Across
1
Amplified beam of light
5
Curved glass that refracts light
6
Force that attracts objects together
8
Blocking of light by a celestial body
Down
2
Absolute temperature scale unit
3
Our home planet
4
Infectious microscopic agent
7
Reddish electrical conductor
9
Mass per unit volume
10
Group of similar cells
11
Basic unit of life
12
Second lightest element