How fast is a relativistic velocity?

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    Relativistic Velocity
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Discussion Overview

The discussion revolves around the concept of "relativistic velocity" and seeks to determine at what speed an object is considered to be moving at a relativistic velocity. Participants explore the implications of relativistic effects, particularly time dilation, across various speeds and contexts.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that relativistic velocity might be considered at speeds like 0.1c or 0.5c.
  • Another participant argues that relativistic effects, such as time dilation, occur at all speeds, even as low as 3 mph, questioning when these effects become significant.
  • A participant agrees that 0.1c is where relativistic effects become considerable but acknowledges the subjective nature of the threshold.
  • It is noted that GPS satellites operate at relativistic speeds, implying that time dilation must be accounted for to maintain accuracy, while everyday speeds (e.g., 60 kph) may not require such considerations.
  • A mathematical expression for gamma (\(\gamma\)) is provided, suggesting that when instruments can distinguish \(\gamma\) from 1.0, relativistic effects should be considered.
  • Another participant reiterates that the relevance of relativistic speed depends on the specific situation, indicating that a fixed speed threshold may be insufficient.

Areas of Agreement / Disagreement

Participants express differing views on what constitutes a relativistic velocity, with no consensus on a specific speed threshold. The discussion highlights the subjective nature of defining relativistic effects based on context and application.

Contextual Notes

Participants mention various speeds and contexts (e.g., GPS satellites versus everyday vehicles) without resolving the implications of these examples on the definition of relativistic velocity. The discussion reflects a range of assumptions about the significance of relativistic effects at different speeds.

whydoyouwanttoknow
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How fast do you have to be going before you would be said to have a relativistic velocity?
 
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Obviously it's subjective, but 0.1c perhaps or even 0.5c?
 
The dilations happen at all speeds, even 3 mph. The question is when does the size of the dilations become of interest to you?
 
selfAdjoint is right, but I say at 0.1c is where is comes into considerable effect.
 
selfAdjoint said:
The dilations happen at all speeds, even 3 mph. The question is when does the size of the dilations become of interest to you?

So your average GPS sat. is going at a relativistic speed because if you didn't take time dilation into account they'd give you the wrong position? But for the rest of us who cares that our car is going 60kph?
 
Calculate [tex]\gamma=\frac{1}{\sqrt{1 - \left(\frac{v}{c}\right) ^2}}[/tex].
When your instruments can distinguish [itex]\gamma[/itex] from 1.0 [for example, with a very accurate clock], then you may consider the problem to require relativistic considerations.
 
whydoyouwanttoknow said:
So your average GPS sat. is going at a relativistic speed because if you didn't take time dilation into account they'd give you the wrong position? But for the rest of us who cares that our car is going 60kph?
Yep. So even saying .1C is incomplete: it depends on the situation.
 

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