Where is everyone?

We've been searching for decades, but haven't found so much as a microbe in space yet. Could it be that we're early; that life simply has not evolved yet in the neighbourhood? Are we doing it all wrong? Is there a bustling universe of sentient beings out there, waiting for us to catch on? Humans are now beginning to build technology that could make the difference in our quest for alien life. We have a growing understanding of what to look for. We're getting better at sending probes to nearby planets, which could tell us more about where and how to search. What might we find? Why does it matter? Take a look

- Anesha George

There's a space-age joke about a man who has lost the keys to his car. He keeps looking beneath the nearest lamppost. Asked why, he replies: "It's where the light is.

For millennia, we have gazed up at the stars, haunted by the question: Are we alone? Our means of answering that question have remained frustratingly limited.

To extend the metaphor of the joke, we've been looking where the light is; where we are. Unlike in the joke, though, we aren't even sure the keys exist. (Though we're reasonably sure they should.)

We don't know where the street leads, what's in the next district, or indeed how we got to the lamppost to begin with.

It's a muddle.

Are we now set to take the leap that could help us un-muddle it? We have the technology to see further. We have a clearer understanding of what to look for.

The James Webb Space Telescope (JWST; built by the space agencies of the US, Europe and Canada), itself revolutionary, is already being overtaken by planned space telescopes that will have mirrors far larger than its 6.5-metre one.

Back on Earth, we are using lab simulations and computer simulations to help narrow the list of biosignatures to look for and conditions that could indicate life, either surviving or long-extinct.

"We started to reach for other stars in 1995 and we now know that there are 200 billion Sun-like stars in our galaxy alone, shining with billions and billions of possibilities," says Lisa Kaltenegger, an Austrian astrophysicist and astrobiologist, founding director of the Carl Sagan Institute at Cornell University, and author of Alien Earths: The Science for Planet Hunting in the Cosmos (2024). "At this point, it would be a bigger surprise to learn that there isn't life out there, than to learn there is."

What might such life look like?