Chapter 35 The Big Bang
FinalThe Big Bang
Earth is only one of may planets orbiting the sun. Yet Earth is the only living planet. But it's possible that the universe is teeming with life. The universe is inconceivably huge. The distances are so great that we measure them in light-minutes and light-years.
is the distance light travels in one minute. And that's a long way, because light travels through space at 300,000 kilometers a second. That means that a light-minute is 60 times 300,000--or 18 million kilometers. A light-year
is nearly ten trillion kilometers.How far away is the sun?
It's a little over eight light-minutes away. The rays of sunlight warming our faces on a hot June day have traveled for eight minutes through the universe before they reach us.
Pluto, which is the planet farthest out in our solar system, is about five light-hours away from us. When an astronomer looks at Pluto through his telescope, he is in fact looking five hours back in time. We could also say that the picture of Pluto takes five hours to get here.
Our sun is one of 400 billion other stars in the galaxy we call the Milky Way
. This galaxy resembles a large discus, with our sun situated in one of its several spiral arms. When we look up at the sky on a clear winter's night, we see a broad band of stars. This is because we looking toward the center of the Milky Way.
The distance to the star in the Milky Way that is our nearest neighbor is four light-years. But that's only the nearest star. The whole galaxy--or nebula, as we call it- is 90,000 light-years wide. That is another way of describing the time it takes for light to travel from one end of the galaxy to the other. When we gaze at a star in the Milky Way which is 50,000 light-years away from our sun, we are looking back 50,000 years in time.
The only way we can look out into space, then, is to look back in time. We can never know what the universe is like now. We only know what is was like then. When we look up at a star that is thousands of light-years away, we are really traveling thousands of years back in the history of space.
Everything we see meets the eye in the form of light waves. And these light waves take time to travel through space. We could compare it to thunder. We always hear the thunder after we have seen the lightning. That's because sound waves travel slower than light waves. When we hear a peal of thunder, we are hearing the sound of something that happened a little while ago. It's the same thing with the stars.
Astronomers say there are about a hundred billion of such galaxies in the universe, and each of these galaxies consists of about a hundred billion stars. We call the nearest galaxy to the Milky Way the Andromeda nebula
. It lies two million light-years from our own galaxy. That means the light from that galaxy takes two million years to reach us. So we're looking two million years back in time when we see the Andromeda nebula high up in the sky. If there was a clever stargazer in this nebula--pointing his telescope at Earth right now--he wouldn't be able to see us. If he was luck, he'd see a few flat-faced Neanderthals.
The most distant galaxies we know of today are about ten billion light-years away from us. When we receive signals from these galaxies, we are going ten billion years back in the history of the universe. That's about twice as long as our own solar system has existed.
Although it is hard enough to comprehend what is means to look so far back in time, astronomers have discovered something that has even greater significance for our world picture. Apparently no galaxy in space remains where it is. All the galaxies in the universe are moving away from each other at colossal speeds. The further they are away from us, the quicker they move. That means that the distance between the galaxies is increasing all the time.
If you have a balloon and you paint black spots on it, the spots will move away from each other as you blow up the balloon. That's what's happening with the galaxies in the universe. We day that the universe is expanding.
Most astronomers agree that the expanding universe can only have one explanation: Once upon a time, about 15 billion years ago, all substance in the universe was assembles in a relatively small are. The substance was so dense that gravity made it terrifically hot. Finally it got so hot and so tightly packed that it exploded. We call this explosion the Big Bang.
The Big Bang caused all the substance in the universe to be expelled in all directions, and as it gradually cooled, it formed stars and galaxies and moon and planets...
The universe is expanding because of the explosion billions of years ago. The universe has no timeless geography. The universe is a happening. The universe is an explosion. Galaxies continue to fly through the universe away from each other at colossal speeds.Will they go on doing that for ever?
Possibly but there is another. Even though the universe continues to expand, the force of gravity is working the other way. And one day, in a couple of billion years, gravity will perhaps cause the heavenly bodies to be packed together again as the force of the huge explosion begins to weaken. Then we would get a reverse explosion, a so-called implosion
. But the distances are so great that it will happen like a movie that is run in slow motion. You might compare it with what happens when you release the air from a balloon.Will all the galaxies be drawn together in a tight nucleus again?
Yes. There would be another Big Bang and the universe would start expanding again. Because the same natural laws are in operation. And so new stars and galaxies will form.
Astronomers think there are two possible scenarios for the future of the universe. Either the universe will go on expanding forever so that the galaxies will draw further and further apart--or the universe will begin to contract again. How heavy and massive the universe is will determine what happens. And this is something astronomers have no way of knowing as yet.
But if the universe is so heavy that it begins to contract again, perhaps it has expanded and contracted lots of times before.
That would be an obvious conclusion. But on this point theory is divided. It may be that the expansion of the universe is something that will only happen this one time. But if it keeps on expanding for all eternity, the question of where it all began becomes even more pressing.
For a Christian, it would be obvious to see the Big Bang as the actual moment of creation. The Bible tells us that God said 'Let there be light!' From this 'linear
' point of view of a Christian belief in the creation, it is better to imagine the universe continuing to expand.
Some cultures with a 'cyclic'
view of history (history repeats itself eternally). In India, for example, there is an ancient theory that the world continually unfolds and folds again, thus alternating between what Indians have called Brahman's Day and Brahman's Night. This idea harmonizes best, of course, with the universe expanding and contacting-in order to expand again-in an eternal cyclic process.
The planet is alive. All organisms are made of elements that were once blended together in a star.
When radio telescopes can pick up light form distant galaxies billions of light-years away, they will be charting the universe as it looked in primeval times after the Big Bang. Everything we can see in the sky is a cosmic fossil from thousands and millions of years ago. The only thing an astrologer can do is predict the past.
If it's a clear night, we can see millions, even billions of years back into the history of the universe. So in a way, we are going home.
We also began with the Big Bang, because all substance in the universe is an organic unity. Once in a primeval age all matter was gathered in a clump so enormously massive that a pinhead weighed many billions of tons. This 'primeval atom'
exploded because of the enormous gravitation. It was as if something disintegrated. When we look up at the sky, we are trying to find the way back to ourselves.
All the stars and galaxies in the universe are made of the same substance. Parts of it have lumped themselves together, some here, some there. There can be billions of light-years between one galaxy and the next. But they all have the same origin. All stars and all planets belong to the same family.But what is this earthly substance? What was it that exploded that time billions of years ago? Where did it come from?
We ourselves are of that substance. We are a spark from the great fire that was ignited many billions of years ago. However, we must not exaggerate the importance of these figures. It is enough just to hold a stone in you hand. The universe would have been equally incomprehensible if it had only consisted of that one stone the size of an orange. The question would be just as impenetrable. Where did this stone come from?