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Characteristics of the Universe

by Ron Kurtus (revised 30 November 2011)

The Universe consists of all the stars and galaxies of which we are aware. It is everything that is out there in the sky and is immense beyond imagination. In fact, it is difficult to grasp the great distances and large numbers involved in the universe. Our place and existence is tiny compared to everything else. The theory is that the Universe began with the Big Bang. There are also theories that other universes exist, parallel to ours.

Questions you may have include:

This lesson will answer those questions.



Size of Universe

The Universe is large in size and consists of billions of galaxies, which in turn consist of billions of stars.

Physical size

The size of the Universe is immense. It is estimated that the Universe is 156 billion (156,000,000,000) light years across. Since light travels at approximately 299,800 kilometers per second or 186,000 miles per second, you can see that the distance is very large.

Number of galaxies and stars

The Universe consists of approximately 100 billion galaxies. Each galaxy consists of anywhere from 10 million to 1 trillion (1,000,000,000,000) stars rotating around a center area.

Galaxy consisting of billions of stars

Galaxy consisting of billions of stars

Each star in a galaxy is a sun, similar to our Sun. Some stars are much larger than our Sun, while others are smaller.

Our galaxy

Our Sun, the Earth and planets in our Solar System are part of the Milky Way galaxy. It is called that because, on a clear night, the many stars in our galaxy almost look like milk spread across the sky.

Our view of the rest of the Milky Way galaxy

Our view of the rest of the Milky Way galaxy

Since we are in the Milky Way galaxy, our view of it is an edgewise view.

Beginning of the Universe

The major theory of how the Universe started is the "Big Bang" theory. This states that about 13.7 billion years ago (13,700,000,000 years) all matter was compressed to what some estimate was the size of a golf ball. It then exploded in a "big bang" and spread out until it has reached the enormous size of the present-day Universe.

While the matter was spreading out, it started to clump together into larger and larger masses. The turbulence of the explosion resulted in the spinning of the galaxies.

Measurements show that the Universe is still expanding. By interpolating the directions and velocities backward, astronomers have estimated the beginning time of the explosion. Of course, such measurements are highly inaccurate. There is debate on this theory and whether the Universe will continue to expand or will start to contract.

Other universes

There are theories that there may be other universes that we are not aware of. One theory says that there are parallel universes similar to our universe. Since we don't know how big our Universe is, there may be other universes outside our Universe's boundaries.

Another theory is that a black hole may actually be the starting point of the Big Bang of another universe. These are all abstract thoughts that cannot be proven.

(See Are Atoms Tiny Solar Systems? for another idea.)

Just the whole concepts of what's out "there" and where the universe exists are quite mysterious.

Summary

The universe is extremely large and consists of millions of galaxies and billions of stars. We are in the Milky Way galaxy. A major theory of the beginning of the universe is called the Big Bang Theory.


Help all those in your universe


Resources and references

Ron Kurtus' Credentials

Websites

Space Weather - News about Earth-Sun environment

Astronomy Resources

Books

Top-rated books on the Universe


Questions and comments

Do you have any questions, comments, or opinions on this subject? If so, send an email with your feedback. I will try to get back to you as soon as possible.


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