# Why Does light have a speed limit.?

krom
Am I allowed to Ask Questions that have no answers? as I guess your answers will be personal theory, and this site doesn't allow them?.

Catch 22 no?

I think I have the answer, but I'm not allowed to post it here as its a personal theory, anyone know where its possible to post it, and maybe chat about it. I have tried posting it on here, but its been removed even from the general chat, for being a personal theory, how do we try and answer questions that don't have answers?, without it being a theory.?

I can't tell you why I think light has a limit! because It will get removed?. not even in the forum where there's such posts as "I hate my parents" and "is time real?" .

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Staff Emeritus
Gold Member
Am I allowed to Ask Questions that have no answers? as I guess your answers will be personal theory, and this site doesn't allow them?.

Catch 22 no?
My answers certainly won't be personal theories.

Are you asking "why does light travel at c?", or "why can information not be transmitted faster than c?".

Staff Emeritus
Gold Member
I think I have the answer, but I'm not allowed to post it here as its a personal theory, anyone know where its possible to post it, and maybe chat about it. I have tried posting it on here, but its been removed even from the general chat, for being a personal theory, how do we try and answer questions that don't have answers?.
As has been said before, you may submit your properly formatted personal theory to the Independent Research forum. Have you perhaps considered that there is already an answer to your question(s)?

Staff Emeritus
Am I allowed to Ask Questions that have no answers? as I guess your answers will be personal theory, and this site doesn't allow them?.

Catch 22 no?

I think I have the answer, but I'm not allowed to post it here as its a personal theory, anyone know where its possible to post it, and maybe chat about it. I have tried posting it on here, but its been removed even from the general chat, for being a personal theory, how do we try and answer questions that don't have answers?, without it being a theory.?

I can't tell you why I think light has a limit! because It will get removed?. not even in the forum where there's such posts as "I hate my parents" and "is time real?" .

There is a difference between "asking a question" based on the desire to learn, versus "asking a question" simply to expound on one's personal theory that hasn't been verified. If you do not know the difference between the two, then you definitely have come to the wrong place. You have been shown the IR forum where this may be considered, per the rules of that forum.

Zz.

krom
you read it pm?, its not that bad, also its ruff, I just wanted people talking about things we no nothing about, maybe there's something there to be learnt.

I asked why light has a limit, and my idea has an answer, just wanted to see what others thought, don't take it as anything other than a brain storming event.

IR forum? I have been shown nothing, I'm new I don't know what you mean by IR.

krom
My answers certainly won't be personal theories.

Are you asking "why does light travel at c?", or "why can information not be transmitted faster than c?".

Homework Helper
Gold Member

what makes you think we know nothing about it?

Staff Emeritus
Gold Member
I asked why light has a limit
Are you asking "why does light travel at c?", or "why can information not be transmitted faster than c?".
Or are you asking "why does light travel at c in a vacuum and slower in other media"?

Staff Emeritus
Gold Member
For the former, the speed of light can be derived by applying Maxwell's equations to the wave-equation. For the latter, have a read of http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html" [Broken].

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krom

Why does it have a so called limit to its top speed. why can't it go faster? are you talking about working out the speed of light? I want to know why it has a fixed top speed.

Staff Emeritus
IR forum? I have been shown nothing, I'm new I don't know what you mean by IR.

You should have a read of the thread that you started asking where you can post such topics. :grumpy:

Staff Emeritus
you read it pm?, its not that bad, also its ruff, I just wanted people talking about things we no nothing about, maybe there's something there to be learnt.

I asked why light has a limit, and my idea has an answer, just wanted to see what others thought, don't take it as anything other than a brain storming event.

IR forum? I have been shown nothing, I'm new I don't know what you mean by IR.

Have you been reading your PM? You were given a link to the Guidelines. The IR (Independent Research) forum is clearly mentioned there. If not, you can also read the "Rules" that is linked at the top of the Physics Forums page.

These guidelines are what you agreed to when you join PF.

Zz.

per.sundqvist
There is no proof of why there is a limit of speed of light, nigther can you proof theoretically that Newtons equatios are true (because they are axioms). Its a question of practice and experience. Theories, that we accept, are excepted because they agree with reallity. If you could find out an experiment where you could disproof it, then we have to rethink!

