Ninety-three million miles away, in the heart of the star we call the Sun, just now 81 billion billion billion billion (8.1 x 10^37) helium nuclei were born. This happened last second, this second, and every second in the past and future stretching for billions of years in each direction. And, believe it or not, all this newly-born helium is what makes your peanut butter and jelly sandwich so delicious – in fact, what makes peanut butter and jelly even possible.
Inside the Sun, the mother of helium is hydrogen. The simplest hydrogen nucleus is but a single proton, one positively-charged particle flying about on its own in the inferno that is the solar core. Occasionally this hydrogen nucleus will slam into another just like it and stick. In the process, a particle called a positron comes flying out, transforming one proton into a neutron. The two hydrogens have changed into a new isotope, called hydrogen-2, or deuterium.
This process is very, very slow – a good thing, because it keeps the Sun from using up its hydrogen very quickly. In fact, the Sun is around 5 billion years old, and still has plenty of hydrogen for several billion more years of this hydrogen slam dance precisely because it is so difficult for two hydrogen nuclei to fuse into deuterium.
From there, though, things can happen rapid-fire. Another proton can stick to the deuterium, and then two such particles can smash into one another and stick, with wreckage in the form of leftover hydrogens flying off. The final result is that four hydrogen nuclei have transformed into a single nucleus. That nucleus is helium.
But wait, there’s more! For if you were to weigh the particles going into this reaction, and the particles coming out, you’d notice a difference. Helium has a mass 0.7% lower than the four protons that go toward making it up. That doesn’t seem like much, but it’s that magical 0.7 % that is responsible for butterflies, sea turtles, and, yes, delicious peanut butter and jelly sandwiches. That 0.7% mass difference transforms into energy via the famous equation E=mc^2, and that energy, first in the form of gamma rays, flies out of the reaction. The gamma rays heat up the Sun, and that heat becomes radiation – also ultraviolet, infrared, and visible light rays.
It takes thousands of years for light to make its way from the Sun’s nuclear core to the (relatively) cooler surface, but only around 8 minutes for this light to fly from the surface of the Sun through the frozen vacuum of space to finally encounter the Earth. Once those packets of precious energy arrive here, amazing organic machines called green plants work some more magic. They grab the photons and use their energy to split water molecules apart, combining hydrogen with carbon dioxide from the air to make complex, energy-rich storage molecules we call sugars. In the process the plants belch out a dangerous waste gas called oxygen.
The plants use sugar for everything. Some of it might go into building the complex proteins of a peanut, or perhaps become the sugars of energy-rich strawberries and grapes. Eventually, we plant parasites pick the peanuts, harvest the fruits, process them, pack them into screw-top jars, and finally spread this stored-up sunshine on slices of bread (with the crusts cut off, please!) With that first delicious bite, we taste energy that was first liberated 93 million miles away, on the day when helium was born. I think I’ll go have a sandwich now!