If you’ve seen at least one other episode of the Guide to Space, you know I’m obsessed about the Fermi Paradox. This idea that the Universe is big and old, and should be teeming with life. And yet, we have no evidence that it exists out there. We wonder, where are all the aliens?
Ah well, maybe we’re in a cosmic zoo, or maybe the Universe is just too big, or the laws of physics prevent any kind of meaningful travel or communications. Fine. I doubt it, but fine.
The sign of a truly great scientific theory is by the outcomes it predicts when you run experiments or perform observations. And one of the greatest theories ever proposed was the concept of Relativity, described by Albert Einstein in the beginning of the 20th century.
In addition to helping us understand that light is the ultimate speed limit of the Universe, Einstein described gravity itself as a warping of spacetime.
He did more than just provide a bunch of elaborate new explanations for the Universe, he proposed a series of tests that could be done to find out if his theories were correct.
One test, for example, completely explained why Mercury’s orbit didn’t match the predictions made by Newton. Other predictions could be tested with the scientific instruments of the day, like measuring time dilation with fast moving clocks.
Since gravity is actually a distortion of spacetime, Einstein predicted that massive objects moving through spacetime should generate ripples, like waves moving through the ocean.
The more massive the object, the more it distorts spacetime. Credit: LIGO/T. Pyle
Just by walking around, you leave a wake of gravitational waves that compress and expand space around you. However, these waves are incredibly tiny. Only the most energetic events in the entire Universe can produce waves we can detect.
It took over 100 years to finally be proven true, the direct detection of gravitational waves. In February, 2016, physicists with the Laser Interferometer Gravitational Wave Observatory, or LIGO announced the collision of two massive black holes more than a billion light-years away.
Any size of black hole can collide. Plain old stellar mass black holes or supermassive black holes. Same process, just on a completely different scale.
Colliding black holes. Credit: LIGO/A. Simonnet
Let’s start with the stellar mass black holes. These, of course, form when a star with many times the mass of our Sun dies in a supernova. Just like regular stars, these massive stars can be in binary systems.
Imagine a stellar nebula where a pair of binary stars form. But unlike the Sun, each of these are monsters with many times the mass of the Sun, putting out thousands of times as much energy. The two stars will orbit one another for just a few million years, and then one will detonate as a supernova. Now you’ll have a massive star orbiting a black hole. And then the second star explodes, and now you have two black holes orbiting around each other.
As the black holes zip around one another, they radiate gravitational waves which causes their orbit to decay. This is kind of mind-bending, actually. The black holes convert their momentum into gravitational waves.
As their angular momentum decreases, they spiral inward until they actually collide. What should be one of the most energetic explosions in the known Universe is completely dark and silent, because nothing can escape a black hole. No radiation, no light, no particles, no screams, nothing. And if you mash two black holes together, you just get a more massive black hole.
The gravitational waves ripple out from this momentous collision like waves through the ocean, and it’s detectable across more than a billion light-years.
Arial view of LIGO Livingston. Credit: The LIGO Scientific Collaboration
This is exactly what happened earlier this year with the announcement from LIGO. This sensitive instrument detected the gravitational waves generated when two black holes with 30 solar masses collided about 1.3 billion light-years away.
This wasn’t a one-time event either, they detected another collision with two other stellar mass black holes.
Regular stellar mass black holes aren’t the only ones that can collide. Supermassive black holes can collide too.
From what we can tell, there’s a supermassive black hole at the heart of pretty much every galaxy in the Universe. The one in the Milky Way is more than 4.1 million times the mass of the Sun, and the one at the heart of Andromeda is thought to be 110 to 230 million times the mass of the Sun.
In a few billion years, the Milky Way and Andromeda are going to collide, and begin the process of merging together. Unless the Milky Way’s black hole gets kicked off into deep space, the two black holes are going to end up orbiting one another.
Just with the stellar mass black holes, they’re going to radiate away angular momentum in the form of gravitational waves, and spiral closer and closer together. Some point, in the distant future, the two black holes will merge into an even more supermassive black hole.
View of Milkdromeda from Earth “shortly” after the merger, around 3.85-3.9 billion years from now. Credit: NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas, and A. Mellinger
The Milky Way and Andromeda will merge into Milkdromeda, and over the future billions of years, will continue to gather up new galaxies, extract their black holes and mashing them into the collective.
