What Would Happen If the Earth Grew One Centimeter Every Second

As part of their ongoing “What If?” series, Randall Munroe of xkcd and Henry Reich of MinutePhysics explain what would happen Earth grew its radius by one centimeter every second. Munroe explains that weight would go steadily up as the pull of gravity grew stronger, but other things would start to fail.

After a year, gravity would be 5 percent stronger and the ground underneath structures would have expanded 5%. You’d probably notice  the weight gain, and you’d definitely notice the failure of roads, bridges, power lines, satellites, and undersea cables. Your pendulum clock would now be ahead by five days. After five years, gravity would be 25% stronger. If you weighed 70 kg when the  expansion started, you’d weigh 88 kg now. 

After about a ten years of Earth’s growth, the gravity pull would be difficult to navigate and it would be difficult to breathe.

After 10 years, gravity  would be 50 percent stronger. We’ll assume the atmosphere is expanding, too, otherwise there wouldn’t be enough to cover the growing earth and the air would by now be too  thin to breath. With an expanding atmosphere, surface air pressure would rise due to  both increased gravity and more air,  

After 100 years of growth, the environment would be completely toxic to most forms of life.

After 40 years, Earth’s surface gravity would have tripled. At this point, even the  strongest humans would be able to walk only with great difficulty. Breathing the thick air would be a challenge. Trees would collapse and crops wouldn’t stand up under their own weight. After 100 years, we’d be experiencing over 6 G’s of gravity. Not only would we be unable to move around to find food, but our hearts would be unable to pump blood to our brains. …On top of that, at somewhere around this point, even ordinary air becomes toxic  due to higher oxygen levels. 

Needless to say, as with all of these hypotheticals, the future under these conditions doesn’t look very bright, but there is good news on this front. After the destruction of the moon, the Earth for a very short moment will have rings like Saturn.

 As the Earth grew, the Moon would, like all our satellites, gradually spiral inward. After several centuries, it would be close enough to the swollen Earth that the tidal forces between Earth and the Moon would be stronger than the  gravitational forces holding the Moon together. When the Moon passed this boundary?—?called the Roche limit?—?it would gradually break apart, and Earth would, for a short time, have rings.