Tuesday, March 16, 2010

A Weighty Matter

Hey, I gained a pound last week!

Since weight is equal to mass times acceleration, either mass or acceleration must have changed.

The acceleration of gravity at Earth's surface is about 9.8 m/s2. My weight increased by 1 pound, which is about 0.6% for me. If the acceleration of gravity at Earth's surface increased by 0.6%, then Earth's mass must have increased by that amount. Earth masses1 about 5975 x 1021 kg, and 0.6% of that is about 36 x 1021 kg. That's about the same as Europa, one of the four largest moons of Jupiter. (Europa is just a bit smaller than our own Moon.)

So an object with the mass of Europa collided with Earth last week, and only I noticed!

Or maybe I just ate too much shoo-fly pie.

1 I'm using "mass" as a verb, because Earth doesn't "weigh" anything!

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