StartsWithABang (3485481) writes "Finite to the past, infinite to the past, or cyclical in nature: those are the three options for the nature of our spacetime. We can trace our Universe's history back billions of years, to the earliest moments of the Big Bang and even before to the epoch of cosmic inflation that preceded it, but was there truly a singularity from which space-and-time emerged? Here's the limits of our knowledge on that front."
StartsWithABang (3485481) writes "There’s a problem with our view of the night sky: beautiful though it is, we’re incapable of seeing with our own eyes what the Universe is like from an outsider’s perspective. No matter where we are, we’re stuck inside our own galaxy, with all its light-blocking and obscuring properties. But there’s a trick to seeing through it: some wavelengths of light are more transparent to our galaxy’s material than others! And when we get there — when we view it — the rewards are incomparable, including what we learn about what’s there in our own Universe. A great busting of the myth that if we were plunked down at random, we probably wouldn't see a single galaxy."
StartsWithABang (3485481) writes "After successfully landing on a comet with all 10 instruments intact, but failing to deploy its thrusters and harpoons to anchor onto the surface, Philae bounced, coming to rest in an area with woefully insufficient sunlight to keep it alive. After exhausting its primary battery, it went into hibernation, most likely never to wake again. We’ll always be left to wonder what might have been if it had functioned optimally, and given us years of data rather than just 60 hours worth. The thing is, it wouldn’t have needed to function optimally to give us years of data, if only it were better designed in one particular aspect: powered by Plutonium-238 instead of by solar panels."
StartsWithABang (3485481) writes "The particles of the standard model, some type of dark matter and dark energy, and the four fundamental forces. That’s all there is, right? But that might not be the case at all. Dark energy may not simply be the energy inherent to space itself, but rather a dynamical property that emerges from the Universe: a sort of fifth force. This is speculation that's been around for over a decade, but there hasn't been a way to test it until now. If this is the case, it may be accessible and testable by simply using presently existing vacuum chamber technology!"
StartsWithABang (3485481) writes "The largest galaxies in the Universe all have a few things in common: they all contain many trillions of stars, they all contain many times their stellar mass in the form of dark matter, and they’re all found towards the centers of great galactic clusters. Oh, and one more thing: none of them are spiral galaxies! Why are the largest spiral galaxies in the Universe only a few times the size of our Milky Way, but the largest galaxies overall are hundreds or even a thousand times as big as our home galaxy? The astrophysics behind the largest galaxies in the Universe."
StartsWithABang (3485481) writes "For centuries, the argument has raged about whether light is — at its fundamental core — a wave or a particle. More recently, not only have all the fundamental particles gotten in on that argument, but also about which interpretation of quantum mechanics is the right one. Are there many parallel Universes? Is the Universe in an indeterminate state? Are there nonlocal, hidden variables determining everything? Or — with the original formulation — did Niels Bohr have it right all along? As it turns out, these may not even be the right questions to be asking; if they all give the same observational predictions, we may be learning only about our own preconceptions by favoring one interpretation over another."
StartsWithABang (3485481) writes "Launched from the Rosetta satellite, on a mission 10 years in the making, the space probe Philae just successfully landed on a comet, the first time in history humanity has managed to make such a thing happen. But other than sounding cool, what have we gained? Here's a redux of the technical challenges and achievements, the scientific knowledge to come and when we can expect the payoff!"
StartsWithABang (3485481) writes "When our science fiction fills our heads with ideas that could make our lives tremendously improved, we like to believe it’s only a matter of time before technology catches up with our imaginations. Indeed, tricorders, wireless communicators and rocket ships were just some of the breakthroughs predicted by sci-fi on their way to becoming commonplace technology. But many of our dreams are a long way from becoming reality, including human-sized teleporters, wormholes and time travel. Here's what happens when science fiction runs into the cold, hard wall that is scientific reality."
