Imagine a place where there is no light or sound or anything that could be seen by the naked eye. Although there is something there, but it has a gravity so strong that nothing can escape it. There was a place like this billions of years ago, the beginning of the universe!

, Kaboom!! The largest explosion ever has just happened (One would see light first because light travels faster at 186,000 miles per second. Then one, supposing one could survive it, would hear sound only after some of the material was around you, because sound is caused by vibrations and in a vacuum their isn’t anything to vibrate). All the matter around that people see and touch and even more matter that one can’t see or touch and even more matter that one can’t see or touch is expanding (Not expanding like everything is getting bigger, but like having something extremely dense and going to something less dense. Which would make it appear to be expanding),all of the matter in the stars, plants, and even the stuff that will eventually be all of the organisms on Earth are made of is formed. About one second after the big Bang matter was in the form of free neutrons and protons, but no elements existed yet because the temperature was to high. As the universe expanded, the temperature fell and some of these nucleons were synthesized into light elements: deuterium(D), helium-3, and helium-4 (Shellard). The heavier elements were created later in the interior of stars and spread widely in supernova explosions (Shellard).

Most people think the Big Bang was this huge fire ball. If this is true, where did all of this energy go? This sudden expansion released all of the energy in the universe, Even though people think their is a lot of energy around, like in the sun, its only a fraction of what there is. The law of conservation of energy says that energy connot be lost, but it can be converted into other forms of energy such as heat, light, and sound.

After this gigantic explosion there was all this matter around (mostly helium). This huge cloud of matter (called a nebula)started to bond together and spin (because of gravity). After a while there would be a bigger mass of matter in the middle that bonded with more matter than the rest. After is got so bug, nuclear fission started because the gravity was so great, and that is how the sun was made. It liked like a big pancake with a big ball in the middle. This system of a sun and planets and other matter in orbit is called a solar system.

Stars shine because they burn up the helium and other gasses for fuel. This helps keep them from collapsing. How long a star lives depends on hoe big it is. The more mass a star has, the more energy it can make. But, a bigger star uses up its energy very fast. A smaller star will sue its every slower and live linger. When stars like the Sun sue up their fuel, the outside layer of gas in the star is blown off into space as a shell (Heasley). Stars that are much bigger than the Sun don’t die as gently and quietly. These stars blow up in a huge explosion. This huge explosion is called a supernova. The star becomes very bright for a short time as it blows itself up (Heasley). What is left is a neutron star, if the star is large enough what is left over might turn into a black hole. The supernova shoots gas and other matter out into space. These shells of gas move away from the star very fast (Heasley). This gas will become what we call a supernova remnant. The supernova remnant will be sued to make other stars.

Their are other masses of matter that didn’t get bug enough to star nuclear fission, the planets. The young planets were hit with almost a constant shower of comets, meteorites, and asteroids which made them bigger. Just look at the moon; there are creators all over. Where are all the creators on Earth? Well, they are there its just hard to find because most of them were eroded away. There are a lot of craters around but one has to know where to look. note to myself: SAY WHERE THEY ARE-get pic's

Asteroids are large chunks of rocky or iron material. They usually orbit the Sun between Mars and Jupiter. Astronomers think that they are pieces of a planet that never formed there because of the immense pull from Jupiter’s gravity. With telescopes astronomers can see thousands of these small objects. The Galileo spacecraft took pictures of two asteroids large Earth-Killer asteroids. Now astronomers are also studying asteroids using the Space Telescope and radar from Earth (Heasley). The craters on it show that even small things tile asteroids bump into other things in space (Heasley).

Comets are balls if ice and rock that are left over from when the solar system formed almost 10 billion years ago. Sometimes the gravity from the planets will pull one of these comets into the inner solar system where Earth is. Then the hear from the Sun will warm the comet, and is will form a long tail. Some comets are in orbits that bring them back again and again. When Haley’s Comet came near the Sun in 1986, the Giotto Spacecraft went to visit it (Heasley). It took this close-up picture of the comet. The comet appears to be very big because of gas and dust that evaporate from it when the Sun heats it. The solid part of the comet is really very small, only about 10 miles across (Heasley).

