Questions for the physicists

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Anonymous

Questions for the physicists 2016-01-25 22:46:10 Post No. 7810589

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Questions for the physicists 2016-01-25 22:46:10 Post No. 7810589

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So due to the theory of special relativity, the speed of light in vacuum, c ~= 3x10^8 m/s is the fastest speed possible, but emitted photons do not accelerate up to that speed right? It's just an instantaneous electromagnetic wave. I know that photons can be affected by gravity which gives them acceleration ( change direction of velocity), but I'm talking about when an excited electron returns to its ground state by emitting a photon, the photon just appears i to existence already going at the speed of light. Is this correct?

What is the difference between the cyclo/synchrotron and particle accelerators like the LHC?

What is the highest %age of c that humans have been able to accelerate a massive particle to?

Is there a limit to acceleration in the universe like the limit of c for speed? Is it possible to accelerate a particle at 3x10^9 m/s^2 for 0.09 s to get it to 0.9c?Or even at arbitrarily larger accelerations than that for even smaller time intervals?

What would be the limit to acceleration? The magnitude of the force and so the energy needed to create that force?

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Too many questions.

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Nobody? I tried to formulate some good questions I had, what's wrong with them? If people didn't know either I thought it would at least start some discussion, but not even one legit reply?

This board must not be /sci/ence but /frogs, trite memes, pseudoscience, philosophy and 0.999...=/=1 and IQ de(baits)/.

>>7811147

gee, thanks for your input you could have at least answered one of them

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>>7810589

>I know that photons can be affected by gravity which gives them acceleration

I thought the mass of protons is so insignificant that they aren't affected by gravity. It's only the space that gravity affects, in which the photon travels, and not the photon itself.

Anyways, can't really answer you questions. But I like the cats you are posting so here's a free bump.

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>>7811959

>I thought the mass of protons is so insignificant that they aren't affected by gravity. It's only the space that gravity affects, in which the photon travels, and not the photon itself.

Yeah but isn't moving through curved spacetime equivalent to accelerating towards the object that causes the curvature? Like it's a fictitious gravitational force causing the "acceleration" but that doesn't change anything about the acceleration itself.

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>>7810589

>but emitted photons do not accelerate up to that speed right? It's just an instantaneous electromagnetic wave.

I could be wrong, but I don't think anyone knows that for a fact. At this point it's philosophical.

Personally I believe that we exist in an ocean of tiny-ass particles and that photons are just excitations of this ocean. Hence we can avoid the idea of a particle being created and then accelerated to the speed of light. It's like waves on a lake. The speed of the wave is constant and depends on the properties of the lake.

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>>7812059

>The speed of the wave is constant and depends on the properties of the lake.

That's what I was saying. Whe you drop a rock into a pond the waves do not accelerate up to their propagation speed. A wave's speed is constant in a specific medium from the time of the origination event.

But, you could say that in a change of medium the velocity changes, like in reflection or refraction of light, and a change in velocity is acceleration, but again it seems like an "instantaneous" change in velocity, is the change in velocity over some actual existent time interval? Because if the time taken is 0, the acceleration would approach infinity in magnitude

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>>7812130

>change in velocity over some actual existent time interval? Because if the time taken is 0, the acceleration would approach infinity in magnitude

Also what do you guys think about the quantization of time? Wouldn't having a smallest possible "unit" of time make intuitive sense. But I guess the thing is would it be useful and make sense in the context of modern physics theory

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>>7811959

>I like the cats you are posting

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I think the first question is interesting. I had always visualised the speed to be instantaneous, now, I dont know.

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>>7811959

>It's only the space that gravity affects, in which the photon travels, and not the photon itself.

That is the same thing. Gravity is the warping of spacetime.

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>>7810589

>>7813244

Well, [math]\Delta E= \frac {hc} {\lambda} [/math] where delta E is change in energy, h is Planck's constant, and [math]\lambda[/math] is wavelength. Energy is always conserved, so the amount of energy spent is defined as: [math]E_n = -hcR_\infty \frac {Z^2} {n^2} [/math] where R sub infinity is the Ryberg constant, Z is the atomic number of the particle, and n is the principal quantum number (electron shell number). So the change in that, which is [math]E_n = -hcR_\infty \frac {Z^2} {n_0^2} - E_n = -hcR_\infty \frac {Z^2} {n_f^2} =hv[/math], (where v:=c/lambda), so divide that change by h and you have the velocity of the emitted photon. This happens instantaneously, to answer your first question.

I will kill myself and livestream if that latex doesn't compile.

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>>7813465

Well I have to retype it anyway since I copied and pasted without thinking. "So the change in that, which is..." [math]\Delta E_n=-hcR_\infty \frac {Z^2} {n_0^2} + hcR_\infty \frac {Z^2} {n_f^2} = hv \iff v= \frac {\Delta E_n=-hcR_\infty \frac {Z^2} {n_0^2} + hcR_\infty \frac {Z^2} {n_f^2}} {h} [/math]

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>>7812059

>I could be wrong, but I don't think anyone knows that for a fact. At this point it's philosophical.

