Why Does Light Experience Time Differently Than Objects with Mass?

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Discussion Overview

The discussion revolves around the nature of light and its relationship with time, particularly in the context of relativity. Participants explore why light, which travels at the speed of light, seems to experience time differently than objects with mass. The conversation touches on theoretical implications, the concept of light's "age," and how measurements of light may be influenced by relativistic effects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants question why the effects of relativity, which apply to objects moving at high speeds, do not seem to apply to light itself.
  • There is a suggestion that light (photons) has no resting mass, which may allow it to travel at the speed of light, though this point remains uncertain among participants.
  • One participant proposes that if humans could achieve near-light-speed travel, it might reveal new understandings of the universe's laws.
  • Participants express curiosity about the concept of a photon's "age" and whether there is a meaningful difference between photons of varying ages.
  • Concerns are raised about how measurements of light waves might be skewed by the observer's frame of reference and the implications of time dilation on these measurements.
  • Some participants discuss the Doppler effect and its relevance to the discussion, while others express confusion about the relationship between light's properties and time.
  • There is a debate about whether light experiences time, with some asserting that it does not, while others question the implications of this assertion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of light's relationship with time. Multiple competing views are presented, particularly regarding whether light experiences time and how its "age" should be understood.

Contextual Notes

Participants acknowledge limitations in their understanding of complex concepts like relativistic mass, the nature of photons, and the implications of the Big Bang on light's properties. There are also unresolved questions about the definitions and implications of measuring light's "age."

ClarkKivette
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When we consider something traveling at or near the speed of light, the theory of relativity applies, and the thing moving very fast is experiencing time differently than us.
My big question is ... Why shouldn't this apply to light? Because light is traveling at the speed of light, and the same math that illustrates objects experiencing time differently should apply to light.
When we view light from something 10 million light years away, we assume the light itself is 10 million years old. If this were not true you could raise some interesting questions.
This is an unusual point, and how does time really apply to something without mass. But if you imagine aliens observing our world at the wrong speed, they my see everything but not have a real understanding of what there looking at, and the laws of our physics would appear bizarre. When we observe the electromagnetic spectrum and measure wave lengths, we are doing that from our perspective and time, and we are the aliens.
 
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Well, I'm really not someone who knows for sure, but I think it has something to do with light (heretofore photons) having no resting mass but relativistic mass. And I think that's also why (having no resting mass) is the reason it can go that speed, but I'm not sure. Wait until someone else sheds some light on the situation;).
 
Originally posted by Decker
Well, I'm really not someone who knows for sure, but I think it has something to do with light (heretofore photons) having no resting mass but relativistic mass. And I think that's also why (having no resting mass) is the reason it can go that speed, but I'm not sure. Wait until someone else sheds some light on the situation;).

Very interesting thought. I have this sneaky feeling that what Science has theorized with regards to many things in Physics might not be taking this idea into the realm of possibility. I believe that if we, as humans, could achieve space travel near the speed of light that a new Universe might come into focus that would greatly increase our grasp of the laws of the universe.
 
I'm more interested in the concept of light's "age." What's the difference between a 5-year-old photon and a 50 million-year-old photon?

cookiemonster
 
I don't know the difference between a 5 year old photon and a 50 million year old photon. I guess I'm having a hard time expressing myself. When I was talking about observing wavelengths I was tring to express one way that are preception could be skewed. When we measure a light wave, say from crest to crest, we are using our time to measure that distance. If what you were measuring is essentially functioning at a different time, your measurement wouldn't be right, and your overall understanding of what you were looking at would be wrong.

When I was talking about light that has been traveling 10 million years not being 10 million years old. I was thinking of things like how we use the expansion of the universe as arrow of time to show the direction time flows. When we measure time there is some kind of distance covered..the hand of a clock, ligh tavaling a meter etc. If you consider the big bang an obvious starting point, and the first light to leave it to be the oldest and has traveled the farthest. This would be as legitimate as the movement of a clock hand that represents the pasting of time for the universe. The interesting thing is the light that has taveled the farthest and is the oldest would be newer than that which it left behind if relativity applied to it. This would make reading and interpreting the clock interesting.
 
