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Where are all the Aliens? -

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Here's the thing. There are plenty of stars in our galaxy just like our sun, only billions of years
older. If alien civilisations sprung up around them, they'd be billions of years more advanced than

Dr Graham Phillips

Think about it - billions of years! Our technology's advanced incredibly in just the last few
decades... those aliens would have amazingly sophisticated spacecraft - and they would have had
billions of years to explore the entire galaxy with them. Why aren't the aliens here already?


This conundrum is known as Fermi's Paradox, after physicist Enrico Fermi. What's the solution to
it? Perhaps ET is just not that social.

Professor Lawrence Krauss

Maybe I don't want to communicate at all, maybe I realise that it's much better for me to just hang
back. I know enough I'm not interested in these primitive civilisations over there I know how the
universe works I'm kind of happy where I am - there's lots of reasons it seems to me that alien
civilisations would not immediately populate the galaxy as fast as is physically possible.


Another possibility for why we haven't made contact is that ET simply doesn't exist.

Professor Charley Lineweaver

Why would you expect to?


Charley points out, we're the only technological species to ever evolve on Earth; it's silly to
expect such beings to also evolve elsewhere.

Professor Charley Lineweaver

So there's a little bit of a projection assumption there that I disagree with. It reminds me a
little bit of the Christian missionaries who went to China looking for Christian Chinese - we're
Christian it's a universal thing so we should find them all over the place.


If intelligence were truly universal, it should have evolved more than once here on Earth. Take

Professor Charley Lineweaver

Australia was drifting independent of other continents for a hundred million years or so and the
kangaroo the smarter kangaroo didn't do better than the dumb kangaroo if it did then you'd have big
brained kangaroos hopping around here you know competing with us for radio telescope time. So based
on evidence from earth and the range of possibilities explored by life on earth we shouldn't expect
humanoid radio building people out there.


A third possibility is, maybe technology doesn't keep advancing like it has been.

Professor Lawrence Krauss

Maybe that civilisations don't expand at the expediential rate that Star Trek and all those science
fiction shows suggest that maybe that they literally exhaust their resources when they become
highly technological. Look what's happening to us.


But the most depressing resolution of Fermi's Paradox is that intelligent civilisations
selfdestruct before they get a chance to explore the galaxy. That leads to a very bleak prediction
about our future.

Topics: Space

Reporter: Dr Graham Phillips

Producer: Dr Graham Phillips

Camera: Kevin May

Sound: Steve Ravich

Editor: Andrew Scott

Story Contacts

Professor Lawrence Krauss


Arizona State University

Dr Charley Lineweaver

Planetary Science Institute

Research School of Astronomy and Astrophysics

Mt Stromlo Observatory

Cotter Road, Weston Creek

Related Info

The Fermi Paradox