By photon's POV, would light travel infinity in no time?

[Flatland]

The limit of time passage approaches zero as an object appoaches the speed of light from a speed less than the speed of light, but I don't see any reason for an object that only exists at the speed of light not to experience time. The path of a photon changes due to gravitational fields. From the perpective of a photon, relative movement of other objects occurs, it's position relative to other objects changes with respect to time. A photon also has a frequency, a change of state versus time.

Ok, you have to deal with the fact that from the perspective of a photon, the speed of light isn't constant (another photon traveling in the same direction has zero velocity, while a photon not traveling in the same direction has observed velocity), but again, this is a special case for a frame of reference, with different set of rules than sub-light speed objects.

Very very very very incorrect. From the perspective of a photon, the universe is still a singularity. A photon cannot "see" an events occur as everything for it happens at once.

 

[MeJennifer]

I just wanted to make a comment on the "you can't take the POV of a photon" argument.

Despite this whole argument we can consider the topological structure of Minkowski space-time. And one property of this space-time is that there are points that have a zero distance between many other points. And photons happen to be on those points.

Causality is not as straightforward as in case of a Euclidean space-time. For instance the neighborhood of a point in Minkowski space-time is far from localized, since it intersects with null and near null lines from other points.

 

[Chris Hillman]

Jennifer,

Don't confuse the underlying euclidean topology with the indefinite signature metric tensor.

There is a notion of "metric topology" studied in general topology which is very important in analysis, but this always refers to a postitive definite metric, and the topologies used in gtr and allied theories are certainly not metric topologies in this sense. This is not sufficiently emphasized in most textbooks, but you have noticed the key point: the Minkowski analog of "balls" would be noncompact, so the topology you would come up with would be very unlike the one which is actually used!

Without mentioning names, there is at least one relativity crank who went off the deep end by pursuing the observation which you rediscovered, so be careful in surfing the web that you are reading about mainstream science rather than one person's profound misconceptions. To mention a distinct example, the late Alexander Abian wrote a sane monograph or two as a younger man, and was apparently a popular and successful teacher for many decades, despite being well known on the net for his proposals to "blow up the Moon" and so on.

 

[MeJennifer]

Don't confuse the underlying euclidean topology with the indefinite signature metric tensor.

I don't think I am, but I don't know how else could I explain it easily.

There is a notion of "metric topology" studied in general topology which is very important in analysis, but this always refers to a postitive definite metric, and the topologies used in gtr and allied theories are certainly not metric topologies in this sense.

Right!

the Minkowski analog of "balls" would be noncompact, so the topology you would come up with would be very unlike the one which is actually used!

Right, that is what I wanted to bring across.

 

[Chris Hillman]

Topological structure versus algebraico-geometric structure

Hi, Jennifer,

I don't think I am

I think you are. This is why:

Despite this whole argument we can consider the topological structure of Minkowski space-time. And one property of this space-time is that there are points that have a zero distance between many other points.

OK, now I really have to go!

 

[TucsonDean]

The original poster is just trying to understand the nature of time and space at very high speeds, so let's just re-phrase the question this way:

As a THOUGHT EXPERIMENT, if I have an infintesimal mass, and am traveling at the maximum speed an infintesimal mass can travel, how would I experience time and space?

Let's also remember that it's a THOUGHT EXPERIMENT, and not worry about whether an infintesimal mass can experience anything.

Then we can leave it to the poster to imagine what would happen at the limit.

 

[JesseM]

TucsonDean, you're resurrecting a thread that no one has posted on for over 2 years! (not to mention that the original poster has since been banned) If you're interested in this subject, better to either start a new thread, or post on a more recent thread related to this topic such as this one.

 

[TucsonDean]

OK, thanks, didn't notice the date. I am a physicist and know the answers, was frankly mostly getting on folks for being so unhelpful to the original poster.

 

[cfrogue]

OK, thanks, didn't notice the date. I am a physicist and know the answers, was frankly mostly getting on folks for being so unhelpful to the original poster.

May I ask the answers?

 

[TucsonDean]

The quick answer is that time in the surrounding environment appears to slows down and the physical dimension of space in the direction of motion appears shortened. The faster one goes, the more profound the effect. At the speed of light, which an object with mass cannot attain, time would stop altogether and space in the direction of motion would shrink down to nothing.

 

[cfrogue]

The quick answer is that time in the surrounding environment appears to slows down and the physical dimension of space in the direction of motion appears shortened. The faster one goes, the more profound the effect. At the speed of light, which an object with mass cannot attain, time would stop altogether and space in the direction of motion would shrink down to nothing.

This is logically inconsistent with the limit being attained.

Your focus is on logic as the limit is approached.

This has nothing to do with operating at the limit.

 

[DaveC426913]

This is logically inconsistent with the limit being attained.

Your focus is on logic as the limit is approached.

This has nothing to do with operating at the limit.

He gave you the answer. Do you not like it?

The limit cannot be attained but we can come arbitrarily close to it. The universe will be arbitrarily close to zero in depth in the direction travelled; time will be arbitrarily close to stopped. Also, the radiation frequency impinging on it will be arbitrarily close to infinite.

 

[cfrogue]

He gave you the answer. Do you not like it?

The limit cannot be attained but we can come arbitrarily close to it. The universe will be arbitrarily close to zero in depth in the direction travelled; time will be arbitrarily close to stopped. Also, the radiation frequency impinging on it will be arbitrarily close to infinite.

My mistake. I thought light operated at this limit.
Is this false?

Perhaps you could also explain what happens at this limit.

I would like to know.

 

[DaveC426913]

My mistake. I thought light operated at this limit.

Photons travel at c, yes.

The catch is that photons do not have a valid frame of reference. Time does not pass for a photon. It is nonsensical to ask what a photon experiences because a photon has no experience.

Perhaps you could also explain what happens at this limit.

The question has no answer; the question itself is malformed. The very word "happens" implies the passage of time, which does not exist at the speed of light.

 

[cfrogue]

Photons travel at c, yes.

The catch is that photons do not have a valid frame of reference. Time does not pass for a photon. It is nonsensical to ask what a photon experiences because a photon has no experience.


The question has no answer; the question itself is malformed. The very word "happens" implies the passage of time, which does not exist at the speed of light.

If you check now what I was asking the poster, you will see this is what I was implying and thus I do not understand your post to me that discussed the "limit" being approached.

 

[DaveC426913]

If you check now what I was asking the poster, you will see this is what I was implying and thus I do not understand your post to me that discussed the "limit" being approached.

Ah. So you and I agree?

So you were challenging TucsonDream about what would happen at the limit, because you knew he couldn't provide a sensical answer?

I think I see that now.

 

[lalbatros]

Could the initial question not be easily answered by representing the Lorentz transformation as two different grids on the (x,t) plane. I think that the v=c limit would clearly appear as degenerate: there is no good frame of reference by squeezing the coordinates up to the speed of light.

 

[cfrogue]

Ah. So you and I agree?

So you were challenging TucsonDream about what would happen at the limit, because you knew he couldn't provide a sensical answer?

I think I see that now.

Yes, you and I agree and your assessment is correct.

 

[DaveC426913]

Could the initial question not be easily answered by representing the Lorentz transformation as two different grids on the (x,t) plane. I think that the v=c limit would clearly appear as degenerate: there is no good frame of reference by squeezing the coordinates up to the speed of light.

I think the point is that, anyone who can understand Lorentz transforms already understands relativistic effects.

If they don't understand relativity, telling them about Lorentz transforms is not going to help them much...