system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why is snow white?

Water is transparent. Ice is a bit transparent. When you grind ice it gives very small white ice. Snow is very white why is that?
gpt
Millions and millions of reflections and refractions breaking up the light. 

Stand in front of a glass window and although you mostly can see through it there will be a fainter reflected image of you. That's just one air to glass transition for the light. Smash up the glass into cubes like a broken windscreen and you get multiple reflections as the light bounces around. Grind it up and the number of reflecting surface multiplies hugely. Snow, fog, foam, salt and many other things look white from that effect even though the material is transparent in bulk.