Posts Tagged‘quantum mechanics’

At The Quantum Level Measurement is Everything.

As we go further and further down into the world of infinitesimally small physics the rules we use at the macro level start to break down. Where once we had defined rules that governed the behaviour of bodies interacting with each other we quickly end up in the realm of possibilities rather than definites, something which causes no end of grief to those seeking to understand it. Indeed whenever I feel like I’m getting close to understanding a fraction of what quantum mechanics is something else comes out of left field that ruins it, leaving me with a bunch of disjointed pieces of information that I try to make sense of yet again. Today I bring you one such piece which both makes complete sense yet is completely nonsensicalfarnsworth not fairPhysicists at our very own Australian National University designed an experiment to test the wave/particle duality that single atoms can exhibit. Their experiment consisted of a stream of single helium atoms that were fired down an apparatus that contained 2 light gates which, if activated, would cause a interference pattern when measured (indicating a wave). However should only one of the gates be open then the particle would travel down a single path (indicating a particle). The secret sauce to their experiment was that the second gate, the one which would essentially force the particle to travel as a wave, was turn on randomly but only after the particle would have already traversed the gate. This essentially proves the theory that, when we’re operating at the quantum level, nothing is certain until measurements are made.

Extrapolating from this you can make some pretty wild theories about the mechanism of action here although there are only a few that can truly make sense. My favourite (and the one that’s least likely to be real) is that the information about the gate activation travelled back in time and informed the particle of the state before it traversed them, meaning that it was inevitable for it to be measured that way. Of course the idea of information travelling back in time violates a whole slew of other physical laws but if that proved to be correct the kind of science we could pursue from it would be straight out of science fiction. I know that’s not going to happen but there’s a part of me that wants to believe.

The far more mundane (and more likely) explanation for this phenomena is that the atom exists as both a particle and a wave simultaneously until it is observed at which point it collapses down into the only possibility that make sense. Whilst some may then extend this to mean things like “The world doesn’t exist unless you’re looking at it” it’s actually a far more nuanced problem, one that requires us to understand what constitutes measurement at a quantum level. At a fundamental level most of the issues arise out of the measurement altering the thing you’re trying to observe although I’m sure there’s far more to it than that.

I’m honestly not sure where these results will take us as whilst it provides evidence for one interpretation of quantum mechanics I don’t know where the future research might be focused. Such an effect doesn’t appear to be something we can make use of, given the fact that measurement needs to take place for it to (in essence) actually happen, but I’ll be the first to admit that my knowledge of this area is woefully limited.

Perhaps I should take a wander down to the university, although I fear I’d only walk out of there more confused than ever…

 

Quantum Entanglement Just Became a Whole Bunch Weirder.

Quantum Mechanics is…weird. Anyone who’s had a passing education in the world of physics will know of certain principles that hold true for pretty much everything but the second you dive into the quantum world all that knowledge and understanding won’t help you one bit. Even simple things like “2 objects can’t exist in the same place at the same time” aren’t true when you’re down at that level, destroying any sense of logicality you might have had when approaching the subject. Indeed there’s a quote famously attributed to Richard Feynman that “If you think you understand quantum mechanics, you don’t understand quantum mechanics”, although I’ve yet to find anyone say that they do understand it (I sure as heck don’t). Worse still even when you think you’ve got one principle figured out an experiment will come around and turn it on its head, like quantum entanglement recently was.

Quantum Entanglement

Quantum entanglement, in its simplest form (at least in my understanding) is the phenomena whereby two particles are linked together at the quantum level. Should you attempt to measure some attributes of one of the particles, say an electron’s spin, the other particle will instantaneously assume the same observed state regardless of the distance separating them. Whilst we don’t know the exact speed at which that state travels we do know it’s at least 10,000 times faster than the speed of light, something which would appear to violate the cosmic speed limit. However no information is actually transferred between the two particles, they simply assume the same state at the exact same time, and indeed any applications you might think of to use it to transfer information will, unfortunately, fail. Up until recently it was thought that such entangled particles needed to be close to, or create with, each other in order for entanglement to happen. However that’s not the case anymore as particles can be entangled even without knowing each other.

I think I actually ended up understanding less about quantum mechanics after finding this out.

The research, done at Chapman University, attempted to explore what’s called the Pigeonhole Principle in the realm of quantum mechanics. It’s a relatively simple mathematical concept to explain: say you have 3 pigeons and 2 pigeonholes, if you were to put all the pigeons into those holes at least one of them would contain 2 pigeons. Simple right? Well it is and simple proofs like this have a multitude of uses in mathematics, however when it’s applied to quantum mechanics some…strange things happen. Essentially the research team found out that you could put infinite pigeons into only 2 different holes and none of them would end up in the same hole. If that sounds confusing that’s because it is, but this has what lead the research team to demonstrate that particles, even those which had no idea their entangled partner existed, could in fact be entangled.

Like most discoveries in the area of quantum mechanics the potential practical applications of this discovery aren’t readily apparent. The big issue we have with using quantum entanglement for anything currently is that making entangled particles is ridiculously hard. However if there’s potential for particles to be entangled without them needing to be near each other, or having even known each other at all, there’s potential to do away with the expense of creating them ourselves. Just how we go about harnessing these naturally entangled particles, and whether or not they have any practical uses, is something that will have to be worked on.

