Can You Travel Faster Than Light According to Physics?

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Discussion Overview

The discussion revolves around the concept of traveling at relativistic speeds, specifically addressing the implications of time dilation and length contraction as experienced by observers in different reference frames. Participants explore the scenario of a spaceship traveling at 0.95 times the speed of light towards Alpha Centauri, examining the perceived speed of objects and the effects of relativistic physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether a traveler on a spaceship moving at 0.95 times the speed of light would perceive themselves traveling faster than light when considering time dilation and the distance to Alpha Centauri.
  • Another participant clarifies that the traveler would not see adjacent objects passing by at speeds exceeding light, but rather at 0.95 times the speed of light, due to the principles of relativity.
  • The same participant notes that the traveler would experience length contraction, leading to a shorter perceived distance to Alpha Centauri in their reference frame.
  • A third participant acknowledges the concept of length contraction but does not elaborate further.

Areas of Agreement / Disagreement

Participants generally agree on the principles of time dilation and length contraction, but the initial confusion regarding perceived speeds indicates that there may still be some misunderstanding of these concepts.

Contextual Notes

The discussion highlights the complexities of relativistic effects, including the dependence on reference frames and the implications of measuring distances and speeds at relativistic velocities. Some assumptions about the nature of light speed and perception may remain unresolved.

Who May Find This Useful

This discussion may be useful for individuals interested in the fundamentals of special relativity, particularly those exploring the implications of traveling at relativistic speeds and the associated effects on time and space perception.

kairama15
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Consider this, and tell me where my thinking goes wrong. I'm confused.

There is a person observing a spaceship launch from earth, and another person on the spaceship. There are space rocks and asteroids stationary with respect to the Earth for the spaceship to observe as it flies.
The person on Earth watches as the spaceship quickly accelerates to 0.95% the speed of light.
The person on Earth watches the spaceship go to alpha centauri which we'll say is 4 lightyears away.
So it takes 4 lightyears / 0.95 = 4.2 years for him to see the spaceship get there.

However, on the spaceship going that fraction of the speed of light, time goes slower and it only takes him 1.24 years in his reference frame to get there. So, does that mean he'll feel like he's going 4 lightyears/1.24 years = 3.2 times the speed of light? For example, will he see adjacent objects like asteroids and space rocks fly by him at 3.2 times the speed of light? He knows that alpha centauri is 4 light years away but he'll get there in 1.24 years. Surely I'd be confused if I calculated I went faster than the speed of light... Where is my thought process going wrong? Or is this what would actually happen to someone traveling that quickly?
 
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kairama15 said:
will he see adjacent objects like asteroids and space rocks fly by him at 3.2 times the speed of light?

No. He will see them fly by at 0.95 percent of the speed of light.

kairama15 said:
He knows that alpha centauri is 4 light years away but he'll get there in 1.24 years.

He will get there in 1.24 years by his clock, because he will see the distance between him and alpha centauri length contracted to a little less than 1.24 light years.
 
Length contraction!

(Ugh, Peter beat me)
 
I see. thank you
 

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