On January 6, North Korea announced to the world that it had successfully detonated a hydrogen bomb, prompting the United Nations to consider even stricter sanctions against the already isolated and hobbled regime. The international community is atwitter with doubts and fears (and headaches), as the boastful and unpredictable country attempts to shake up the world order once again. Because the thing is, a hydrogen bomb is much more potent than your average atomic bomb. And here's the science behind why.
Before diving into what an H or hydrogen bomb is, we need to start with the basics. Atomic weapons use nuclear fission to generate their destructive power. Hydrogen bombs use both fission and fusion ”” in that order. So what's the difference? Let's break it down.
Fission is the process whereby the nucleus of an atom will break apart, and its constituent parts ”” the positively charged proton and the neutral charged neutron ”” will split off. Highly radioactive elements, like uranium, are much more inclined to start a cascading effect when the nucleus fissions. That means that if you slam a uranium isotope (one form of the element) with a bunch of small particles, it will break apart like mad...and send more and more nuclei into a frenzy. When a nucleus splits, it produces separate neutrons and protons, but it also releases a lot of heat and energy. That's where the explosion comes from.
To make an atomic bomb, you need a critical mass of elemental matter that will quite easily undergo this fission (i.e. be radioactive). That's where enriching the element comes into play ”” turning it into an isotope that will break up easily. Then you've got to cram all that matter into a warhead, so that upon impact, the neutrons will go splattering all over each other, and send out a chain reaction that's ultra deadly. Such force has only been used in one nuclear attack...and guess by whom.
On August 6, 1945, America dropped an atomic bomb on Hiroshima in Japan, immediately killing 80,000 people. Just three days later, it dropped another on Nagasaki, killing about 40,000. Thousands of others died from residual radiation poisoning. Einstein himself was not part of the Manhattan Project that brought the atomic weaponry to fruition, though in 1939 he did pen a letter to then-president Franklin D. Roosevelt exhorting him of the necessity of large-scale atomic warfare. In a 1952 essay to Japanese publication Kaizo, Einstein begged pardon for his limited, but perhaps significant, involvement.
Now that we've got the atomic bomb out of the way, it's time to raise the stakes. North Korea didn't say it successfully dropped an atomic bomb ”” which would have been slightly less alarming news; it said it dropped a hydrogen bomb. The hydrogen bomb, or thermonuclear weapon, takes the energy generated by a fusion reaction to power a fusion reaction. Fusion, the opposite of fission, is the fusing of two nuclei together into one...a process that also results in massive amounts of explosive energy ”” even more so than that from an atomic bomb.
After the atomic fission reaction occurs, it sends all the neutrons produced from the fission or primary step of the bomb into the thermonuclear chamber (the secondary step) where there is a critical mass of a solid compound lithium deuteride ”” lithium plus deterium. When this happens: boom. The neutrons plus the lithium deuteride fuse to form helium and hydrogen isotopes (hence the name), releasing lots and lots of power.
One of the snags to the hydrogen bomb process was sustaining the energy produced in the primary so that it would not dissipate before instigating the fusion reaction. Physicists Edward Teller and Stanislaw Ulam figured out that if you put a kind of buffer material between the two stages, you can bolster the energy and effect the fusion that way. They used none other than styrofoam to absorb the shock wave gamma rays that resulted in the fission process, and it's those rays that force the compression of the lithium deuteride and the neutrons in the vessel.
On January 31, 1950, President Harry S. Truman announced that the US was going to get down and dirty with the latest in morbid modern tech: the hydrogen bomb. Just under two years later, the country dropped Mike, a 10.4 megaton H-bomb that utterly vaporized an island. The scientists behind it had used Teller and Ulman's ideas, which were then used in similar fashion by the Soviets (who had lifted everything the Americans worked on through the use of a spy).
So, how hard could it be to make a hydrogen bomb? In fact, a lot ”” which is why so few superpowers (purportedly) have one, and why it would mean big things for North Korea if it succeeded in building one. The first hurdle to overcome is to acquire or extract enough of the special kind of atoms that lend themselves to radioactivity. For the primary, it's uranium or plutonium, both of which need lots of enrichment. This takes time, space, money and energy. The same is true of the secondary, which requires tritium and deuterium (rare isotopes of hydrogen), that require even more input.
The other problem is that while it's easy to make a really big bomb, it's harder to fit all that complexity into something that can be sent soaring through the sky. When Russia dropped its hydrogen bomb Tsar Bomba, it was 3,000 times bigger than Little Boy, the bomb America dropped on Hiroshima. That takes some mad skills. Very mad.
So, when North Korea purportedly dropped its first hydrogen bomb, it sent out seismic quakes that were detected by monitoring stations around the world. Experts and dignitaries are split on how to take the information. North Korea has detonated atomic bombs three times in the past, and some believe that what the rogue nation is calling a hydrogen bomb is actually a boosted atomic bomb. A boosted bomb is a fission bomb that uses a little bit of fusion stuff for an added punch. That's the lesser of two evils, if it's the case.
There are ways to tell what kind of weapon is used, but they are not always 100 percent reliable. For instance, scientists can test the area around where the detonation took place for fission fragments, which are byproducts of the reaction. They mostly take the form of noble gases (naturally occurring gases) like xenon, and which can also be very dangerous. But this will only indicate fission reaction.
Another way to discern atomic explosion is by measuring the effects one had on the rock in the ground. The explosion would have sent waves through the ground, compressing the rock in what's called a P-wave, meaning you'll see first compression then radiation from the source in the rock. This is different from the kinds of waves produced by an earthquake (S-waves) in that the effect is asymmetrical. The only problem is that you can generate P-waves in rock with enough power ”” they're not necessarily a dead ringer for hydrogen bomb, just a big explosion.
For what it's worth, the White House's initial reports on the subject state that the readings from North Korea's detonation do not match its own metrics on hydrogen bombs. When America let loose its own thermonuclear weapon underwater in 1971, it caused a 6.8 magnitude earthquake. By contrast, North Korea's quake clocked in at 4.8...even smaller than the last fission bomb it detonated in 2013. So, hopefully these numbers are telling.