Time slows at the speed of light

In summary, the conversation discusses the concept of special relativity and the effects it has on time for individuals traveling at the speed of light. The question is posed about how to determine the amount of time that has elapsed for a person traveling at this speed, and whether their perception of time is different from a stationary observer. The conversation also brings up the scenario of a round-trip journey at the speed of light and how time would be perceived by the traveler.
  • #1
DianaPrince
1
0
Hi,
I am not exactly sure how to present this question. Even thinking about it creates some confusion,so I will only try my best. My question is about special relativity. Since the first time I saw Carl Sagan's Cosmos series, I have been fascinated by this, but still don't totally get it. I can accept as fact that time slows down as you approach the speed of light, but actually understanding this presents a whole different problem.

If for example time elapses differently for a stationary observer than it does for someone traveling at the speed of light, how can we determine how much time has elapsed? Suppose I am standing with a friend in an open field. My friend takes a round trip ride from Earth to the sun at the speed of light (let's just pretend that he didn't get burnt to a crisp). Once he leaves my side in his imaginary spacecraft , I stand there waiting for him to return, which should only take about 16 minutes (round-trip). What will I notice when he returns? Is the amount of time that he was gone different for him than it was for me? For how long (stationary-earth-time) must he travel at the speed of light in order for there to be a visible difference in the aging process once we meet back up? If we as humans are accustomed to time passing at a very particular rate, what experience does the person traveling at the speed of light have? For example, he goes on a speed-of-light-journey let's say to Proxima Centauri. I sit around waiting for 8 1/2 years for him to get there and back. Does he feel as if he were only on a short journey? If so, according to his clock and his perception of elapsed time, how long did his journey last - for him? I hope I made my question clear. Any answers or additional info to help me understand this would be appreciated.
Jasmin
 
Physics news on Phys.org
  • #2
Welcome to PF!

Hi Jasmin! Welcome to PF! :smile:
DianaPrince said:
… Once he leaves my side in his imaginary spacecraft , I stand there waiting for him to return, which should only take about 16 minutes (round-trip). What will I notice when he returns?

Nothing … he can't get any younger, and you'll only be 16 minutes older! :smile:
If we as humans are accustomed to time passing at a very particular rate, what experience does the person traveling at the speed of light have? For example, he goes on a speed-of-light-journey let's say to Proxima Centauri. I sit around waiting for 8 1/2 years for him to get there and back. Does he feel as if he were only on a short journey?

If he goes on an almost-speed-of-light-journey, then everything seems normal to him (apart of course from the immense g-forces at the start the turn-round and the finish!), and yes he feels as if he were only on a short journey. :smile:
If so, according to his clock and his perception of elapsed time, how long did his journey last - for him?

Depends how close he was to the speed of light … could even be less than a nano-second …

The precise factor is √(1 - v²/c²), so the closer v is to c, the slower his time is. :smile:
 
  • #3


Hi Jasmin, thank you for your question and for sharing your fascination with special relativity. It can definitely be a difficult concept to wrap our minds around, but I'll do my best to provide some insight.

First, it's important to understand that time dilation (the slowing of time) is a consequence of the theory of special relativity. This theory states that the laws of physics are the same for all observers in uniform motion, regardless of their relative velocities. This means that there is no absolute frame of reference, and all motion is relative.

Now, to answer your specific questions: when your friend travels at the speed of light, he will experience time passing at a slower rate compared to you as the stationary observer. This means that for every second that passes for you, less time will have passed for him. So, if he takes a round-trip journey to the sun at the speed of light, he will experience less time passing compared to you waiting for him on Earth.

As for how much time he needs to travel at the speed of light for there to be a noticeable difference in the aging process, it's not a specific amount of time but rather a difference in velocities. The closer he travels to the speed of light, the greater the time dilation effect will be.

For your example of traveling to Proxima Centauri, if your friend were to travel at the speed of light, he would experience the journey as taking only a few seconds. However, for you as the stationary observer, 8 1/2 years would have passed. This is because the speed of light is the fastest speed possible, and as an object approaches it, time slows down for that object.

It's important to note that this time dilation effect is only noticeable at extremely high velocities, such as the speed of light. For everyday speeds, the difference in time experienced by moving objects is negligible.

I hope this helps to clarify some of your questions about special relativity. It's a fascinating concept, and it's always great to see people curious and wanting to understand it better. Keep exploring and learning, and you'll continue to gain a deeper understanding of this mind-boggling theory.
 

What is the concept of time slowing at the speed of light?

The concept of time slowing at the speed of light is based on Einstein's theory of relativity. According to this theory, time is relative and can be affected by the speed at which an object is moving. As an object approaches the speed of light, time slows down for that object in relation to an observer who is not moving at that speed.

How does this phenomenon occur?

This phenomenon occurs because as an object approaches the speed of light, its energy increases and its mass also increases. This causes a distortion in the fabric of space and time, resulting in time appearing to slow down for the object in motion.

Why does time slow down at the speed of light?

Time slows down at the speed of light because of the constant speed of light in a vacuum. According to Einstein's theory, the speed of light is the fastest possible speed in the universe and therefore, the closer an object gets to this speed, the slower time will appear to pass for that object.

Can time actually stop at the speed of light?

No, time cannot actually stop at the speed of light. According to Einstein's theory, time will continue to slow down as an object approaches the speed of light, but it will never come to a complete stop. However, for an observer, time may appear to have stopped for an object moving at the speed of light.

What are the implications of this phenomenon?

The implications of time slowing at the speed of light are significant for our understanding of the universe. It has been observed and measured in experiments, and it has led to a better understanding of space, time, and the relationship between the two. It also has implications for space travel and the concept of time travel.

Similar threads

  • Special and General Relativity
Replies
7
Views
1K
  • Special and General Relativity
Replies
20
Views
1K
  • Special and General Relativity
Replies
4
Views
180
  • Special and General Relativity
Replies
18
Views
1K
  • Special and General Relativity
Replies
12
Views
2K
  • Special and General Relativity
Replies
2
Views
315
  • Special and General Relativity
2
Replies
45
Views
3K
  • Special and General Relativity
2
Replies
51
Views
2K
  • Special and General Relativity
Replies
9
Views
1K
  • Special and General Relativity
Replies
20
Views
1K
Back
Top