Looking up into a dark night sky like we have here in the Methow Valley, we can see thousands of stars. That view is just the tip of the iceberg, so to speak. In our own Milky Way galaxy there are hundreds of billions of stars, and there are hundreds of billions and even trillions of other galaxies with that many or more stars in the universe close enough for us to see.
Did you know that there are more stars out there than there are individual grains of sand on Earth? Think about that for a moment. All the sand on all the beaches and in all the sand dunes in the deserts on Earth. That is a lot of stars.
Yet the stars, as numerous as they are, only make up one-half of 1% of all the “stuff” in the universe. What could the other 99.5% be? You might think that the planets would add up to quite a bit, but our sun weighs 333,000 times as much as the Earth. Even Jupiter, the largest of the planets, weighs less than 1% of the sun.
So, add up a few odds and ends like neutrinos, hydrogen and helium gas floating around out there and you come up with 5% of the total ingredients of the universe. This is what we call baryonic matter and it is made up of atoms. It is the type of matter that we are familiar with.
Everything from the pesky hairs growing out of our ears to hydrogen deep in the core of stars is made out of it. That leaves 95% of the universe that we do not really know much of anything about.
Back in the 1930s, astronomers were measuring the rotation of our own Milky Way galaxy and other nearby galaxies. They realized that the galaxies were spinning too fast. Stars would be flung out of them by centrifugal force like a merry-go-round run amok, tossing riders right off of it. What was needed to keep things together was more gravity and more mass to account for that gravity, a lot more mass. Thus the idea for dark matter was born and astronomers figure there is over five times as much of it as regular matter that we are familiar with.
Why is it call dark matter? It does not emit, reflect or absorb light so we cannot see it. It is dark. What is it? Scientists are scratching their heads over that one. One candidate is something they call WIMPS, Weakly Interacting Massive Particles, which means they do not have a clue. Where is it? Everyone agrees it surrounds galaxies and gives them that extra gravity needed to make them work. Some propose that there is trillions of tons of the stuff floating around in space between us and the moon. That is kind of creepy. Others think there may even be dark matter actually “swimming” through our bodies right now. That is really creepy.
Scientists are foaming at the mouth to figure it all out. They want to build a detector to find dark matter, but it has to be big, like the size of the Earth. Some have pointed out that we already have a ready-made detector, the crust of the Earth. It has been around a long time, and if we could figure out what to look for, we might find evidence of dark matter right beneath our feet.
It has even been suggested that if you have a granite counter top, and can get your hands on an electron microscope, you might be able to find “scars” left by a dark matter particle slamming into a granite atom. Think about that the next time you are chopping up vegetables on your counter top.
So there is 5% ordinary matter, 27% dark matter, but that leaves 68% left over which is most of what is out there in the universe. What is it? I will give you a clue. It is another dark something that nobody knows hardly anything about. Tune in another time for more on that one.
If you are looking for something fun and easy to spot out there, Saturn should be visible low in the southeast as soon as it gets dark. Much-brighter Jupiter will be up later, a steady yellowish light in the east. Do not forget about the Northern Lights. With all the space weather bombarding us from the sun, you just might get a glimpse of their graceful undulating curtains. Where should you expect to see them? In the north, of course, but I am sure you figured that one out. Look up there as much and as hard as you can, but I do not think you will see any dark matter.