Given the size and age of the universe, it’s no wonder that mankind has only scratched the surface when it comes to understanding it. Astronomers can answer many questions about space, but there are some mysteries that we may never solve.
10. How Stars Explode
When a star has essentially burned itself out, a couple of possible outcomes will arise. A massive enough star may collapse under its own weight and form a black hole. Other stars go supernova, a concept that sci-fi fans should be familiar with enough to understand on a basic level. The star burns and expands and forms a red giant. It continues to expand until it collapses and then neutrinos in the star’s core rapidly expand and create a cataclysmic supernova explosion.
In computer modeling, scientists have had very little luck making a supernova happen. When provided with the observable data we have, computer stars collapse and that’s it. Their own gravity causes them to fold in on themselves. No giant explosion. And that is the central mystery of a supernova. If the star got so massive gravity made it collapse, how could it then explode outward so forcefully?
The fact that some stars do supernova and some stars don’t is still a bit of a puzzle. Presumably there is quite a bit we’re missing in terms of what goes on inside a dying star, but for now the picture is still unclear.
9. Where The Universe’s Light Come From
Most of us probably think of space as dark. It looks pretty black with just spots of light thanks to distant stars. But there’s a lot more light in the universe than you might at first think, and so far we’re not sure why.
NASA’s New Horizons probe left our solar system and headed off into the universe some years ago. On the way, NASA tried to filter out all known light sources to take a look at how bright the universe really was. They ended up with half of the background light still there, all of it coming from unknown sources.
It’s possible the light is just a trick and the reason New Horizons saw it was because of a technology issue. Or it’s possible the universe is just really bright for as of yet unknown reasons. In any event, half the light in the universe has no known source as far as we know right now.
8. What Dark Energy Is
When scientists first discovered that the universe was expanding faster than they thought it should, it raised a serious question: where was that energy coming from? An expanding universe needs power from somewhere and as far as we knew, there was not enough energy around to allow that to happen.
The concept of dark energy can help explain a lot of the mysteries of the universe. There had to be something out there allowing the universe to expand as it did. And based on what we know of the mass of the universe, there has to be a heck of a lot of it out there as well, but we’ll cover that shortly.
So the concept of dark energy is a decent way to explain why the universe expands the way it does, but the problem is no one knows what dark energy is or where it comes from. It’s an answer to one question, but it poses many more that still have to be solved.
7. Where Supermassive Black Holes Come From
Black holes are tricky things for more reasons than you might think. Science fiction has made them fairly well known and on some basic levels most people understand that a black hole is a super massive astral body with so much gravity that even light can’t escape. You may have even heard a black hole forms when a star collapses on itself. But that seems to only be true sometimes.
Supermassive black holes exist in the center of many galaxies, and they live up to the name. A supermassive black hole can have a mass that is tens of millions of times greater than our sun. Now our sun isn’t the biggest star in the universe by any means, so when a much bigger star collapses it could make a big black hole and over many millions of years that black hole could keep drawing in more mass and keep getting bigger.
The problem with supermassive black holes is that their mass is too big. Based on the age of the universe and what we know about how black holes form and grow, these supermassive ones just don’t make sense. They shouldn’t have gotten as big as they are.
Maybe these formed along with the creation of the universe. Or maybe they eat other gigantic black holes and get way out of hand. No one really knows why they’re as big as they are, or even how big they can become.
6. How Many Earth-Like Planets are There
In our little solar system alone there are eight planets, and maybe a ninth no one has tracked down yet. Of those, Earth is the only one with life on it. And when we expand our search beyond this solar system, we haven’t had any luck finding signs of life on other worlds just yet either. But how many worlds are we talking about? How many planets exist that could potentially support life?
Science cannot answer that question because it’s literally impossible with the level of technology currently at our disposal. The universe is colossal, some 92 billion light years across. Looking through all that space makes finding a needle in a haystack look like trying to find an elephant in your bathroom. And that’s not the worst of it.
We have no way of knowing exactly how many planets exist, but we can make some guesses. You can start with a general assumption about stars. Every star should have at least one planet. Remember, ours has eight, so this is super conservative. If there are 100 billion galaxies in the universe, then we’re already up to 100 billion planets. But a galaxy is made up of many solar systems and it’s estimated that there are about one billion trillion stars per galaxy. Now we’re at numbers so big they barely make sense and no one ever uses them in casual conversation.
The math on that works out to 70 quintillion planets. That’s a 7 followed by 20 zeroes. It’s completely unknown how many of those could be Earth-like or if any of them are. It’s just as possible that we truly are alone. Does it seem unlikely? It sounds like it should be, but science doesn’t really work that way.
We’ve identified a very small number of exoplanets that meet some of the criteria we think are necessary for life – their size, the distance from their star, etc. But it’s a frightfully small number and there’s still no sign that they’re bustling with life.
