🎧 Listen: Mag Cosmos podcast episode
Mag Distance/Size
Space
“Length” and “size” and “distance” all measure the same physical dimension, but they are subtly different:
- “length” refers to a span across space
- “size” refers to the largest spatial dimension of an object
- “distance” refers to how far away something is from something else (center to center)
Diameter is used for size, because it is closest in spirit to “length”. For a cube-like solid, the size is just the magnitude of the longest side. (The diagonal of a cube would be ↑0.2 longer, so it generally won’t make a difference.)
Translating from mag diameter to another mag quantity uses simple logarithmetic. To convert to:
- radius: ↑-0.3 size
- circumference: ↑0.5 size
- surface area: 2 x size
- volume: 3 x size
For example, Earth is “↑7 size” and to walk all the way around it would be “↑7.5 distance”. And it has “↑14 surface area” and “↑21 volume”.
The Moon, Earth, Jupiter, and Sun are ↑6.5, ↑7, ↑8, and ↑9 size, respectively. The distance to the Sun (1 AU) is ↑11, and the distance to Voyager is ↑13.
How far is the Moon? We know that it takes seconds (↑0 time) to radio the Moon, and since the speed of radio is the speed of light at ↑8.5, so the Moon is ↑8.5 distance from Earth.
Conversions
- ↑-10: ångström
- ↑3: mile; kilometer
- ↑11: Astronomical Unit (AU, distance from Earth to Sun)
- ↑16: light-year (↑8.5 speed of light + ↑7.5 year)
Mag Size
- ↑-10 (1 ångström): Hydrogen atom
- ↑-9 (nm): width of DNA; width of nanotube
- ↑-8: cell wall
- ↑-7: HIV
- ↑-6 (µm): bacterium
- ↑-5: red blood cell; width of human hair
- ↑-4: water bear
- ↑-3: flea
- ↑-2: coin
- ↑-1: banana
- ↑0: family home
- ↑1: large building (school)
- ↑2: huge building
- ↑3: Three Gorges Dam; smallest moons and asteroids
- ↑4: city; asteroids
- ↑5: state or minor country or minor moon; largest asteroids
- ↑6: the US; the Moon
- ↑7: Earth
- ↑8: gas giant: Jupiter
- ↑9: star: Sun
- ↑13: Kuiper Belt
- ↑21: Milky Way Galaxy
- ↑24: Virgo Supercluster
- ↑27: Universe
Mag Distance
How far away are things?
- ↑0: across the hall
- ↑1: across the street
- ↑2: a few blocks
- ↑3 (1km): walkable
- ↑4 (10km): bike trip; hike trip (farsang, Scadinavian mil)
- ↑4.5: marathon
- ↑5 (100km): car trip; helicopter trip
- ↑6 (1000km): train trip; plane trip
- ↑7: overseas
- ↑7.5: around the world
- ↑8: to the Moon
- ↑10 or ↑11: to Mars
- ↑11: to the Sun (1 AU)
- ↑12: to Pluto
- ↑13.5: to Voyager 1
- ↑16.5: to Alpha Centauri
For a much bigger list, see Orders of magnitude (length) on Wikipedia.
Mag Speed
Speed is distance over time (m/s), which makes it a half-mag (compressed) scale:
- ↑-10: continental drift
- ↑-8: slow glacier
- ↑-5: glacial pace
- ↑-3.5: fastest-moving glacier
- ↑-3: snail’s pace
- ↑-1: sloth (top speed)
- ↑0: walking; swimming
- ↑0.7: running; biking
- ↑1: road-race cycling
- ↑1.1: Usain Bolt world record for running
- ↑1.5: car on highway
- ↑2: high-speed train; racecar
- ↑2.5: speed of sound; bullet; jet
- ↑3: escape velocity from Moon; missiles; thermal neutrons
- ↑4: escape velocity from Earth
- ↑4.5: speed of Earth around Sun
- ↑5: speed of Solar system around galaxy
- ↑6: escape velocity from Milky Way
- ↑7: fast neutrons
- ↑8: speed of light in diamond
- ↑8.5: speed of light in vacuum
For a much bigger list, see Orders of magnitude (speed) on Wikipedia.
References
- Cosmic View: The Universe in 40 Jumps (Kees Boeke, 1956)
- Cosmic Zoom (National Film Board of Canada, 1968)
- Powers of Ten (Charles and Ray Eames, 1968)
- I shrink 10x every 21s until I’m an atom (Epic Spaceman, 2024)