Our Universe - 1

If you are a regular reader of this blog, you will know that I personally like space-science a lot. Many of my previous posts are about many entities that play a major role in our universe like time, gravity and atoms.

Today, I’d like to talk about a very broad, general and debatable concept, our universe. What is our universe made up of? How old is it? Does it have a beginning? When will it end? How big is it? Most of us generally think that we know the answer to these questions. But science is really mysterious and so is our universe!

Let’s start with how our universe was born. You must be familiar with the Big Bang theory. It’s widely accepted but it has many loopholes. While we assume that the universe started from the Big Bang, reality is unknown.
The Big Bang is a theory based on our present-day observations of motion of distant stars and galaxies with respect to our own. A very famous scientist ‘Edwin Hubble’ discovered that galaxies, stars and everything in this universe is moving away from us at an accelerating rate. How did he get to know this? It is something called as the Doppler effect.

When 2 objects emitting waves move with respect to one another, there is a shift in frequency of the resulting wave to the subject. This phenomenon is called as Doppler effect and can be widely experienced through sound waves. When it comes to light, the same effect can be observed. In this case however, the frequency of light is measured by the change in colours emitted. If an object emitting light moves far away from us, we see it emitting red colour as the wavelength is pulled longer. The relation to the universe here is, every single cosmic entity viewed from Earth gives a red-shift, meaning that everything is moving away from us.

So how does this relate to the Big Bang? Just rewind! If everything is moving away from everything, then it all must’ve started from a single point. An infinitely dense particle which started expanding and gave rise to our wonderful universe!

This all seems well explained right? ...Wrong.
Many questions like What was around the infinitely dense point? What made the point explode? Where did that come from? arise.

While Big Bang is derived from one of the observed phenomena, the age of the universe itself is found from the theory. The age of the universe is approximately 13.77 billion years (give or take 59 million years). This age is calculated by measuring the distances and radial velocities of other galaxies, most of which are flying away from our own at speeds proportional to their distances. Using the current expansion rate of the universe, we can imagine rewinding the universe to the point where everything was contained in a singularity, and calculate how much time must have passed between that moment (the Big Bang) and the present.

According to the Big Bang, our universe had a beginning. But the Big Bang isn’t the only theory. Implications found in quantum gravity and string theory tantalizingly suggest a universe that is in reality nothing like how it appears to human observers. It may actually be a flat hologram projected onto the surface of a sphere, for example. Or it could be a completely digital simulation running in a vast computer (Yes! Matrix!).

Irrespective of the beginning, the fact that the universe is expanding is true. But at what rate? There must be a constant speed at which it is expanding. It does have a speed, but it is not a constant. The rate of expansion increases by 67 kilometres per second per million parsecs. One parsec is approximately 3.086×10^13 kilometres. If you consider an object as far as one million parsecs, that cosmic body is increasing its velocity by 67 kilometres every single second! That is the rate of expansion!

The galaxies and stars are not simply accelerating away from us. The universe is expanding along with them. Take a raisin-dough model for example. The dough inflates when heated. The raisins on the dough don’t move apart individually. They move with the dough. This is similar to the universe on a larger scale. The stars and galaxies and every other object keep moving along with the universe.

The Big Bang might not be accurate but it is widely accepted as it answers most of the questions. However, this should not limit our thinking. Theories like this are the biggest inspirations to infinite imagination of possibilities. Who knows what the actual past is?

Considering the big bang as the base, I talked about the birth, expansion and age of the universe. There is a lot more to our universe and its mysteries which I’d like to talk about in the next part of this post.

So stay tuned for the next version of ‘Our Universe’ where I plan to talk about the constituents of the universe, the timeline and the end of the universe itself!

-Sameer V Devipur