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We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).

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+ - Pulling someone out of a black hole is impossible

Submitted by StartsWithABang
StartsWithABang (3485481) writes "If you move at the speed of light and are inside the event horizon of a black hole, you inevitably fall towards the singularity at the center. But if you were completely outside of the event horizon, you can escape. So what if you were completely outside of a large, massive black hole (with small spatial curvature at the event horizon) and then dipped just a small amount of matter inside. Could you just pull it out again? It turns out the answer is no, and that — to date — there's still no way to escape from a black hole!"

+ - Overcoming the Fingers (and Pancakes) of God

Submitted by StartsWithABang
StartsWithABang (3485481) writes "We’re all familiar with Hubble’s law, or the notion that the Universe is expanding, and that the farther away you look, the faster you’ll see that distant galaxy moving away from you. This relation would be exact, if only the rest of the objects in the Universe didn’t exert gravitational forces on one another. They do, however, leading to distortions that aren’t really there when we try and reconstruct maps of the Universe, known as “fingers” and “pancakes” of God. Thanks to some amazing physics, however, we can understand and remove these artifacts, allowing us to map the Universe on the largest scales to unprecedented accuracy."

+ - Why a French Abbey becomes an island every 18 years.

Submitted by StartsWithABang
StartsWithABang (3485481) writes "Once every 18 years, a French Abbey — Mount St.-Michel — becomes inaccessible, as the English Channel rises to such levels that the causeway that normally reaches it becomes engulfed by the surrounding waters. You might think this is due to the tides, where the Earth, Moon and Sun align, but then shouldn’t this happen twice a month, during the two Spring Tides? As it turns out, the effects are much more subtle, and involve the Moon’s elliptical orbit and the equinoxes as well, but when they all align, once every 18 years, a supertide is the result, and Mount St.-Michel becomes an island!"

+ - No, the LHC will still not make an Earth-destroying black hole

Submitted by StartsWithABang
StartsWithABang (3485481) writes "Every time we go to higher-and-higher energies with our particle accelerators, we increase the chances of finding new particles, new knowledge, and new fundamental physics. While there are also potential risks, the most commonly trotted-out one is that the LHC — set to run at 13 TeV, up from 7 TeV previously — will create an Earth-destroying black hole that will devour the planet in short order. Here's the physics of why that's impossible."

+ - The first billion-pixel mosaic of Mars

Submitted by StartsWithABang
StartsWithABang (3485481) writes "In 2012, Mars Science Laboratory performed the first robotically-controlled soft landing of a vehicle of such incredible mass: nearly half a tonne. A few months later, the rover, Curiosity, took the first ever billion-pixel mosaic from the Red Planet's surface, with breathtaking views of the terrain and alternate views of what the soils would look like were they here on Earth. Now in its third year on Mars, Curiosity is roving the low slopes of its ultimate destination: Mount Sharp."

+ - Space CAN expand faster than the speed of light

Submitted by StartsWithABang
StartsWithABang (3485481) writes "You know the fundamental principle of special relativity: nothing can move faster than the speed of light. But space itself? That's not a "thing" in the conventional sense. Two years after coming up with special relativity, Einstein devised the equivalence principle, and thus began the development of general relativity, where space itself would have properties that changed over time, responding to changes in matter and energy. This includes the ability for it to expand, even faster than the speed of light, if the conditions are right."

+ - The stolen credit for what makes up the Sun

Submitted by StartsWithABang
StartsWithABang (3485481) writes "Sure, it's easy today to look at the Sun and know it's a ball of (mostly) hydrogen, generating energy by combining those protons in a chain into helium through the process of nuclear fusion. But before we even knew that nuclear fusion was possible, we needed to figure out what the Sun was made out of, a more difficult task than you'd imagine. The credit was given to Henry Norris Russell (of Hertzsprung-Russell diagram fame), but he completely stole the work from a woman you never heard of, his student, Cecilia Payne, after discouraging her from publishing her work on the subject four years prior."

