[Intro]

[Savannah]: In 1982, an alien made its way to Earth and into our hearts. After 40 years, E.T., the extraterrestrial, remains a celebrated classic movie shared across generations. And while we're so happy to have E.T. on our tvs, we're still waiting for any real aliens to stop by. 

Some researchers have even gotten a little impatient in the wait and sent out beacons to let them know who and where we are. Okay, maybe they didn't send out the messages because of the movie, but those messages could be the first step to making it more of a reality. Here's what those messages looked like.

[Hank]: In the 1970's, if you wanted to describe life on Earth in a simple way, you probably knew who to ask, astronomers Frank Drake and Carl Sagan. Both were involved in astrophysics research and education, and Sagan had been consulted on NASA missions like the Venus Probe Mariner 2.

But when NASA was finalizing its plans for the Pioneer 10 and 11 missions, the first two spacecrafts to pass through the asteroid belt, Sagan proposed a plan which a journalist had suggested to him. Attatching a message to the probes explaining who we are and where we live in case they're ever found by another civilization. And NASA agreed.

Over the next few years, the two scientists put together three landmark representations of the human race, the first time that anyone had intentionally created messages to be sent outside the solar system to be read and interpreted by extraterrestrial life. 

Two were physical messages using NASA probe's couriers. The other one was more of a crafty mathematical code for aliens to crack. But all of them were attempts to describe ourselves to being who would have no concept of Earth, or humans, or even just simple units of measurement like meters or seconds.

We know the odds of these messages being detected by another civilization are very small. They'd have to find a small probe flying through space or be listening to exactly the right frequency at exactly the right time, but they sent them anyway.

Pioneer 10 and Pioneer 11 launched in the early 1970's and each carry a copy of the same plaque meant to explain where they came from. For anything on the plaque to make sense, Drake and Sagan realized they needed to use a universal language: science.

So, to describe length, the plaque uses units based on the energy change that occurs when an electron and a proton and a hydrogen atom switch the way they spin, since it has a diagram of the transition they hope that any space-faring civilization would understand what they were talking about.

To explain where the Earth is, they included a pulsar map. The map shows the Earth’s location among fourteen different pulsars: stars that regularly emit bursts of electromagnetic radiation, almost like beacons.

The plaque also includes other details, like pictures of humans standing in front of the probe. Which is kind of weird, because now the whole universe knows what we look like with our clothes off.

But when it was time to launch the Voyager probes a few years later; Sagan, Drake, and their team were a little more ambitious. Instead of just a plaque, the Voyagers carry with them copies of the golden record, the kind that plays music. Forged from gold-plated copper instead of vinyl.

The record’s cover contains basic information like the hydrogen and pulsar diagrams, plus some illustrations that explain how to play the message on the record. Once the alien recipients figure out how to build a record player, they’d be treated to sounds from all around be Earth, including greetings in fifty five languages, from extinct Sumerian languages to modern Chinese dialects. That’s followed by ninety minutes of different kinds of music throughout the world and throughout history, and a host of natural sounds like birds chirping, whale songs, wind, and thunder.

Finally, 116 images are included on the discs, intended to explain nearly every conceivable aspect of life on Earth: photos of plants and animals, different landscapes, illustrations of humans in various stages of life, diagrams of our sex organs, and demonstrations of how we drink water and chew food, lick ice cream cones.

So that was Sagan, and Drake’s attempt at creating a kind of encyclopedia of life on Earth.

But they also included a third kind of message; and all it really said was, “we are intelligent, and we’re here.” For this message, they didn’t use a physical representation; instead, they tried radio waves. In 1974, Sagan and Drake put together a code to be transmitted by the Arecibo Radio Telescope in Puerto Rico, which was undergoing some upgrades. The data was sent in binary, like in computers, but instead of being ones and zeroes, the information was encoded as two different radio frequencies.

It took 1679 radio signals to transmit the message, which was a deliberate number: it’s the product of 73 and 23, two prime numbers. And when you organize those signals into a 73 by 23 rectangle, it looks like this, except that there weren’t actually any colours in the actual message, they were just added for clarity.

Those white dots at the top represent the numbers one through ten. The purple dots are the atomic numbers of the most important elements for human life: hydrogen, carbon, nitrogen, oxygen, and phosphorus. The green blobs are the formulas for the building blocks of DNA, and those blue strings are meant to be DNA’s double helix.

Some of the other information in the data are pictures of a human, our solar system, and the Arecibo telescope.

For three minutes, the telescope sent the message toward the M-13 globular cluster, 25 000 light-years away.

