The stars are some of the most fascinating objects there are. They are existence itself- the shaping of matter into its unbelievable complexity and breathtaking form. There are some fantastic sights to explore, wonders which no living thing has ever seen, on our very doorstep. And what you will find is that our doorstep is a tiny, tiny thing.
The most visible star in the sky is Sol, our sun. We like to think that we consume a lot of energy. The sun, however, laughs at what we call our ‘massive energy requirements’.
The sun: By far the most powerful object in our lives
In fact, all of the energy we have ever consumed comes from the sun. Fossil fuels are the remains of plants, before bacteria evolved a way to eat their remains. The plants just died and accumulated in huge numbers, eventually becoming buried beneath the soil, and later, rock. Millions of years later we found these dead plants and burned them, using their energy to power our devices.
These plants got their energy from where most plants get it- the sun! A plant is just a solar panel. Instead of storing the energy it harvests in a battery, it keeps it in sugar. This sugar is what sustains much of Earth’s wildlife, including humans.
Wind energy and hydroelectric energy also comes from the sun. The air in our sky is heated and as everyone knows, hot air rises. But when it rises, other air rushes in to fill the gap it leaves behind, which is what wind is. So the energy from wind ultimately comes from the sun as well.
The same goes for water. Water is heated by the sun, evaporates, and later rains down on land. The water collects and runs in the form of rivers, lakes, ponds, and eventually gets to oceans. But on the way, there are many waterfalls and strong currents which we can obtain energy from.
How much energy does all of humanity use in a year? About 5 x 10^20 Joules, or 5 followed by 20 zeroes. That is a massive number. And yet, the sun produces 1.5 x 10^22 Joules. Which is 15 followed by 21 zeroes, or 30 times what we as a species use in a year. This is produced in 0ne day.
We think we have mastered nature, when the reality is we aren’t even on the scale. The sun produces more than 30 times the energy per day than 7 billion people use in a year.
Except that I lied. That’s just the energy that strikes the face of the Earth. Want to know how much energy the sun actually produces in a day?
Asking how much light strikes the Earth relative to how much the sun produces is like putting a candle at one end of a football stadium, and measuring how much of its heat reaches the other end of the stadium. It’s a miniscule percentage, and so the sun’s total energy output is absurd.
Walk just 10 metres and you won’t feel the candle’s heat. And yet, if the sun were a candle its heat would feel quite strong from 100 metres away.
The actual number is 3.3 x 10^31 Joules, or 33 followed by 30 zeroes. That is 1,000,000,000 times as much as we use in a year. That’s right, if we continued living as we do now, we would have to live for a billion years before we used as much energy as the sun produces in one day. To get a sense of how long that is, a billion years ago life was simple multicellular- mostly bacteria and algae. There were no plants, no animals, no bugs. All of that evolved in the last billion years.
This is why you don’t look directly at the sun, because you are less than a speck of dust when compared to its sheer might.
Forgive me for digressing, but this is why nuclear fusion is what we should be looking at as soon as possible. The sun is able to produce this much energy because it collides hydrogen atoms together and fuses them into helium. We are a hair’s breadth away from recreating this process on Earth. If we are able to do that, then we will be able to produce enough energy in one day to satisfy all of our energy needs for a year. All of our food, electricity, fuel, and enough left over to embark on projects that we currently consider impossible. Not just things like solving world hunger and halting climate change, but things like building enormous space colonies, transmuting elements, bringing lost species back to life. Even making other planets habitable and traveling to distant galaxies. All it takes is investing into nuclear fusion research. If a politician says he/she wants to invest in nuclear fusion, you should probably vote for them.
But back to the sun. Now the reason we aren’t annihilated by the sun’s energy is because it is really far away. I can’t really describe to you how far apart things are- you will have to just see it yourself. Here is a model of the solar system to scale. Hold the right arrow and enjoy- it’ll be a while before you hit Earth. Props if you make it to Jupiter.
