The Universe's Invisible Glue and Push

Blow up a balloon and let it go. It zooms across the room! Something you cannot see — the air inside — pushed it. Way out in space, there are two invisible things doing something similar, but billions of times bigger. Scientists call them dark matter and dark energy, and even though nobody has ever seen them, we know they are there because of what they DO.

- What dark matter is and why scientists think it exists - What dark energy is and how it pushes the universe apart - Why 'dark' does not mean 'scary' — it means 'we cannot see it yet' - How galaxies act like spinning balloons held together by invisible glue

Galaxies are huge spinning groups of stars, like a merry-go-round with billions of lights on it. Scientists noticed something strange: galaxies spin so fast that the stars on the outside should fly off into space, the same way you fly off a merry-go-round that spins too fast if you are not holding on tight. But the stars do NOT fly off. Something invisible is holding them in place, like extra glue we cannot see. Scientists named this invisible glue dark matter. We cannot see it, touch it, or catch it in a jar, but we can see its GLUE-like effect on the stars.

Now imagine a different balloon: one that keeps getting bigger and bigger, forever, all by itself. That is kind of like our whole universe! Scientists measured the distance between galaxies over many years and found something amazing: galaxies are moving FARTHER apart, and they are speeding up as they go. Something invisible is pushing everything apart, like a fan blowing up the biggest balloon ever. Scientists named this push dark energy. It is the biggest push in the whole universe, and it is working on everything, everywhere, right now.

Dark matter PULLS things together, like glue holding stars in a galaxy. Dark energy PUSHES things apart, like air blowing up a balloon bigger and bigger. Our universe has both happening at the same time!