Stupid and Small Questions Thread

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Stupid and Small Questions Thread Anonymous Wed Jul 30 14:21:47 2014 No.6672414 [DELETED]

Fire away.

Anonymous Wed Jul 30 14:22:28 2014 No.6672415

I'll start.Does anyone happen to know the name of a Mathematician who noticed that when you add first and the last number of the set and then move by one to the middle from both sides and add and repeat you get the same number every time? Only thing that I remember is that he lived around 16th century.

Medical_Physicist !!ST92PtcX00D Wed Jul 30 14:29:18 2014 No.6672421

>>6672414

Uhm, I'm pretty sure the whole "add up all the numbers from 1...100" question is generally accompanied with a story about Gauss surprising his teacher by doing it elegantly, but someone might have realized the method before him.

>>	Anonymous Wed Jul 30 14:31:25 2014 No.6672424 >>6672415 Carl Friedrich Gauss. Added all the numbers from 1 to 100. 1+99, 2+98, 3+97... etc

>>	Anonymous Wed Jul 30 15:08:23 2014 No.6672469 Why is cum white?

>>	Anonymous Wed Jul 30 15:15:02 2014 No.6672476 >>6672469 *Semen

>>	Anonymous Wed Jul 30 15:19:55 2014 No.6672483 What's /sci/'s career tiers?

Anonymous Wed Jul 30 15:24:18 2014 No.6672492
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I've read that there is a higher concentration of metabolites at the beginning and ending portions of your piss stream. I can't seem to find any articles proving this fact and would love to know if it's factual.

>>	Anonymous Wed Jul 30 15:25:28 2014 No.6672496 >>6672469 Because it reflects all wavelengths on the visible color spectrum.

>>	Medical_Physicist !!ST92PtcX00D Wed Jul 30 15:32:14 2014 No.6672502 >>6672483 God tier: medical physics Shit tier: not medical physics

>>	Anonymous Wed Jul 30 15:53:54 2014 No.6672543 >>6672483 >career tiers That is only shitposting. Those tier lists are just 18 year olds trolling each other about their college majors.

>>	Anonymous Wed Jul 30 18:09:16 2014 No.6672730 what causes us to age?

Anonymous Wed Jul 30 18:09:46 2014 No.6672732
File: 56 KB, 682x362, sequence.png [View same] [iqdb] [saucenao] [google]

Going through a proof that there exists a monotonic subsequence for some sequence sn whose limit is equal to the limit of the supremum of sn.

I follow it until the 'Otherwise..' part; are they claiming that if the number of points of the sequence within epsilon of t is finite, there exists some N such that when n>N, the sequence values begin to decrease and become less than t minus epsilon? Why would that make the supremum of sn less than t minus epsilon, there still exists values we defined previously for n<N that were within epsilon of t.

>>	Anonymous Wed Jul 30 18:16:17 2014 No.6672750 >>6672543 During Galio's time, I recall professors made a tier list themselves for the careers. Philosophy ranked on top.

>>	Anonymous Wed Jul 30 19:05:51 2014 No.6672837 >>6672730 would like to see an answer for this as well

>>	Anonymous Wed Jul 30 19:10:58 2014 No.6672845 >>6672750 Philosophy back then and philosophy now are quite different.

Anonymous Wed Jul 30 19:25:44 2014 No.6672858

>>6672730
Causes us to age? Can you think of anything living that doesn't age?

If you mean age as in time flowing, then you're really asking: why does time flow? Time is nothing but a definition, so no why there.

If you by aging mean chemical processes, the answer is like: why does fruit rot?

>>	Anonymous Wed Jul 30 19:27:01 2014 No.6672861 >>6672730 Our use of oxygen

>>	Anonymous Wed Jul 30 19:27:55 2014 No.6672862 >>6672858 Well why does fruit rot? I'm curious about the chemical processes. I thoughht it was caused by shortening telomeres(?) originally.

>>	Anonymous Wed Jul 30 19:30:02 2014 No.6672866 >>6672861 Could you elaborate? I can't find anything on google

>>	Anonymous Wed Jul 30 19:30:21 2014 No.6672867 >>6672862 No expert, but maybe an irreversible process like burning coal?

Anonymous Wed Jul 30 19:31:49 2014 No.6672870

>>6672862
First the purpose of a fruit is to spread seed. It is not meant to endure very long. It just needs to last long enough attract fruit eaters and if they do not show it needs to get its seeds out to grow. There are actually hormones, especially the gas ethylene the fruit itself emits to promote fruit ripening then rotting. Ethylene also attracts insects like fruit flies. This is why fruit ripens faster in a bag, it concentrates the gas.

As fruit ripens the stored starch is broken down into simple sugars making it sweeter. Also the structural elements that give it shape are softened. Chlorophyll is stopped and other pigments appear so the fruit attains a ripe color. These other pigments also are responsible for producing part of the scent in some fruit. This is why ripe fruit is easier to eat and much more desirable. This ripening is actually breaking the tissues down making it easier for the yeast and bacteria to begin eating the fruit and release the seed.

>>	Anonymous Wed Jul 30 19:32:54 2014 No.6672874 >>6672866 http://en.wikipedia.org/wiki/Free-radical_theory_of_aging

>>	Anonymous Wed Jul 30 19:37:39 2014 No.6672879 >>6672502 Glad to see objectivity is an integral part of medical physics

>>	Anonymous Wed Jul 30 19:39:06 2014 No.6672885 How do I swindle another human being to debasing themselves by being attracted to me?

>>	Anonymous Wed Jul 30 19:40:48 2014 No.6672887 What are the practical applications for quantum mechanics?

>>	Anonymous Wed Jul 30 19:44:08 2014 No.6672890 >>6672874 >>6672870 Thanks anons

>>	Anonymous Wed Jul 30 19:46:39 2014 No.6672895 >>6672887 Lasers

>>	Anonymous Wed Jul 30 19:48:22 2014 No.6672900 >>6672887 Computers.

>>	Anonymous Wed Jul 30 19:51:10 2014 No.6672904 >>6672887 http://www.discovery.com/tv-shows/curiosity/topics/10-real-world-applications-of-quantum-mechanics.htm

Anonymous Wed Jul 30 19:59:14 2014 No.6672920

>>6672414
I'm doing Calc I problems related to work needed to empty a trough.

One of the problems has a trough and a 2m pipe at the top.

Why is it correct to just add this length to the distance part of the function I am integrating? Shouldn't the diameter of the pipe, its position, where the pump is located, or all of the above increase the amount of work required to empty the trough?

Anonymous Wed Jul 30 20:01:20 2014 No.6672925

>>6672887
Well seeing as everything in the universe is made of particles and atoms, and quantum mechanics is what (somewhat) explains how things work at that level. Think of it like Newtons Laws for our scale of things, but at the quantum level there is a lot of weird shit happening. A lot of the really big practical uses will come in the future when we learn more about QM, such as quantum computers.

>>	Anonymous Wed Jul 30 20:07:41 2014 No.6672935 Why does everyone misinterpret Schrodinger's cat? It was meant to show the problems with the Copenhagen interpretation, not be a basic introduction into QM.

>>	Anonymous Wed Jul 30 20:13:54 2014 No.6672943 >>6672920 Diameter doesn't change the total amount of work done, just how quickly the work is done, which would be Power.

Anonymous Wed Jul 30 20:16:07 2014 No.6672949

Unless I'm wrong, if I throw a ball into the air faster than the earth's escape velocity, the ball will travel away from the earth forever and never come back (assuming no air resistance, and it doesn't hit anything and all that). My question is how can this be? Even if the ball is far away from the earth, doesn't the earth's gravity still affect the ball if very slightly? If given eternity, why won't the ball stop, and start to come back?

>>	Anonymous Wed Jul 30 20:20:55 2014 No.6672961 >>6672935 >I am the ONLY one interpreting Schrödingers cat correctly

>>	Anonymous Wed Jul 30 20:21:04 2014 No.6672962 >>6672949 I'mma hijack this one because it prompted something I thought of earlier. Assuming the same situation, does the ball have to maintain escape velocity or just achieve it momentarily to escape the gravitational pull?

>>	Anonymous Wed Jul 30 20:22:29 2014 No.6672964 >>6672949 Because the kinetic energy you gave the ball is greater than the energy of the gravitational field.

>>	Anonymous Wed Jul 30 20:23:03 2014 No.6672967 >>6672949 Also, I think this is what inertia is all about, if no other force acts on an object, it will stay on its course and maintain its velocity. As such, I just answered my own question as well.>>6672962 The end.

>>	Anonymous Wed Jul 30 20:23:56 2014 No.6672968 Why are logarithms used in mathematics? I've been told that they were created a long time ago to aid in making big calculations. We have computers now, so why bother? There is probably an obvious reason that I am ignorant of.

>>	Anonymous Wed Jul 30 20:29:35 2014 No.6672978 >>6672968 Logarithmic and exponential relationships are ubiquitous in natural and physical phenomena. They are also very useful functions in mathematics, physics, statistics, and probability

Anonymous Wed Jul 30 20:30:36 2014 No.6672981

>>6672870
How did plants evolve to the point of growing fruit to help spread there seed? Like how did they know to make the fruit have nutritional value to other organisms, knowing that this will spread their seeds efficiently?

Kind of a dumb ass question, but I'm suddenly curious after reading your post.

>>	Anonymous Wed Jul 30 20:32:07 2014 No.6672985 >>6672978 That doesn't explain anything. Why not use exponential functions only?

>>	Anonymous Wed Jul 30 20:34:34 2014 No.6672990 >>6672968 well, in my field we use them to make linear representations of exponential functions this cn be helpfull when calculating microbial protein production and enzyme activity etc

Anonymous Wed Jul 30 20:34:51 2014 No.6672991

>>6672949
The Earth's gravitational pull gets weaker the farther away the ball is from Earth. So when you throw it at escape velocity, the Earth will slow the ball down, but the ball constantly moves away and the gravitational force gets weaker and weaker. So the Earth will never be able to slow the ball down enough to stop it completely.

>>	Anonymous Wed Jul 30 20:36:33 2014 No.6672995 >>6672985 The logarithm is the inverse of the exponential. Half life is a good example.

