Big Bang Theory: Evolution of Our Universe

Illustration of the Big Bang Theory

How was our Universe created? How did it come to be the seemingly infinite place we know of today? And what will become of it, ages from now? These are the questions that have been puzzling philosophers and scholars since the beginning the time, and led to some pretty wild and interesting theories. Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding cosmos. This is known as The Big Bang Theory.

For almost a century, the term has been bandied about by scholars and non-scholars alike. This should come as no surprise, seeing as how it is the most accepted theory of our origins. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there of this, and what does the theory say about the long-term projections for our Universe?

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Oscillating Universe Theory

The Oscillating Universe Theory is a cosmological model that combines both the Big Bang and the Big Crunch as part of a cyclical event. That is, if this theory holds true, then the Universe in which we live in exists between a Big Bang and a Big Crunch.

In other words, our universe can be the first of a possible series of universes or it can be the nth universe in the series.

As we know, in the Big Bang Theory, the Universe is believed to be expanding from a very hot, very dense, and very small entity. In fact, if we extrapolate back to the moment of the Big Bang, we are able to reach a point of singularity characterized by infinitely high energy and density, as well as zero volume.

This description would only mean one thing – all the laws of physics will be thrown out of the window. This is understandably unacceptable to physicists. To make matters worse, some cosmologists even believe that the Universe will eventually reach a maximum point of expansion and that once this happens, it will then collapse into itself.

This will essentially lead to the same conditions as when we extrapolate back to the moment of the Big Bang. To remedy this dilemma, some scientists are proposing that perhaps the Universe will not reach the point of singularity after all.

Instead, because of repulsive forces brought about by quantum effects of gravity, the Universe will bounce back to an expanding one. An expansion (Big Bang) following a collapse (Big Crunch) such as this is aptly called a Big Bounce. The bounce marks the end of the previous universe and the beginning of the next.

The probability of a Big Bounce, or even a Big Crunch for that matter, is however becoming negligible. The most recent measurements of the CMBR or cosmic microwave background radiation shows that the Universe will continue on expanding and will most likely end in what is known as a Big Freeze or Heat Death.

CMBR readings are currently being gathered by a very accurate measuring device known as the WMAP or Wilkinson Microwave Anisotropy Probe. It is the same device that has measured with sharp precision the age of our universe. It is therefore highly unlikely that future findings will deviate largely from what has been discovered regarding the Universe’s expansion now.

There is however one mysterious entity whose deeper understanding of may change the possibilities. This entity, known as dark energy, is believed to be responsible for pushing the galaxies farther apart and subsequently the universe’s accelerated expansion. Unless its actual properties are very dissimilar from what it is showing now, we may have to shelve the Oscillating Universe Theory.

We’ve got a few articles that touch on the Oscillating Universe Theory here in Universe Today. Here are two of them:

Physics World also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:


Big Crunch

The Big Crunch is one of the scenarios predicted by scientists in which the Universe may end. Just like many others, it is based on Einstein’s Theory of General Relativity. That is, if the Big Bang describes how the Universe most possibly began, the Big Crunch describes how it will end as a consequence of that beginning.

It tells us that the Universe’s expansion, which is due to the Big Bang, will not continue forever. Instead, at a certain point in time, it will stop expanding and collapse into itself, pulling everything with it until it eventually turns into the biggest black hole ever. Well, we all know how everything is squeezed when in that hole. Hence the name Big Crunch.

For scientists to predict with certainty the possibility of a Big Crunch, they will have to determine certain properties of the Universe. One of them is its density. It is believed that if the density is larger than a certain value, known as the critical density, an eventual collapse is highly possible.

You see, initially, scientists believed that there were only two factors that greatly influenced this expansion: the gravitational force of attraction between all the galaxies (which is proportional to the density) and their outward momentum due to the Big Bang.

Now, just like any body that goes against gravity, e.g. when you throw something up, that body will eventually give in and come back down for as long as there is no other force pushing it up.

Thus, that the gravitational forces will win in the end, once seemed like a logical prediction. But that was until scientists discovered that the Universe was actually increasing its rate of expansion at regions farthest from us.

To explain this phenomena, scientists had to assume the presence of an unknown entity, which they dubbed ‘dark energy’. It is widely believed that this entity is pushing all galaxies farther apart. With dark energy, and what little is known about it, in the picture, there seems to be little room for the possibility of a Big Crunch.

Right now, measurements made by NASA’s Chandra X-ray observatory indicate that the strength of dark energy in the University is constant. Just for added information, an increasing dark energy strength would have supported the possibility of a Big Rip, another universe ending that predicted everything (including atoms) to be ripped apart.

Even with an unchanging dark energy strength, an ever expanding universe is still the most likely scenario. So unless data that contradicts these properties are collected, the Big Crunch will have to remain as a less favored theory.

Articles on the big crunch are so hot. It’s a good thing we’ve got a nice collection of them here in Universe Today. Here are two of them:

Here are links from NASA about the big crunch:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste: