Why does matter take up space?

Answer 1

Matter takes up space because it exists. It takes up space because it has depth. If it didn't take up space it would be a 2D object and nothing could be made of matter. Because everything is made up of matter, matter must take up space.

Answer 2

Matter occupies space because of the Pauli Exclusion Principle and because of electrostatic interactions.

I'm generalizing, but the Pauli Exclusion Principle basically says that we can never have any two identical particles (say, atoms in a piece of iron) in the same position at the same time. So, in order to satisfy this principle, they spread out so they don't tread on each others territory.

Also, atoms are composed of negatively charged electrons surrounding positively charged protons in the nucleus. When you try to push two atoms together, their nuclei will repel each other due to the electrostatic force (+ and + repel). Also, their electrons will repel in a more complicated way. This also prevents atoms from getting too close to each other.

These two things put together explain why you can't put your hand through a solid wall.

One last thing - Check this out the Bose Einstein Condensates. If you cool atoms down to near absolute zero, and are very careful, you can get millions of atoms to occupy the same space at the same time!

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