Time Dilation & Length Contraction: Does Relativity Work for Mediums?

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Discussion Overview

The discussion revolves around the applicability of relativity, specifically time dilation and length contraction, in different mediums such as air and water. Participants explore whether the speed of light in a vacuum (c) should be used in calculations involving these phenomena in mediums.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks whether relativity applies to mediums and if c should be the speed of light in a vacuum or in the medium.
  • Another participant asserts that relativity still holds in a medium, emphasizing that c remains the invariant speed regardless of the medium.
  • A further contribution clarifies that c in the Lorentz transforms is an invariant quantity, reinforcing that it is the speed of light in a vacuum that should be used.
  • There is a query about the existence of particles traveling faster than c, with one participant stating that nothing travels faster than c, referencing past confusion regarding neutrinos.
  • Participants mention tachyons as hypothetical faster-than-light particles, noting their lack of detection and uncertain theoretical status.
  • Some participants humorously engage in banter about their own "speeds" in relation to c.

Areas of Agreement / Disagreement

While there is general agreement that c is the speed of light in a vacuum and should be used in relativity equations, there are competing views regarding the existence of faster-than-light phenomena, particularly in the context of hypothetical particles like tachyons.

Contextual Notes

Participants express uncertainty about the implications of speeds exceeding c in mediums and the status of tachyons, indicating a lack of consensus on these points.

Mohammed Ayaz Quadri
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Hello I am new here and I am just Junior college student. So please use simpler terms. I need to know that does relativity work for mediums like air and water. I mean the equations of time dilation and length contraction, do they work for other mediums. If so shall I take C as the speed of light in vacuum or thr speed at that particular medium? Thank You.
 
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Hi Mohammed, welcome to PF!

Relativity still works in a medium, and the c that you use is the speed of light in vacuum. The invariant speed is not changed inside a medium.

In fact, inside a medium, particles may exceed the speed of light in the medium as long as they do not exceed c.
 
To expand slightly on what Dale said, the quantity c in the Lorentz transforms and length contraction and time dilation formulae is an invariant quantity that is the same everywhere for everyone. It also happens to be the speed at which light travels in a vacuum. That's not actually a coincidence, but as far as relativity is concerned it's just an interesting fact.

So that means you always use c in the Lorentz transforms, not whatever the speed of light is in whatever medium you happen to be in.
 
Ty everyone. I didnt expected so quick answers. Can you help with this: I have heard that very few things found are traveling at a speed more that c. How far is this true? Ty
 
Nothing travels faster than c.

There was some brief confusion about neutrinos, but it turned out that there was a loose cable in the experiment's time recording apparatus. And there are purely hypothetical particles called tachyons, but they've never been detected. I should point out that I don't even know if there's a respectable theory that predicts tachyons, or if they're just science fiction. You do sometimes see them mentioned, though.

Edit: as Dale said, things can exceed the speed of light in a medium (look up Cerenkov radiation, which is a side-effect of this). But nothing exceeds c.
 
Mohammed Ayaz Quadri said:
Ty everyone. I didnt expected so quick answers. Can you help with this: I have heard that very few things found are traveling at a speed more that c. How far is this true? Ty
NOTHING travels at more than c. Period.

EDIT: Ibix beat me to it.
 
phinds said:
EDIT: Ibix beat me to it.
My reply speed gets close to c. :wink:
 
Ibix said:
My reply speed gets close to c. :wink:
You can increase it by dieting until you are massless! ;)
 
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Ibix said:
My reply speed gets close to c. :wink:
And my brain is often in a vacuum, so together we've got it covered.
 
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  • #10
Ty. Everyone is very helpful here. Some interesting conversation going on, eh?
 

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