Physics

No sunshine, no moonlight, no stardust, no sign of romance

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We suggest that advanced civilizations could cloak their presence, or deliberately broadcast it, through controlled laser emission.

Such emission could distort the apparent shape of their transit light curves with relatively little energy, due to the collimated beam and relatively infrequent nature of transits.

We estimate that humanity could cloak the Earth from Kepler-like broad-band surveys using an optical monochromatic laser array emitting a peak power of ∼30 MW for ∼10 hours per year.

{ Monthly Notices of the Royal Astronomical Society | Continue reading }

Don’t fall into the trap of thinking because a line of attack didn’t work at first that it isn’t effective. Repetition is key.

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Have you heard the one about the biologist, the physicist, and the mathematician? They’re all sitting in a cafe watching people come and go from a house across the street. Two people enter, and then some time later, three emerge. The physicist says, “The measurement wasn’t accurate.” The biologist says, “They have reproduced.” The mathematician says, “If now exactly one person enters the house then it will be empty again.”

{ Nautilus | Continue reading }

‘Everybody is raving about the Trump Home Mattress.’ —@realDonaldTrump

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Excitement is in the air at the Large Hadron Collider (LHC), the powerful accelerator at CERN (the European Laboratory for Particle Physics) near Geneva. Last year, researchers there recorded faint but extremely promising signs of what could be a new particle that does not fit within the current theoretical model. The LHC is now about to resume operation after being shut down since December for annual maintenance. If its next run confirms the existence of the new particle, that could open the long-sought passage to ‘the new physics’ – and, hopefully, answer some big, longstanding questions.

Experimental physicists and theorists have always worked together trying to understand nature’s underlying laws. Out of this collaboration emerged the ‘Standard Model’, which describes the fundamental particles and the ways that they interact to form all matter we see around us. At some times, experimental discoveries prompted fresh insights or confirmed what theorists already suspected. At others, theoretical predictions sent the experimentalists on a specific search. This was the case back in 1964 when physicists Robert Brout, François Englert and Peter Higgs predicted the existence of the Higgs boson, the particle that was discovered in 2012.

The Higgs boson filled in the last missing piece of the Standard Model, but this model is itself clearly incomplete. None of its particles has the properties of dark matter, a mysterious entity that is five times as prevalent as all the ordinary matter (everything made of atoms, which in turn are built from quarks and electrons) visible in the stars and galaxies. The Standard Model also does not explain the wide range of masses of the fundamental particles, nor why antimatter seems to have nearly completely disappeared, leaving the Universe filled almost exclusively with matter.

That is why, after spending nearly 60 years building the Standard Model, particle physicists are now terribly excited at the prospect of finally breaking it. The flaws of the model were well known, but no one knows what the right model might be. Theorists have been stuck for decades, exploring a vast array of ideas but lacking the data to tell them if they were on the right path. Only an experimental breakthrough can help them move forward, and the LHC might have already made it.

{ Aeon | Continue reading }

‘Being is the absence that appearances conceal.’ –Georges Bataille

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The universe may have existed forever, according to a new model that applies quantum correction terms to complement Einstein’s theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once.

The widely accepted age of the universe, as estimated by general relativity, is 13.8 billion years. In the beginning, everything in existence is thought to have occupied a single infinitely dense point, or singularity. Only after this point began to expand in a “Big Bang” did the universe officially begin.

Although the Big Bang singularity arises directly and unavoidably from the mathematics of general relativity, some scientists see it as problematic because the math can explain only what happened immediately after—not at or before—the singularity.

{ Phys.org | Continue reading }

The night that hides things from us

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Penrose and many others argue from practical considerations, Godel’s theorem, and on philosophical grounds, that consciousness or awareness is non-algorithmic and so cannot be generated by a system that can be described by classical physics, such as a conventional computer, but could perhaps be generated by a system requiring a quantum (Hilbert space) description. Penrose suspects that aspects of quantum physics not yet understood might be needed to explain consciousness. In this paper we shall see that only known quantum physics is needed to explain perception.

