Friday, September 4, 2009

The Quantum Solution to Time's Arrow

A direct link to the above video is at

There's a great feature on different approaches to visualizing the extra dimensions over at New Scientist: "Beyond Space and Time: Fractals, Hyperspace, and More". Most of what's in there is a repeat of ideas explored in my book and this blog: I think this is great, as it seems to be part of a general shift within mainstream science this year where the ideas I've been promoting are gradually becoming more accepted.

I've mentioned before that the sound effects of my original Imagining the Tenth Dimension animation are an important part of what helps to convey the information being explored. One of the key ideas to this way of visualizing the extra dimensions is conveyed by the repetitive use of the sound of a thick deck of cards being riffled - and this sound ties to the idea that although our reality feels like a continuous whole, or a continuous "line of time", it's actually divided into tiny little planck-length-sized pieces. Previous blog entries like The Flipbook Universe and Slices of Reality have also discussed this concept.

In my popular blog entry Creativity and the Quantum Universe, we discussed some of the new lab experiments which appear to prove that life is somehow engaged with a larger chunk of reality than these quanta, these planck-length slices that the granular nature of spacetime tells us we exist within from instant to instant. In The Holographic Universe, I talked about the GEO600 experiment which appears to prove through observation that our reality is not continuous. And here's a link to a recent cover story from New Scientist magazine: "Late Light Reveals What Space is Made Of". As evidence mounts that these "atoms of spacetime" (as they were called last year in a Scientific American article on Loop Quantum Gravity which we looked at in "Why is the Speed of Light the Limit?") are what our reality is truly constructed from, the application of quantum theory to our macro world makes more and more sense.

There are other mind-boggling implications if the quantum and macro worlds really are all part of a single continuum from the very small to the very large, throwing away the dividing line between these two realms that has traditionally been proposed. Here's a link to a new article written by Lisa Zyga, "Physicist Proposes Solution to Arrow-of-Time Paradox", that was published last week at . I'll quote a few paragraphs from the article here:

Entropy can decrease, according to a new proposal - but the process would destroy any evidence of its existence, and erase any memory an observer might have of it. It sounds like the plot to a weird sci-fi movie, but the idea has recently been suggested by theoretical physicist Lorenzo Maccone, currently a visiting scientist at MIT, in an attempt to solve a longstanding paradox in physics.

The laws of physics, which describe everything from electricity to moving objects to energy conservation, are time-invariant. That is, the laws still hold if time is reversed. However, this time reversal symmetry is in direct contrast with everyday phenomena, where it’s obvious that time moves forward and not backward. For example, when milk is spilt, it can’t flow back up into the glass, and when pots are broken, their pieces can’t shatter back together. This irreversibility is formalized through the second law of thermodynamics, which says that entropy always increases or stays the same, but never decreases.

This contrast has created a reversibility paradox, also called Loschmidt’s paradox, which scientists have been trying to understand since Johann Loschmidt began considering the problem in 1876. Scientists have proposed many solutions to the conundrum, from trying to embed irreversibility in physical laws to postulating low-entropy initial states.

Maccone’s idea, published in a recent issue of , is a completely new approach to the paradox, based on the assumption that is valid at all scales. He theoretically shows that entropy can both increase and decrease, but that it must always increase for phenomena that leave a trail of information behind. Entropy can decrease for certain phenomena (when correlated with an observer), but these phenomena won’t leave any information of their having happened. For these situations, it’s like the phenomena never happened at all, since they leave no evidence. As Maccone explains, the second law of thermodynamics is then reduced to a mere tautology: physics cannot study processes where entropy has decreased, due to a complete absence of information. The solution allows for time-reversible phenomena to exist (in agreement with the laws of physics), but not be observable (in agreement with the second law of thermodynamics).

In his study, Maccone presents two thought experiments to illustrate this idea, followed by an analytical derivation. He describes two situations where entropy decreases and all records of it are permanently erased. In both scenarios, the entropy in the systems first increases and then decreases, but the decrease is accompanied by an erasure of any memory of its occurrence. The key to entropy decrease in the first place is a correlation between the observer and the phenomenon in question. As Maccone explains, when an interaction occurs between an observer and an observed phenomenon that decreases the entropy of the correlated observer-observed system, the interaction must also reduce their quantum mutual information. When this information is destroyed, the observer’s memory is destroyed along with it.

I want to make special note of this phrase: "Maccone’s idea... is a completely new approach... based on the assumption that is valid at all scales". As people familiar with my project will know, there are critics who have said that by assuming there is a direct continuum from the quantum to the macro worlds, I am somehow mistaken. I've talked many times about the 2007 proof offered by a team of scientists at Oxford under the direction of physicist David Deutsch which also agrees with this idea of there being no actual separation between the quantum and the macro, and I will continue to underline this idea as I see it come up in other scientific theories.

Quantum mechanics is probabilistic, some outcomes are chosen over others, but Everett's "Many Worlds" Interpretations tells us all the choices ultimately exist within an underlying fabric which is intimately connected together. That's true at the quantum level, and it is just as true for our lives, and it's true for the entire universe we find ourselves within. More and more people are embracing this idea that I believe to be self-evident: once you back out to the biggest picture of all, everything fits together.

A direct link to the above video is at

Coming up next: The Statistical Universe.

Enjoy the journey!

Rob Bryanton

Other related blogs:
The Long Undulating Snake
Does the Multiverse Really Exist?
Aren't There Really 11 Dimensions?
Have Each of Us Already Died?
Scrambled Eggs
Local Realism Bites the Dust
Time is a Direction
Information Equals Reality

No comments:

Tenth Dimension Vlog playlist