In the quest to harness fusion energy—the same process that powers the sun—scientists are testing every detail to improve how future reactors, called tokamaks, will operate. One key focus is the use ...

Most of the universe’s hydrogen and helium atoms formed around 400,000 years after the Big Bang, which is the name for when scientists think the universe began, about 14 billion years ago.

Once the universe had sufficiently expanded and cooled, however, subatomic particles could acquire electrons to form neutral hydrogen atoms, and the cosmic dark ages began.

Hydrogen is the lightest and one of the most common atoms in the universe, usually found bonded in twos, but it’s difficult to isolate. Today, companies generate hydrogen by applying steam to ...