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July 06, 2008

Mysteries of time, and the multiverse

From The Los Angeles Times:

Sean_2 In his studies of entropy and the irreversibility of time, Caltech physicist Sean Carroll is exploring the idea that our universe is part of a larger structure.
Caltech physicist Sean M. Carroll has been wrestling with the mystery of time. Most physical laws work equally well going backward or forward, yet time flows only in one direction. Writing in this month’s Scientific American, Carroll suggests that entropy, the tendency of physical systems to become more disordered over time, plays a crucial role. Carroll sat down recently at Caltech to explain his theory.

What's the problem with time?

The irreversibility of time is sort of the most obvious unanswered question in cosmology.

Time has been talked about in cosmology for many years, but we have a toolbox now we didn't used to have.

We have general relativity, string theory, discoveries in particle physics that we can use to help us find the right answer.

What does entropy have to do with all this?

The most obvious fact about the history of the universe is the growth of entropy from the early times to the late times.

The fact that you can turn eggs into omelets but not vice versa is a thing we know from our kitchens.

You don't need to spend millions of dollars on telescopes to discover it.
More here.

Posted by Azra Raza at 05:56 AM | Permalink

Comments

surprisingly elegant and insightful. remerciations.

Posted by: aditya | Jul 6, 2008 2:08:15 PM

Sean rocks because he recommended Eddington to me! I'd love to take him out to dinner some day...

Posted by: missvolare | Jul 6, 2008 2:33:50 PM

All physical laws have the implied statement with them that they apply unidirectionally in time, since this is all that is ever observed. Time is only a meaningful concept when some observable quantity changes.
Maxwell’s equations are symmetric and do not specify the constraint of causality that the signal may not be received by the receiver before it is transmitted from the transmitter. But this physical constraint is always implied if not stated explicitly. The motion of the earth about the Sun is the traditional way of comparing times but others could and are used in various situations. Frying an egg is an example of an irreversible thermodynamic process which cannot be reversed by simply reversing the energy supply. This is a confusing example in this context. The confusing discussion introducing entropy and time is nothing new. The speculative discussion about other universes is unenlightening since they have not been observed. This is another example of a low quality article published by Non Scientific American.

Posted by: Winfield J. Abbe | Jul 6, 2008 11:57:22 PM

@Winfield J. Abbe,

You say:

All physical laws have the implied statement with them that they apply unidirectionally in time, since this is all that is ever observed. Time is only a meaningful concept when some observable quantity changes. (emphasis added)

I don't believe that to be true. For example, Kepler's Laws of Planetary Motion would work be the same even if time were reversed.

Posted by: Eric | Jul 7, 2008 5:23:34 PM

We are obviously missing something major, and this side track into string theory has done nothing, other than enhance some elegant mental masturbation.
Looking into Time may give the needed break from this dismal time in this chapter of physics.

Posted by: Dave Ranning | Jul 7, 2008 7:45:47 PM

'The speculative discussion about other universes is unenlightening since they have not been observed."

What a frightening idea, that something must be observed for it to be talked about in an enlightening way. The history of intelligence is full of unobservable ideas that are nevertheless enlightening — ideas that, without proof (or even pudding), reveal a previously untrod-upon path down which we might walk and light lights. Lights by which future generations can — yep — observe.

Posted by: ghostman | Jul 7, 2008 8:02:25 PM

INHO, science can't find what it's looking for because it is looking in completely the wrong place - the multiverse concept is intellectually neat but a cop out

Posted by: Tom Evans | Jul 8, 2008 3:58:16 AM

very thought provoking and insightful

Posted by: Sachin | Jul 8, 2008 5:00:02 AM

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