/sci/ - Science & Math

[Physics Guy No.3146946]

Taking physics questions (if they aren't too fucking stupid).

Any takers?

[Anonymous No.3146953]

>>3146946
What is the term that goes to infinity that we define as dark matter?

[Anonymous No.3146960]

Why does the electron emission in the absence of light increase as the temperature of a photomultiplier is decreased?

[Anon No.3146965]

How to you make a homopolar motor, into a homopolor generator that creates more energy than is used from the battery?

[Anonymous No.3146967]

What's the best introductory physics textbook if I forgot high school physics?

[Anonymous No.3146968]

What causes the emission of short bursts of light from imploding bubbles in a liquid when excited by sound?

[Anonymous No.3146983]

This is high school level physics
if the mass of one proton was totally converted into energy, the yield would be?
First, wtf is yield?

[Anonymous No.3146984]

Is it possible for an atom to release no more than a single photon of light when an electron transitions to another energy level? Has this ever been detected or is it possible to detect?

[rimz !!mP/3/9/BIcp No.3146996]

why is physics so fucking counter intuitive and if it says in quantum theory that an atom can disappear upon observation (shrodinger's cat) then why is it we never ever observe something vanishing?

[Anonymous No.3147002]

What's the viability of the hypothesis extended from M theory, that states that "dark matter" is simply gravity leaking across to our universe from another brain?
I know, I know
>String theory
But it does seem quite convenient.

[Anonymous No.3147008]

>>3146965
Hello Nicholas Bogdan

[Physics Guy No.3147011]

>>3146965
>creates more energy than is used from the battery

No

>>3146984
Yes, yes

>>3146983
They are just asking for the rest mass of a proton

[Anonymous No.3147018]

>>3146996
>it says in quantum theory that an atom can disappear upon observation (shrodinger's cat)
I can answer that for you, stop getting all of your information from Through the wormhole and actually research it yourself

[Physics Guy No.3147021]

>>3147011
By rest mass, I meant in units of energy. Most physicist speak of mass and energy as the same fucking thing.

[rimz !!mP/3/9/BIcp No.3147029]

>>3147018

can't you just explain it to meee?

[Physics Guy No.3147031]

>>3146996
>it says in quantum theory that an atom can disappear upon observation (shrodinger's cat)

No. You have wrong information kid.

[Anonymous No.3147032]

>>3146984
That's how lazers works bro

[Anonymous No.3147039]

Hey Physics Guy, what is the best introductory physics book/textbook that you know of?

[rimz !!mP/3/9/BIcp No.3147043]

>>3147031

Give me correct knowledge?

[Anonymous No.3147045]

Was this post you?

http://green-oval.net/cgi-board.pl/sci/thread/2946827#p2947115

[Anonymous No.3147048]

>>3146983
ok wait i think i answered my own question.
since Energy and Mass are equivalent, the yield would be the difference between energy and the mass of a proton
using the equation E=mc2,

[Physics Guy No.3147054]

>>3147002
>>What's the viability of the hypothesis....M-theory...

There is no viability of the hypothesis. M-theory and string theory aren't even considered proper science.

[Anonymous No.3147060]

>>3147048
ok no i was wrong
>>3147011
you are right. thanks

[Anonymous No.3147062]

If you make a robot run around in a circle, where does all the kinetic energy go? I thought all energy was preserved?

[Anonymous No.3147065]

why is it a problem if certain observer can see wrong sequence of events if looking at something that travels faster than light?

[Me No.3147068]

>>3147008
Hello

[Physics Guy No.3147080]

>>3146967
>>3147039
This is the one I usually use

[Anonymous No.3147084]

>>3147080
THANK YOU!

[Me No.3147087]

>>3147011
So then why would you ever want to make a Faraday wheel or a dynamo if all homopolar generators are doomed to give an output that is less than the input?

[Anonymous No.3147088]

>>3147062
> I thought all energy was preserved?
No, only total energy. The kinetic energy is becoming heat.

[Anonymous No.3147092]

>>3147087
... to convert between mechanical and electrical power?

[Physics Guy No.3147097]

>>3147065
Such a transformation takes you out of the Poincare group.

[Anonymous No.3147104]

>>3146946
Op, here's one: I've always been dumb in physics, and I've been wondering; how can electrical charge go through acid? Wouldn't the H+ - ions just go to the Cathode & then go together with another H and disappear as gas?

[Anonymous No.3147106]

If time and light are related (correct me if I'm wrong on that one), and black holes are places where not even light can escape from, would it be possible to use black holes for some form of time travel?

[Physics Guy No.3147107]

>>3147087
"to convert between mechanical and electrical power"...DURRRRRR

>>3147092

[Anonymous No.3147108]

>>3147062
>All energy was preserved
Only in a completely closed system(Impossible to create)
In an open system kinetic energy is transferred to heat at all points of friction(e.g.robot an the floor, all of the joins and moving parts within the robot)

[Anonymous No.3147109]

People often cite quantum mechanics as examples of events with no cause. Is this only labeling events we can't *find* causes for as therefore uncaused, and committing a fallacy?

[Physics Guy No.3147126]

>>3147106
Probably not in the way you are thinking.
FYI: Any objects in relative motions are undergoing "time travel", as each clock is ticking at a different pace. Same shit happens to objects in black wholes, ie; huge time distortion.

[Anonymous No.3147127]

If the Higgs-Boson isn't found in the CERN experiement, how will we redefine everything we know about physics and its standard model?

Also, is nuclear fusion on the horizon within the next twenty years or so and would it be a good time to get into the field for an undergraduate going into a graduate program?

[Anonymous No.3147129]

>>3147104
Charge can go through any ionic solution, and yes that does happen. I remember in GCSE chemistry my teacher did an example by running a current through an aqueous solution of table salt. It started releasing chlorine gas.
That was a fun day....

[Anonymous No.3147130]

>>3147107
,... that BS and you know it, a homopolar motor takes electrical energy transferrers and it into mechanical, however when this idea is used to make a generator it then becomes a homopolar generator, variations of this are the Faraday wheel and the dynamo, so once more i say WTF?!? Is there a way to add in a second physical energy source that is in addition to the electrical energy imputed to make a higher electrical output?

[Anonymous No.3147136]

>>3147126
Well, I was thinking of something along the lines of sending a text message to the past.

Would that be somehow possible?

[Anonymous No.3147149]

>>3147136
The movie Deja Vu did it.

[Physics Guy No.3147152]

>>3147109
>committing a fallacy

Nope. You seem to have a very narrow view of causal and non-causal structures. You are probably so skewed by your would-view that you may never be able to understand it, sorry. It isn't your fault though, you just need to develop your critical thinking skills more.

There is a big difference between having a "cause" that we just don't know, and a non-causal system. We know the difference between the two, and how to figure out which type of system is which.

[Physics Guy No.3147156]

>>3147136
no

[Anonymous No.3147173]

[noko No.3147175]

so how do magnets work?

[Anonymous No.3147181]

>>3147045
You see, the reason I ask is that you said things like

>I have direct acces to the data and all internal memos.

But I thought you were at CMS. And then you posted a search of public collections only with no hits, as if that meant anything.

(For people who don't know, that unreviewed, unchecked leaked result turned out to be wrong; the Higgs has not been found yet.)

[Anonymous No.3147182]

>>3147175
"noko" goes in the e-mail field, Mr. Summerfag.

[Anonymous No.3147183]

>>3147152
>Nope.

