NOVA Now

For tens of thousands of years, humans have pondered eternal questions like “How does our world even exist?” and “Where did we come from?” Now, more than ever, scientists are finding answers within the Big Bang theory. About 13.8 billion years ago, in a fraction of a fraction of a second, the universe expanded into being. The event, astronomers believe, was less of an explosion than a transformation of energy into matter: As this so-called inflation slowed, it gave way to matter, radiation, and all we know today. But more questions loom. To learn how scientists came up with the Big Bang theory, Dr. Alok Patel hears from a physicist and a cosmologist about the forces that shaped our early universe and the tools researchers use to peer back in time. And, he learns what scientists’ understanding of the universe’s origins can tell us about its ultimate end.

Black holes: they’re dense, elusive, light-absorbing pockets of spacetime that are critical to our understanding of the universe. But black holes are difficult to peer into, so there’s a lot scientists still don’t know. This leaves some room for science fiction to take over. Tall tales of galactic adventure may pair well with popcorn, but they also blur the lines between fact and fiction. To explore what humanity knows—and what we think we know—about black holes, Dr. Alok Patel and a theoretical cosmologist journey to Earth’s closest black hole: the Milky Way’s own Sagittarius A*, approximately 26,000 light-years away. (Don’t worry; no scientists or science nerds were harmed in the making of this podcast.)

If television shows and movies are any indication, we humans spend a lot of our time subconsciously preparing for UFOs carrying maleficent aliens to descend on Earth. But should we rush to create an intergalactic battle plan? In actuality, finding otherworldly life won’t be so easy (or, hopefully, so dangerous). Already, astronomers and other scientists are using a multitude of techniques to search for planets outside our solar system and any signs of life they carry. With 4,500 exoplanets identified out of what could be hundreds of billions in our galaxy alone, one thing is becoming clear: If we find extraterrestrial life, it likely won’t be anything like Hollywood has imagined. Hearing from two exoplanet experts about the diversity of planets and life in the Milky Way, Dr. Alok Patel learns that Earth is incredibly unique—and surprisingly mundane.

When our ancestors looked up into the night sky, they too saw a great, glimmering band of light splitting the darkness. In Southeast Asia, people called it “the Silver River.” In Southern Africa, “the Backbone of the Night.” And in the West, around 2,500 years ago, it earned the name “the Milky Way.” Across the globe, civilizations had theories of what the band of light was and why it was there. But only recently have humans had the tools to get the full picture. Today we know the Milky Way is our galaxy: two spiral arms filled with more than 100 billion stars, all rotating around a supermassive black hole. And here on our little blue planet, we’re in the middle of it all. Dr. Alok Patel speaks with two galaxy experts to find out how scientists have built the first high-resolution, three-dimensional map of the Milky Way—and what that map reveals about the formation and future of our galactic home.