How To Explain Dark Matter To A 5-Year-Old
Astronomers and scientists have always pondered the big questions. Are we alone in this universe? How is everything connected? What exactly makes up this universe that we don't understand yet? Recently, more and more have been asking this question: what is dark matter, and why are scientists looking for it? What is this whole idea of "dark flow" in our massive universe?
Imagine for a second that you're an Intergalactic School kid from the galaxy of Andromeda who just climbed aboard a Dark Flow Taxi with your best friend, on your way back to class at the Universal University of The Milky Way Galaxy. When you and your friend arrive, you discover the fare is more expensive than the previous trip, which was more costly than the one before it. At this point, you would certainly suspect that something was afoot, and rightly so. Your trip was actually taking longer each time because you were, in fact, traveling a greater distance. How could this be possible, since your points of departure and arrival have remained the same? The answer lies within the hidden world of dark matter in the universe.
Understanding dark matter and having dark energy explained can be a bit tricky since the world's foremost scientists aren't exactly sure what they are, and can only validate their existence by the influence they exert upon the Universe.
So how does dark matter work? What is dark energy? And why will your trip home to Andromeda take even longer than last time? Here is a list of reasons explaining what scientists know (so far) about dark energy and dark matter, and how they think it influences our universe and what it means for the future of humanity.
All Your Textbooks Are Wrong About What Makes Up The Universe
We have been taught in school that the universe and everything in it is made up of atoms. We learned about protons, neutrons, and electrons, and how they are the building blocks of all matter - but scientists have discovered that not everything in the universe was paying attention in class.
It turns out there is ten times as much not made of atoms as there is visible matter in our universe. Roughly 4.6% of our universe is made up of baryonic matter, which is what we think of when it comes to our friends protons, neutrons, and electrons. Scientists now believe that 23.3% of the cosmos is dark matter, and dark energy fills up the remaining 72.1%, though exact percentages fluctuate.
- Photo: NASA, N. Benitez (JHU), T. Broadhurst (Racah Institute of Physics/The Hebrew University), H. Ford (JHU), M. Clampin (STScI),G. Hartig (STScI), G. Illi / Wikimedia Commons / Public domain
96% Of The Universe Is Comprised Of Invisible Dark Matter And Dark Energy
When you look up at the night sky and see it twinkling with the light from billions of stars in our galaxy alone, it's not hard to imagine space being a little crowded, especially when you throw in all the other planets and comets and things floating around out there.
And then you find out that our Milky Way is only one galaxy in a universe filled with billions and billions of other galaxies out there, and every one of those galaxies is filled with planets and stars much the way ours is... you realize that the universe is a really big place. Just when you think we've seen what all lies within the universe, we discover that all the things we can see out there are just a tiny part of the cosmic picture. The other 96% of the Universe is filled with dark matter and dark energy.
What Exactly Is Dark Matter?
In Star Wars, it would be considered The Force which holds things together, but inside the world of science, it is proving a little more slippery to grasp. Dark matter doesn't behave the way scientists are used to seeing matter act. It doesn't give off light, and it doesn't reflect or absorb light.
Scientists have rounded up all the suspects in space to try figuring out which one is responsible for the dark matter, but so far none of them satisfy all of the requirements. From axions to black holes, none could account for the effect that dark matter has on gravity.
- Photo: ESO/L. Calçada / Wikimedia Commons / CC-BY 4.0
Dark Matter Holds Everything Together
Since dark matter has a massive gravitational effect, it affects everything in the universe. It is the gravity produced which caused all the material in space to clump together and form galaxies. These galaxies, in turn, would often clump together with other galaxies to form clusters of galaxies. After they were formed and began spinning around, it has been dark matter which keeps everything from being slung out into space.
Imagine having a tennis ball attached to a string, and you're spinning it around above your head. The ball is the galaxy, and you are the gravity. If the tennis ball were a bowling ball, your gravity would not keep it from breaking the string and flying off into space. Dark matter is what makes the string strong enough to hold everything in place.
- Photo: NASA Goddard / YouTube
Dark Matter Plus All Other Matter Still Isn't Half Of The Universe
So what else is out there to account for the rest of the universe? Dark energy! Dark energy makes up 68% to 72% of the entire universe. And while dark matter is busy acting as a cosmic magnet by being gravitationally attractive, dark energy is doing just the opposite, since it is gravitationally repulsive.
Painting with very broad strokes, what you have all together is pretty much a universe in which half of it is trying to hold everything together while the other half is trying to push it apart.
- Video: YouTube
What In The World Is Dark Energy?
The fact is, scientists don't know for sure what dark energy is. It's kind of like dark matter’s invisible evil twin, except that while dark matter creates an attractive gravity, dark energy is generating a repulsive gravity, or antigravity. This means dark energy is pushing things farther and farther apart, making the universe expand, much in the same way a balloon gets bigger when you blow air into it.