They only picked that cluster on the night of the observatory’s reopening ceremony, and that’s basically where it happened to be pointed.

By the time the message gets there the cluster won’t even be in that spot anymore, because it will have moved on in its galactic orbit. So it’s unlikely that we’ll ever get a response, even if we wait 50 000 years.

Since then, we’ve broadcast lots and lots of other messages at likely looking star systems, though we haven’t yet heard back.

But I think at least we’ve learned a little bit more about ourselves in the process.

—

So we’ve sent a bunch of messages into space for extraterrestrials to receive. The gist was mainly: “I’ll be right here”.

But since ET hasn’t shown up in suburbia yet, those messages might need some refining. So we’re trying again. Here’s what we changed this time around.

—

In humanity’s search for life in the universe, we’ve done a lot of looking, and a lot of listening. But to maximize our chances of connecting with extraterrestrial life, we can’t just sit back and wait: we need to reach out, and try to make contact ourselves.

For more than half a century, we’ve begun doing just that. But many of these early attempts were more symbolic than practical.

Now, in a paper published in the journal Galaxies, a team of American and Chinese researchers propose a new message aimed at improving its chances of being received and understood.

While the odds of success remain unfathomably small, the project is helping to refine our notion of who we really are, and what is truly universal. There are basically two ways of sending a message to the stars: either in physical form or through a radio broadcast. In the 1970s, scientists experimented with both. The pioneer plaque and voyager golden records were physical objects attached to the first spacecraft launched on trajectories that would take them out of the solar system.

Each contained basic information about Earth and a map pointing the finder back towards our solar system. But it was all symbolic: contacting alien life wasn't the mission's goal, and none were aimed at a nearby star.

In theory the so-called Arecibo message sent in 1974 improved on that. Transmitted by the Arecibo Telescope it was sent at the speed of light, towards M-13, a cluster of three hundred thousand stars.

That message, though, turned out to have been more of a publicity stunt than an actual communication attempt, because by the time it reaches its targeted point in 25 000 years, M-13 with be elsewhere in the Milky Way. The newly unveiled project, called Beacon in the Galaxy, aims to improve on these previous efforts.

A key focus is on improving the odds that a message is properly interpreted, if it is actually received by intelligent life.

That might sound hard, but evidence suggests it's probably even harder that we think.

When one of the creators of the Arecibo message circulated a draft to some of his friends, including a number of Noble Prize winners, not one successfully understood what it meant. And they were humans!

One strategy employed by the Beacon message is to remove as much extraneous information as possible.

The Voyager Golden Record was full of things meant to evoke a sense of life on Earth: photographs, songs, spoken greetings, and the sounds of nature. But without any context, these would be virtually impossible for any alien life is to understand. Worse, they could prove to be distractions from more important messages, like where Earth is located and when the message was broadcast.

The beacon also relies on a special alphabet designed to be resistant to the breakdown of signals radioed across huge distances. That way, a simple transmission or decoding error doesn't turn ones into sevens, or threes into eights.

These symbols were first developed as part of a prior extraterrestrial communication attempt broadcast from Ukraine in 1999 and 2003.

Like previous messages, the actual beacon signal would be a stream of binary ones and zeroes, designed to be converted into simple pictures containing the information.

To make sure the transmission is as clear as possible, the authors calculate when and where the message should be sent. Broadcasting around March 30 or October 4 with reduce interference from the Sun's own radio energy.

At the same time, the target should be as close to straight overhead as practical, in order to minimize the amount of distortion from Earth's atmosphere.

One final improvement proposed for the beacon message is a update to our galactic map. The messages in the 1970s specified Earth's location to 14 nearby pulsars, neutron stars that send out perfectly repeating bursts of radio waves.

Since then, scientists have realized that pulsars might not be the best choice for a universal map. For one thing, their unique pulse is only visible if you are in the path of its lighthouse-like beam.

They're also not terribly bright, and their positions drift slowly around the galaxy just like other stars.

For those reasons and more, the beacon's map is made up of globular clusters instead.

Composed of hundreds of thousands of stars, these dense clusters shine in all directions and are bright enough to be seen from virtually anywhere in the galaxy.

There's also fewer of them in the Milky Way, making it easier for ET to match the map to known objects.

So given all of this planning, when will the beacon message be sent? Probably not any time soon.

With the Arecibo Telescope no longer operating, the authors propose sending the message from either California's Allen Telescope Array or China's enormous Fast Radio Telescope.