Black holes can absolutely collide. Einstein predicted the gravitational waves this would generate, and now LIGO has observed them for the first time. As better tools are developed, we should learn more and more about these extreme events.
We’ve had an abundance of news stories for the past few months, and not enough time to get to them all. So we are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
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We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page.
So if you’ve been to Yellowstone National Park, you’ve seen one of the most amazing features of the natural world – geysers. In today’s episode, we’re going to talk about geysers on Earth, and where they might be in the solar system.
We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
It’s been a while since I read the NASA manual on space helmet operation, but if I recall correctly, they really just have one major rule. When you go to space, keep your space helmet on.
I don’t care what haunting music those beguiling space sirens are playing. It doesn’t matter if you’ve got a serious case of space madness, and you’re hallucinating that you’re back on your Iowa farm, surrounded by your loved ones. Even if you just turned on an ancient terraforming machine and you’re stumbling around the surface of Mars like an idiot. You keep your helmet on.
Keep. Your. Helmet. On. Credit: NASA
Not convinced? Well then, allow me to explain what happens if you decide to break that rule. Without a helmet, and your own personal Earth-like atmosphere surrounding you, you’ll be exposed to the hard vacuum of space.
Within a moment, all the air will rush out of your lungs, and then you’ll fall unconscious in about 45 seconds. Starved for oxygen, you’ll die of suffocation in just a couple of minutes. Then you’ll freeze solid and float about forever. Just another meat asteroid in the Solar System.
That’s the official stance on space helmet operation, but just between you and me, there might be a little wiggle room. A few other places in the Solar System where you can take your helmet off for just a moment, and maybe not die instantaneously.
Earth is obviously safe. If you’re down here on the planet, and you’re still wearing your helmet, you’re missing the whole point of why you need a helmet in the first place. That space helmet rule only applies to space, silly, you can take it off down here.
In order to survive, the human body needs a few things. First, we need pressure surrounding our body, and helping to keep our lungs inflated. The Earth’s atmosphere provides that service, stacking a huge column of air down on top of you.
Without enough pressure, the air will blast out of your lungs and you’ll suffocate. Too much pressure and your lungs will crush and your heart will give out.
You’re going to want atmospheric pressure somewhere between .5 to 5 times the atmosphere of Earth.
If you can’t find air, then some other gas or even water will do in a pinch. You can’t breathe it, but it can provide the pressure you’re looking for.
Do not take your helmet off on the Moon. Credit: NASA
If you’ve got the pressure right, then your next priority will be the temperature. You know what it’s like to be too cold on Earth, and too hot, so use your judgement here. It’s too cold if you’re starting to die of hypothermia, and too hot if you’re above 60 C for a few minutes.
If you really want to thrive, find air you can breathe. Ideally a nice mixture of nitrogen and oxygen. Again, here on Earth, that column of air pushing down on you also allows you to breathe. If you swapped air for carbon dioxide or water, you’re going to need to hold your breath.
So what are some other places in the Solar System that you could take your helmet off for a few brief moments?
Your best bet is the planet Venus. Not down at the surface, where the temperature is hot enough to melt lead, and it’s 90 atmospheres pressure.
But up in the cloud tops, it’s a whole different story. At 52.5 kilometers altitude, the temperature is about 37 C. A little stifling, but not too bad. And the air pressure is about 65% Earth’s air pressure.
Hold your breath if you’re planning on taking off your helmet within the clouds of Venus. Credit: NASA
The problem is that this region is right in the middle of Venus’ sulphuric acid cloud layer, so you might inhale a mist of toxic acid if you tried to breathe. Not to mention the fact that Venus’ atmosphere is carbon dioxide, which means you’ll asphyxiate if you tried to breathe it.
But assuming you had some kind of air supply to breathe, and a suit to protect you from the sulphuric acid, you could hang around, without a helmet as long as you liked.
Take that! Overly draconian NASA helmet rules.
Out on the surface of Titan? Good news! The surface pressure on Titan is 1.45 times that of Earth. You won’t need a pressure helmet at all, ever. You will need a warming helmet, however, since the temperature on Titan is -179 C. You might be able to take that helmet off for a brief moment, before your face freezes, but don’t take a breath, otherwise you’ll freeze your lungs.
Want another location? No problem. Astronomers are pretty sure there are vast reservoirs of water under the surface of many moons and large objects in the Solar System, from Europa to Charon.