As a start it is good to look at what assumtions does these theories makes? Can you find an example which violate these certain conditions? Then you may find the way to the noble prize... New physics is more about finding these "backdoor" ways than defending old truth! I strongly encourage you to continue! (I also did when I was younger, and haven't we all once tried to develop perpetum mobile?)

Best,
Per

Cvan
If light did not travel at c, I severely doubt the universe would have arisen in the fashion it had, and that we would not be here to question the speed of light.

Mentor
Krom, you seem to have missed it, but you were given the answers in post #9. Or are you not intrerested in the real answers?

Free-form, idle speculation/brainstorming just isn't how science is done. That's why we don't allow it here: this is a science forum.

Littlepig
Because science don't explain why things happens, but how they happens...xD

Now, if you want the why, make a call to the Universe's Arquitect.

Physics explains reality, try to formulate laws that agree with it. How light propagates at speed c: Due to electromagnetic waves and is invariance due observers; why it does that way? Every physicist answer would be based on intuition and not on actual physical understanding. Because the hole theory of Relativity is based on the axiom that light travels in vacuum at c and is independent from observer. Why that principle? Because so far it fits in experiments(and so in reality).

My guess is that you should read something about it, Steven Hawking and others have some interesting books about it. ;)

Magic Man
Everything has a limit. The speed of light is not limited because of some universal rule but because of the medium it travels through and to get from one place to another has to involve some passage of time.

c is the speed at which photons travel through a vacuum which is, to our current knowledge, a 'path of least resistance' to their passage. If you can get a 'cleaner' medium than a vacuum (perhaps one without the other particles and potential dark matter etc. that 'clutter' space) then there is no reason not to theorise that photons may travel at speeds higher than c through this medium.

Littlepig
Everything has a limit.

Prove it, otherwise is just your opinion. And this isn't about opinions, or at least without fundament.
No one proved so far that exists a fundamental particle(like greeks thought about atom), as no one proved that it doesn't exist, so, no: so far you can't say that, you are only speculating based on intuition.

Magic Man
I think you know I was speaking generally and in context to the medium.

You cut the quote short. I was stating that any limit is only that which is imposed by the medium it is traveling through.

nuby
Dumb question about c: is it an angular velocity or linear? or both somehow.

Mentor
Linear speed only.

RossD
If the relative speed or velocity of light remains constant even when the velocity of the source or observer changes how can there possibly be any doppler effect (red/blue shift)with light?? Frequency is directly related to velocity!

Staff Emeritus
Gold Member
If you want to know why light moves at c, the answer is that it's a consequence of Maxwell's equations. (You already got that answer).

So why do Maxwell's equations hold? They are a consequence of the fact that the electromagnetic field (the vector potential) is a massless vector field on Minkowski space. Actually that's more of an equivalent formulation of the theory than a reason why it holds, but if we consider quantum electrodynamics, the concept of renormalizability tells us why there are no other interaction terms in the Lagrangian. (There may be other terms, but non-renormalizable terms do not contribute noticeably to experiments at low energies).

Why is the field massless? That question doesn't make much sense, as it is part of the definition of what we mean by "light".

Why is spacetime Minkowski space? It isn't really. General relativity tells us that there's a relationship (expressed by Einstein's equation) between the geometry of spacetime and its matter content. Minkowski space is the particular solution that corresponds to an empty universe: No matter, no gravity, no nothing. But GR also tells us that a spacetime with matter looks like Minkowski space locally. What that really means is somewhat technical, but you can think about it this way: When you look at a small enough region, its geometry will appear to be flat, just as a small region of the surface of a sphere appears to be flat. This property of spacetimes in GR is sufficient to make the speed limit (locally) the same as in SR.

So why does GR hold? No one has an answer to that yet, and even if they did, it would create another why question. This is a problem you'll eventually run into no matter what question you start with.

kahoomann
Because science don't explain why things happens, but how they happens...xD

Now, if you want the why, make a call to the Universe's Arquitect.

Physics explains reality, try to formulate laws that agree with it. How light propagates at speed c: Due to electromagnetic waves and is invariance due observers; why it does that way? Every physicist answer would be based on intuition and not on actual physical understanding. Because the hole theory of Relativity is based on the axiom that light travels in vacuum at c and is independent from observer. Why that principle? Because so far it fits in experiments(and so in reality).

