/sci/ - Science & Math

[Physics Guy No.5707179]

Taking your physics questions
If they aren't too fucking stupid

GO

[Anonymous No.5707181]

At what radius does light orbit the sun?

[Anonymous No.5707183]

>>5707179
What field?

[Anonymous No.5707186]

what would happen if a black hole collided with it's white hole.

[Anonymous No.5707188]

are all points in time and space connected?

[Anonymous No.5707189]

Treat in the same manner, by means of axioms, those physical sciences in which already today mathematics plays an important part; in the first rank are the theory of probabilities and mechanics.

[Anonymous No.5707192]

>>5707186
gray hole, duh

[Anonymous No.5707198]

Question of the century

[Anonymous No.5707232]

Does the universe itself have a Schwartzschild radius, and if so does would that mean at one point in it's expansion it was below that and would technically be a black hole?

[Anonymous No.5707246]

>>5707181
http://en.wikipedia.org/wiki/Photon_sphere

>>5707186
The Black hole and the white hole are actually the same object:
Hawking, S. W. (1976). "Black Holes and Thermodynamics". Physical Review D 13 (2): 191–197. Bibcode:1976PhRvD..13..191H. doi:10.1103/PhysRevD.13.191.

>>5707188
Define "connected"

>>5707232
Yes it has a schwarzchild radius. No, it was never a black hole.

[Schaiffe !zribfvVT8o No.5707257]

>>5707179
When firing a bullet underwater, how far will it travel before water resistance slows it to a stop?
I know it will depend on the initial velocity, and some are more high powered than others, so just use the average or something.

[Physics Guy No.5707265]

>>5707257
I ain't gonna do a long ass calculation for you.

[Anonymous No.5707270]

>>5707179
Should I study technical physics (something connected to astronomy) or robotics as my second degree? (first being chemical technology, which I find boring)

Also how much physics is there in robotics?

[Anonymous No.5707272]

if we had more elementary functions or operators that we could mathematically describe things with then would we be able to analytically solve many-electron schroedinger equations or navier stokes equations?

[Anonymous No.5707277]

>>5707257
Not OP. The drag force is often proportional to the velocity squared, but it also depends a lot on the geometrical structure of the object as well as its radius. That's the most precise information I can give you right now

[Anonymous No.5707300]

If evlution its only a thery (a geuss) why are ther still monkeys?

[Anonymous No.5707311]

Why do Newton's laws apply to acceleration, and not the 3rd, 4th, or any other derivative of a particle's motion?

[Anonymous No.5707322]

>>5707311
Newton's laws are the axioms of classical mechanics so to speak so there's not really a precise answer to that. They can easily be shown to be compatible with Kepler's laws of planetary motion which is probably why Newton arrived at "acceleration" and not "velocity" or "derivative of acceleration".

[Anonymous No.5707325]

If the universe is infinite, how come there are no well behaved free particle wavefunctions?

[Anonymous No.5707326]

What's actually happening when light reflects off an object?

[Anonymous No.5707324]

>>5707311
All that shit you use is just leading order approximations.

[Physics Guy No.5707333]

>>5707325
>infiite

Define infinite. You need to stop this bullshit, and talk in scientific terms. You need a clear definition of what you are talking about.

[Anonymous No.5707335]

>>5707322
Maybe I'm only taking this on faith, but I don't think that a statement's being "axiomatic" in one system necessarily restricts it from being explained in another, of possibly weaker assumptions.
>>5707324
Could you elaborate?

[Anonymous No.5707342]

>>5707257
there was a myth busters epi about this

[Anonymous No.5707343]

Is a wavefunction a real field? or a metaphor for our probability of where quantum particles may be

[Anonymous No.5707347]

>>5707326
It depends whether you're asking from a perspective of "wave" or "particle". As a wave, some of the light simply gets transmitted while some gets reflected like all other waves you can think of. In the perspective of particles, the photons are absorbed by particles in the surface which then deexcites and reemits the light.

[Anonymous No.5707358]

>>5707333
Well by infinite, I mean not closed, and extending spatially forever. For instance imagine an electron in an infinite empty plane. QM predicts such an electron can never exist. This seems to contradict basic intuition.

[Anonymous No.5707357]

>>5707343
You could say it's a real field, because basically it connects every point with equal probability of finding an electron. It doesn't mean it's at some exact point, but it won't be outside.

[Anonymous No.5707364]

if a normal space ship was traveling at very high speeds, it would burn up because of all the gas in space causing friction.

so, how fast could a space ship fly without destroying itself? let's say it's made out of normal steel.

[Physics Guy No.5707369]

>>5707358
>QM predicts

Are you using naive Quantum Mechanics? Shit that is known to be inheretly flawed and outdated? Why? Do you not know of QFT?

[Physics Guy No.5707372]

>>5707358
What do you mean by "closed"? Again, shit defintions are shit. There are probably like 15 different types of "closure" as defined by mathematicans and physicists.

Just as there are many defintions of "infinite".

[Physics Guy No.5707375]

>>5707369
http://en.wikipedia.org/wiki/Quantum_field_theory

[Anonymous No.5707383]

What's the difference between a phase transition (criticality) and a bifurcation (as in chaos theory)?

