Universe Today Video

We hear that rocks are a certain age, and stars are another age. And the Universe itself is 13.7 billion years old. But how do astronomers figure this out? I know it’s impolite to ask, but, how old are you? And how do you know? And doesn't comparing your drivers license to your beautiful and informative “Year In Space” calendar feel somewhat arbitrary? How do we know old how everything is when what we observe was around long before calendars, or the Earth, or even the stars? Scientists have pondered about the age of things since the beginning of science. When did that rock formation appear? When did that dinosaur die? How long has the Earth been around? When did the Moon form? What about the Universe? How long has that party been going on? Can I drink this beer yet, or will I go blind? How long can Spam remain edible past its expiration date? As with distance, scientists have developed a range of tools to measure the age of stuff in the Universe. From rocks, to stars, to the Universe itself. Just like distance, it works like a ladder, where certain tools work for the youngest objects, and other tools take over for middle aged stuff, and other tools help to date the most ancient. Let’s start with the things you can actually get your hands on, like plants, rocks, dinosaur bones and meteorites. Scientists use a technique known as radiometric dating. The nuclear age taught us how to blow up stuff real good, but it also helped understand how elements transform from one element to another through radioactive decay. For example, there’s a version of carbon, called carbon-14. If you started with a kilo of it, after about 5,730 years, half of it would have turned into carbon-12. And then by 5,730 more years, you’d have about ¼ carbon-14 and ¾ carbon-12. This is known as an element’s half-life. And so, if you measure the ratio of carbon-12 to carbon-14 in a dead tree, for example, you can calculate how long ago it lived. Different elements work for different ages. Carbon-14 works for the last 50,000 years or so, while Uranium-238 has a half-life of 4.5 billion years, and will let you date the most ancient of rocks. But what about the stuff we can’t touch, like stars? When you use a telescope to view a star, you can break up its light into different colors, like a rainbow. This is known as a star’s spectra, and if you look carefully, you can see black lines, or gaps, which correspond to certain elements. Since they can measure the ratios of different elements, astronomers can just look at a star to see how old it is. They can measure the ratio of uranium-238 to lead-206, and know how long that star has been around. How astronomers know the age of the Universe itself is one of my favorites, and we did a whole episode on this. The short answer is, they measure the wavelength of the Cosmic Microwave Background Radiation. Since they know this used to be visible light, and has been stretched out by the expansion of the Universe, they can extrapolate back from its current wavelength to what it was at the beginning of the Universe. This tells them the age is about 13.8 billion years. Radiometric dating was a revolution for science. It finally gave us a dependable method to calculate the age of anything and everything, and finally figure out how long everything has been around. So, fan of our videos. How old are you? Tell us in the comments below. Thanks for watching! Never miss an episode by clicking subscribe.Our Patreon community is the reason these shows happen. We’d like to thank Ryan Finley and the rest of the members who support us in our quest to make great space and astronomy content every week. Our community members get advance access to episodes, extras, contests, and other shenanigans with Jay, myself and the rest of the team. Want to get in on the action? Click here.

Venus really sucks. It's as hot as an oven with a dense, poisonous atmosphere. But how did it get that way? Venus sucks. Seriously, it’s the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you dead in moments. Let’s push Venus into the Sun and be done with that terrible place. Its proximity is lowering our real estate values and who knows what sort of interstellar monstrosities are going to set up shop there, and be constantly knocking on our door to borrow the mower, or a cup or sugar, or sneak into our yard at night and eat all our dolphins. You might argue that Venus is worth saving because it’s located within the Solar System’s habitable zone, that special place where water could exist in a liquid state on the surface. But we’re pretty sure it doesn't have any liquid water. Venus may have been better in the past, clearly it started hanging out with wrong crowd, taking a bad turn down a dark road leading it to its current state of disrepair. Could Venus have been better in the past? And how did it go so wrong? In many ways, Venus is a twin of the Earth. It’s almost the same size and mass as the Earth, and it’s made up of roughly the same elements. And if you stood on the surface of Venus, in the brief moments before you evacuated your bowels and died horribly, you’d notice the gravity feels pretty similar. In the ancient past, the Sun was dimmer and cooler than it is now. Cool enough that Venus was much more similar to Earth with rivers, lakes and oceans. NASA’s Pioneer spacecraft probed beneath the planet’s thick clouds and revealed that there was once liquid water on the surface of Venus. And with liquid water, there could have been life on the surface and in those oceans. Here’s where Venus went wrong. It’s about a third closer to the Sun than Earth, and gets roughly double the solar radiation. The Sun has been slowly heating up over the millions and billions of years. At some point, the planet reached a tipping point, where the water on the surface of Venus completely evaporated into the atmosphere. Water vapor is a powerful greenhouse gas, and this only increased the global temperature, creating a runaway greenhouse effect on Venus. The ultraviolet light from the Sun split apart the water vapor into oxygen and hydrogen. The hydrogen was light enough to escape the atmosphere of Venus into space, while the oxygen recombined with carbon to form the thick carbon dioxide atmosphere we see today. Without that hydrogen, Venus’ water is never coming back. Are you worried about our changing climate doing that here? Don’t panic. The amount of carbon dioxide released into the atmosphere of Venus is incomprehensible. According to the IPCC, the folks studying global warming, human activities have no chance of unleashing runaway global warming. We’ll just have the regular old, really awful global warming. So, it’s okay to panic a bit, but do it in the productive way that results in your driving your car less. The Sun is still slowly heating up. And in a billion years or so, temperatures here will get hot enough to boil the oceans away. And then, Earth and Venus will be twins again and then we can push them both into the Sun. I know, I said the words “climate change”. Feel free to have an argument in the comments below, but play nice and bring science.

