- Is there anyone out there?

Hello?

It's an age old question, do aliens exist and what are the odds that we will make contact?

There's actually a famous mathematical equation that could help.

(upbeat music) The Drake equation is used to help calculate the odds that advanced alien civilizations exist in our galaxy.

Over the years, scientists have proposed ways to update it, to reflect new discoveries like exoplanets and get closer to answering the questions, are we alone and will we ever know for sure?

So N in the equation stands for a specific kind of advanced alien civilization.

Those that have the technology to produce radio signals detectable by earth.

But there may be civilizations out there that don't communicate with radio waves like we do here on Earth, or maybe they are just so far away that we can't detect their signals.

Then on the other side of the equation are all of the ingredients for advanced civilizations as we understand them.

R star is the average rate that star suitable for the development of intelligent life form in our galaxy, and F sub P is the fraction of those stars that have planets around them.

This number has been updated in the last couple of decades with the discovery of exoplanets, but for now, the rest of the terms are estimates, impossible to measure because we just really don't know how many other planets have life, let alone intelligent, advanced life.

So if most of these terms are estimates, then there's no definitive answer to the Drake equation.

So why is this equation useful?

Well, because it's a framework.

We have to start somewhere.

It's like a guideline for researchers to know what to look for and what to study to find life beyond earth.

But one of the key pieces scientists really do wrestle with is the number of planets where life could become intelligent.

That's F sub I in the equation.

And here's why.

The Drake equation assumes its simple forms of life, like microbes inevitably evolve into complex and intelligent life.

But others think that the jump in evolution from single-celled organisms to intelligent life is not inevitable.

And some even think that at an important factor for how life on earth evolved to become intelligent and technologically advanced might have to do with something you probably learned about in grade school, plate tectonics, oceans and continents.

They argue that these things are so important that new terms should be added to the Drake equation.

But why?

What do plate tectonics have to do with the evolution of advanced civilizations?

Today, Earth's crust is made up of massive plates that sit on top of the hot molten rock mantle.

But billions of years ago, there was just one massive plate that broke apart as the mantle heated and cooled, forming mountains and volcanoes, creating diverse habitats, recycling nutrients, and regulating the climate.

The movement of these plates is known as plate tectonics, and some scientists think that complex organisms on earth emerged on the ocean floor not long after plate tectonics started.

Some researchers think those factors made it possible for life to evolve from the sea to the land, which was key for intelligent life developing technology.

But at least so far, we don't know of any other planets that have plate tectonics like we have here on earth.

(buzzer buzzing) So factoring that into the Drake equation dramatically lowers the odds of other advanced alien civilizations.

By that calculation, we may be the only advanced civilization in the galaxy, but there's a lot we don't know about how life evolved to become intelligent.

We really only have one example to study, Earth.

(bright music) It may be that there are factors that we haven't even thought to consider yet, totally unrelated to plate tectonics, and actually that's a limitation of this whole thought experiment.

We just can't account for things we haven't even thought to consider.

But maybe one day the researchers listening for extraterrestrials will hear something, and if so, hopefully whoever is out there will live long enough for us to make contact.

Ever hear the Fermi paradox?

(bell dinging) It may be that it takes so long for any kind of signal to travel to us or vice versa, that the civilization on the other end may no longer exist to receive it.

- [Computer] You've got.

- And that's L in the Drake equation, the average length of time civilizations exist to make such signals.

So what do you think?

Are we alone?

Does the Drake equation need a revision?

Will we ever find the aliens?

(upbeat music) (soft music)