StartsWithABang (3485481) writes "Out beyond Neptune, the last of our Solar System’s gas giants, the icy graveyard of failed planetesimals lurks: the Kuiper Belt. Among these mixes of ice, snow, dust and rock are a number of worlds — possibly a few hundred — massive enough to pull themselves into hydrostatic equilibrium. The most famous among them are Pluto, the first one ever discovered, and Eris, of comparable size but undoubtedly more massive. But there’s an even larger, more massive object from the Kuiper Belt than either of these, yet you never hear about it: it’s Triton, the largest moon of Neptune, a true Kuiper Belt object!"
StartsWithABang (3485481) writes "One of the things we learn about the gravitational force is that it has an “infinite range” to it. Because it’s a ~1/r^2 force, and because as you move radially away from the source, a sphere spreads out (in surface area) as ~r^2, you don’t lose anything as you move farther and farther away. So long as you intercept the same angular size on the sky, you’ll experience the same amount of force. But you can’t move arbitrarily far away from a source and still feel its gravitation! Despite being an infinite range force, our Universe has only been around a finite amount of time, and signals only propagate at a finite speed. Here's the reconciliation of these two seemingly contradictory facts."
StartsWithABang (3485481) writes "We like to think of nature as beautiful, elegant and infallible. Yet our notions of what’s beautiful and elegant don’t always line up with what reality gives us. Take the notion of symmetry, for example: the gravitational force is symmetric, always exerting equal magnitude forces on whatever two masses it occurs between. But as similar as they are, electricity and magnetism are not symmetric at all. There are no such things as magnetic charges or currents, and this has huge ramifications for physics. But it didn’t need to be this way at all; the Universe could have been symmetric in this fashion. The fact that it isn’t teaches us all sorts of things, including why the idea of a Grand Unified Theory (GUT) may not be in the cards for our Universe at all."
StartsWithABang (3485481) writes "If you wanted to travel to the stars — to star systems beyond our own — you’d better be prepared to take your sweet time. Even at the speeds the Apollo astronauts traveled to the Moon, it would take millions of years to reach even the next nearest star beyond our own, Proxima Centauri. And yet, General Relativity admits an astounding possibility to short-cut the great cosmic distances by punching a hole in spacetime, connecting two far-separated events to one another through a cosmic bridge: a wormhole. What strikes us as the most fanciful of science fiction ideas may legitimately someday become science fact, and if it does, here's the physics of how it will work!"
StartsWithABang (3485481) writes "The Big Bang takes us back to very early times, but not the earliest. It tells us the Universe was in a hot, dense state, where even the possibility of forming neutral atoms was impossible due to the incredible energies of the Universe at that time. The patterns of fluctuations that are left over from that time give us insight into the primordial density fluctuations that our Universe was born with. But there’s an additional signature encoded in this radiation, one that’s much more difficult to extract: polarization. While most of the polarization signal that’s present will be due to the density fluctuations themselves, there’s a way to extract even more information about an even earlier phenomenon: gravitational waves that were present from the epoch of cosmic inflation! Here's the physics on how that works, and how we'll find whether BICEP2 was right or not."
StartsWithABang (3485481) writes "When you consider the short life of a star cluster — from a collapsing molecular cloud to a nebula rich in gas and dust to a bright cluster of shining stars until the time it dissociates — you might think that they’d all be the same, except for a few details like mass and density profile. But then how would you explain Messier 26? Here’s a cluster, 89 million years old, whose core is almost totally devoid of stars, exactly where we’d expect it to be densest. You might think there’s some leftover, nebulous dust, but in a cluster this old, that’s unheard of! You might also think that there’s just a stellar deficiency, but that’s also unheard of! As it turns out there's a simple explanation: the intervening dust of our galaxy, that would have shocked and surprised the original discoverer of this object, who was simply disappointed at his findings."
StartsWithABang (3485481) writes "The Big Bang — and General Relativity in general — teaches us that in an expanding Universe, it’s the fabric of space itself that evolves over time. One of the consequences of this is a bit puzzling: that since the Universe was denser in the past, it must have been hotter in the past as well. But if each individual photon has redshifted to longer wavelengths, and the energy of every photon is inversely proportional to that wavelength, does that mean that energy is actually destroyed in an expanding Universe? The answer (surprisingly) is no, thanks to the relationship between work and energy."