You can't see light. When it's dark, in a vacuum, if a person shines a beam of light straight across your eyes, you won't see it. Slightly technical, some physicists will disagree with this.
光は見えません　真空の暗闇で 光を目に当てても 見ることはできません ちょっと専門的で 同意しない物理学者もいますが―