The Bubble Nebula is on the outskirts of a supernova remnant occurring thousands of years ago. Nebulae like this showcase where massive stars are born, and also where heavy elements get added back into the Universe, giving rise to rocky planets and organic materials like what we find here on Earth. Image credit: T.A. Rector/University of Alaska Anchorage, H. Schweiker/WIYN and NOAO/AURA/NSF.

This one imperfection in nuclear physics allowed Earth to exist

If all we had were hydrogen and helium after the Universe were born, we wouldn’t be here today.

“The discovery of deuterium and the marked differences in the physical and chemical properties of hydrogen and deuterium, together with an efficient method for the separation of these isotopes, have opened an interesting field of research in several of the major branches of science.” -Harold Urey

In order to create a rocky planet that’s teeming with life, the Universe needed to create large amounts of the heavy elements required for life’s processes. To make many of those elements, such as Tin, Iodine, Selenium, Molybdenum, Zinc, and Copper, you need supernovae to have occurred many times in our galaxy’s past. To get many more, such as Iron, Calcium, Cobalt, Sulfur, and Potassium, you need stars massive enough to create them. Yet the Universe was born, almost exclusively, with mere hydrogen and helium. If all you had was hydrogen and helium, it would be impossible to make a star more massive than about three times the Sun’s mass; these heavy elements would never be created and spread throughout the Universe. The only reason we can exist, today, is because one tiny imperfection in the early Universe allows the stars to grow hundreds of times as massive.