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A laser pointer at 2 billion fps makes the speed of light look... kinda weird

AlphaPhoenix0 HN recommenders · 2025–2026
6M views · demo · evergreen · Uploaded 2025-10-17

AlphaPhoenix shows off a new camera that films at two billion frames per second and uses it to film a laser pointer pulse. He investigates a strange quirk in how the speed of light appears on camera.

Referenced in threads about the two-billion-fps camera and equivalent-time sampling as an example of filming light moving.

Everyday physics & science demosFundamental physics

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3 comments from Hacker News

@westurner2025 · in “Man Builds Two Billion FPS Camera That Records at the Speed of Light”

OT video: "A laser pointer at 2 billion fps makes the speed of light look... kinda weird" (2025; AlphaPhoenix) [VIDEO]

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@nomel2026 · in “From Oscilloscope to Wireshark: A UDP Story”

By definition, you can't interpolate a sample. A sample is a measured value. What you can do, if and only if you have an exactly repeating signal triggering at the same point within a cycle, is change the delay between the trigger and sample, and repeat. In other words, sample at different times within the same signal (since it's exactly repeating), to build up samples in time, of that waveform, to whatever time resolution you want. Of course, you're limited to any noise in the trigger, variation in the signal, etc. This is how you can record light moving through your garage [1]! [1] [VIDEO]

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@apt-get2026 · in “Using the railway network as a flatbed scanner”

Related - filming light at 2 billion fps with a somewhat similar setup in concept (at the single pixel scale): [VIDEO]

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