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Everything Space => Astronomy Clubs and Events => Ask an Astronomer => Topic started by: gcks on February 28, 2005, 10:56:04 PM


Title: Speed of light
Post by: gcks on February 28, 2005, 10:56:04 PM
How did we achieve to measure the speed of light?

Title: Re: Speed of light
Post by: Astronuc on March 01, 2005, 06:24:42 AM
Quote
During the 1670's, the Danish astronomer Ole Roemer was making extremely careful observations of Jupiter's moon Io. The black dot is Io's shadow. Io makes one complete orbit around Jupiter every 1.76 days; the time it takes to make each orbit is always the same, so Roemer expected that he could predict its motion quite precisely. To his astonishment, he discovered that the moon didn't always appear where it was supposed to be. At certain times of the year, it seemed to be slightly behind schedule; at other times, it was slightly ahead.

Roemer noticed that Io seemed to be ahead of its predicted orbit when the earth was closer to Jupiter, and behind when it was farther away.  Knowing how much Io's timing seemed to change and how much the distance from earth to Jupiter varied, Roemer was able to calculate a value for the speed of light. The number he came up with was about 186,000 miles per second, or 300,000 kilometers per second.
from http://www.colorado.edu/physics/2000/waves_particles/lightspeed_evidence.html

Albert Michelson made some precise measurements of the speed of light in 1931. 

Here is site with some nice background.

http://www.sigma-engineering.co.uk/light/lightindex.shtml

Title: Re: Speed of light
Post by: gcks on March 06, 2005, 04:15:16 AM
Is there any astronomical proof of exceeding the speed of light?

Title: Re: Speed of light
Post by: Orstio on March 06, 2005, 09:34:44 AM
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Is there any astronomical proof of exceeding the speed of light?

No.

Title: Re: Speed of light
Post by: gcks on March 07, 2005, 03:45:05 AM
Is it possible to exceed the speed of light ? (I have read something about "worm holes", could that be possible ? )

Title: Re: Speed of light
Post by: gcks on March 07, 2005, 03:47:06 AM
and what about particles that (it is said) exceed the speed of light ? How did they manage to detect them?

Title: Re: Speed of light
Post by: Orstio on March 07, 2005, 04:26:42 AM
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Is it possible to exceed the speed of light ? (I have read something about "worm holes", could that be possible ? )

Within our current knowledge of physics, it is impossible for anything to accelerate beyond the speed of light.

Wormholes do not accelerate anything beyond the speed of light, they circumvent the space-time continuum.

Quote
and what about particles that (it is said) exceed the speed of light ? How did they manage to detect them?

These would be speculative virtual particles.  None have yet been detected.


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