StartsWithABang writes: In a four-dimensional Universe (3 space and 1 time), it’s easy to get lost. If you take a random walk, the chances of you coming back to your original starting point in a finite number of steps gets lower and lower the more dimensions you have. If all you could do was walk along a sheet of paper – or even better, along the surface of a pipe – you’d have a much greater chance of return than if you had all three spatial dimensions to deal with. There’s an interesting property of mathematics that if you treat all four dimensions as “space” rather than spacetime and you add in the laws of quantum mechanics, then at very short distance scales, the probability of a random walker returning to their original position behaves like they’re in a two dimensional Universe, rather than four. Could this be a way of reducing the quantum gravity problem from a difficult (perhaps unsolvable) 4D case to an easier (and solvable) 2D one?
StartsWithABang writes: If you want to know what types of stars are found all throughout a galaxy, looking at our own simply won’t do: too much of it is obscured by the plane and our position within it. But there’s an even more impressive galaxy – Andromeda – just 2.5 million light years away. And thanks to the power of the Hubble Space Telescope, we’ve not only resolved individual stars within it, we’ve resolved over a hundred million of them. But when we look towards the center versus at the outskirts of the disk, or even into the halo, we find something very, very different: older, redder, fainter and less-evolved stars. Even more spectacularly: beyond them, a rich slew of distant galaxies, visible out to distances exceeding a billion light years.
StartsWithABang writes: When dark energy was discovered, and the expansion of the Universe was shown to be accelerating, there was concurrently another puzzle that received much less attention: the problem of the Great Attractor. Galaxies appear to move due to both the Hubble expansion and the local gravitational field, but the gravity from the galaxies we saw didn’t account for all the motion. There must have been an additional set of masses, revealed only in the 2010s with the identification of the supercluster Laniakea. All the galaxies in our local neighborhood are headed towards it, but are we moving fast enough to overcome the expansive pull of dark energy? The answer looks to be no.
StartsWithABang writes: Today marks the 50th anniversary of the premiere of Star Trek, our first science fiction adventure that promised a positive view of the future, ushered in by technology and humanity’s best traits. In addition to a utopia where maladies like hunger, disease and poverty were eradicated, Star Trek promised a future where technology was widely available and sufficiently advanced to the benefit of all of humanity. While many of these imagined advances in technology have been met or even exceeded already, such as in the field of medical diagnostics and communication, others like warp drive and the Star Trek transporter may never come to fruition. No matter how much your technology advances, you still can’t circumvent the laws of nature.
StartsWithABang writes: If you want to find dark matter directly, your best hope is to gather a tremendous number of nucleons for it to interact with, wait an incredibly long period of time, and devise a device surrounding it capable of detecting even a single potential collision while distinguishing it from any background signals. That was the exact idea behind LUX, the Large Underground Xenon detector. After a 20 month run with more than a third of a ton of liquid Xenon inside, the LUX collaboration has released their final results. Not only did they achieve four times the sensitivity they anticipated, but they didn’t detect a single event. This eliminates most models of WIMP dark matter, including from scenarios like supersymmetry and extra dimensions.
StartsWithABang writes: Less than a decade after the first human was launched into space, astronauts Neil Armstrong, Buzz Aldrin and Michael Collins journeyed from the Earth to the Moon. For the first time, human beings descended down to the lunar surface, opened the hatch, and walked outside. Humanity had departed Earth and set foot onto another world. While Armstrong and Aldrin walked on the surface, collecting now-iconic photos, deploying science instruments and returning hundreds of pounds of lunar samples, Michael Collins orbited overhead, embarking on a missing that no human being had undertaken before. Forty-seven years later, humanity has never had a bigger breakthrough as far as crewed space exploration goes. Relive it all in this incredible video, made exclusively with NASA archival photos.
StartsWithABang writes: On July 20, 1976, the Viking 1 lander touched down onto the Martian surface, followed just a few weeks later by Viking 2. On board both landers were a suite of three experiments designed to look for signs of life. While the Gas Chromatograph-Mass Spectrometer and the Gas Exchange experiment both came back negative, the Labeled Release experiment — where nutrient-rich molecules tagged with radioactive carbon-14 were added to the Martian soil — gave off a positive release of radioactive CO2. Did our first trip to Mars really find life after all?
