What We Cannot See
Look up at the night sky. You can see twinkly stars — but scientists say most of the universe is made of something you can NEVER see, no matter how big your telescope is! It is called dark matter, and even though it is invisible, we know it is there because of how it pushes and pulls on things we CAN see.
What You'll Learn
- Why scientists believe invisible stuff called dark matter exists - How we can 'see' something's effects even when we cannot see the thing itself - One simple example of an invisible force you already know
An Invisible Push You Already Know
Have you ever felt wind on your face? You cannot see wind, but you can see leaves blowing and feel your hair move. That is how scientists first noticed dark matter: they could not see it, but they saw stars in faraway galaxies spinning around much faster than they should — as if something invisible and heavy was pulling on them, like extra wind pushing the leaves.
Galaxies Spin a Special Way
A galaxy is a giant swirl of billions of stars, like our own Milky Way galaxy. Scientists like Vera Rubin, an astronomer who studied galaxies in the 1970s, measured how fast stars at the edges of galaxies were spinning. The outer stars were moving almost as fast as stars near the center — that should not happen unless there was a lot of extra invisible material holding the galaxy together with its pull.
Vera Rubin was an American astronomer who carefully measured galaxy spins and helped convince other scientists that dark matter is real. A giant telescope in Chile, the Vera C. Rubin Observatory, is named after her.
Flashcards — click each card to reveal the answer
Why do scientists believe dark matter exists even though no one has ever seen it?
What did astronomer Vera Rubin study that helped show dark matter is real?
Invisible Force Hunt
With a grown-up, find three examples of invisible forces or things at home or outside (examples: wind moving a flag, a magnet pulling a paperclip without touching it, gravity making a ball fall). Draw a picture of each example and write one sentence explaining how you know the invisible force is there, even though you cannot see it.
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