I'm sure Einstein didn't get his axiom that light travels in vacuum at c from "Universe's Architect". So the question is: where and how he got his axiom in the first place?

Staff Emeritus
Gold Member
I'm sure Einstein didn't get his axiom that light travels in vacuum at c from "Universe's Architect". So the question is: where and how he got his axiom in the first place?
The was/is strong experimental and theoretical evidence for the invariance of C. Astronomical measurements of double stars by De Sitter together with the theoretical work on electrodynamics by Lorentz are often quoted at this juncture.

Mentor
If the relative speed or velocity of light remains constant even when the velocity of the source or observer changes how can there possibly be any doppler effect (red/blue shift)with light?? Frequency is directly related to velocity!

Frequency is also directly related to wavelength: $c = f \lambda$. In the Doppler effect, both the frequency and the wavelength change, but in opposite directions, so that c remains the same. For example, with the source and observer approaching each other, the frequency increases and the wavelength decreases.

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LongOne
Free-form, idle speculation/brainstorming just isn't how science is done. That's why we don't allow it here: this is a science forum.

Hi Russ,
I think you overstated this in sort of a demeaning manner to your correspondent. Brainstorming is a valuable part of scientific work during the early part of the process. Prior to the time that a theory is developed and a prediction/hypothesis can be formulated, there are many different ways in which one may get an idea that could pan out. Clearly, one of these is brainstorming.

There was a recent show on the Research Channel, "Frontier" (a continuing series), sponsored by NSF, that discussed the scientific process and how the early stages of discovery include "out of the box" thinking, brainstorming, comments from peers, seeing an analogous situation, etc. Unfortunately, I cannot remember who the speaker was. But the speaker's intention was to highlight the fact that ideas come from many different places in many different ways. As I recall, he mentioned several specific examples (but age has taken its toll on my memory!) These ideas, of course, are followed up by application of the more customary scientific process.

Regards

shamrock5585
light speed

why is it exactly that nothing with mass can travel at 'c' ?

could it be that we just have never found anythign that travels faster than the speed of light in a vacuum?

how did einstein come to this conclusion?

why is it exactly that nothing with mass can travel at 'c' ?

could it be that we just have never found anythign that travels faster than the speed of light in a vacuum?

how did einstein come to this conclusion?

In order to accelerate anything to get to the speed of light, it would take an infinite amount of energy, since the mass would be infinite.

shamrock5585
why would the mass be infinite? i remember einstein saying that the faster something travels the more mass it acquires... but why is this? how does that work?

Mentz114

why is it exactly that nothing with mass can travel at 'c' ?

could it be that we just have never found anything that travels faster than the speed of light in a vacuum?

how did einstein come to this conclusion?

Can you work out what the universe would be like if we could send out a beam of light, and then catch up with it ? This is one thought that drove Einstein towards special relativity.

Another obvious point is that if there were no upper limit on the speed of information, we could not experience the passage of time because everything would happen at once.

M

shamrock5585

Can you work out what the universe would be like if we could send out a beam of light, and then catch up with it ? This is one thought that drove Einstein towards special relativity.

Another obvious point is that if there were no upper limit on the speed of information, we could not experience the passage of time because everything would happen at once.

M

yes it would be pretty weird if we could send light and catch up with it to observe yourself, but if a person "could" ever do it you would have to accelerate damn fast to do it in a reasonable distance which would kill any human from the amount of force due to acceleration...

with information being sent that fast doesn't mean everything would happen all at once, it just means that if you sent a message it would be received almost instantaneously... but no matter how fast something is moving it would still take time even if something could travel faster than light... for it to happen even instantaneously the message would have to be sent at an infinite speed to give a value of time change to be zero... this is obviously impossible...

I like mathmans reasoning... I am wondering why does an object increase mass when traveling faster... it would have more energy traveling faster... and energy and mass are one and the same... so would it just increase relativistic mass when traveling faster? is it possible to measure relativistic mass?

if it travels faster and faster aquiring more and more energy/mass to reach the finite speed of light how does the mass get to infinity when approaching the speed of light?