Since the invention of the periodic table 150 years ago this month, scientists have worked to fill in the rows of elements and make sense of their properties.
But researchers have also pursued a parallel quest: scouring the cosmos to figure out where all 118 elements came from.
After centuries of effort, they have determined that the vast majority of elements were forged in the fiery lives and strange deaths of stars. They now pervade galaxies, infusing the next generation of stars and planets with chemical diversity.
Indeed, every element on Earth _ except for a few made recently by humans _ was inherited from the nebula that gave birth to our solar system 4.5 billion years ago. That includes the iron in our skyscrapers, the silicon in our computers, the gold in our jewelry, and the calcium in our bones.
"There's a real connection between our galaxy _ our universe _ and our humanity because of the elements." said John Cowan, an astrophysicist at the University of Oklahoma.
So how did nature fill up the periodic table? The story starts at the beginning.
The very beginning.