This is not the way I think. I'm trying to figure out what QM actually has to do with the matter... because I have no idea.

I'm asking if QM (as is relevant to the debate I alluded to earlier) shows us a non-causal system, or a system with a cause we are unaware of...

[noko No.3147198]

>>3147182

dude are you easy to troll

[Anonymous No.3147200]

>>3147198
>Jokes on them, I was only pretending to be a fucking retard

[Anonymous No.3147201]

>>3147198
>>>/b/

[Anonymous No.3147207]

>>3147200

dude if you srsly respond like this to guys who put noko in the name or subject field, you for sure are a summerfag or a very stupid person

[noko No.3147210]

Does god exist?

[Anonymous No.3147212]

>>3147198
>>>/b/

[Anonymous No.3147214]

>>3147198

[The Doctor No.3147215]

What do you think of the Holographic Principle?

[Anonymous No.3147218]

So, how advanced is actual particle physics? Like, do I really have to wait until graduate school? What kind of math do you need to really get it?

[Anonymous No.3147219]

Explain coral castle.

[Anonymous No.3147227]

>>3147198
Nice one summerfag

[noko No.3147234]

>3147227
}implying blah blah whatever

[Anonymous No.3147239]

>>3147129
>Charge can go through any ionic solution
Many thanks, but WHY can charge go through any ionic solution?

[Anonymous No.3147241]

>>3147219
block and tackle
http://www.peter-thomson.co.uk/coralcastle/coralcastle.html

[Anonymous No.3147257]

So, the universe is infinite. How come people keep talking about the size of the universe? Is it the visible universe they are talking about?

[Anonymous No.3147264]

>>3147257
Either that or they have no clue what they're talking about.

However, it's possible that the universe has finite volume, yet no center or edges (by wrapping around on itself, like the surface of a sphere). But it could just as easily be infinite, and it is certainly much larger than the visible universe.

[Anonymous No.3147271]

teh earth is flat !

[Anonymous No.3147278]

>>3146996
well. the chance that an atom vanishes at one point just out of nowhere is extremely low. now if, lets say you want a rock to disappear, that's gonna be quite a few billion atoms. and the chance that all those billion vanish at once is extremely fucking ridiculously low.

[Anonymous No.3147284]

>>3147239
Because ionic compounds do no have single molecules like covalent compounds, rather it is one big lattice of + and - ions arranged in order. So when they become dissolved in solution, they dissociate into their respective ions. e.g. NaCl(s) becomes Na+(aq) + Cl-(aq)

[Anonymous No.3147301]

>>3147241

what about the perfectly balanced door?

[Anonymous No.3147319]

If the Higgs Boson is found, and you can remove it from an object, how would an object with no mass be different from a normal object? what would be the implications of removing the mass from an object?

[Anonymous No.3147324]

What is time? I know it's not our measurement of time. Is time simply the word we use for change in the universe?

Because I view the world as if everything is happening at once. It's all this same "moment". There's just change in this single moment. Have you ever experienced the past or future? They are simply changes made to your brain in the present.

[Anonymous No.3147325]

>>3147264
The wrapping was Einsteins prediction, right?
Also, some people say the visible universe is limited because objects outside of it move away from us at a speed greater than light (0,6c + 0,6c or something along those lines). However, i was under the impression that this is impossible because of time dilation and so on. I was thinking we just can't see that far.

[Anonymous No.3147328]

Why do you trust Jewish physics?

[Physics Guy No.3147331]

>>3147183
>I'm asking if QM shows us a non-causal system, or a system with a cause we are unaware of...

You don't seem to understand what QM is. QM is a tool, it is a set of procedures and rules (like all physics). Like all physics, it can exist abstractly as a set of tools. If applied properly to the physical universe, QM provides excellent explanitory and predictive power (hence it is a science).

The nature of basic QM itself is not non-causal, it is non-deterministic. It is the universe that is non-causal. It is the direct observations that lead us to see that certain system of the universe are non-causal, not QM. The actual mathematics and physics used to help model these systems is way beyond the basic QM, you end up dealing with QFT. You could say that QFT allows for some non-casual systems, of which we observe all the fucking time.

Again, there is a difference between a non-causal and an unknown cause. We know the difference, and how to expect either case. We know the universe ends up with non-causal behavior.

I think you are overreach your thinking ability here. You really need more fundamental/basic physics knowledge to try and understand the more advanced concepts. You wouldn't expect to learn Calculus without knowing how to Add, would you?

[Anonymous No.3147336]

How come WTC 7 fell, even though it wasn't hit by a plane?

"Hot stuff fell in the general vicinity of it lol" is not an acceptable answer.

[Josef !!nUf2NflSAyw No.3147341]

>>3147331
>It is the universe that is non-causal.
>You could say that QFT allows for some non-casual systems
Excuse me?

[Anonymous No.3147347]

>>3147325

it doesn't work that way buddy. 0,6c+0,6c=1,0c.
no linear addition for velocities.

[Anonymous No.3147358]

>>3147319
No.
Just... no.

[Anonymous No.3147374]

>>3147331
>You don't seem to understand what QM is.

Off your high horse, sir. I do understand this. That's why I said "QM shows us x system" instead of "QM is x system".

>It is the direct observations that lead us to see that certain system of the universe are non-causal, not QM.

Thank you. This is what I'm trying to discern... the source of the idea often cited in debates. I'm obviously not presenting this as my own argument. Now, you still haven't actually explained how we know the difference between non-causal and unknown cause, and additionally, how we know that the universe presents non-causal behavior. I'd like to know.

[Anonymous No.3147379]

>>3147347
Well, no, not at those speeds. That was why i was asking.

[Anonymous No.3147382]

>>3147341
Shit just got real

[Anonymous No.3147386]

>>3147358
This is a purely theoretical question, much like a hypothetical FTL question. We do not know if mass behaves this way, nor do we know if this object exists. My question is based on three assumptions: 1) the object exists 2) the object behaves as expected 3) the object can be artifically removed from the object, or lessened in effect.

[Physics Guy No.3147394]

>>3147319
>Higgs Boson.....remove it from an object

I don't think you understand the Higgs at all. The Higgs is not the Quanta of mass. The Higgs doesn't physically provide mass that way. Every massive object, does not have a Higgs in it.

It is way more fucking complcated then that. The Higgs is just a remanent of a greater physical structure. In order to remove the mass of an object, it would require reverting to that greater structure, which in turn involves producing falue vaccum levels and all sorts of crazy shit.

[Anonymous No.3147397]

>>3147386
Pressed submit too fast. Meant to add: 'I am asking what the current mathematical modules would imply were an object's mass reduced to naught'.

[Anonymous No.3147402]

>>3147379
but even if the universe only moves at 1.0c, you won't be able to see the edge, because it's too fast. once you see it, it's already a whole bunch larger and has changed.

Inteersting physics fact#1: Forwards time travel is possible. Time dilatation will bend time if you move fast enough( >80%c.) This way, if you move at this speed for a while, a longer while will have taken place outside of your system(spaceship)

[Physics Guy No.3147407]

>>3147341
Vacuum fluxuations are a non-casual system.

[Anonymous No.3147414]

Are there REALLY such things as magnetic monopoles? I was taught that they were impossible in intro physics, but I'm seeing a lot of articles claiming they exist.

