Is it possible? (faster than light in a medium)

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Discussion Overview

The discussion revolves around the possibility of traveling faster than the speed of light in a medium, specifically in water. Participants explore the implications of light speed in different media and the conditions under which one might exceed this speed.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants assert that the speed of light in a vacuum is the ultimate speed limit, while light in a medium like water travels at c/n, suggesting that running faster than c/n could imply exceeding light speed.
  • Others argue that while one cannot run faster than the speed of light in water, there could be hypothetical materials with a refractive index that allows light to travel at an apparent speed less than running speed.
  • A participant introduces the concept of Cherenkov radiation, noting that if an electron moves faster than the speed of light in water, it emits this radiation, which is a phenomenon that has been observed.
  • There is a repeated assertion about the speed of light in water and the conditions under which one might exceed it, with some participants questioning the feasibility of running faster than c/n.

Areas of Agreement / Disagreement

Participants do not reach a consensus; multiple competing views remain regarding the implications of traveling faster than light in a medium and the conditions under which this might occur.

Contextual Notes

Some statements depend on specific definitions of speed in different media and the assumptions about hypothetical materials. The discussion includes unresolved questions about the nature of light speed and its implications in various contexts.

IPhO' 2008
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If we have a tank which full of water.Then,emitted the light into the tank.The speed of light is c/n . If we can run faster than c/n. We will run faster than light.
Is it possible?
 
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Yes, the impossibility of traveling faster than light only applies to the speed of light in a vacuum.
 


IPhO' 2008 said:
If we have a tank which full of water.Then,emitted the light into the tank.The speed of light is c/n . If we can run faster than c/n. We will run faster than light.
Is it possible?

You are gauging the speed of light I assume from one medium to another.

It will max out at c.
 


Well, we can't run faster than the speed of light in water, but hypothetically, if there is a material with a refractive index that causes light to travel at an apparent speed less than running speed, we could run faster.
 


russ_watters said:
Well, we can't run faster than the speed of light in water, but hypothetically, if there is a material with a refractive index that causes light to travel at an apparent speed less than running speed, we could run faster.

http://www.news.harvard.edu/gazette/1999/02.18/light.html
 


IPhO' 2008 said:
If we have a tank which full of water.Then,emitted the light into the tank.The speed of light is c/n . If we can run faster than c/n. We will run faster than light.
Is it possible?

Instead of us running, use an electron moving through the water. If the election moves faster that the speed of light in the water, Cerenkov radiation is emitted. This radiation is routinely observed.

http://en.wikipedia.org/wiki/Cherenkov_radiation
 
Thread title edited. Please make thread titles specific to begin with.
 
We can run faster than c/n in lab,but we can't run faster than c/n in the water.
Right?
 

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