All areas of science, social sciences and theology have its own explanation of what was before what is now. Many even try to predict what is to come. Like any other science, physics and astronomy explanation of how the universe came into existence remain one of the most plausible explanations of the universe. This is called the ‘big bang theory.’

What is big bang?

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The name big bang was given to this theory by an astrophysicist named Sir Fred Hoyle who tried to mock this theory on a BBC radio program. This however has made the theory more popular. Something I believe he never intended. So sometimes there is a lot of good in evil as this case clearly illustrate.

The big bang theory came as a result of Einstein’s theory of general relativity which rightly predicted that the universe is still expanding even as of today. This rightly implies that the expanding universe started from a point and has been expanding ever since. This point is called a singularity. The big bang is estimated to have occurred about 13.7 billion years ago.

Singularities are zones that are infinitesimally hot, dense and small. Thanks to the likes of Steven Hawking, George Ellis, and Roger Penrose, who have been actively working on the theory of the black hole. Black holes are said to be areas of infinite pressure. That means, any finite matter that comes close to the black hole is actually swallowed up by it.

Big Bang theory, chapter 1

In the beginning, there was no space, time, mass and energy. There exists a singularity which harbored a huge amount of dark energy, and began to expand from an infinitesimally high temperature and density to the temperature of the universe as we know it today. Dark energy remains the mysterious force that scientists believe is responsible for the universe current accelerating expansion. In the beginning before anything existed, the universe underwent an awfully momentary and histrionic period of inflation, expanding at a rate faster than the speed of light. It doubled in size, perhaps more than 100 times in a fraction of a second. What created the singularity? We really can’t say but physicists believe it was in existence before space and time. The singularity suddenly appears, and we owe our existence to it.

General misconceptions about the big bang theory

Many people on hearing the word big bang, they think it implies some kind of loud explosion from a single point which marked the beginning of the universe. On the contrary, it does not imply any form of explosion. The bang in the big bang means inflation. The singularity is a point mass which began to inflate (expand), giving rise to space and has continued till this day. Just imagine an infinitesimally small balloon which began to inflate and become bigger and bigger with time. You get the concept?
We might also think that a singularity is a point that occurred suddenly in space. But Physicist has made us to know that before the big bang, nothing existed. Not even space and time. Therefore, it will be plausible to think that the singularity gave rise to space and time.

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Evidences supporting the theory

Why was the big bang theory regarded as the most plausible explanation of the universe? The reason is because it has a lot of evidences backing it.

First, galaxies have been found to be moving away from us according to Hubble’s law (speed is proportional to their distance). This supports the explanation that the universe was once compacted.

In 1965, Radio astronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which permeates the observable universe. This is thought to be a signature of the very hot universe before the eventual cooling to the temperature as we know it today just as the big bang suggested. Penzias and Wilson were awarded the 1978 Nobel Prize for Physics for this discovery.

Also, the abundance of light elements i.e. hydrogen and helium appear to support the big bang theory. These are some of the evidences that show to proof the efficacy of the theory.

Wait a minute, where is God in all this?

Science and theology believes that the universe has creation was a supernatural event. While the former tries to find evidences and interpolate back in time to resolve this mystery, the latter believes in a supernatural force that command things to be in just seven days. It might take more than the seven days to create the universe as science have suggested. Where is the unifying point between the big bang theory and what theology teaches? Did God create the singularity?

The question again is, will the universe continue to expand indefinitely or will eventually stop? If the first case holds, that means we might have no end to the universe. However, there have been many predictions in regards to the end of the universe. Various scenarios can play out and some are explained below.

The big crunch scenario

This scenario predicts that the universe will reach a maximum size and stop expanding. It will then begin to collapse in on itself all the way. What this mean is that gravity will slow down the expanding universe and will eventually bring it to halt. Then the reverse process will start to take place and everything will be crunched back to a singularity.

Heat death scenario

If the universe keep expanding indefinitely, the law of thermodynamics will play its part as well. As galaxies continues to drift apart, heat becomes evenly distributed throughout eventually resulting in a cold, dark boring mist.
This is because eventually, all the stars will wink out and there won’t be enough energy available to ignite new ones. The universe will eventually go dark and matter will bounce off each other without exchanging energy. the universe will be in a state of equilibrium. All that will be left will be particle and void.

In furtherance to the heat death scenario, another possibility is that black holes will devour most of the matter and the universe will become dark.

The big bounce scenario

This prediction is similar to the big crunch but a more positive one. Physicist doesn’t like this explanation so much. It predicts that when gravity eventually slows down the expanding universe, the universe will not go back to singularity. Instead, it will get close to singularity and then get repelled by a similar force to the one that started the big bang, so another big bang will occur. In the case, things are not really destroyed but recycled. A new universe will be formed.

The big rip scenario

The big rip takes its prediction in the suggestion that dark energy is responsible for the accelerating expansion of the universe. If that is the case, then the acceleration will eventually speed up such that the universe can’t take it anymore and it rips itself apart into emptiness.
This scenario seems like the apocalypse. It is estimated that this will happen in another 16 billion years. Unlike other scenario, at the time of the big rip, planets and indeed life will still be in existence.

Multiverse scenario

In a multiverse, our universe is just one out of many universes. Although any of the other scenarios may play out, the larger universes will still be there. Therefore since matter still exists in the other universe, there will still be existence. So if a universe runs out of time, there are still other universes in existence. According to the theory, the number of new universes being born is more than the old ones.

The eternal universe

Just as the name suggest, it predicts that the universe has been, and will continue to exist forever. It suggested that time had existed before the singularity that that started the big bang. Singularity could have been created by the collision of two branes (sheet like structures of space). In the eternal universe model, the universe is cyclic and will continue to expand forever.

Conclusion

Although the big bang theory remain the widely most acceptable theory of the formation of the universe, there has been various other scientist who feels it is not comprehensive enough. Some Scientist are still not convinced about what might have cause the inflation, even though it has been suggested to be dark energy. Therefore, there is still a lot of improvement on the theory daily.

References

Big Bang Theory
10 Theories On How The Universe Will End