[Josef !!nUf2NflSAyw No.3147420]

>>3147407
I find that hard to believe. (And I've tried messing with causality a few times already. Didn't work. Where's T symmetry when you need it)
Well, maybe I'll understand it some day

[Anonymous No.3147422]

Explain me the event horizon.

[Anonymous No.3147429]

>>3147394
I am simply going off what other people told me. It is probably faulty, given your reaction.
Is there a more proper way to phrase a question regarding the possibility of the reduction of mass?

As a CS/EE student, my knowledge of physics is limited to making electricity move in pretty patterns and basic mechanics.

[Physics Guy No.3147441]

Derp

[Anonymous No.3147443]

>>3147414
There are theories that postulate them, but no one's found any yet (not counting irreproducible results).

There are also pseudoparticles that behave like monopoles that emerge in certain condensed-matter systems (I'd have to look it up) but those aren't real monopoles, only apparent. There are magnetic flux tubes running between opposite-charged pairs.

[Anonymous No.3147449]

>>3147422
Event horizon is the area where the force of gravity in a black hole is almost strong enough to create an escape velocity of almost C. beyond the event horizon, the force of gravity is so high that v(escape) >c. this is possible because escape velocity is not an actual velocity, but the velocity that would be NEEDED for matter to escape. Explanation enough=?

[Anonymous No.3147452]

>>3147407
What exactly is meant by non-causal?
And surely there are examples from non-relativistic QM as well. What are those?

[Physics Guy No.3147459]

>>3147374
>haven't actually explained how we know the difference between non-causal and unknown cause

Of course not, I don't think you are capable of understanding such yet, you don't seem to have the proper prerec's. Let's start smaller, and guide you there.

First do you know the difference between a deterministic and non-deterministic (probabalistic) system?

Do you know how a prob system is proven to be truly prob, and not just us not us not accounting for something?

These are basic physics concepts of QM, you need to understand, before we go any further.

[Anonymous No.3147468]

>>3147422
Nobody knows what it really is, but one of the assumptions says that it's the part of a black hole where nothing can escape from and where time takes over the role of space.

[Anonymous No.3147473]

Is it possible to purposefuly quantum entangle a pair of objects?

[Anonymous No.3147474]

>>3147459
>Do you know how a prob system is proven to be truly prob, and not just us not us not accounting for something?
The fuck? Any probabilistic system can be simulated by a non-probabilistic system. Pseudo-random number generators, have you heard of them? Also Bohmian mechanics/field theory.

[The Doctor No.3147482]

1. What do you think of the Holographic Principle, M theory not withstanding?

2. I have heard that antiparticles travel through time in the opposite direction. Just how speculative is this?

3. I suppose that if a massy object was to travel at C, infinite mass would result. Like a black hole? Supposing it could happen at all.

4. Further upon black holes. Suppose a black hole was formed in the LHC. Would it even matter since it wouldn't weigh more than its constituent particles.

5. Gonna stop before I hurt myself.

[Anonymous No.3147485]

>>3147468
That's an feature of the Schwarzschild coordinate system, not actual physics.

[Anonymous No.3147497]

>>3147449
How is the escape of a particle even possible amongst such high gravity?

[Anonymous No.3147511]

>>3147482
Please answer this guy's questions they are awesome.

[Anonymous No.3147517]

>>3147422
The event horizon is a surface that's moving outward at the speed of light relative to any massive object at that location. Nothing can escape it, since that would mean moving faster than light.

[Anonymous No.3147537]

>>3147482
1. No idea, haven't heard of this.
2. That is probably bullshit, just as the antigravity theory that has been denied.
3. it does not happen unless it gets infinite energy. and where does it get infinite energy? nowhere. shit's not gonna happen.
4. If it were to be a REAL black hole, we would all be fucked. but everything is just gonna be a lot of mass on a small dot, yet not sufficient or stable enough to acutally suck up our planet.
5. hope your head doen's 'splode.

[Anonymous No.3147558]

>>3147497
it is not. that is the point of a black hole. a black hole is black because the velocity needed to escape from it is greater than the speed of light. no particle and no photon can ever escape this.

[Physics Guy No.3147563]

>>3147420
Yes, it is often hard for some to deal with, but it is true. The problem is actually in your phil reasoning and not your scientific reasoning. You made some assumptions you shouldn't have made. Re-evaluate!

Particles "pop" and "disappear" from existence all the time, and vacuum flux is an undisputed fact of nature (we observe that shit all the time as well).

Don't confuse a non-causal system, as that of complete chaos though. We still have physics (probabalistic), mathematical models, symmetries, certain conservations,....etc.

Just because something has no "initial cause", doesn't mean it cannot be studied, catagorized, predicted, and even experimenally verified. Science can still be done!

[Anonymous No.3147569]

Will nuclear fusion be attainable in the next twenty to thirty years?

[Anonymous No.3147584]

>>3147569
it has been attained already. but it is not effective as a source of energy, as the prerequisites require lots of energy, and no stable solution to contain the plasma has yet been brought to work for industrial use

[Physics Guy No.3147586]

>>3147474
>Any probabilistic system can be simulated by a non-probabilistic system

Nope

http://en.wikipedia.org/wiki/Bell's_theorem

Do you see know, how ill-prepared you really are?

[Anonymous No.3147605]

>>3147586
I suspected that was what you were thinking of. Looks like you're the ill-prepared one here. Bell's theorem has *nothing* to do with the determinism vs. probabilistic issue. That is just a common misconception.

[Anonymous No.3147616]

So the center of a black hole has infinite density, which would require a finite number of it's mass to exist in 0 space...so how does that work?

[Anonymous No.3147618]

>>3147045
>>3147181
Are you going to respond to this?

[Anonymous No.3147625]

>>3147584
Perhaps I should have rephrased the question. Is sustained nuclear fusion by humans obtainable in the next twenty to thirty years?

[Anonymous No.3147629]

>>3147459
>First do you know the difference between a deterministic and non-deterministic (probabalistic) system?

My layman's understanding would lead me to believe that both systems are predictable, yet one is predictably random.

>Do you know how a prob system is proven to be truly prob, and not just us not us not accounting for something?

No. Is it explainable in layman's terms?

[Anonymous No.3147641]

>>3147625
well. that's what research is for. i don't believe it's going to happen anytime soon, but we all know what bill gates said "640K(ram)ought to be enough for anybody." and look what we have now. 8GB RAM upwards...

[Anonymous No.3147642]

What's the probability of a single UV photon causing cancer?

[MerseyRed !8lVOWRN7t. No.3147657]

Has there been any steps forward to understand how the observer effect works with the double slit experiment? (Electrons acting like particles when we look at them, then acting like waves when we don't)

[Anonymous No.3147673]

Would Cauchy stress in 2D be represented as a 2x2 tensor?

[Physics Guy No.3147688]

>>3147482
1) Ehh, its a neat thing to think about that, but uttterly pointless right now

2) This is true, we actually use that shit in calculations all the time, it is basically what you get if you directly interpret the mathematics used. Feynman was a huge proponent of these beliefs. Most physicist are fine with this, although there are still a few who "deny it".

3)
>Suppose _random fairytale bullshit_ what happens?

Massive things can't don't move at c (in the manner you talk about). You are talking about fairytales, like Santa Clause or god, not science.

4) A blackhole formed at the LHC would disintergrate very rapidly.

5) Huh?

[Anonymous No.3147693]

>>3147657
no need to further understand this. Understanding really is not a part of modern physics anymore...
It is explained by using the model that any piece of matter can be described as a particle AND as a wave.
This is defined by the De-Broglie wavelength. You could theoretically do the doubleslit experiment with a brick and get the same results.

