Why is matter visible?

Question

If matter is mostly empty space, then why isn't it transparent?

Answer 1

Quantum mechanically matter is not empty space exactly. it is devoid of much mass. But not devoid of electric charge. There is electron density pervading matter in and out. Which in certain cases absorbs or reflect light which is an electromagnetic wave.

Of course some matter is transparent too . Where there is minimum interaction possible between the electron density and e m waves in the visible range.

Answer 2

What about this; light has no mass, being a form of energy. How come light isn't invisible? Its even more than 'mostly empty space'!

Answer 3

Matter interacts with electromagnetic waves (light), thus is visible.