Welcome back!

I hope you are all safe and doing well.

This is a momentous occasion. This blog post makes 1 year of blogging!!! I cannot express in words how excited I am to have reached this milestone; it’s been a tremendous journey and I’ve enjoyed every bit of it. And I couldn’t have done it without your support! It means the world to me to see so many people caring about what I write. I hope that I’ve been able to make your days better一and maybe a little more stellar!一with this blog.

We have almost literally traveled throughout space, exploring everything from fascinating interstellar objects such as nebulae to even the most mundane backyard telescopes. In this following year, I hope to expand our interstellar horizons even further, maybe even touch on the tip of theoretical physics…

But let that be a teaser for the future.

As for today, we will be continuing the conversation we began the last about dark matter. Today, we’ll be discussing dark matter’s dark and mysterious companion: dark energy. Compared to the knowledge that scientists know about dark energy, our knowledge of dark matter is magnitudes greater一that’s how mysterious it is.

In this blog post, I will aim to explore the facets of dark energy. What is it, even; can we even really tell? How did we even find out about it? Was a mistake of Einstein proportions regarding dark energy, not a mistake at all?

All in good time! So sit back, relax, and enjoy our foray into the (rhetorically) illuminating world of dark energy.

Albert Einstein’s main claim to fame一and believe me, he has many; you can read about them on my website in the History of Astronomy section一is that he was able to essentially develop an equation that described the ENTIRE universe.

Take a minute to comprehend that.

A mathematical expression that described the ENTIRE cosmos.

Of course, a feat this mammoth of proportions had to be perfect. It had to be an unimpeachable model of the world. It couldn’t even have a single flaw.

Unfortunately for Einstein一in his eyes at least一there was a flaw.

In order to understand this, let us take a look at the equation that Einstein created:What Is Einstein's Cosmological Constant and How Does It Affect the  Expansion of the Universe? - Owlcation - Education

Equation Credit: Albert Einstein, Image Credit: Owlcation

Now, this looks super complicated, and don’t worry, you really don’t need to understand the whole thing right now. What you should take a look at is the highlighted Greek letter lambda (𝚲). This was an interesting quirk of the equation. Einstein called it the “cosmological constant”. But what was its role? It was essentially the only thing that made the equation work; without it, the universe that the equation predicted would collapse upon itself. Quite a large problem if you’re trying to develop an accurate equation to describe our very non-collapsed universe.

The issue, essentially, was gravity. Gravity is an attractive force; objects under the force of gravity fall towards its source. During Einstein’s early period, scientists did not yet believe that the universe was expanding, meaning the amount of gravity in the universe would (under their understanding) cause the universe to collapse upon itself.

But, of course, as they were all alive, this wasn’t true. And, therefore, Einstein added a “cosmological constant” in order to balance out this inevitable crunch.

Einstein, of course, hated this constant. 

Now, you may be saying to yourself, “Well, Pranet, that’s really interesting, but what does any of this have to do with dark energy?” And my response? Just hang in there. This is where it gets interesting.

In 1929, an astronomer named Edwin Hubble (you may have heard of the eponymous telescope) discovered that several galaxies far away from Earth were moving away from the Earth. His conclusion? The universe was expanding!

Einstein was pleased with this, as it meant that he didn’t need his cosmological constant; if the universe was expanding, it wasn’t possible for it to collapse on itself! And so, the poor little 𝚲 sat in a dusty corner for decades, believed by Einstein to be one of his single greatest errors.

Now, you might think that’s the end of the story. Einstein had a cosmological constant, it was invalidated by expansion. But wait, there’s more!

In the 1980s astronomers observing the expansion of supernovae observed something interesting. Instead of the rate of expansion being constant (as logic would dictate) it seemed to be accelerating.

Suddenly, Einstein’s old equations were dusted off, and the cosmological constant was brought back from its corner. Suddenly, the explanation for the acceleration had been一scientists realized一right in front of them the whole time. Suddenly, a new force was on the horizon: dark energy.

Dark energy is, essentially, just a force that is causing the expansion of the universe to accelerate. The universe, being propelled by this strange quantity, is growing larger at ever-increasing speeds.

Scientists have done studies with incredible technologies to map out the composition of the universe, and these are the results. You’ve already seen this graph in the post for dark matter, so let’s take a look at it again,

 GMS: Content of the Universe Pie Chart

Credit: NASA

Now, we know what this enormous portion called “dark energy” really is! A super mysterious force that makes the universe expand at ever-greater velocities一oh, and something that takes up 70% of the mass-energy ratio in the universe.

Congratulations! You now have the same general understanding of dark energy as the majority of the astronomy community.

Now, you may ask, what is the future?

Well, I am sad to share that attempts to directly observe the dark energy were unsuccessful. But who knows? One day you may be able to actually discover what dark energy is, what it’s made of, maybe even if it can be harnessed for our benefit. That would be the defining scientific discovery of the era.

I hope you all learned something new (and enjoyed this post!) Once again, I cannot thank you all enough for your incessant support through this whole process; my blog would not have been possible without everything that you all do. I tip my hat to y’all.

Clear skies!