Experiments Show Gravity Is Not an Emergent Phenomenon

One of the most exciting ideas in modern physics is that gravity is not a traditional force, like electromagnetic or nuclear forces. Instead, it is an emergent phenomenon that merely looks like a traditional force.

This approach has been championed by Erik Verlinde at the University of Amsterdam who put forward the idea in 2010. He suggested that gravity is merely a manifestation of entropy in the Universe, which always increases according to the second law of thermodynamics. This causes matter distribute itself in a way that maximises entropy. And the effect of this redistribution looks like a force which we call gravity.

Much of the excitement over Verlinde’s idea is that it provides a way to reconcile the contradictions between gravity, which works on a large scale, and quantum mechanics, which works on a tiny scale.

The key idea is that gravity is essentially a statistical effect. As long as each particle is influenced by a statistically large number of other particles, gravity emerges. That’s why it’s a large-scale phenomenon.

But today, Archil Kobakhidze at The University of Melbourne in Australia points to a serious problem with this approach. He naturally asks how gravity can influence quantum particles.

(via Technology Review)

Physicists Weigh Antimatter with Amazing Accuracy

A new measurement provides the most accurate weight yet of antimatter, revealing the mass of the antiproton (the proton’s antiparticle) down to one part in a billion, researchers announced today (July 28).

To give a sense of just how accurate their measurement was, researcher Masaki Hori said: “Imagine measuring the weight of the Eiffel Tower. The accuracy we’ve achieved here is roughly equivalent to making that measurement to within less than the weight of a sparrow perched on top. Next time it will be a feather.”

The result, detailed this week in the journal Nature, may help scientists investigate the mystery of why the universe is made of regular matter even though they suspect roughly equal parts of matter and antimatter were around just after the universe formed. When a particle, such as a proton, meets with its antimatter partner, the antiproton, the two annihilate each other in a powerful explosion.

(via LiveScience)

Building a better quantum computer with lasers and (impure) diamonds

If the development of a quantum computer were like motor racing, then we would currently be in the twisty-turny bit that comes before we barrel over the mountain and hit the long, fast straightaway. We know the requirements for quantum computing; we even know systems that kinda-sorta meet these requirements. But no existing quantum computing architecture—that is, how we make quantum bits (qubits) and perform operations on them—is really all that satisfying. If you don’t even know which materials are best for building a quantum computer, it makes progress awfully slow.

As a result, a lot of researchers have moved away from constructing proof-of-principle demonstrations of quantum computing, and are now trying to create clever ways to make qubits better behaved. A pair of papers look into the prospects for using impure diamonds as an architecture for quantum computing

(via Ars Technica)

I’ve always suspected that this is what’s going on in a cat’s head, with more opportunities for bloodshed.

earthlights:

this is probably strangely accurate.

(via proofmathisbeautiful)

The Puzzle Over Saturn’s Orbit (cont’d) 

 Many astronomers think our universe is filled with mysterious dark stuff that exerts a gravitational pull on big things like galaxies. In fact, most galaxies spin so fast that they would fly apart unless there were a substantial amount of this dark gloop holding them together.

But if dark matter does fill our galaxy, we ought to see it in our Solar System. There’s no shortage of dark matter detectors looking for the stuff. Most have drawn a blank and those that do claim to have seen it have been ridiculed.

There is an alternative hypothesis, however. This is the idea that Newton’s equations of motion work in a different way at the very low accelerations that stars experience as they orbit a galaxy.

(via Technology Review)