{ James A. Donald | Continue reading }

photo { Martin Parr }

When most I wink, then do my eyes best see

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Einstein wondered what would happen if the Sun were to suddenly explode. Since the Sun is so far away that it takes light eight minutes to travel to Earth, we wouldn’t know about the explosion straight away. For eight glorious minutes we’d be completely oblivious to the terrible thing that was about to happen.

But what about gravity? The Earth moves in an ellipse around the Sun, due to the Sun’s gravity. If the Sun wasn’t there, it would move off in a straight line. Einstein’s puzzle was when that would happen: straight away, or after eight minutes? According to Newton’s theory, the Earth should know immediately that the Sun had disappeared. But Einstein said that couldn’t be right. Because, according to him, nothing can travel faster than the speed of light — not even the effects of gravity. […]

Before Einstein people thought of space as stage on which the laws of physics play out. We could throw in some stars or some planets and they would move around on this stage.

Einstein realised that space isn’t as passive as that. It is dynamic and it responds to what’s happening within it. If you put something heavy in space — let’s say a planet like Earth — then space around it gives a little. The presence of the planet causes a small dent in space (and in fact, in time as well). When something else moves close to the planet — say the Moon — it feels this dent in space and rolls around the planet like a marble rolling in a bowl. This is what we call gravity. […] Stars and planets move, causing space to bend in their wake, causing other stars and planets to move, causing space to bend in their wake. And so on. This is Einstein’s great insight. Gravity is the manifestation of the curvature of space and time.

{ Plus Magazine | Part One | Part Two }

‘The road up and the road down is one and the same.’ –Heraclitus

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Our best theories of physics imply we shouldn’t be here. The Big Bang ought to have produced equal amounts of matter and antimatter particles, which would almost immediately annihilate each other, leaving nothing but light.

So the reality that we are here – and there seems to be very little antimatter around – is one of the biggest unsolved mysteries in physics.

In 2001, Tanmay Vachaspati from Arizona State University offered a purely theoretical solution. Even if matter and antimatter were created in equal amounts, he suggested that as they annihilated each other, they would have briefly created monopoles and antimonopoles – hypothetical particles with just one magnetic pole, north or south.

As the monopoles and antimonopoles in turn annihilated each other, they would produce matter and antimatter. But because of a quirk in nature called CP violation, that process would be biased towards matter, leaving the matter-filled world we see today.

If that happened, Vachaspati showed that there should be a sign of it today: twisted magnetic fields permeating the universe. […] So Vachaspati and his colleagues went looking for them in data from NASA’s Fermi Gamma ray Space Telescope.

{ New Scientist | Continue reading }

related { Rogue antimatter found in thunderclouds }

everything is stooopid

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Every 250m years the sun, with its entourage of planets, completes a circuit of the Milky Way. Its journey around its home galaxy, though, is no stately peregrination. Rather, its orbit oscillates up and down through the galactic disc. It passes through that disc, the place where most of the galaxy’s matter is concentrated, once every 30m years or so.

This fact has long interested Michael Rampino of New York University. He speculates that it could explain the mass extinctions, such as that of the dinosaurs and many other species 66m years ago, which life on Earth undergoes from time to time. Palaeontologists recognise five such humongous events, during each of which up to 90% of species have disappeared. But the fossil record is also littered with smaller but still significant blips in the continuity of life.

Many hypotheses have been put forward to explain these extinctions (and the events may, of course, not all have the same explanation). The two that have most support are collisions between Earth and an asteroid or comet, and extended periods of massive volcanic activity. Dr Rampino observed some time ago that cometary collisions might be triggered by gravitational disruptions of the Oort cloud, a repository of comets in the outermost part of the solar system. That would send a rain of them into the part of space occupied by Earth. This has come to be known as the Shiva hypothesis, after the Hindu god of destruction. […]

In his latest paper, Dr Rampino speculates that the real culprit may be not stars, but dark matter—and that this might explain the volcanism as well.

