[Seany (OP)]

I was just thinking.. But wouldn't it look like a loooooong path down? Because it just keeps reflecting and reflecting and reflecting and again.. and again..

[Seany (OP)]

Anyone kno about this one?

[another_someone]

That is the way they do experiments to measure the speed of light, by creating a very long light path using parallel mirrors almost perpendicular to the light source.

The reason why they must be almost perpendicular to the light source, rather than truly perpendicular, is that you have to have a way of introducing the light to the mirrors (and you also want an end point where to measure the light), so the light path still requires an start point and an end point that is outside of the mirrors.  If the mirrors were perpendicular to the light, you could have neither a start point, nor and end point, for the light path.

[Seany (OP)]

Haha yeah. Thanks. So they make it a fraction fraction fraction fraction from parallel, so that they go miles before they reach the end point, right?

[another_someone]

Haha yeah. Thanks. So they make it a fraction fraction fraction fraction from parallel, so that they go miles before they reach the end point, right?

Yes, except, I'm sorry, what I got wrong was that it is not that the mirrors are not parallel, but the the light path is not perpendicular to them - I have now corrected that.

[Seany (OP)]

Ohhhh.. Yep, that makes more sense. [] So the first light ray which they send is at like 89.9999 degrees from the mirror. Kk Thanks []

So what cool experiences would you have? Just a loooooong tunnel?

[neilep]

George...this is very interesting....what measure of distance do they obtain measuring the speed of light like this ?

[neilep]

............and why do they need to check for the speed of light anyway.....it's 'C'  isn't it ?

[Seany (OP)]

Whats the 'C'?

[Seany (OP)]

Oh constant? Yes.. But maybe when they first found out about light.. They needed this to measure the speed of it.

[Batroost]

Just to make things a bit tricker...

The meter is defined in terms of the speed of light i.e. it was redefined in 1983 as the distance traveled by light in a vacuum in 1/299,792,458 of a second.

So when people make highly accrate measurements of the 'speed of light' they are really setting an accurate length scale...

[neilep]

Just to make things a bit tricker...

The meter is defined in terms of the speed of light i.e. it was redefined in 1983 as the distance traveled by light in a vacuum in 1/299,792,458 of a second.

So when people make highly accrate measurements of the 'speed of light' they are really setting an accurate length scale...

Ah !!..this is great..THANK YOU Batroost and welcome to the forum !

So, in this case the speed of light is used as a calibration tool...a measuring device !!..excellent !!

Thanks

[Seany (OP)]

Oh, so it's like a new measurement?