# Does time stands still at c? And is room a point then?

• danov
In summary, objects that move with the speed of light, such as photons, do not experience time and their surrounding space is contracted to almost nothing. This concept is known as special relativity and applies to all objects that travel at the speed of light. However, it is important to note that photons do not have a "point of view" as they are not objects and this concept is not useful in understanding their behavior. Additionally, photons do not have mass but have energy, which allows them to travel at the speed of light. Overall, the behavior of photons and other objects traveling at the speed of light can be better understood through the study of special relativity and concepts such as length contraction and time dilation.
danov
hello, does time stand still for objects which move with c, like photons? And is the room contracted so much that its a point for thus photons?

Hi Danov,
no object will ever be seen to move at c from any point of view whatever. Look up 'special relativity'. Photons are not objects and don't have a point of view, so time as we experience it cannot be ascribed to photons.

Mentz114 said:
Hi Danov,
no object will ever be seen to move at c from any point of view whatever. Look up 'special relativity'. Photons are not objects and don't have a point of view, so time as we experience it cannot be ascribed to photons.

Why? Photons are waves and particles, Particle-Wave-Dualism. Or not?
Photons have no mass but they have energy. And because Mass=Energy and vv that doesn't matters. We know that Myons, which move nearly c, contract the room very much and time is passing much slower for them. Thats why they reach earth-surface. So Photons don't have any time-passing and any room. And that is strange. Wouldnt that mean that photons from their point of view would be everywhere at any time? I mean from their point of view the room is contracted to nearly nothing and so they reach one specific point without the need to move plus the time stands still for the photon and it can be at several places at a any time or even at many places at the same time?

Im sorry if I misunderstood something but I didnt studied physics yet.

This has been discussed about a zillion times before. While I could probably point you at some of the earlier threads, I've been a little busy recently :-(. I would suggest that if you really want a detailed answer, that you take a look at these earlier threads.

The short answer given above is correct, however, even if you don't find it satisfying. Photons do not have a "point of view" in the standard sense. Assuming that they do leads to severe difficulties, much as assuming that division by zero is possible does.

danov said:
Photons have no mass but they have energy. And because Mass=Energy...
Mass and energy are very different things, although they can be converted one to another. Photons do not have have mass and thus travel at c.

So Photons don't have any time-passing and any room. And that is strange. Wouldnt that mean that photons from their point of view would be everywhere at any time?

If a photon did have a point of view it would be very strange. But I doubt if it has any usefulness as a concept.

I mean from their point of view the room is contracted to nearly nothing and so they reach one specific point without the need to move plus the time stands still for the photon and it can be at several places at a any time or even at many places at the same time?

Well, the photons in a tight laser beam are not everywhere are they ? So some of what you say can be ruled out from common experience.

You should read Richard Feynmans book on QED.

Photons do not have have mass and thus travel at c.

But they do have relativistic mass and momentum...

danov said:
hello, does time stand still for objects which move with c, like photons? And is the room contracted so much that its a point for thus photons?

If you know about the invariant interval in relativity, ds, then you will know that ds is the proper time for the frame traveling along any path. But you will also know that a light-path is described by setting ds=0. So the proper time for the photon is not changing as it travels along the path. And this means that everything goes by the photon at the same time in its own frame. I guess that's your "point."

Here's a teaser: If the photon passes everything at once, is it traveling at infinite speed?

Mentz114 said:
Mass and energy are very different things, although they can be converted one to another. Photons do not have have mass and thus travel at c.

yes, but the important point to me is that something is able to travel at c

Mentz114 said:
If a photon did have a point of view it would be very strange. But I doubt if it has any usefulness as a concept.

ok, I chose a photon because its the only object i know which travels with c. Are there other objects that travel with c and therefore have no mass?

And I just don't understand why a photon should not have a point of view. I am still in school 12th grade yet but does not everything have a point of view? Thats what relativity-theory says: Everything is relative.

Mentz114 said:
Well, the photons in a tight laser beam are not everywhere are they ? So some of what you say can be ruled out from common experience.

You should read Richard Feynmans book on QED.

