Across
1
Particle of light
4
Force that attracts objects together
5
Unit of force
10
Measure of matter in an object
11
Blocking of light by a celestial body
12
Positive particle in nucleus
Down
2
Absolute temperature scale unit
3
Unit of electric potential
6
Icy body with a tail near the sun
7
Nerve cell in the brain
8
Center of an atom or cell
9
Infectious microscopic agent