There’s just one problem: neither of these facilities have the equipment needed to broadcast a signal. They are designed to only listen. Upgrading either would be possible, but it’s a big undertaking that will require major financial investment. But that does not mean that the Beacon of the Galaxy is an entirely abstract exercise. Working out how we might communicate with other intelligent life helps scientists recognize what aspects of our view on the universe are actually universal.

And hey, if ET does come knocking, projects like this one gives us a solid first draft of what we might say.

—

We’ve had a few drafts now for what we would say to ET if we could. But we haven’t just kept them in our email drafts: we’ve sent them, in case any aliens might respond.

But the closest thing we’ve got to a response so far is the ‘WOW’ signal. Here’s Caitlin to describe what that looked like.

—

Deep within an archive in Columbus, Ohio, there’s a slip of paper with a bunch of random-looking letters and numbers printed on it. A few of the characters are circled, and one part is hand-written in red ink: “WOW!”

Those circled characters are the signs of an unusually strong signal from outer space, detected in 1977. But we still don’t know exactly what it was, and we never found it again.

There’s a theme that tends to come up a lot when you’re talking about space. With so many planets and moons scattered throughout this universe of ours, where are the aliens?

So some astronomers have spend their time looking for extraterrestrial life. By broadcasting carefully crafted messages to space.

But what if there’s intelligent life out there that’s doing the same thing, sending messages to us? Or even just broadcasting signals that we could pick up from here?

That’s why other astronomers and some entire organizations spend their time looking for alien signals using radio telescopes.

Lots of things in space naturally emit radio waves, and radio telescopes are designed to capture, focus, and read that energy.

By analyzing the data collected by these radio telescopes, researchers can learn new things about the universe. Like where there might be undiscovered galaxies.

But organizations like SETI, or Search For Extra-Terrestrial Intelligence, also like to monitor the data. They’re looking for something out of the ordinary, like patterns or especially strong signals, that might mean they were sent out, purposefully or otherwise by an advanced civilization on another world.

These days, we can comb through the data automatically using computers. But back in the 1970s, it was done by hand, which is where a volunteer named Jerry Ehman comes in.

A computer hooked up to the telescope would print out the data collected as characters arranged in a grid. And on August 15th, 1977, Ehman was looking through some of these printouts, when he saw a sequence of characters that meant that the telescope had detected a signal thirty times the strength of the usual radio background waves; a signal that went on for 72 seconds.

38 years later, we still don’t really know what is was. Once Ehman found, and accidentally named, the ‘WOW’ signal, scientists wanted to see if they could find it again. They were able to narrow down the possible sources to somewhere in the constellation Sagittarius, possibly near the M55 star cluster, but never detected it again.

So where did the signal really come from? Scientists aren’t sure.

For one thing, it could have been was a computer glitch, but it probably wasn’t, because the signal wasn’t the sudden, constant spike in the data you would expect to see if it was just a glitch. Instead, it gradually rose to a peak, then fell again as the telescope passed a certain area of the sky.

It also could have been caused by something natural, like a pulsar: a rotating star that sends out beams of radio waves in pulses. But then, astronomers would expect to see the change through a lot of different radio frequencies. Instead, the ‘WOW’ signal was only detected on one channel, and a special one: 1420 MHz. The same band that’s naturally emitted by hydrogen. If you want to send a message that says, “Hey, there’s intelligent life over here,” picking the same frequency emitted by the simplest element in the universe is a pretty good way to do it.

In fact, it’s such a strong possibility that extraterrestrial life would use that band, that using the frequency on Earth is illegal under international law.

Nobody wants to get all excited about a possible message from aliens, only to find out that it was a local radio station broadcasting the nightly news.

In 2012, on the 35th anniversary of the detection of the WOW signal, the National Geographic channel decided, as part of a promotion for an upcoming TV series, to use the Arecibo Observatory for in Puerto Rico to send what they called a 'reply' to the WOW signal.

They compiled all sorts of messages, like tweets from the public and videos from people like Stephen Colbert and Leila Lopes, who was Ms. Universe at the time.

Then they sent them to the places the WOW signal might have come from. But space is big: even travelling at the speed of light, the message still wouldn't have gotten there yet.

Proxima Centauri, the closest star to our solar system, is about four lightyears away. The M55 cluster, on the other hand, is more like 17 000 lightyears away.

Even it there is someone listening, and they decide to reply, it will be a future generation of scientists that get to hear the reviews of Stephen Colbert's sense of humour. And until then, or until we detect more clues, the WOW signal will remain a mystery.

