Time

[Steve Limpus]

Over at the Astronomycast forum I offered the opinion that we should consider time a 'thing' in and of itself - in my mind I was comparing the notion of 'time' to the notion of the 'north pole', considering it a location or co-ordinate in spacetime. I cited the idea that relativity teaches us time can speed up or slow down to support the argument that time is something.

The contrary view was, naturally, that time is not 'something' - it's just the relationship between other things... objects, events, etc.

However, on reflection, I'm becoming less comfortable that my position was more valid than the other.

Your thoughts? Or are the arguments on both sides moot?

I have the feeling Ken G will offer that my original position was not strong.

[Neverfly]

I agree with the argument against yours. That time is not a thing- just a relationship between.

[Jeff Root]

Time is as much a "thing" as space is, but no more so.

-- Jeff, in Minneapolis

[Ken G]

I have the feeling Ken G will offer that my original position was not strong.

Yes that's how I see it, but I wouldn't say it is weak either, the words are hard to even define meaningfully. Also, I don't see the other view you describe as being any stronger, to tell you the truth! Time is a measurable quantity, so that's where its "realness" lies, but if one is to look at its meaning I would say it fundamentally stems from the simple observation that a local observer always "packs in" the same amount of action in the same number of ticks of a local clock. In other words, the meaning of time stems from the fact that it cannot be sped up. The key comparison is not between my time and yours, it's between my clock, and my heart, and my footsteps, and my metabolism, and the rate of chemical processes and nuclear decay going on all around me. Your time has no place in that tapestry of mine, it is your time, which I match up with mine in a fairly arbitrary way to be able to interpret certain simplifying laws as being in play.

The fact that when we meet again, we may have experienced a different amount of elapsed time is a limitation of the absolute realness of time-- it shows that time's realness is purely owned by the person who experiences it. Yet, with that caveat, it does seem to be as real as anything can be, even though it is about relationships between things rather than the things themselves. I don't see "relationships" as any less real than "things", so I agree with you on that score, but again I see the realness of time as being due to its intransigence for a given observer, not its transigence when compared between observers.

[Steve Limpus]

Thanks Jeff and Neverfly, I understand both your points of veiw, and Ken, your thoughts have been a genuine help to me - appreciated all.

[mugaliens]

I agree with the argument against yours. That time is not a thing- just a relationship between.

I find it's more a function of "relative distance travelled" with velocity as a variable more than anything.

Consider 2 cases:

1. Tom and Jerry are stationary in space.

2. Tom and Jerry are both heading towards Proxima Centauri at .5 c.

In both cases, Jerry takes off towards Proxima Centuari at a velocity of .4 c relative to Tom. He continues for 1 month then reverses course to rendezvous back with Tom.

In both cases, the time dilation caused by Jerry's excursion and relative velocity to Tom is the same, regardless of the fact that Jerry's absolute velocity relative to "static space" (whatever that is) is very different.