Since there are stars and galaxies in all directions, why is space black? Shouldn't there be a star in every direction we look? Imagine you’re in space. Just the floating part, not the peeing into a vacuum hose or eating that funky “ice cream” from foil bags part. If you looked at the Sun, it would be bright and your retinas would crisp up. The rest of the sky would be a soothing black, decorated with tiny little less burny points of light. If you've done your homework, you know that space is huge. It even be infinite, which is much bigger than huge. If it is infinite you can imagine looking out into space in any direction and there being a star. Stars would litter everything. Dumb stars everywhere wrecking the view. It’s stars all the way down, people. So, shouldn't the entire sky be as bright as a star, since there’s a star in every possible minute direction you could ever look in? If you've ever asked yourself this question, you probably won’t be surprised to know you’re not the first. Also, at this point you can tell people you were wondering about it and they’ll never know you just watched it here and then you can sound wicked smart and impress all those dudes. This question was famously asked by the German astronomer Heinrich Wilhelm Olbers who described it in 1823. We now call this Olbers’ Paradox after him. Here let me give you a little coaching, you’ll start your conversation at the party with “So, the other day, I was contemplating Olbers’ Paradox… Oh what’s that? You don't know what it is… oh that’s so sweet!”. The paradox goes like this: if the Universe is infinite, static and has existed forever, then everywhere you look should eventually hit a star. Our experiences tell us this isn't the case. So by proposing this paradox, Olbers knew the Universe couldn't be infinite, static and timeless. It could be a couple of these, but not all three. In the 1920s, debonair man about town, Edwin Hubble discovered that the Universe isn't static. In fact, galaxies are speeding away from us in all directions like we have the cooties. This led to the theory of the Big Bang, that the Universe was once gathered into a single point in time and space, and then, expanded rapidly. Our Universe has proven to not be static or timeless. And so, PARADOX SOLVED! Here’s the short version. We don’t see stars in every direction because many of the stars haven’t been around long enough for their light to get to us. Which I hope tickles your brain in the way it does mine. Not only do we have this incomprehensibly massive size of our Universe, but the scale of time we’re talking about when we do these thought experiments is absolutely boggling. So, PARADOX SOLVED! Well, not exactly. Shortly after the Big Bang, the entire Universe was hot and dense, like the core of a star. A few hundred thousand years after the Big Bang, when the first light was able to leap out into space, everything, in every direction was as bright as the surface of a star. So, in all directions, we should still be seeing the brightness of a star.. and yet we don’t. As the Universe expanded, the wavelengths of that initial visible light were stretched out and out and dragged to the wide end of the electromagnetic spectrum until they became microwaves. This is Cosmic Microwave Background Radiation, and you guessed it, we can detect it in every direction we can look in. So Olbers’ instinct was right. If you look in every direction, you’re seeing a spot as bright as a star, it’s just that the expansion of the Universe stretched out the wavelengths so that the light is invisible to our eyes. But if you could see the Universe with microwave detecting eyes, you’d see this: brightness in every direction. Did you come up with Olbers’ Paradox too? What other paradoxes have puzzled you?

