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Admiral Grace Hopper Explains the Nanosecond

funbury · lecture · Watch on YouTube

History of computingComputer architecture & CPUsTech pioneers & interviews

What it is

Admiral Grace Hopper holds up a length of wire to show how far light travels in a nanosecond, about 11.8 inches. She explains how she made the idea concrete to people who could not picture a billionth of a second.

Why Hacker News recommends it

HN uses it to illustrate physical latency limits and why performance and distance matter in computing.

  • 5 people recommended it
  • 5 different months
  • 1 strong recommendations
  • first 2020, last 2025

What HN commenters said

  1. “For me it changed my mind on wasting time on less efficient algorithms.”

    Makes the cost of inefficiency tangible

    dmoreno, 2023-01 · Strong recommendation · in “Ask HN: What's your favorite illustration in Computer Science?”

  2. “Learn from Admiral Grace Hopper”

    Grace Hopper shows how far light travels in a nanosecond

    dougmwne, 2020-01 · Recommendation · in “A low-mass planet candidate orbiting Proxima Centauri”

  3. “For those that haven't seen it”

    The famous nanosecond wire demonstration

    lozf, 2020-04 · Recommendation · in “Captain Grace M. Hopper: The Mother of COBOL (1981)”

  4. “the industry has collectively decided that Grace Hopper is an old codger who doesn't need to be listened to.”

    Hopper's lesson on caring about performance

    klyrs, 2021-06 · Recommendation · in “Your CPU may have slowed down on Wednesday”

  5. “Admiral Grace Hopper Explains the Nanosecond" is a good illustration of this (segment is only 2m)”

    Two-minute segment illustrating how long a nanosecond is

    throw0101a, 2021-12 · Recommendation · in “I bought 1000 meters of wire to settle a physics debate [video]”

Excerpts from Hacker News comments, linked to the originals. Summaries and labels were written by a language model from those comments.

Topics: grace hopper, nanosecond, latency, speed of light, performance

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