# [Paleopsych] kragen at pobox.com: the energy cost to evacuate Earth's human population

Premise Checker checker at panix.com
Mon Nov 14 23:20:21 UTC 2005

```The energy cost to evacuate Earth's human population
From: kragen at pobox.com
Date: Mon, 31 Oct 2005 03:37:02 -0500 (EST)
To: kragen-tol at canonical.org

http://en.wikipedia.org/wiki/Escape_velocity says:
On the surface of the Earth the escape velocity is about 11.2
kilometres per second.

You have: 100 kg * (11.2 km/sec) * (11.2 km/sec) / 2
You want: kilowatt hours
* 1742.2222
/ 0.00057397959

So 1700 kWh per (large) person, to lift them out of Earth's gravity
well (assuming perfect efficiency, as with a space elevator.)

http://www.ecoworld.org/energy/EcoWorld_Energy_Resid_KWH_Prices.cfm lists
average US residential electricity prices from 6.5 to 14.8 cents per kWh, with
an outlier at 33.3 in San Francisco during the California energy crisis.  It
also claims that the cost of the fuel alone amounts to about 0.5 to 1 cent per
kWh.

So if we have to pay 10 cents per kWh, lifting a person into space should cost
around \$170 --- an energy cost that could in theory be recovered if they came
back down.  (At present this energy is mostly dissipated thermally.)

Evacuating the entire human race to an extraterrestrial habitat
prepared to handle them should then have an energy cost around \$1
trillion.  This is roughly 2% of annual world GDP (\$55.9 trillion) at
PPP.  (See http://www.worldbank.org/data/databytopic/GDP_PPP.pdf for
details.)

Current world energy usage is around 354 exajoules
(http://energy.er.usgs.gov/products/Papers/WMC/17/) or 400 exajoules
(http://www.pugwash.org/reports/pac/agra/agra_reports_wg4.htm) or 375
kWh per person is

You have: 1742 kilowatt hours * 6 billion
You want: joules
* 3.76272e+19
/ 2.6576519e-20

38 exajoules, a significant fraction of world yearly energy usage, but
far from unimaginable.  It would probably be enough to raise the unit
price of energy.

I conclude that, while technical obstacles currently make evacuation
of Earth's population to extraterrestrial colonies impossible, the
energy cost of the evacuation itself is within reason.

```