>>	Anonymous Wed Jul 30 20:41:46 2014 No.6672999 >>6672981 Could just be natural selection

>>	Anonymous Wed Jul 30 20:43:39 2014 No.6673006 >>6672492 it is, just lok for some articles on urin tests, most metabolite determinations have to be measured from mid stream urine to rule out falsely elevated values

>>	Anonymous Wed Jul 30 20:44:34 2014 No.6673010 >>6672981 >organism is already eating the plant anyway >one of those plants happens to have a mutation that makes it produce tumors around it's seeds >organisms eat dem delicious mutant tumors with seeds in them bam fruit

>>	Anonymous Wed Jul 30 20:45:53 2014 No.6673015 >>6672961 http://en.wikipedia.org/wiki/Schrödinger's_cat#Origin_and_motivation

Anonymous Wed Jul 30 20:47:16 2014 No.6673017

>>6672730
the way our dna is replicated during cell division is inefficient. over time nucleotides (data) are lost in the splitting process and random compounds are added to fill the gap. this resulta in inferior cell quality and eventually non functioning cells.

incidentally, cells that dont have this data loss function become cancerous

>>	Anonymous Wed Jul 30 20:50:46 2014 No.6673025 >>6672968 http://zetatrek.tumblr.com/post/93313594640/telescopes-logarithms-computers-a-400-year-journey They still help. Plus, they're solving a^b=x for b, what's there not to love

>>	Anonymous Wed Jul 30 20:53:27 2014 No.6673032 >>6673010 Fruit also serves as a nutrient bank for the seed(s) inside. Other animals eat this and then widely distribute the seed along with a brown fertilizer. It's easy to see how both of these would give a strong reproductive advantage.

>>	Anonymous Wed Jul 30 20:57:17 2014 No.6673044 >>6673032 Didn't even think about that. It's a pretty clever idea too. I really love evolution. Usually you can come up with several elegant ways to explain a certain aspect.

Anonymous Wed Jul 30 21:10:44 2014 No.6673063

>>6672964
Okay, but I still don't get why the earth can't stop the ball if given a sufficient amount of time.

>>6672991
Same thing kinda.. If the earth is always pulling on the ball no matter how far away the ball is (even if very slightly) shouldn't it eventually stop it after an unfathomable amount of time? Kinda like how the harmonic series diverges even though the numbers get infinitesimally small.

Anonymous Wed Jul 30 21:12:55 2014 No.6673065

>>6672981
>Like how did they know to make the fruit have nutritional value to other organisms, knowing that this will spread their seeds efficiently?

Evolution is completely 'blind', organisms mutate randomly, the majority of these mutations are pointless or harmful. It's just that some mutations positively affect reproduction, so that we end up with more organisms that had good mutations, while the ones with negative mutations don't reproduce and disappear. There is no intention or design behind it all, just chance mutations and the environment killing off the shit ones.

Anonymous Wed Jul 30 21:14:56 2014 No.6673069

>>6673063
>Okay, but I still don't get why the earth can't stop the ball if given a sufficient amount of time

It just depends on the angle. If you throw straight up it will come back unless you threw with infinite power.
If you throw it at an angle it might enter a stable orbit around earth though and while it might not ever touch the earth again in your fictional scenario it still didn't escape it's gravity

Anonymous Wed Jul 30 21:18:15 2014 No.6673076

>>6673065
Fun fact: evolution only really cares about animals before they reproduce, for obvious reasons. So that's why there are things like old elephants starving to death when their teeth rot out: evolution doesn't care about the elderly. It's purely a reproductive mechanism.

Anonymous Wed Jul 30 21:18:55 2014 No.6673078

>>6673063
Because the pull of the Earth's gravity gets smaller at a quicker rate than the ball slows down.

Imagine the ball slows down 10% every mile or so, it would never actually stop. In reality the % it slowed down each mile would get less and less, until that was infinitely small.

Anonymous Wed Jul 30 21:25:16 2014 No.6673088

>>6673076
Fun actual facts:

1) Evolution doesn't 'care' about anything.
2) Evolution will still act on the part of the population past breeding age, if those individuals have an impact on the breeding population. Case in point: species which have grandmother care, like humans, chimps, and elephants.

>>	Anonymous Wed Jul 30 21:27:02 2014 No.6673092 >>6672985 Yeah! And why use division?! We should just use multiplication for everything!

>>	Anonymous Wed Jul 30 21:30:38 2014 No.6673099 >>6673078 This makes sense, thank you. I never thought of itaking a percentage per interval, but instead as a static amount per interval.

>>	Anonymous Wed Jul 30 21:52:21 2014 No.6673119 How do any attractive forces work? It just doesn't seem to make intuitive sense unless there is some sort of universal pressure pushing everything away from everything else, and instances of attraction mitigate it.

>>	Anonymous Wed Jul 30 21:56:07 2014 No.6673128 File: 6 KB, 300x200, 239823984289jsdl3.jpg [View same] [iqdb] [saucenao] [google] anyone have the neil degrasse tyson where its something about seeing further than the others because of that 420 dank shit?

>>	Anonymous Wed Jul 30 22:06:15 2014 No.6673143 >>6673128 no >>>/r/

>>	Anonymous Wed Jul 30 22:09:28 2014 No.6673145 Is there a math and/or physics equivalent of slashdot?

>>	Anonymous Wed Jul 30 22:45:23 2014 No.6673194 Could someone explain to me what plasma is?

>>	Anonymous Wed Jul 30 22:57:20 2014 No.6673201 >>6673194 Plasma is to gas what gas is to water

Anonymous Wed Jul 30 23:20:34 2014 No.6673221

Helping a friend with reviewing for a calc test. Stupid question incoming.

Find the inverse of y=x^3+4X.

So, replace y with x's, blah blah.

x=y^3+4y

So, my natural inclination is to pull out the y

x=y(y^2+4)

Issue is that gives imaginary roots, and he's not covered that yet. Am I just too drunk to do basic algebra now? :c

>>	Anonymous Wed Jul 30 23:31:33 2014 No.6673239 >>6673128 Not NDT. It was Newton. https://en.m.wikipedia.org/wiki/Standing_on_the_shoulders_of_giants

Anonymous Thu Jul 31 00:01:53 2014 No.6673286

>>6673221
That might actually be a stupid question.
Meaning it might not have an inverse in terms of standard algebraic functions.
I've been working on it but I'm not coming up with anything.
Which isn't to say it's impossible but I like to think I'm capable of an algebra problem from a Calc 1 class...

>>	Anonymous Thu Jul 31 00:35:36 2014 No.6673308 >>6673221 There is no inverse. Horizontal line test.

>>	Not him Thu Jul 31 00:41:07 2014 No.6673316 >>6673221 I've got nothing. What book and section are you using? >>6673286 Scary right? http://www.wolframalpha.com/input/?i=inverse+of+x%5E3%2Bx >>6673308 wrong function is one-to-one. next time try

>>	Not him Thu Jul 31 00:48:43 2014 No.6673323 >>6673316 > next time try uhh I feel like there was more to this thought, but I don't remember what.

>>	Anonymous Thu Jul 31 00:49:24 2014 No.6673324 >>6673308 Derivative is <span class="math">y' = 3x^2 + 4[/spoiler] Which is always positive, so the function is always increasing and therefore passes the horizontal line test.

Anonymous Thu Jul 31 00:51:09 2014 No.6673326
File: 121 KB, 468x1049, SMBC Shame.gif [View same] [iqdb] [saucenao] [google]

Is there a psychological term that describes the occurrence displayed in the comic?

Like a frequent reflection on past memories that leads to constant insecurity or shame?

If there is, is it a fairly common thing? Do most people frequently struggle with it?

>>	Anonymous Thu Jul 31 00:52:50 2014 No.6673327 >>6673326 I struggle with it. But I finally understand I'm not normal.

>>	Anonymous Thu Jul 31 01:56:31 2014 No.6673392 >>6673326 It's a symptom of anxiety but it's only one of a myriad of other symptoms and a fairly common one at that.The counter to it though is to realize that if everyone is busy thinking about their past mistakes no one is thinking about yours.

>>	Anonymous Thu Jul 31 02:04:14 2014 No.6673398 >>6672414 Can anybody explain particle pair production at the quantum level?

>>	Anonymous Thu Jul 31 02:05:53 2014 No.6673401 >>6673398 *using quantum mechanics

>>	Anonymous Thu Jul 31 02:13:47 2014 No.6673413 If we ever develop the time machine who'd build it?

>>	Anonymous Thu Jul 31 02:55:13 2014 No.6673450 >>6673413 an engineer.

>>	Anonymous Thu Jul 31 02:57:45 2014 No.6673451 >>6673398 conserve momentum conserve energy conserve quantum numbers when these 3 are obeyed, eg when a photon hits some nuclei, you can basically create any particle you want.

>>	Anonymous Thu Jul 31 04:40:34 2014 No.6673498 >p2 + X + -49 = Y So if X = OP does that mean that Y = faggot?

Anonymous Thu Jul 31 07:48:24 2014 No.6673609

Am I stupid? Task was to write an equation that represents the relationship between a number of bacteria (a) and the duration in minutes (t), assuming they double in number every 4 minutes

2*a^(t/4)

If 0 <= x < 1 then a^x = 1. So after 1 minute, there are 2*1 = 2 bacteria, even when they are supposed to double three minutes later. Help a noob!

>>	Anonymous Thu Jul 31 07:51:53 2014 No.6673613 If the function f(x) = x^2 was actually the absolute value of some other function, what would said function be?

Anonymous Thu Jul 31 07:59:22 2014 No.6673621

>>6673609
>2*a^(t/4)

This is wrong. If the number a doubles each t minutes, that means:

a * 2^t

Assume you have an initial number of 1 and 5 minutes, this makes:

1 * 2^5 = 1 * 2 * 2 * 2 * 2 * 2 = 32

Which makes sense, because the initial number is doubled t times. What you did was:

2 * 1^5 = 2 * 1 * 1 * 1 * 1 * 1 = 2

>>	Anonymous Thu Jul 31 08:17:15 2014 No.6673637 How do I convert my polarimetric values into a proper table so I can make a conclusion out of it? I measured a rotation of D-(+) Glucose (0.2M) , and my outcome was 16.9. Now how do I calc my specific rotation? (I'm such a noob)

Anonymous Thu Jul 31 08:56:34 2014 No.6673671

>>6672732
e (epsilon) and N_0 are fixed

For n > N_0
you have s_n < t + e (*)

but s_n could behave "oddly", for instance it could decrease. We want to assure that's not the case : that is to say (except for some possible values), s_n stay close to t. => we want to prove the set A of (1) is infinite.

By contradiction, suppose A is finite. The set of s_n being infinite since (s_n) is a sequence indexed by N, it means that an infinity of them or outside of A, either >t+e, either <t-e.

First case is impossible because of (*), so it means an infinite number of s_n are such that s_n<t-e.
We can define the indexing variable N_1 from which it happens.

but if all the s_n with n>N_1 are such that s_n<t-e, their sup verifies sup < OR = t-e (standard behavior of supremum).

This inequality stands for e>0, so the limit (which exists by hypo) must be <t (it can't be t : write down the definition of the limit for sup s_n with an e' -> you can find an e which force the sup s_n to be outside (t-e',t+e')).

And you have your contradiction.

--
>>6672732
>Why would that make the supremum of sn less than t minus epsilon
it makes it for n big enough! Don't forget we're interested by the limit of sup, so we don't care of the first values.
The object studied here is (sup{s_n}), indexed by n. When n gets bigger, the first "big values" of s_n vanish

>>	Anonymous Thu Jul 31 08:59:00 2014 No.6673674 >>6673613 ? x->x^2 can be seen as the absolute value of itself, since x^2>=0. Rephrase your question, maybe

>>	Anonymous Thu Jul 31 09:02:09 2014 No.6673676 >>6673613 x2 or -x2 ?