This artist’s concept of Jupiter’s moon Ganymede, the largest moon in the solar system, illustrates the club sandwich model of its interior oceans. You could try taking your helmet off while diving in them. Credit: NASA/JPL
They’re heated up through tidal interactions, and could be dozens of kilometers thick. Drill down through the ice sheet, and then just dive into the icy waters without a helmet. It’ll be really cold, and you won’t be able to breathe, but you can stay alive as long as you can hold your breath.
Did you jump out of your spacecraft and now you’re falling to your death into one of the Solar System’s gas giants? That’s bad news and it won’t end well. However, there’s a tiny silver lining. As you fall through the atmosphere of Jupiter, for example, there’ll be a moment when the temperature and pressure roughly match what your body can handle.
Go ahead and take your helmet off and enjoy that sweet spot before you plunge into the swirling hydrogen gas. Once again, though, don’t breathe. Hold your breath, the moment will last longer before you go unconscious.
And listen, if you really really need to take off your helmet in the cold vacuum of space, you can do it. Make sure you completely exhale so you don’t wreck your lungs. Then you’ve got about 45 seconds before you go unconscious.
That’s enough time to jump across to an open airlock, or kick that nasty xenomorph holding onto your leg into deep space.
Even though the NASA space helmet manual has one rule – keep your helmet on – you can see there are a few times and places where you can bend those rules without instantly dying. Use your judgement.
I’d like to thank Mechadense for posting a comment on an earlier Guide to Space YouTube video, which became the inspiration for this episode. Thanks for doing the math Mechadense and bringing the science.
When SpaceX CEO Elon Musk took to the stage at the International Astronautical Congress in Mexico on Monday, he announced his bold vision to send humanity into the Solar System, he laid out one of the most elaborate and ambitious projects ever put forward in the field of human space exploration.
Like many of you, I watched his announcement slack jawed at the implications.
My first thought? A spaceship capable of carrying 100 humans from Earth to Mars with a reusable main stage? Uh, that’s ambitious.
Scott Manley is one of my favorite YouTubers/Twitch Streamers. In case you’ve never seen him before, Scott is an absolute master of the space game, running instructional videos on EVE Online, Kerbal Space Program and other cosmic simulations.
Entering the atmosphere of Duna with 100 Kerbals on board.
The planets aligned, and Scott was planning to run a livestream game on his Twitch channel Monday night, so I jumped in and provided colour commentary while Scott constructed all aspects of the mission: a spacecraft capable of carrying 100 Kerbals safely to the surface of the Red Planet (Duna), a monster booster rocket to blast the crew compartment into orbit, and a refueling module that travels on a re-purposed booster.
Over the course of 2-hours, Scott built and tested all parts of the Interplanetary Transport Ship in KSP to varying levels of success. Some boosters exploded, Kerbals were left stranded on the surface of Duna (maybe that does match Musk’s plans), and Scott was unable to use the docking claw to mate spacecraft to transfer fuel.
In Scott’s defense, though, he was consuming 10% space beer during the broadcast.
But if I know Scott, he’s working on version 2 right now, and we’ll see a smooth video demonstrating all aspects of the mission shortly.
If you haven’t already, go ahead and subscribe to Scott’s channel, and enjoy the silliness.
P.S. If you’re interested in space games, Pamela and I discuss them in this week’s Astronomy Cast.
Canadians don’t have much to be proud of, but we can regale you with our ability to withstand freezing cold temperatures. Now, I live on the West Coast, so I’m soft and weak, rarely experiencing temperatures below freezing.
But for some of my Canadian brethren, temperatures can dip down to levels your mind and body can scarcely comprehend. For example, I have a friend who lives in Winnipeg, Manitoba. For a day last winter, the temperatures there dipped down -31C, but with the windchill, it felt like -50C. On that same day, it was a balmy -29C on Mars. On Mars!
But for scientists, and the Universe, it can get much much colder. So cold, in fact, that they use a completely different temperature scale – Kelvin – to measure how far away things are from the coldest possible temperature: Absolute Zero.
Nowhere close to absolute zero. Credit: Osccarr (CC BY 2.0)
On the Celsius scale, Absolute Zero is -273.15 degrees. And in Fahrenheit, it’s -459.67 degrees. In the Kelvin scale, however, it’s very simple. Absolute Zero is 0 kelvin.
