Speed of light is set to be 299,792,458 m/s

Click For Summary

Discussion Overview

The discussion revolves around the speed of light, specifically the implications of time dilation and length contraction as one approaches the speed of light. Participants explore how these relativistic effects influence the measurement of light's speed from different reference frames.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants question how the speed of light can be measured as constant at 299,792,458 m/s if time slows as one approaches that speed.
  • Others argue that all observers, regardless of their relative motion, will measure the speed of light as 299,792,458 m/s, and that time dilation is experienced differently by observers in different frames.
  • It is noted that length also contracts when approaching the speed of light, reinforcing the idea that the speed of light remains constant across reference frames.
  • One participant expresses confusion about the relativity of time, suggesting that if time appears to slow down for someone moving close to the speed of light, it complicates the measurement of their speed.
  • Another participant emphasizes the first postulate of Special Relativity, stating that there is no absolute motion and that time is relative, not variable.

Areas of Agreement / Disagreement

Participants express differing views on the implications of time dilation and the nature of measuring speed in relativistic contexts. The discussion remains unresolved, with multiple competing interpretations of how time and speed relate in different frames.

Contextual Notes

Participants highlight the complexity of measuring speed and time in relativistic scenarios, noting that assumptions about time and motion can lead to confusion. The discussion does not resolve these complexities.

MaoIragorri
Messages
6
Reaction score
0
I have a question...
The speed of light is set to be 299,792,458 m/s
but if time slows as you approach the speed of light,
how can we tell how fast Light itself is actually traveling?
 
Science news on Phys.org


MaoIragorri said:
I have a question...
The speed of light is set to be 299,792,458 m/s
but if time slows as you approach the speed of light,
how can we tell how fast Light itself is actually traveling?

As you approach c relative to some external reference frame, you do not experience a time dilation, you experience time passing normally. But the observers in that external reference frame experience your time as increasingly attenuated.


All observers - on the spaceship and off it regardless of their speed with respect to each other - will measure the speed of light as 299,792,458 m/s.

There are many searchable posts on this forum that go into it in more detail.
 


Length also contracts when approaching the speed of light. Relativistically speaking, the speed of light is constant in all reference frames; measurement of it shouldn't change from one frame to another.
 


yeah, but the are all external references...
if time starts to slow down around you, then a second becomes elongated...
to people around you the second might remain a second, but if to you the second becomes, let's say an hour... how fast are you moving per second.

does this make sense?
 


MaoIragorri said:
does this make sense?
No.

The first postulate of Special Relativity is that the laws of the universe are the same for any inertial (non accelerating) observer. What this means here is that there is no experiment you can perform to distinguish an absolute motion. You may be stationary with respect to one outside observer, moving at 1,000 mph with respect to another and moving at 10,000 mph with respect to another. And all 3 of these observers (and you) can consider themself stationary and measure the speed of light to be C in their frame.

Don't say "if time starts to slow down around you" - that's nonsensical. You never see any change in your clock, but your clock runs at one rate for you, another rate with respect to the clock of that guy moving at 1,000 mph and yet another rate wrt the guy moving at 10,000 mph. Time isn't variable, it is relative.
 


Briliant, thanks all.
 

Similar threads

High School Help with refraction of light
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad What will stop me from going at the speed of light?
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Speed of Light when not in a vacuum?
  • · Replies 5 ·
Replies
5
Views
6K
Undergrad Ships passing each other at near light speed
  • · Replies 5 ·
Replies
5
Views
702
High School Speed of light versus wavelength
  • · Replies 14 ·
Replies
14
Views
2K
Graduate Is 299,792,458 m/s really the max speed of light
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Measuring the speed of light in a straight line
  • · Replies 19 ·
Replies
19
Views
2K
Undergrad Achieving the speed of light at the end of a whip
  • · Replies 15 ·
Replies
15
Views
6K
Graduate Why does the speed of light change in different media?
  • · Replies 4 ·
Replies
4
Views
4K
Undergrad How was the speed of light calculated before the redefinition of the meter?
  • · Replies 8 ·
Replies
8
Views
4K