A solar system is just a sun, with planets and debris rotating around it. A galaxy is a whole bunch of solar systems, held together by gravity, rotating around each other (maybe around a central point like a black hole). A galaxy can be thousands of light years wide containing billions of stars. The observable universe contains about 10 to 100 billion galaxies (SkyDEN). Their are three types of galaxies: spiral, elliptical, and irregular. the Sun and the Earth are in the Milky Way, a spiral galaxy. An elliptical galaxy has a ball shape and in irregular galaxy has no regular form.

Just like galaxies are a whole bunch of solar systems, galaxies are in larger structures called Galaxy Clusters (or just clusters). Clusters can be millions of light years across. The Milky Way is part of the cluster called Local Group (SkyDEN).

Yet even bigger there are superclusters. As anyone could guess it is made up of thousand of galaxy clusters. The Local Group is in the supercluster called the Local Supercluster. Surrounding the Local Supercluster is a gigantic void measuring about 300 million light years across, bigger that the Local Supercluster (SkyDEN). Is their yet a bigger structure that is so big that people could not see because of being on a scale of hundreds of millions of light years? (SkyDEN). No one knows.

If there was a lot of mass in a small volume, you will create a very strong gravitational field. A black hole is a body so dense that even electro-magnetic radiation cannot escape from its strong gravitational pull. A black hole is surrounded by the event horizon, a spherical boundary whose radius is often referred to as the Schwarzschild radius (Soper). Once any object enters the event horizon it can never escape. This principle also goes for light, which is the reason a black hole is black.

People know that the universe is still expanding because Slipher measured the spectra of a nebulae and it had a red redshift. Almost everything people can observe, from Earth, in outer space has a redshift. When a train comes toward one its whistle sounds high, then when the train asses one the whistle sounds lower. This is the Doppler effect. When the train is coming towards one the sound waves are compressed which make a higher sound pitch, and when the train is moving away the sound waves are farther apart which makes a lower sound pitch. This also works for light. When something that gives off light that has a violetshift then its coming toward one. If it has a red shift it is moving away.

Their are two ways the universe could end. The first is called The Big Chill. If the universe does not have enough matter within it, then the gravitation generated by matter would be too weak to stop the universe from growing. This would cause the universe to expand forever. As the universe continued to grow, the galaxies would get dimmer and dimmer as they sped away. Moreover, the stars would inevitably exhaust their nuclear fuel and there light would eventually be extinguished (SkyDEN). This would happen if the universe just keep expanding until the temperature drops, and the stars would run out of fuel, (temperature would drop because the same temperature in a larger area would make the whole the same temperature, but in a spot in the area would be lower then a small area) and everything freezes and dies.

The second way the universe could end is by The Big Crunch. On the other hand, if the universe has enough matter, the gravitational attraction of the matter would be strong enough to slow down the expansion until the universe began to shrink (SkyDEN). When the universe started collapsing, it would eventually return to its childhood state (SkyDEN). The temperature and matter density would get higher and higher, just like the Big Bang in reverse. In this theory the universe will start to collapse back in to itself (because of gravity) and become a huge black hole.

If this could happen maybe there would be another explosion and start the universe over again and just keep alternating like this. Start as a small point explodes, clump back up, and explode again for infinity. Although their will be know way of ever knowing.

Bibliography

Soper, Davison E. “Black hole basics.”
http://zebu.uoregon.edu/~soper/MilkyWay/blackhole.html
(5/17/98)

Heasley, James N. “ASTRONOMY FOR C-5 The KEIKI TOUR,” c. 1997
http://hoku.ifa.hawaii.edu/astrokid/files/hello.htm
(5/17/98)

Shellard, Paul. “Cambridge Cosmology: Hot Big Bang.” 1996.
http://www.amtp.cam.ac.uk/user/gr/public/bb_home.html
(5/6/98).

“SkyDEN.” http://www3.actden.com/sky_den/contents.htm
(5/6/98)