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xkcd #3283: Size and Lifespan
(imgs.xkcd.com)
Title text:
With their 13 years recording and performing together and two humans worth of mass, the White Stripes are sandwiched neatly between gray wolves and blue whales.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3283/
Play tectonics is pretty well studied, plus you got the whole part where the sun becomes a red giant and annihilates the planet. I bet Randall worked it out pretty well.
Back of the envelope it’s about 10^17 seconds, which works out a few billion years. He drew it with some wiggle area, so anywhere from hundreds of millions to several billions which covers the range of plate tectonics and the Earth being consumed by the sun.
So it seems pretty accurate
Oh right, it's logarithmic, so that wiggle area is much bigger than it would be on a similar linear graph. I also forgot about the sun swallowing the earth, which would prevent Greenland from getting into another order of magnitude, though there is always the possibility that earth will get flung either to a higher orbit or out of the solar system entirely before the sun swallows it and Greenland will last for trillions of years.