What causes people to age differently?

[stevendaryl]

To Stevendaryl: Do you not agree that people who were once the same age suddenly had different ages in the given example?

Two people took two different paths through spacetime. One path was "longer" than the other, as measured using the spacetime metric. The twin who took that path aged more.

In space, there is nothing surprising about the fact that one person might take an hour to go from point A to point B, while another person takes two hours. Even though they both started at A, and both ended at B, one aged more along the way than the other. That's not surprising.

The same thing is true of spacetime, where A and B are not points in space, but points in spacetime. There is more than one way to get from A to B and the two different ways have different proper times.

 

[jartsa]

What causes people to age differently?

First, I think it would be good to know what causes people to age. Have you thought about that, spaced-out?

 

[Ibix]

Triplet Case: When Mary & Bill meet in passing, both are the same age, and Bill goes on to meet Barry when they are the same age. Barry then catches up with Mary, and they have different ages. This is a direct comparison of aging and shows that people who move differently age differently. Barry's and Bill's paths relative to Mary are the same - same speeds - same distances traveled - same space-time paths.

There is no math or geometry in the given triplet case

Of course there is maths and geometry. There always is. The problem here is that you haven't really thought about your experiment. If they are all going at the same velocity, they'll never catch up to each other. If they all cross at different times they must have gone at different speeds, which means different paths through spacetime.

The only other option is that they all started in different places, and then you have relativity of simultaneity to worry about (not to mention gynaecological complexity).

I agree with the analysis of others above - your mental model of relativity still has absolute simultaneity or absolute time in it. That's why it appears not to make sense to you.

 

[spaced-out]

Of course there is maths and geometry. There always is.

What math is needed?

The problem here is that you haven't really thought about your experiment. If they are all going at the same velocity, they'll never catch up to each other. If they all cross at different times they must have gone at different speeds, which means different paths through spacetime.

There is no such thing (physically-speaking) as "a path thru space-time" because space-time is math (geometry).

When two people born at the same time and place later have different ages, then something much more than mere math is afoot. And the only thing that differed about my people was their speeds.

 

[PAllen]

What math is needed?



There is no such thing (physically-speaking) as "a path thru space-time" because space-time is math (geometry).

When two people born at the same time and place later have different ages, then something much more than mere math is afoot. And the only thing that differed about my people was their speeds.

Is the difference flying from NY to Rome via Zurich, versus direct just math, not physics? Why is path through space physics but not spacetime? In fact, these different flights are also paths through spacetime.

 

[stevendaryl]

What math is needed?

Geometry.

There is no such thing (physically-speaking) as "a path thru space-time" because space-time is math (geometry)

When two people born at the same time and place later have different ages, then something much more than mere math is afoot. And the only thing that differed about my people was their speeds.

Speed is just math, so it can't possibly be the reason.

(Just to show that your argument doesn't make the least bit of sense.)

 

[ZapperZ]

The original question has been answered. Refusal to accept is not based on physics any longer. Thread closed.

Zz.