Across
1
Blocking of light by a celestial body
4
Center of an atom or cell
5
Particle of light
7
Compound containing oxygen
Down
2
Gas essential for breathing
3
Force that attracts objects together
4
Unit of force
6
Substance with pH below 7
8
Amplified beam of light
9
Push or pull on an object
10
Reddish electrical conductor
11
Mass per unit volume