>>	Anonymous Thu Jul 31 09:32:57 2014 No.6673698 why do we feel a force outwards when we drive a car in a bend if the centripetal force is inwards? if there are two forces, one inwards and other outwards, shouldn't they cancel each other?

>>	Anonymous Thu Jul 31 09:42:09 2014 No.6673703 File: 12 KB, 410x122, problem.jpg [View same] [iqdb] [saucenao] [google] >>6672414 Please provide a solution to this. I'm fucking retarded and cant solve it.

not going to grad school Thu Jul 31 10:02:01 2014 No.6673723

>>6672414
Atmospheric electricity. It's my understanding that the earth's atmosphere is positively charged, and that as you move away from the ground this charge increases by about 30 volts per foot moving away from the gradient. This increases to about 300,000 volts around 40 km above the surface. (i know these numbers aren't consistent, and this is probably my misunderstanding.) Why can't we just build giant towers to collapse this potential, and collect the energy to power stuff, or is this just exactly what those graphene ambient energy collecters do I'm the first place.

I'm not talking about the ionosphere.

>>	Anonymous Thu Jul 31 10:05:28 2014 No.6673728 >>6673698 Forces are always in equal and opposite pairs, but they don't operate on the same thing. force of road on car, inward = force of car on road, outward force of car on you, inward = force of you on car, outward

>>	Anonymous Thu Jul 31 10:07:44 2014 No.6673729 >>6673723 Because air is a very poor conductor, which is how that potential is able to exist in the first place. You need a much stronger electric field to collapse it, which does happen sometimes and is called lightning.

Anonymous Thu Jul 31 10:13:27 2014 No.6673740

I'm a musician who has always been interested in the sciences, philosophy, politics, etc. I want to greatly increase my literacy in all of these fields. I've began reading phil/pol books and now I come to you for your recommendations on how I can improve my scientific literacy without having to get another degree/changing major. Pls help. Thanks, greatly appreciate it.

>>	not going to grad school Thu Jul 31 10:18:35 2014 No.6673748 >>6673729 o duh, you can't draw the field even if a conductor is up there. Ty stupid questions anon

>>	Anonymous Thu Jul 31 10:29:59 2014 No.6673773 >>6672414 If I was invisible, would I cast a shadow?

>>	Anonymous Thu Jul 31 10:31:22 2014 No.6673775 >>6673773 I would imagine not, seeing as the light is either being bent around you and actually going right through you. Depends on your method of invisibility. I could be totally wrong though.

>>	Anonymous Thu Jul 31 10:32:23 2014 No.6673778 >>6673775 or actually going right through you*

>>	Anonymous Thu Jul 31 10:37:31 2014 No.6673783 Is time quantized?

>>	Anonymous Thu Jul 31 10:38:54 2014 No.6673784 >>6673775 Yeah, makes sense.

>>	Anonymous Thu Jul 31 10:43:15 2014 No.6673789 >>6673703 google 2nd order linear diff equation.

Anonymous Thu Jul 31 10:47:28 2014 No.6673799

Will polylinear function be always convex, if all its coefficients are non-negative? I know that if we fix all arguments except one, we'll get linear function that always be convex. So we can do for every arguments. Does it mean that polylnear function be convex?

>>	Anonymous Thu Jul 31 10:49:48 2014 No.6673803 >>6673789 I've already did that man. I cant factor it. At all. So I dont know if it has 2 real roots or 2 complex roots or 1 root.

>>	Anonymous Thu Jul 31 10:51:10 2014 No.6673804 >>6673803 depends on the sign of alpha^2-4w^2

>>	Anonymous Thu Jul 31 10:57:24 2014 No.6673811 >>6673804 We're not given any information about alpha or w^2, so it's pretty much impossible to work out if the discriminant is >0, <0 or =0. What can you do in this situation?

Anonymous Thu Jul 31 11:02:51 2014 No.6673817

>>6673811
keep it all in complex numbers.

yfor a general equation like
<div class="math">
ay'' + by' + cy = 0
</div>

you end up with
<div class="math">
f(x) = e^{ux}(A\cos(vx) + B\sin(vx))\,
</div>
or
<div class="math">
f(x) = q e^{ux}\cos(vx+r)\,
</div>

where A,B,q,r are defined to satisfy initial conditions

and u,v are the real,imaginary parts of the roots of <div class="math">a\lambda^2 + b\lambda + c = 0</div>

>>	Anonymous Thu Jul 31 11:06:33 2014 No.6673825 >>6673783 That is unknown.

>>	Anonymous Thu Jul 31 11:11:43 2014 No.6673829 >>6673728 thank you

>>	Anonymous Thu Jul 31 11:51:14 2014 No.6673871 >>6673450 What kind?

>>	Anonymous Thu Jul 31 11:52:53 2014 No.6673875 >>6673698 Inertia

>>	Anonymous Thu Jul 31 12:22:42 2014 No.6673899 Why do I have the urge to hurt small animals? I would never do it.

>>	Anonymous Thu Jul 31 12:24:02 2014 No.6673900 Is there a way to determine an angle with the trig ratios without just memorizing special triangles?

>>	Anonymous Thu Jul 31 12:42:00 2014 No.6673923 >>6672885 Read The Game.

>>	Anonymous Thu Jul 31 12:54:01 2014 No.6673949 Am I right in saying that the kinetic energy of a moving object is the same as the work done to get it up to that velocity (assuming 100% efficiency in whatever the propulsion system is)

>>	not going to grad school Thu Jul 31 13:20:57 2014 No.6673986 >>6673900 what like this? http://www.sparknotes.com/testprep/books/sat2/math2c/chapter9section9.rhtml on a phone or you'd get a more in depth answer

Anonymous Thu Jul 31 13:24:01 2014 No.6673990

Is it presumed that time existed before the big bang?

If time did not exist before the big bang, then wouldn't everything be frozen, preventing the big bang from happening? Whatever laws that set off the big bang wouldn't be able to move forward because time wouldn't be there as a medium to move through

I'm really new at this science stuff so please forgive how dumb this is

>>	not going to grad school Thu Jul 31 13:25:14 2014 No.6673992 >>6673986 or do you mean like what is sine(48)

>>	Anonymous Thu Jul 31 13:28:26 2014 No.6673997 >>6673949 Yes.

>>	Anonymous Thu Jul 31 13:28:45 2014 No.6673998 >>6673992 I mean finding the angle when you have a ratio of the sides of a right triangle without relying on special triangle properties.

>>	Anonymous Thu Jul 31 13:32:28 2014 No.6674002 >>6673997 Taylor expansion to get approximate. trig identities and special triangles to get exact

>>	Anonymous Thu Jul 31 13:46:24 2014 No.6674018 How can something in history be proven?

Anonymous Thu Jul 31 13:46:39 2014 No.6674019

>>6673613
There are infinite other functions it could be
For example,
the piecewise discontinuous function
f(x) = x^2 if x is rational, -x^2 otherwise

Really for any set A that is a subset of the reals,
f(x) = x^2 if x is in A, -x^2 if x is not in A
would have |f(x)| = x^2.

If you want a non-piecewise function I think these are your only options >>6673676.

>>	Anonymous Thu Jul 31 13:51:47 2014 No.6674028 >>6674018 How can something in the present be proven?

>>	Anonymous Thu Jul 31 13:54:48 2014 No.6674031 >>6674028 Touché.

not going to grad school Thu Jul 31 14:16:01 2014 No.6674063

>>6673998
Sin cosine and tangent are that ratio. So no. Sine is opposite/hypotenuse, and there is a specific angle associated with each ratio. That is to say Sine is a function between the two. I'm reasonably certain that the sine function was estimated by taking triangles and measuring them, because you usually use Taylor polynomials and just repeat the values when writing a sine function for computers. So to answer your question I'm pretty sure you just have to memorize them.

But I stopped taking math at the 400 level so there might be some esoteric PhD level math that can do what you want, in which case you wouldn't be able to do it. But rest assured, if I am wrong, some one who probably ignored your question earlier will be by to call me a noob and answer it for you.

I take it you're memorizing the unit circle?

>>	Anonymous Thu Jul 31 14:47:44 2014 No.6674091 >>6674018 It's not like somebody Alexander The Great fake his whole conquest in order to mislead people two thousand of years in to future.

>>	Anonymous Thu Jul 31 14:56:53 2014 No.6674101 >>6672469 Actually the seminal fluid is clear when it's inside your body but when it touches the air it oxidizes and turn opaque. The white clouds however are simply just. Highly concentrated regions of sperm and supporting material.

>>	Anonymous Thu Jul 31 14:59:27 2014 No.6674107 A question for you pro/sci/uttos, where do you stand on non-hard science-fiction?

>>	Anonymous Thu Jul 31 15:12:28 2014 No.6674127 So get this, space and time are relative to each other according to Einstein's theory right? Well, if space is expanding, does time have the ability to expand as well?

Anonymous Thu Jul 31 15:19:07 2014 No.6674136

>>6674063
I took a year off from school and I'm relearning everything upto calculus so I don't go into college with no memory of how to do basic shit. Also my school never took us past precal due to the incompetent teacher we had. We spent the entire year on the trig review portion of the precal class and didn't even finish it. Thanks America.

>>	Anonymous Thu Jul 31 15:45:39 2014 No.6674178 >>6673671 Thanks a bunch man, I understand it now.

>>	not going to grad school Thu Jul 31 16:17:35 2014 No.6674232 File: 28 KB, 500x461, 9096eb41-7b8a-4bc7-85be-a51d38d30.png [View same] [iqdb] [saucenao] [google] >>6674136

>>	Anonymous Thu Jul 31 16:21:10 2014 No.6674241 >>6674091 You think they would not?

Anonymous Thu Jul 31 16:21:52 2014 No.6674243

>>6674127

Space and time are not separable like that. When we say space is expanding, obviously we mean space is more expanded now than it was previously, i.e. time is already involved. Another way of saying the exact same thing is that the 4D object we call the universe is narrower in the "past" direction.

>>	Anonymous Thu Jul 31 16:28:37 2014 No.6674261 >>6672496 I shot my spectrum all over OP's face

>>	Anonymous Thu Jul 31 16:41:52 2014 No.6674298 Any math majors here? What's the hardest undergraduate course I can expect to take?

Anonymous Thu Jul 31 17:08:16 2014 No.6674367
File: 68 KB, 488x595, subsequence.png [View same] [iqdb] [saucenao] [google]

So I'm proving that a sequence with infinite values within epsilon of t has a subsequence that converges to t, and at this point the proof they're constructing the subsequence by induction, but if a subsequence is supposed to be infinite, and we're constructing it piece by piece inductively, how is that reasonable enough to prove something? Pic related.

(1) in the picture references the statement that the set { n in N such that t - epsilon < s_n < t } is infinite.

