Physics

Amazingly, 95% of the make-up of the universe is stuff we can't see, according to cosmologists. Find out more about dark energy and dark matter, which far surpasses the amount of visible mass in the universe.

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Quantum Levitation on TED

Sunday July 22, 2012

One of the most visually impressive recent discoveries in physics is the phenomenon of quantum levitation, in which a superconductor becomes suspended within a magnetic field. Quantum locking goes even a step beyond this. This isn't the same as just magnetic repulsion, though, because the superconductor itself doesn't have any electrical charge. Instead, it repulses the magnetic field around it, but if the superconductor is thin enough, then some of the field pops through the material due to the quantum Meissner effect. The result is that the magnetic field actually "locks" the superconductor in place relative to the source of the magnetic field.
Physicist Boaz Almog from Tel Aviv University recently gave a TED talk where he demonstrates the phenomenon. It's available on our list of TED physics videos. (Though it may not be quite as cool as when Stephen Colbert quantum levitated ice cream.)
Image Source: Tel Aviv University superconductor group

Brian Greene on the Higgs Field: Mass Molasses of the Universe

Saturday July 21, 2012

The Higgs boson is getting a lot of press since the July 4 CERN announcement that it may have been detected by the Large Hadron Collider, but the boson is only part of the story. See, the real work isn't done by the boson itself, but by the Higgs field, which theoretical physicist Peter Higgs proposed in 1964 as a means of explaining how the Standard Model of quantum physics could explain the mass shown by fundamental particles. The Higgs boson is just a physical manifestation of that field, created when you shove enough energy into it. (In quantum physics, fields and particles are viewed as different ways of representing the same basic physical entity. This is, of course, a bit of an over-simplification, but it's close enough.)
Here is how theoretical physicist Brian Greene explained the Higgs field on the Charlie Rose show on PBS:

Mass is the resistance an object offers to having its speed changed. You take a baseball. When you throw it, your arm feels resistance. A shotput, you feel that resistance. The same way for particles. Where does the resistance come from? And the theory was put forward that perhaps space was filled with an invisible "stuff," an invisible molasses-like "stuff," and when the particles try to move through the molasses, they feel a resistance, a stickiness. It's that stickiness which is where their mass comes from.... That creates the mass....
... it's an elusive invisible stuff. You don't see it. You have to find some way to access it. And the proposal, which now seems to bear fruit, is if you slam protons together, other particles, at very, very high speeds, which is what happens at the Large Hadron Collider... you slam the particles together at very high speeds, you can sometimes jiggle the molasses and sometimes flick out a little speck of the molasses, which would be a Higgs particle. So people have looked for that little speck of a particle and now it looks like it's been found.

Greene isn't the only one out there talking about the Higgs boson, of course. There's also this nice post from Jim Baggott, over at the Huffington Post, which helps to shed some light on why physicists are so excited, and I had an earlier post where I collected together quite a lot of the early explanations that spread across the web in the wake of the LHC announcement.

Beyond the Higgs: The Other Bosons

Sunday July 15, 2012

With all the excitement about the Higgs boson, it seems like a good time to think about the other bosons that we know about. The Standard Model of particle physics contains a total of four bosons (not counting the theoretical Higgs). These bosons are considered force carriers, because they communicate the three fundamental forces of physics that are explained by quantum physics. The bosons associated with these three forces are:
There are four bosons because the W boson and Z boson work together to mediate the weak nuclear force.
In addition to the above bosons, theories of quantum gravity also propose another type of boson, the graviton, which would mediate the gravitational force. To date, however, this boson has not been confirmed.