{ The Economist | Continue reading }

‘Anaxagoras agrees with Leucippus and Democritus that the elements are infinite.’ –Aristotle

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New theories suggest the big bang was not the beginning, and that we may live in the past of a parallel universe.

[…]

Time’s arrow may in a sense move in two directions, although any observer can only see and experience one.

{ Scientific American | Continue reading }

photo { Tania Shcheglova and Roman Noven }

The time is out of joint

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O’Brian oversees America’s master clock. It’s one of the most accurate clocks on the planet: an atomic clock that uses oscillations in the element cesium to count out 0.0000000000000001 second at a time. If the clock had been started 300 million years ago, before the age of dinosaurs began, it would still be keeping time — down to the second. […]

At the nearby University of Colorado Boulder is a clock even more precise than the one O’Brian watches over. […] This new clock can keep perfect time for 5 billion years.”It’s about the whole, entire age of the earth,” says Jun Ye, the scientist here at JILA who built this clock. […]

But this new clock has run into a big problem: This thing we call time doesn’t tick at the same rate everywhere in the universe. Or even on our planet.

Right now, on the top of Mount Everest, time is passing just a little bit faster than it is in Death Valley. That’s because speed at which time passes depends on the strength of gravity. Einstein himself discovered this dependence as part of his theory of relativity, and it is a very real effect.

The relative nature of time isn’t just something seen in the extreme. If you take a clock off the floor, and hang it on the wall, Ye says, “the time will speed up by about one part in 1016.” […] Time itself is flowing more quickly on the wall than on the floor. These differences didn’t really matter until now. But this new clock is so sensitive, little changes in height throw it way off. Lift it just a couple of centimeters, Ye says, “and you will start to see that difference.” […]

The world’s current time is coordinated between atomic clocks all over the planet. But that can’t happen with the new one.

{ NPR | Continue reading }

photo { Petra Collins }

‘The freaks of chance are not determinable by calculation.’ —Thucydides

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An interesting idea is that the universe could be spontaneously created from nothing, but no rigorous proof has been given. In this paper, we present such a proof based on the analytic solutions of the Wheeler-DeWitt equation.

{ arXiv | Continue reading | more }

Three quarks for Muster Mark

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In a little over a century, we’ve discovered that what we once thought was the fundamental, smallest unit of matter — the atom — is actually made up of even smaller particles: nuclei and electrons. The nuclei themselves are made of protons and neutrons, and those protons and neutrons are made of still smaller particles: quarks and gluons.

Those particles — quarks, gluons, and electrons — are just some of the particles that cannot be broken up into smaller constituents to the best of our knowledge. All told, when we count up the fundamental particles that we know of, the ones that cannot be broken apart into anything smaller or lighter, we count a number of different types:

— six quarks (and their antiquark counterparts), each coming in three different color possibilities and two different spins,

— three charged leptons, the electron, muon and tau (and their anti-lepton counterparts), each allowed two different spin states,

— three neutral leptons, the neutrinos, along with the three anti-neutrinos, where the neutrinos all have a left-handed spin and the antis have a right-handed spin,

— the gluons, which all have two different spin states and which come in eight color varieties,

— the photon, which has two different allowable spins,

— the W-and-Z bosons, which come in three types (the W+, W-, and Z) and have three allowable spin states apiece (-1, 0, and +1), and

— the Higgs boson, which exists in only one state.

That’s the Standard Model of elementary particles. […] However, we know there must be more to the Universe, as this doesn’t account for dark matter, for one. Furthermore, there are theoretical limitations and inconsistencies to the physics we presently know and so we suspect there’s more physics beyond the Standard Model to explain it.

{ Ethan Siegel | Continue reading }