From OUR point of view they are not everywhere. But who knows how this looks like for a photon? Or what do you say? How much is room contracted for a photon? Let's say 1000 meters. And does time pass for a photon? If not: How much are 1000 seconds for a photon?

country boy said:
Here's a teaser: If the photon passes everything at once, is it traveling at infinite speed?

It don't needs to travel at infinite speed because the room at c speed, I think, is contracted so much that a photon (or anything else that fast) can reach every place in practically no time. But maybe that's my problem: How much is a room contracted for objecs at c? Maybe its not as much as I think. And what is the maximal room contraction at extremely high gravitational fields. But wait! Isnt it infinitely high at extrem big gravitational fields like center of black hole?

Look, the simple answer is the following:

In length contraction, the limit of x' as v->c is 0. The limit of t' is infinity. So, let's assume you get infinitely close to c (without reaching it). The universe becomes as a point, and all clocks have essentially stood still. The answer to both of the OP's question is essentially yes, with the caveat that you can get infinitely close to c but cannot reach it.

Hi Danov,
And I just don't understand why a photon should not have a point of view. I am still in school 12th grade yet but does not everything have a point of view?
No, it doesn't. Relativity is about inertial frames which are alway linked to matter. A point of view must belong to something that can see.

It is good that you explore these ideas and equations, but you must be aware that the Lorentz contraction no longer holds good when v=c.

I wish you well with your studies.

M

danov said:
It don't needs to travel at infinite speed because the room at c speed, I think, is contracted so much that a photon (or anything else that fast) can reach every place in practically no time. But maybe that's my problem: How much is a room contracted for objecs at c? Maybe its not as much as I think. And what is the maximal room contraction at extremely high gravitational fields. But wait! Isnt it infinitely high at extrem big gravitational fields like center of black hole?
A photon doesn't have a reference frame in relativity, so you can't really ask how much is a room contracted for objects at c. What you can do is ask what the length of the room is in the limit as an observer's speed relative to the room approaches c, and the limit in this case would be 0.

Hi Danov.
There is no actual answer that can be given to you about your question , this is because under the present set of "Rules" we work under (relativity etc) a photon has no point of view. And to most people the hypothetical point of view of a photon has no use, you might say that this is very unfair to the photon, which might indeed have a very extraordinary point of view. Now one day we could be in a position where we have the right set of "rules" that allow us to see this point of view but right now the only "observer" is you and me.

Hi, Infernos,

Welcome to PF! This thread is three years old. We try to discourage people from posting in old threads like this. (It's referred to as "necroposting.")

Hi bcrowell.
Thanks for the heads-up on posting protocol, I posted only due to relevance this post still has when searching on this topic on google (very close to the top!)

Infernos said:
Hi bcrowell.
Thanks for the heads-up on posting protocol, I posted only due to relevance this post still has when searching on this topic on google (very close to the top!)

Hello Infernos,

May be worth starting a thread of your own if you are looking for more specific information.

The general quality of response on this site is usually good and there are some very valid and authoratative posters.

## 1. What does it mean for time to stand still at the speed of light?

According to Einstein's theory of relativity, as an object moves closer to the speed of light, time slows down for that object. At the speed of light, time would theoretically stand still.

## 2. Is time really completely stopped at the speed of light?

No, time does not truly stop at the speed of light. This is a concept known as time dilation, where time appears to slow down for an object moving at high speeds. However, for an outside observer, time would still appear to be passing normally.

## 3. How does this concept of time dilation affect our perception of time?

Time dilation only becomes noticeable at speeds close to the speed of light, which is much faster than anything we experience in our daily lives. Therefore, for most practical purposes, we do not experience any significant effects on our perception of time due to time dilation.

## 4. Does this mean that time is relative to an observer's speed?

Yes, according to the theory of relativity, time is relative to an observer's speed. This means that different observers can experience different durations of time depending on their relative speeds and positions.

## 5. How does this relate to the concept of room being a point at the speed of light?

At the speed of light, objects would appear to contract in length, including the distance between two points. Therefore, at the speed of light, the room would appear to be a single point. However, this is a theoretical concept that cannot be achieved in reality due to the limitations of the speed of light.

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