I know you're a biologist, but you're very informative. Could you help me be as scientifically accurate as possible in writing sci fi? If aliens invaded our atmosphere (thermosphere and mesosphere), our oceans (about 1,000 meters below) and on some surfaces (arctic), and humans decided that the nuclear option was viable and launched nukes above the ships, what would the overall fallout be like? How long would radiation last, atmospheric impact, most affected altitudes, etc? Thank you
I want to start off by making it very clear: This would be an exceptionally bad idea. We’ll get to why in a moment, though. First I have a question for you:
Why do we always assume that aliens would want to invade Earth? If they want to destroy us there are so many easier ways, like just hurtling an asteroid at the planet. If they want slaves, then why don’t they just build robots? If they can travel between star systems, then I think it’s safe to assume they have pretty good robot technology and don’t need to rely on delicate, breakable humans. Minerals? There’s a whole asteroid belt full of ‘em, no war required. I can’t imagine what we have that’s worth invading for. Except maybe chocolate. Or avocados. Or cheese. Or coffee. On second thought, I think I’m hungry.
Anyway, back to your question. There’s upwards of 15,000 nuclear warheads on Earth right now. If we did choose the nuclear defense option to ward off aliens, it would quickly turn into the nuclear suicide option.
A couple years ago, a group of scientists estimated the global impact of a 100 warhead nuclear conflict between India and Pakistan. Here’s what they think would happen (excerpted from Popular Science):
Five megatons of black carbon enter the atmosphere immediately. Black carbon comes from burned stuff and it absorbs heat from the sun before it can reach the Earth. Some black carbon does eventually falls back to Earth in rain.
After one year, the average surface temperature of the Earth falls by 1.1 kelvin, or about two degrees Fahrenheit. After five years, the Earth is, on average, three degrees colder than it used to be. Twenty years on, our home planet warms again to about one degree cooler than the average before the nuclear war.
Earth’s falling temperatures reduces the amount of rain the planet receives. Year five after the war, Earth will have 9 percent less rain than usual. Year 26 after the war, Earth gets 4.5 percent less rain than before the war.
In years 2-6 after the war, the frost-free growing season for crops is shortened by 10 to 40 days, depending on the region.
Chemical reactions in the atmosphere eat away Earth’s ozone layer, which protects Earth’s inhabitants from ultraviolet radiation. In the five years after the war, the ozone is 20 to 25 percent thinner, on average. Ten years on, the ozone layer has recovered so that it’s now 8 percent thinner.
The decreased UV protection may lead to more sunburns and skin cancers in people, as well as reduced plant growth and destabilized DNA in crops such as corn.
In a separate study, published in 2013, International Physicians for the Prevention of Nuclear War estimated 2 billion people would starve in the wake of a 100-A-bomb war.
Multiply this time 150. I think you can see that this would be a bad idea. I would advise against putting this in your story, unless your story ends with humanity destroying itself.
