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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."
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? :)
But only from the point of view of an external god-like observer.
We need to start likening things to quantum physics. At this point rocket science is frikkin' easy compared to all this quantum stuff.
Until quantum entangled particles gets harnessed into the faster than light communications they've talked about over the years, no one will really care anyway.
Occasionally living proof of the Ballmer peak.
At least this time they're not pointing loaded guns at cats.
Science advances one funeral at a time- Max Planck
From the outside, the universe looks like a photograph.
I hope we're hanging on a nice wall.
A god-like observer can observe without interacting. Back in reality every observation is an interaction.
Time is an illusion. Lunch time doubly so.
Slashdot - News for Nerds, Stuff that Matters, in ISO-8859-1 Has just realised that beta makes this signature redundant
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.
Pretty good is actually pretty bad.
Just ignore him... NURSE! He's out of bed again!
Slashdot - News for Nerds, Stuff that Matters, in ISO-8859-1 Has just realised that beta makes this signature redundant
He is all those three, plus one more: omnihumorous.
We just haven't got the punchline yet.
After reading a lot on this is that sometimes an issue becomes a problem without reason.
Now, time is ONLY a man made measure - a measure between events. Nature/the universe doesn't know what time is nor cares about it. It is only us humans that need to try to explain time dilation and various other 'time issues' to make the maths work. Remove time, and I bet it will balance these equations.
Time cannot run backwards,as there is no such thing as time except in the human brain and the human concept of measuring changes.
Nature doesn't care about time? Tell that to the laws of thermodynamics. Entropy only goes one way.
If you watch a video of a ball rolling on a desk, you can't tell just by the video whether time has been reversed. The physics governing that motion don't care about time. If you watch a video of an egg being shattered, you'll know when the video is reversed. You know all the contents of the egg can't spontaneously get back together as time moves forward. That would be going to a much more well-ordered state.
Also, the GPS device you use to triangulate your position and navigate to your destination? Well, consider that relativity tells us that the satellites zooming up above us have slower ticking clocks. They're actually moving through time slower than you are, and our current GPS accuracy wouldn't be achievable if we didn't take that into account.
Just keep in mind that an 'observer' does not mean a conscious entity. An observer, in the quantum mechanical sense, is more accurately an "interactor", as in anything that interacts with it. Which, when put into those terms, their thought process in this paper is much clearer: without interaction there is no way to determine if time has passed, if there's no way to tell if time is passing... it may as well not be.
There are other physical constants, too. The charge of the electron for one and Plank's constant for another. The reality of a 'physical constant' is that it is just a ratio of one measured quantity in the observed Universe to another measured quantity that is always the same, so is sort of a conversion factor between physical observables which are somehow tightly related (not a great explanation, I know).
As for your light from the flashlight story -- there is no easy explanation because the easy explanations all depend on things behaving as we have grown up observing and internally modeling them in our low energy, slow speed existence. The explanation is just that at high relative speeds between observers the measurements of time and distance mix into each other such that each observer will always observe a light beam (in a vacuum) to be at 1.0c no matter what the speed of its source. A slightly deeper explanation is that time and 3 dimensional space form a four dimensional manifold (fancy name for something which local coordinates can be mapped to a flat space) in which the mix of time and space dimensions depends on the motion of the observer (actually reference frame of the observer). Relativistic effects are beyond the classical existence we model in heads growing up and so require math to take us beyond intuitive notions, that's about all I've got on the issue.
Speed is Distance / Time.
Your watch measures time, so you can use it to calculate how fast the light comes out of your torch by timing how long it takes to travel a distance, and you have a meter stick to measure just that.
When you are traveling fast, your watch slows down, and your meter rule gets shorter. However you don't notice this, as your own internal body's clock slows, and you yourself gets shorter in exactly the same proportions. But, when you measure the speed of light, coming out of the torch, now with your slower watch, and shorter meter stick, everything just adds up and you calculate the light to be traveling at the speed of light, EVEN THOUGH, the light, relative to you is now traveling just .5c.
The person you have just passed sees your watch, and meter rule, and thinks you've made a mistake, because your rule is longer and your watch ticks slower. He sees you measuring the speed of light coming from your torch. To him, he sees the light is coming out of your torch at .5c, but can see you (inaccurately) measuring it....and working it out to be 1c because you've measured it over a shorter distance using a slower watch.
When he measures the speed of the light coming out of your torch passing him, he also works it out to be going at light speed.
So there you go. There is no paradox. Light is going at the same speed regardless of if you are moving or not. The only difference is that your movement causes things like slowdown of time, and length change, which means that you are unable to calculate the "proper" relative speed of light, which would be .5c.......any attempt at measuring it, always comes out at 1c.
OR.....the more usual way of putting it is just make the speed of light constant, regardless of your speed, and alter the other things such as time, and length, to make your speed calculations always come to 1c.