I have no doubt that quantum mechanics is a fertile ground for research to be conducted however I sometimes wish it wasn’t so weird. It took me the better part of 2 hours just to make sure I was understanding what the hell was actually going on and to verify that what the various reports were saying lined up with the actual research. Don’t get me wrong though, this kind of stuff is incredibly exciting, but it feels like you have to be wired in a slightly weird fashion for any of it to make sense to you the first time around. I’m sure it won’t be long before I’m thoroughly confused again, especially if anyone out there points out some factual inaccuracies in this post.

I think I need to lie down…

Stephen Hawking Makes Black Holes Even More Perplexing.

Undoubtedly black holes are one of the most intriguing phenomena in our universe. The current interpretation of them, being a point mass that’s infinitely dense, is quite modern being only formalized some time back in the 1950s although the scientific roots can be traced back a bit further than that. Still they’re far from being a solved problem space as, like all things that use the word “infinite” in some capacity, their behaviour is a little strange especially when you try to explain them using different theories for how the universe works. To us laypeople we tend to be rooted in the general relativity explanation, however once you step into the world of quantum mechanics suddenly they start behaving differently creating quite the paradox.

Black HoleIn the world of general relativity passing across the event horizon, the point at which nothing (not even light) can escape, would be a somewhat peaceful affair. Since you would be in complete free fall at the time you wouldn’t experience a sudden jolt or anything that would indicate to you that this had happened (which makes black holes nightmare material for someone like me who has aspirations for space travel). After a while though you’d start to feel rather uncomfortable as the difference between the gravity at your head and feet became vastly different, eventually leading to a rather untimely demise at the hands of what has been dubbed spaghettification. However if you approach the same problem from the view of quantum mechanics you might not even get a chance to experience that as the world past the black hole’s event horizon is something vastly different.

The current hypothesis say that instead of the event horizon being a peaceful transition (although usually even getting to the event horizon would be quite nasty thanks to the accretion disks they usually sport) there instead exists a violent firewall of energy, ready to tear anything apart that crosses that horizon. Whilst the mechanics of this are well above my understanding it appears to be a quirk of Hawking Radiation, the process by which black holes “evaporate” over time. This evaporation occurs via entangled particles, one which leaves the black hole and another that falls back in. However this must mean that the entanglement is broken at some point which would release a lot of energy. This has led to a paradox which means that we have to either modify or abandon certain principles in physics, something which scientists don’t really like to do unless there’s a good reason to.

Hawking has recently weighed in on the topic through a paper on ArXiv which was then famously misinterpreted as him saying that there were no black holes at all. What he was actually saying was that there were no black holes in the traditional sense that there were distinct event horizons which, when passed, would not allow anything to escape. Instead Hawking has propose apparent horizons which are temporary artefacts, shifting around the black hole. This would then allow information to escape without necessitating the quantum firewall, preserving the more peaceful theory.

The new theory hasn’t been hit with resounding approval however as it raises almost as many questions as it answers. I’ll admit its quite intriguing, definitely worthy of further research, but with so many fundamental changes to the model of how black holes operate it’s hard to take it at face value. Still the mere fact that this has caused such ripples, even outside the scientific community, shows just how important this is to the wider world of physics.

 

Magnets: This is How They Work.

Whilst it’s always fun to quote the Insane Clown Posse’s single Miracles the answer to the question they posit, how do magnets work, is something that I myself had not completely understood. Most engineering students will know the relationship that electric currents and magnetism share but ask any of them to explain how natural magnets work and you’d likely get the same blank stare and jumbled answer I would have given before I had watched the video below:

What really fascinated me about natural magnets is the fact that its one of the few natural phenomena that can only be explained on a quantum level. This is likely the reason why the mechanism isn’t common knowledge as some of this stuff was above even my university level experience (although I was hardly a physics or hard science major). This new found understanding hasn’t exactly changed how I view the world but its certainly going to be a great little conversation topic come my next meeting with my more nerdy brethren.

How Gravity Really Works.

We’re all familiar with the concept of gravity: 2 bodies of mass, no matter how or small and regardless of the distance between them, are attracted to each other. As a force it’s pretty weak, even when the two bodies are close to each other, as you can overcome the gravitic forces of an entire planet by simply standing up. However the fact that its range is unlimited and that it doesn’t appear to discriminate as to what it acts on is what makes it such a fundamental force in our universe.

Whilst that understanding is probably good enough for a general understanding of its mechanism of action it in fact is far more complicated and interesting than that and the following video is probably the best way of describing it I’ve seen in a long time:

It’s not a perfect simulation, as they mention in the video, but it does give you a really great insight into how the general relativity way of explaining gravity works and how it works with other well known theories like orbital mechanics. I reckon with a little additional engineering you could make something that functioned like a nearly ideal gravity field something which would be awesome in a science museum like Questacon here in Canberra. It’s still great in its current form though and hopefully we see similar things make its way into the science labs at our schools.