The feeling of time while traveling at the speed of light

Click For Summary

Discussion Overview

The discussion revolves around the theoretical implications of experiencing time while traveling at the speed of light, specifically through the lens of a hypothetical traveler on a photon. Participants explore the nature of time, change, and perspective in relation to light and relativistic physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant proposes a scenario where a traveler on a photon would experience no passage of time, raising questions about the nature of time and location for such a traveler.
  • Another participant argues that the exercise is pointless and refers to previous discussions on the topic.
  • Some participants assert that if photons do not age, they cannot experience change, questioning the relationship between time and change.
  • There is a claim that assuming photons experience time leads to contradictions, with references to incorrect assumptions leading to nonsensical conclusions.
  • One participant mentions that for a traveler moving just under the speed of light, the experienced time would be approximately 44.7 years, challenging the notion that time would be zero.
  • Discussions arise about the ambiguity of light's "perspective" and the lack of an inertial reference frame for light, complicating the understanding of time from a photon's viewpoint.
  • Some participants express uncertainty about the validity of claims regarding photons not aging and seek clarity on how to conceptualize time for massless particles.

Areas of Agreement / Disagreement

Participants do not reach a consensus, with multiple competing views on the nature of time for photons and the implications of traveling at the speed of light. Disagreements persist regarding the validity of assumptions made in the scenarios presented.

Contextual Notes

Limitations include unresolved assumptions about the nature of time and change for massless particles, as well as the implications of relativistic physics on the discussion of perspective.

arkay
Messages
2
Reaction score
0
So I have been wondering about something, this is completely theoretical obviously you cannot sit on a photon but think about this and let's see what you think...

We have a Photon traveling at the speed of light from one point to another. The origination point, a light source 1000 light years from Earth. Now, let's say a traverler is very tiny and sitting on that photon traveling from the light source to Earth.

A) If the photon is traveling at the speed of light, and time slows down relative to the item in transit, 1000 years will have passed on Earth before the journey is complete, however to the traveler, relatively, no time would have passed. So that leaves two questions: 1) For the traveler, how long would it "feel like", he was sitting on the photon? Was it instant, or was he sitting there for a thousand years? 2) If no time would have passed then the photon, and the traveler on the photon would appear to be in more than one place at a time, in fact would he not be in every place within the path at the same time until the photon slows under the speed of light? Is that a paradox?

B) Now let's take the same scenerio as A except slow the photon down so it is moving just under the speed of light, so the entire trip takes 1001 years now. Does that traveler feel as though he has been sitting on the photon for 1 year or 1001 years?
 
Physics news on Phys.org
arkay said:
So I have been wondering about something, this is completely theoretical obviously you cannot sit on a photon but think about this and let's see what you think...

I think that that in fact, it is not even theoretical, but that it's a pointless exercise.

I have already explained it before here, so - being a lazy physicist/mathematician, I'll just refer you to that thread :-)
 
A) is not possible as mentioned by CompuChip, so I will stick with B).
arkay said:
B) Now let's take the same scenerio as A except slow the photon down so it is moving just under the speed of light, so the entire trip takes 1001 years now. Does that traveler feel as though he has been sitting on the photon for 1 year or 1001 years?
Actually it is 44.7 yrs for the traveller.
 
Interesting that someone else had a very similar thought. Almost worded the scenerio the same as me too. Kinda wierd.

Anyway thanks for the link, that was a very interesting thread.
 
In the link, a couple of responders said that, "You can claim 'photons don't age' if you like," and "For photons, the infinitesimal interval is zero, and in this sense, photons experience no time." I think the question both OP's either stated or hinted at what, if it was like something to be a photon, what would it be like? If a photon experienced, what would the experience be like?

If photons "experience no time", then can they experience change? Is change dependent on time?

I'm not sure if the question crosses out of physics and into philosophy, but I'd wondered the same thing myself and might have found an appropriate forum to gain some understanding.
 
The short answer is that assuming photons experience time is like dividing by zero. It leads to contradictions. Other ways of saying this

"Garbage in, Garbage out" (a bit impolite, perhaps, I don't really mean to be perjorative, it's just that if you make an incorrect assumption, incorrect conclusions follow).

