# Fibre Optic particle accelerator

• November 14th, 2011, 11:21 AM
Aristarchus in Exile
Fibre Optic particle accelerator
Drill a small borehole a few miles towards the centre of the earth. Hollow a fibre optic strand to particle size. Hang the thread straight down the borehole. Insert a particle into the centre of the strand. Shine light into the strand. Will the photons accelerate the particle? Will the particle, because of relativity, no matter how fast it goes, even close to C, see the photons ahead of it as travelling at C, allowing the particle C amount of acceleration?

The strand is not laid horizontal to avoid the effects of gravity distorting the particle's path.
• November 14th, 2011, 12:30 PM
Janus
Quote:

Originally Posted by Aristarchus in Exile
Drill a small borehole a few miles towards the centre of the earth. Hollow a fibre optic strand to particle size. Hang the thread straight down the borehole. Insert a particle into the centre of the strand. Shine light into the strand. Will the photons accelerate the particle?
If you just drilled a hole there will likely be some bleed over from the fiber to hole that will provide some momentum transfer to the particle

Will the particle, because of relativity, no matter how fast it goes, even close to C, see the photons ahead of it as travelling at C, allowing the particle C amount of acceleration?

1. light does not travel at c in a fiber optic cable but closer to 0.66c. That being the case, the particle would see the light travel ahead of it at

So for example if the particle was moving at 0.5c relative to the optic cable, it would see the light travel at 0.24c. Remember it is not light that is special, it is the speed c. Since the light does not travel at c in the cable, you cannot claim that everyone will measure it speed to be the same.

2. Even if we use light traveling in a vacuum at c ( for example, with a light sail), even thought the sail will always measure the light as traveling at c relative to itself now matter how fast it is moving relative to the source, the momentum and energy of that light hitting the sail will drop off. This is because the light will be more and more red shifted as the sail moves faster and faster away from the source. Since the frequency decreases as measured by the sail, so the does the momentum and the light pressure. The frequency and momentum will approach zero as the sails speed approaches c.
Quote:

The strand is not laid horizontal to avoid the effects of gravity distorting the particle's path.
• November 14th, 2011, 01:40 PM
Aristarchus in Exile
Janus .. your tone and information sets this forum apart from all others. Thanks.