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Old 2014-04-26, 19:12   #1
cheesehead
 
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"Richard B. Woods"
Aug 2002
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Default Spooky? The arrow of time is downright dangerous in the wrong hands!

Thirty years ago, the idea that quantum entanglement might explain the arrow of time occurred to Seth Lloyd, a 23-year-old philosophy graduate student at Cambridge University with a Harvard physics degree (now an MIT professor). But when he tried to submit his 1988 doctoral thesis about it to a journal, he was told that there was “no physics in this paper."

Unlike most crackpot ideas, this one became more acceptable as it aged. Others elaborated and strengthened it.

"New Quantum Theory Could Explain the Flow of Time"
http://www.wired.com/2014/04/quantum-theory-flow-time/

Quote:
. . .

But to the bafflement of generations of physicists, the arrow of time does not seem to follow from the underlying laws of physics, which work the same going forward in time as in reverse. By those laws, it seemed that if someone knew the paths of all the particles in the universe and flipped them around, energy would accumulate rather than disperse: Tepid coffee would spontaneously heat up, buildings would rise from their rubble and sunlight would slink back into the sun.

“In classical physics, we were struggling,” said Sandu Popescu, a professor of physics at the University of Bristol in the United Kingdom. “If I knew more, could I reverse the event, put together all the molecules of the egg that broke? Why am I relevant?”

Surely, he said, time’s arrow is not steered by human ignorance. And yet, since the birth of thermodynamics in the 1850s, the only known approach for calculating the spread of energy was to formulate statistical distributions of the unknown trajectories of particles, and show that, over time, the ignorance smeared things out.

. . .

...The newer proofs are more general, researchers say, and hold for virtually any quantum system.

“When Lloyd proposed the idea in his thesis, the world was not ready,” said Renato Renner, head of the Institute for Theoretical Physics at ETH Zurich. “No one understood it. Sometimes you have to have the idea at the right time.”

. . .

In the new story of the arrow of time, it is the loss of information through quantum entanglement, rather than a subjective lack of human knowledge, that drives a cup of coffee into equilibrium with the surrounding room. The room eventually equilibrates with the outside environment, and the environment drifts even more slowly toward equilibrium with the rest of the universe. The giants of 19th century thermodynamics viewed this process as a gradual dispersal of energy that increases the overall entropy, or disorder, of the universe. Today, Lloyd, Popescu and others in their field see the arrow of time differently. In their view, information becomes increasingly diffuse, but it never disappears completely. So, they assert, although entropy increases locally, the overall entropy of the universe stays constant at zero.

“The universe as a whole is in a pure state,” Lloyd said. “But individual pieces of it, because they are entangled with the rest of the universe, are in mixtures.”

One aspect of time’s arrow remains unsolved. “There is nothing in these works to say why you started at the gate,” Popescu said, referring to the park analogy. “In other words, they don’t explain why the initial state of the universe was far from equilibrium.” He said this is a question about the nature of the Big Bang.

. . .

Twenty-six years after Lloyd’s big idea about time’s arrow fell flat, he is pleased to be witnessing its rise and has been applying the ideas in recent work on the black hole information paradox. “I think now the consensus would be that there is physics in this,” he said.

Not to mention a bit of philosophy.

According to the scientists, our ability to remember the past but not the future, another historically confounding manifestation of time’s arrow, can also be understood as a buildup of correlations between interacting particles. When you read a message on a piece of paper, your brain becomes correlated with it through the photons that reach your eyes. Only from that moment on will you be capable of remembering what the message says. As Lloyd put it: “The present can be defined by the process of becoming correlated with our surroundings.”

. . .

Last fiddled with by cheesehead on 2014-04-26 at 19:15
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Old 2014-04-26, 19:19   #2
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"Richard B. Woods"
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For the record: the original title of this thread is/was:

Theory: The arrow of time is a consequence of "spooky action at a distance"
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Old 2014-04-26, 21:39   #3
ewmayer
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A friend of mine has been pursuing the related theme of "observation as entanglement", which appears to be capable of resolving many spooky QM (apparent) paradoxes.

I am skeptical of the persistent, almost religious, bias modern QMicists appear to have for the holiness of information. If things get sufficiently entangled that one can no longer retrieve any information without an input of low-entropy energy of sufficient size to make the 2LOT hold, should we consider that as "lost" information or merely "annoyingly entangled" information?

For example:
Quote:
Originally Posted by cheesehead View Post
In the new story of the arrow of time, it is the loss of information through quantum entanglement, rather than a subjective lack of human knowledge, that drives a cup of coffee into equilibrium with the surrounding room. The room eventually equilibrates with the outside environment, and the environment drifts even more slowly toward equilibrium with the rest of the universe. The giants of 19th century thermodynamics viewed this process as a gradual dispersal of energy that increases the overall entropy, or disorder, of the universe. Today, Lloyd, Popescu and others in their field see the arrow of time differently. In their view, information becomes increasingly diffuse, but it never disappears completely. So, they assert, although entropy increases locally, the overall entropy of the universe stays constant at zero.
And whence the negative entropy to counterbalance the local increases? The assertion thus smacks more of religion than science. As does the next grand claim:

Quote:
“The universe as a whole is in a pure state,” Lloyd said. “But individual pieces of it, because they are entangled with the rest of the universe, are in mixtures.”

Last fiddled with by ewmayer on 2014-04-26 at 21:40
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Old 2014-07-25, 22:02   #4
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Quote:
Originally Posted by cheesehead View Post
For the record: the original title of this thread is/was:

Theory: The arrow of time is a consequence of "spooky action at a distance
"
I have math and works on time. All type up on papers. Mea to have ladies put on cloud for all. Beauty waits on silly me
Pray soon.
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Old 2014-07-25, 22:39   #5
chalsall
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Quote:
Originally Posted by Kathegetes View Post
I have math and works on time. All type up on papers. Mea to have ladies put on cloud for all. Beauty waits on silly me
Pray soon.
Clever. And pathetic.
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