It seems to me that half of what you're describing is the Doppler effect. The other half I don't understand.

When I was talking about light that has been traveling 10 million years not being 10 million years old.

Again I ask, what does a photon being 10 million years old mean? Two photons of the same wavelength, one 5 years old and the other 50 million, are indistinguishable. We can't observe any difference between them.

As for light from the Big Bang, the universe wasn't actually transparent until about 300,000 years (if my memory serves) after the Big Bang. Before that, photons interacted with other particles. So I suppose we might be able to see photons from 300,000 years after the Big Bang (maybe not, I'm not fluent enough on the subject to give a real definitive answer).

A "photon clock" wouldn't work because, as I said above, time does not change a photon's properties, making them indistinguishable.

Just a note on the "flow" of the universe, the isotropic property (someone please check me on this: is this the right one? I'm so bad with names) of the universe prevents us from determining the absolute direction in which we're moving. It essentially states that due to the expansion of the universe, we observe everything, in all directions, to be moving away from us. Thus, everything is redshifted. Also, things that are farther away from us are moving away more quickly. That's why we measure distances from objects in terms of their redshifts.

Maybe I'm just not understanding what you're saying. If I am, I apologize.

cookiemonster
 
Originally posted by ClarkKivette
When we consider something traveling at or near the speed of light, the theory of relativity applies, and the thing moving very fast is experiencing time differently than us.

sorry, but your statement seems vague to me. I understand that when you travel near C you will experience time just the same as if you were not moving (relative to your earlier speed). Although time for the nearC speeder will be operating slower relative to the time of a relatively non-moving observer.

Originally posted by ClarkKivette

My big question is ... Why shouldn't this apply to light? Because light is traveling at the speed of light, and the same math that illustrates objects experiencing time differently should apply to light.

my explanation for this is that it does. (i hope i am not missinterpeting your question) As you travel near the speed of light, the light frequency will slow down. Likewise, as the light frequency in your reference frame slows down (incorrect terminology i know) your speed or gravitational state must be somewhat simultaneously adjusting to relatively make sense. If you are really asking a totally different question please elaborate and I will try and help.

Originally posted by ClarkKivette
When we measure a light wave, say from crest to crest, we are using our time to measure that distance. If what you were measuring is essentially functioning at a different time, your measurement wouldn't be right, and your overall understanding of what you were looking at would be wrong.

my answer to this is that when we are measuring the frequency of light in our particular reference frame, we can also measure our own gravitational and/or velocity (incorrect terminology i know) time dilation in our referece frame so that our formula encompass all of these applications that may be manipulated for further study of relative situations.

Originally posted by ClarkKivette
The interesting thing is the light that has taveled the farthest and is the oldest would be newer than that which it left behind if relativity applied to it. This would make reading and interpreting the clock interesting.

please explain further...left behind?

sincerely,
Mike Svenson
 
relativity doesn't really matter till you start approaching the speed of light.

even then, you can figure out relativistic speed and time using formulas, so it all simplifies down to the same thing anyways i think.
 
Originally posted by cookiemonster
I'm more interested in the concept of light's "age." What's the difference between a 5-year-old photon and a 50 million-year-old photon?

cookiemonster
Nothing: light does not experience time. This likely explains why a photon appears to "know" everything about its trip from the momen it is emitted, regardless of whether the path has even been decided yet.
The interesting thing is the light that has taveled the farthest and is the oldest would be newer than that which it left behind if relativity applied to it. This would make reading and interpreting the clock interesting.
That doesn't make any sense. Light travels at C. How can one photon traveling at C pass another photon that is also traveling at C?
 
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