[Physics Guy No.5707386]

>>5707343
The wavefunction is as real as anything we know. It is actually more "real" than things like position and momentum.

[Anonymous No.5707388]

>Taking physics questions
>"Answers" every question with a link or belittlement for lack of pace with technical terms

Have you considered academia, OP?

[Anonymous No.5707391]

Doing solid state, having trouble evaluating the integral from |k| to kf (where where k is the vector kx+ky+kz and kf is the radius of a fermi sphere), the function to integrate is k^2*d^3k. It's apparently kf^5*pi*4/5. Any tips?

[Anonymous No.5707392]

Great I've been waiting. I've been trying to prove why a diffraction grating with N-slits has N-1 side minima. My idea was be to set up the formula for the intensity relative to the angle and then calculate the roots on the interval between 2 cardinal maxima. But shit ain't working, propably because my equation is wrong.
Could you link me to any related articles or something? Can't seem to find anything that actually helps me...

[Physics Guy No.5707399]

>>5707392
Between two principal maxima there are N-1 zeros.

This is just application of calculus
http://courses.physics.illinois.edu/phys214/lectures/lecture4.pdf

[Anonymous No.5707405]

>>5707399
You skipped my question you stupid faggot.

[Physics Guy No.5707408]

>>5707405
Was your question "fucking stupid"? See OP Post

[Anonymous No.5707415]

>>5707408
>OP Post
original post post?

[Anonymous No.5707421]

>>5707358
It doesn't. There is an event horizon at the edge of the (expanding) universe and we are inside it.

[Anonymous No.5707425]

What does physics say about the book of mormon?

[Anonymous No.5707439]

[Anonymous No.5707453]

When you started learning physics, what were you're approach? Like accepting the facts or are you the new Einstein and fully understood everything? Im having a test in special relativity and nuclear physics (intermediate level or whatever) and i'm having some trouble understanding few things … Though I won't post any questions because my mother tongue isn't english and therefore I have to translate everything

[CANCER No.5707458]

>>5707179
what creates a magnetic field?

[Anonymous No.5707460]

>>5707383
A bifurcation is when you vary some parameter in a system that at some point changes the system's stability in some way. For example, if you balance too much mass on top of a beam it will buckle (pic related). The type of parameters is everything such as "mass", "density", "frequency", "number of animals" etc. etc. There are many different kinds of bifurcations that change the stability in the system in specific ways. As far as I know, "phase transition" has no real meaning in the study of nonlinear dynamics and chaos.

[Anonymous No.5707463]

>>5707458
Moving charged particles (currents) create magnetic fields.

[Anonymous No.5707468]

>>5707460

you sound like a fucking moron

[Anonymous No.5707473]

>>5707468
Thanks.

[Anonymous No.5707471]

If we were to make 1.999... into an integer would it be 1 or is it already an integer?

[Anonymous No.5707476]

>>5707471
it would be an irrational integer

[Anonymous No.5707478]

>>5707471
Are you there OP?

[Anonymous No.5707485]

[Anonymous No.5707486]

>>5707476
But my math textbook claims that no integers can be irrational. (I'm sorry if the question is stupid but I just started high school so my knowledge of math is very limited).

[Anonymous No.5707488]

E =/= MC2

prove me wrong

[Anonymous No.5707491]

>>5707476
>irrational
>integer
Pick one.

[Anonymous No.5707499]

>>5707488
We can't
You're assuming that E=/=MC2 so therefore it is impossible to disproof that.

[Anonymous No.5707503]

>>5707488
It is for the rest mass. In a framework of inertial reference system, E^2 = p^2c^2 + m^2c^4 where p is momentum of the particle. If the particle is not moving, its energy is given by E_0=mc^2. This is also typically what we would define as as an object's "mass".

[Anonymous No.5707518]

>>5707486
>>5707491
Not for pseudo-reals such as 1.999....

[Anonymous No.5707517]

Bumping for Coulomb

[Anonymous No.5707521]

>>5707518
Ok TY

[Anonymous No.5707527]

>>5707246
>No, it was never a black hole
Strictly speaking wasn't it a black hole at t=0 as all the energy in the universe was in a point of zero volume

[Anonymous No.5707528]

>>5707471

Not OP but technically 1.999... = 2, if you're saying that 9 repeats infinitely. If you studied series then this should be familiar to you.

1.9999....
= 1 + 9/10 + 9/100 + ...
= 1 + 9/10(1 + 1/10 + 1/100 + ...)
= 1 + 9/10(10/9)
= 1 + 1
= 2

Where I uses a series summation.

[Stupidguy123 No.5707539]

>>5707528
I know that proof, and i assumed that the answer was 2 but i was curious because of my limited understanding of math.
//Why the hell would i ask the question is i didn't know?

[Anonymous No.5707548]

>>5707539
>I know that proof, and i assumed that the answer was 2 but i was curious because of my limited understanding of math.
>//Why the hell would i ask the question is i didn't know?

ahh well I figured I would toss that out there just in case, besides answers like "irrational integers" make people trying to learn worse off, maybe someone will benefit from my proof -shrugs-

[Stupidguy123 No.5707556]

>>5707548
Ok. If anybody is further interested in the subject but doesn't quite understand it read this for a start: http://www.purplemath.com/modules/howcan1.htm

[Anonymous No.5707580]

>>5707246
If you wanna get meta, its still a black hole

[Anonymous No.5707585]

>>5707471
pic related

[Anonymous No.5707587]

I was thinking in my math class today about what shape bounds infinity, and I guess that's a similar question to what shape is the universe?