5. How Will the Universe End
We know a bit about the beginning of the universe, at least the moments after it started, but the future is even less clear. Where the universe is going has been the subject of debate for years and no definitive answer is forthcoming. Some speculation is that the universe has no end. It’ll just keep going. But there are competing theories that the universe will not be so lucky at all.
One of the most well known theories is the opposite of the Big Bang, which is the Big Crunch. If the Bang sent everyone out, the Crunch is like when an elastic is stretched to its limit and then shrinks back down to size. The universe will shrink and collapse down into maybe another Big Bang.
The Big Freeze proposes that the universe is heading toward heat death. Everything will eventually die out to the same uniform temperature across the universe until all matter and energy is dispersed and the vast emptiness of near Absolute Zero makes up the whole of existence.
Another possibility is that dark energy we mentioned earlier may be able to build up faster than the universe expands. Over time, we’ll have too much energy and like a powder keg it’s going to explode, effectively tearing the universe apart in what has been called the Big Rip.
4. Why the Sun is So Hot
It should come as no surprise to anyone that the sun is hot. It’s a giant ball of fire in the sky, that’s reasonable. But why it’s as hot as it is has been something of a mystery as far as science is concerned.
The surface of the sun measures at a scorching 10,000 degrees Fahrenheit. For some perspective, magma in a volcano can get up to 2,300 degrees and an oxy-acetylene torch can get up over 6,000 degrees. So that’s pretty impressive when compared to the sun. But then there’s the sun’s corona.
The corona of the sun, the zone around the sun full of burning plasma, gets much hotter than the surface. The temperature there can reach three million degrees. The science here is what’s confusing. If the core of the sun is where the heat comes from, why is it so much hotter on the outside? So far, we’re just not sure.
Just as an aside, it’s worth noting things do get even hotter on Earth. The Large Hadron Collider has smashed particles together and, for a very brief moment, created temperatures of over 7.2 trillion degrees, which is hotter than a supernova.
3. What Causes Fast Radio Bursts
A fast radio burst is a remarkably fast blip on the cosmic screen. They can last for just a millisecond or two and originate from somewhere far beyond our galaxy. They’re radio pulses of an unknown origin and they are, from a scientific standpoint, baffling. A single burst that lasts less than a millisecond can produce as much energy as the sun will over several days.
In 20 years, scientists have observed about 1,000 of these bursts. Only 15 have been traced back to the galaxy where they came from thanks to the fact they’re so incredibly fast. While it seems impressive to trace them to a galaxy, remember that a galaxy is massive. We’ve gotten no further so we have no idea where these powerful bursts come from or why.
The popular theory is that the burst may be caused by magnetars, the highly magnetic corpses of dead stars. But for now that remains just a theory.
2. What Most of the Universe is Made Of
There’s a whole lot of stuff in the universe and that stuff has a lot of mass. If you were to make a quick guess, you’d probably assume a sizable portion of the universe’s mass was made up of things. You know, matter. Dogs, planets, stars, that sort of stuff. You’d be terribly wrong, as well. It’s believed that, at the very most, matter makes up about 10% of the universe. Some estimates have it down at a paltry 1%.
The remaining 90% to 99% of the universe is believed to be made of two things. Dark energy and dark matter. If matter is 5% of the universe, then dark matter is 25% and dark energy takes up the other 70%. And, as we’ve already seen, we don’t even really know what the heck dark energy is.
Because we’re not sure of what exactly the rest of the universe is, we have no idea how much of it the universe is made from. It’s kind of like looking at a cake from the outside and trying to guess what ingredients went into making it. You can make some educated guesses, but good luck nailing it.
1. What Happened Before the Big Bang
The universe as we know it started 13.8 billion years ago with the Big Bang. Science has managed to speculate with a fair degree of certainty about what happened in the fractions of seconds immediately after the Big Bang took place. That’s all very impressive and something well worth researching if you’re curious about the origins of literally everything ever. But while we can speculate what happened one second after the Big Bang, trying to figure out what happened one second before it is all but impossible.
The very concept of before the Big Bang kind of defies logic. If you imagine it, you probably picture an explosion. And like any explosion we can see today, it’s a fixed point that explodes out. We understand how a grenade works; it explodes out and shrapnel flies about in the air. But the Big Bang can’t work like that because it created the universe. It didn’t explode out into anything because there was nothing there yet. Space expanded from the Big Bang. The concept doesn’t readily make sense. There was no empty space, or waiting universe. There was nothing. Or maybe there was. We have no way of knowing.
Was the universe already an infinite energy that exploded? Your guess is as good as anyone else’s. Stephen Hawking once argued it doesn’t even matter what happened before the Big Bang, because how could it matter? It’s meaningless to the way the universe works now, so just ignore it.