I won’t get into the details about each of the planets in our solar system here. I do in Planets and Pluto, and I encourage you to read it. Each of the planets is unique and seriously cool.
The solar system, not at all to scale. If it was, then the first planet, Mercury, would be far beyond the wall of the room you’re in.
Even the distance from the Earth to the Moon is much larger than we tend to think. This is that distance, to scale. Not pictured: the Sun’s diameter, which is 3 times this distance.
As big as the sun is, the space in between the sun and the Earth is much, much bigger. And that’s not even a relatively significant distance. The entire solar system, all 8 planets and Pluto (sorry, it really isn’t a planet), spans a distance too great for our minds to comprehend.
And all of that, our solar system, our home, is nothing compared to the rest of our galaxy.
There are around 100 million stars in the Milky Way. 100 million chances for there to be life within the galaxy. 100 million gigantic spheres of unbelievable power, most of which are bigger than our own sun. Some of those are dozens of times more powerful. Others are thousands of times. I will not go into detail regarding the different classifications of stars, but I do in Suns and Stars (coming soon).
A blue supergiant- one of the bigger class of stars in the universe, to which our sun is but an ant to an elephant
I must apologize for lying again. There are about 100 million stars in the Orion-Cygnus Arm of the galaxy alone. 100 million stars in one arm of the Milky Way galaxy. But, I mean, the arms of the galaxy are huge, right? The Orion Arm is what, a quarter of the Milky Way? At least an eighth?
The arms of the Milky Way
Wrong. The Orion-Cygnus arm is one of the smallest arms of the Milky Way. In fact, there is debate over whether it should be called an arm at all, or whether it’s just an offshoot of the much larger Carina-Sagittarius arm. The Orion Arm makes up less than 0.2% of the Milky Way in terms of the number of stars.
Which means that our Milky Way galaxy actually contains about 300 billion stars.
I apologize for the roundabout method of getting to this number, but a number like “billion” isn’t easy for our minds to grasp. And when you pair that concept with the enormity of stars, solar systems, galaxies, and other things that are just too large to wrap our heads around, it’s a bit numbing to say the least.
The Milky Way galaxy has billions of years worth of things to explore. Half of its stars are thought to be in the bulge at the centre of the galaxy. There are two major arms of stars, and about three smaller arms not including the Orion-Cygnus arm. They contain stars ranging from smaller than Earth to a third of the size of our entire solar system.
And thought to be at the very centre is a supermassive black hole. Its radius is unknown, but it is thought to be about the size of Uranus’s orbit. But the really astonishing aspect of this thing is, as the name suggests, its mass, which weighs in at 4.1 million.
Suns.
And then there are other galaxies. Some are smaller than ours, containing just a few hundred million stars. Our closest neighbour, Andromeda, contains about a trillion stars. Which makes it more three times the size of the Milky Way. On a clear night in the middle of a field with no light pollution, however, only 6 galaxies are visible to the naked eye. Most of the stars belong to the Milky Way, and most of them are part of the Orion-Cygnus Arm. When you marvel at the sheer vastness of the cosmos in the night sky, you are seeing an abysmally tiny fraction of it.
Stop and reflect on that. Everything that I talked about earlier, with the Orion-Cygnus Arm and the other 5 arms (which are all bigger) fit into the Andromeda galaxy… three times.
The Milky Way, Andromeda, and 60ish other galaxies around us comprise the observable universe.
Our local group. The Andromeda and Milky Way galaxies are tiny blips in this image
Kidding again. They make up the local group. Surely this is it. We must be getting close to the edge of the universe by now.
Wrong. Totally, completely, amusingly wrong. Our local group is a small one. It’s not the tiniest, but it’s below average in size. A local group is like one seed of one strawberry of one strawberry bush of a field of strawberry bush in strawberry country. And what a seed it is- need I remind you that the Orion-Cygnus arm of the Milky Way galaxy is bigger than our minds are able to grasp? The Andromeda galaxy, bigger than our own, is one of 59 other galaxies in our local group. To be fair, the Andromeda and Milky Way galaxies are the largest galaxies in the group. But the group itself is nothing special… not even close.
