Brother paradox
Discussion
A variation of the Twin Paradox:
A man in a space rocket is travelling in one direction and passes his younger brother, by 5 years, in another rocket moving in the opposite direction. After a while both brothers return and meet up. Will their age difference still be 5 years, or less? Relativity says the one travelling faster will have have had less time pass relative to the slower one, but where is the point of reference? The speed of the men is only relative to each other.
Is it that the faster one has to accelerate more than the slower one?
A man in a space rocket is travelling in one direction and passes his younger brother, by 5 years, in another rocket moving in the opposite direction. After a while both brothers return and meet up. Will their age difference still be 5 years, or less? Relativity says the one travelling faster will have have had less time pass relative to the slower one, but where is the point of reference? The speed of the men is only relative to each other.
Is it that the faster one has to accelerate more than the slower one?
Edited by V8LM on Sunday 30th June 12:30
it is "relative" to where they meet up,
if they both travel half way they will be the same age
if one travels say 10% distance and the other 90% then they will have aged differantly
so the brother who has traveled further will have aged less
the brother who only did 10% of the distance will have aged more (presumably sitting in the little chef at aplha centuri for a long time whilst he waits for his brother)
if they both travel half way they will be the same age
if one travels say 10% distance and the other 90% then they will have aged differantly
so the brother who has traveled further will have aged less
the brother who only did 10% of the distance will have aged more (presumably sitting in the little chef at aplha centuri for a long time whilst he waits for his brother)
Russian Rocket said:
the brother who only did 10% of the distance will have aged more (presumably sitting in the little chef at aplha centuri for a long time whilst he waits for his brother)
But from the brothers frame of reference the little chef has been travelling while he stayed still, that is what I think the OP's question refers to.State 1) Two brothers, the same age, are side by side.
State 2) The two brothers recede from each other at a significant proportion of the speed of light.
State 3) The two brothers are reunited and are side by side again. If the travelled one is younger, what frame of reference decides which one travelled and which stayed still? From each brothers point of view the other brother travelled while they stayed still.
In the conventional version of the twin paradox, the travelling twin ages less because the situation is not symmetrical - the twin that goes to Pluto or wherever and back again has to decelerate and accelerate again to get back to the start point, while the other just sits on his arse.
In the version you describe here, it sounds to me like the brothers undergo symmetrical accelerations. They therefore age identically, and the age difference remains the same.
In the version you describe here, it sounds to me like the brothers undergo symmetrical accelerations. They therefore age identically, and the age difference remains the same.
I think I see it now thanks. Russian Rocket's explanation makes great sense thinking about paths through space-time. The brother's paths are joined at the start and again at the end. But the paths are unequal lengths as one has travelled faster than the other, so their time has passed less than the other.
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