Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: TyroJack on 09/09/2019 13:50:31

Title: If events can occur in a different order to observers how can tim be a dimension
Post by: TyroJack on 09/09/2019 13:50:31

When I think of time as the 4th dimension I imagine it broadly applying to the Universe which ages uniformly -- 3.8 billion years or so -- but how does that work if different observers, in relative motion, measure time differently?

A dimension gives us the ability to place something with a coordinate on an axis and points on an axis are in a strict order.

So how can time be a grand 4th dimension applying universally in Spacetime?

It seems much easier to see it as the 4th dimension in a particular frame of reference, assigning a time coordinate to objects or events within that frame.

Title: Re: If events can occur in a different order to observers how can tim be a dimension
Post by: alancalverd on 09/09/2019 15:47:52

The introduction of "relative motion" sows the seeds of confusion.

Suppose Alf, Bill and Charlie stand in a straight line in alphabetical order. From Alf's point of view, Bill is closer than Charlie. But now let Alf move along an arc to end up at the other end of the line. En route, B initially appears closer than C, then equidistant, then further away.

You have put your finger on the nub of relativity. There are no absolute coordinates.

Title: Re: If events can occur in a different order to observers how can tim be a dimension
Post by: Colin2B on 09/09/2019 18:16:19

Quote from: alancalverd on 09/09/2019 15:47:52

Suppose Alf, Bill and Charlie stand in a straight line ....

 ......You have put your finger on the nub of relativity. There are no absolute coordinates.

Excellent example of why it’s not just time that is relative.

Title: Re: If events can occur in a different order to observers how can tim be a dimension
Post by: yor_on on 17/09/2019 18:45:43

It's not as weird as you think. There is something called 'SpaceTme intervals'

That one will help.

the other thing to remember is that all other clocks you define goes out from yours.
And so theirs.

That's actually a 'constant'.
What it does is to give us a logic

Title: Re: If events can occur in a different order to observers how can tim be a dimension
Post by: CPT ArkAngel on 18/09/2019 20:12:16

The causal order of events is still the same for all observers.

Title: Re: If events can occur in a different order to observers how can tim be a dimension
Post by: TyroJack on 11/12/2019 11:52:38

Thank you, one and all.