The Importance of Size in the Universe

The extent of the electromagnetic force is infinite. You're being constantly poked by everything in the universe. The size of something depends on not just what you poke it with, but how hard you poke it. If you poke an atom very gently, it'll seem bigger because you'll notice smaller deflections further away. But if you poke it very hard, it will actually seem smaller because you overpower the electrons on the outside and only see the nucleus on the inside.