Could any extraterrestrial civilisation be aware of us?

We’ve been broadcasting radio signals since the beginning of the 20th century but are they being picked up?

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Jill Tarter, the former Director of the SETI (Search for Extraterrestrial Intelligence) Institute stands in front of the Allen Telescope Array, a radio telescope array dedicated to astronomical observations and the search for extraterrestrial intelligence. Image Credit: SETI Institute

Jill Tarter, the former Director of the SETI (Search for Extraterrestrial Intelligence) Institute stands in front of the Allen Telescope Array. Image Credit: SETI Institute

Asked by Sam Lee

We have been broadcasting radio signals since the beginning of the 20th century. It is thought that any civilisation with advanced technology within 78 light years of Earth would be able to pick up on this leaked radiation.

Extraterrestrial civilisations might have difficulty making use of any signals they detect. For example, TV signals would be too weak to make images from and even if they could pick up signals, extraterrestrials would not understand human languages.

If these alien civilisations launched an array of optical telescopes into space, they might be able detect the presence of ozone in our planet’s atmosphere. This might indicate to extraterrestrials that life forms are present on Earth and they are not alone.

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