Stopping the Earth's Spin

A few nights ago my 3 year old asked me how hard would it be to stop the Earth from spinning. (well that’s how I’m paraphrasing a combination of my bad recall and how I often need to translate what is being said)

I wanted to be able to give an answer beyond, “ a really big number”, so I thought I would sit down, crunch some numbers and get back with an answer. It turns out if I had been asked at a time where my brain was a bit more active I could have simply looked up the answer on Wikipedia. The Earth with a mass of 5.97*10^24 kilograms, rotating about its axis roughly every 24 hrs, has about 2.6*10^29 Joules of rotational energy.

Well that’s a bit too easy, and I want some value add for my curious little one. Here come some comparisons

Every second the sun produces about 3.83*10^26 Watts of energy, that means if you were to magically slow down the Earth by converting all of its rotational energy into light, you would produce a light as bright as the sun for a little over 11 minutes. (675 seconds for those curious).

Way too abstract and magical for the average person,

How many cellphones could the Earth’s rotational energy power?

say our average phone battery has a capacity of 4000 mAh and a listed voltage of 5 Volts (these are high values for May 2024, but I needed something that was close enough) This means our phone battery could hold about 72,000 Joules of energy. That’s enough to charge 3.58*10^24.

3.57*10^24 individual batteries just 1 time.

Darn that was also too crazy a number

Car batteries, that should help, say 75 kWhr battery packs, or 270 MJ of energy

well the Earth has as much rotational energy as 9.6*10^20 electric car batteries

That’s such a crazy big number that if all 8 billion people on Earth were to drive in electric cars that were magically charged by the Earth’s spin, the Earth would have enough energy to charge those 8 billion batteries 120 billion times.

Edit (5/10/2024) Some friends asked the nuclear equivalent.

For reference a kiloton of TNT is equal to 4.18x10^12 Joules of energy. To store that energy in electric cars, you would need 15,500 vehicles, that’s a lot of energy. In simple terms, the rotational energy of the Earth is equivalent to 6.18x*10^16 kilotons of TNT. Let’s put this in terms of America’s ability to destroy global civilization.

For the US nuclear arsenal, the average bomb has a yield of around 200 Kilotons, and there 5044 devices. Assuming each device has the average 200 kiloton yield, the entire American arsenal has a total nuclear potential energy of 4.22x10^18 Joules. Even with this outrageously massive number, the Earth’s spin has more energy, so much that it is equal to 6.12x10^10 nuclear arsenals. That would be equivalent to 8 billion humans having access to over 38,600 nuclear warheads.

At this point I truly don’t know how to phrase the energy of the Earth’s rotation in a way that we can actually appreciate, thinking about 8 billion cars is already crazy, then imagining that we could charge each of those 8 billion vehicles 120 billion times is more than I can actually comprehend.

Hopefully this post gave an interesting sense of the scale of our universe.

Edit courtesy of Wikimedia.

Source

Based upon a NASA image:

Author Marvel

Obadiah KopchakComment