Bay Area locals may recognize this ad, which I found on BART. I thought it was hilarious, though you may not unless you share my appreciation for energy/power errors in your sense of humor.


I've taken better pictures in my life. The caption reads: "Power from the sun: 400,000,000,000,000,000,000 kilowatts per second." This of course makes no sense, as a kilowatt is a unit of power, which is basically a rate of energy transfer (a watt is 1 Joule per second, and a Joule is a unit of energy).

It is true that a tremendous amount of solar power is intercepted by the Earth, but we need to incorporate context and the appropriate units into our illustrations. In terms of solar power hitting Earth's land mass, the rough number is about 7000 TW, or 7,000,000,000,000 kW. Where these folks got their 4x1014 kW per second [sic] figure from I have no idea--it's possibly expressing a kWs (kilowatt-second) estimation, a.k.a. the amount of energy produced by a 1-kW power source over 1 second. Or it could by kWh (kilowatt-hours). I have no idea, but either way they're mislabeling their units, probably in the name of including a VERY BIG NUMBER in their illustration.

Without proper units or context, numbers are meaningless. In this case, the number is a lie.

See blogger Lee.org for a similar take on this silly ad.