2:17 PM — Not to Scale I read in the following in someone's blog today:

I think a true space flight would be one which goes to the moon and makes a couple of rounds and then returns to Earth. Or, maybe something which goes halfway to the moon.

I was amazed at how ignorant this stament was. Most people really don't understand size scales involved in space at all. I replied with the following scale model.

If you take a basketball, or a soccer ball (football in Europe), it's around a foot (0.3m) in diameter. Call that the Earth. The Moon's size in comparison is one quarter of that, or 3 inches (8cm), or say a tennis ball. Now hold them 30 feet (10m) apart--maybe a couple rooms in your house apart--and that's how far apart the Earth and the Moon are, to scale. In this model, the Space Shuttle never gets more than 0.6 inches (1.5cm) from the basketball Earth, and certainly not halfway to the moon.

More specifically, the Earth is 12,700km in diameter, and the Space Shuttle orbit ranges from 185-643km above the surface (c/o Wikipedia). If we assume the basketball is 12" diameter, that gives me 643km/12,700km=x/12" --> x=0.6" (with 1 Sig. Fig.). The highest Mercury mission apogee was 285km, the ISS is at 360km, and the HST is 600km. (This difference between the ISS and the HST is why the ISS can't serve as a bail-out place for a potential future Hubble servicing mission that won't happen.)

If you find any errors in my calculations, feel free to post a comment and correct me. That's the beauty of science! :)  ¶ permalink | 0 musings