Zias and B.Lou's Sound Faster Than Light Test refers to a series of memes based on a viral video clip of streamers Zias and B.Lou testing whether sound or light is faster by turning on a phone flashlight at the same time as making an "Ah" noise to see which one is faster.
The clip originates from a stream on March 22nd, 2025, which went viral on TikTok that year. In September 2026, the clip experienced a resurgence in virality and inspired a series of video edits and memes on TikTok and Instagram Reels, which ironically refer to the two as great scientists.