Big Numbers

Let’s face it: numbers can be hard to imagine. I can handle up to about five. After that, my brain translates numbers into “more than five.” Anything past one hundred is “a whole lot”. And anything past a thousand is just “a whole heck of a lot.” That’s why, when astronomers spout off distances like “six trillion parsecs” or “eighteen gazillion kilometers,” my brain just hears “blah blah blah farther than my Toyota can drive blah blah.” The figures are meaningless.

Knowing this trend, I thought I might make more sense of the universe if I scaled it down rather dramatically, as follows:

• At the center: the Sun 
• At this scale, the Sun is just a grain of sand. 

  

  Grain of Sand

• The planets are no bigger than smoke particles.
• 5 inches: Mercury 
• 8½ inches: Venus
• 12 inches: Earth 
• Note: the Moon orbits about 1/32nd in. from Earth
• 18 inches: Mars
• 2-4 feet: the Asteroid Belt
• 5 feet: Jupiter
• 9½ feet: Saturn
• 19 feet: Uranus
• 30 feet: Neptune 
• 39½ feet: Pluto
• 30-100 feet: the Kuiper Belt
• 9.5 miles: the Oort cloud (theorized)
• 51.3 miles (yes, I said miles): Proxima Centauri, the nearest star to our Sun

Our miniature Solar System emphasizes a couple of things: (1) the dramatically exaggerated distance to the outer planets (Jupiter and beyond) as compared to the inner planets (Mercury to Mars), and (2) the ridiculous distances between stars. If, for example, you take two grains of sand (neighboring stars) and place them on mountaintops on opposite horizons, you have a rough idea of the density of the universe.
Insane!

Not happy with these numbers, however, I found it necessary to wrangle the Earth-Moon relationship.

Here is a typical graphic showing Earth and its moon:

From pictures like these, I have always assumed that the moon was maybe 3 to 5 Earth diameters from us. Sounds about right, no?

Wrong.

The Moon is roughly 400,000 kilometers away (yes, I know—“blah blah blah a whole heck of a lot”), which turns out to be no less than 30 Earth diameters. To make sense of it, I felt the need to sketch up a graphic, as follows:

(Note how tiny the Moon is. Also, the grey band is shows both the near and the far range of the lunar orbit.)

In other words, the Moon is a long ways from us. Buzz and Neil, I’m impressed!