Putting Dark Energy in the Spotlight


The universe is expanding. In fact, this was first determined 87 years ago by the famous astronomer, Edwin Hubble. Hubble proposed that the speed at which an object is receding is proportional to its distance from Earth with the formula v = Hod. Astronomers began to piece together the evolution of our universe from the time of the Big Bang and thought they were close to understanding where the universe is ultimately going as well.

Since the Big Bang was essentially a giant explosion, it made sense to assume it followed a standard model of any explosion: that at some point, the total energy of the pieces would dissipate, and thus, come to a stop.

However, astronomers began to note some really weird things happening the farther away they observed. Hubble’s Law predicted that extremely distant objects would recede faster than closer objects, and the evidence concluded that this is the case –albeit much faster than expected. In other words, the universe isn’t just expanding, it’s accelerating!

Now of course, the natural question is why? Why is the universe not slowing down, as predicted? And what could possibly account for this strange result?

It appears that there is some unknown force at work here, some anti-gravity that pushes everything perpetually outwards instead of pulling it in. In order to have such immense effects on something as large as our entire universe…well there must be an awful lot of this strange entity.

Everything that exists in our universe from radiation to matter (also including dark matter!) is only responsible for 20 – 40% of the density of the universe! The rest must therefore be this unknown force that is so plentiful. To make it even more interesting, it is also something that cannot be detected (yet). This mysterious entity that accounts for the remaining density of the universe is what astronomers have labelled ‘dark energy’.

The elusiveness of dark energy stems from its apparent nature. If it were a form of radiation, astronomers could use detectors aboard orbiting satellites to pick up traces of its existence, but so far this has not been the case. Similarly, dark energy seemingly has no identifiable gravitational effects that can be detected. (This is a method used to detect dark matter.)

Whether we can detect it or not, the data shows that dark energy definitely exists. If anything, it could be said that dark energy is more prominent now than it was in the past. As the universe expands, the density of matter and radiation both decrease, but the density of dark matter has stayed the same. This means that we live in what is called a ‘dark energy dominated universe’.

It’s interesting to think that despite all we know, the majority of the universe remains a mystery to us. But I imagine it won’t be long before new evidence emerges for understanding dark energy and its role in the universe.

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