When you see the beautiful pictures from the Hubble Space Telescope, you're looking at a lie. They're specially colored images, done for science. But what does space really look like? Do you love the beautiful pictures from the Hubble Space Telescope? Do you ever wonder what it would look like to fly through space and see places like the Orion Nebula up close? Just imagine hiding the Enterprise in the Mutara Nebula, and getting the jump on Khan? Have you ever wondered… what does this stuff actually look like? Looks like we’re back to wrecking sci-fi Christmas again, as I've got some bad news. Nothing, nothing will ever look as cool as the pictures you see on your computer, or even have the same colors. If you were flying right through the Orion Nebula, it wouldn't look anything like the pictures. In fact, it would kinda suck. When looking out into the night sky with your own eyeballs, you don’t see any beautiful nebulousness. Just the stars and the faint glow of the Milky Way. You might be able to see a few fuzzy bits, hint of nebulae, galaxies and star clusters. We’re back to a familiar problem, which those of you who are considering Venus as a vacation spot know too well. We’re made out of meat, and in this case, it’s certainly not doing us any favors. Imagine building a camera out of meat. Pop into a deli, grab a fistful of cold cuts, a pickled egg, and a light sensor, and make that into a camera. Well, that’s your eyes. With the modern advances in camera technologies, we've learned that apparently meat cameras are not great cameras. The biggest advantage to the inorganic kind is that they can gather light for minutes and even hours, soaking up all the photons streaming from a distant object. They, do however, make terrible sandwiches. For example, the famous Hubble Deep Field photograph, which peered into a seemingly empty part of space, turned up thousands of galaxies. Hubble stared for more than 130 hours to create this image. Our meat cameras refresh themselves every few seconds. Even in the darkest skies, with the most perfectly light-adjusted eyes, if you keep your eyes perfectly still and stare at a spot in space, you can’t gather more than 15-20 seconds of light with your eyes. So we’ll never see these objects because they’re so faint and deliver such a tiny amount of light for every second you stare at them. But sure, what if you got close? What if I stuck my meat camera on a tripod right outside one of these gaseous structures. Here’s the crazy part. Nebulae never get any brighter even as you get closer. In optics, there’s a rule called “the conservation of surface brightness”. As you get closer to a nebula, it also gets bigger in the sky. The increased brightness is spread out over a larger area, and the average brightness remains exactly the same. You could be right beside the Orion Nebula, and it wouldn't look any brighter or majestic than we see it from here on Earth. In other words… it would still suck. But what about the colors? Here’s where astronomers are lying to you in a grand conspiracy of Roswellian proportions. So, watch out for those black helicopters, it’s time for another meeting of the Guide To Space Tinfoil Hat Society. Astronomers generally use black-and-white CCD cameras to make their observations. Then they’ll put filters in front of their cameras to only let through very specific wavelengths of light. Those filters can match the specific colors that make up the visible spectrum: red, blue and green. But usually they’re using filters that reveal scientific information. For example, astronomers want to detect the presence of hydrogen, oxygen and sulfur in a nebula. They’ll use one filter that reveals each one of the elements. And then in a program like Photoshop, they’ll assign red to hydrogen, blue to oxygen and green to sulfur. The resulting image can look beautiful, but the colors have nothing to do with reality. That’s right,

This star is X light-years away, that galaxy is X million light-years away. That beginning the Universe is X billion light-years away. But how do astronomers know? I’m perpetually in a state where I’m talking about objects which are unimaginably far away. It’s pretty much impossible to imagine how huge some our Universe is. Our brains can comprehend the distances around us, sort of, especially when we've got a pile of tools to help. We can measure our height with a tape measure, or the distance along the ground using an odometer. We can get a feel for how far away 100 kilometers is because we can drive it in a pretty short period of time. But space is really big, and for most of us, our brains can’t comprehend the full awesomeness of the cosmos, let alone measure it. So how do astronomers figure out how far away everything is? How do they know how far away planets, stars, galaxies, and even the edge of the observable Universe is? Assuming it’s all trickery? You’re bang on. Astronomers have a bag of remarkably clever tricks and techniques to measure distance in the Universe. For them, different distances require a different methodologies. Up close, they use trigonometry, using differences in angles to puzzle out distances. They also use a variety of standard candles, those are bright objects that generate a consistent amount of light, so you can tell how far away they are. At the furthest distances, astronomers use expansion of space itself to detect distances. Fortunately, each of these methods overlap. So you can use trigonometry to test out the closest standard candles. And you can use the most distant standard candles to verify the biggest tools. Around our Solar System, and in our neighborhood of the galaxy, astronomers use trigonometry to discover the distance to objects. They measure the location of a star in the sky at one point of the year, and then measure again 6 months later when the Earth is on the opposite side of the Solar System. The star will have moved a tiny amount in the sky, known as parallax. Because we know the distance from one side of the Earth’s orbit to the other, we can calculate the angles, and compute the distance to the star. I’m sure you can spot the flaw, this method falls apart when the distance is so great that the star doesn't appear to move at all. Fortunately, astronomers shift to a different method, observing a standard candle known as a Cepheid variable. These Cepheids are special stars that dim and brighten in a known pattern. If you can measure how quickly a Cepheid pulses, you can calculate its true luminosity, and therefore its distance. Cepheids let you measure distances to nearby galaxies. Out beyond a few dozen megaparsecs, you need another tool: supernovae. In a very special type of binary star system, one star dies and becomes a white dwarf, while the other star lives on. The white dwarf begins to feed material off the partner star until it hits exactly 1.4 times the mass of the Sun. At this point, it detonates as a Type 1A supernova, generating an explosion that can be seen halfway across the Universe. Because these stars always explode with exactly the same amount of material, we can detect how far away they are, and therefore their absolute brightness. At the greatest scales, astronomers use the Hubble Constant. This is the discovery by Edwin Hubble that the Universe is expanding in all directions. The further you look, the faster galaxies are speeding away from us. By measuring the redshift of light from a galaxy, you can tell how fast it’s moving away from us, and thus its approximate distance. At the very end of this scale is the Cosmic Microwave Background Radiation, the edge of the observable Universe, and the limit of how far we can see. Astronomers are always looking for new types of standard candles, and have discovered all kinds of clever ways to measure distance. They measure the clustering of galaxies,