You are wrong. This is not a philosophical problem.

>Personally I believe...

Personally I think you've not done any graduate work in quantum field theory so your interpretation is misinformed

>>7812149

>Also what do you guys think about the quantization of time? Wouldn't having a smallest possible "unit" of time make intuitive sense.

No more sense than a quantization of length (what some people confuse for the planck length). Space-time is a manifold so I don't see how quantizing distances would work. I think the point it to quantize the gravitational effects from that manifold, which is to quantize curvature.

Though I have never studied quantum gravity and neither has anyone in this thread.

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Photons have infinite acceleration yet constant velocity

Isn't it crazy?

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>>7813600

>Photons have infinite acceleration yet constant velocity

>Isn't it crazy?

It would be crazy if it weren't wrong

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>>7813603

>change velocity from 0 to c instaneneously, therefore infinite acceleration

>travel at c constantly

Absolutely right

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>>7813611

You clearly do not understand what is going on. The photon is never at the speed 0 because it does not exist at all before it is emitted. Energy is imparted in an instant into the electromagnetic field, and as such causes a wave to propagate at c that very instant. There is no energy or wave before it begins propagating.

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>>7813634

Not relevant. Everybody knows that anyways

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>>7813473

Also, h~6.62607004*10-34 and [math]R_\infty \sim 1.09737315685955*10^7[/math] and h can be canceled out in that last expression there. So [math]v=\Delta E = cZ^2R_\infty( \frac {1} {n_f^2} - \frac {1} {n_0^2} )[/math] Formally written, [math] \frac {1} {\lambda} = R_\infty ( \frac {1} {n_0^2} - \frac {1} {n_f^2} )[/math]

The only reason I'm repeatedly correcting myself is to bump this.

Also, >>7813600 & >>7813611 look at that formula up there, also I'm pretty sure I'm butchering notation with that change in change [math] a=\frac {\Delta v} {\Delta t} = \frac {\Delta( \Delta E)} {\Delta t} [/math] which you can interpret two ways: either you could see that it must be 0 since E changes only once, or you could be a complete dumb ass and somehow turn this philosophical.

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>>7813634

completely different process that involves coupling to quanta of vibrational atomic motion

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>>7813473

put \displaystyle first in there,

makes the fractions nice and big

[math] \displaystyle \Delta E_n=-hcR_\infty \frac {Z^2} {n_0^2} + hcR_\infty \frac {Z^2} {n_f^2} = hv \iff v= \frac { \Delta E_n=-hcR_\infty \frac {Z^2} {n_0^2} + hcR_\infty \frac {Z^2} {n_f^2}} {h} [/math]

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>>7813637

In regards to your last line there as you put it, now consider that t and e are intersecting on anything but right angles, at which point does the entropy of t is deflecting e into an internalizing fractal as they pass by eachother and t is interpreted as a polygon of the with a system of irrationals that e is presenting that are exponentiating as t passes through its boarders, and the regulators of t at this point are e from t in its previous rendition identifying with e in the present concoction.

And that's energy in a nutshell.

See, doesn't have to get all philosophical

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>>7813667

Was anything you said supposed to make any sense at all?

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>>7813649

protip: displaystyle also sizes your parenthesis so they fit properly

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post more cats

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>>7810589

The transition isn't instantaneous. It goes smoothly from a quantum state where you have zero probability of finding a photon if you measure to a state where you have a probability of nearly 1 of finding a photon. But if any point you measured and found a photon, its speed would be c.

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>>7813877

So how long does it take for an electron to move down an energy level?

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>>7813896

Depends on the transition.

Here's a calculation of 2p -> 1s for a hydrogen atom:

http://farside.ph.utexas.edu/teaching/qmech/Quantum/node122.html

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>>7813877

incorrect

>>7813896

>>7813932

They calculated the mean lifetime. That means the expected time the electron spends in that state before transitioning is whatever. That does not mean it takes that long to transition.

Transitions are instantaneous. That is a basic facet of quantum mechanics that you would know if you ever took a class on it.

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>>7813959

>the atom randomly instantaneously transitions between states

No, mate. It's unitary evolution until you measure it.

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>>7813994

>unitary evolution

Meaningless

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>>7814037

Kek, are you the same person accusing me of not having taken a class on QM?

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>>7813848

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>>7813848

kittycats

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>>7813959

>>7813877

OK this is OP, thanks for the replies and arguments, I think this stuff is interesting to think about, I only took physics 1 and 2, really liked E&M, I'm in biochemistry. I want to take intro to quantum and special relativity eventually and just trying to think about physics ideas a little in the meantime.

