What is the Universe?
The Universe consists of all the matter and energy since the beginning of time …as we know it. It is the totality of all things that exist. Most people would agree with this description. However most people will also think that this description is talking about the things we can “see”, both with our modern instruments as well as with our eyes. But there is more…..much, much more!
The Universe can be thought of as consisting of three parts……the Material part (the part we see), Dark Matter, and all the Energy…including Dark Energy:
1. Material part….. all the things we can observe, or measure:
-our Earth, the Moon, the Sun, the planets, their moons, the asteroids, plus the space and molecules between the planets…….this is our Solar System.
-the stars we see at night, their Solar Systems, the gas clouds within the Milky Way, Black holes, .plus the space and molecules between the stars……..this is our galaxy, the Milky Way.
-other galaxies, and gas clouds, and Black Holes, and the space and molecules between the galaxies.
….all of this is part of the universe…a really big part! ….but not the biggest!
You will note above that the material part includes all that we are familiar with…liquid, gas, and solid material….all of it. But it also includes plasmas…high energy particles which are atoms stripped of their electrons. You will find this hard to believe but plasmas are thought to make up 99% of the material world. (You can bet that Madonna did not see this coming!). So what we are familiar with…the gas, liquids, and solids….is only 1 % of the material world!
2. Dark Matter… scientist are beginning to believe that there is some missing material, stuff we cannot see nor measure, what they call Dark Matter, and it is a lot of matter! It is thought that this Dark Matter is larger than the Material part! See the Structure/Dark Matter tab above for more discussion of Dark Matter.
3. Energy….all the energy that is flowing from one place to another. There is a ton of energy here……light energy, x-rays, gamma rays, and other weird forms of energy…including Dark Energy…. coming from all the activity going on in the universe. This an extraordinary amount of energy! And if you were to equate this to material (remember E=mc2?). this would be the most material in the universe!
The contents of the universe then consist of three categories of “stuff” :
- Material Matter. All of that which we can see, touch, feel, or measure……….5% of the universe (and, as noted above, plasmas are thought to make up 99% of this)
- Dark Matter. We can’t see it or measure it, but it keeps us together………23% of the universe
- Energy. Most of this is Dark Energy…we can’t see it or measure it, but it keeps us expanding….72% of the universe
Note carefully the percentages indicated above. Astronomers today believe that, by far and away, what we see in this universe, the Material Matter, is just the tip of the iceberg. It is currently believed by most astronomers and scientists that Dark Matter and Dark Energy make up 95% of the universe. How do we know this? A recent probe measuring cosmic microwave background (CMB) has provided 5 years of data which scientists have been able to analyze and come up with a determination of the approximate age and contents of the universe20. The contents are given above…the age currently is figured to be 13.73 billion years, or, as I like to think of it….13,730 million years, ± 120 million years. To take this one more step, given the above percentages, all of the gas, liquid, and solids that we are familiar with make up only 0.05% of the universe! Most of the universe is dark matter, dark energy, and plasmas. This is an amazing concept but keep in mind that it is currently only a theory. There may be alternatives to this so keep an open mind!
Check out the Structure tab above for further information on the structure of the Universe, but for now consider that the universe consists of a lot of wonderful events that are constantly occurring within galaxies, and often between galaxies. To whet your appetite, consider for a moment these facts:
- At night, we see in the sky only a small percentage of the stars in our galaxy, the Milky Way. How many stars do we see on a clear night? …maybe 50,000? There are 200,000 million stars in the Milky Way alone!
- But hold on….there are 50 other galaxies like ours in our small, local, neighborhood……relatively close to us. It’s called the Local Group. We’re one of the bigger galaxies in this group.
- A few of these 50 nearby galaxies are the same size as ours….but most are smaller. Still, even the small ones have 100’s of millions of stars!
- And did you know that our galaxy, the Milky Way, is currently in the midst of a collision with one of the smaller galaxies, the Sagittarius Galaxy? Yes it is true…the Milky Way is currently absorbing another galaxy as you read these words! Of course it will take millions of years for the process to complete, and without affecting our solar system, or so we think.
- And beyond our Local Group is the rest of the Galaxy Cluster we are part of….a Cluster being a group of 1000’s of galaxies.
- And then there are millions more Galaxy clusters beyond ours.
- We are now talking of in excess of billions of galaxies! …each with billions of stars!
- And each one of the galaxies, in all of the clusters, likely has a Black Hole in the center which can have the mass of a million million stars!
- It gets worse….if you think the above is telling us that there is a lot of matter in the universe, we now know that the Gas Clouds which permeate the Galaxies, contain more mass then the stars themselves!
- Then there is the little matter of Dark Matter….which does matter. We need it to keep all the other matter from flying apart! (…to be consistent with Keplers Laws of Motion……ho humm…..)
- And then there is the last item, Energy…and the largest piece of energy is ….Dark Energy! It is thought that there is more than twice as much “matter equivalent” in Dark Energy than in all the Dark Matter and Visible Matter combined.
As you can see this is now getting to be a little ridiculous…it’s as if we have gone crazy with numbers. But, consider for a moment that the above is true….and it is what smart astrophysicists and astronomers of today believe, supported by pretty solid observations. When you are outside on a clear night, look up and see the stars….and realize for a moment that there is so much more out there waiting to be discovered. We are living at a time when some of those discoveries will be made. Hopefully you will be a bit more prepared to appreciate those discoveries.