We've talked about the biggest stars, but what about the smallest stars? What's the smallest star you can see with your own eyes, and how small can they get? Space and astronomy is always flaunting its size issues. Biggest star, hugest nebula, prettiest most talented massive galaxy, most infinite universe, and which comet came out on top in the bikini category. Blah blah blah. In an effort to balance the scales a little we’re going look at the other end of the spectrum. Today we’re talking small stars. First, I’m going to get the Gary Coleman and Emmanuel Lewis joke out of the way, so we can start talking about adorable little teeny tiny fusion factories. We get big stars when we've got many times the mass of the Sun’s worth of hydrogen in one spot. Unsurprisingly, to get smaller stars we’ll need less hydrogen, but there’s a line we can’t cross where there’s so little, that it won’t generate the temperature and pressure at its core to ignite solar fusion. Then it’s a blob, it’s a mess. It’s clean-up in aisle Andromeda. It’s who didn't put the lid back on the jar marked H. So how small can stars get? And what’s the smallest star we know about? In the traditional sense, a star is an object that has enough mass and pressure in its core that it can ignite fusion, crushing atoms of hydrogen into helium. Fusion is exothermic, releasing energy. It’s this energy that counteracts the force of gravity pulling everything inward. That gives you the size of the star and keeps it from collapsing in on itself. By some random coincidence and fluke of nature our Sun is exactly 1 solar mass. Actually, that’s not true at all, our shame is that we use our Sun as the measuring stick for other stars. This might be the root of this size business. We’re in an endless star measuring contest, with whose is the most massive and whose has the largest circumference? So, as it turns out, you can still have fusion reactions within a star if you get all the way down to 7.5% of a solar mass. This is the version you know as a red dwarf. We haven’t had a chance to measure many red dwarf stars, but the nearest star, Proxima Centauri, has about 12.3% the mass of the Sun and measures only 200,000 kilometers across. In other words, the smallest possible red dwarf would only be about 50% larger than Jupiter. There is an important distinction, this red dwarf star would have about EIGHTY times the mass of Jupiter. I know that sounds crazy, but when you pile on more hydrogen, it doesn't make the star that much bigger. It only makes it denser as the gravity pulls the star together more and more. At the time I’m recording this video, this is smallest known star at 9% the mass of the Sun, just a smidge over the smallest theoretical size. Proxima Centauri is about 12% of a solar mass, and the closest star to Earth, after the Sun. But it’s much too dim to be seen without a telescope. In fact, no red dwarfs are visible with the unaided eye. The smallest star you can see is 61 Cygni, a binary pair with one star getting only 66% the size of the Sun. It’s only 11.4 light years away, and you can just barely see it in dark skies. After that it’s Spock’s home, Epsilon Eridani, with 74% the size of the Sun, then Alpha Centauri B with 87%, and then the Sun. So, here’s your new nerd party fact. The Sun is the 4th smallest star you can see with your own eyes. All the other stars you can see are much bigger than the Sun. They’re all gigantic terrifying monsters. And in the end, our Sun is absolutely huge compared to the smallest stars out there. We here like to think of our Sun as perfectly adequate for our needs, it’s ours and all life on Earth is there because of it. It’s exactly the right size for us. So don’t you worry for one second about all those other big stars out there. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

Astronomers are pretty sure what happened after the Big Bang, but what came before? What are the leading theories for the causes of the Big Bang? About 13.8 billion years ago the Universe started with a bang, kicked the doors in, brought fancy cheeses and a bag of ice, spiked the punch bowl and invited the new neighbors over for all-nighter to encompass all all-nighters from that point forward. But what happened before that? What was going on before the Big Bang? Usually, we tell the story of the Universe by starting at the Big Bang and then talking about what happened after. Similarly and completely opposite to how astronomers view the Universe... by standing in the present and looking backwards. From here, the furthest we can look back is to the cosmic microwave background, which is about 380,000 years after the big bang. Before that we couldn't hope to see a thing, the Universe was just too hot and dense to be transparent. Like pea soup. Soup made of delicious face burning high energy everything. In traditional stupid earth-bound no-Tardis life unsatisfactory fashion, we can’t actually observe the origin of the Universe from our place in time and space. Damn you… place in time and space. Fortunately, the thinky types have come up with some ideas, and they’re all one part crazy, one part mind bendy, and 100% bananas. The first idea is that it all began as a kind of quantum fluctuation that inflated to our present universe. Something very, very subtle expanding over time resulting in, as an accidental byproduct, our existence. The alternate idea is that our universe began within a black hole of an older universe. I’m gonna let you think about that one. Just let your brain simmer there. There was universe “here”, that isn't our universe, then that universe became a black hole… and from that black hole formed us and EVERYTHING around us. Literally, everything around us. In every direction we look, and even the stuff we just assume to be out there. Here’s another one. We see particles popping into existence here in our Universe. What if, after an immense amount of time, a whole Universe’s worth of particles all popped into existence at the same time. Seriously… an immense amount of time, with lots and lots of “almost” universes that didn't make the cut. More recently, the BICEP2 team observed what may be evidence of inflation in the early Universe. Like any claim of this gravity, the result is hotly debated. If the idea of inflation is correct, it is possible that our universe is part of a much larger multiverse. And the most popular form would produce a kind of eternal inflation, where universes are springing up all the time. Ours would just happen to be one of them. It is also possible that asking what came before the big bang is much like asking what is north of the North Pole. What looks like a beginning in need of a cause may just be due to our own perspective. We like to think of effects always having a cause, but the Universe might be an exception. The Universe might simply be. Because. You tell us. What was going on before the party started? Let us know in the comments below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