Another thing I've read about spacetime is that light moves through the three spatial dimensions at c and at 0 through time, so all other massive particles must always be moving through time because they will never reach c in the spatial dimensions.

So wouldn't the question be not whether the photon is generated instantaneously, because it never moves through the time dimension, so it would be in the truest sense instantaneous, but how does the electron drop down an energy level, with the change in orbital shape (probability density), while coupled to photon release, which is instantaneous? Or am I misunderstanding something?

Does an instantaneous change for a probability density make sense? It doesn't make sense to me if the electron is thought to have a fully particle character, but what if it becomes full wave character at that moment?

So, can the electron's drop in energy to ground state be fully instantaneous, or if it's not, how is it coupled to photon release which is instantaneous?

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>>7815367

when you look up at the black cat it really does look like that. I have a black cat, I know.

Post more some more cats.

to answer the post: I'm not a physicist but I've studied it quite a bit. let me just put this whole topic into perspective:

in sprint running (sport) you have something called a false start: a runner starts before the gun goes off and gets disqualified for it.

now, there was a guy in the 1996 Olympics who happened to do that. actually, he had a habit of doing it, and the time difference was small, 0.1s before the actual gun went off. his trainer attributed that to the runner's amazing reflexes.

it's difficult to measure those things really. relativistic speeds are even harder to measure. I just don't think we have the proper time measuring mechanisms at the moment to answer all those questions with certainty.

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>>7815384

>Another thing I've read about spacetime is that light moves through the three spatial dimensions at c and at 0 through time

That meme has everything backwards. The equivalent of the distance formula in spacetime has a minus sign in it that the normal distance formula doesn't have. A clock that takes a straight path in spacetime (meaning no acceleration) from [math](t_1, x_1, y_1, z_1)[/math] to [math](t_2, x_2, y_2, z_2)[/math] measures a time of

[eqn]\frac{1}{c} \sqrt{c^2 (t_2 - t_1)^2 - \left((x_2 - x_1)^2 + (y_2 - y_1)^2 + (z_2 - z_1)^2\right)}.[/eqn]

"Speed through time" (time per time) is a bit of a confusing way to think about things, but if we explain what we mean carefully (unlike the meme), we can use the idea.

First, what would the equivalent thing with distance be? If we were traveling from Richmond to San Francisco, it might make sense to define the "speed" of a road as

(distance moved west) / (road length)

or equivalently

(length of road when projected onto another road going straight west) / (length of the road as measured along the road).

A straight road to San Francisco would have a large speed by that definition, while a road that weaved north and south would have a smaller speed.

The equivalent thing for time would be

(time as measured by a observer at rest in the coordinate system) / (time as measured by the object itself).

The meme would have you think that a fast moving object was traveling slowly through time. But by the more sensible definition of speed through time, it's actually moving faster. It's faster because the crucial minus sign in the formula makes a path through time that weaves back and forth through space shorter than a straight path through time.

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>>7815384

>Does an instantaneous change for a probability density make sense?

The only time you get an instantaneous change in probability density is when you measure something, and that can happen even without quantum mechanics. For example, if you lose a little screw on the floor, when you find the screw, the probability density of the screw being anywhere else but where you found it goes to zero.

LIkewise, when an atom emits a photon, the probability density for where the electron is changes smoothly if you're not measuring anything. But if I update the probability density given the answer to whether a photon has been emitted or not, the probability density changes abruptly.

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>>7810589

>What is the highest %age of c that humans have been able to accelerate a massive particle to?

I assume neutrinos don't count since they're not accelerated, so the record would go to LEP at 0.99999999997c.

https://en.wikipedia.org/wiki/Large_Electron%E2%80%93Positron_Collider#History

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>>7815408

I'm running out of kittys

>>7815785

ok I didn't really understand what you were trying to say, but yeah I wanna take a class on this or get a textbook at some point and do the math to understand this stuff

>>7815870

Damn that's pretty impressive, faster than the speed of light in air

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>>7812054

No, it's not, because being "pulled" by gravity is indistinguishable from an inertial reference frame. That's the whole point of general relativity. There is no true force acting upon you, you're just following the inertial straight line through curved spacetime. The photon is always going at speed c on whatever that line is, but the apparent physical distance it travels ends up changing when in a gravitational field, thus taking longer time.

>>7813634

The photon itself still travels at c regardless of the medium it's in, but interactions with other particles give off the impression that's it is traveling slower when viewed from a large scale.

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>>7810589

Here. This is how I /think/ it all works. I hypothesise that the expansion of the universe is the only thing that can change C as the 'gap' between the fundamental units increases. (and not by enough to be noticeable).

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>>7817180

>>7810589

Forgot the obligatory cat.

Forgot to mention that the fundamental building blocks althogh shown as 3D may in fact be 2D

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>>7811147

...get off /sci/, now.

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>>7817193

Fundamental blocks are 0D, otherwise they wouldn't be fundamental

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