system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come when you squint at a bright light, light beams seem to appear on the top and bottom of the source?
gpt
What you are seeing is the diffraction of light through your eyelashes. As light passes by the barrier of your lashes the light is bent and the sum total of this interaction is the light "beams" you describe, actually called "diffraction spikes".