>>	Anonymous Thu Jul 31 17:13:19 2014 No.6674378 File: 495 KB, 1280x1024, JesusfuckIvan.jpg [View same] [iqdb] [saucenao] [google] >>6672414 If I were to smear queen Bee pheromones on my dick, could I fuck a bee hive? Or at least jerk off into it?

>>	Anonymous Thu Jul 31 17:28:38 2014 No.6674407 >>6674298 I've been told Real analysis

>>	Anonymous Thu Jul 31 17:29:49 2014 No.6674409 Does anyone know a site that lists the greek alphabet and its letters meaning in maths?

>>	Anonymous Thu Jul 31 17:33:11 2014 No.6674422 >>6674409 http://en.wikipedia.org/wiki/Greek_letters_used_in_mathematics,_science,_and_engineering

>>	Anonymous Thu Jul 31 17:35:09 2014 No.6674425 >>6674422 Crap, forgot about wikipedia. Thanks anon

Anonymous Thu Jul 31 17:38:40 2014 No.6674432

>>6673871
It'd be a collaboration of multiple disciplines and definitely wouldn't be restricted to only engineers. There'd be involvement from all STEM related careers.

Of course, this is all hypothetical, so for all we know some redneck in the woods could do it as well.

>>	Anonymous Thu Jul 31 17:40:37 2014 No.6674439 >>6673899 intrusive thoughts

>>	Same Hobbies Guy Thu Jul 31 18:12:06 2014 No.6674504 >>6673017 sooooo, if i could potentially create a process which is efficient, our cells would not alter with time?

>>	Anonymous Thu Jul 31 18:12:21 2014 No.6674506 >>6672424 Doesn't everyone do this when they're adding up consecutive numbers when young?

>>	Anonymous Thu Jul 31 18:16:42 2014 No.6674518 >>6673392 But I think of other people's mistakes sometimes.

>>	Anonymous Thu Jul 31 18:18:31 2014 No.6674523 What is a good way to learn about differential equations at an intermediate level? I've had some analysis and basic ODE practice (and a good amount of algebra), but I want to learn more about things like harmonic analysis and Lie groups.

Anonymous Thu Jul 31 18:49:49 2014 No.6674600

i've started study physics but nothing so far really explains why gravity exists, if your a bit further along, is my current thinking about right - is it because matter occupies space, that piece of the universe has to exist (as opposed to before the big bang) does matter emit gravity to balance the creation of this space, by the emission of gravity allowing space to exist, thus to create either/and a vacuum or attract other matter, as means of conservation of euclidean space?

Anonymous Thu Jul 31 19:34:56 2014 No.6674681

<span class="math">\displaystyle \lim_{n \rightarrow \infty} \frac{n^p}{e^n}, \;\;\; p>0[/spoiler]

I'm a general math tutor here and I ran into the problem of trying to explain this problem to some of my students. The limit is zero and I honestly could not come up with an acceptable explanation for explaining why the limit equaled zero. My explanation is that the denominator is going to increase much much MUCH faster than the number as <span class="math">n \rightarrow \infty[/spoiler], but because these calculus students have never seen something like proof by induction or something of the sort, I didn't quite know a good method to explain it otherwise.

Apparently, the solution online that I found was that for <span class="math">\displaystyle \lim_{n \rightarrow \infty} \frac{n^p}{e^n}, \;\;\; p>0[/spoiler], applying L'Hôpital's rule <span class="math">p[/spoiler] times gives us

<span class="math">\displaystyle \lim_{n \rightarrow \infty} \frac{n^p}{e^n} = \lim_{n \rightarrow \infty} \frac{ pn^{p-1} }{e^n} = \underset{p - 3 \, times}{\cdots} = \lim_{n \rightarrow \infty} \frac{p^pn}{e^n} = \lim_{n \rightarrow \infty} \frac{p^p}{e^n} = 0[/spoiler]

This alternative method makes so much sense, but I would like to know if my explanation to my students held any valid ground. Is it flawed? I didn't think about looking online for the answer at the time, but eh. What's done is done...

>>	Anonymous Thu Jul 31 19:40:34 2014 No.6674686 >>6674681 Please excuse that horrible transgression. That shouldn't be <span class="math"> p^p [/spoiler]. That should be <span class="math"> p! [/spoiler] in the numerator. I haven't slept in 20 hours and got lost in the TeX.

Anonymous Thu Jul 31 19:40:47 2014 No.6674688

>>6672730
telemeres get shorter over time.
Telemeres are like the neat little tubes at the end of shoelaces, they protect the ends of DNA from damage.
Oxidation kills the fuck out of telemeres until they die, and then the DNA starts eroding too, until you get DNA that just fails to work properly.

Anonymous Thu Jul 31 19:50:20 2014 No.6674702 [DELETED]

>>6674681
elementary proof using <span class="math">exp[/spoiler]'s definition:
<span class="math">\lim_{n\to\infty}\frac{n^p}{e^n}[/spoiler]
<span class="math">=\lim\frac{n^p}{\sum_{k=0}^\infty\frac{n^k}{k!}}[/spoiler]
<span class="math">\geq \lim\frac{n^p}{\frac{n^{p+1}}{(p+1)!}}[/spoiler]
<span class="math">=\lim\frac{(p+1)!}{n}[/spoiler]
<span class="math">=0[/spoiler].

>>	Anonymous Thu Jul 31 19:51:45 2014 No.6674705 >>6674702 fuck this shit. broken line is <span class="math">=\lim\frac{n^p}{\sum_{k=0}^\infty\frac{n^k}{k!}}[/spoiler]

>>	Anonymous Thu Jul 31 19:52:47 2014 No.6674707 >>6674705 While this statement is totally true, what I meant is <span class="math">=\lim \frac{n^p}{\sum_{k=0}^\infty \frac{n^k}{k!}}[/spoiler]

Anonymous Thu Jul 31 19:54:09 2014 No.6674711

>>6673194
Gas that's had its electrons stripped from its nuclei.

>>6673698
When an elevator goes up (accelerates upwards) you feel a force "downwards" where you feel heavier. When an elevator drops, you feel a little weightless. This is because the elevator (and your car) are non-inertial frames. Your body's inertia is resisting acceleration, so when your frame accelerates, it has to accelerate your body too. To your body, which assumes your frame isn't moving, it feels like a magical force is pushing you the other direction.

>>6673740
Audit classes without taking them for a grade. Just show up and listen to lectures and have your mind blown.

>>6673990
The idea is that time began at the big bang and did not exist beforehand, but no one truly knows what happened before the big bang because we can't probe that yet.

>>6674127
Yes. Time dilation. But as another anon stated, it's a different sort of expansion.

>>6674298
Real analysis, but it isn't that bad if you take your time and try to get an intuition for what's going on. I took the honors version and got my ass handed to me, only because everyone else in the class was way better at math.

>>6674681
Yes, your explanation is fine. Another way of thinking about it is that if you increase n by one, the top part only gets bigger by ((n+1)/n)^p and the bottom part gets bigger by a factor of e. At large n, (n+1)/n ^ p gets very close to 1, and so eventually it starts acting like you're just multiplying by 1/e every time you make n bigger.

1/e^-infinity = 0.

Conceptually, ignoring L'Hopital and rigor.

>>	Anonymous Thu Jul 31 19:58:56 2014 No.6674718 >>6674681 <div class="math">\lim_{n\to\infty}\frac{n^p}{\mathrm e^n} = \lim_{n\to\infty}\frac{n^p}{\sum_{k=0}^\infty \frac{n^k}{k!}} = \lim_{n\to\infty} \frac{n^p}{\frac{n^{p+1}}{(p+1)!}} = \lim_{n\to\infty}\frac{(p+1)!}{n} = 0</div>

>>	Anonymous Thu Jul 31 19:59:58 2014 No.6674721 >>6674718 The <span class="math">=[/spoiler] in the middle should be a <span class="math">\leq[/spoiler] for clarity...

>>	Anonymous Thu Jul 31 20:17:23 2014 No.6674738 >>6674681 Like >>6674711 said, you can use d'Alembert's ratio test.

Anonymous Thu Jul 31 20:33:59 2014 No.6674757
File: 888 KB, 360x270, Poincare6.gif [View same] [iqdb] [saucenao] [google]

Assume a particle in a 1D potential. The phase space is then 2D. Now add a time-dependent and periodic function to that potential. What dimension is the phase space then? I'd think that you would need another dimension in your phase space to prevent phase space trajectories from crossing. Pic related, they are the Poincaré sections of the Duffing oscillator.

Anonymous Thu Jul 31 21:13:31 2014 No.6674788

Does anyone here study Aerospace Engineering? I want to get a degree in this subject but I am a little worried if I can handle the math and the general know how. Right now I'm about to start my freshman year in college and will be doing pre-engineering.

>>	Anonymous Thu Jul 31 21:14:55 2014 No.6674790 >>6674788 Sure.

>>	Anonymous Thu Jul 31 21:16:09 2014 No.6674793 >>6672496 That's the same as saying "because it just is". :/

>>	Anonymous Thu Jul 31 21:23:21 2014 No.6674800 >>6674790 How is it? What are some of the maths involved with aerospace engineering? Do you get to design and test vehicles? Also how much studying do you do?

Anonymous Thu Jul 31 21:28:24 2014 No.6674805

>>6674800
mmkay first. I did ME for BS, but my first year of grad school the degree is called ME and AE because they are so similar.
> How is it?
I liked.
> What are some of the maths involved with aerospace engineering?
The biggest difference is the numerical PDEs.
And there's some fun triple integrals in fluids.
besides that there's some complex analysis in controls, the normal calc cycle, diff eq and lin alg.
> Do you get to design
yes. at my school you either choose to take two courses in aircraft design or spaceship design.
> and test vehicles?
I did, but only as part of my intro to profession class. We built model rockets that were suppose to go to as close to 100 m as possible.
> Also how much studying do you do?
very little compared to most people

Anonymous Thu Jul 31 21:28:26 2014 No.6674806

Who's ready for the stupidest of stupid questions?

I don't understand what pressure is. Like, I get the formula, P=F/A. Pressure is the force on something per its area, but how do knives work? Knives work by maximizing pressure by minimizing area. There's a high force per unit of area, but there's still a given amount of force acting through the knife. P may equal something really big/1, but the area is less than one.

I'm just stupid.

>>	Anonymous Thu Jul 31 21:30:25 2014 No.6674807 >>6674806 P = 1/a small area which is similar to really big/1

>>	Anonymous Thu Jul 31 21:32:11 2014 No.6674811 >>6674807 I get that, but what IS pressure? I'm having difficulty explaining what I mean. I'm so thick.

Anonymous Thu Jul 31 21:32:19 2014 No.6674812

>>6674806
There is a given amount of force. Let's call it 1.

If your area is small, you can get large pressure.

Let's try it numerically.
Area 0.5. Pressure 1/0.5 = 2.
Area 0.1. Pressure 1/0.1 = 10.
Area 10^-4. Pressure 10^4.
As your area gets closer and closer to 0, pressure will get bigger and bigger towards infinity.

