system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why does roast beef sometimes have shiny rainbow colors in it?
gpt
When light hits a slice of meat, it splits into colors like a rainbow. This is something called a "diffraction grating," essentially what happens when light waves bend or spread around a slightly pitted surface and create a pattern. It's the same thing that happens to make rainbows on the surface of a DVD.  It is somewhat unique to roast beef meat because the sliced muscle fibers are the right size.