71428017
submission
StartsWithABang writes:
When you think about our world and our place in the Solar System, you very likely think about Earth, spinning on its axis, with the Moon orbiting around it, and with the entire Earth-Moon system orbiting the Sun. In fact, all of it — the Earth spinning on its axis, the Moon revolving around Earth, the Earth revolving around the Sun, and even the Sun spinning on its own axis — spins in the same direction: counterclockwise, as viewed from looking "down" on the Earth's north pole. Is this true for all planets in all solar systems? The answer turns out to be "mostly," but there are some incredibly interesting exceptions.
71419777
submission
StartsWithABang writes:
When the electric potential difference between storm clouds in the upper atmosphere and the solid ground of the Earth becomes greater than the breakdown voltage in air, spontaneous lightning strikes occur, exchanging some 10^20 electrons per bolt. But this same phenomenon occurs, spontaneously, during volcanic eruptions, something that's been well-documented for nearly 2000 years. After decades of investigation, we're finally very close to understanding exactly how this happens.
71357109
submission
StartsWithABang 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!
71320649
submission
StartsWithABang 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.
71289001
submission
StartsWithABang 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!
71259327
submission
StartsWithABang 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.
71219487
submission
StartsWithABang 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.
71145797
submission
StartsWithABang 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.
71114405
submission
StartsWithABang 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.
71087919
submission
StartsWithABang 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.
71054253
submission
StartsWithABang 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!
71049509
submission
StartsWithABang 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.
71013891
submission
StartsWithABang writes:
It's been nearly 43 years since humans walked on the lunar surface, and while we've mapped the full sphere of the Moon in unprecedented detail since, nothing compares to the final views that astronauts on the surface experienced. Go relive the panoramic magic here, including the final one ever taken from the Moon.
70978393
submission
StartsWithABang 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!
70923577
submission
StartsWithABang 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.
