The Universe Has Already Made Almost All the Stars It Will Ever Make

Our human world is soaked in light. For starters there are the 100,000 trillion photons arriving every second at every square centimeter of Earth’s dayside surface, after racing here from the outer envelope of a natural giant thermonuclear reactor we call the sun. There are also the photons that zip every which way through any cubic centimeter of open space. Some of these are the microwave leftovers from the hot Big Bang over 13 billion years ago, others are the photons produced in distant stars and innumerable astrophysical events strewn across the cosmos. 

We’re also bathed in locally-sourced, artisanal electromagnetic radiation. We warm, squishy humans are potent infrared beacons. Our fancy chemical metabolism sheds energy as heat, radiating photons off into the environment. If you could switch on goggles sensitive