—

The WOW signal was detected after we sent that first beacon, but it seems like it would take way longer to receive our message and respond to it. So, odds are that's not what it was.

If you want to know the real odds of getting a message or visit from ET, Reed can tell you how to calculate them.

—

In 1960, a young astronomer named Frank Drake sent radio waves into space. Hoping to make contact with an alien world. His signal was never answered, but it was the first modern search for extraterrestrial life.

Twenty years later, Drake became one of the about first members of the Search for Extra-Terrestrial Intelligence, or SETI institute, and they've been combing the stars ever since.

Okay, so where are my aliens? Could there be other creatures sending signals for us to find? Or, could we look forever, but never find anything, because we're the only ones here?

Only a year after his first experiment, Frank Drake proposed the Drake Equation, to estimate the number of alien civilizations in our galaxy sending signals we can detect. But we don't yet know enough about the universe to solve the Drake Equation.

In the meantime, it is a useful way to think about the odds that there are other intelligent species out there.

To figure out how many aliens live in our neighbourhood, Drake had to first decide on what factors contribute to the birth of intelligent life. He eventually decided on seven.

The first variable was R*, the number of stars born each year that could support life. Life probably won't evolve around stars that are too cold and dim, that are unstable, or that burn too quickly.

The best habitable stars seem to be stars like our sun, which have been stable and bright for billions of years.

In the decades since the Drake Equation was developed, we've learned that about one of these stars forms in our galaxy every year.

Drake then considered the fraction of life-friendly stars in our galaxy that have planets, F sub P, and the average number of planets in those solar systems with environments that could support life, or N sub E.

In other words, planets with liquid water and an oxygen-rich atmosphere. By measuring the brightness of different corners of the sky and using statistics, astronomers have figured out that there are between one hundred and four hundred billion stars that could support life in the Milky Way galaxy.

With data from the Kepler Space Telescope, which was built to study Earth-like planets outside our solar system, they could go even further and estimate that the number of habitable planets in our galaxy between forty and forty-nine billion.

Now here's where things get tricky: while we have rough estimates of the first three variables of the Drake Equation, the last four are a little more complicated.

Drake's fourth variable, F sub L, was the fraction of those habitable planets with life. The next variable is the fraction of those planets with intelligent life, F sub I; and the fraction of those intelligent civilizations that are broadcasting signals into space, F sub C.

Finally, there's L, the length those civilizations have been broadcasting.

Even signals travelling at light speed can only go so fast. So, if a distant planet hasn't been broadcasting very long, there's a chance the signal may not have had time to reach us here on Earth.

According to Drake, by multiplying those seven terms together, you get N, the number of alien worlds broadcasting messages we can detect from Earth right now.

The problem is we've never found life on a planet besides Earth, so we have no idea what fraction of the billions of planets in our galaxy have life, let alone intelligent life.

So until we find ET, we won't know what those last four variables should be. And even some of the numbers we do have are based on life as we know it here on Earth.

There could be creatures that thrive in toxic atmospheres or that can't stand water, which would totally throw off our guesses.

But that's okay, because the Drake Equation isn't designed to have an answer; instead, it's a tool to help us think about how alien life might exist.

It helps us think about what life off Earth could be like, and our odds of finding it under different conditions.

Like, in a paper published in May of this year, in the journal Astrobiology. In the paper, two researchers rewrote the Drake Equation so that instead of asking "What are the odds we can find intelligent aliens right now?", it asks "What are the odds humanity is it only advanced civilization to have ever existed?"

They considered only two variables: the things we know, and the things we don't know. Their first variable, the number of habitable planets in a given corner of the universe, takes into account what astronomers have learned other the past fifty years. Their second variable, the odds of finding an intelligent civilization on one of those planets, covers everything we still don't know.

Using this version of the equation, the researchers concluded that humans aren't the first intelligent species, unless the probability of intelligent life evolving is less than one in ten to the twenty-four.

That's a one with twenty-four zeroes after it, or a trillion trillion. While we don't actually know the odds of intelligent life evolving — they could be much higher or much lower than a trillion trillion — their analysis is another way of helping us consider one of humanity's most basic questions: "Are we alone?"

—

So we're still waiting for ET to show up, or even phone Earth from home. But we haven't given up hope. We're still sending messages into space and looking for life in the wildest places.

To hear about some of that search, you can watch the Sci-Show space video that takes you through five unusual places we're looking for life.

And if you really want to be good you can go to https://patreon.com/scishowspace to learn how you can support this channel. Thanks for watching.