Identify an experiment.

[China Doll]

Hi All,

Following on from PLIVELY34's thread last night I posed the same question to a friend of mine and we have a bit of a discussion. He mentioned something about an experiment which he thought was done by Einstein (sp?) but wasn't sure and he also couldn't remember the outcome, (this did not help the point he was trying to make but did succeed in making me curious).

The experiment was something to do with strapping a clock to some sort of engine and then sending it backwards. Does anyone know what he was talking about? Why was the experiment done? What was the outcome?

Cheers China

[jake-the-peg]

Einstein proposed a lot of thought experiments like this. this sounds a lot like the famous "twins paradox" where you take two twins and put one in a rocket and zoom him about the universe at close to the speed of light. When he returns the twin he's left is in his old age but the astronaut is just a few days older.

This is because time slows down as you get close to the speed of light (special relativity) or get acted on by a large gravitationnal force.

An experiment similar to this has been done many times but most famously in 1971 when 4 atomic clocks were sychronised and flown around the world in a 747 the result showed that time dilation did indeed happen.

http://hyperphysics.phy-astr.gsu.edu/hbase/rel ativ/airtim.html

Would this be what you were thinking of?

[China Doll]

Cheers Jake you're a star, it looks like what he was talking about. I'll double check later.

(Not quite sure I understood the results.... or indeed my mates point but hey ho!)

[jake-the-peg]

Well the twins one can get a trifle complex - there's a simpler demonstration.

The point is that time doesn't work the way we all tend to think that it does. All is happy in the garden in our everyday lives but if you start travelling close to the speed of light time slows down relative to the 'stationary' world.

My favorite example is muons. These little exotic particles are formed in the upper atmosphere as cosmic rays crash into the air.

Now these muons are short lived and only a very few should live long enough to make it down to the ground. But we don't see a few, we see loads - in fact nearly 100,000 times as many as we ought to see.

The reason is that they travel so fast time slows down for them long enough for them to make it to the ground.

http://hyperphysics.phy-astr.gsu.edu/hbase/rel ativ/muon.html

The point of all this is that we may think that we all know how time works but in extreme situations it's actually pretty different.

Bit like a blind man who's only ever felt the trunk of an Elephant and is being told that there's way more to it in reality :c)

[China Doll]

I liked the picture but the equation went right over my head.

Think I know how that blind man feels....

Thanks Jake, you're a star.

[rojash]

The problem I have with the Twins is this: If Alf is travelling at close to the speed of light relative to Bill, then Bill must be travelling at close to the speed of light relative to Alf. So each should see the other as having experienced time dilation, and each will be younger (or older, depending on from whose point of view you are looking) than the other.

[China Doll]

Rojash - As much as that is a really interesting point I do feel that you have pretty much nailed the lid on me getting any sleep tonight. That's the sort of thing that whirls around and around my head, (there's a lot of whirling around space). :0)

[jake-the-peg]

Yep that is indeed what makes it a paradox. - The solution to this is on Wikipedia in some detail but the point is that only the twin in the rocket undergoes acceleration and deceleration as he leaves and turns around to come home which is what makes him different to his brother.

This is kind've why I went on to muons as it's easier (ha ha) to understand

Just think of high speed as natures little "suspended animation chamber"