Rather than searching for aliens phoning home, scientists are looking for signs of the homes themselves. A new project proposing that galaxy-spanning alien civilisations should generate detectable heat has turned up a few dozen galaxies that hold promise as harbours for life.

The best-known technique used to search for tech-savvy aliens is eavesdropping on their communications with each other. But this approach assumes ET is chatty in channels we can hear.

The new approach, dubbed G-HAT for Glimpsing Heat from Alien Technologies, makes no assumptions about what alien civilisations may be like.

"This approach is very different," says Franck Marchis at the SETI Institute in California, who was not involved in the project. "I like it because it doesn't put any constraints on the origin of the civilisation or their willingness to communicate."

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