As Einstein showed us, light and matter and just aspects of the same thing. Matter is just frozen light. And light is matter on the move. How does one become the other? Albert Einstein’s most famous equation says that energy and matter are two sides of the same coin. But what does that really mean? And how are equations famous? I like to believe equations can be famous in the way a work of art, or a philosophy can be famous. People can have awareness of the thing, and yet never have interacted with it. They can understand that it is important, and yet not understand why it’s so significant. Which is a little too bad, as this is really a lovely mind bending idea. The origin of E=mc2 lies in special relativity. Light has the same speed no matter what frame of reference you are in. No matter where you are, or how fast you’re going. If you were standing still at the side of the road, and observed a car traveling at ¾ light speed, you would see the light from their headlights traveling away from them at ¼ the speed of light. But the driver of the car would still see that the light moving ahead of them at the speed of light. This is only possible if their time appears to slow down relative to you, and you and the people in the car can no longer agree on how long a second would take to pass. So the light appears to be moving away from them more slowly, but as they experience things more slowly it all evens out. This also affects their apparent mass. If they step on the gas, they will speed up more slowly than you would expect. It’s as if the car has more mass than you expect. So relativity requires that the faster an object moves, the more mass it appears to have. This means that somehow part of the energy of the car’s motion appears to transform into mass. Hence the origin of Einstein’s equation. How does that happen? We don’t really know. We only know that it does. The same effect occurs with quantum particles, and not just with light. A neutron, for example, can decay into a proton, electron and anti-neutrino. The mass of these three particles is less than the mass of a neutron, so they each get some energy as well. So energy and matter are really the same thing. Completely interchangeable. And finally, Although energy and mass are related through special relativity, mass and space are related through general relativity. You can define any mass by a distance known as its Schwarzschild radius, which is the radius of a black hole of that mass. So in a way, energy, matter, space and time are all aspects of the same thing. What do you think? Like E=mc2, what’s the most famous idea you can think of in physics? And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

What fate awaits Phobos, one of the moons of Mars? “All these worlds are yours except Europa, attempt no landing there.” As much as I love Arthur C. Clarke and his books, I've got to disagree with his judgement on which moons we should be avoiding. Europa is awesome. It’s probably got a vast liquid ocean underneath its icy surface. There might even be life swimming down there, ready to be discovered. Giant freaky Europa whales or some kind of alien sharknado. Oh man, I just had the BEST idea for a movie. So yea, Europa’s fine. The place we should really be avoiding is the Martian Moon Phobos. Why? What’s wrong with Phobos? Have I become some kind of Phobo...phobe? Is there any good reason to avoid this place? Well first, its name tells us all we need to know. Phobos is named for the Greek god of Horror, and I don’t mean like the usual gods of horror as in Clive Barker, John Carpenter or Wes Craven, I mean that Phobos is the actual personification of Fear… possibly with a freaky lion’s head. And… there’s also the fact that Phobos is doomed. Literally doomed. Living on borrowed time. Its days are numbered. It’s been poisoned and there’s no antidote. It’s got metal shards in its heart and the battery on it’s electro-magnet is starting to brown out. More specifically, in a few million years, the asteroid-like rock is going to get torn apart by the Martian gravity and then get smashed onto the planet. It all comes down to tidal forces. Our Moon takes about 27 days to complete an orbit, and our planet takes around 24 hours to complete one rotation on its axis. Our Moon is pulling unevenly on the Earth and slowing its rotation down. To compensate, the Moon is slowly drifting away from us. We did a whole episode about this which we’ll link at the end of the episode. On Mars, Phobos only takes 8 hours to complete an orbit around the planet. While the planet takes almost 25 hours to complete one rotation on its axis. So Phobos travels three times around the planet for every Martian day. And this is a problem. It’s actually speeding up Mars’ rotation. And in exchange, it’s getting closer and closer to Mars with every orbit. The current deadpool gives the best odds on Phobos taking 30 to 50 million years to finally crash into the planet. The orbit will get lower and lower until it reaches a level known as the Roche Limit. This is the point where the tidal forces between the near and far sides of the moon are so different that it gets torn apart. Then Mars will have a bunch of teeny moons from the former Phobos. And then good news! Those adorable moonlets will get further pulverized until Mars has a ring. But then bad news… that ring will crash onto the planet in a cascade of destruction to be described as “the least fun balloon drop of all time”. So, you probably wouldn't want to live on Mars then either. Count yourself lucky. What were the chances that we would exist in the Solar System at a time that Phobos was a thing, and not a string of impacts on the surface of Mars. Enjoy Phobos while you can, but remember that real estate there is temporary. Might I suggest somewhere in the alien sharknado infested waters of Europa instead? What do you think. Did Arthur C Clarke have it wrong? Should we explore Europa? And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