[Anonymous No.3147727]

>>3147657
maybe an easier example. the slit experiment can of course also be done with light. if you use a laser, and you lower the intensity so it "fires" 1 photon at a time, you will still get the characteristic image i posted.
The image i used was done with single slit, but the results are essentially the same.


BTW physicsguy, where did you get this knowledge. All that i'm posting is advanced german high-school level.

[Anonymous No.3147734]

I know that waves oscillate back and forth, my question is, why do particles in a wave oscillate instead of going straight?

[Anonymous No.3147763]

>>3147734

What do you mean by "particles in a wave"?

[Physics Guy No.3147770]

>>3147657
>observer effect

It is just wave-function collapse. Anything that causes a collapse of a particular measurable is an observer. An "observer" need not be human, it could be a rock, or anything really.

>wave-particle duality

The fundamental objects in the universe are fields (wave like properties). Certain excitations and particular happenings of a field, cause an "excitation", which we view as a particle.

[Anonymous No.3147771]

>>3147763

I assume he means quanta

[Anonymous No.3147789]

>>3147771

I thought he meant, for example, the individual atoms of a vibrating string

[Anonymous No.3147814]

>>3147763
>>3147771
>>3147789
I mean that in a light wave, said particle would be a photon. ect.

[Anonymous No.3147825]

>>3147814
The particle doesn't oscillate. The relationship between particles and waves is a bit more complicated than that.

[Anonymous No.3147837]

since quantum mechanics states that anything is possible, is it possible that quantum mechanics behaves how it should IE, the infamous double slit experiment, can quantum mechanics behave the way we want it to behave so we can finally achieve unification?

[Physics Guy No.3147838]

>>3147825
>>3147789
>>3147814
>>3147771
see
>>3147770

[Anonymous No.3147852]

>>3147838
answer my question.
where'd you acquire your knowledge? just basic college phyiscs? high school even? or more advanced shit?

[Anonymous No.3147855]

>>3147814

Photons do travel straight. (actually, in the Riemannian spaces of general relativity, the ds=0 path followed by light is a way to *define* straightness)

What's oscillating is the electromagnetic field associated with the photon.

[Anonymous No.3147864]

>>3147837
wat.

[Anonymous No.3147869]

>>3147814

>since quantum mechanics states that anything is possible

Not even close to true.

[Physics Guy No.3147947]

>>3147852
University, reading books, and working in Labs. Right now I am working at the LHC.

[ႼЋïŁႣƧტƿḩЄƦṥ !Scone2booQ No.3147972]

>>3147947
>Right now I am working at the LHC.
Doing what? What is your position?

[Anonymous No.3147977]

Why does Schrödinger's cat die nearly every time when you look at it?

[Anonymous No.3147989]

>>3147972
he keeps the birds from dropping bread on the power supply with a giant net.

[Anonymous No.3148006]

>>3147977
Because you forgot to put air holes in the box.

[Physics Guy No.3148010]

>>3147972
I work on the CMS, on a particular sub-detector. Gathering data, checking data, running equipment, just the standard shit people do at the LHC. I am an active member of a few research teams, etc.

Don't really wanna give too much info away.....

[Colonel Coffee Mug !phJ7yIcs.Q No.3148015]

Hey Physics Guy, is there are validity to Entropic Gravity, or am I just going full pop-sci? Half-pop-sci? How pop-sci?

Have a nice wallpaper in return.

[Anonymous No.3148028]

>>3147947
That's awesome. What do you do at the LHC actually? I mean, i know what the field of research is, but what do YOU actually do there?

[Anonymous No.3148067]

>>3148010
is that because we could find your info due to your field of research etc, or is there research "stealing" you want to avoid?

[Anonymous No.3148076]

>>3148010
>Don't really wanna give too much info away.....
I smell a conspiracy.

Or more like, I want to believe in one because it would make life a bit more interesting.

What, is CERN doing some top-secret research on time travel and when they succeed they're gonna use it to turn the world into a dystopia where everything is controlled by them?

[Anonymous No.3148079]

What's the accepted definition of time in physics? Ive been told its the duration between two events. But that's circular reasoning.

[Anonymous No.3148082]

>>3148076
why would you want to turn the world into a dystopia? that's fucking retarded, man...
>>3148028
nvm. answered above.

[Anonymous No.3148086]

>>3148076
>>3148067
That, or he doesn't want anyone to know he goes on fucking 4chan you idiots

[Physics Guy No.3148103]

>>3148015
> validity to Entropic Gravity

Nope.
There are hundreds of "neat" ideas about gravity, entropic gravity is just one of many. Right now, it is not a validated inquiry of science. It has very few supporters (only those with a stake in it), and hasn't yet proved itself as a correct form of reasoning.

It may turn out to be true, just like any other of those hundreds of ideas could be true. But until it actually is produces signifigant results and predictions, it is a waste of time in general. You cannot give crediance to all the crazy ideas out there, that would be fucking retarded (and is not scientific reasoning).

[Anonymous No.3148109]

>>3148010
You don't happen to have any good contacts to ALICE people, do you?

[Anonymous No.3148111]

>>3148086
going on 4chan isn't too bad. i only browse /sci/, /g/ and /tv/. stopped going on /b/ a long time ago...

[Anonymous No.3148113]

>>3148006
Lets pretend the box is holey as standard.

Why does Schrödinger's cat die nearly every time when you look at it?

[Anonymous No.3148120]

>>3148086
Why must you go for the choice with the least fun potential?

I'd like to believe Physics Guys is part of a top secret team that does conspiracy shit like sending kittens through black holes or observing the effects of prolonged exposure to Gaga music to the human brain.

[ႼЋïŁႣƧტƿḩЄƦṥ !Scone2booQ No.3148123]

>>3148010
Are you an intern? Do you have a degree?

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148125]

>>3147126
It's called phenomena not time travel. As time only exists, As a form of measurement in the minds of thinking creations.

[Anonymous No.3148133]

>>3148082
I never said I want the world to become a dystopia.
I just want some big events to happen in my lifetime.
That's why despite being a man of science, I want to believe that something intriguing will happen 2012, even though I know that all of those predictions are bullshit.
>>3148086
Chill, I'm just fucking around.

[Anonymous No.3148134]

>>3148015

It fails to correctly predict the behaviour of slow neutrons under gravity, so it's either straight up incorrect, or needs considerable tweaking.

See, for example, http://arxiv.org/abs/arXiv:1009.5414 subsequently published in the physical review.

[ႼЋïŁႣƧტƿḩЄƦṥ !Scone2booQ No.3148136]

>>3148113
It dies half the time. What are you talking about?

[Dr. White !!/zv2MTbpUH9 No.3148141]

Is there any evidence towards the idea that the speed of light changes given the size of the universe or the local gravity?

I once read a book about this by one Joao Magueijo

[Anonymous No.3148151]

>>3148136
thats what I thought but another person I know from CERN who teaches me this stuff says it dies nearly every time when you look at it. I don't get it.

[Anonymous No.3148156]

>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
>>3148079
ANSWER ME.

[Dr. White !!/zv2MTbpUH9 No.3148159]

>>3148151
What did someone run an experiment about this?

It's probably because the sample material is so large that there's always something decaying, setting off the detector/poison

[Anonymous No.3148160]

>>3148141
Most of the references in the popular media to searches for changes in the speed of light are actually searches for changes in the fine structure constant. None of those have turned up anything as far as I know.