At this point, a science explainer is going to stumble into a minefield of incorrect usage. It’s not 0 degrees kelvin, you don’t say the degrees part, just the kelvin part. Just kelvin.
This is because when you measure something from an arbitrary point, like the direction you just turned, you’ve changed course 15-degrees. But if you’re measuring from an absolute point, like the lowest physical temperature defined by nature, you drop the degrees because it’s an absolute. An Absolute Zero.
Of course, I’ve probably gotten that wrong too. This stuff is hard.
Anyway, back to Absolute Zero.
Still not cold enough. Credit: Lori Cuthbert (CC BY 2.0)
Absolute Zero is the coldest possible temperature that can theoretically be reached. At this point, no heat energy can be extracted from a system, no work can be done. It’s dead Jim.
But it’s completely theoretical. It’s practically impossible to cool something down to Absolute Zero. In order to cool something down, you need to do work to extract heat from it. The colder you get, the more work you need to do. In order to get to Absolute Zero, you’d need to put in an infinite amount of work. And that’s ridiculous.
As you probably learned in physics or chemistry class, the temperature of a gas translates to the motion of the particles in the gas. As you cool a gas down, by extracting heat from it, the particles slow down.
You would think, then, that by cooling something down to Absolute Zero, all particle motion in that something would stop. But that’s not true.
From a quantum mechanics point of view, you can never know the position and momentum of particles at the same time. If the particles stopped, you’d know their momentum (zero) and their position… right there. The Universe and its laws of physics just can’t allow that to happen. Thank Heisenberg’s Uncertainty Principle.
Therefore, there’s always a little motion, even if you could get to Absolute Zero, which you can’t. But you can’t extract any more heat from it.
The physicist Robert Boyle was one of the first to consider the possibility that there was a lowest possible temperature, which he called the primum frigidum. In 1702, Guillaume Amontons created a thermometer that he calculated would bottom out at -240 C. Pretty close, actually.
But it was Lord Kelvin, who created this absolute scale in 1848, starting at -273 C, or 0 kelvin.
A photograph of Lord Kelvin.
By this measurement, even with its windchill, Winnipeg was a balmy 223 kelvin on that wintry day.
The surface of Pluto, on the other hand varies from a low of 33 kelvin to a high of 55 kelvin. That’s -240 C to -218 C.
The average background temperature across the entire Universe is just 2.7 kelvin. You won’t find many places that cold, unless you get out to the vast cosmic voids that separate galaxy clusters.
Over time, the background temperature of the Universe will continue to drop, but it’ll never actually reach Absolute Zero. Even in a Googol years, when the last supermassive black hole has finally evaporated, and there’s no usable heat left in the entire Universe.
In fact, astronomers call this bleak future the “heat death” of the Universe. It’s heat death, as in, the death of all heat. And happiness.
You might be surprised to know that the coldest temperature in the entire Universe is right here on Earth. Well, sometimes, anyway. And assuming the aliens haven’t got better technology than us, which they probably do.
At the time that I’m recording this video, physicists have used lasers to cool down Rubidium-87 gas to just 170 nanokelvin, a tiny fraction above Absolute Zero. In fact, they won a Nobel Prize for their work in discovering Bose-Einstein condensates.
NASA is actually working on a new experiment called the Cold Atom Lab that will send a version of this technology to the International Space Station, where it should be able to cool material down to 100 picokelvin. That’s cold.
The Cold Atom Lab is planned to launch in August 2017. Credit: NASA / JPL
Here are your takeaways. Absolute Zero is the coldest possible temperature than can ever be reached, the point at which no further heat energy can be extracted from a system. Never say degrees kelvin, you’ll cause so much wincing. The Universe can’t match our cold generating abilities… yet. Take that Universe.
I’d love to hear the coldest temperature you’ve ever personally experienced. For me, it was visiting Buffalo in December. That’s not right.
We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.
Remember the movie Sunshine, where astronomers learn that the Sun is dying? So a plucky team of astronauts take a nuclear bomb to the Sun, and try to jump-start it with a massive explosion. Yeah, there’s so much wrong in that movie that I don’t know where to start. So I just won’t.
Seriously, a nuclear bomb to cure a dying Sun?
Here’s the thing, the Sun is actually dying. It’s just that it’s going to take about another 5 billion years to run of fuel in its core. And when it does, Cillian Murphy won’t be able to restart it with a big nuke.
