View Full Version : Twins again

2002-Jan-23, 12:01 PM
On 2002-01-22 11:11, Donnie B. wrote: (http://www.badastronomy.com/phpBB/viewtopic.php?topic=470&forum=1&15)

On 2002-01-22 09:38, GrapesOfWrath wrote:

On 2002-01-22 08:37, Donnie B. wrote:
Is this one of those issues that depends on the presence of the rest of the cosmos, like the twin paradox?
Eh? Twins paradox. (http://mentock.home.mindspring.com/twins.htm)

I'm sorry for being so thick, GOW, but I don't see how that page explains away the paradox.

In the first case, A stays fixed and B accelerates away, then accelerates retrograde and returns. A is older than B.

In the second case, we take B as fixed. A accelerates away, then accelerates retrograde and returns. Yet A is still older than B.

The difference between the two cases is only one thing: B felt the acceleration in both cases. Yet, why should this be? With B taken as fixed, it was A who accelerated in the second case.

The only difference between them is that A remained fixed with respect to the greater universe. In the second case, B felt the acceleration because the whole cosmos went soaring past him. Good thing he had his rocket motors turned on, or he'd have been dragged along!

I'm not trying to be argumentative, but I'd be interested in getting this further clarified.

Check out the last paragraph of that link, where I talk about a "messenger Carl," which avoids the acceleration of the reference frames. Another attempt at explaining this is here (http://mentock.home.mindspring.com/twinrdux.htm).

2005-Nov-14, 06:40 PM
I don't mean to be flippant, but what if you don't have a twin? You can never know how truly comparitively old you really are? Nor who has really racked up the most frequent flyer miles.........