[Anonymous No.3148170]

>>3148113

It doesn't. In the standard formulation there's a single atom unstable to beta decay, which is somehow linked to a cat-killing machine, so that the cat dies in the event of decay.
The probability of the cat being dead when you open the box depends on the length of time for which you leave the cat in the box relative to the decaying atom's half-life.

[Physics Guy No.3148173]

>>3148076
>CERN doing some top-secret research on time travel

I wish. I imagine we will do some time travel research one day, but not anytime soon, and it won't be secret.

It would be impossible to keep time travel research secret like that, cause it would end up being so fucking costly, and energy consuming. Also, the size of our (initial) time travel equipment would make the LHC look small in comparision. Shit would take decades, if not a century, to build (at least).

Most of humanity is not yet ready for that kinda science.

[Dr. White !!/zv2MTbpUH9 No.3148175]

>>3148079
I'd figure time is just another coordinate axis comparable to the xyz coordinate system. The function of our movement through the t axis would be govern by general relativity.

[Dr. White !!/zv2MTbpUH9 No.3148187]

>>3148173
Also because anyone working on it would come to /sci/ to talk about it.

[Anonymous No.3148195]

>>3148173
Are you assuming that the most plausible way of getting time travel is the exotic matter + general relativity route?

[Anonymous No.3148197]

>>3148160
Err.. I thought there was some paper on this. They looked at some far-ass galaxy and concluded that alpha was different then ours is now.. can't remember the name of the article though.

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148200]

>>3148173
Time travel doesn't exist. What humans think of time travel is in all actuality multidimensional travel within a multiverse framework. As there can not be only 1 universe constantly expanding alone. For all things have polarity.

[Anonymous No.3148202]

>>3148170
yeah there is no explanation for what was said to me. i got trolled perhaps

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148206]

>this thread praising its stone age physics bullshit lol

[Anonymous No.3148207]

Can you explain the whole speed of light thing? Speed relative to what, everything, all at once? I don't understand this part. If it propagates through space like anything else, what gives? Wouldn't you say light was stationary if there was nothing else in the space it was moving through, as it's propagating at a constant speed?

[Dr. White !!/zv2MTbpUH9 No.3148229]

>>3148207
Speed relative to everything. It's exactly the same no matter what reference frame you have.

>if there was nothing else in the space
Was that Mach who said something like that?

[Anonymous No.3148233]

Question:

The coupling of the top quark to the Higgs is ~1 (top mass is 172GeV, Higgs v.e.v is 174GeV).
For the neutrino the coupling is tiny, but this can be accomadated quite nicely with the seesaw mechanism.
However, the electron coupling is ~3 orders of magnitude smaller than the top coupling.
What could account for such a range of fermion couplings to the Higgs?

[Anonymous No.3148234]

>>3148200
>>3148206
who are you to know this? raptor jebus from the future?

[Anonymous No.3148239]

>>3148229
i think mach said angular momentum required that other matter exists in space

[Dr. White !!/zv2MTbpUH9 No.3148241]

>>3148200
>>3148206
Continue to believe this, unwashed masses! Everything is under control by us.

[Anonymous No.3148243]

>>3148234
John Titor.

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148248]

>>3148207
The speed of light is humanities current blockade of speed. For they can not construct megalithic super structures for which to create quarks via nano construction methods to open a wormhole destination atm.

[Anonymous No.3148268]

>>3148248
now get out.

[Anonymous No.3148269]

>>3148248

you come back from the future and the first thing you do is come on 4chan?

ALL PRAISE VIRGIN NECKBEARD OF THE FUTUTRE!

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148288]

>>3148269
>>3148268

[Anonymous No.3148289]

>>3148233
Not OP, but aren't the Higgs couplings theoretically adjusted to exactly fit the current standard model?

I don't think there is an actual explanation as to why the couplings are this way, that would've made big news I guess...

[Anonymous No.3148305]

Hey OP, what's the deal with this possible new particle they picked up over at the Tevatron? Any inside talk about it, or implications of something like they think they picked up?

[Dr. White !!/zv2MTbpUH9 No.3148314]

>>3148305

Wasn't that something about the chromatic force? What's that all about?

[Physics Guy No.3148320]

>>3148079
Time is a fundamental scalar "coordiante" of the configuration space we observe (like positions). Durations can be taken of this coordinate (if need be).

The unique thing about time (as opposed to the other coordinates) it is "non-negative current flow". This is easily explained by the Minokowski like metric, in which time is essentially the imaginary conterpart of space. Hence for all practicle purposes, time is often regarded as "imaginary space" .

The only way to give meaning to imaginary values, is for "norms to be taken", thereby cementing the fact that time will always appear to flow "forward" (generally).

Fundementally, the "generator" of time is "energy", just as the generator of space is momentum (and visa versa depending on your observation system).

[Dr. White !!/zv2MTbpUH9 No.3148334]

>>3148320
Is that why the energy momentum tensor is part of the General Relativity equation?

[Anonymous No.3148340]

>>3148289

Yep, they're put in by hand to fit the measured masses.
My question was about what ideas there are about where they actually come from.

Another interesting thing: the quark weak mixing matrix is damn close to diagonal, whereas the leptonic mixing matrix is not even close.
I know there's no answer to this currently, but it seems to be a question that isn't even asked very much.

[Anonymous No.3148345]

>>3148320
>The only way to give meaning to imaginary values, is for "norms to be taken",

puremathsfag here. not convinced, why is this so? surely there are examples in physics where i and -i both have valid interpretations.

[Dr. White !!/zv2MTbpUH9 No.3148365]

>>3148345
If you are asking about the singular direction of time, I've come up with an analogy that makes sense to me.

Imagine time is like a necklace with each bead being a moment. You can't move any bead backwards because it would bump into the one right behind it. In order to do so (And for time travel to occur, possibly) would be to move the bead in two dimensions, off of the one dimensional string.

But since time, as far as we know, is one dimensional, you can't have it flowing in anything other than one direction.

[Physics Guy No.3148372]

>>3148305
The CDF peak (indicative of a new particle) has pretty much been ruled out by most. It ended up being a flaw in the data analysis method, or some werid shit like that (many papers produced on this already).

Until someone can reproduce it (which no one has been able to do), it is thought of just as experimental error, and of little, if no importance (besides telling us how to not produce such errors in the future)

[Anonymous No.3148376]

>>3148365
>nonsense talk

gtfo so physics guy can answer my question

[Anonymous No.3148378]

>>3147537
You don't know shit.
2 is the accepted model for antiparticles, since the actions are the same both forward and backward in time.
4 If a black hole does form, it wouldn't pose a threat due to radiation.

[Josef !!nUf2NflSAyw No.3148382]

>>3148320 Time is a scalar ("coordinate") of the configuration space
Time's a number. A scalar is, practically speaking, invariant under transformations. The coordinate part is true of course.

[Dr. White !!/zv2MTbpUH9 No.3148384]

>>3148376
>Implying if I throw my bullshit ideas out he can't answer your question

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148389]

>>3148320
Time does in fact have polarity in which it flows negatively. Example a person standing next to the pyramid, Time will move slightly slower than a person 50 miles out in the open desert with nothing around. Density controls the micro measurements of time in which still is a active phenomena only in the minds of thinking creations.

(USER WAS BANNED FOR THIS POST)

[Anonymous No.3148395]

>>3148389
Do we have a mod around to deal with this shit head?

[Anonymous No.3148400]

LQG or M-Theroy?

[Dr. White !!/zv2MTbpUH9 No.3148405]

>>3148389
Time is in fact the subjective self realization of sub-antithetical cognition.

It is our minds processing of the quantum consciousness existing in all life forms and within the fabric of the universe!

[Anonymous No.3148415]

>>3148389

4 CORNERS OF THE TIME CUBE

[Physics Guy No.3148416]

>>3148345
>surely there are examples in physics where i and -i both have valid interpretations

Interpretations in terms of the "math" or the "undelying physics" maybe. But as far as "observation", and "experimentation", they are indistinguishable.

We cannot observe imaginary values in any way, shape or form. i and -i, will produce the same observation.

FYI: I have a degree in pure math as well

[sage No.3148426]

What could possibly be at the center of a neutron star?

[suicidalmathmajor No.3148429]

>>3148426

Not that I was trying to sage this thread. Best in a long long time.

[Anonymous No.3148432]

ITT: Guy with no knowledge, but Google, is acting like an intellectual authority.

[Anonymous No.3148435]

>>3148395
The best way to deal with a troll is to ignore him. All he is doing is seeking your attention, don't give it to him.

[Dr. White !!/zv2MTbpUH9 No.3148439]

>>3148435
Yea, that Illuminati guy is pretty annoying.

[Anonymous No.3148457]

Actually the illuminati guy is pretty smart. He has a interesting input. And is welcomed in /sci/

[Physics Guy No.3148462]

>>3148426
Probably some weird states of quark matter.

That is usually what forms when you compress alot of matter into a very small space (before the black hole limit).

[Dr. White !!/zv2MTbpUH9 No.3148467]

>>3148462
So the stuff right after electron degenerate matter but right before neutron degenerate matter?

[Dr. White !!/zv2MTbpUH9 No.3148471]

>>3148457
Shut up illumicorp

[Anonymous No.3148476]

>>3148416
plenty of other similar symmetries exist, but are not interpreted in the way you propose. that is, if a symmetry exists, we consider its "norm" only.

are these your own ideas? i don't see them elsewhere after a little searching

[Anonymous No.3148482]

>>3148471
I think you're way more annoying than ILLUMICORP. Please just leave.

[Anonymous No.3148486]

>>3148207

[Anonymous No.3148488]

>>3148482

[Vicarious !!cEGdAHjF6OB No.3148496]

Why is it that bikers feel like they've got a headwind even when they don't?

[Anonymous No.3148499]

>>3148476
The thing hinges on how quantum mechanics works. When you calculate something in QM, lets for simplicity say a wavefunction, to get the probability distribution which is what you can measure, the theory tells you to take the square of the norm. Thus i and -i will always give the same answer. Also when calculating more relevant stuff, i.e. scattering amplitudes/matrix elements, to get the actual cross section you need to take the square of the norm.

[ILLUMICORP !ELkrV.qD7I!!g0XnOr645KD No.3148503]

>>3148496
Psychosomatics.

[Anonymous No.3148525]

>>3148372
link to said papers?

[Anonymous No.3148540]

>>3148499
we were talking i and -i being interchangeable - and how time is imaginary in minkowski space - could explain time's arrow.

i think it's a hand waving argument myself.

that equations will be equivalent in both directions is not the same as saying there is only one direction.

[Physics Guy No.3148557]

>>3148476
Not my ideas buddy. The idea of time as imaginary space is pretty common. It can be found in most QFT books, and most books that use Minoskski metric. It is embedded in the choice of your metric tensor.

>if a symmetry exists, we consider its "norm" only

I never said that, nor did I imply that? What symmetery are you even refering to?

What I said was, "the only way to observe an imaginary quantity is to take a norm". You seem to be confusing this with the whole symmetry discussion? why? The symmetry discussion was on the generation of time from a fundamental level (using lie groups), not the observation of time.

I think you are confusing concepts guy.

[Anonymous No.3148571]

>>3147239
Because any ions can convey the charge.
I didn't complete highschool and I know this.

[Anonymous No.3148581]

why do people who think that they are really smart, are in fact complete and total retards?
why is /sci/ filled with these people?
why does /sci/ worship people like deities while claiming to be atheist?
why are you all brainwashed, groupthink, hypocritical faggots?

[Anonymous No.3148582]

>>3148557
of course imaginary time isn't your idea, i'm not 12yrs old, but as an explanation for times arrow it seems to be. would like sources if not.

we are referring to the i and -i symmetry.

[Anonymous No.3148597]

>>3148540
You got that out of >>3148320 ?
To me it sounded like a bunch of technobabble with a few factoids thrown in here and there about Minkowski space and Lie groups to make it sound plausible.

[Elen !!w5CHYddUvhS No.3148600]

Okay, OP. I have a real serious question. Please consider it carefully, because it's kind of complicated.

I was reading Carl Sagan's Cosmos, and he talked about the big bang not being all of the universe's matter exploding out of one corner of it, as I had previously imagined it, but rather as the universe itself expanding, the space itself expanding. I envisioned a 6-dimensional hypersphere, where the 3 dimensions of space are squeezed into the surface.

Then, just today, I suddenly realized that, if the volume of this hypersphere were increasing at an even or low-exponential rate, the rate of expansion of the hypersphere's radius would actually be *de*celerating. And it hit me: objects in the three dimensional "shell" of the universe would be "pressed" into the fabric by momentum, resulting in curvature... and GRAVITY!

(Picture related.)

I'm not sure why Carl Sagan didn't explain it like this. Is this not a preferred model? I looked around on Wikipedia, and this seems to be what I'm referring to – the FLRW metric (http://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metri
c).

Is this how the FLRW metric visualizes the universe? As an expanding 6-dimensional hypersphere? Or am I totally misunderstanding everything about spacetime and gravitation? Feel free to call me stupid if I am.

(For reference, I'm interested because I'm going to be going to college to major in physics and math, and I want to get a graduate degree in astrophysics at some point, so I'll be working with all this stuff one day.)

Also for reference, the circle in my diagram represents a six-dimensional hypersphere. The radius of the circle is the fourth dimension, its width as a circle is the fifth, and its thickness as a sphere is the sixth. The three euclidean dimensions are represented as a flat plane, stretched like a tarp over the surface of the sphere, and expanding uniformly in all directions.

[Dr. White !!/zv2MTbpUH9 No.3148601]

>>3148581
Dunning–Kruger effect

[Anonymous No.3148611]

>>3148601
samefagging again old chap?

[Anonymous No.3148613]

>>3148597
>>3148597
well yeah, i was trying to show that as usual physics guy is full of shit, so picked up on the algebraic equivalence of i and -i implying time's arrow nonsense.

[Anonymous No.3148614]

>>3148600
>babby's first idea

[Physics Guy No.3148615]

>>3148540
It is nice to see ya'll interested in such concepts. It isn't really hand-waving though, you can actually develop proofs and such if you want. I have seen a few, here and there.

You really need a good grasp of abstract fundamental physics (group theory, cal of var, least action, notherm theorm, etc) to understand that shit though.

[Anonymous No.3148620]

>>3148615
i call bullshit

cite or stfu

[Dr. White !!/zv2MTbpUH9 No.3148623]

>>3148611
Actually, I've been doing what >>3148482 said. I'm just watching this thread now.

