Time & Speed of Light: Not a Universal Constant

In summary, time is not a universal constant and can vary based on the speed of bodies and the distance between them. However, individual clocks will always tick at a constant rate regardless of state of motion. The concept of time as we perceive it can also be influenced by the relativistic Doppler effect, but this is not dependent on distance.
  • #1
Shubh Goel
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TL;DR Summary
Assumption travelling at speed of light is possible.
1. We are in empty space. I am travelling backwards(I am facing the direction opposite to my direction of motion) at half the speed of light. My other friend is travelling in opposite direction with the same speed being backward. If i look in the direction of my friend, i will see him getting slower and slower as we move apart even though relative velocity between us is still the same.
Time as we perceive is not a universal constant. It depends on the speed of the bodies and the distance between them.
 
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  • #2
Shubh Goel said:
Assumption traveling at speed of light is possible.
It isn't - it's prohibited by the postulates of relativity.
Shubh Goel said:
I am traveling backwards(I am facing the direction opposite to my direction of motion) at half the speed of light. My other friend is traveling in opposite direction with the same speed being backward.
Travelling at those speeds with respect to what? In what follows I'm assuming that you are specifying both speeds with respect to some common reference.
Shubh Goel said:
If i look in the direction of my friend, i will see him getting slower and slower as we move apart even though relative velocity between us is still the same.
No - you will always see him moving at constant velocity, 80% of the speed of light (in relativity velocities do not add the same way as they do in Newtonian physics). You will see his clocks ticking at a constant rate, albeit slower than your own.
Shubh Goel said:
Time as we perceive is not a universal constant. It depends on the speed of the bodies and the distance between them.
This depends a lot on what you mean by "time as we perceive it". Your own wristwatch, for example, will always tick at the same rate whatever your state of motion. Other people's watches may well tick at different rates as measured by you, but they would have the opposite opinion about whose watch is ticking normally and whose is ticking slowly.

Clock rates do not depend on distance, though. I suspect you have misunderstood something around the relativistic Doppler effect. It's fairly easy to show that you will see your friend's watch ticking at a constant rate of once every three seconds. The general formula for someone receding from you at speed ##v## is that their clock ticks once every $$\sqrt{\frac{c+v}{c-v}}$$seconds. If you correct for the increasing light travel time, you will calculate a tick rate of once every ##(1-v^2/c^2)^{-1/2}## seconds, which turns out to be once for every 1.67 ticks of your watch in your scenario. Neither of these formulae depend on the distance between you.
 
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  • #3
The OP is based on a misunderstanding of relativity, which has been explained. Thread closed.
 
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1. What is the speed of light?

The speed of light is a fundamental constant in physics, denoted by the letter c. In a vacuum, it is approximately 299,792,458 meters per second (m/s). This means that light travels about 186,282 miles per second.

2. Is the speed of light constant?

No, recent research has shown that the speed of light is not a universal constant. It can vary depending on the medium through which it is traveling, such as air, water, or glass. This is known as the refractive index of the medium.

3. How does time relate to the speed of light?

Einstein's theory of relativity states that time is relative and can be affected by the speed of light. As an object approaches the speed of light, time slows down for that object. This phenomenon is known as time dilation.

4. Can the speed of light be exceeded?

Based on our current understanding of physics, it is impossible for any object to travel at or above the speed of light. As an object approaches the speed of light, its mass increases exponentially, making it more and more difficult to accelerate further.

5. How does the variability of the speed of light impact our understanding of the universe?

The variability of the speed of light has significant implications for our understanding of the universe. It challenges the notion of a universal constant and requires us to reevaluate our current models and theories. It also opens up new possibilities for studying the behavior of light and its interactions with matter.

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