Physics

NASA created a rare, exotic state of matter in space

NASA has cooled a cloud of rubidium atoms to ten-millionth of a degree above absolute zero, producing the fifth, exotic state of matter in space. The experiment also now holds the record for the coldest object we know of in space, though it isn’t yet the coldest thing humanity has ever created. (That record still belongs to a laboratory at MIT.) The Cold Atom Lab (CAL) is a compact quantum physics machine, a device built to work in the confines of the International Space Station (ISS) that launched into space in May. Now, according to a statement from NASA, the device has produced its first Bose-Einstein condensates, the strange conglomerations of atoms that scientists use to see quantum effects play out at large scales. “Typically, BEC experiments involve enough equipment to fill a room and require near-constant monitoring by scientists, whereas CAL is about the size of a small refrigerator and can be operated remotely from Earth,” Robert Shotwell, who leads the experiment from the Jet Propulsion Laboratory, said in the statement. Despite that difficulty, NASA said, the project was worth the effort. A Bose-Einstein condensate on Earth is already a fascinating object; at super-low temperatures, atoms’ boundaries blend together, and usually-invisible quantum effects play out in ways scientists can directly observe. But cooling clouds of atoms to ultra-low temperatures requires suspending them using magnets or lasers. And once those magnets or lasers are shut off for observations, the condensates fall to the floor of the experiment and dissipate. In the microgravity of the ISS, however, things work a bit differently. The CAL can form a Bose-Einstein condensate, set it free, then have a significantly longer time to observe it before it drifts off, NASA wrote — as long as 5 or 10 seconds. And that advantage, as Live Science previously reported, should eventually allow NASA to create condensates far colder than any on Earth. As the condensates expand outside their container, they cool further. And the longer they have to cool, the colder they get.

Fascinating!!  For more, click on the text above.      🙂

Scientists teleport photon from Earth to orbit

For the first time, scientists have successfully teleported a photon from the ground to a satellite in orbit. It’s been 20 years since quantum scientists successfully teleported a photon over 10 miles, proving that quantum entanglement — a process that Albert Einstein called “spooky action at a distance” — was possible. The very unnatural phenomenon occurs when two quantum objects, such as photons, share a wave function. Since they come into existence at the exact same time and place, they share the same identity, even when separated. What happens to one happens to the other — wherever it exists. In 2010, a team at the University of Science and Technology of China in Shanghai set a record by teleporting photons over 60 miles on Earth. And now, just seven years later, they’ve outdone themselves, teleporting protons from a ground station in Tibet, 2½ miles above sea level, to a satellite orbiting Earth more than 310 miles away. It marks the first time an object has been teleported from our planet into space. Last year, China launched a research satellite called Micius into a sun-synchronous orbit, meaning it passes over the same point on Earth at the same time every day. Chinese scientists then created thousands of entangled pairs of photons and beamed one photon from each pair to Micius. After measuring both photons, they confirmed that 911 on Micius remained entangled with their companions on Earth. They’re more than identical twins. The two are one and the same. And, theoretically, the sky isn’t the limit. Photons are fragile; when they interact with matter on Earth and in Earth’s atmosphere, they lose entanglement. But in the vacuum of space, they can extend infinitely. And while the process won’t exactly succeed in making Captain Kirk demolecularize on the Starship Enterprise and remolecularize on a planet below, it has the potential nonetheless to change the world as we know it. Quantum teleportation is seen as the basis for unimaginably high-speed communication and foolproof cryptography. Since the two objects are not twins but actually the same object, what happens to one happens instantaneously to the other. Beam that up, Scottie.

Very cool!!

Why Does Gravity Move At The Speed Of Light?

