[BobSpence (OP)]

In a recent show you responded to a caller re travelling at near the speed of light. I think you got it somewhat confused.
First, according to the original Special Relativity Theary, To BOTH an observer on the earth AND one on a spacecraft travelling away from or towards the earth would see the other's clocks running slow, so after travelling for a while, each would see the other as having aged less than themselves, so if the travellers returned to meet, you would have a severe paradox, as each could not be younger than the other!
The point here is that Special relativity only applies to objects travelling at CONSTANT velocity, and it is not possible to board a spacecraft on earth, travel at high speed to a distant point, and return without changing velocity several times by  large amounts. This requires us to use General Relativity, which predicts that when objects subject to high acceleration or high gravitational fields, which are shown to be equivalent to a certain degree, time slows down for them. This would cause the traveller to have aged less when they return - this effect would resolve the paradox.

Regards,
Bob S.

[chris]

Thanks for that Bob. I think this relates to the show featuring Simon Goodwin doesn't it ? I remember him saying when asked the question "How long have you got" and receiving the answer "Relatively speaking, not that long !".

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[BobSpence (OP)]

Yes Chris, that was the show. Variations of this example, usually referred to as the twins paradox have been annoying me for years, since to me they actually miss the point of the 'true' paradox I pointed out, so your show is certainly not the first to have presented this.

I certainly realize that Relativity theory is not easy to wrap your brain around, and to 'explain' it in a few minutes would be asking a bit much.

Anyway I should say I certainly enjoy your podcasts, yours was one of the first I subscribed to after I got my iPod a few months ago.

Regards,
Bob S.

[chris]

Thanks Bob.

I'll let you in on a little secret now. That's actually quite an old show and we've only put it out this week in order to smooth the way into the new series which starts this weekend. It's naughty of me to have missed it, but, the new stuff will certainly be free of any space/time anomalies !

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx