Posted in DC Comics, Science, Superheroes, Superman

Krypton, Earth, and the Drake Equation

One of the most captivating parts of Superman, is his mythology. Granted, his origin bears a striking similarity to biblical and mythological figures. It provides a fascinating background in which to base a truly wonderful superhero. However, a question that may burn in your mind when thinking of it. Why did Jor-el send Superman to Earth specifically? What makes Earth so special? It’s been shown in the comics frequently that there are plenty of other planets capable of supporting life, so why Earth?

In Superman: Birthright, we get a brief glimpse at Jor-El firing the rocket. Running simulations to see if the rocket can even escape Krypton’s destruction. Just as the planet begins to erupt, it seems that an actual target for the rocket is an afterthought. Jor-El runs to the console and quickly selects a planet that seems to have the best chance of letting his infant son live.

“Billions of worlds we know NOTHING about. Merciful Rao, let there be one – Yes. Lit by a yellow star. It’s gravitational pull relatively negligible. If he makes it at all, he’ll stand his best prospects here. Computer, secure COORDINATES.”

Given Jor-El’s rushed state, it’s worth asking. If he had run the calculations sooner, and looked a little longer, would he have found a better option? To unravel this question, let’s use the Drake Equation to see if there is a possibility.

Created by Frank Drake in the 1950s, the Drake Equation was created to help estimate the likely hood of intelligent life existing elsewhere in the universe. At this point in history, no part of the equation has a definitive number, and some are beyond calculation, so right now, we need to use available information, and best guess. The equation proposed looks like this:

N = R* × Fp × ne × Ft × Fi × Fc × L

N represents the number of Intelligent civilizations in the galaxy. R* is the birth rate of suitable stars for life in the Milky Way Galaxy, measured in stars per year. Fp is the fraction of stars with planets. ne represents the number of planets in a star’s habitable zone. Ft for the number of civilizations that have technology and want to make contact. Fi is the fraction of habitable planets were life exists. Fc is planets inhabited by intelligent beings, and L is the average, in years, for an alien civilisation to invent radio, up until their culture is destroyed or disappears.

In this case, we are looking for what N‘s value is. When proposing the equation, Drake used the Earth and what we know of our own solar system as a model. R* has been estimated to be anywhere between 1 and 10. When proposing this, Drake used the middle estimate, so for now, we will use 5. For Fp, Carl Sagan, an American astronomer, believed that most stars had planets. However, the conservative estimate is around 20%, or 1 in 5. With our solar system as a model, then ne equals 1, as Earth is the only habitable planet in our solar system. Again, using Earth as a model, and without any other available data, then Fi, Fe, and Ft are all at 100%. L is the hardest to calculate, as even when using Earth as a model, you can’t find a definitive answer. We are still alive. Hence why we are asking questions. Drake and Sagan estimate that the number maybe anywhere between 100 and 10,00 years. While this gives us an estimate for just our galaxy, the Milky Way is estimated to be 100,00 light years across. In Superman #132, Krypton is stated to be 3 Million light years away from Earth. Within that distance, there are approximately 20 other galaxies. Add in the Drake Equation, and this gives us a possibility of around 2,000 to 200,000 possible planets Jor-El could have sent Superman to, besides Earth.

So, it looks like it was luck that Jor-El chose Earth. Case closed.

However, in 2000, Ward and Brownlee re-evaluated the Drake Equation in their book Rare Earth. They looked back at the estimates previously suggested, and comparing it to data collected in the 50 or so years since its original inception. Their findings force all of those previously established numbers to move to their lower estimate. After re-entering the data, this gives us a maximum number of possible planets from 200,00, to only about 1,000. Condensing this back down to just the Milky Way, this makes it highly likely that Earth is the only planet with intelligent life nearby.

It seems it wasn’t fate that brought the Man of Steel to us. Simply, we were a last resort.

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