A star can burn its hydrogen for millions or even billions of years. But when the party's over, black holes form in an instant. How long does it all take to happen. Uh-oh! You’re right next to a black hole that’s starting to form. In the J.J. Abrams Star Trek Universe, this ended up being a huge inconvenience for Spock as he tried to evade a ticked off lumpy forehead Romulan who’d made plenty of questionable life choices, drunk on Romulan ale and living above a tattoo parlor. So, if you were piloting Spock’s ship towards the singularity, do you have any hope of escaping before it gets to full power? Think quickly now. This not only has implications for science, but most importantly, for the entire Star Trek reboot! Or you know, we can just create a brand new timeline. Everybody’s doing it. Retcon, ftw. Most black holes come to be after a huge star explodes into a supernova. Usually, the force of gravity in a huge star is balanced by its radiation - the engine inside that sends out energy into space. But when the star runs out of fuel to burn, gravity quickly takes over and the star collapses. But how quickly? Ready your warp engines and hope for the best. Here’s the bad news - there’s not much hope for Spock or his ship. A star’s collapse happens in an instant, and the star’s volume gets smaller and smaller. Your escape velocity - the energy you need to escape the star - will quickly exceed the speed of light. You could argue there’s a moment in time where you could escape. This isn't quite the spot to argue about Vulcan physiology, but I assume their reaction time is close to humans. It would happen faster than you could react, and you’d be boned. But look at the bright side - maybe you’d get to discover a whole new universe. Unless of course Black holes just kill you, and aren't sweet magical portals for you and your space dragon which you can name Spock, in honor of your Vulcan friend who couldn't outrun a black hole. Here we've been talking about what happens if a black hole suddenly appears beside you. The good news is, supernovae can be predicted. Not very precisely, but astronomers can say which stars are nearing the end of their lives. Here’s an example. In the constellation Orion, Betelgeuse the bright star on the right shoulder, is expected to go supernova sometime in the next few hundred thousand years. That’s plenty of time to get out of the way. So: black holes are dangerous for your health, but at least there’s lots of time to move out of the way if one looks threatening. Just don’t go exploring too close! If you were to fall through a black hole, what do you think would happen? Naw, just kidding, we all know you’d die. Why don’t you tell us what your favorite black hole sci fi story is in the comments below! And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

One of the biggest mysteries in the Universe is the fact there there's matter, and not antimatter. Where did it all go? When we look around, everything we can see is made of matter. For every type of matter from electrons, protons and quarks there is a similar type of matter known as antimatter. So why aren't there piles of antimatter rocks, cars and chocolate bars just lying around? Why does Scotty always have a little extra kicking around in his liquor cabinet? And where do I get mine? The primary difference between matter and antimatter is that they have opposite electric charge. Which seems pretty mundane. The negatively charged electron has an antiparticle known as the positron, which has a positive electric charge. Anti-protons have a negative charge, and are just flat out grumpy. We’ve been able to create these particles in the lab, and have even been able to create small amounts of anti-hydrogen consisting of a positron bound to an antiproton, when examined closely there’s were shown to have a goatee and a little colorful sash or dagger. When we create particles in accelerators such as the Large Hadron Collider, we seem to get equal amounts of matter and antimatter. This suggests that when particles were formed soon after the big bang, there should have been equal amounts of matter and antimatter. But the universe we observe is only made of matter, and… here’s the best part… we have no idea why. Why didn't the matter and antimatter completely annihilate each other? How come we ended up with a little more matter? This delightful mystery is known as baryon asymmetry. We do have a few ideas, and by we, I mean some giant brained crackerjacks have come up with a few plausible options. The most popular is that somehow antimatter behaves a little differently than matter. This could cause an imbalance between matter and antimatter. After particles collided in the early universe, there would still be matter left over, hence the matter we observe. Another idea is that the observable universe just happens to be in a region dominated by matter. Other parts of the multiverse could have observable universes dominated by antimatter. Baryon asymmetry is one of the big mysteries of modern cosmology. There is an even crazier idea. Antimatter might have anti-gravity. In other words, an atom of anti-hydrogen would fall up instead of down. If that is the case, then matter and antimatter would repel each other, and you might have matter universes and antimatter universes that are forever separate.There have been some initial experiments to test this idea, but so far there have been no conclusive results. What do you think? Where’s all our antimatter and how do we track it down? I’d sure love to bring some home and show my friends... And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

