For Scientific American Science Quickly, I'm Rachel Feldman.

On November 16, 1974, humanity sent an unprecedented message into the stars.

If we go as far away as Mars or the other planets and look back, even with a powerful spacecraft, is essentially

impossible to know of human life on Earth.

But now, like this radar transmitter, the Earth is exceedingly visible.

That was the voice of Frank Drake, a late astronomer and astrophysicist who was instrumental

in sending what's now known

as the Erecibo message. Here to tell us more about humankind's first attempts at finding

intelligent life in the cosmos and what's changed in the last 50 years is freelance science

journalist Nadia Drake. Nadia, thanks so much for joining us today. Thank you. It's good to be here.

Let's start with some basic context for our listeners.

What was Erecebo and what anniversary are we talking about today?

The Erescebo Observatory was formerly the world's largest radio telescope.

And that was until China built their bigger radio telescope more recently. But

for many years, it had been the largest telescope on Earth with a dish that spans a thousand

feet. And it had a very powerful radar, a transmitter that they used to study bodies in the

solar system, actually. In 1974, the observatory had just finished doing some

upgrades to the facility that were going to turn it into a world-class observatory for astronomy.

One of the things they did was they replaced the reflector dish for the telescope and gave it a

surface that would let it make observations at frequencies

that were really useful for astronomers. The other thing they did was that they upgraded the transmitter

and gave it more power. And to commemorate that upgrade, they decided to have a dedication ceremony

...