[Anonymous No.3148630]

>>3148615
>makes up idea
>can't justify it
>says it's too hard for us to understand

[Physics Guy No.3148641]

>>3148600
>Carl Sagan's Cosmos

Stopped reading. Pop-science is not science. Anything you think you "know" from pop science is probably wrong. It was probably presented wrong, and you probably interpreted what they were trying to tell you wrong. IT IS SHIT!

Also, If you have questions, just ask them succinctly, I don't need your whole life story bro. I won't even bother reading all your post, sorry.

[Anonymous No.3148642]

>>3148601
yes but people read that and still think it doesn't apply to them
I know it applies to me, therefore I am not a retard

[Anonymous No.3148644]

>>3148615
Well, I have a good grasp of those things, and so presumably do some others in this thread, so why don't you explain what you were trying to say.

[Anonymous No.3148648]

What's a good book to study up on tensor mathematics?

[Anonymous No.3148654]

>>3148630
entropy, CPT, or wave collapse are good candidate reasons that time has direction (except wave collapse)

imaginary time as a reason is just stoner talk

[Elen !!w5CHYddUvhS No.3148662]

>>3148641
>Stopped reading. Pop-science is not science. Anything you think you "know" from pop science is probably wrong. It was probably presented wrong, and you probably interpreted what they were trying to tell you wrong. IT IS SHIT!

What the fuck. Carl Sagan wasn't some fake scientist. He made his living in astrophysics and cosmology. When he presents a model, he does his best to represent it faithfully. In fact, his representation of the expansion of the universe *goes against* the popular conception of it by insisting that it was the space itself which expanded and not the matter which exploded.

You're being unfairly judgemental of the man.

>Also, If you have questions, just ask them succinctly, I don't need your whole life story bro. I won't even bother reading all your post, sorry.

I didn't post my whole fucking life story. You're clearly a sham, and just don't want to examine a real cosmological question. I should never have thought anyone on /sci/ could answer my questions. I'll just have to wait until fall, so I can ask a real fucking professor. And if he doesn't know, I'll ask him who might.

Go back to /b/, you child.

[Anonymous No.3148669]

>>3148644
This is typical physics guy. If I had a nickel for every time he dodges a difficult question by saying:

>"the math is over you head, so here's a picture of a scientist laughing at you"

Did you know, he is the only person on this board that has taken a math class past calculus? It's true, just ask him.

I don't doubt he is a physicist, but he starts these threads to sit on a high horse, and pretend he has a better understanding of maths than anyone here. He won't answer questions that allow others to call him on his bs. nb4 hatersgonnahate.jpg

[Anonymous No.3148682]

therticly, cud u cros a embrio witha shrume an mak pieple tht ar alwaz hi?

[Physics Guy No.3148684]

>>3148620
inb4 you keep asking for more proof and you are never satisfied, no matter what.

If you want to go through the argument, I am more then happy to help you bro, but you need to be familar with a bunch of concepts before we can proceed. First of all do you understand the Minsowksi metric?

The first step is to show that it is an Euclidean metric with "time being imaginary space". This known as the Wick rotation. Do you know what a Eucldiean metric is?

http://en.wikipedia.org/wiki/Wick_rotation

You following? How familiar are you with physics? These concepts so far?

[Anonymous No.3148687]

>>3148669
totally, bet this fag has never opened a discrete maths book
calculus is highschool level math

[Physics Guy No.3148695]

>>3148662
Dude, stop overreacting, ask our question pal. No one is stopping you, so? Question? (don't post a whole fucking page!)

[Anonymous No.3148701]

i have pictures of my entire physics final that im taking tomorrow. wanna do it for me?

[Physics Guy No.3148713]

>>3148701
>i have pictures of my entire physics final

How did you get them? We can discuss them if you want, but I'm not gonna do extensive calculations for you/

[Anonymous No.3148714]

>>3148684
I'm familiar with all that. Were you trying to get a justification for the arrow of time out of that, or did whoever first mentioned that misinterpret your post?

[Anonymous No.3148730]

>>3148695

I do believe he was just asking if what he was imagining was close to the present model or completely distant from it... the image looked kinda cool imo.

However since you're asking for questions: what's your opinion on Alcubierre drive?

[Elen !!w5CHYddUvhS No.3148735]

>>3148695

Just open the image I posted with my original question (>>3148600).

Tell me how badly inaccurate a model of the universe's expansion it is, OR if it roughly resembles an existing model in any way, and in what ways it is poorly representative of the model it resembles.

For reference, the circle in the picture represents a six-dimensional hypersphere: the radius represents the fourth dimension, its width as a circle represents the fifth, and its thickness as a sphere represents the sixth. The three euclidean dimensions are represented as a flat plane, stretched over the surface like a tarp, and expanding uniformly in all directions.

[Anonymous No.3148766]

>>3148713
its really easy stuff, but our class was nuts and didnt learn anything..

theres one question that states that you have 2 identical sized cubes of different metals, one of which has a specific heat 3.5 times the other one. theyre both placed into identical styrofoam cups (of negligible heat capacity) with identical amounts of water at the same temperature. The question asks after equilibrium is attained, which one has a higher temp?

[Anonymous No.3148773]

Question on Tensors.

The thing I'm reading concludes Einstien's Tensor Convention with the expression

<span class="math"> a^s= a_j * a^(js)[/spoiler]

Where g is the fundamental tensor and a is the scalar component of a unit tensor

I don't understand how they come about this identity. They say it's an exercise for the reader. Brilliant

[Anonymous No.3148795]

When I was studying tensors, they concluded the section on Einstein Summation Convention with the identity

<span class="math"> a^s= a_j g^js[/spoiler] where a is the scalar component of the axis s or j, and g is the fundamental tensor. The subscript and superscript represent contravariant and covarient tensors naturally.

[Physics Guy No.3148800]

>>3148714
That just tell us that time is fundamentally imaginary, if we attempt to view it as we do our other coordinates in configuration spaces.

Next, you try to define a time operator using our operator theory, QM and QFT, making sure it is hermitian (so we can get it to correspond to reality).

The only way to to this is through something analgous to a norm. There is no other way to map the imaginary space to the actual values we observe which is consistant with QFT, and approximates to QM is the approperate limits.

You still following? Need me to clarify something?

[Anonymous No.3148802]

>>3148795
My question is how do they derive this identity? They say it's an exercise for the reader. Brilliant.

[Anonymous No.3148805]

>>3148600
>I was reading Carl Sagan's Cosmos, and he talked about the big bang not being all of the universe's matter exploding out of one corner of it, as I had previously imagined it, but rather as the universe itself expanding, the space itself expanding. I envisioned a 6-dimensional hypersphere, where the 3 dimensions of space are squeezed into the surface.

Why 6 dimensions? You only need 4 to have a hypersphere with a 3-dimensional surface.

It is possible to visualize the FLRW metric this way, but only in the case of a closed universe. Right now, measurements are consistent with a flat universe.

>Then, just today, I suddenly realized that, if the volume of this hypersphere were increasing at an even or low-exponential rate, the rate of expansion of the hypersphere's radius would actually be *de*celerating.

In that visualization, the volume inside the hypersphere doesn't have any physical significance. The extra dimension you add to curve 3D space into a hypersphere isn't real; it's just helps you imagine it.

>And it hit me: objects in the three dimensional "shell" of the universe would be "pressed" into the fabric by momentum, resulting in curvature... and GRAVITY!