"Loaded question". ("A loaded question is a question which contains a controversial assumption such as a presumption of guilt. Or in this case, an assumption that relativity is invalid."). People want to ASSUME that they can travel as fast as light in spite of the fact that it's impossible. Why, I don't know. Some of it might be sloppy thinking, in terms of thinking that is possible to answer questions in a framework where the assumption is inconsistent with said framework without getting nonsense.
 
DaleSpam said:
Actually it is 44.7 yrs for the traveller.

How it can be? Light never slows down, it just takes longer path, so time experienced by the photon rider (If there is any) will still be Zero.
 
pervect said:
People want to ASSUME that they can travel as fast as light in spite of the fact that it's impossible. Why, I don't know.

I suspect in this case, with most people naturally having bad intuition for anything involving limits, it feels very natural to assume that v = c is just the limit case of the v < c theory.
 
NoDoubt said:
How it can be? Light never slows down, it just takes longer path, so time experienced by the photon rider (If there is any) will still be Zero.
In case 2 we were explicitly discussing something slightly slower than c, e.g. an observer riding a pulse of light in a dielectric medium. Just use the spacetime interval formula to get the proper time.
 
  • #10
DaleSpam said:
In case 2 we were explicitly discussing something slightly slower than c, e.g. an observer riding a pulse of light in a dielectric medium. Just use the spacetime interval formula to get the proper time.

Oh.., I see, Now it is "something" slightly slower than c, Then the formula will work perfectly, But I thought I heard "photon moving just under the speed of light". Never heard that before. :smile:
 
  • #11
Did you even read the OP? Take it up with him, it isn't my scenario.
 
  • #12
CompuChip said:
I suspect in this case, with most people naturally having bad intuition for anything involving limits, it feels very natural to assume that v = c is just the limit case of the v < c theory.

So does that mean that the posters who said that photons don't age were wrong--or at least that they didn't have good justification for claim?

Maybe my hang-up is that I'm familiar with a framework for thinking about time for massive things that travel at less than the speed of light--but then there are these things that travel at the speed of light. Is there a way to think about time for them?
 
  • #13
You can certainly say that the proper time along the worldline of a pulse of light is 0.

The problem comes when people try to go beyond that and start talking about light's "perspective". In relativity an object's perspective refers specifically to the reference frame where that object is at rest. There is no inertial reference frame where light is at rest, so there is no unambiguous meaning to the term "photon's perspective", just as there is no unambiguous meaning to the "perspective" of a non-inertial object.

In both cases you have to define exactly what coordinate system you mean, and people asking such questions never do that.
 
  • #14
DaleSpam said:
You can certainly say that the proper time along the worldline of a pulse of light is 0.

The problem comes when people try to go beyond that and start talking about light's "perspective". In relativity an object's perspective refers specifically to the reference frame where that object is at rest. There is no inertial reference frame where light is at rest, so there is no unambiguous meaning to the term "photon's perspective", just as there is no unambiguous meaning to the "perspective" of a non-inertial object.

In both cases you have to define exactly what coordinate system you mean, and people asking such questions never do that.

Very interesting. So, if "perspective" in relativity refers to the reference frame of an object at rest, and light is never "at rest", is it true to say that light has no perspective? Or, is talking about a photon's perspective ambigious, but clear and sensical provided that you define a coordinate system?
 

Similar threads

High School Let me ask a thing about the Speed of Light
  • · Replies 6 ·
Replies
6
Views
2K
High School One-Way Speed of Light
  • · Replies 93 ·
4
Replies
93
Views
6K
Undergrad Another Time Dilation Question
  • · Replies 42 ·
2
Replies
42
Views
5K
High School Would We See the Same Light After Traveling Back to Earth Faster Than Light?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Time dilation and the human body
  • · Replies 11 ·
Replies
11
Views
2K
High School Experience Travel on a Photon: Hitch-Hiker's Guide to the Universe
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad A question about the speed of light and electromagnetism
  • · Replies 51 ·
2
Replies
51
Views
5K
High School Why Do Events Freeze For Me at the Speed of Light?
  • · Replies 4 ·
Replies
4
Views
1K
Graduate 1-Way Speed of Light
  • · Replies 42 ·
2
Replies
42
Views
3K
Undergrad One way speed of light
  • · Replies 26 ·
Replies
26
Views
1K