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Submission + - Where our Moon came from

Submitted by StartsWithABang
StartsWithABang writes: Almost every planet has bodies orbiting it, but their moons are far and away much, much smaller and less massive than the planet in question. Not so for Earth! For practically all of human history, the largest, nearest object in the skies—the Moon—was a total mystery, and why we had one that was so large and massive compared to our planet. This was even a mystery when we walked on the Moon! Yet now we know it was formed from an impact with another large world in the early Solar System, and we even have pieces of evidence that validate this unique origin for the Moon.

Submission + - Why don't planets have the same elements as stars?

Submitted by StartsWithABang
StartsWithABang writes: The stars are the heaviest bound objects in the Universe, yet they're made out of the lightest elements: hydrogen and helium. On the other hand, the light, rocky planets are made out of the heaviest elements, with practically no hydrogen or helium at all. Why is this? There's an incredible story of mass, velocity, temperature and gravitation that brings it all together, and explains not only when but how thick a hydrogen/helium envelope a planet can have.

Submission + - How do you figure out your latitude and longitude?

Submitted by StartsWithABang
StartsWithABang writes: If you awoke at any location on Earth, with no idea where you were or when it was, how would you figure out your latitude and longitude? (No GPS.) It's something you can do with only primitive tools, and it turns out that latitude is very easy if you know the night sky well. But longitude? That's a complicated one, but it turns out we can figure it out if we're clever. Here's the story of how.

Submission + - Dark matter in galaxies: proven!

Submitted by StartsWithABang
StartsWithABang writes: If you look at the stars in a galaxy — and then at all the different wavelengths of light that there are — you’d think you can do a good job of reconstructing its mass, and where it’s located. Makes sense, right? Only then, if you take those observations and compare them to how the stars within the galaxy actually move, you’d be shocked to find that what you see isn’t what you get! You might think to invoke dark matter, or you might seek to change the laws of gravity, but there’s a brilliant observational test we can make to tell the two scenarios apart. And for the first time, on the scales of an individual galaxy, we’ve seen the dark matter explanation emerge as the only one that makes sense.

Submission + - When Einstein met H.G. Wells

Submitted by StartsWithABang
StartsWithABang writes: When we talk about dimensions, we’re used to thinking of three: something like length, width and depth, or x, y and z. But there’s a fourth dimension as well that’s of paramount importance for our Universe, otherwise everything would simply be static: time. H.G. Wells brought this idea to life in his story The Time Machine in 1895, and years later Einstein brought forth special and general relativity into the world, bringing scientific validity to this theoretical conception. Here's the fascinating background, story and aftermath of when they met in 1929.

Submission + - Everything about the cosmic and quantum concepts of "nothing"

Submitted by StartsWithABang
StartsWithABang writes: When we conventionally think about nothing, we imagine removing all the forms of matter and energy from space, and having it be completely empty. If only! Quantum mechanics tells us that even empty space isn't so empty, and that not only is it full of virtual particles, but that the zero-point energy of empty space isn't quite zero. Why is this, and what are the limits of our knowledge about what "nothing" truly is? Sabine Hossenfelder has an exploration of all of this that's worth a read.

Submission + - Where does our galaxy's gravity come from?

Submitted by StartsWithABang
StartsWithABang writes: By now, you’ve probably had a lot of opportunities to think about what holds our Universe together: the incredible force of gravitation. Although it’s the weakest known force in the Universe, there seems to be no limit to how much mass you can collect in one place. And so on the largest scales — like solar systems, stars and galaxies — it seems to be the only force that matters. Yet the matter that we see and know of can simply not account for the gravitational force that we see, from its effects on the galaxy to the formation of rocky planets with heavy elements like our own. What’s going on, then? The overwhelming majority of our galaxy's gravity must be coming from a type of dark matter that isn't made of any of the particles we know of.