We've all heard that the Universe is expanding, but why is it expanding? What's the force pushing everything outwards? If still you don’t know that we live in an expanding Universe, then I’m clearly not doing my job. And so once more, with feeling... the Universe is expanding. But that certainly doesn't answer all the questions that go along with the it. Like what’s the Universe expanding into? Which we did in another video, which I’ll list at the end of this episode. You might also want to know why is the Universe expanding? What’s making this happen? Did it give up its gym membership? Did it sign up for the gallon of ice cream of the month club? Has it completely embraced the blerch? Edwin Hubble, the astronomer made famous by being named after a space telescope, provided the definitive evidence that the Universe was expanding. Observing distant galaxies, he observed they were fleeing outwards, in fact he was able to come up with calculations to show just how fast they were moving away from us. Or to be more precise, he was able to show how fast all the galaxies are moving away from each other. Which was your question! Just like a minute ago! See you’re just as smart as Hubble! So up until about 15 years ago, the only answer was momentum. The idea was that the Universe received all the energy it needed for its expansion in the first few moments after the Big Bang. Imagine the beginning of the Universe, BOOM, like an explosion from a gun. And all the rest of the expansion is the Universe coasting outwards. For the longest time, astronomers were trying to figure out what this momentum would mean for the future of the Universe. Would the mutual gravity of all the objects in the Universe cause it to slow to a halt at some point in the distant future, or maybe even collapse in on itself, leading to a Big Crunch? Or just clump up in piles and stay on the couch all summer because it’s maybe a little lazy and isn't ready to start going back to the gym yet? In 1999, astronomers discovered something completely unexpected... dark energy. As they were doing their observations to figure out exactly how the Universe would coast to a stop, they discovered that it’s actually speeding up. It’s as if that bullet is actually a rocket and it’s accelerating. Now it appears that the Universe will not only expand forever, but the speed of its expansion will continue to accelerate faster and faster. So what’s causing this expansion? Currently, we believe it’s mostly momentum left over from the Big Bang, and the force of dark energy will be accelerating this expansion. Forever. How do you feel about a rapidly accelerating expanding Universe? Tell us in the comments below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

The Sun has so much more mass than the Earth. So, so, so much more mass. Almost everything in the Solar System is orbiting the Sun, and yet, the Moon refuses to leave our side. What gives? The Sun contains 99.8% of the entire mass of the Solar System. It looks to us like everything seems to orbit the Sun, so why doesn't the Sun capture the Moon from Earth like a schoolyard bully snatching the Earth’s lunch money. That would make sense right? It all fits in with our skewed view of social hierarchy based on an entities volume. Good news! It’s already happened, In a way. The Sun has already captured the Moon. If you look at the orbit of the Moon, it orbits the Sun similar to the way Earth does. Normally the motion of the Moon around the Sun is drawn as a kind of Spirograph pattern, but its actual motion is basically the same orbit as Earth with a small wobble to it. The Moon also orbits the Earth. You might think this is because the Earth is much closer to the Moon than the Sun. After all, the strength of gravity depends not only on the mass of an object, but also on its distance from you. But this isn't the case. The Sun is about 400 times more distant from the Moon than the Earth, but the Sun is about 330,000 times more massive. If you’re up for some napkin calculations, you little mathlete, by using Newton’s law of gravity, you find that even with its greater distance, the Sun pulls on the Moon about twice as hard as the Earth does. So why can’t the Moon escape the Earth? In order to escape the gravitational pull of a body, you need to be moving fast enough *relative to that body* to escape its pull. This is known as the escape velocity of the object. So, yes, the Sun is totally trying to rip the Moon away from the Earth, but the Earth is super clingy. The speed of the Moon around the Earth is about 1 km/s. At the Moon’s distance from the Earth, the escape velocity is about 1.2 km/s. The Moon simply isn't moving fast enough to escape the Earth. Man, those numbers sure are close. I wonder if we could kickstart a rocket to stick on the side? So, even though the Moon can’t escape the Earth, it is gradually moving away. This is due to the tidal interactions between the Earth and Moon, which we talk about another video we’ll link at the end of this one. So even though the Moon will never escape the Earth, it will continue to move away. So, what do you think? What kind of devious project should we start to get the Moon that little boost so it finally escapes the clingy Earth and all its clingy Klingon clingyness? Tell us in the comments below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

