Archive for November, 2017

Units. Of measure


Meters and liters, inches and feet.  Ounces, quarts, gallons.  Kilometers per second.  Light second, light minute, light hour, light year.  Terabyte, barrel, kilowatt, hands, stone, the things we measure have changed along with the way we measure things.  Learning the metric system is only a start, because our immediate neighborhood is only a few light hours across.

Mars averages about 12 light minutes from Earth, while the Earth is only about 8 light minutes from the Sun.  Light travels about 300,000 kilometers per second, so, unlike the Sun, Mars can be anywhere from 3 something light minutes away to about 22 light minutes.  Sometimes, a radio beep would take nearly an hour to go to Jupiter.

On Earth, everything is only a fraction of a light second away, but even the Moon is nearly a light second away.  To get into space, we have to get going about 7 kilometers per second, after we get above most of the atmosphere.  Space is only a about 100 kilometers from wherever you are right now, but the atmosphere gets very thin only a few kilometers up.  And space is big.  Really, really big.