The Universe is so vast and full of mysteries we are yet to solve. Dark matter and energy are the biggest of them all, and if they are fully understood; they can open a whole new chapter in our book of knowledge! A lot of you may have heard of Dark Matter and Dark Energy, but do you know what they actually are?
The gap in the puzzle of Space
Everything you can directly observe in the entire Universe; from your own hands, to all the Stars in the night sky… accounts for just 5% of the total mass of the Universe . Yes, 5%. In fact, astronomers have repeatedly weighed galaxies over and over again, reproducing ridiculous results suggesting everything we know… is nothing. Dark Matter and Dark Energy are assigned to this 95%.
• Matter we can directly observe: 5%
• Dark Matter: 27%
• Dark Energy: 68%
Why can’t we see this matter?
If you are thinking how you can possibly not be able to see a physical ‘thing’ – I don’t blame you. See to answer this question, we must understand why we can see ‘things’ in the first place. Let’s take a banana as an example. The reason we see a banana is because light, and the atoms making up that banana interact. I’m not going to go into much detail about how they interact, but this interaction is what determines the objects physical appearance, i.e. colour (yellow).
This means that Dark Matter must be made up from a new exotic particle, which does not interact with light of any form – meaning it would be impossible to directly observe them. We now know why we cannot see it, but what is its importance?
Did you know that every object has gravity? The greater the mass of an object the stronger its gravitational strength – this is why we can feel the pull of Earth but not the pull of a banana, for example. Why is this related? Well, when the masses of different galaxies in our Universe are measured, we see that there is a lot more mass than the masses of all the objects we can directly observe, combined . In fact, if these galaxies didn’t have this extra weight (Dark Matter), gravity would be too weak to hold them in place and the Stars would just drift away into Space.
Dark Matter only interacts through gravity meaning there is absolutely no way of physically touching or detecting it (as it does not interact electrostatically which is what allows us to feel things) – it would just pass through regular matter, unaffected . Since it interacts through gravity, we can see its effects in the Universe, specifically on galaxies and stars. In conclusion, we know that:
• Something does exist
• There is a lot of this something
• This something interacts with gravity
Dark Energy is a lot weirder than Dark Matter. In fact, we do not know what Dark Energy is. Remember when I mentioned the heavier something is the stronger its gravity? It was traditionally thought that due to this gravity, the Universe would slowly stop expanding and begin to collapse in on itself – but recent studies have shown that the Universe is not only still expanding… but this expansion is accelerating.
See, the closer ‘stuff’ are, the stronger the gravity – but as the theory goes; the further away ‘stuff’ is, the stronger the force of Dark Energy, thus explaining the acceleration of the expansion of the Universe . You may ask yourself, why don’t we expand too? Galaxies are tightly held together by the force of Gravity which overcomes this Dark Energy force – meaning all that is affected, is the empty space… in Space. This means that by the second there is more and more space.
Here’s a fun fact for you; if you shot a gun in Space, the bullet would travel forever. This is because the expansion rate of Space is faster than the speed of a bullet.
Just to think that empty space has a lot more energy than everything else in the Universe…combined, is a baffling thought. What we call ‘normal matter’ is 5% of the matter that is actually there so does that still mean this normal matter… is normal?
We know so much, yet we know so little and it is only a matter of time before we understand what we never thought we would ever have to.
Here is a very well ‘put together’ video for you that goes into a little bit more detail in case you are interested!
If you have any questions, leave them below and until next time, take care.
 – https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy
 – https://www.space.com/20930-dark-matter.html
 – http://www.cfhtlens.org/public/what-dark-matter
 – http://hubblesite.org/hubble_discoveries
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