Shortly after the Big Bang, the Universe had cooled to the point that the first stars could form out of the primordial hydrogen. How long did it take, and what did these first stars like? Hydrogen soup. Doesn't that sound delicious? Perhaps not for humans, but certainly for the first stars! Early in the Universe, in a spectacular show of stellar soupification, clouds of hydrogen atoms gathered together. They combined with one another. The collected mass got bigger and bigger, and after a time, ignition. The first stars were alive! Well, alive in the sense that they were burning - not that they had feelings or knew what was going on, or had opinions, or were beginning to write would what would eventually become the first Onion article or anything. But where did all that gas come from, and can we spot the evidence of those long-ago stars today? As you know, the Big Bang got our Universe off to a speedy start of expansion. It then took 400,000 years for us to see any light at all. Protons and electrons and other small particles were floating around, but it was far too hot for them to interact. Once the power of the Big Bang finally faded, those protons and electrons paired up and created hydrogen. This is called, rather uninventively, “recombination”. I’d rather just call it hydrogen soup. We’ve got energy. But what is the secret ingredient that sparked these stars? It was just that soup clumping together over time. We can’t say to the minute when the first stars formed, but we have a pretty good idea. The Wilkinson Microwave Anisotropy Probe, aka WMAP examined what happened when these clouds of hydrogen molecules got together, creating tiny temperature differences of only a millionth of a degree. Over time, gravity began to yank matter from spots of lower density into the higher-density regions, making the clumps even bigger. Fantastically bigger. So big that about 200 million years after the clumps were formed, it was possible for these hydrogen molecules to ram into each other at very high speeds. This process is called nuclear fusion. On Earth, it’s a way to produce energy. Same goes for a star. With enough nuclear reactions happening, the cloud of gas compresses and creates a glow. And these stars weren't tiny - they were monsters! NASA says the first stars were 30 to 300 times as massive as the sun, shining millions of times brighter. But this flashy behavior came at a price, because in only a few million years, the stars grew unstable and exploded into supernovae. These stars weren't only exploding. They were also altering the soup around them. They were big emitters of ultraviolet light. It’s a very energetic wavelength, best known for causing skin cancer. So, this UV light struck the hydrogen surrounding the stars. This split the atoms apart into electrons and protons again, leaving quite the mess in space. But it’s through this process that we can learn more about these earliest stars.The stars are long gone, but like a criminal fleeing the scene, they left a pile of evidence behind for their existence. Splitting these atoms was their evidence. This re-ionization is one key piece of understanding how these stars came to be. So it was an action-packed time for the universe, with the Big Bang, then the emergence of soup and then the first stars. It’s quite an exciting start for our galactic history. What do you think the first stars looked like? And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

Rockets are the perfect way to get around in space. But how do they work? Space travel and rockets, it’s like ice cream and apple pie, or ice cream and apple pie and my face. They just go together. They belong together. But what if I’m allergic to rockets, or have some kind of cylindrical intolerance, or flaming column sensitivity that makes me hive out? Why can’t I fly to space in balloons or airplanes or helicopters? Why do we need these pointy cubist eggplant flame tubes? The space age followed the development of powerful V2 rockets in WW II. They could hit targets 320 km away and reach an altitude of 200 km. They were a new kind of war machine, a terrifying weapon that could hurl payloads of destruction from the skies. But this terrifying development is what brought us our modern rockets as their propulsion system can work up where there’s no air, in the vacuum of space. How do they actually work? It all comes down to that “every action, equal and opposite reaction” thing that Newton was always going on about. If you take a balloon, fill it with air, and then let it go. All that air rushing out propels the balloon around. This kind of balloon rocket would work perfectly well in space too although it might be a little too fragile and unpredictable to want to strap yourself to. If we take that idea and scale it up, add some fuel tanks and fins, attitude control and optionally: astronauts. We’ve got ourselves a rocket. It works by pushing “stuff” out one end of a tube at the highest possible velocity. The faster you can blow stuff out the end, the faster the tube itself is going to go. This means rocket science is really all about how to get the exhaust gases hurling out the backside of the rocket as quickly and forcefully as possible. The fuel can be solid, like the space shuttle’s solid rocket boosters. Or the fuel can be liquid, like the shuttle’s main fuel tank filled with liquid oxygen and hydrogen. This fuel is ignited and completely converted into exhaust gases which blast out of the rocket’s nozzles at high velocity. Really, really high velocity. The scary part for passengers is that modern rockets are mostly made of fuel. In fact, the weight of the space shuttle’s fuel was 20 times more than the weight of the shuttle itself. Which I believe really puts a fine point on the bravery of any astronaut. Think of a rocket as a beer can, filled with explosives, that you strap yourself to the outside of. To make a rocket go faster and shorten the travel time, you want to kick material out at a higher velocity. NASA has experimented with ion drives for some of its missions. These highly efficient engines use electric fields to accelerate particles of xenon at much higher velocities. Even though they use a fraction of the amount of fuel, ion engines can reach much higher speeds because of the high exhaust velocity. And even higher velocity rockets have been tabled, such as the VASIMIR engine and even antimatter engines. So how do rockets work? Just like deflating balloons, only bigger. Much much bigger. And full of explosives and modeled on a horrible and terrifying weapon from the second world war. Really, not much like a balloon at all... Have you ever made a rocket? What’s your favorite rocketry experiment. Tell us in the comments below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!