StartsWithABang writes: When you look at an active, massive star-forming region like the Orion Nebula, you expect to find new stars dominating, blowing off the gas and eventually bringing the episode of star formation to an end. Previous visible light studies of Orion – the closest region to Earth of massive star formation – seemed to indicate exactly this, with star populations dropping off at masses below about 25% that of our Sun. But a new view of this nebula in the infrared, the deepest ever thanks to ESO’s HAWK-I instrument, showed that we had it wrong. In the regions where star formation was most intense, there were more than ten times as many brown dwarfs – or failed stars – than we had thought previously. This could have profound implications for the number of planets formed in a nebula like this, and the next generation of 30-meter-class telescopes should find out.
StartsWithABang writes: If you’re talking to someone across the same room, what the two of you perceive as time and space might match up perfectly, to the limit of what each of you can measure. But if one of you moves quickly relative to the other, if you experience different gravitational fields or spacetime curvatures, or if the space of the Universe between you is expanding, times and distances will cease to line up. This isn’t a flaw of yours in any way, but rather an inevitable feature of special and general relativity. Observers in different locations can never agree on definitions of distance and time, particularly in an expanding Universe. So we invent some alternate definitions for differently scaled types of distance and time: conformal time and comoving distance, to help us understand what’s going on in the Universe.
StartsWithABang writes: Let there be light! You’d think that would be enough: that you form stars in the Universe, you see those stars in the Universe, and that tells you about what’s out there. If only it were that simple. In order to truly see the first stars, you need a lot more that just starlight: you need that light to be able to freely travel through space. And — as bad luck would have it — visible light, the kind of light we’ve built our telescopes to see, is opaque to neutral atoms. In other words, it’s not enough to simply have a Universe full of stars; you need a transparent Universe full of stars, otherwise they’ll be invisible to our eyes!
StartsWithABang writes: We think of the Universe as all there ever is, was or will be. But, in fact, there's a limit to the most distant galaxies, stars, matter and radiation we can see. The hot Big Bang occurred a finite amount of time ago, and hence the amount of the Universe accessible to us through any observational means is necessarily limited. What lies beyond that? According to our best explanations and theories, there's more Universe. But beyond that, the combination of cosmic inflation and what we know about quantum field theory indicates that there are multitudes of individual pockets that contain entirely disconnected Universes, each beginning with their own Big Bang, some of which may even have different fundamental laws and constants from our own.
StartsWithABang writes: When most people think of the Kuiper belt, they think of a population of objects just beyond Neptune, with slightly larger, more elliptical and more inclined orbits. As new discoveries like the recent 2015 RR245 show, however, there are a great many additional objects in the scattered disk with different orbital parameters that are much harder to find. These objects are quite likely to exist in great numbers, and are very difficult to find with current technology. Our observational biases may have strong and profound implications for our Solar System, including for the potential existence or non-existence of the hypothetical Planet Nine. There's a whole lot more we still need to find out before any firm conclusions are drawn.
StartsWithABang writes: Nearly 1,000 years ago, in 1054, a massive star in the constellation of Taurus, invisible at some 6,500 light years away, exploded in a type II supernova. Today, its remnant measures 10 light years across, while its inner core has a rapidly spinning neutron star that rotates in a mere 30 milliseconds. Hubble and Chandra not only reveal the nebular structure, but also show the inner, pulsing region, revealing matter accelerated by electrons moving at nearly the speed of light. It's a beautiful show unlike anything we've ever seen.
StartsWithABang writes: The Standard Model is great at describing all the known particles we’ve ever observed and how they interact, but there are a number of important hints that it isn’t all there is in the Universe. The existence of dark matter, dark energy, neutrino masses, the matter-antimatter asymmetry, the strong-CP and hierarchy problems all tell us that this collection of quarks, leptons, their antiparticles and the bosons we know are only part of the story. The LHC at CERN is currently producing the highest energy collisions at the largest rate ever seen on Earth, making it the best tool to discover new, never-before-seen particles. In a news release just a few days ago, they announced the discovery of multiple new particles – tetraquarks – that had never been seen before. Here's what that means for the Standard Model and our understanding of physics.