When we Americans talk about “the Pilgrims,” we usually are talking about the group of English settlers who came to North America in 1620 in search of religious freedom. They celebrated a good fall harvest the following year, which became the first Thanksgiving.[1] In general, a pilgrim is someone who makes a journey for religious purposes.
What then is a space pilgrim? Suppose the entire population of the Earth needed to evacuate the planet and relocate elsewhere. Granted evacuation itself would not technically make us all pilgrims, we could probably argue that there is religious significance in staying alive. So we might be able to call ourselves pilgrims, using the term loosely. Traveling into space as pilgrims probably could earn us the title of space pilgrims as well.
Nomenclature aside, how much energy is required to get every living human off the Earth and relocated elsewhere? Getting anything off the Earth and to some specific destination can involve some complicated math. Since this is intended to be merely a quick look at the scale of a planet-wide evacuation, I’m trying to keep things simple. Fortunately, someone posting on StackExchange has indicated the amount of energy required to reach lower Earth orbit (LEO), namely 32.0 megajoules (MJ) for one kilogram.[2] This is only the theoretical amount of energy required to counteract gravity enough to move 1 kg to that altitude. It does not include the energy lost to the inherent inefficiency of any machinery. Also, that number does not tell us anything about what happens after reaching that height.
How many kilograms do we need to move into space to account for every living human? Though I did not find the weight of the entire Earth population, the ZME Science web site does happen to describe a 2005 study estimating the weight of all the adults on Earth at 287 million tons.[3] That figure is inclusive enough to give a rough idea. If not, maybe someone (local extraterrestrials?) has a deal where kids ride free on Tuesdays, and in that case, let’s hope that our space pilgrimage takes place on a Tuesday.
We can estimate the current weight of all adults by using the ratio of the total adult weight to the total population (including children). The Worldometers web site has a list by year with the 2005 world population at 6,542,159,383 and the 2018 population at 7,632,819,325.[4] That number for 2018 will of course continue to change until the end of 2018. As of November 26, 2018, the world population to 3 significant digits is 7.67 billion, also according to Worldometers, though I myself performed the rounding.[5]
Doing the math gives us an estimate of the current weight of the world adult population in tons: (287,000,000/6,542,159,383)*7,670,000,000 = ~336,000,000 tons. Turns out, those are British tons based on pounds, but the LEO energy figure above is based on kilograms. I’m assuming those are “short tons” of 2,000 pounds each. I found an easy converter at UnitConversion.org indicating that the world adult population has a mass of about 304,814.07264 kg, which I’m rounding to 305,000 kg.[6] That gives a final energy of 305,000*32.0 MJ = 9,760,000 MJ . In household terms, that’s about 2,710,000,000,000 kilowatt-hours (kWh). In comparison, the United States produced 4,034,000,000 kWh in 2017, according to the U.S. Energy Information Administration.[7]
Yes, it apparently would take well over 500 years for the U.S. to generate that much electricity, assuming the U.S. used its full electricity generation capacity in 2017. And that’s to lift just the adults to lower Earth orbit and not to lift any equipment to actually transport people to orbit or to actually keep them alive. It looks like we’re not going anywhere soon in very large numbers, at least not all of us. Bottom line, we better try harder to solve the problems of global warming, pollution, overpopulation, etc. Or maybe develop reliable teleportation technology, though I suspect that would also take a very large amount of energy.
References:
[1] https://www.plimoth.org/learn/just-kids/homework-help/who-were-pilgrims
[2] https://space.stackexchange.com/questions/4330/how-much-energy-is-required-to-put-1-kg-in-leo
[4] http://www.worldometers.info/world-population/world-population-by-year/
[5] http://www.worldometers.info/
[6] http://www.unitconversion.org/
[7] https://www.eia.gov/tools/faqs/faq.php?id=427&t=3
(c) Copyright 2018 by Mike Ferrell
Odd STEM 