What If The Atmosphere Caught on Fire?
Imagine for a moment your standing in the middle of the Jornada del Muerto desert in New Mexico. It’s July 16th 1945, at the height of World War 2. Robert Oppenheimer must be standing out here somewhere in the cold night. He must be anxious. The clock is counting down to the explosion of Trinity, the first atomic bomb. What if all of this work is for nothing, and the device fails to detonate at all? Worse, what if it does work? What if the Trinity device heats the nitrogen atoms in the atmosphere to fusion temperatures? The explosion could incinerate the Earth.
The clock ticks to zero, firing the high explosives in the Gadget. The shock waves converge on the plutonium, squeezing the core into a supercritical state. A stray neutron splits a plutonium atom, releasing more neutrons and energy. The reaction grows exponentially, liberating vast sums of energy and heating the air into an incandescent fireball that rises above the barren landscape like the sun.
Oppenheimer took a deep breath and let the melancholy set in. It worked, he built a bomb. A weapon that could destroy the world. But it hadn’t burned the atmosphere. Arthur Compton had been right all along.
In 1922, the physicist Arthur Compton had observed that x-rays scatter off electrons. Or to be more exact, the x-ray photons transfer their momentum to the electrons at the expense of their own energy. This effect diminishes the frequency of the x-rays. The scattering in effect cools down the radiation.
In the dense plasma of the Trinity explosion, the electrons had stolen away the energy of the photons before they could heat the nitrogen atoms to ignition.
The Hydrogen Bomb
Even today, nuclear fusion is notoriously difficult to ignite in the laboratory. Thermonuclear bombs can only achieve their scary destructive power because they channel the energy of an exploding fission explosion for a brief moment to squeeze the hydrogen fuel to ignition. It is speculated that mirrors lining the inside of the bomb reflect the x-rays from the fission explosion onto the capsule of hydrogen fuel. The capsule’s casing is vaporized and this squeezes the capsule. There is another rod or orb of plutonium inside the capsule and this is crushed until it is supercritical. It explodes in a second fission explosion and heats the fuel to millions of degrees, sparking fusion in the fuel and sparking a still more grand explosion.
What if you could burn the atmosphere?
The free nitrogen atoms in the atmosphere are exceedingly hard to fuse. Even if you could magically place these atoms inside the sun, you’d still get nothing. Our sun would have to grow to eight times its current mass to fuse nitrogen. Stars of this mass are prone to supernova explosions, but that is another story for another time.
But what if you only want to burn hydrogen gas instead? This is difficult to begin with since hydrogen is a trace gas in our atmosphere. Put the hydrogen gas next to the incandescent plasma of a nuclear explosion, and you still get nothing. The effect of Compton Scattering will again steal away the energy before the reaction can propagate.
What if you added more hydrogen to Earth’s atmosphere? At first nothing. Hydrogen is a light gas that easily escapes the atmosphere. Most of the hydrogen on Earth is bound in water molecules. But in time as the concentration grew you’d experience more headaches and nausea. Keep adding hydrogen and you could expect many more fires and explosions. Still hydrogen burns clear, so you can’t see it until you are on fire. However there is not enough oxygen currently available in the atmosphere to sustain these fires and they’d fade away. Let’s keep adding hydrogen. You’d suffocate along with all the other life on Earth. The atmospheric pressure begins to rise and in time it crushes everything on the surface. This rising pressure would heat and in due time evaporate the oceans liberating much more hydrogen.
Add a Jupiters worth of hydrogen, and still no ignition. Keep adding a Jupiter’s worth of hydrogen until you reach thirteen Jupiter’s. Only then will the deuterium ignite under the immense pressure of 1,000,000 bar and 53,999,540 degrees fahrenheit. Deuterium is an isotope of hydrogen and its supply is limited. You could expect the planet to burn at a warm magenta for only a few million years.
This is ridiculous. What about just sparking ordinary combustion? Some people just want to watch the world burn! The situation was much different 400 million years ago during the Carboniferous period. The National Academy of Sciences says that during that age oxygen levels peaked as high as 26 percent, at this concentration most anything burns. Left alone, a single spark from lightning could spark a fire and from there a wildfire. Left unchecked, the heat of the fire builds into a firestorm. Air spirals around and into the inferno at hurricane force. Anything near its presence burns, propelling vast quantities of hot smoke into the sky. Any moisture in the air condenses on the smoke into clouds and rain, finally extinguishing the fire. This is assuming that all of the fuel isn’t consumed first.
The situation is much different in our present age where some of this oxygen has been sequestered by erosion. Over time the elements erode minerals. Then the minerals are further oxidized consuming the oxygen. Reducing the atmosphere to the 20 percent oxygen concentration of today.