+ - The first stars in the Universe were invisible

Submitted by StartsWithABang
StartsWithABang (3485481) writes "You'd think it would be enough to form some stars, and "let there be light" would be a reality. But these stars don't become visible for literally hundreds of millions of years until after they form. It's not that they don't emit light — they do — but rather that the Universe is opaque to that light for up to half a billion years after those stars form. While modern telescopes like Hubble are inherently limited by this fact, the James Webb Space Telescope, which will observe in wavelengths that these dusty particles ought to be transparent to, might be able to finally probe the true light from the very first stars."

+ - The skies celebrate St. Patrick's Day with a spectacular aurora

Submitted by StartsWithABang
StartsWithABang (3485481) writes "Everyone's a little bit Irish on St. Patrick's Day, but it's a very rare St. Patrick's Day indeed when the skies themselves turn green! But the Universe is aligning for us tonight, as the particles from a class-C solar flare slam into Earth's auroral oval, creating a spectacular green show visible much closer to the equator than anyone has a right to expect. Check out the Earth's natural, physical celebration of St. Patrick's Day tonight!"

+ - Einstein's happiest thought was really macabre

Submitted by StartsWithABang
StartsWithABang (3485481) writes "Sure, Einstein came up with both special and general relativity, revolutionizing our understanding of how the Universe works. But how did he come up with his new theory of gravity? Oddly enough, by imagining someone plummeting towards their doom. By comparing a freely-falling observer with one accelerating under a non-gravitational force, Einstein unearthed the equivalence principle, and eight years later, General Relativity came spilling out. The Universe has never been the same."

+ - Is a chunk of neutron-star matter stable?

Submitted by StartsWithABang
StartsWithABang (3485481) writes "At a density more than 10^22 times that of water, neutron stars are the densest form of matter found in the Universe. Compressing somewhere around the mass of the Sun into a sphere just a few kilometers in radius, the incredible gravitational binding energy keeps these neutrons from decaying. If you took a small chunk of this matter out, it would still be tremendously powerful: the amount you could hold in your hand would have a greater mass than the Moon! But would it be stable? And if not, what would happen, and how much would you need to have to reach stability? Love the catastrophic answers, and the conclusions that neutron-star-matter is most definitely not what Thor's hammer is made of!"

+ - Proxima Centauri might not be the closest star to Earth

Submitted by StartsWithABang
StartsWithABang (3485481) writes "The Alpha Centauri system consists of three stars, including Proxima Centauri, the closest star to Earth. But while main-sequence, hydrogen-burning stars are easy to find due to their visible light output, brown dwarfs — which only fuse the small amounts of deuterium they're born with — often emit no visible light at all, and can only be seen in the infrared. In 2013, WISE discovered a binary pair of brown dwarfs just 6.5 light years away, making them the third-closest star system to Earth, and leaving open the possibility that there may yet be brown dwarfs closer to us than any star, a question that it will take the James Webb Space Telescope to answer."

+ - How the solar neutrino problem was solved 1

Submitted by StartsWithABang
StartsWithABang (3485481) writes "For nearly all of human history — well into the 20th century — we really didn’t know how the Sun worked. Could it have been combustion, like we see on Earth? Or perhaps gravitational contraction, like that which powers white dwarf stars? No, it turned out to be nuclear fusion. Yet when we built our best models and went to test what we expected to see with what we actually observed, it was the smallest particles that didn’t add up: the neutrino. For decades, we kept observing only a third the number we expected. Here’s the story of how we solved that mystery, only in the early 2000s, and finally figured out what goes on inside the Sun!"

+ - Photonic booms: how optical phenomena move faster than light 1

Submitted by StartsWithABang
StartsWithABang (3485481) writes "Imagine the surface of the Moon, some 360,000 km distant, and an infinitely precise and powerful laser pointer. With a flick of your wrist, you can send the dot that you see flying across the Moon’s surface as quickly as you can manage. Without too much difficulty, in fact, you’ll find yourself breaking the speed of light! Not in terms of violating special relativity or anything, but if you follow the motion of the dot, you’ll not only find that it appears to move faster than the speed of light in a vacuum, c, but that its behavior is more interesting — and more counterintuitive — than you’d ever imagined."

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