Quiz time

[Kris.Parker1]

Thanks for that. On the same note, why when water is clear does is turn white when it is frozen (eg Ice Berg)?.

[Bob Willson]

Ice is made of many small crystals. Usually, when they are frozen they move a bit and the crystals are damaged as they freeze. This damage gives a higher index of refraction and so they reflect the light. Snow, which is also frozen water is a good example of this.

It is possible to make ice that is perfectly clear. (Well, at least as clear as the water it is made from.)

I do hope that this sounds sufficiently learned as I just intuited it all.

[silentC]

Nice try Bob. Actually it's because an ice crystal is not transparent, it is translucent. Light passes through it but not in a straight line. When you have a whole bunch of ice crystals in a big lump, the light is scattered all over the shop and most of it ends up bouncing right back at you and because this is happening more or less evenly across the spectrum of visible light, it appears white.

[Kris.Parker1]

Nice one. Okay one more question for all you Einstein wannabes out there. Should stump a few of you. We'll see.

If I were to turn a torch on whilst travelling at the speed of light, would I light up the path in front of me? I know the answer to this one so I thought it would be fun to see if any else knew. A great one to remember as it has a 6th sense type of twist to it.

Cheers

Kris

[silentC]

Yes

[silentC]

Now here's a question for you. If a second person is standing still and they observe you whizzing past at the speed of light, with your torch turned on, to the observer does the light from the torch appear to be moving at:

a. twice the speed of light?
b. the speed of light?
c. standing still?

[Kris.Parker1]

I would have to say that as nothing in existence can travel faster than the speed of light, to the observer I beleive it would also appear to be travellig at the speed of light.

Correct me if I am wrong.

For the light to look as though it was standing still time would have to stop. And as we all know time will stand still before the speed of light changes; however, light remains at a constant - theoretically if I were to shine a torch through a viscous liquid, such as clear oil, then the light would not so much slow down as the protons be absorbed by the oil thus reducing the amount of light getting through - hypothetically giving the appearance of light slowing down.

Whew - quantum pysics - what nightmare!

[craigb]

But how do you get the hard boiled egg into the bottle ?

[Kris.Parker1]

CraigB. I'd have to suggest getting a bigger bottle!

[silentC]

Your first statement is correct, according to the theory of relativity that is.

As for whether light can appear to stand still, it all depends on what you mean. It can appear to be standing still under certain circumstances. In your example, if I am the observer, to me both you and the torch light are travelling at the speed of light. Therefore the light appears to me to be standing still, relative to you, although it is moving past me at the speed of light.

Anyone got any Panadol?

[Bob Willson]

The speed of light is (as far as we know) a constant that is also the fastest thing known. It is also postulated that the speed of light cannot be exceded. That being so it is impossible for anything to go faster than that speed of light. The obverse of this is of course that no light can travel slower than the fastest speed of light.

Recent research is, however, starting to show that the speed of light is no longer acceptable as a constant

[Kris.Parker1]

Haave to agree with you on that one Bob. Just FYI if I were to travel at the speed of light for 1 billion years (where time equals 0) then I would have travelled 1 billion light years. At the same time while you were travelling at the speed of light, the universe (including Earth) would age 1 Billion light years. Goddamn that's hard to explain. You get what I'm trying to say though?

[silentC]

I read somewhere that someone has claimed recently to slow a photon down. There's also a theory about a type of glass that could trap the light and slowly release it out the other side, so you could have a window that let you look back in time.

All a bit much for a Friday and it's not even beer o'clock yet

[silentC]

You want weirdness? How about the idea that light is only a particle when you are observing it. When nobody is looking, it is a wave.

Oh, and if you take a pair of those little particles that make up a photon, one is always positive and the other is always negative - but only when you look at them. Until then, they can be one or the other. And as soon one turns positive, simultaneously the other goes negative. Theoretically, this can take place across any distance, so if you could unravel them and seperate them by a billion light years, if you could make one go positive, the other would instantly go negative. Trouble is no-one knows how to influence which state they take.

Mind bending....

[Kris.Parker1]

I read somewhere that someone has claimed recently to slow a photon down. There's also a theory about a type of glass that could trap the light and slowly release it out the other side, so you could have a window that let you look back in time.

I recall the item you are talking about. I think that it is called a photon accelerator. They have measured speeds up to almost the speed of light.