Knives also use shearing forces, but I think in terms of pressure, what you need to understand is that the area is pretty close to no area at all.

Anonymous Thu Jul 31 21:34:16 2014 No.6674813

>>6674812
Another way of thinking about it is that knives focus the force.

If you press a book onto some meat, the meat won't break. Why? Because every particle of meat is sharing some of the force, and they work together to stay together.

If you press a knife into some meat, you focus all of the force onto a thin line of particles. Suddenly, there aren't as many meat particles fighting back against the force, so they break easily.

>>	Anonymous Thu Jul 31 21:34:25 2014 No.6674814 File: 338 KB, 580x1503, 1402859000374.jpg [View same] [iqdb] [saucenao] [google] What doth life?

>>	Anonymous Thu Jul 31 21:36:13 2014 No.6674815 >>6673899 One label for it. http://en.wikipedia.org/wiki/The_Imp_of_the_Perverse

Anonymous Thu Jul 31 21:36:36 2014 No.6674816

>>6674811
In terms of fluids (and sorta in terms of solids) the average number of collisions with a surface.
Materials have a pseudo-pressure (in that it has the same units) called stress, which determines they're breaking point.
When you have a pointy knife you increase the local stress of the material (say butter) to a point where the forces that hold the butter together break.

Anonymous Thu Jul 31 21:38:12 2014 No.6674819

>>6674681
How do you know <span class="math">e^n[/spoiler] grows faster than <span class="math">n^p[/spoiler]? Because that limit goes to 0. It's circular reasoning.

A formal proof either uses L'Hopital + Induction (which is easiest I think), or going back to the definition of limit with definition of exponential function.

>>	Anonymous Thu Jul 31 21:43:59 2014 No.6674829 >>6674805 Awesome thanks anon Also if you don't mind sharing; what are you doing as a profession now? Are you using your education?

>>	Anonymous Thu Jul 31 21:48:47 2014 No.6674832 >>6674814 40

Anonymous Thu Jul 31 21:49:02 2014 No.6674833

Let's say I have a battery powered device. The battery has a limited number of charge/recharge cycles.

If I charge the device with the battery inside it, will a battery intensive app drain the battery more than a non-battery intensive app?

In other words, when you charge a device that has a 100% full battery (like a laptop or camera), is it being powered from the wall while charging the battery as charge leaks or is the battery powering the device and the charger fighting to keep the battery filled?

>>	Anonymous Thu Jul 31 21:50:02 2014 No.6674835 >>6672730 Oxygen

Anonymous Thu Jul 31 21:50:19 2014 No.6674836

>>6674829
I was working as a repair and calibration technician with a little bit of design work near the end, but then medical problems so I quit.
I used a little bit of CAD, which I find boring. Soldered a lot. Tried to explain friction and measurement errors to my boss.

I'm about to go back to school in ME focusing on applied mechanics and hopefully working in a lab on robotics.

>>	Anonymous Thu Jul 31 22:04:22 2014 No.6674852 >>6674836 Alright thanks anon get well soon

>>	Anonymous Thu Jul 31 22:06:09 2014 No.6674853 I'm 23 years old and will study computer science this year. what are my chances of doing well having no experince with programming whatsoever.

>>	Anonymous Thu Jul 31 23:24:59 2014 No.6674958 >>6674853 Start off with an easy language, and depending on what you'll learn in your classes it might help quite a bit. >>6672414 Computer Science or Electrical Engineering?

>>	Anonymous Thu Jul 31 23:26:49 2014 No.6674960 There's a neat little syndrome/fallacy that states that once a person is convinced of a fact they're unable to be convinced otherwise. Anyone know what this might be called? >>6674958 EE

>>	Anonymous Thu Jul 31 23:29:54 2014 No.6674964 >>6674958 Why not both?! I am dumb 18 yr old kid. I double major in those. I start on the 19th.

Anonymous Thu Jul 31 23:37:20 2014 No.6674975

>>6674681
>>6674819
Another way you can show it that is more rigorous (though probably not as good as just doing L'Hopital's) is to observe that
<span class="math">
\displaystyle \frac{n^p}{e^n}
[/spoiler]
is a number with p factors of <span class="math">n[/spoiler] in the numerator and n factors of <span class="math">e[/spoiler] in the denominator.
There are a constant number of n's in the numerator.
To cancel each one of these n's out, there must be
<span class="math">
\displaystyle \frac{n}{e}
[/spoiler]
factors of <span class="math">e[/spoiler] in the denominator.

.....

I'm gonna be perfectly honest, I lost my own line of reasoning here.
I'm just gonna post this anyways in the hopes someone can figure out where I was going with this and pick up where I left off.

>>	Anonymous Thu Jul 31 23:49:40 2014 No.6674985 why does venus have a lower exosphere than earth despite having a more massive atmosphere?

Anonymous Fri Aug 1 00:33:29 2014 No.6675023

>>6674681

I suppose the factorial method using repeated use of L'Hôpital's rule helps explain the problem perfectly. But that would only work if <span class="math">p \in \mathbb{Z}_+[/spoiler]. What would you even do if <span class="math">p \not\in \mathbb{Z}_+[/spoiler]? Like let's suppose <span class="math">p \in \mathbb{R}_+[/spoiler]. What would we even do then?

I don't think the problem in the book ever specified where p comes from, just as long as p > 0.

>>	Anonymous Fri Aug 1 01:04:40 2014 No.6675056 >>6672414 Sorry I know this isn't that /sci/, but I'm intimidated by /lit/ The ends ALWAYS justify the means right? > you killed a million people but at least you got that guy a seeing-eye dog. The million dead people are part of the ends, right?

>>	Anonymous Fri Aug 1 01:27:38 2014 No.6675088 >>6675056 The "means" is the process by which you achieve the "end" result. The millions of people killed would be part of the means, and the ends is getting the eye-seeing dog.

>>	Anonymous Fri Aug 1 01:29:03 2014 No.6675091 >>6675088 but you "end" up with a million dead people. They don't come back to life at the "end".

>>	Anonymous Fri Aug 1 02:19:14 2014 No.6675195 >>6674738 Not a series.

>>	Anonymous Fri Aug 1 02:19:29 2014 No.6675196 >>6674243 >>6674711 Thanks will read up on time dilation sounds cool as fuck

Anonymous Fri Aug 1 02:20:23 2014 No.6675199

>>6675023
Then you can still use the elementary proof
<div class="math">\lim_{n\to\infty}\frac{n^p}{\mathrm e^n} = \lim_{n\to\infty}\frac{n^p}{\sum_{k =0}^\infty \frac{n^k}{k!}} \leq \lim_{n\to\infty} \frac{n^p}{\frac{n^{p+1}}{(p+1)!}} = \lim_{n\to\infty}\frac{(p+1)!}{n} = 0</div>

Prof-It Fri Aug 1 02:30:08 2014 No.6675230

>>6672415
Incorrect. Proof?

add this string...
123456789

You get four 10's and one 5.

>>6672469
Because both sugar and salt are white. Some cum is sweet and some is salty.

>>6672483
You wouldn't believe me if I told you.

>>6672730
Magnetic fields.

>>6672885
Plastic surgery, diet, exercise, probably more diet, and most likely a sex change.

>>6672887
They're only perceived as practical. Once the concept of quantum mechanics is realized to be negate compared to the rest of the universe, we'll all have a good laugh.

>>6672920
Not if the trough will hold more fluid than the specified length of pipe.

>>6672935
The real problem is that he never had a cat. What was really in the box?

>>6672949
The ball would come back. Just not in your lifetime, not in the Earths lifetime, not in the Milkyway's lifetime, nor the universes lifetime. (Assuming it wasn't destroyed) The ball will return to the origin of the universe and be expelled in the next "big bang".

>>6673119
OHHH A thinker. :) I should have a private chat with you.

>>6673145
No

>>6673194
At what plattitude? There are 11 known so far. I theorize there are infinite multiples of 3 soooo.

>>6673221
T4(x) =Msquared.

>>6673326
DeJaVu and it's very common. Unless you are new here.

>>6673413
a 27 year old Russian. (he's 25 now)

>>6673698
Not when the outer force exceeds the weight to which the force is being applied. (the car is heavier than you and is the thing moving which leans inward on a gentle turn. you are lighter and not moving (stationary in the car) and being moved by the magnetic force of the speed at which you turn.)

>>6673773
Only in the dark. (not trying to be funny either) Think about it and you might see it.

>>6673783
It'd have to be real first.

>>6673900
Geometry usually does the trick.

>>6673949
No. The kinetic energy could be 100% greater. Imagine you have a parachute tied to a copper wire that drags the ground. No energy is exerted to move the parachute yet kinetic energy is collected.

Prof-It Fri Aug 1 02:43:52 2014 No.6675265

>>6673949
Look into kinetic energy collection: Tesla Motors.

>>6673990
Time is a man made theory. The fact that time doesn't really exist will evade humanity until "time travel" is completed.

>>6674018
Go watch it.

>>6674028
Turn on CNN lol

>>6674127
You're leaning the right way but you need to find something to lean on. Time doesn't exist but space does. So if you follow that time exists and you know space is real, What are you measuring "time" against if it doesn't expand or evolve like space does?

>>6674378
Easily. But only because your dick is no bigger than a queen bee.

>>6674806
Most here will say this answer is as equally stupid as you think your question. The answer however is, Magnetics. My great grandchildren will be dead before it's truly understood but 90% of all movement and physical presence is due to magnetics.

>>6674985
The interior fluidic flow is less dense at a more shallow level.

Anonymous Fri Aug 1 04:22:33 2014 No.6675387

>>6674367
>if a subsequence is supposed to be infinite, and we're constructing it piece by piece inductively, how is that reasonable enough to prove something

Because a sequence is indexed by N, so definition by induction are possible. N is countable

If you wanted to construct a function f:R->R, you would be unable to do it by induction, because R isn't countable

=> piece by piece is feasible each time you face a countable infinite.

>>	Anonymous Fri Aug 1 04:30:10 2014 No.6675398 >>6675230 So you were a troll this whole time?

baddie 101 Fri Aug 1 05:30:00 2014 No.6675469

My mind is just blanking atm.
The Mno4 is being reduced, so therefore the H2O2 must be getting oxidised to O2, right? So would the half equations be 1) Mn04 + 4H + 3E ---> MnO2 +2H2O &
2) 2H2O2 ---> 2H2O + O2

If this is right, what would the full equation then be? I'm stuck with the following: MnO4 + 2H2O2 + 3H ---> MnO2 + O2 + 4H2O

Any help would be appreciated

>>	baddie 101 Fri Aug 1 05:31:11 2014 No.6675471 File: 1.04 MB, 2560x1536, 20140801_125526.jpg [View same] [iqdb] [saucenao] [google] >>6675469 forgot picture

Anonymous Fri Aug 1 05:40:03 2014 No.6675480

>>6675469
>>6675471
depends on the acidity:

high acidity:
couples are MnO4-/Mn2+ and H2O2/O2.

low acidity:
couples are MnO4-/MnO2 and H2O2/O2.

