AI Summary
5 min readThe Scale of the Universe
A user named Burrow on the podcast's subreddit took a fact the hosts had mentioned in an earlier episode—that human cells sit exactly halfway between the smallest possible size and the largest possible size—and turned it into a thought experiment so vivid that Michael Stevens called it "one of the best things I've ever seen." The game works like this: you start at the Planck length, the smallest size physics can describe, and your friend starts at the size of the observable universe. Every second, you get ten times bigger while your friend gets ten times smaller. You keep going until you meet in the middle.
The lopsided journey to the middle
For the first ten seconds, you are lonely. There is almost nothing between the Planck length and a neutrino—vast empty stretches of scale where no known matter exists. Meanwhile, your friend, shrinking by a factor of ten each second, passes superclusters like Laniakea, local groups of galaxies, the Milky Way, and Andromeda. After ten seconds, you are as large as a neutrino (2.8 yoctometers across), and your friend is the size of the Ring Nebula (1.3 light-years across). Already the asymmetry is striking: the small side of the universe is mostly empty, while the large side is rich with structure.
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What you'll learn
- 1 (00:00) **Introduction: The Human Cell as Cosmic Midpoint** - Hannah Fry and Michael Stevens introduce the episode's central idea: the human egg cell sits exactly at the midpoint between the smallest known scale (Planck length) and the largest (observable universe).
- 2 (01:15) **The Thought Experiment: Shrinking and Growing Together** - Michael describes a game where you start at the Planck length and your friend starts as the observable universe, each changing size by a factor of 10 every second until you meet in the middle.
- 3 (02:31) **First 10 Seconds: Extreme Loneliness vs. Cosmic Grandeur** - For the first 10 seconds, you see almost nothing (from Planck length to a neutrino), while your friend passes massive structures like superclusters, galaxies, and nebulas.
- 4 (03:29) **Ad Break (Cancer Research UK, Sally, Google Chrome)**
- 5 (05:42) **The Lopsided Journey and the Midpoint Revealed** - The game feels unbalanced: your friend has much more to see. The midpoint is the human egg cell, which is also exactly between a neutrino and the Ring Nebula, and between a proton and the Moon.
- 6 (07:17) **Seconds 17-26: From Cork to Stegosaurus** - A rapid-fire sequence of comparisons: at 17 seconds you're a cork (friend is Earth's orbital diameter); at 20 seconds you're a proton (friend is Moon-sized); at 24 seconds you're an oxygen atom (friend is the Great Pyramid); at 26 seconds you're a DNA molecule (friend is a Stegosaurus).
- 7 (09:27) **Seconds 28-30: Virus, White Blood Cell, and a Grain of Sand** - At 28 seconds you're the width of COVID-19 virus (friend is a banana); at 30 seconds you're a white blood cell (friend is a grain of sand). You are still too small for color to exist.
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Guests on this episode
Show Notes
The scale of the universe stretches from the Planck length, the smallest scale physics can describe, to the observable universe, the largest thing we can see.
Travel inward from one and outward from the other by powers of ten and they meet at something astonishingly familiar: the size of a human egg cell.
Michael Stevens (VSauce) takes Professor Hannah Fry on a journey through powers of ten, from quarks and protons and DNA to bananas and pyramids and on to planets and galaxies, to explore where we sit in the scale of the universe.
Along the way they ask whether the Planck length could be the universe's smallest pixel, whether reality might be a computer simulation and just how empty space really is.
Plus, your questions: why our best ideas arrive in the shower, Wikipedia's strangest rabbit holes and Hannah corrects the record on whether Saint Augustine and Thomas Aquinas believed curiosity was a sin.
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You can find the Reddit thread for scale of the universe here: https://www.reddit.com/r/TheRestIsScience/comments/1uycf3l/i_visualized_michael_scale_comparison_from_the
And The Power Of 10 documentary here: https://www.youtube.com/watch?v=0fKBhvDjuy0
See some of Hannah & Michael's favourite Wikipedia pages here:
- Osama Bin Laden The Elephant - https://en.wikipedia.org/wiki/Osama_bin_Laden_(elephant)
- Death From Laughter - https://en.wikipedia.org/wiki/Death_from_laughter
- Order Of Magnitude - https://en.wikipedia.org/wiki/Order_of_magnitude
- Amedeo Avogadro - https://en.wikipedia.org/wiki/Amedeo_Avogadro
- Guy Standing (Economist) - https://en.wikipedia.org/wiki/Guy_Standing_(economist)
-Guy Standing (Actor) - https://en.wikipedia.org/wiki/Guy_Standing_(actor)
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