[Anonymous No.5707597]

An investment of $45000 was made by a business club. the investment was split into three parts and lasted for one year. the first part of the investment earned 8%, the second 6%, and the third 9%. total interest was $3510. the interest from the first investment was 2 times the interest from the second. find the amounts of the three parts of the investment.

[Anonymous No.5707606]

>>5707488
>E =/= MC2
>prove me wrong
Well, that is easy when you're missing the other half of the equation.
It is:<span class="math"> e^2 = m^2c^4 + p^2c^2 [/spoiler] where p is momentum.

If the particle is moving, <span class="math"> p^2c^2 [/spoiler] will be greater than 0, therefore <span class="math"> E \neq mc^2 [/spoiler]

[Anonymous No.5707658]

>>5707606

E = MC2 is not total energy, it's its rest energy, or potential energy in a sense. p^2*c^2 is it's kinetic energy. It's not wrong, you just have no idea what the variables are.

[Anonymous No.5707694]

>>5707179
What are the differences between string theory and loop quantum gravity in terms of prediction?

Which do you prefer?

[Anonymous No.5708034]

are we able to extract helium or use the helium caused bij Alpha radiation

[Anonymous No.5708071]

Can we really become a type 3 civilization as Michio Kaku says? I can't see how humans could harness the power of a galaxy(or black hole?)

What kind of monstrous machines would that require?

[Anonymous No.5708100]

>>5708071

I'm not OP but I assume it would use infinite energy and they would work in an entirely different way than the way we think of energy right now.

[Anonymous No.5708179]

This is shit tier HS physics but hopefully someone can help. The question is about convergent and divergent lenses and mirrors. How can I determine which circumstances call for me to use a negative focal length and magnification? And how can I tell from the measurements whether the image is real or inverted? There seems to be so many different cases for this that it's impossible to memorize and I can't seem to understand the reason behind all of it. any help?

[Anonymous No.5708207]

You're driving a car with the speed of ~ 3x10^8 m/s, you turn on your headlights. What do you see and why?

[Anonymous No.5708210]

Where did the energy come from that created the big bang? Because you know... wasn't there nothing? How did something come from nothing?

[Anonymous No.5708212]

>>5708179

This can be derived using planck's constant, 6.62606957 × 10-34 m2 kg / s, together with W(p * cos X)s, which will give you the means to figure out if the photons hitting the image is coming out as inverted or not.

[Anonymous No.5708222]

>>5708212
I have no idea about any of that, sorry man. I know the image will be inverted if the height of the image is negative, meaning it got reflected below the principle axis. How I have no idea about the focal points and since they change throughout lenses and mirrors there's at least 8 different situations I'm bound to fuck up on

[Anonymous No.5708263]

>>5707179


I went from engineering to applied physics.
The physics dept at our school says that the degree plan is old. Would that really matter?
What kind of job could i get if i double major in applied and math? or if i get a master's in applied?

I'm interested in electromagentics but am somewhat curious about nuclear

[Anonymous No.5708269]

>>5708210

Where does the notion that something have to come from something else come from? It doesn't even help to answer that question, because it will spiral backwards in an infinite loop ("What created the thing that created the thing that created the thing that created the universe" etc).

Our most probable answer to the question though; The concept of beginning/end is just a human fallacy, we cannot imagine how something has existed "forever" and we cannot imagine what truly nothingness is.

[Anonymous No.5708303]

Is it really true that multiple dimensions exists or is it just as real as fairies?

[Anonymous No.5708333]

>>5708303

Well, you're living in at least 3 of them right now.

[Anonymous No.5708339]

>>5708333
Alright, wrong choice of words.

I mean as if there is alternate universes and such.

[metric !1tensorX8Q No.5708381]

Just started learning QFT a couple weeks ago, so pardon the novice question, but why is the <span class="math">i \varepsilon[/spoiler] term in the denominator of the Feynman propagator necessary?

[Anonymous No.5708390]

>>5707179
So, suppose you're dealing with superstrings vibrating in 6 dimensional calabi yau spaces. Now, given the orientation, number of "holes", etc.. the strings will exhibit different properties and become different particles. What would happen if you had a configuration of a calabi yau space so that your superstring in one configuration was a particle of lava and in another configuration a particle of ice and then you collided your lava superstring with your ice superstring?

[Anonymous No.5708394]

Given that there is a finite number (albeit incredibly large) of permutations possible to this reality, that would in turn mean that there is a finite number of alternate realities possible, right?

[Anonymous No.5708403]

>>5708381
Tells you which way the waves go -- towards the future, past, or some combination of both. It's instructive to look at a simpler case: how the <span class="math">i \epsilon[/spoiler] term works when you take the Fourier transform of a Heaviside step function.

[Anonymous No.5708415]

A pole one light year long with infinite rigidity made of hypothetical unbreakable/unchangable material is put in a point in vaccum space, if I were to push one end, would the other end be traveling faster than light assuming that energy transfer is instant.