---
half equations

first case:
MnO4- + 8H+ + 5e- -> Mn2+ + 4H2O
H2O2 -> O2 + 2H+ + 2e-

second case:
MnO4- + 4H+ + 3e- -> MnO2 + 2H2O
H2O2 -> O2 + 2H+ + 2e-

--
now you combine them in order to make the e- disappear.
If I'm correct, it gives you something like

first case:
2 MnO4- + 6 H+ + 5 H2O2 --> 2 Mn2+ + 8 H2O + 5 O2

second case:
2 MnO4- + 3 H2O2 + 2 H+ --> 2 MnO2 + 4 H2O + 3 O2

>>	baddie 101 Fri Aug 1 05:42:17 2014 No.6675483 >>6675480 Yes, I believe that would work. Thank you

>>	Anonymous Fri Aug 1 05:42:22 2014 No.6675484 >>6675195 It can be applied to sequences as well.

baddie 101 Fri Aug 1 05:54:36 2014 No.6675490
File: 1.03 MB, 2560x1536, 20140801_125519.jpg [View same] [iqdb] [saucenao] [google]

>>6675480
While I'm at it...
In this case, the 2 half equations here would be
1) Cr2O7(2-) + 14H(+) + 6e(-) ---> 2Cr(3+) + 7H2O
2) HSO3(-) + H2O ___> SO4(2-) + 3H(+) + 2e(-)

And therefore the full equation would be
Cr2O7 + 3HSO3 +11H ---> 2Cr(3+) + 3SO4 + 4H2O

Am I correct? Any corrections would be greatly appreciated.

>>	Anonymous Fri Aug 1 06:19:02 2014 No.6675509 Why are 750mL boiling flasks no longer made? I have the opportunity to buy some vintage ones but I can not find any other sources. Were they discontinued for a reason? Should I buy some?

Anonymous Fri Aug 1 06:31:57 2014 No.6675518

>>6675490
>1) Cr2O7(2-) + 14H(+) + 6e(-) ---> 2Cr(3+) + 7H2O

ok

>>6675490
>2) HSO3(-) + H2O ---> SO4(2-) + 3H(+) + 2e(-)
ok

>>6675490
>And therefore the full equation would be
>Cr2O7 + 3HSO3 +11H ---> 2Cr(3+) + 3SO4 + 4H2O

you forgot to put the charges and there is also a problem with the H, nah? there are 14 of them on the meft, 8 on the right.

just rewrite 1)+3*2), and then simplify it and it should be OK

>>	Anonymous Fri Aug 1 06:37:27 2014 No.6675528 >>6675509 buy a 1000mL one

Anonymous Fri Aug 1 06:38:54 2014 No.6675530
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http://en.wikipedia.org/wiki/Cyclomatic_complexity

Can cyclomatic complexity equations found on this page be used to approximate the human brain's complexity in relation to computer simulations, even if it's a bit over simplified?

>>	Anonymous Fri Aug 1 06:39:50 2014 No.6675532 >>6675528 Been thinking about it. Is there any reason they stopped making them though?

>>	Anonymous Fri Aug 1 06:42:03 2014 No.6675536 >>6675509 Whoa, wait, what? I can't actually find any 750ml ones for sale now that you mention it. What gives?

>>	Anonymous Fri Aug 1 06:55:11 2014 No.6675546 >>6675536 Yeah I know, I've searched all the major sites and have found nothing. I'm tempted to buy afew just to show off

>>	Anonymous Fri Aug 1 07:03:06 2014 No.6675555 >>6675546 I wonder if there's any others like that... Have any pieces you're particularly proud of?

>>	Anonymous Fri Aug 1 07:08:28 2014 No.6675561 >>6675530 not really. But if you want info on how to measure the complexity of the brain, look into the database of PNAS (the journal), several papers have been dealing with this problematic

>>	Anonymous Fri Aug 1 07:08:45 2014 No.6675562 >>6675555 Funnily enough I'm just starting my collection. All my others are just commercial lab grade glacier branded- does the job

>>	Anonymous Fri Aug 1 07:17:12 2014 No.6675567 How do physicists find out how to make engine and drives and shit? Isn't that more of engineering? If I want to work on things like that (space drives and such), what field should I go into? If physics, which subfield? Is that a viable career?

>>	Anonymous Fri Aug 1 07:21:01 2014 No.6675569 I have had middle/high school students in this volunteer program I work with ask about how mirrors "work". Is there a simple way to explain it?

Anonymous Fri Aug 1 07:24:28 2014 No.6675572
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>>6675562
I recently acquired a big ass box of large test tubes.
They're used and chipped, but not too bad.
Really nice to have around when you don't feel like washing anything or measuring much.

I'd also like to ask how to get carbon out of some glassware.
I fucked up and left the heat too high while distilling acetic acid.
It burned and now it's stuck on the inside of a flask, scrubbing with brushes isn't helping much.
I have some 30% hydrogen peroxide and sulfuric acid but i'd rather not resort to a 'nuclear' attack if it's unnecessary, might damage the glass or me.

Anonymous Fri Aug 1 07:40:05 2014 No.6675580
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>>6675572
I agree with the test tubes, cheap as and you can just throw them after.

Is it an Erlenmeyer?
You could always try gumption. It works for me, just make sure it doesn't scratch the glass though.
Never had to deal with that though.
You could just fill it will 0.1 mol HCL for a day or two and see how it does, this has worked to removed iron stains. Make sure you plug it though

>>	Anonymous Fri Aug 1 07:53:15 2014 No.6675587 >>6675567 bump for this

>>	Anonymous Fri Aug 1 08:11:03 2014 No.6675595 I lost 20kg of weight, yet I can't see any difference in my reflection. Could someone explain why that is?

>>	Anonymous Fri Aug 1 08:13:11 2014 No.6675596 >>6675595 A large portion of that will be waterweight, and you would have grown used to the change in your appearance over the amount of time it took to lose the weight. If you compare photographs, the change should be recognizable.

>>	Anonymous Fri Aug 1 08:16:22 2014 No.6675597 >>6675596 Interesting. Thanks

Anonymous Fri Aug 1 08:40:05 2014 No.6675620
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>>6675569

Sure, a mirror is not that complicated. Light bounces off it in the same direction it arrives at. That's it. So when you look at a particular spot in a mirror, you're looking back along that ray of light to a particular direction that is the source of that light. So you get a one-to-one correspondence between sources of light and places to see that light in the mirror, in other words you get a picture of the room.

For objects that aren't mirrored, the light reflects it in all different directions, so you can't tell where it came from by looking at it, and you'll see light from different sources at the same spot.

The image shows the difference. (specular reflection = mirrored surface)

>>	Anonymous Fri Aug 1 08:41:48 2014 No.6675623 >>6675567 Bump for the second part >If I want to work on things like that (space drives and such), what field should I go into? If physics, which subfield? Is that a viable career?

Anonymous Fri Aug 1 08:43:18 2014 No.6675625

>>6675620

I should add, that physically the difference is that the reflective surface is very smooth at the microscopic level, as that picture also shows. That's why highly polished surfaces act like mirrors - you're literally smoothing them out enough that the light bounces more predictably.

not going to grad school Fri Aug 1 08:44:50 2014 No.6675627

>>6675530
>>6675561
degree in computer science and psychology. (specifically Neuro-psych, took graduate Neuro courses, with grad students) So I have both relevant backgrounds.

Yes and no. You could use this to measure the complexity of an ANN so why not on natural NN? It's just a measure of computational complexity. The control flow graph would essentially be a graph of the neuro/glial connections with each neuron/glial cell being broken down into graphs representing internal computation. I.e neurons talking to neurons, neurons calculating axon input, nodes of ranvier, astrocytes managing homeostasis, etc etc.

The thing is brain computation is so complex we're not even sure what all the paths are, so we couldn't actually make an accurate version of that graph. There is evidence that there are quantum level computations, specifically for smell, so who really knows how deep the rabbit hole goes?

>>	Anonymous Fri Aug 1 09:25:26 2014 No.6675666 >>6675567 bump

>>	Anonymous Fri Aug 1 09:55:38 2014 No.6675686 File: 962 B, 294x29, CodeCogsEqn.gif [View same] [iqdb] [saucenao] [google] >>6673703 The basic solution is, I think, just this ugly thing here. Unless I've made a fundemental error, which wouldn't surprise me, I never liked ODEs

Anonymous Fri Aug 1 10:03:04 2014 No.6675693

HVAC technician here. When I am doing diagnostics on a system I often must take temperature readings on the refrigerant lines, to measure how superheated the refrigerant is entering the suction port of the compressor, and how subcooled the liquid refrigerant is after leaving the condenser. My question id this: how accurate are me readings using a surface temperature sensor on the copper linesets? I am aware that copper is highly conductive but it must be insulating the refrigerant from the sensor by some measurable amount. Sorry for the longwinded explanation.

>>	Anonymous Fri Aug 1 10:09:23 2014 No.6675699 >>6674853 A great forst language to learn is C

>>	Anonymous Fri Aug 1 10:12:19 2014 No.6675700 >>6675091 So, sorry, what is your question? Is it whether the end always justifies the means? because no, it's pretty obvious.

>>	Anonymous Fri Aug 1 10:26:45 2014 No.6675708 stupid question which is only somewhat related to sci.. Ive been studying CS for two semesters now, and I find programming boring, but love the feeling of actually completing a working piece of software. Should I quit CS?

Anonymous Fri Aug 1 10:44:13 2014 No.6675721

>>6675693
Yes, any substance, even one with a high thermal conductivity, has some amount of thermal resistance. But the resistance of the copper affects the speed at which it will change temperature, not the temperature it will eventually reach. So if you are taking a readings on a copper line and the temperature is stable, it's a safe bet that reading is accurate to the limit of the sensor.

None !NezumipFxw Fri Aug 1 11:26:08 2014 No.6675762

I have a device with a 3-axis MEMS gyroscope. The readings are labeled X, Y and Z, and the documentation says they are in milidegree per second.
My question is, what does this data actually represent? Are those coordinates of angular velocity pseudovector? Or do they mean something else?

>>	Anonymous Fri Aug 1 11:32:51 2014 No.6675773 >>6675721 thanks a lot. good to know

>>	Anonymous Fri Aug 1 11:35:25 2014 No.6675775 If I want to be one of those people working on theoretical warp drives, what field of science should I go into?

>>	None !NezumipFxw Fri Aug 1 11:48:59 2014 No.6675787 >>6675775 Theoretical physics?

Anonymous Fri Aug 1 11:49:58 2014 No.6675788

I got into engineering thinking I could get great jobs. I actually did but now I hate the entire field itself because it's all just dealing with higher management and trying desperately to get a patent. At this point I think going into a physics major would help me get out of this rut in my life. How could I start off?

>>	Anonymous Fri Aug 1 11:52:43 2014 No.6675792 >>6675775 Alcubierre drive? I think there was a thread a while back explaining why these were improbable in this generation. But I guess either theoretical physics or, if you want to help bring this to reality, some form of engineering.

