There is a special kind of hydrogen. 
There is a special kind of hydrogen. 
Most of it was made a long time ago. It was made when the universe began. 
Scientists use it for many things. They use it in power plants. It can even be used in weapons. It is a very useful thing to find.
There is a special kind of hydrogen called deuterium. 
A scientist named Harold Urey found it in 1931. 
We can find deuterium in many places. It is in the oceans on Earth. It is also in space. Some comets have a lot of it. One comet, 67P, has three times more than Earth's water. This helps scientists think that Earth's water might come from comets.
People use deuterium for many important jobs. It is used in nuclear weapons. It is also used in experiments to make power. Scientists use it in special tools to study tiny things. It is a very useful part of our world.
Deuterium is a special kind of hydrogen that is a bit heavier than the kind we see most often. 

To understand how it works, we have to look at its tiny center. 
A scientist named Harold Urey discovered deuterium in 1931. 
Most of the deuterium in space was made a very long time ago. It was created during the Big Bang about 13.8 billion years ago.
We can see how deuterium connects to our own world by looking at space.
Deuterium, also known as hydrogen-2 or heavy hydrogen, is a stable isotope of hydrogen. 
The unique mass of the deuterium nucleus affects how its electrons behave. In quantum mechanics, the energy levels of electrons depend on the reduced mass of the atom. 

Most deuterium in the universe was created during the Big Bang 13.8 billion years ago. During the early universe, a period known as the deuterium bottleneck occurred. At first, the universe was too hot for deuterium to stay together. Any deuterium that formed was immediately destroyed by high energy levels. Once the universe cooled to a specific temperature, a sudden burst of element formation happened. This allowed deuterium to form, which then fused into helium. This process helped set the ratio of elements in the early universe.
Deuterium is a vital tool in modern science and industry. It is used in many nuclear weapons and fusion power experiments. 


American chemist Harold Urey discovered deuterium in 1931. 
Astronomers use the ratio of deuterium to hydrogen to study space. 
Deuterium plays a complex role in the life cycles of stars. While it is produced by the slow stellar proton-proton chain, it is also rapidly destroyed by fusion. 
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