Unexplainable podcast: 17 of the most astounding scientific mysteries

pThree years ago, Vox launched Unexplainable, a podcast about unanswered questions and what we learn when we explore the unknown. There’s a line I think about all the time from our very first episode.

“Whatever we know is provisional,” Priya Natarajan, a Yale physicist, told us about research on dark matter. But the sentiment also applies to science overall. “It is apt to change. What motivates people like me to continue doing science is the fact that it keeps opening up more and more questions. Nothing is ultimately resolved.”

Unexplainable isn’t about how scientists don’t know anything. Science is a process of narrowing a gap between the questions we have and the capabilities of our tools and know-how to answer them. In many cases, that gap appears closed. No one doubts, for instance, the existence of gravity.

But even then, it is a scientist’s job to have intellectual humility, or at least to be open to the idea that there’s still a piece missing — as there is with gravity — knowing the results could just end up confirming what they thought in the first place.

Really, science is about a big question: How do we know when we’ve completely learned something?

What this series has taught us is that answering the question is a journey. Sometimes the stories on that journey are exciting — like what happens when NASA launches a staggeringly powerful observatory into space. Sometimes they are frustrating, especially when answers to a question are held back by powerful forces like scientific funding, perverse incentives, or stigma.

Most often, though, the stories are deeply human: We ask questions because we’re trying to understand our imperfect bodies, our beautiful but fragile world, and our place in the universe just a bit better.

We’re drawn to questions because they are optimistic. They invite us to dream of a better world in which they are answered, where the gaps between questions and our capabilities to answer them are smaller. Scientific knowledge is a gift we can give the future. It’s worth getting right.

Here are some of the questions that astounded us the most.

1) What is the universe made out of?

NASA

If you go outside on a dark night, in the darkest places on Earth, you can see as many as 9,000 stars. They present as tiny points of light, but in reality, they are massive infernos. And while these stars seem astonishingly numerous to our eyes, they represent just the tiniest fraction of all the stars in our galaxy, let alone the universe.

All the stars in all the galaxies in all the universe barely even begin to account for all the stuff out there. Most of the matter in the universe is unseeable, untouchable, and, to this day, undiscovered.

Scientists call this unexplained stuff “dark matter,” and they believe there’s five times more of it in the universe than normal matter — the stuff that makes up you and me, stars, planets, black holes, and everything we can see in the night sky or touch here on Earth. It’s strange even calling all that “normal” matter because, in the grand scheme of the cosmos, normal matter is the rare stuff. But to this day, no one knows what dark matter is.

So, how might scientists actually “discover” it?

Further reading: Dark matter holds our universe together. No one knows what it is.

2) How did life start on Earth?

DeAgostini/Getty Images

For decades, scientists have been trying to re-create in labs the conditions of early Earth. The thinking is, perhaps if they can mimic those conditions, they will eventually be able to create something similar to the first simple cells that formed here billions of years ago. From there, they could piece together a story about how life started on Earth.

This line of research has demonstrated some stunning successes. In the 1950s, scientists Harold Urey and Stanley Miller showed that it’s possible to synthesize the amino acid glycine — i.e., one of life’s most basic building blocks — by mixing gases believed to have filled the atmosphere billions of years ago and adding heat and simulated lightning.

Since then, scientists have been able to make lipid blobs that look a lot like cell membranes. They’ve gotten RNA molecules to form, which are like simplified DNA. But getting all these components of life to form in a lab and assemble into a simple cell — that hasn’t happened.

So what’s standing in the way? What would it mean if scientists succeeded in creating life in a bottle? They could uncover not just the story of the origin of…