Questions about photons. Their interaction with time and their life-cycle.

In summary: That is, there is no proper time along its trajectory. This is a fundamental aspect of special relativity and is necessary to maintain the constancy of the speed of light in all inertial frames of reference.However, as atyy mentioned, this does not mean that photons do not move forward in time. In fact, they do, as observed by an external observer. But for the photon itself, there is no sense of time passing along its trajectory.As for what happens when a photon ceases to exist, it can either be absorbed by another particle (creating other particles in the process) or it can simply continue on its trajectory until it interacts with something else. The process by which photons end their life is ultimately determined by the interactions and
  • #1
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Do photons experience time? If they move at the speed of light then special relativity states that they do not, but then does that mean they do not move forward in time which means the distance they travel is instantaneous (thus it is infinitely fast), which we know is not true (as they move at the speed c).

Furthermore, what happens when a photon ceases to exist? How does it cease to exist? Does it hit my body and 'poof' it is gone? what is process by which photons end their life.
 
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  • #2
There was recently an ample thread about a similar subject, about 12 pages long, that was unfortunately deleted.
So now we'll probably need 12 pages again to answer this.

When they cease to exist they collide with another particle (which can also be another photon) and they create other particles (which can also be other photons).
 
  • #3
About experiencing time, a short answer would be "they don't".

Speed of light travel is actually "instantaneous (thus it is infinitely fast)", in the reference frame of the photon, if you can define such a frame.

Edit: And I make an appeal to bring the other 12 pages long thread back. Maybe trim it a bit, but a lot of science advisors spent a lot of their time and put a lot of effort in those posts. Just trim the crackpot posts and leave the others, don't delete the whole thread.
 
  • #4
One has to distinguish between coordinate time and proper time.

If you choose a particular Lorentz inertial coordinate system and use that to draw a spacetime diagram, a photon's wordline is a 45 degree line in spacetime, along which a photon does advance in coordinate space and coordinate time.

However, there is also proper time (or its analogue for null vectors). For a massive particle traveling less than the speed of light, the proper time is the time elapsed as read by an ideal clock traveling with the particle. However, for photons, this quantity is zero or null. This quantity being zero could be loosely said to mean that time does not pass for photons.

A property that is equivalent to photons traveling on null paths is that their speed is the same regardless of their wavelength. Hence two light waves traveling in the same direction with different frequencies will be "frozen" relative to each other. This could also be loosely said to mean that time does not pass for photons.
 
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  • #5
um0123 said:
Do photons experience time? If they move at the speed of light then special relativity states that they do not, but then does that mean they do not move forward in time which means the distance they travel is instantaneous (thus it is infinitely fast), which we know is not true (as they move at the speed c).

Furthermore, what happens when a photon ceases to exist? How does it cease to exist? Does it hit my body and 'poof' it is gone? what is process by which photons end their life.

Please start by reading the FAQ sub-forum in the Relativity forum.

Zz.
 
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Very sweet explanation atyy.
If I may add.

'Proper time' is just the time 'any/one/thing' finds itself to have locally as measured by its wrist watch. And for a 'photon' that 'time passed' should be null intrinsically, but not for us measuring its 'propagation'.
 
  • #8
"If they move at the speed of light then special relativity states that they do not ...": this is not true.
At any speed any object "experiences time".
The singularity of the Lorentz transformation only reflects how clocks can be compared, not the flow of time.
 
  • #9
lalbatros said:
At any speed any object "experiences time".

That's debatable. It might be about semantics and what exactly a particular person means by "experiences time".
Any object traveling with the speed of light (a massless particle) does not experience the flow of time.
 

1. What is a photon?

A photon is a fundamental particle of light and electromagnetic radiation. It is considered to be both a particle and a wave, and has zero mass and no electric charge.

2. How do photons interact with time?

According to the theory of relativity, time and space are intertwined and are affected by the presence of mass and energy. Photons do not experience time in the same way that we do, as they travel at the speed of light and do not age or decay.

3. What is the life-cycle of a photon?

The life-cycle of a photon is determined by its energy and wavelength. Some photons have a shorter life-span, such as those emitted by radioactive materials, while others can travel for billions of years and still retain their energy.

4. Can photons be destroyed?

Photons cannot be destroyed, as they are considered to be elementary particles and do not break down into smaller components. However, their energy can be absorbed or transferred to other particles, causing them to disappear from our observable universe.

5. How are photons used in technology?

Photons play a crucial role in many technologies, including telecommunications, solar panels, and medical imaging. They are also used in quantum computing and cryptography due to their ability to carry information and interact with matter in unique ways.

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