[Anonymous No.5708442]

>>5708339
There's no way to know, so there's no reason to think that there are infinite universes or whatever

[Anonymous No.5708457]

>>5707179
Is mass 0.99.. or 0.0..001

Serious though, I'd actually like to hear an educated opinion on this

[Anonymous No.5708458]

What's the best introductory text?

[Anonymous No.5708471]

Fucking magnets how do they work

[Anonymous No.5708545]

>>5707388
haha this is exactly what i was just thinking

[Anonymous No.5708567]

Why is it such a big deal that information not be destroyed when matter gets sucked into a black hole?
http://en.wikipedia.org/wiki/Black_hole_information_paradox

[Anonymous No.5708618]

Why is the speed of light what it is?
Why cant light go faster?

[Anonymous No.5708625]

Is the feynman lectures really that good? Thinking about shelling out 100 bucks to get them but I just want to confirm that i'm not gonna get something meh

[Anonymous No.5708648]

>>5708625
They're a good supplement (great in their own right, but no guarantee they'll track your class). Be sure to watch the actual taped lectures. Feynman had some interesting ways of approaching concepts. However, you'll find yourself feeling as if you are following along perfectly with his clear brilliance, only to have a hard time reproducing his though patters when trying to apply his lecture. It can take multiple viewings for things to sink in.

[Anonymous No.5708650]

Who is right, the teacher or the 7yo student?

Looks like the teacher is saying the planets move through space because they move through space.

Kid is saying suns gravity pulls the planets through space.

Pic related

[Anonymous No.5708657]

>>5708650
I would say it's debatable. I read the question as "What motion do the planets illustrate?" rather than "What mechanism causes the planets to move?" so I would be more tempted to agree with the teacher.

[Anonymous No.5708660]

>>5708648
Thanks anon, you've cleared up any doubts.

[Anonymous No.5708680]

>>5708657
Thanks, I will be writing the teacher for an explanation.

[Anonymous No.5708721]

>>5708179
make a diagram. lenses are massively easy if you draw yourself a nice little diagram. bob ross that shit. not op.

[Anonymous No.5708782]

>>5708680

lol why.. why does that matter. just got some points taken away. because he didnt write very detailed

how does the planets move in space.. means in what way or what motion do they move in space.

[CANCER No.5709020]

>>5707463
how? imbalance electron spin?

[Anonymous No.5709030]

>>5707388
this

[Anonymous No.5709042]

>>5707388
nah, physics guy has been here for years. Even if he started out as a lowly undergraduate when he started posting, he would almost done with his doctorate. So basically it is safe to assume he already has a PhD.

[Anonymous No.5709091]

>>5707388
this. Not a single useful answer in this thread.

[Anonymous No.5709148]

>>5707421
haha what? no
hope no one took this seriously

[Anonymous No.5709218]

>>5707232
the visible universe has one but the universe in total is infinite, so its r_s is infinite

[Anonymous No.5709220]

>>5707358
Go learn some functional analysis/measure theory

[Anonymous No.5709221]

>>5707325
wat
https://en.wikipedia.org/wiki/Free_particle

[Anonymous No.5709262]

can black holes be nest

[Anonymous No.5709321]

Why relativity still relevant after this?
>http://www.scientificamerican.com/article.cfm?id=room-temperature-entanglement

[Anonymous No.5709348]

If an atom is mostly empty space, what makes tangible things... tangible?

[Anonymous No.5709350]

What is a black hole?

[Anonymous No.5709355]

>>5709262
For black birds.

[Anonymous No.5709364]

>>5707179
Is a physics major a good idea?
What I am majoring in.

[Anonymous No.5709368]

>>5707179
What created all the laws of physics? What created the law of gravitational and electromagnetic interactions? Why do they interact like they do?

[Anonymous No.5709369]

>>5709368
>What created all the laws of physics?
Jews did.

[Anonymous No.5709925]

I might be derping but i'll shoot anyway.. What if you could somehow shoot mesons trough a blackhole (mesons do not get affected by gravitation right?) wouldn't it be considered information?

[Anonymous No.5709994]

>>5707694
Why no answer to this?

[Anonymous No.5710006]

>>5709925
>mesons do not get affected by gravitation right?
If it's in spacetime, it's affected by gravitation.

[Anonymous No.5710023]

Alright, I'll ask at the risk of being called a faggot.

So if relativity talks about things being either in motion or not relative to different contexts - like if I'm in a car with a constant speed I can drink my coffee with the same ease as being in a stationary office - how do you get from that idea to "E = mc2 + [...]".

Not a physicsfag nor smart but just genuinely interested.

[Anonymous No.5710044]

I have been attempting to calculate a value for the change in magnetic flux with regards to time, (d phi/d t)

Using
Φpk = √2 V /(2π f N)

I have calculated this value for Peak Flux, where V is the voltage going through my coil, f is the frequency at which my alternating current is in changing direction and N is the number of turns on my coil.

Am I right in thinking that this "Peak Flux" is the amplitude of the sinusoidal wave that plots the change in flux?

