Do we really understand the universe or are we all just daydreaming?
The vastness and emptiness of the universe have been topics of scrutiny and pondering for many astronomers and physicists. Thousands of people have spent ages trying to pry open the secrets of the universe. But just like the bashful nymphs straight out of Greek mythology, the universe doesn’t open itself up completely. Rather it reveals its cards slowly one by one.
Think about it. We used to believe that Earth is stationary and everything around it is moving but then came Galileo. According to him the Earth wasn’t stationary at all but was revolving around the Sun (which by the way was also thought of as stationary). After him came Sir Albert Einstein, who completely revolutionized this dilemma by introducing relativity which incorporates both these ideas depending upon the frame of reference of the observer. And when we thought of applying these known concepts to the microworld, the entire story changed. We don’t even know where the particles are there at a precise point in time (courtesy of Schrödinger). But still, the secrets the universe beholds leaves everyone startled and amazed, personally giving me goosebumps.
One such card disclosed recently regarding this property of emptiness is that it is constantly increasing at an accelerating rate. This implies that the universe itself is expanding to account for increasing emptiness.
In the 1930s Edwin Hubble discovered that the universe is indeed drifting apart, creating more and more empty space. This was shocking for the whole astronomic society as they had previously assumed that the universe is contracting, courtesy of gravity. The fact presented by Hubble was then confirmed by various other scientists. The most famous among them were Saul Perlmutter, Adam Reiss, and Brian Schmidt. In around the 1990s and early 2000s they collected tons of data from Type 1A supernova and brightness of various celestial bodies and calculated what is known as The RedShift. This experiment proved something even more disturbing for the research community. The universe started to expand right after its formation. But the rate was constant for the first 7 billion years or so. After these years mysteriously, the rate of creation of the empty universe began to accelerate and to this date is accelerating. This anomaly left the scientists baffled. After a lot of research scientists concluded that some kind of powerful energy is responsible for this behavior of our universe.
This energy is named DARK ENERGY. It is named so because no one knew what it was or how is it formed, just knew that it is there. Interestingly dark energy accounts for 74% of our Universe whereas Dark matter and observable matter (i.e., Stars, Planets, you, me, etc.) combined accounts for only 26%. Even though it is present in huge abundance, we came to know about it recently. This is so far the strongest energy discovered and it keeps getting stronger as the universe expands. And since it is present in the empty space of the universe, it means that empty space has more energy than everything else in the universe combined. Exciting isn’t it!
As the universe expands, its properties don’t change. There is just more space created wherever there is a void. As space is created, more dark energy is created along with it. Surprisingly, this creation of energy out of nowhere doesn’t violate the Theorem of Conservation of Energy. This is so because as there is an increase in dark energy, the universe still expands, thus its gravitational negative potential energy also increases balancing the formation of dark energy.
But then why don’t we see it happening in our daily lives? This is because gravitational forces tend to dominate inside the galaxies and solar systems due to relatively close proximity of the planets, stars, and moons. Whereas in the universe beyond galaxies, which is mostly empty, this effect is detectable by measuring the data from The Redshift experiments.
As it’s in the very nature of a scientist to make some sort of meaning out of these observations, there had been several attempts to understand this energy. Some of them are: -
1. It is thought that this energy is a property of Empty Space and has a close relation with Einstein’s Equation.
It means that empty space or void space of the universe is nothing as preserved but has its own energy that constantly expands itself thus expanding the empty space along with it, the entire universe.
This concept was supported by one famous equation of General Relativity given by Einstein. The cosmological constant (represented by lambda) was introduced to counter the force of gravity thus making the universe static. But after Hubble’s discovery, scientists tried to give this constant an entirely new definition. It was made equal to the energy density of empty space due to imperfect collision during quantum fluctuation. In simple terms, it means that Vacuum Energy (or dark energy) is created due to irregularities during the annihilation of matter along with its anti-matter counterpart.
But when the theoretical values were matched with the observed ones, there was a difference in magnitude of around 10¹². Thus, this theory was disbanded. But it is to date the closest theoretical explanation of dark energy.
2. The Theory of Quintessence.
This is a relatively new theory. According to this, dark energy is thought of having an entirely new energy field that is dynamic, which means it can change shape, size, and magnitude with time, but is repulsive. This field is termed as Quintessence, which if proved, may become the 5th fundamental force the other being –
· Electro Magnetism
· Weak Nuclear Interaction
· Strong Nuclear Interaction.
Also, scientists have suggested a new particle named Higgs Boson, maybe the essential building blocks of this new field. These particles are responsible for the creation of more dark energy. There have been several attempts and experiments to find the existence of Quintessence, but none have provided us with compelling results.
3. Maybe all of us are wrong.
There are many scientists that believe the fact that maybe we all are contracting rather than the universe expanding itself. Which implies that there is no dark energy at all. But then what does the observation of Hubble, Perlmutter, etc. indicate? Although the chances of this happening are estimated to be negligible, but who knows! The Search Still Continues…