Comments on: How long is forever?

By: John

John — Sat, 21 Nov 2015 16:40:08 +0000

I came late to this issue but am now fascinated by the implications for much of our post-Newtonian physics. My conclusion is that Julian Barbour et al are right and that all there ever has been is movement, time being a convenient short-hand notation based on our planet’s size and position in space. If time is suspect, therefore so is speed. But if speed is meaningless, so is acceleration. If acceleration is out the window, it just took with it our definition of local G. If a car is moving round the equator at 60 knots, mathematically all this means is that it is travelling at a speed of 1/15 (no units are needed) from the perspective of an observer stood on the equator. Why? Assume Earth has diameter D. Now replace nm with πD/21600 and hr with πD/24 and by very simple mathematics the result is 60 x 900 / 21600 = 1/15. It doesn’t matter where I position the observer, the result of a particular speed is always going to be a ratio.

By: H.S.Pal

H.S.Pal — Fri, 29 Oct 2010 16:01:41 +0000

CAN ANYTHING BE TIMELESS? Today’s scientists are like religious gurus of earlier times. Whatever they say are accepted as divine truths by lay public as well as the philosophers. When mystics have said that time is unreal, nobody has paid any heed to them. Rather there were some violent reactions against it. Here are some examples: “G.E. Moore pointed out that if time is unreal then there are no temporal facts: nothing is past, present or future, and nothing is earlier or later than anything else. But, plainly, it is false that there are no temporal facts, for it is a fact that I am presently inscribing this sentence and that my breakfast yesterday preceded my lunch.” - Richard M. Gale [Book: the philosophy of time, edited by Richard M. Gale, Publisher: Macmillan, 1962, Chapter: Introduction to Section Two, The static versus the dynamic temporal, page 69.] .... [See full text of comment 'Can anything be timeless?']

By: Reality Check admin

Reality Check admin — Tue, 10 Aug 2010 13:35:50 +0000

Of course, how foolish of me!

By: fostertom

fostertom — Tue, 10 Aug 2010 12:57:52 +0000

The left hand end

By: Reality Check admin

Reality Check admin — Tue, 10 Aug 2010 12:38:07 +0000

Excellent!
(But which end?)

By: fostertom

fostertom — Tue, 10 Aug 2010 12:18:37 +0000

I have a postcard with the caption ‘Eternity lasts a long time – particularly towards the end’.

By: Reality Check admin

Reality Check admin — Mon, 09 Aug 2010 19:53:23 +0000

There are two distinct types of time dilation in relativity, Ian (as I'm sure you probably know). The better-known one is relativistic time dilation, where two observers moving relative to each other see the other's clock going at a different rate from their own. You're absolutely right that in that case things only change in respect of events in another reference frame , i.e. another state of motion (according to current theory). I offer a comprehensive explanation for this, and a novel perspective, in my book Tapestry of Light. The second type is gravitational time dilation - that's the one I'm referring to in my post. In that, time dilates (slows down) objectively for everything within the influence of a gravitational field. So, for example, you could have a clock near the ground and another a few hundred feet in the air (at the bottom and top of a tower, for example), and a static observer could watch both clocks and see that the one nearer the ground was going slower because of the stronger gravitational field nearer the earth (though they'd have to watch for a long time to see any noticeable difference). [Note that the observer would see the same effect whether they were by clock A, by clock B, or some distance from both.] There have been some quite clever experiments doing almost exactly this, in a more sophisticated way, that have proved this effect conclusively. In that latter case time is affected within that gravitational reference frame, and an observer in that frame will know they're being affected - even though, for them, life will go on as normal, since everything around them is affected as well. I hope that clarifies things a bit - for you and for others.

By: Ian Dring

Ian Dring — Mon, 09 Aug 2010 18:01:46 +0000

Interesting article Grahame – this time dilation thing is a bit weird. Is it the case that within a frame of reference time is constant – it only changes (dilates) when you are making an observation from a distance or another reference frame.