[Anonymous No.5710067]

why does induction exist

[Anonymous No.5710069]

>>5710023
That velocity is relative was known a long time before Einstein. Special relativity was about how to make that concept consistent with the recently discovered fact that the measured speed of light doesn't depend on the velocity of the device measuring it. This required modifying relativity so that not only are the positions of objects different in different reference frames, but also the times of events. Which implied modifying all the mechanical laws (a very small change except at large velocities) to make them consistent with the new version of relativity.

[Anonymous No.5710070]

>>5710067

nobody knows

[Anonymous No.5710071]

Why does the universe exist?

[Anonymous No.5710073]

>>5709321
Entanglement doesn't violate relativity, just outdated notions of how causality works. There's no way to send a message back in time telling you not to send the message, or other paradoxical nonsense.

[Anonymous No.5710103]

OP ded.

[Anonymous No.5710132]

>>5708650
Personally i would answer "elliptically"; however, seeing as that is not the question the teacher wanted to ask- i would side with the student in this case as he/she provides a more precise answer i.e.- the orbit the sun, because it is pulling on them...

[Anonymous No.5710136]

we've missed you Physics Guy
i thought you were gone for ever

so now to my questions
1. does quantum mechanics work for calculating the probability of past events? does it make sense to have a probability wave function for the past?
2. i've read some time ago on newscientist that measuring the position of a particle by 2 different experiments tends to give different results, the probabilities of measuring the particle were different. so my question is this + entanglement can it lead to FTL information traveling?
3. are wormholes possible? i remember reading something about them not being stable for long enough (smaller than a planks time). also i read something about an equation about them, can we somehow make them stable?
4. why do scientist say that spacetime can't be quantized when the smallest change in position and time are pancks lenght and pancks time?
5. given the photon energy equation and the expansion of the universe, where does the energy lost due to expansion go? or are the photons somehow creating space as they travel? (this would imply that spacetime has energy stored in it)

[Anonymous No.5710154]

>>5707388
This a million times. Even if OP's got a degree in physics it doesn't change the fact that he's being plain fucking unhelpful here, ending every other post with "don't you fucking know that?".

>>5707372
>>5707333
You know perfectly well what that guy meant when talking about 'infinite' or 'closed'. Your answer just looked like a shield for incompetence and lack of knowledge.

Holy fuck, if that's what academia has to offer these days then we're at the edge of the abyss. I swear to god, I've seen that shit every day when I was studying Maths, people specializing in a single field knowing more and more about narrower and narrower subject until they knew everything about nothing - and being a douche about it.

Mad, rustled, called the police.

[Anonymous No.5710261]

>>5710136
Not physics guy, but here it goes.

1.) Past events have already happened so the outcome is not very probabilistic.
2.) If quantum mechanics is not a statistical mechanics of some as yet unknown non-local hidden variables, no.
3.) I don't deal much with GR, but I haven't heard any one saying that they aren't possible, just that they probably aren't out there naturally and that we would need some really FUBARed matter to make them.
3.) Those aren't the smallest change, those are the smallest measurable change given the current state of physics. There being a smallest meaningful measurement is rather different from quantization.
5.) I don't actually know this one. Well, luminosity of very distant objects follows the right relations and so the intensity of the light source is not impacted by expansion. Therefore, in order to compensate, more photons must be "created" in transit. Therefore, the loss of energy of a single photon as a result of redshift would be to making more photons in order to maintain the proper intensity relations. Or at least that is my educated guess.

[Anonymous No.5710284]

>>5710261
what about, is time continuum or discrete?
is it inbound to every particle (relativity) or to the so called space?

[Anonymous No.5710329]

For a spacecraft to decelerate using nuclear pulse propulsion wouldn't it have travel through it's own nuclear blast that it just used to slow down?

[Anonymous No.5710335]

>>5707179
how do scientists answer the homunculus argument? what is watching the picture in my head? electricity can't WATCH the picture the way that something clearly is. so what is WATCHING the picture in my head? ty

[Anonymous No.5710342]

>>5710261
you are wrong Planck's length is the absolute minimum allowed in our universe
read about the Ultraviolet Catastrophe

[Anonymous No.5710349]

>>5710342
>Planck's length is the absolute minimum allowed in our imperfect model of the universe
fixed

[Anonymous No.5710351]

>>5710335
why do you say that something must be watching the picture in your head?
what happens is that the brain makes sense of the information it received in the brain
the brain is you

[Anonymous No.5710355]

>>5710351 samefag
>what happens is that the brain makes sense of the information it received in the brain
what happens is that the brain makes sense of the information it received from the eye

[Anonymous No.5710358]

>>5710351
i honestly can't say if this answer is satisfactory or not. it fills my brain with f@# k to just try and figure if that makes sense. are YOU sure it makes sense? that it really answers the whole question... just curious

[Anonymous No.5710365]

Also not Physics Guy (and we can't be sure the OP is, either, nor is it a good idea to treat namefags or anons on 4chan as trustworthy -- always check things out yourself)

>>5710136
>1. does quantum mechanics work for calculating the probability of past events? does it make sense to have a probability wave function for the past?
If you do things naively, some quantum-mechanical calculations will give you wrong answers if you try to apply them to past events. For example, if I consider a photon that has passed through a half-silvered mirror, and extrapolate the wavefunction backwards in time, I get the nonsensical result that there was a 50% chance of the photon that the photon came from a place where there was no light source. These sort of things illustrate the inadequacy of using a single wavefunction to describe our knowledge of the photon. One way of dealing with the issue is to use both a initial state vector and a final state vector to describe the photon. Another is the consistent histories approach.

