He then pumped the air out of the sphere, forming a vacuum. A perfect vacuum contains nothing, not even a single atom. So the hollow sphere was most likely not a perfect vacuum, but it was very close to empty, which made it a partial vacuum. There was very little air inside the sphere to push the bowls apart, and the greater push of the air on the outside held the bowls together. Try as they might, the horses were not able to pull the bowls apart.
Air pressure is very strong.
It does not crush our bodies because our bodies push back with an equal force. Don't miss Janice VanCleave's new book Science Around the Year .