Most of this has been known and stated fairly clearly in the quantum theory of open systems for some time now. The Nakajima-Zwanzig (generalized master) Equation is derived based on the assumption of a "universal" quantum description that is partitioned into "system" and "everything else", with a projection of all dynamics from everything else onto the system variables. The universe is, of course, completely deterministic, but entropy (and hence "time" as an arrow) enters the system from the incomplete information available on the system "bath", everything else.
The proper treatment of this completely eliminates the common quantum "paradoxes" such as Schrodinger's Cat because one can clearly see where one makes an incorrect assumption about the possibility of quantum entanglement of the cat and the microscopic decay process independent of "everything else". The entire "system" consisting of cat and box is coupled to the rest of the Universe and the apparently "purely random" decay that creates the supposedly tangled state that is resolved by opening the box is continuously resolved because the box and all of its contents is already tangled, so to speak, with everything else. It also helps to properly view and include time-reversibility in the description and not treat the quantum process of measurement non-relativistically and semi-classically. The same thing is true of the EPR paradox -- if it is treated relativistically there can obviously be no such thing as wavefunction collapse per se with some sort of transluminal communication of phase information, because the time reversal of this process makes no sense at all. The GME resolves this entirely because it correctly describes the infusion of classical entropy in a measurement process from the bath in an e.g. thermodynamic state within e.g. the random phase approximation.
Personally, I think the Nakajima-Zwanzig treatment and master equations are one of the most neglected areas of quantum theory, often completely untaught in graduate-level quantum series. It is one of the better ways to rigorously derive things like spontaneous emission and in the process explain a lot of things about the process that are otherwise mysterious, such as how "exponential decay" arises from the coupling of a two-level quantum emitter to a multimode bath (and how it does NOT occur if one, for example, couples a two-level quantum emitter to a single field mode). Loudon has a nice discussion of this point, and Agarwal describes the application of the GME to spontaneous emission including radiative shift. The outcome of this approach in quantum mechanics is often to transform exponential processes that typically move one out of the basis one begins in almost instantly (entanglement) to projective dynamics within the basis and with e.g. discrete dynamical transitions replacing cats that are half dead or half alive in an entangled state, a Langevin approach where the actual system really does either kill the cat or doesn't, at a particular time, with the correct probability distribution for an ensemble of diabolical cat-killing engines, because the rest of the Universe always functions as a "measuring apparatus" -- one cannot "disentangle" the cat, the poison, the radioactive source from the Universe by merely putting it in a box, and at the instant of the cat's death the future time evolution of the entire Universe is unique to this and only this outcome.
You can see some small part of the malaise that infects the terminology of quantum theory in the phrase above: "An external god-like observer sees no difference" -- the hardest single thing one has to deal with when correctly considering the quantum description of the Universe is the notion that there is no outside, most especially no outside from which the inside can be "seen". Seeing is the exchange of information, mediated by a field interaction. The Universe cannot possibly be "seen from the outside" because if the "outside" in question can see it at all, it is a part of it. It cannot
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.
You (as are most people with a poor grasp of these physics because of some shitty analogy someone used to explain it to them) are making the common mistake that the person with the flashlight in hand would think the light is traveling at 1c away from him (total of 1.5c) but they wouldn't see any such thing.
Yes they would see it traveling away at 1c - but the velocities don't sum like that. Due to time dilation, you're also experiencing time at a different rate than a stationary observer. The net effect is that you both see the light traveling at 1c.
To extend the analogy, suppose both people also have a stopwatch which starts timing at the exact moment when the person who's moving at 0.5c fires a pulse of light in the same direction as his movement. After the observer's stopwatch has reached 1 second, freeze everything and see where everyone is. The person who's moving at 0.5c has moved half the distance light travels in 1 second, obviously; about 149 896 km. The pulse of light has moved twice as far, about 299 792 km.
To the outside observer, the light has traveled 299 792 km in 1 second, i.e. it is moving at 1c.
The moving person, saw it travel only half as far relative to him - only 149 896 km - yet, because he's experiencing time at a different rate, his stopwatch has only ticked off 0.5 seconds. So from his perspective, the light has traveled 149 896 km in only 0.5 seconds, i.e. it is moving at 1c.
The problem is that they keep formulating and performing these measurements where the scientists work.
Everybody knows time doesn't pass at work. If they'd re-run the experiment under a rainbow or with a beautiful woman they'd find that time passes far too quickly in fact.
"Time, we know, is relative. You can travel light years through the stars and back, and if you do it at the speed of light then, when you return, you may have aged mere seconds while your twin brother or sister will have aged twenty, thirty, forty or however many years it is, depending on how far you traveled. This will come to you as a profound shock, particularly if you didn't know you had a twin brother or sister."
The preceding comment is my own, and in no way construes an opinon of the Emperor of Mankind.