Collections of galaxies can be known as either galaxy groups or galaxy clusters. Galaxy groups contain about 50 galaxies, all held relatively close together by their massive, collective gravity. A galaxy cluster can contain anywhere from hundreds to thousands of galaxies. The Virgo cluster, which is the closest galaxy cluster to us, contains anywhere from 1200 to 2000 galaxies. Yes, it is at least 20 times the size of our local group, which contains our enormous galaxy, a galaxy three times the size of our enormous galaxy, and 57 other galaxies. There are bigger galaxy clusters, but unfortunately they are too far away to reliably estimate the number of stars they contain (remember, only 6 other galaxies are visible to the naked eye on a perfect night, and 4 of these are part of our local group).
The Virgo cluster, about 20 times the size of our local group
But there is one more structure in the hierarchy. A supercluster contains hundreds, sometimes thousands of galaxy clusters and galaxy groups. Until recently, our Local group and the Virgo cluster were thought to reside in the Virgo Supercluster, which contained about 100 galaxy groups and clusters. Just this year, the Laniakea supercluster was discovered/proposed, which contained the Virgo supercluster, Hydra-Centaurus supercluster, and the Pavo-Indus supercluster, a total of 300-500 galaxy groups and clusters.
There are about 15 known superclusters in addition to the Laniakea. But there is something blocking out about 20% of the night sky, and we can only guess what lies beyond. Our own Milky Way has too much dust and gas to see beyond it. This is called the zone of avoidance, and it may not be insurmountable- it is possible that by observing other wavelengths, we can see past it.
The map of the nearby superclusters. Each of those dots is a large galaxy or galaxy group. The very centre of this image is where the Milky Way Galaxy resides
After the superclusters, we get to the observable Universe. Light beyond this region takes longer than the age of the universe to reach us, which means that we cannot hope to see past it. But as for material to explore, there are billions of lifetimes worth of stars in our own Milky Way- and when you consider that it is possible for life to exist on another planet in our tiny, inconsequential solar system, it is almost certain that within the hundreds of billions of stars in our own galaxy, life resides in abundance. Even if a hundredth of these systems can support life, then there are billions of planets teeming with it. Of these billions, if one in a million gives rise to intelligence- then by sheer volume, there are hundreds of sentient species within our own galaxy. Of all the galaxy groups, galaxy clusters, and galaxy superclusters, how many do you think are more advanced than us? And by how much? This is why we need a space program. Exploration is what drives us forwards. And there is plenty to explore.
Here is a brilliant module which has the entire universe to scale. Try going all the way to the right. It is a great way to visualize the distances we talked about.
Sources:
Image of Sun retrieved from http://upload.wikimedia.org/wikipedia/commons/a/a3/Giant_prominence_on_the_sun_erupted.jpg
Image of candle retrieved from http://upload.wikimedia.org/wikipedia/commons/4/4b/Candle.jpg
Image of Earth-moon distance retrieved from http://upload.wikimedia.org/wikipedia/commons/5/5c/Earth_Moon_Scale.jpg
Image of Solar System retrieved from http://upload.wikimedia.org/wikipedia/commons/a/a9/Planets2013.jpg
Image of sun compared to blue supergiant retrieved from http://www.slate.com/content/dam/slate/blogs/bad_astronomy/2013/04/17/bsg_sun.jpg.CROP.original-original.jpg
Image of Milky way arms retrieved from http://en.wikipedia.org/wiki/Milky_Way#mediaviewer/File:Milky_Way_Arms.svg
Image of local group retrieved from http://en.wikipedia.org/wiki/Local_Group
Image of Virgo cluster retrieved from http://upload.wikimedia.org/wikipedia/commons/4/44/Virgo_cluster_052012_overlay.jpg
Image of Superclusters retrieved from http://upload.wikimedia.org/wikipedia/commons/d/d8/Nearsc.gif
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