>2. i've read some time ago on newscientist that measuring the position of a particle by 2 different experiments tends to give different results, the probabilities of measuring the particle were different. so my question is this + entanglement can it lead to FTL information traveling?
I don't know what article you read, but you can't use entanglement to send someone a message.

>3. are wormholes possible? i remember reading something about them not being stable for long enough (smaller than a planks time). also i read something about an equation about them, can we somehow make them stable?
The Wikipedia article is pretty informative here:
http://en.wikipedia.org/wiki/Wormhole#Raychaudhuri.27s_theorem_and_exotic_matter

[Anonymous No.5710375]

>>5710136
>4. why do scientist say that spacetime can't be quantized when the smallest change in position and time are pancks lenght and pancks time?
The correct statement is that we don't have a theory that combines quantum mechanics with gravity and is valid at all scales. As far as discrete spacetime, the evidence is shaping up against it:
http://arxiv.org/abs/0908.1832

>5. given the photon energy equation and the expansion of the universe, where does the energy lost due to expansion go? or are the photons somehow creating space as they travel? (this would imply that spacetime has energy stored in it)
Energy in GR is not a globally conserved quantity. Only local energy conservation applies. The consequence of local energy conservation applied to cosmology is a relationship between the rate of change of energy and the pressure. The loss of energy due to redshifted light obeys this equation.

[Anonymous No.5710403]

>>5707179
If you're going on how different energy's and masses operate, and not any "hurdurwhatdoestheedgelooklike" bs, how would you see the universe?

[Anonymous No.5710420]

>>5710375
>Energy in GR is not a globally conserved quantity. Only local energy conservation applies. The consequence of local energy conservation applied to cosmology is a relationship between the rate of change of energy and the pressure. The loss of energy due to redshifted light obeys this equation.
what's the definition of a local system then? what about a group of photons are they a local system? does local mean in time?

[Anonymous No.5710448]

>>5710420
The reason there's a global/local distinction comes from how GR works with SR reference frames. In special relativity, once you choose a reference frame, you can apply it anywhere. In general relativity, SR reference frames are only valid as an approximation for things sufficiently close to you. If you extrapolate your reference frame to a distant object so you can speak about its velocity, you'll find that the velocity you get depends on the path along which you extrapolated. Energy is a reference frame dependent quantity, so there's no objective way to even talk about the total energy of the universe; you have to pick a reference frame for every point first. There's a natural way of doing that for cosmology; roughly speaking, use the frame of the nearby galaxies. But a reference frame extrapolated along the trajectory of the photon won't agree with that choice, and it's that reference frame in which the photon's energy will be conserved.

For more about how what I've been calling extrapolation works:
http://en.wikipedia.org/wiki/Parallel_transport
http://torus.math.uiuc.edu/jms/java/dragsphere/

[Anonymous No.5710456]

is there a good place online for physics learning?

khan academy is good for math but not so for other areas

[Anonymous No.5710580]

>>5710448
thanks

[Anonymous No.5710591]

Physics graduate student here:

Can you explain to me how Poisson brackets are used when trying to determine canonical transforms?

[Anonymous No.5710738]

>>5710375
>http://arxiv.org/abs/0908.1832
some scientists say that this may be because spacetime is not perfectly flat at these wavelengths

[Anonymous No.5710752]

What is the spontaneous process that produces life?

[Anonymous No.5710790]

Psychology student here.

Some professors here say that quantum physics proved that you can't approach human behaviour in a deterministic way, kind of what conductism used to do.
I agree that you can't do psychology with a deterministic approach, but I'm not entirely sure about the quantum physics thing.
Are they right?

[Name: Obvious No.5710791]

>>5707179
I have a mass of N atoms per m. cu. with spin S =1 and orbital ang. mom. L = 0. When I apply a field B(vector) the S = 1 moments can align parallel to, 90 degrees to, or antiparallel to Bvector.

Show that by calculating the occupancies of these level that the magnetisation M ia given by

M = 2 N mu_b [2*sinh x / (1 + 2*cosh x)]

and find the average dipole moment in units of mu_b per atom for B = 1 Tesla and T = 10K.

Not homework, before you ask - merely a question a friend of mine posed and we have been struggling over for a while now.

[Anonymous No.5710794]

>>5710752
>spontaneous
no!

you are made out of organs
your organs are made out of different tissues
tissues are made of cells
cells are made of orgnels, proteins and some way to contain protein/genetic information for replication
the proteins are made out of amino acids
amino acids are made of chemical elements (carbon chains)
these chemical elements are made in the nucleus of the stars (the stars then go nova and planets form form the debris)
before the first stars there was only hydrogen and helium (fusion in the star made the higher elements)
hydrogen and helium are made out of electrons protons and neutrons
protons and neutron are made out of quarks
quarks and electrons are elementary particles (well there are theories that say otherwise but it'd be better if we end up here)
those elementary particles and the universe were created with the big bang

[Anonymous No.5710803]

why do all electrons, protons and neutrons exhibit such high uniformity in mass and charge?

how are positrons exactly opposite in charge to an electron?

shouldn't there be variance? even atoms of an element exhibit isotopes.

