There's a disturbing reason scientists are worried about the bomb North Korea says it just set off

North Korea claims it set off a hydrogen bomb on Wednesday morning - a claim that, if true, stokes fears of the rogue nation's nuclear capabilities.

Scientists are attempting to confirm whether the claim is true, but experts are skeptical.

What is a hydrogen bomb?

A hydrogen bomb, also known as an H-bomb or thermonuclear weapon, is created by smashing together radioactive hydrogen atoms in a process called nuclear fusion - the same type of powerful reaction that fuels our sun.

Atoms consist of positively charged protons and neutrally charged neutrons in their nuclei, as well as negatively charged electrons. All forms of an element have the same number of protons, but some can have different numbers of neutrons, and these are known as isotopes. H-bombs work by fusing certain radioactive isotopes, which releases an enormously destructive burst of energy.

Hydrogen bombs differ from conventional atomic bombs, which work by splitting atoms from heavier elements such as uranium or plutonium, a process called fission. Whereas conventional A-bombs occur in just one stage, hydrogen bombs occur in two stages - an initial fission stage, followed by the secondary fusion stage, which releases much more energy.

In fact, hydrogen bombs are about 1,000 times more powerful than atomic bombs.

The United States tested the first hydrogen bomb in 1952 on Eniwetak Atoll in the Pacific, and most of the world's nuclear powers possess H-bombs now.

How will experts know if it's an H-bomb?

When you detonate a bomb with the massive amount of energy of a nuclear weapon, it generates seismic activity that can be picked up by earthquake sensors called seismometers.

Using these instruments, the US geological Survey detected a magnitude 5.1 seismic event in northeastern North Korea, where the bomb was supposedly detonated, according to the New York Times. That's similar to the magnitude 4.9 event detected in 2013 when the country last tested an atomic bomb.

South Korean intelligence officials estimate that the recent event released the equivalent of six kilotons of explosive material TNT - about a third the energy released by the atomic bomb the US dropped on Hiroshima during World War II.

If it was an H-bomb, we'd expect it to release much more energy - hundreds of kilotons of TNT, making scientists doubt the claim.

Instead, many believe the country may have instead developed a weapon that is less powerful than an H-bomb but more powerful than a conventional A-bomb, called a boosted-fission weapon. You can make these weapons by adding a radioactive element of hydrogen such as tritium to the core of a conventional atomic bomb, which uses a small amount of nuclear fusion to increase the rate of the fission reaction.

If North Korea's claim to have set off an atomic bomb is true, it would be the fourth time the country has detonated a nuclear weapon, the Times reports.