Lawrence Krauss - Why aren't Aliens Already Here?

It seems absurd in a universe with 100 billion galaxies, each with billions of stars and planets, that we are the only intelligent life. So where are all the others?

[stenkarasin]

Not to mention that we only appeared a moment ago by the standards of the universe, maybe they just haven't had time to notice us yet.

[duncanwallace]

Lawrence didn't mention time. A civilisation could arise, spread and then go extinct and in the vastness of time 'miss' another civilisation which arises in a similar area a billion years later. Understanding the vastness of space and time is hard. One thing which brought it home was the video game Elite Dangerous, which has been out for around three years, and is based on our galaxy. With thousands of players exploring and the ability to 'warp' hundreds of light years in a short time, over 112.8 million unique star systems have been discovered by players in the three years the game has been out. That represents 0.028% of the milky way... and we're just one of billions of galaxies. So yes, civilisations could easily miss each other across space and time.

[tmfd]

A tribesman on an island then could say “if there’s all these high tech and foreign people, why haven’t I seen them?” There needs to be a reason for others to go there.

[wayneasiam]

I remember a few years back when the esteemed Dr. Krauss responded online to one of my conjectures by saying... wrong, wrong and...wrong. Priceless.

[cato]

I often think I am an alien because I feel like an observer to the idiocy on this planet.

[jeffdunlap]

If you could even manage to get a large space craft to go 1/10th of the speed of light, and assuming there is no advanced life in this galaxy, but there is in the Andromeda galaxy, it would only take you 25 million years to get there. Keep in mind that the Aliens have to follow the same laws of physics we do. No free rides. It's all about distance, physics, and evolution, and the fact that super intelligent beings are rare and separated by uncrossable distances, no matter what they are capable of building. We keep assuming that the universe was somehow created for us. It wasn't, we just happen to be here..

[Jeremy-qlor]

It seems like the most likely explanation for "Why haven't we seen aliens" is that interstellar travel simply isn't possible. Even a super advanced intelligence might not be able to make a vehicle that can travel to other galaxies.

[zerge]

Aliens are already here. Let's stop pretending they are not.

[renevalice]

never forget how vast space is- even light at its speed, becomes old and ancient as it travels throughout the cosmos.

[larkstonguesinaspic]

I don't know man Space is really big and there isn't much chance that we hear about or meet other civilizations in the galaxy. It just requires too many resources and too much energy to travel distances between stars. And also we haven't been looking for them for that long either. We humans existed on small portion of earths history and even recorded much much smaller part of it. And we've been only listening for signals 70 years or so. And in terms of Space exploration our Voyagers just got out of the system and humans only went as far as the moon.
So what I mean is we basically took a glass of water out of the ocean, looked at it and said " well I don't see any sharks or whales so where are they why aren't they here "

[comedycopter]

Is The person on the left, interviewing himself 20 years in the future?

[raymondparsley]

Krauss is correct and honest in saying: ''Even if there's life out there, we can never know about it... and that's sad to me." This, of course, speaks to the vastness of space... which also makes communication with "aliens" virtually impossible. Our real interest and challenge as humans, it seems to me, should be that of exploring, and possibly colonizing our own solar system.

[John-tcgp]

A scientist willing to _believe_ anything without evidence is a poor scientist

[NormBa]

The question is plagued perhaps by some anthropomorphisms. Why would aliens, if they existed, necessarily be in possession of 'human curiosity' or an expansive communitarian spirit? I think we have a speciated term again: human outreach. Krauss makes an interesting point about all evolutionary endeavors not necessarily pursuing advancing intelligence. Could some environments be so hostile that intelligence is a hindrance. Arguably one definition of intelligence could be an organism's adaptation to its environment. I'm thinking too of Don hoffman's suitedness as opposed to veridicality or aptitude.

[TheGreatAlan]

There are so many stars that even if the odds of life were a billion to one, that means there would be millions of planets with life

[jamesruscheinski]

There are probably around 1 million intelligent alien civilizations in galaxy that are not technologically advanced and may never be, possibly for reason not to destroy themselves technologically; for which reason without technology very difficult for us to find.

[ableVelo]

Very weak argument Krauss. Very weak.

[jeffdunlap]

At 1/10th of the speed of light a grain of sand would cause a space craft to blow up

[ThatOneScienceGuy]

I can barely contain my excitement when I think about the possibility of not only finding one other life form out there but dozens. To think that we could at some point have a kind of interstellar multi civilization sort of thing going on is just mind bending. We’re so alone here as humans. I’d love to come into contact with other civilizations and get their opinions on the nature of reality and what they think about this universe we’ve evolved in. If they’re more advanced than us I’d love to learn about what they’ve learned about the universe.

[drbonesshow]

Lawrence Krauss reminds me of the revelation: a turd rolled in coconut is still a turd. Forgive me, I'm a physics professor doing real physics.