# The Naked Scientists Forum

### Author Topic: Can we control the speed of light?  (Read 3293 times)

#### The Scientist

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##### Can we control the speed of light?
« on: 19/07/2010 12:43:40 »
We know that the speed of light is 299,792,458 metres per second. But are there any  ways of controlling the speed of light? Please share your views with us. Thanks!

#### imatfaal

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##### Can we control the speed of light?
« Reply #1 on: 19/07/2010 15:05:37 »
that's the speed in a vacuum.  you can 'control' it by sending it through another medium; the ratio of speed in a vacuum to the speed in a medium is called the refractive index.  the refractive index of glass is about 1.5 - so every time you shine a light through glass you are making it drop to around 200,000,000 m/s.  some materials lower the speed of light to practically pedestrian speeds - upon checking wikipedia it seems that a bose-enstein condensate of rubidium can halt light in the correct circumstances!
Matthew

#### syhprum

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##### Can we control the speed of light?
« Reply #2 on: 19/07/2010 17:33:38 »
I say this with tongue in cheek but is it not slowed down by strong gravitational fields such as exist close to Neutron stars and black holes

#### LeeE

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##### Can we control the speed of light?
« Reply #3 on: 19/07/2010 18:49:59 »
As far as I understand, light is not slowed by strong gravitational fields, but because of the gravitational curvature of space there may be 'more' space for it to travel through in the vicinity of a gravity well.

When viewed by a distant observer, in flatter space and who is measuring the speed by the rate of angular displacement, it might appear to slow down as it approaches the gravity well.

#### syhprum

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##### Can we control the speed of light?
« Reply #4 on: 19/07/2010 19:49:42 »
Yes I realise what is the reason when I stop to think before typing.
The light moves at its normal speed but takes a longer path dipping into the gravitational well.

#### The Naked Scientists Forum

##### Can we control the speed of light?
« Reply #4 on: 19/07/2010 19:49:42 »