StartsWithABang writes: When we look out into the Universe, we normally gain information about it by gathering light of various wavelengths. However, there are other possibilities for astronomy, including by looking for the neutrinos emitted by astrophysical sources — first detected in the supernova explosion of 1987 — and in the gravitational waves emitted by accelerating masses. These ripples in the fabric of space were theorized back in the early days of Einstein’s General Relativity, and experiments to detect them have been ongoing since the 1960s. However, in September of 2015, Advanced LIGO came online, and it was the first gravitational wave observatory that was expected to detect a real gravitational wave signal. The press conference on Thursday is where the collaboration will make their official announcement, and in the meantime, here’s an explainer of what gravitational waves are, what Advanced LIGO can teach us, and how.
StartsWithABang writes: When you look at the largest, most powerful optical telescopes in the world, they all have something in common: they all have holes in their central, primary mirrors. This is for a few reasons, including that they’re all reflectors, they all need to focus light somewhere in front of the mirror, and they all need to send that light somewhere to be recorded and analyzed. You can, in principle, focus the light somewhere off-axis, and many amateur telescopes do, but for the professionals, you lose more light that way than you would by simply having a hole in the center. In order to conserve the most light and maximize the image quality with the fewest artifacts, leaving a hole in the mirror is by far the best way to go.
StartsWithABang writes: Looking at the history of life on Earth, the fossil record shows something incontrovertible: in order for new forms of life to rise to dominance, it requires something to knock the prior forms from dominating their ecological niche. This can come about in any number of ways, but the most striking changes come from catastrophic events that wipe a large percentage of species off the Earth at once: a mass extinction event. While the asteroid strike that wiped out the dinosaurs was perhaps the most famous one, there is bountiful evidence that there were many others over the past 500 million years, with perhaps some periodicity to these events. Recently, reports have emerged that our Sun’s passage through the galactic plane, with periods of 26-30 million years, might correlate with these events. Yet a look at the fossil record shows extinction events do not have the required periodicity to account for that, nor do Oort cloud strikes account for the majority of such events on Earth.
StartsWithABang writes: Travel fast enough through the air, and you’ll exceed the speed of sound. The compressed air in front of you builds up, denser and denser, creating a shock wherever you’ve exceeded the sound barrier. In interstellar space, stars that move fast enough do the exact same thing. There doesn’t need to be sound in space for runaway stars to compress gas, heating it and causing it to radiate. Our infrared space telescopes, like NASA’s Spitzer and WISE, are ideal for identifying and imaging these stellar bow shocks. Hundreds have been identified so far, with thousands to millions likely in every galaxy overall.
StartsWithABang writes: When you think about the Multiverse, everyone thinks about the Universe beyond what’s accessible to us. But whether you think about more Universe like our own, multiple Universe that are disconnected from ours, an infinite number of parallel Universes, where possibly multiple copies of identical “yous” are entangled, or where the laws of physics are different from our own depends on what type of Multiverse you’re talking about. As it turns out, our standard picture of inflation, the Big Bang and quantum physics leads to some of these being quite likely, with others being grossly disfavored. Before you follow the speculations of a great many others down whatever rabbit-hole of thought they’d lead you, come learn about what’s known, what’s expected and what’s highly speculative (and unobservable) based on our current knowledge.
StartsWithABang writes: Give a planet a kick, and it goes into a more distant orbit around our star. Give it a hard enough kick, and it will reach escape velocity, leaving our Solar System forever. But if you gave it an almost hard enough kick, it would travel extremely far from the Sun, but it would eventually boomerang back towards the inner Solar System, with potentially disastrous, disruptive consequences. This applies to any system (not just the Solar System), including our own galaxy. In the Milky Way’s outskirts, there are high-velocity gas clouds, including one — the Smith Cloud — that’s moving towards us at a breakneck pace. Thanks to data from the Hubble Space Telescope, Andrew Fox and his team have just uncovered that this cloud came from our Milky Way, was almost ejected into intergalactic space, but is now on its way back, where in 30 million years it will collide with our galactic disk. The 11,000 light year-long cloud is expected to produce over 2 million new stars when it does.
StartsWithABang writes: The analogies between small-scale, living things and large-scale, cosmic entities are abundant: between a neuron and the Universe’s large-scale structure; between an atom and a solar system; between the stars in a galaxy and the atoms in a cell; between the cells in a living being and the galaxies in the Universe. It makes you wonder if, on a cosmic scale, some portion (or the whole) of the Universe could actually be alive and self-aware? While we don’t yet know how to test for that, what we can calculate is the amount of information that a self-aware being does exchange, and compare that to the amount of information that could conceivably be mutually exchanged by cosmic entities on various scales. The conclusion is that while the entire Universe can’t do it, on timescales much longer than the present age of the Universe, individual bound galaxies, groups and clusters perhaps could.
StartsWithABang writes: If you ask the average person where you can find new stars in our galaxy, they might (correctly) identify the Orion Nebula, a hotbed of star formation where thousands of new stars are presently being born. But at ~1,500 light years away, it’s not the closest place where new stars are forming, not by a long shot. Instead, the southern hemisphere holds a number of smaller “dark nebulae,” which are actually gas clouds. Many of them are in the process of forming brilliant new stars, including Lupus 3, which is giving birth to stars ranging from much less than the mass of our Sun all the way up to many times it mass and brightness.
StartsWithABang writes: As we peel back the layers of information deeper and deeper into the Universe’s history, we uncover progressively more knowledge about how everything we know today came to be. The discovery of distant galaxies and their redshifts led to expanding Universe, which led to the Big Bang and the discovery of very early phases like the cosmic microwave background and big bang nucleosynthesis. But before that, there was a period of cosmic inflation that left its mark on the Universe. What came before inflation, then? Did it always exist? Did it have a beginning? Or did it mark the rebirth of a cosmic cycle? Maddeningly, this information may forever be inaccessible to us, as the nature of inflation wipes all this information clean from our visible Universe.
StartsWithABang writes: When Einstein’s theory was first proposed as an alternative to Newtonian gravity, there were a number of subtle but important theoretical differences noted between the two. Einstein’s theory predicted gravitational redshift, time delays, bending of light and more. But what was perhaps most remarkable is that unlike Newton’s gravity, Einstein’s general relativity predicted an entirely new phenomenon: gravitational radiation. Much like how charged particles moving in a magnetic field accelerate and emit radiation in the form of photons, masses moving in a gravitational field accelerate and emit radiation in the form of gravitational waves, or ripples in the fabric of space itself. Even though these waves move at c, the speed of light in a vacuum, the expanding Universe carries them even farther, as these ripples ride atop the fabric of our expanding spacetime.
StartsWithABang writes: Later today, the richest lottery drawing in history — the $1.5 billion Powerball jackpot — will take place. While many outlets are encouraging people to purchase as many tickets as possible, it’s important to run through the mathematics and find out what your expected value is for each ticket. While a naive analysis shows that a jackpot in excess of about $245 million would lead to a break-even-or-better result, when you factor in taxes and split jackpots, you find that even for the $1.5 billion jackpot, your $2 ticket is only worth about $0.85.