First Experimental Evidence That Time Is an Emergent Quantum Phenomenon

KentuckyFC writes "One of the great challenges in physics is to unite the theories of quantum mechanics and general relativity. But all attempts to do this all run into the famous 'problem of time' — the resulting equations describe a static universe in which nothing ever happens. In 1983, theoreticians showed how this could be solved if time is an emergent phenomenon based on entanglement, the phenomenon in which two quantum particles share the same existence. An external, god-like observer always sees no difference between these particles compared to an external objective clock. But an observer who measures one of the pair — and so becomes entangled with it--can immediately see how it evolves differently from its partner. So from the outside the universe appears static and unchanging, while objects that are entangled within it experience the maelstrom of change. Now quantum physicists have performed the first experimental test of this idea by measuring the evolution of a pair of entangled photons in two different ways. An external god-like observer sees no difference while an observer who measures one particle and becomes entangled with it does see the change. In other words, the experiment shows how time is an emergent phenomenon based on entanglement, in which case the contradiction between quantum mechanics and general relativity seems to melt away."

Comments

Hmm

[wenchmagnet]

First time I've seen no comments show up a few minutes into a Slashdot story going up.

Are most other people, like me, scratching their heads and trying to wrap their minds around this? :)

Re:Hmm

[AbbyNormal]

You must be new here.

Re:Hmm

[Anonymous Coward]

Plus, all matter in the entire universe is entangled and the entanglement never fails and we cannot detect the other particle for some reason? That's an awfully big pile of nonsense.

"Nonsense" of course meaning "I'm not smart enough to make sense of this."

Re:Hmm

[pscottdv]

The theory requires no outside, God-like, observer, nor does it propose one. The point is that time is measured by "events" and "events" occur when the quantum states of two systems become entangled, but only to the systems that became entangled. To an "observer" that has not become entangled, a system is static and no event has occurred.

In the Copenhagen interpretation, one would say that according to the entangled observer the "wavefunction has collapsed" whereas according to the unentangled observer, it hasn't.

Re:Hmm

[mcgrew]

It was very early in the US and very late in Europe when the story broke.

Yesterday there was a story posted at slashdot that asked if your thermostat had free will. I think this answeres the question -- no. Not ony does you thermostat not have free will, neither do you.

The new problem was that time played no role in this equation. In effect, it says that nothing ever happens in the universe, a prediction that is clearly at odds with the observational evidence.
<snip>
But the results depend on how the observation is made. One way to do this is to compare the change in the entangled particles with an external clock that is entirely independent of the universe. This is equivalent to god-like observer outside the universe measuring the evolution of the particles using an external clock.

In this case, Page and Wooters showed that the particles would appear entirely unchangingâ"that time would not exist in this scenario.

Free will is an illusion.

Re:Hmm

[taiwanjohn]

I can appreciate the "get off my lawn" sentiment as much as the next guy, but honestly I don't feel the /. experience has degraded that much since the old days. Is it different now from when I joined 15 years ago? Yeah, sure. But so am I. So's the world.... So what?

The thing I find consistent about /. and which keeps me coming back here is that I know I'll (almost) always find something interesting here, often something very interesting and/or enlightening. Sure, I may occasionally bitch and moan about the dupes and the mods, etc., but when I see a story that looks interesting and has a "healthy" discussion going, I'm pretty confident that reading that discussion will give me some new insights or information that I hadn't heard of before. Offhand, I can't think of many other "popular" websites I could say the same about.

Re:I think...

[dingen]

What? Of course time isn't man-made. Why would you say only man cares about time? I'm pretty sure plants and animals are also happily perceiving the passage of time.

Re:Instead of likening things to rocket science

[Amouth]

If you don't nurture them then yes they don't grow. You don't have to force things on them but rather encourage their natural want to learn.

Now having a child (3 years old at the moment) i'm amazed at how quick they can learn, and feel sorry for children who's Parents don't interact with them and teach them. Too many parents want the schools to do everything for them, yet it is what they do outside of school which has the greatest impact to what they learn.

We are lucky, we don't say "Damn, I wasn't that dumb when I was that age!" instead my wife and I both go "Damn, he is smart, smarter than either of us at that age." and as long as we keep constantly feed him new ideas and information and reinforce it he will continue to be smarter than we were or are.

Again, just for the soapbox, the fact that children on average are getting "dumber" is completely the fault of their Parents.

If a tree falls in the forest

[MobyDisk]

If a tree falls in the forest and no one observes it, how long did it take to fall?

Re:Instead of likening things to rocket science

[camperdave]

Sadly, it's becoming well nigh impossible to find a decent chemistry set, electronics kit, meccano set, or even a generic Lego set. Everything is either excessively "safened" or themed to the point of monotony.

Re:First Post!

[TopherC]

What I can't yet understand is how this experiment helps validate the theory of time as an emergent quantum phenomenon. It seems more like a demonstration than an experiment to me. What alternative theory is their experiment excluding?

I'm a physicist but that doesn't mean I understand any of this QM stuff. I have a feeling this is a little like experimentally demonstrating Bell's inequality -- one can do experiments whose results are consistent with predictions of QM, and in ways that one might expect other general classes of theories to differ even though you don't have a specific alternative theory to exclude. Most experiments are like this really. But in the case of this time-entanglement experiment I really don't see room for alternative predictions. I think the paper's title acknowledges this: "Time from quantum entanglement: an experimental illustration" (my emphasis).

I'm not saying that the experiment is in any way unhelpful or bad. It's a great idea, but I would not go so far as to say that this is "experimental evidence."