Submission + - There is no center of the Universe

Submitted by StartsWithABang
StartsWithABang writes: From our vantage point, the Universe is expanding and cooling, with all but a few of the closest galaxies receding from our view. In fact, the farther away an object is, the faster it appears to recede. This may sound an awful lot like what occurs in an explosion to you, especially if it were centered on us. Furthermore, the name “the Big Bang” sure gives that same implication, doesn’t it? Yet despite these facts, it turns out that the idea that the Universe has a center is completely false, and is actually contradicted by both relativity and the Universe that we observe.

Submission + - Why scientific theories can never be proven

Submitted by StartsWithABang
StartsWithABang writes: As any scientist knows, it's true that no scientific theory, no matter how well-tested, how validated, or how universally applicable it is, can ever be 100% proven. But is this a flaw, or is it a feature of science? As it turns out, being able to revise, refine, and learn as we move forward leads to something even better than scientific "proof." It leads to an increasingly accurate picture of all the natural phenomena in the entire Universe.

Submission + - The status of the Universe: 2015

Submitted by StartsWithABang
StartsWithABang writes: In the past 100 years, we've come to understand that our Universe is a vast, expanding-and-cooling space that formed planets, stars, galaxies and clusters from a past that was so hot and dense we didn't even have atoms, nuclei, or stable protons! There are a myriad of questions that have puzzled philosophers and scientists alike for millennia:
  • How old is the Universe?
  • How big is the part of the Universe we can see?
  • What is the shape of the Universe’s space?
  • What makes it up, and in what amounts?
  • What is the Universe’s fate?
  • And where did the Universe come from?

We now know the answers to all of these; here is the full rundown of what we know about all there is at the start of 2015!

Submission + - How many habitable planets are in our galaxy?

Submitted by StartsWithABang
StartsWithABang writes: For the past three years, Kepler has been looking at 150,000 stars, searching for planetary transits. The science haul has been huge, but mostly larger planets close in to their parent stars. Nevertheless, a few rocky, habitable-zone planets have been discovered. Whether we take optimistic or pessimistic estimates, what do we expect for the rest of the galaxy? At minimum, some 6 billion habitable-zone, rocky planets. And likely many more!

Submission + - Mystery of why galaxies always appear dustier on one side solved

Submitted by StartsWithABang
StartsWithABang writes: If you look at a spiral galaxy face-on, the sweeping spiral arms and the central massive bulge are usually the most prominent features. But if you look at one tilted at an angle to us, dust lanes appear prominently. You might expect that the dust lanes should appear equally on both sides of the galaxy, but they don't. Even more puzzlingly, the dust actually does live in the middle of the disk, so you might think there's no excuse for this! We had a theory as to why this works for a while, but recent Hubble observations have confirmed this picture, and we've finally got our answer!

Submission + - The most amazing Hubble image ever

Submitted by StartsWithABang
StartsWithABang writes: Twenty years ago, the Hubble Space Telescope imaged the Eagle Nebula, and uncovered the highest-resolution views of the pillars of creation ever taken. That was back in 1995, and now Hubble is outfitted with a new camera, superior imaging technology, and can span more wavelengths than ever before. The result — double the resolution, larger field-of-view, and better science — is worth your time in full-screen.

Submission + - Should we be content with our paltry space program?

Submitted by StartsWithABang
StartsWithABang writes: At its peak — the mid-1960s — the US government spent somewhere around 20% of its non-military discretionary spending on NASA and space science/exploration. Today? That number is down to 3%, the lowest it’s ever been. In an enraging talk at the annual American Astronomical Society meeting, John M. Logsdon argued that astronomers, astrophysicists and space scientists should be happy, as a community, that we still get as much funding as we do. Professional scientists do not — and should not — take this lying down.

Submission + - Where do the atoms that make us up come from?

Submitted by StartsWithABang
StartsWithABang writes: From the perspective of a human being, when we ask about where "all this" comes from, there's little that's more important to us than the existence of atoms. Yet when the Universe first cooled off following the Big Bang, the Universe was some 99.9999999% hydrogen and helium, with no trace at all of carbon, nitrogen, oxygen or the other heavy elements necessary for life. So where did the heavy elements come from? Theoretical astrophysicist Ethan Siegel has the full story in less than 5 minutes!

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