66279103
submission
StartsWithABang 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.
66244853
submission
StartsWithABang 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!
66211867
submission
StartsWithABang 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.
66161989
submission
StartsWithABang 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!
66153119
submission
StartsWithABang 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.
66121041
submission
StartsWithABang 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.
66040217
submission
StartsWithABang 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.
65953685
submission
StartsWithABang writes:
We like to think of our Solar System as typical: a central star with a number of planets — some gas giants and some rocky worlds — in orbit around it. Yes, there's some variety, with binary or trinary star systems and huge variance in the masses of the central star being common ones, but from a planetary point of view, our Solar System is a rarity. Even though there are hundreds of billions of stars in our galaxy for planets to orbit, there are most likely around a quadrillion planets in our galaxy, total, with only a few trillion of them orbiting stars at most. Now that we've finally detected the first of these, we have an excellent idea that this picture is the correct one: most planets in the Universe are homeless. Now, thank your lucky star!
65922047
submission
StartsWithABang writes:
No, we haven't found it yet. But there are good reasons that we probably never will, and that even if we did find it, we probably wouldn't be able to recognize it as such. Come learn the nuances of what we think it should look like, what our prospects for hunting them are, and what the closest is that we've come so far!
65870545
submission
StartsWithABang writes:
Wandering into the woods unprepared and without a plan sounds like a terrible idea. But if you’re interested in scientific exploration at the frontiers, confronting the unknown with whatever you happen to have at your disposal, you have to take that risk. You have to be willing to take those steps. And you have to be okay with putting your best ideas out there — for all to see — knowing full well that you might get the entire thing wrong. Sometimes, that’s indeed what happens. Some of the most revered and famous scientific minds in history confronted the great mysteries of nature, and came away having done nothing but set us back many years by leading the field down a blind alley. But other times, the greatest leaps forward in our understanding occur as a result. Explore some great examples, and learn why this is vital for scientific progress.
65861329
submission
StartsWithABang writes:
You've no doubt heard of quantum entanglement before: the idea that if you create a mixed quantum state that consists of two particles, you can then know the properties of one by measuring the properties of the other. The odd — and counterintuitive — thing about this is that once these particles are entangled, you can move them an arbitrary distance apart from one another, measure the properties of one, and instantly know about the properties of the other! Does this violate the law of special relativity, which says the speed limit of everything in the Universe? As it turns out, the answer is no, but Einstein nevertheless thought this shouldn't be allowed to happen! Despite being the most brilliant mind of his generation, this is one of those times that Einstein got it completely wrong. Come learn about the ghostly physics that Einstein called "spooky action at a distance."
65792875
submission
StartsWithABang writes:
Every once in a while, a river develops a sandbar island in the middle. Normally, this happens because it carves a small tributary through one of its banks, creating an isolated island. Unfortunately, over time, the rushing water erodes the island in the middle, something that happens very quickly if there isn't a large, complex root system to fight the erosion processes. For those of you who feel that once person can't make a difference, meet the ultimate counterexample: the man who planted an entire forest, saved an island, and defended herds of wildlife from would-be poachers.
65772737
submission
StartsWithABang writes:
It's a phenomenon we've all experienced: you've got a roaring fire going and you're excited to keep it burning for longer, so you throw an extra two or three large logs on it. A half hour later, all you've got left are coals. It might not make intuitive sense, but you would have been better off just putting a single log on — in other words, adding less fuel — if you wanted your fire to last longer. Here's the science of why.
65727029
submission
StartsWithABang writes:
Handing your health and fitness over to a reality show, where the goal is to lose as much of your weight as possible in the shortest amount of time, might not be the healthiest long-term option, but for a chance at a quarter of a million dollars, it's worth it for some. Imagine how frustrated you'd be, though, if you learned that you should have been the winner, but weren't, all because of the rounding errors inherent to the format of the show. They not only often send the wrong person home, but may have crowned the wrong winner as a result of this common math mistake!
65701011
submission
StartsWithABang writes:
It’s such a part of our cosmic and scientific history, that it’s difficult to remember that it’s only been for the past 50 years that the Big Bang has been the leading theory-and-model that describes our Universe. Ever since the 1920s, when Edwin Hubble discovered the apparent expansion of our Universe, we’ve recognized that it’s a much bigger place than simply what’s in the Milky Way. But the Big Bang was hardly the only game in town. Yet the discovery of not only the Cosmic Microwave Background, but the detailed measurement of its temperature and spectrum, was able to rule out every single alternative as a non-viable model.
