Nobody Knows

A couple of days ago, I made it a point to talk about how much easier it is to find answers to things nowadays. Gone are the days of wondering the answer to most questions: search is your friend, and it has only gotten better over the last 25 years.

Whether you want to learn about a 2000 year old computer, the observation problem in physics, or the history of coffee, you can do that with the touch of a finger or simply by speaking. Satisfying your curiosity has never been easier.

However, there are plenty of things out there that aren’t so easy to figure out no matter how much you search. For all its majesty, the internet is simply a collection of things we know, and there are far more of things we don’t know than the things we do know.

I’m usually skeptical by default whenever someone says “nobody knows” something. I’m skeptical because I’ve heard this my whole life, and most of the time it has turned out to be wrong. Still, there really are some things that are beyond our knowledge, things that nobody knows.

For instance, nobody knows whether there is alien life out there.

That’s right, folks. It’s not actually rational to assume that there is simply because it would be an awful waste of space otherwise, as Jodie Foster’s character Dr. Arroway says in Contact.

To see why, let me show you the Drake Equation, a formula proposed by astrophysicist Frank Drake back in 1961. Drake sought to answer the question: how many intelligent civilizations in our galaxy are trying to communicate with us?

Here's the equation he came up with:

N = R* × fp × ne × fl × fi × fc × L

Where:

• N = The number of civilizations in our galaxy with which we might be able to communicate

• R* = The average rate of star formation per year in our galaxy

• fp = The fraction of stars that have planetary systems

• ne = The average number of planets that can potentially support life per star with planets

• fl = The fraction of planets that actually develop life

• fi = The fraction of planets with life that develop intelligent life

• fc = The fraction of intelligent civilizations that develop technology to communicate across interstellar distances

• L = The length of time such civilizations release detectable signals into space

Today, we know a bit about two of these values: the rate of star formation in the galaxy is fairly well understood, and we are starting to get a good idea of the fraction of stars that have planetary systems (it’s very high!). Encouraging!

Unfortunately, we don’t have any idea at all about what the rest of the terms could be. Since we know of exactly one planet that has actually developed life, we can’t assume we have any real idea about the fraction of planets that develop life. We certainly don’t have any idea about what fraction of those planets will develop intelligent life, and it gets even more speculative from there.

The Drake equation is a useful thought experiment. It lays bare what we need to know in order to determine how much intelligent life is out there, and one day, it might be possible to start filling in the blanks. It provides a good framework for thinking.

Just because there’s an equation, does not mean we understand how to come up with the answer.

Nobody knows exactly what memories are.

We know that memories are malleable—your mind does not conjure up a videotape or photograph of an incident you remember, so your memory might not be consistent with what actually happened. They can be reshaped over time, and you can actually form new memories that didn’t even happen.

We do have a good idea of how memories are formed, too. When you see, hear, touch, taste, or smell something, this information is encoded into a useful format your brain can then use. Connections between neurons are strengthened every time you trigger a similar combination, so repetition plays a big role in memory formation.

Whenever you remember something, this is your brain recreating the same neural pattern you had when you experienced the thing you’re remembering.

So far, so good! But here’s a bunch more stuff we really don’t know:

• Where are these memories stored? Is there one set of neurons where there’s something akin to a record of what happened, or is there some kind of decentralized method of storage, so the memory is throughout the brain?

• Why aren’t memories actual copies of the events, but instead summaries that are subject to change over time?

• How do longer term memories stick around at all?

Nobody knows, and that’s exciting.

Nobody knows how time works, or whether it’s even a real thing.

You’re thinking, that’s crazy! We know how to measure time, so we clearly must know what it is. This is where we have to be careful: like with the Drake equation, you can make something you know nothing about sound like you’ve got it all figured out.

Time isn’t what it looks like to us at our human scale. Einstein famously described that simultaneity is a myth: two things only happen at the same time according to one point of view, but if you move somewhere else, one thing happens before the other does.

To us, it feels like we are living through a flip book, where one second is flipped and the next immediately follows. Is this fundamental to the universe, or is it the way our brains tell us what’s happening at a given moment, the way they make sense of the world?

Given that we can form memories in order to help us make sense of “the past”, is it possible that our brains make up the concept of linear time?

Time sure seems to operate more like a dimension of space than a separate thing, and Einstein coined the term spacetime to point out that they’re not actually two separate concepts, but instead are dependent upon one another. Even more perplexing: gravity can warp spacetime.

One person’s experience of time can be completely different than another person’s experience. At the quantum level, it’s even weirder: a particle can exist over here and over there all at once, and there are even questions about whether cause always comes before effect.

These aren’t comprehensive categories by any measure, but I wanted to balance my enthusiasm in being able to find answers with the reality that there’s still plenty we don’t know, even if you know how to search all of human knowledge.

What are some of your favorite unsolved mysteries?