Anonymous Fri Aug 1 11:57:53 2014 No.6675799
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Why do we use sig figs in chemistry? For God's sakes, we're making our figures less accurate; we *could* be accurate out to seven figures, but we're going to cull our number at 2 figures; WHY WOULD WE WANT TO DO THIS?!

>>	Anonymous Fri Aug 1 11:58:10 2014 No.6675800 >>6675387 Thanks.

>>	Anonymous Fri Aug 1 12:02:00 2014 No.6675805 Is it possible to double major in math and applied math and pull a good GPA or am I making a mistake? All the applied math classes I took were really boring and easy so I took theoretical math as well out of interest and challenge.

>>	Anonymous Fri Aug 1 12:11:52 2014 No.6675818 >>6674757 Anyone?

>>	Anonymous Fri Aug 1 12:13:13 2014 No.6675820 >>6675799 What are you talking about?

Anonymous Fri Aug 1 12:23:54 2014 No.6675834

>>6675799
I could be mistaken, but if I'm understanding your question correctly, we actually *couldn't* be accurate out to seven figures in these examples you're talking about.

Assume you have two measured quantities; it doesn't matter what you're measuring, but let's just assume one of your measurements is
0.5467
and the other is
0.25
Now it is apparent that the apparatus measuring the first result is accurate to more digits than the device measuring the second. Why does this actually matter, though?

Well, just because our measurements don't tell us that 0.25 expands onward, that doesn't mean that it doesn't. The difference between 0.2500 and 0.25 is a major one, it's the difference between knowing and not knowing just how accurate your result is.

Now, let's multiply these two numbers together; our final answer, without accounting for significant figures, is 0.136675.How does it make sense that our answer has more significant figures than either of our devices could measure? There's no way we can actually assure that this number is accurate to that many significant figures. For this reason, we round two the least significant measure, so our final answer would be .14.

Tl;dr We strive for precision in our results. Using Sig Figs allows us to maintain precision in our results in assuring that we don't overstretch our answers to a point where accuracy is dubious.

>>	Anonymous Fri Aug 1 12:30:55 2014 No.6675843 Is a SKYLON-like system for delivering heavy payloads more cost effective than standard chemical rockets? How much maintenance would be needed after each flight? Could it replace chemical rockets for the COM SAT industry?

>>	Anonymous Fri Aug 1 13:22:54 2014 No.6675927 >>6675834 This made some sense to me, but I'm seriously considering withdrawing from gen. chem. this semester because the math is intimidating and nothing I'm reading about it is making it click for me. Thanks, though.

>>	Anonymous Fri Aug 1 13:28:40 2014 No.6675939 >>6675762 Anyone?

Anonymous Fri Aug 1 13:46:20 2014 No.6675965
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>>6675762
This was one of the problems that started my foray into real mathematics.

> Are those coordinates of angular velocity pseudovector?
yeah sorta
To convert them into a quaternion:
<span class="math"> \dot{q} = \frac{1}{2} \Omega \otimes q [/spoiler]
my notes are incomplete

>>	Anonymous Fri Aug 1 13:54:24 2014 No.6675981 >>6675965 Thanks. So I can convert them to radians/sec and plug them into a 3x3 cross-product matrix to get a transformation from the reference frame of the body to the reference frame of world, right?

>>	Anonymous Fri Aug 1 16:19:28 2014 No.6676295 >>6672858 lobsters are biologically immortal

Anonymous Fri Aug 1 16:43:48 2014 No.6676338

Ive shortened this question quite a bit, but here goes:

Say 30 warriors are trapped in a cave, and the commander, one of the 30, opts to have them all commit suicide. He lines his men
up in a row of 30, the first 15 of which are cowards who will not kill themselves if not forced to. After the commander appoints
the first man to commit suicide, two men in line are skipped so every third will commit suicide, until two men are left.
If the two men are cowards, both will surrender. If they are both devoted warriors, they will both commit suicide. If one of both is
left they will face off, with the coward having a chance of 0.2 to win and surrender afterwards. If X is the number of warriors that
surrender, what are the chances P(X=k) for x=0,1,2?

What I did to solve this question is note that if the warrior on position n is chosen to start, the two men left are on
positions [(n+16) mod 30, (n+26) mod 30]. By counting out I found the following numbers:

n=1,2,3,4,30 : Two devoted warriors remain (5/30)

n=15,16,17,18,19 : Two cowards remain (5/30)

n=5,6,7,8,9,10,11,12,13,14,20,21,22,23,24,25,26,27,28,29 : One coward and one devoted warrior remains (20/30)

So it follows that

P(X=0) = 5/30 + 20/30 * 8/10 = 21/30

P(X=1) = 20/30 * 2/10 = 4/30

P(X=2) = 5/30

Which works out alright, as P(X=0)+P(X=1)+P(X=2)=30/30=1 as it should. But I Feel like Ive brute forced this question,
what would be a more theoretical approach?

Anonymous Fri Aug 1 16:44:49 2014 No.6676340

>>6676338
A second question:

Prove that <span class="math">\binom{2n}{n} = \sum_{k=0}^{n} \binom{n}{k}^{2}[/spoiler].

What I did to prove this is the following.

Let A, B be two sets so that |A|+|B|=2n and the intersection of A and B is the empty set. Let k elements be chosen from A, so that n-k are chosen from B.
This can be done in <span class="math">\binom{n}{k} \cdot \binom{n}{n-k}[/spoiler] ways. As <span class="math">\binom{n}{k} = \binom{n}{n-k}[/spoiler], <span class="math">\binom{n}{k} \cdot \binom{n}{n-k} = \binom{n}{k}^{2}[/spoiler].
Because <span class="math">0 \leq k \leq n[/spoiler], the sum includes all possible choices for k, so <span class="math">\binom{2n}{n} = \sum_{k=0}^{n} \binom{n}{k}^{2}[/spoiler].

Here Im thinking the other way around; isnt there a more direct way to prove this result?

Thanks in advance

>>	Anonymous Fri Aug 1 16:45:32 2014 No.6676342 >>6672730 time, retard next

>>	Anonymous Fri Aug 1 16:50:06 2014 No.6676346 File: 7 KB, 538x201, latex.gif [View same] [iqdb] [saucenao] [google] >>6676340 Make do solution attached.

Anonymous Fri Aug 1 17:03:02 2014 No.6676358
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What exactly is happening to unobserved systems? For instance, an asteroid produced as the result of a systematic event beyond our ability to observe could still destroy the planet.

Because of quantum mechanics only producing an actual result after being observed, does that mean that unobserved systems are random, or are simply the results of enormous cascades of consequences from the big bang?

Anonymous Fri Aug 1 18:13:59 2014 No.6676443

When it comes to Calc II, with regards to all the different types of tests (nth term, comparison, root, etc), which one are you supposed to use first?

I understand the tests and how to do them, I just don't want to run through all of them before I find one that works. Is there a flowchart or something that works universally?

>>	Anonymous Fri Aug 1 18:29:29 2014 No.6676463 >>6676443 From what I remember, Ratio Test was always done first, then you'd move on to comparison tests.

Anonymous Fri Aug 1 18:40:13 2014 No.6676477

Question: Am I on the right track?

So, for warp to happen, there needs to be spacetime contraction in front of a ship and spacetime dilation behind the ship. Currently, the only way for spacetime dilation to happen is with negative mass or an application of the Casimir Effect on a large scale. So if we put two giant Casimir setups in front and behind a given ship, one dilating the energy behind the ship, one compressing it in front of the ship, the "warp" effect is achieved.

Question 2:
How the fuck would one go about making a spacetime bubble/ring around the ship so the laws of physics aren't broken?

Anonymous Fri Aug 1 18:48:27 2014 No.6676494

>>6675981
No. It's not that easy, I'm sorry.
We had similar issues with our quadcopters.

This paper describes how to get an orientation quaternion from a 9DoF, but you can just look at the gyro part:
An efficient orientation filter for inertial and
inertial/magnetic sensor arrays, Sebastian O.H. Madgwick
This wiki page describes how to convert those to Euler angles and rotation matrices.
http://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles

Also look into directional cosine matrices, I can't find the paper I used.

>>	Anonymous Fri Aug 1 18:54:29 2014 No.6676504 >>6673799 come on, anyone

Anonymous Fri Aug 1 19:05:42 2014 No.6676515

Spent my entire school years steering clear of Maths and Physics. They were probably my least favorite subjects and it seemed to be a pretty popular opinion.

Now I'm in my early 30s, dropped out of 2 colleges (languages & computer science). After watching a lot of videos the past few years on astrophysics, science talks & debates I feel like I never understood how cool those subjects could be. Is it too late to try and pursue a career in those fields?

Anonymous Fri Aug 1 19:10:03 2014 No.6676521

>>6676443
I'm going to operate under the assumption that you know the tests I'm referring to, and know them by the same name. If that's not the case just ask.
For the infinite series
<div class="math">
\displaystyle \sum^{\infty}_{n=0} a_n
</div>

>Test for Divergence
Make sure that the limit of the terms of the series actually approaches zero.
i.e. <span class="math">\displaystyle \lim_{n\to\infty} a_n = 0[/spoiler]
If it doesn't, the series is divergent and you can stop.

There's no particular order to stick to after that, just certain patterns to recognize.
>Integral Test
Use this if <span class="math">a_n[/spoiler] is easily integratable.
>Comparison Test
Try this when slightly altering the original <span class="math">a_n[/spoiler] by removing, adding, or changing constants will create either
1) A new series that is always greater, and is easily shown to converge.
2) A new series that is always lesser, and is easily shown to diverge.
>Limit Comparison Test
Try this when altering <span class="math">a_n[/spoiler] in the Comparison Test produces a function that follows neither 1) or 2).
>Alternating Series Test
Try this when...you've got an alternating series...
>Ratio Test
If I recall this is a really versatile one but is best when you have exponentials and/or factorials.
>Root Test
Try this ONLY when <span class="math">a_n[/spoiler] is raised to the nth power.

>>	Anonymous Fri Aug 1 19:14:32 2014 No.6676522 http://phys.org/news/2014-06-physicist-slower-thought.html approximately how long until this speed of light paper is confirmed/refuted?

Anonymous Fri Aug 1 19:15:00 2014 No.6676524

>>6675567
>>6675587
>>6675623
>>6675666
Not a physicist or engineer, but I thought it was pretty common knowledge that if you want to actually make shit you go into engineering. Physics is a basic science, all it's concerned with is figuring out how the natural world works. You could probably backdoor your way into engineering with a physics degree, but it would a much more difficult and longer route than simply getting an engineering degree.

>>	Anonymous Fri Aug 1 19:15:40 2014 No.6676527 >>6676515 Depends on what you mean by career.

Anonymous Fri Aug 1 19:29:28 2014 No.6676539
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Any recommendations for books that a 13 year old would enjoy/get a lot out of?