[Anonymous No.5710848]

Okay, my question is a bit long and drawn out, but I need confirmation about my hypothesis.

If humans built a train that traveled around the earth that went near the speed of light so the relative conversion ratio was 1 week on the train = 1 year outside of the train. And we were powering that train with a type of fuel source, Would the train use 1 years worth of fuel or 1 weeks worth of fuel? And in addition, would the result change if it was on the train or off the train?

[Anonymous No.5710852]

>>5710791
Hello? Anyone?

[Anonymous No.5710870]

The earths mantle is kept warm by a nuclear core. The earth is old and the nuclear fuel cannot last indefinitely. Determine the radius of the earth in a liquid rock stat similar to what existed after the creation of the moon. Also determine the radius of the earth after the mantle has solidified.

[Anonymous No.5710916]

>>5710803
>why do all electrons, protons and neutrons exhibit such high uniformity in mass and charge?
i'm not sure but i think that heavier neutron for example decayed a lot faster, though in nature they do exist but are very rare (i think i read something like this)
the LHC makes heavier neutrons for example (instead if having up down down quarks they have up down strange)

>how are positrons exactly opposite in charge to an electron?
charge is quantized, this means it comes in packets if a certain amount the electron and the positron have the same amount but opposite

>shouldn't there be variance? even atoms of an element exhibit isotopes.
again quantization of charge.
isotopes are not stable and decay, natural decay spews out neutrons some create more isotopes

[Anonymous No.5710932]

>>5710848
acceleration is what matters
to achieve the speed it would require the same amount of fuel no matter the point of reference

[Anonymous No.5712572]

>>5707179
bumpo

[Anonymous No.5712590]

It's been a while since I was in school, but I've had countless physics questions at some point I'm sure, so sorry if I sound uneducated.

First off, as I was taught to understand it, matter and energy are basically different forms of the same thing. E=mc^2 and shit, right?
Well, a friend of mine is currently majoring in something science related and he tells me that matter, when moving at the speed, mimics energy, but does not become it. If this is true,
What exactly does E=mc^2 tell us? I know what it means in the sense of "Energy = mass multiplied by...etc" but if its not essentially a conversion formula, what is it? This also confused me because I was under the impression photons turns out to have mass some time in recent years.

I should probably read more

[Anonymous No.5712593]

>>5710790
Quantum physics put the location/motion of particles as a probability, rather than something you could say for sure. And quantum physics doesn't disprove determinism entirely, only a small section of it. Wiki 'determinism'.

[Anonymous No.5712594]

Can you differentiate the observer effect and uncertainty principle - I always feel like the two get merged together.

[Anonymous No.5712598]

A filamentary conductor carrying current I in the az direction extends along the entire negative z axis. At z=0 it connects to a copper sheet that fills the
x>0,y>0 quadrant of the xy plane. Find H everywhere on the z axis.

[Anonymous No.5712600]

>>5712594
>observer effect
http://simple.wikipedia.org/wiki/Observer_effect#Use_in_science
>UP
uncertainty principle is any of a variety of mathematical inequalities asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle known as complementary variables, such as position x and momentum p, can be known simultaneously.

>>5712590
http://www.energytribune.com/2771/understanding-e-mc2

[Anonymous No.5712605]

Why is the speed limit of the universe the speed limit of the universe.

[Anonymous No.5712618]

>>5712605
Rather, why is 'c' the limit of information propagation of our current universe. It's just called the 'speed of light' because that's how most people are familiar with it and that's how it was tested. There is no 'why'. It just is.
It's akin to asking 'why does the universe exist'.

[Anonymous No.5713205]

>>5708650
Are they seriously asking these kind of questions to kids? It's been a while since i was a kid, but i thought if you were young enough to spell 'through' as 'thraw' then you weren't expected to know what "Infer" means.

[Anonymous No.5713216]

>>5713205
That's not for the kids, that's there to help sell the material to schools. In fact, none of it's really there for the kids.

[Anonymous No.5713219]

>>5713216
Thanks for significantly lowering my faith in public/private schools systems.

[Anonymous No.5713739]

>>5710591
>graduate student
>doesn't even understand first semester undergrad classical mechanics

I sure hope you're trolling.

[Anonymous No.5713743]

>>5713739
>Goldstein
>"first semester undergrad classical mechanics"
0/10

[Anonymous No.5713747]

>>5713743
I don't know who Goldstein is, but Poisson brackets and canonical transforms are taught in any first undergrad classical mechanics course.

[Anonymous No.5713750]

>>5713747
No they aren't.

[Anonymous No.5713756]

>>5713750
Of course they are. Why do you troll?

[Anonymous No.5713760]

>>5713756
If you don't even know who Goldstein is you have no authority on determining curriculum.

[Anonymous No.5713763]

>>5713760
>ad hominem
>appeal to authority

Discussion is over. Your troll failed. Stop embarrassing yourself.

