I’m Dr. David Lawrence.
I’m a physicist at Jefferson Lab.
And I’m going to describe what matter is.
Matter is basically anything that has mass and takes up space… 
And excludes anything that's pure energy.
So everything is really matter.
It includes the screen you’re watching me on.
The keyboard you typed in this address on.
Your finger that you used to type the address with.
The stars out in the universe…
Everything else that has mass is matter.