Best friend's little brother's birthday's coming up, and he mentioned off hand that he'd like a text book. Kid loves math and science (going through a bio and astronomy kick atm) and learns fairly quick.

Would Byrne's Elements of Euclid be too much?

Thanks in advance, /sci/.

>>	Anonymous Fri Aug 1 19:39:31 2014 No.6676546 Does the fact that we exist currently mean that infinity must exist also?

Anonymous Fri Aug 1 19:45:17 2014 No.6676552

>>6676539
Martin Gardner has many books on recreational mathematics. They have great puzzles.

Textbook recommendations require more information. Hand him your old copy of Stewart and see if he's overwhelmed. I tried reading a calc textbook at around that age. Got distracted pretty quick and only got the barest information about set theory

>>	Anonymous Fri Aug 1 19:49:46 2014 No.6676557 >>6676546 How could the two be linked?

>>	Anonymous Fri Aug 1 19:55:31 2014 No.6676564 >>6676557 I mean in the sense that how could everything that exists now have come from nothing? I just don't understand it, hasn't there always been something and always will have to be something?

>>	Anonymous Fri Aug 1 20:24:53 2014 No.6676610 >>6675708 Definitely.

>>	Anonymous Fri Aug 1 20:53:13 2014 No.6676671 Is it possible to use polynomial interpolation to predict future events?

>>	Anonymous Fri Aug 1 22:55:14 2014 No.6676809 >>6676546 It doesn't make any sense to say "infinity exists" just as it makes no sense to say "2 exists".

>>	Anonymous Sat Aug 2 10:18:06 2014 No.6677403 What do I need for precalculus? Algebra for sure, but what else? Geometry, Trigonometry, Probability?

Anonymous Sat Aug 2 10:19:27 2014 No.6677408

>>6677403
You'll need a measure-theoretical understanding of probability theory for precalculus. A measure-theoretical knowledge of probability with require a lot of real analysis and some linear algebra, so you're several years away from precalculus, at this point.

>>	Anonymous Sat Aug 2 10:25:34 2014 No.6677420 >>6677408 I just entered high school so you are actually right. Learning mostly autodidactically though, the math we do in school is simple.

Anonymous Sat Aug 2 10:33:21 2014 No.6677431

Can't we disprove the notion of physically traveling backwards in time due to the law of conservation, i.e. someone traveling back in time would add heretofore inexistant (or, more specifically, not yet existant) mass to the universe and therefore be disallowed by the laws of physics?

What are some ways t circumvent this speculative problem in an overall speculative issue?

>>	Anonymous Sat Aug 2 10:52:04 2014 No.6677463 File: 27 KB, 620x465, 4-Rodger-AP.jpg [View same] [iqdb] [saucenao] [google] >>6677431 Well that's easy. By reducing your mass to zero.

Anonymous Sat Aug 2 10:57:01 2014 No.6677468

>>6677431
Wouldn't the extra mass added to the universe by your "arrival" back in time be offset by the lack of your mass in the future?
Up until you arrive at the point you left, that is.

I could be completely wrong here, it's just a thought experiment, and I'm way out of my field here.

Anonymous Sat Aug 2 10:57:47 2014 No.6677470

>>6677431
You've hit upon one of the great paradoxes not only of time travel but of Time itself. Surely it must be the case that mass is conserved - neither created nor destroyed. But if we look around we see new mass coming into existence all around us: animals give birth, plants grow, flowers blossom, mushrooms fruit. How can it be the case that as time passes, more and more mass comes into existence? The only solution, one that Physics is starting to realize, is that Time must be a fiction. Indeed, if one accepts Time, one is forced to deny the conversation of mass.

Anonymous Sat Aug 2 11:02:41 2014 No.6677477

>>6677468
This assumes that future and past are happening simultaneously. Even if, it would be two different systems. Travelling back in time is impossible for a variety of logic reasons, but even physically it's not possible. Even though energy remains inside a closed system, the density and heat at the beginning of the universe can never be reached again with the energy we have now. Even assuming the total energy remains the same, thus not hurting the law of conservation of energy, will not mean that transformed energy is able to return to a former state.

>>	Anonymous Sat Aug 2 11:04:46 2014 No.6677478 >>6672496 lol

Anonymous Sat Aug 2 11:05:15 2014 No.6677479

>>6677468
I'm way out of my depth, but I do like that thought. I'm imagining time as one long grocery shelf of cans, and you just move one can back. With conservation though, the shelf has no empty spaces, so you'd have to actually swap cans to move them, i.e. replace the mass traveling backwards with an equal mass at the point of departure.

>>	Anonymous Sat Aug 2 11:05:45 2014 No.6677480 File: 106 KB, 1024x683, omg.jpg [View same] [iqdb] [saucenao] [google] >>6677470 >more and more mass comes into existence >deny the conversation of mass >mfw mass is transforming into energy all the time >mfw mass equals energy Just go. Now.

Anonymous Sat Aug 2 11:13:51 2014 No.6677485

>>6677479
So am I, I'm a 2nd year Math undergrad, so I'm speaking purely theoretically, out of my arse, if you will.
But you can't create mass, so would someone have to travel forward in time to the exact time you left? So, you'd essentially swap places with someone in the past.
I guess.

>>6677477
My vague understanding of QM shows that in some cases, the past and future are happening simultaneously (I haven't got the article handy, but there was an article in New Scientist about particles travelling certain paths in accordance to characteristics which were only looked for once the test was over).
I don't quite understand what you're saying about energy, you're saying time travel isn't possible because we haven't got enough energy in our closed systems?

>>	Anonymous Sat Aug 2 11:15:12 2014 No.6677489 >>6677470 >we see new mass coming into existence all around us: animals give birth, plants grow, flowers blossom, mushrooms fruit These aren't examples of new mass coming into existence magically

>>	Anonymous Sat Aug 2 11:15:46 2014 No.6677490 >>6672414 How do nanobots violate the laws of physics?

>>	Anonymous Sat Aug 2 11:17:09 2014 No.6677492 >>6677489 Where else does it come from? Some women, like Angelina Jolie, even lose weight when they're pregnant, meaning that they are taking in less energy than before, but creating new mass inside their Wombs.

>>	Anonymous Sat Aug 2 11:18:19 2014 No.6677497 >>6677492 Well, son, you see... When a man and a woman love each other very much...

>>	Anonymous Sat Aug 2 11:19:17 2014 No.6677498 >>6677492 I'm not a biologist, so I can't speak with total conviction, but if you seriously think creating mass is that easy, your understanding of physics, or biology for that matter, isn't even middle school level.

Anonymous Sat Aug 2 11:37:03 2014 No.6677521

>>6677485
>I don't quite understand what you're saying about energy, you're saying time travel isn't possible because we haven't got enough energy in our closed systems?

Well the universe has a fixed amount of energy which can transform back and forth into mass but never decrease total. This is a fundamental principle of physics. If you could travel in time, you would need to make sure the total energy remains the same. But even if you somehow manage to do that (the idea of swapping was mentioned), it would still not work. The assumption is wrong that you can arbitrarily convert energy into mass and vice versa. For example a star of the first generation can not countain any matter heavier than iron, because you need at least one supernova to get elements heavier than iron. After heavy elements are created, they can not turn back into hydrogen and helium without adding more energy. This is why the expansion of the universe is irreversible. This very fact also makes time travelling impossible, because it would assume an arbitrary energy transformation.

>>	Anonymous Sat Aug 2 11:57:00 2014 No.6677546 >>6677521 If we did somehow find a way to feasibly convert energy to matter, and vice versa, would that make time travel (via swapping, say) more realistic? Presuming doing so is possible in the first place.

Anonymous Sat Aug 2 11:58:49 2014 No.6677547

>>6677521
AKCHUAAAALLY

One of the acknowledgements we make is within our universe, i.e. the closed system, matter and energy are conserved. If you there were a mechanism for time travel, there's nothing we have that sets rules on "extratemporal" travel, and mass and energy once that happened.

I like an interpretation where if you were to time travel, you'd either find nothing, or another universe, "behind" ours. It's very sensible, if you have a train moving along tracks at a set speed, and you look behind it, do you see more trains? Of course not. If objects traveling in time worked the same way, you'd either encounter nothing, or perhaps other things, where their universal properties may have been influenced by their initial temperal differential.

>>	Anonymous Sat Aug 2 12:02:19 2014 No.6677554 >>6673088 >1) Evolution doesn't 'care' about anything. Yes it does. Care. Verb Definition 2: look after and provide for the needs of. Evolution does that all the time.

>>	Anonymous Sat Aug 2 12:05:16 2014 No.6677557 >>6677554 Evolution is not a thing though

Anonymous Sat Aug 2 12:05:31 2014 No.6677558

>>6677547
Or, in the instance of infinite dimensions, hopping sideways into a dimension where every probability is exactly the same between our universes except for time moving a fraction of Planck time slower, thus SEEMING like we've traveled backwards in our own universe.

In fact, based on infinite universes, every moment of our universe's entire timeline is duplicated essentially sideways from our own, future included.

Anonymous Sat Aug 2 12:08:33 2014 No.6677561

>>6677558
They explored that in Stargate SG1. After traveling in time/dimension to stop the bad guy or whatever, they have to "re-tune" the traveling mechanism, or they'd wind up in mostly the same universe. One of the fun ones is as they're waiting for people to return from the mission, they tune the mirror to find one of their people waiting - but she hadn't been promoted in that universe.

>>	Anonymous Sat Aug 2 12:27:06 2014 No.6677582 >>6677546 Yes. If you can split a gold atom into hydrogen without using any engery, you can do that. >splitting an atom >without energy If you do this, you become god.

Anonymous Sat Aug 2 12:30:23 2014 No.6677588

>>6677558
Circulating fantasy theories/10

Apart from being completely irrelevant, alternating timelines are deprecated and novel content. We live on this one timeline exactly because all those alternative events NEVER happened. Not even in another dimension. All of this is the fantasy of people dreaming about what-if scenarios, which are interesting but horribly inscientific.

>>	Anonymous Sat Aug 2 12:36:46 2014 No.6677597 What topic should I write my bachelor´s thesis in physics about? I've been thinking about electronics, signal processing, analogue filters or something like that, but I'd like to hear the opinions of random strangers.

>>	Anonymous Sat Aug 2 12:42:59 2014 No.6677603 >>6677588 Well, double erasure. >>6677597 Things other than photons having particle-antiparticle relations.

>>	Anonymous Sat Aug 2 13:05:02 2014 No.6677630 >>6677597 Write about why autism intensifies with the self perceived technoogical abilities.

>>	Anonymous Sat Aug 2 14:05:44 2014 No.6677711 >>6677582 I never said without using ANY energy, I just said feasibly, so a relatively small amount of energy

Anonymous Sat Aug 2 14:28:35 2014 No.6677764

>>6677711
You get the fact that even if it uses a marginal amount of energy, it will be impossible, right? Because if you tavel back in time, the universe must be recreated using the same energy available. But tis conversion must be without any loss of energy, else the past would contain less energy, which is impossible.

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/sci/ - Science & Math