Why don't photons experience time?

In summary, Einstein tried to imagine what an electromagnetic wave would look like from the point of view of a motorcyclist riding alongside it, but found that it didn't make sense. There are two ways that the velocity of the system's center of mass could be: it could be moving at the speed of light, or it couldn't. If V=c, then all the particles are moving along parallel lines, and therefore they can't interact, can't perform computations, and can't be conscious. If V is less than c, then the observer's frame of reference isn't moving at the speed of light.
  • #141
PeterDonis

Because c dt = dl. Look at the two events I wrote down:

(0, 0, 0, 0) and (1000, 1000, 0, 0)

I used units where c = 1, so we have dt = 1000 and dl = 1000; the interval is null because the two are equal.


very helpful insight...I had forgotten the distinction between a null interval in space versus a null interval in space-time...

a nice brief discussion here for others who may be learning:

http://en.wikipedia.org/wiki/Spacetime_interval#Spacetime_intervals


and also 'null events of a photon' trace out a lightcone...illustration here,
in flat space-time

http://en.wikipedia.org/wiki/Light-cone

This kind of light-cone has some characteristics of null surfaces in cosmological,
also accelerated, horizons, right??
 
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  • #142
Naty1 said:
This kind of light-cone has some characteristics of null surfaces in cosmological, also accelerated, horizons, right??

Light cones are null surfaces, and all null surfaces have properties in common, yes.
 
<h2>1. What is the concept of time dilation in relation to photons?</h2><p>Time dilation is a phenomenon in which time appears to pass at different rates for objects moving at different speeds. In the case of photons, which travel at the speed of light, time appears to stand still for them because they are moving at the maximum possible speed. This means that photons do not experience time in the same way that we do.</p><h2>2. How does Einstein's theory of relativity explain why photons do not experience time?</h2><p>Einstein's theory of relativity states that the laws of physics are the same for all observers, regardless of their relative motion. This means that no matter how fast an observer is moving, they will always measure the speed of light to be the same. Since photons travel at the speed of light, they do not experience time because they are always moving at the maximum speed and cannot be observed from a different frame of reference.</p><h2>3. Can photons be affected by gravity if they do not experience time?</h2><p>Yes, photons can be affected by gravity. According to Einstein's theory of general relativity, gravity is the curvature of space and time caused by the presence of mass. Since photons have energy and momentum, they can be affected by the curvature of space and time, which is why they can be bent by gravitational fields.</p><h2>4. Do all particles that travel at the speed of light not experience time?</h2><p>No, photons are the only particles that travel at the speed of light. While other particles, such as neutrinos, can approach the speed of light, they still have mass and therefore do experience time. Only particles with no mass, like photons, can travel at the speed of light and not experience time.</p><h2>5. How does the concept of timelessness for photons impact our understanding of the universe?</h2><p>The concept of timelessness for photons challenges our understanding of the universe and the nature of time itself. It suggests that time is not a universal constant and can be influenced by factors such as speed and gravity. This has implications for our understanding of space-time and how the universe operates on a fundamental level.</p>

1. What is the concept of time dilation in relation to photons?

Time dilation is a phenomenon in which time appears to pass at different rates for objects moving at different speeds. In the case of photons, which travel at the speed of light, time appears to stand still for them because they are moving at the maximum possible speed. This means that photons do not experience time in the same way that we do.

2. How does Einstein's theory of relativity explain why photons do not experience time?

Einstein's theory of relativity states that the laws of physics are the same for all observers, regardless of their relative motion. This means that no matter how fast an observer is moving, they will always measure the speed of light to be the same. Since photons travel at the speed of light, they do not experience time because they are always moving at the maximum speed and cannot be observed from a different frame of reference.

3. Can photons be affected by gravity if they do not experience time?

Yes, photons can be affected by gravity. According to Einstein's theory of general relativity, gravity is the curvature of space and time caused by the presence of mass. Since photons have energy and momentum, they can be affected by the curvature of space and time, which is why they can be bent by gravitational fields.

4. Do all particles that travel at the speed of light not experience time?

No, photons are the only particles that travel at the speed of light. While other particles, such as neutrinos, can approach the speed of light, they still have mass and therefore do experience time. Only particles with no mass, like photons, can travel at the speed of light and not experience time.

5. How does the concept of timelessness for photons impact our understanding of the universe?

The concept of timelessness for photons challenges our understanding of the universe and the nature of time itself. It suggests that time is not a universal constant and can be influenced by factors such as speed and gravity. This has implications for our understanding of space-time and how the universe operates on a fundamental level.

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