If you looked out at the Sun across the 93 million miles of space that separate our world from our nearest star, the light you’re seeing isn’t from the Sun as it is right now, but rather as it was some 8 minutes and 20 seconds ago. This is because as fast as light is — moving at the speed of light — it isn’t instantaneous: at 299,792.458 kilometers per second (186,282 miles per second), it requires that length of time to travel from the Sun’s photosphere to our planet. But gravitation doesn’t necessarily need to be the same way; it’s possible, as Newton’s theory predicted, that the gravitational force would be an instantaneous phenomenon, felt by all objects with mass in the Universe across the vast cosmic distances all at once. But is that right? If the Sun were to simply wink out of existence, would the Earth immediately fly off in a straight line, or would it continue orbiting the Sun’s location for another 8 minutes and 20 seconds? If you ask General Relativity, the answer is much closer to the latter, because it isn’t mass that determines gravitation, but rather the curvature of space, which is determined by the sum of all the matter and energy in it. If you were to take the Sun away, space would go from being curved to being flat, but that transformation isn’t instantaneous. Because spacetime is a fabric, that transition would have to occur in some sort of “snapping” motion, which would send very large ripples — i.e., gravitational waves — through the Universe, propagating outward like ripples in a pond. The speed of those ripples is determined the same way the speed of anything is determined in relativity: by their energy and their mass. Since gravitational waves are massless yet have a finite energy, they must move at the speed of light! Which means, if you think about it, that the Earth isn’t directly attracted to the Sun’s location in space, but rather to where the Sun was located a little over 8 minutes ago. If that were the only difference between Einstein’s theory of gravity and Newton’s, we would have been able to instantly conclude that Einstein’s theory was wrong. The orbits of the planets were so well studied and so precisely recorded for so long (since the late 1500s!) that if gravity simply attracted the planets to the Sun’s prior location at the speed of light, the planets’ predicted locations would mismatch severely with where they actually were. It’s a stroke of brilliance to realize that Newton’s laws require an instantaneous speed of gravity to such precision that if that were the only constraint, the speed of gravity must have been more than 20 billion times faster than the speed of light! But in General Relativity, there’s another piece to the puzzle that matters a great deal: the orbiting planet’s velocity as it moves around the Sun. The Earth, for example, since it’s also moving, kind of “rides” over the ripples traveling through space, coming down in a different spot from where it was lifted up. It looks like we have two effects going on: each object’s velocity affects how it experiences gravity, and so do the changes that occur in gravitational fields. What’s amazing is that the changes in the gravitational field felt by a finite speed of gravity and the effects of velocity-dependent interactions cancel almost exactly! The inexactness of the cancellation is what allows us to determine, observationally, if Newton’s “infinite speed of gravity” model or Einstein’s “speed of gravity = speed of light” model matches with our Universe. In theory, we know that the speed of gravity should be the same as the speed of light. But the Sun’s force of gravity out here, by us, is far too weak to measure this effect. In fact, it gets really hard to measure, because if something moves at a constant velocity in a constant gravitational field, there’s no observable affect at all. What we’d want, ideally, is a system that has a massive object moving with a changing velocity through a changing gravitational field. In other words, we want a system that consists of a close pair of orbiting, observable stellar remnants, at least one of which is a neutron star. As one or both of these neutron stars orbit, they pulse, and the pulses are visible to us here on Earth each time the pole of a neutron star passes through our line-of-sight. The predictions from Einstein’s theory of gravity are incredibly sensitive to the speed of light, so much so that even from the very first binary pulsar system discovered in the 1980s, PSR 1913+16 (or the Hulse-Taylor binary), we have constrained the speed of gravity to be equal to the speed of light with a measurement error of only 0.2%! That’s an indirect measurement, of course. We were able to do another type of indirect measurement in 2002, when a chance coincidence lined up the Earth, Jupiter, and a very strong radio quasar (QSO J0842+1835) all along the same line-of-sight! As Jupiter moved between Earth and the quasar, the gravitational bending of Jupiter allowed us to measure the speed of gravity, ruling out an infinite speed and determining that the speed of gravity was between 2.55 × 10^8 and 3.81 × 10^8 meters-per-second, completely consistent with Einstein’s predictions. Ideally, we’d be able to measure the speed of these ripples directly, from the direct detection of a gravitational wave. LIGO just saw the first one, after all! Unfortunately, due to our inability to correctly triangulate the location from which these waves originated, we don’t know from which direction the waves were coming. By calculating the distance between the two independent detectors (in Washington and Louisiana) and measuring the difference in the signal arrival time, we can determine that the speed of gravity is consistent with the speed of light, but can only place an absolute constraint that it’s equal to the speed of light within 70%. Still, it’s the indirect measurements from very rare pulsar systems that give us the tightest constraints. The best results, at the present time, tell us that the speed of gravity is between 2.993 × 10^8 and 3.003 × 10^8 meters per second, which is an amazing confirmation of General Relativity and a terrible difficulty for alternative theories of gravity that don’t reduce to General Relativity! (Sorry, Newton!) And now you know not only what the speed of gravity is, but where to look to figure it out! -Astrophysicist and author Ethan Siegel is the founder and primary writer of Starts With A Bang. Follow him on Twitter, Facebook, G+, Tumblr, and order his book: Beyond The Galaxy, today!

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