But the Sun doesn’t have to die so soon. It’s made of the same hydrogen and helium as the much less massive red dwarf stars. And these stars are expected to last for hundreds of billions and even trillions of years.
Is there anything we can do to save the Sun, or jump-start it when it runs out of fuel in the core?
First, let me explain the problem. The Sun is a main sequence star, and it measures 1.4 million kilometers across. Like ogres and onions, the Sun is made of layers.
The interior structure of the Sun. Credit: Wikipedia Commons/kelvinsong
The innermost layer is the core. That’s the region where the temperature and pressure is so great that atoms of hydrogen are mashed together so tightly they can fuse into helium. This fusion reaction is exothermic, which means that it gives off more energy than it consumes.
The excess energy is released as gamma radiation, which then makes its way through the star and out into space. The radiation pushes outward, and counteracts the inward force of gravity pulling it together. This balance creates the Sun we know and love.
Outside the core, temperatures and pressures drop to the point that fusion can no longer happen. This next region is known as the radiative zone. It’s plenty hot, and the photons of gamma radiation generated in the core of the Sun need to bounce randomly from atom to atom, maybe for hundreds of thousands of years to finally escape. But it’s not hot enough for fusion to happen.
Outside the radiative zone is the convective zone. This is where the material in the Sun is finally cool enough that it can move around like a lava lamp. Hot blobs of plasma pick up enormous heat from the radiative zone, float up to the surface of the Sun, release their heat and then sink down again.
The only fuel the Sun can use for fusion is in the core, which accounts for only 0.8% of the Sun’s volume and 34% of its mass. When it uses up that hydrogen in the core, it’ll blow off its outer layers into space and then shrink down into a white dwarf.
The radiative zone acts like a wall, preventing the mixing convective zone from reaching the solar core.
If the Sun was all convective zone, then this wouldn’t be a problem, it would be able to go on mixing its fuel, using up all its hydrogen instead of this smaller fraction. If the Sun was more like a red dwarf, it could last much longer.
Red dwarf stars burn for much longer than our Sun. Credit: NASA, ESA, and D. Aguilar (Harvard-Smithsonian Center for Astrophysics)
In order to save the Sun, to help it last longer than the 5 billion years it has remaining, we would need some way to stir up the Sun with a gigantic mixing spoon. To get that unburned hydrogen from the radiative and convective zones down into the core.
One idea is that you could crash another star into the Sun. This would deliver fresh fuel, and mix up the Sun’s hydrogen a bit. But it would be a one time thing. You’d need to deliver a steady stream of stars to keep mixing it up. And after a while you would accumulate enough mass to create a supernova. That would be bad.
But another option would be to strip material off the Sun and create red dwarfs. Stars with less than 35% the mass of the Sun are fully convective. Which means that they don’t have a radiative zone. They fully mix all their hydrogen fuel into the core, and can last much longer.
Imagine a future civilization tearing the Sun into 3 separate stars, each of which could then last for hundreds of billions of years, putting out only 1.5% the energy of the Sun. Huddle up for warmth.
But if you want to take this to the extreme, tear the Sun into 13 separate red dwarf stars with only 7.5% the mass of the Sun. These will only put out .015% the light of the Sun, but they’ll sip away at their hydrogen for more than 10 trillion years.
Stick the Earth in the middle and you’d have some very odd sunrises and sunsets, not to mention orbital dynamics. Created with Universe Sandbox ²
But how can you get that hydrogen off the Sun? Lasers, of course. Using a concept known as stellar lifting, you could direct a powerful solar powered laser at a spot on the Sun’s surface. This would heat up the region, and generate a powerful solar wind. The Sun would be blasting its own material into space. Then you could use magnetic fields or gravity to direct the outflows and collect them into other stars. It boggles our imagination, but it would be a routine task for Type III Civilization engineers on star dismantling duty.
So don’t panic that our Sun only has a few billion years of life left. We’ve got options. Mind bendingly complicated, solar system dismantling options. But still… options.
Special Guests:
Dr. Frank Timmes is an astrophysicist at Arizona State University and will be discussing online astronomy education and the Global Freshman Academy. His interests include the universe’s evolving composition and its implications for life in the universe. Dr. Timmes’ current area of research is nuclear astrophysics and the creation of the periodic table.
We are now using a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page.