[Anonymous No.5713764]

>>5713763
>Your troll

[Anonymous No.5713766]

>>5713764
Go to >>>/b/ and learn some subtlety. You suck at trolling.

[Anonymous No.5713768]

>>5713763
Not the anon you are arguing with, but I think "If you don't even know who X is you have no authority on determining curriculum." is a valid assertion, valid in the sense of not necessarily correct, but certainly well posed.

I also don't know who goldstein is by the way.

[Anonymous No.5713769]

>>5713766
>You suck at trolling

[Anonymous No.5713771]

>>5713768
It's not a valid assertion, it's inane trolling garbage. I looked up "Goldstein" by now and he seems to be the author of a babby intro book to classical mechanics for undergrad students. There's no reason to know him. Such low level contents don't even require a book.

>>5713769
Seriously, why don't you just stop posting? Your pathetic attempt at trolling failed and now you resort to infantile and pointless greentext quoting.

[Carbon !5XmfGkN7AQ No.5713784]

>>5707179
What is gravity?
How would man control it?

[Anonymous No.5713785]

>>5710261
>1.) Past events have already happened so the outcome is not very probabilistic.

Lol no.

See
http://www.inoa.it/home/azavatta/References/PRL62p2205.pdf

[Anonymous No.5713787]

>>5713771
You don't learn about stuff like the Lagrangian until graduate level classes in America.

[Carbon !5XmfGkN7AQ No.5713792]

>>5707179
So a wormhole is essentially just a black hole with a white hole?

[Anonymous No.5713794]

>>5713787
>in America

I guess there's your problem. If what you said is true, that's very sad. But how do you guys manage to keep up with us even though you're constantly lagging behind 3 years in education?

[Anonymous No.5713818]

>>5713784
Gravity is a nature phenomenon by which physical bodies attract each other.

Gravity can be created artificially by using centrifugal force

[Carbon !5XmfGkN7AQ No.5713833]

>>5713818
What causes that phenomenon? Interactions involving gravitons, tensor field pseudo-dimensions, or is it just a side effect of space time?

[Carbon !5XmfGkN7AQ No.5713836]

>>5713818
Also I mean actually controlling the force...not simulating it.

[Anonymous No.5713864]

Do you get all your answers from wikipedia?

[Anonymous No.5713881]

>>5713818
> Gravity is a nature phenomenon by which physical bodies attract each other.

So electrons orbit protons because of gravity?

You're a fucking moron.

[Anonymous No.5713889]

>>5713833
What we believe is the cause of gravity right now is the curvature of space and the curvature of space is caused by mass. From a quantum field point of view, we expect a particle called the "graviton" to mediate the force of gravity, but no such particles have been experimentally found yet and neither do we have a satisfying theory that accurately predicts them.

[Anonymous No.5713893]

Why are you so fucking retarded? Can physics answer this?

[Anonymous No.5713902]

>>5713881
Why do you think I have precluded other forces such as EM

and by the way, electrons don't orbit protons except in babby tier simplistic models.

[Anonymous No.5713921]

>OP claims to be a knowledgable physicist
>dismisses all higher level questions as "too stupid"
>only answers babby level questions with wikipedia links

Into the trash it goes!

[Carbon !5XmfGkN7AQ No.5713932]

>>5713889
Doesn't gravity also influence time? It is said that at the core of a black hole time moves at an exponentially small rate...to the point wher it is essentially frozen.

[Anonymous No.5714120]

>>5713932
actually near the event horizon edge things should just go exponentially slow, so that you'll never see the thing falling inside
it would seem like it's frozen in time at the edge, and even if you wait for billions of years you won't see it cross the edge (at least in theory and that if i got it right)

[Anonymous No.5714131]

When they speak of a valence cloud of electrons around the nucleus of an atom, do they mean that the electrons are actually just spinning around the atom at speeds so fast that it's just easier to refer to them as a cloud, or are they actually a cloud that can only be described in terms of hard quantum physics shit that nobody understands except for a handful of professors?

[Anonymous No.5714152]

>>5714131
>are they actually a cloud that can only be described in terms of hard quantum physics shit that nobody understands except for a handful of professors
You learn this in grade 11 or 12 if your education system is retarded.
http://en.wikipedia.org/wiki/Atomic_orbital

[Anonymous No.5714181]

Is the legit Physics Guy, i.e. the guy that worked at CERN?

[Anonymous No.5714186]

>>5714181
Apparently not. It's just another shitposting troll trying to impersonate him.

[Anonymous No.5714188]

>>5714186
figured.

[Anonymous No.5714218]

>>5714186
SAGE is shit posting
it doesn't matter if OP is the Physics Guy as long as he gives educated answers

[Anonymous No.5714263]

>>5714218
>as long as he gives educated answers

[Anonymous No.5714267]

>>5714218
>condescending reply
>link to wikipedia

>Educated answers

[Anonymous No.5714280]

>>5714267
there is only one question directly answered with a wikipedia link

and quoting your source of information is not shit posting

[Carbon !5XmfGkN7AQ No.5714451]

>>5714218
SAGE is shit posting
>babbys first chan

[Anonymous No.5714559]

>>5714218
>as long as he gives educated answers

Unfortunately he didn't.