The pictures you see of dents in a fabric only illustrate one aspect of spacetime curvature, and it's not the part that makes apples fall to the ground.

>(Picture related.)

>I'm not sure why Carl Sagan didn't explain it like this.

Because what you described is not at all like standard general relativity or any alternate candidate theory of gravitation I'm aware of.

[Anonymous No.3148831]

>>3148800
From what I understand time operators don't work in quantum mechanics. And in QFT, we don't restore Lorentz invariance by making time an operator; we do it by making the spatial variables parameters of which the field operators are functions.

>The only way to to this is through something analgous to a norm.
You have a link explaining this?

[Anonymous No.3148847]

>>3148831
>You have a link explaining this?
Or more generally, a reference?

[Elen !!w5CHYddUvhS No.3148855]

>>3148805
>Why 6 dimensions? You only need 4 to have a hypersphere with a 3-dimensional surface.

Because left-right and forward-backward would be curved over the surface of the sphere, and therefore not equivalent to north-south or east-west in the context of the hypersphere. The difference between left-right and east-west would be imperceptable on a micro level, and only noticeable when considering large sections of the sphere.

>The pictures you see of dents in a fabric only illustrate one aspect of spacetime curvature, and it's not the part that makes apples fall to the ground.

I understand that. I'm just representing it using the same analogy, applied over more dimensions, I guess. Falling bodies appear to move in parabolic arcs because the straight lines of their movement in four dimensions, translated into three, experience noticeable distortion.

>Because what you described is not at all like standard general relativity or any alternate candidate theory of gravitation I'm aware of.

Alright. I was just wondering, because the visualization seemed so explanatory. I didn't expect it to be accurate, mainly because I lack significant experience with cosmology and relativistic physics, but also because I simply hadn't ever seen it explained this way, which led me to assume no physicists would find this visualization accurate.

Thanks, though.

[Anonymous No.3148876]

>>3148662
lol u mad

[Physics Guy No.3148919]

>>3148735
Sorry bro, but your model/ideas are not consistant with anything we have ever observed.
It is in no way similar to the model we use for the expansion of space or any model we use for ANYTHING!

GR with the FLRW metric is 4-d (3 spatial, 1 temporal), it works pretty fucking well, and explains and predicts most cosmological phenomina.

Why are you introducing all these extra dimensions? What is the point? What does it accomplish? 4d is all we need.

I'm sure its a neat idea, but that is all it is. And there are hundreds of similar neat ideas out there. No one pays much attention to them, cause they are a fucking waste of time (until they actually produce some results!)

I imagine you got such nonsense from Pop-science. A lot of times pop-science will show all these fucking useless "fringe theories" and pass them off as "standard science".

[Elen !!w5CHYddUvhS No.3148947]

>>3148919
>I imagine you got such nonsense from Pop-science. A lot of times pop-science will show all these fucking useless "fringe theories" and pass them off as "standard science".

No. I did not. I came up with the idea myself, based on an image that popped into my head when I read Carl Sagan's description of how the expansion of the universe actually happened.

So blame me, not Sagan. He didn't do anything wrong. I take full responsibility for this idea, and acknowledge that it was a mistaken impression. Because that's what a good scientist should do.

A good scientist should also not be a condescending prick, like you are.

[Anonymous No.3148976]

>>3148947
are you still mad?

[Anonymous No.3148986]

>>3148947
>A good scientist should also be a condescending prick, like you are.
*fix'd

[Anonymous No.3148997]

>>3148831
>>3148831
Nope. I understand what you are saying, and there were some problems when they initially tried to make a time operator, but it is not the case anymore.

http://www.sciencedirect.com/science/article/pii/S0003491606002363

[Anonymous No.3149029]

1) I saw earlier this days this video:
http://www.youtube.com/watch?v=7ImvlS8PLIo
At 51:00 he says:" All the galaxies will move away from us faster then the speed of light. It's allowed in general relativity." How come is this possible?

2) From what I understand from relativity I concluded this, please tell me if I'm wrong:
- the speed of light cannot be crossed because faster speeds cannot be measured or observed, but that doesn't mean they cannot happen (relative speed between two electrons or other particles that are closing on each other with a speed close to that of speed of light is higher to that of speed of light)

- if the speed of light can be crossed, the theory of relativity is not valid because the barrier of speed of light is axiomatic in this theory

- I think of an analogy between sound propagation and light propagation to explain the constant and barrier of the speed. As with sound, once it's out of the source it propagates from point to point no matter what the speed the source was, only the medium where it propagates has effect on the speed. That doesn't mean one cannot measure that two sound waves are traveling towards each other with twice the speed of sound. The same as for light but in this case it cannot be measured.

I would be very glad if you answered my questions because I hadn't got a chance to talk on this subject with someone who really knows this stuff (that includes university physics teachers). And please excuse my english.

[Anonymous No.3149033]

>>3148947
Are you new here?

[Anonymous No.3149044]

>>3149029
Not physics guy, but

1) the space itself is expanding, the object doesn't need to be moving through space at all, even for it to be "moving" away from another object faster than the speed of light.

[Physics Guy No.3149049]

>>3149029
The light speed limit only applies for inertial frames of reference (Special relativity). The light speed limit does not apply in general, non-inertial frames of reference (General relativity).

I have no idea why or how you were misinformed.

[Anonymous No.3149059]

>>3148795
>>3148802
Anyone?

[Physics Guy No.3149075]

>>3149059
It follows directly from what "g" actually is representing. It is the change of one coordinate system, with respect to the other, remember?

[Physics Guy No.3149077]

>>3149075
That and the produce rule.

[Anonymous No.3149121]

>>3148997
Thanks for the link. Although it's not too surprising to me that people have figured out how to make a time operator.

The article doesn't seem to be consistent with what Physics Guy was saying at all, though:
>Next, you try to define a time operator using our operator theory, QM and QFT, making sure it is hermitian

In the article they say there is a no-go argument that prohibits you from constructing a Hermitian time operator, so they describe some tricks with POVMs (I haven't read it all).

And don't see anything that leads to a better understanding of the arrow of time, if that's what Physics Guy was referring to.

[Anonymous No.3149128]

If atoms move in predictable, set patterns then how do we have free will?

[Anonymous No.3149138]

>>3149128
How about they don't, and we don't?

[Anonymous No.3149167]

>>3149075
>>3149077
What? This isn't true at all. g is the metric, not a coordinate transform, and when you write <span class="math">a^j=g^{ji}a_i[/spoiler] you use the metric as a map from a covariant vector (covector) to a contravariant vector. You can prove it by using the linearity of tensors and how the definition of a covector acting on a vector is related to the metric, but often it's taken as a definition.

[Anonymous No.3150778]

So you hate popsci huh? Are there any programs or documentaries that explain science in layman's terms that you don't hate? Anything /remotely/ accurate out there?

[Anonymous No.3151077]

I've been wondering this for a while and can't seem to find anything about it anywhere on the internet. Has there ever been any research done into the theory that, long ago when the sun was cooler, Venus contained earth-like life? And conversely in the future when the sun heats up and ends life on earth, that mars will emerge from its embryonic state to host its own life?

Sort of explains life, the universe, the afterlife, and everything if ya think about it. lulz

[Anonymous No.3151108]

>>3151077

I'm more concerned with Earth's magnetic field weakening and solar winds blowing off our atmosphere

[The Doctor No.3151215]

>>3149128
Think very carefully about what predictability means.