Time slows at the speed of light

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SUMMARY

The discussion centers on the effects of special relativity, specifically how time dilation occurs as one approaches the speed of light. A hypothetical scenario is presented where a traveler moves at light speed to Proxima Centauri while a stationary observer remains on Earth. The stationary observer ages 8.5 years during the journey, while the traveler experiences significantly less time due to the effects of time dilation, calculated using the formula √(1 - v²/c²). This illustrates the profound differences in time perception between stationary and moving observers in the context of special relativity.

PREREQUISITES
  • Understanding of special relativity principles
  • Familiarity with the concept of time dilation
  • Basic knowledge of the speed of light (c)
  • Ability to apply mathematical formulas related to velocity and time
NEXT STEPS
  • Research the implications of time dilation in GPS satellite technology
  • Explore the Lorentz transformation equations in special relativity
  • Study the effects of near-light-speed travel on aging and biological processes
  • Learn about Einstein's theory of relativity and its historical context
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Students of physics, educators teaching relativity, and anyone interested in the implications of high-speed travel on time perception.

DianaPrince
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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
 
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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:
 

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