Comments on: The Arrow of Time http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/ I am an astronomer, writer, and skeptic. I likes reality the way it is, and I aims to keep it that way. My real name is Phil Plait, and I run the Bad Astronomy blog. Sun, 05 Jul 2009 04:16:21 +0000 http://wordpress.org/?v=2.3.1 By: Elwood http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58527 Elwood Sun, 09 Dec 2007 00:25:17 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58527 [i]The Elegant Universe[/i] has a brief mention of a possible additional time dimension in Superstring Theory, beyond the additional rolled-up spatial dimensions. The second time dimension could conceivable travel in a direction other than forward, forward at a different rate, or reverse itself once bilions of years or millions of times per second. The very concept of time other than the time we normally experience is incredibly difficult to comprehend with our experience being what it is. [i]The Elegant Universe[/i] has a brief mention of a possible additional time dimension in Superstring Theory, beyond the additional rolled-up spatial dimensions. The second time dimension could conceivable travel in a direction other than forward, forward at a different rate, or reverse itself once bilions of years or millions of times per second. The very concept of time other than the time we normally experience is incredibly difficult to comprehend with our experience being what it is.

]]> By: Irishman http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58528 Irishman Sat, 08 Dec 2007 21:52:54 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58528 ZZMike said: > The simple answer (to why don’t we remember the future) is, of course, because it hasn’t happened yet. At any instant of time, things can go any number of different ways, but once past that instant, things solidify into the Past. (Except perhaps in the quantum arena.) Sorry, but all you've done is restate the problem of the Arrow of Time. Why is it that things solidify? That's a process of entropy. ZZMike said:
> The simple answer (to why don’t we remember the future) is, of course, because it hasn’t happened yet. At any instant of time, things can go any number of different ways, but once past that instant, things solidify into the Past. (Except perhaps in the quantum arena.)

Sorry, but all you’ve done is restate the problem of the Arrow of Time. Why is it that things solidify? That’s a process of entropy.

]]> By: Wildride http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58526 Wildride Fri, 07 Dec 2007 20:54:04 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58526 Like most answers to this, it's pretty much begging the question, but how about some kind of temporal momentum. There's a big bang and space expands in three space, so why not in four space? The present is the leading edge of said expansion and that's why we remember the past but not the future. The past is where it's expanded from and the future is where it's expanding to. That would mean there's probably an anti-time universe which is contracting in four space, just like the Backwards episode of Red Dwarf. Like most answers to this, it’s pretty much begging the question, but how about some kind of temporal momentum. There’s a big bang and space expands in three space, so why not in four space? The present is the leading edge of said expansion and that’s why we remember the past but not the future. The past is where it’s expanded from and the future is where it’s expanding to. That would mean there’s probably an anti-time universe which is contracting in four space, just like the Backwards episode of Red Dwarf.

]]> By: Chip http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58525 Chip Fri, 07 Dec 2007 20:33:03 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58525 In "Geometry, Relativity and the Fourth Dimension" published by Dover in 1977, the author Rudy Rucker has a somewhat humorous essay about what life would be like now if, in the future, time flowed backwards. His implication however is that even the most ridiculous scenarios would, relative to all other backward frameworks, have observable natural processes and explanations. In “Geometry, Relativity and the Fourth Dimension” published by Dover in 1977, the author Rudy Rucker has a somewhat humorous essay about what life would be like now if, in the future, time flowed backwards. His implication however is that even the most ridiculous scenarios would, relative to all other backward frameworks, have observable natural processes and explanations.

]]> By: Stephanie http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58524 Stephanie Fri, 07 Dec 2007 19:57:43 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58524 YinYang and PK: Yes, Martin Amis' "Time's Arrow" is a spectacular book. YinYang and PK:
Yes, Martin Amis’ “Time’s Arrow” is a spectacular book.

]]> By: ZZMike http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58523 ZZMike Fri, 07 Dec 2007 19:24:11 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58523 The simple answer (to why don't we remember the future) is, of course, because it hasn't happened yet. At any instant of time, things can go any number of different ways, but once past that instant, things solidify into the Past. (Except perhaps in the quantum arena.) You could say that time is just one of those four dimensions in which we are trapped. We can move around in the other three (though not separately), and when we move, we're using one of the properties of the 4th - time - to do our moving with. The difference is that we have a choice about how we move in the three - but not in the 4th. (It was Arthur Eddington, in 1927, who came up with the expression. He concluded that it's a property only of entropy.) I couldn't find anything by either Bradbury or Clarke called "Arrow of Time", but Bradbury (and a host of others) have written stories about time-travel. The simple answer (to why don’t we remember the future) is, of course, because it hasn’t happened yet. At any instant of time, things can go any number of different ways, but once past that instant, things solidify into the Past. (Except perhaps in the quantum arena.)

You could say that time is just one of those four dimensions in which we are trapped. We can move around in the other three (though not separately), and when we move, we’re using one of the properties of the 4th - time - to do our moving with. The difference is that we have a choice about how we move in the three - but not in the 4th.

(It was Arthur Eddington, in 1927, who came up with the expression. He concluded that it’s a property only of entropy.)

I couldn’t find anything by either Bradbury or Clarke called “Arrow of Time”, but Bradbury (and a host of others) have written stories about time-travel.

]]> By: Jason B. http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58522 Jason B. Fri, 07 Dec 2007 19:03:00 +0000 http://blogs.discovermagazine.com/badastronomy/2007/12/06/the-arrow-of-time/#comment-58522 So, does the arrow of time never reverse, or is a reversal simply very unlikely? So, does the arrow of time never reverse, or is a reversal simply very unlikely?

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