No ET! Ever?

[Aoi Magi]

That is why it's better for civilizations to take out others quickly.

[ignoramus]

There is also the possibility that close to light speed travel is an impossibility.
Maybe, many before us have tried to no avail, hence the silence.

[The Valkyrie]

I personally think it's naïve to state, frankly, that there are no other advanced life forms in the universe. Earth is 4.5 billion years old, give or take, and there are stars in our own galaxy that are much older. I, like many others have stated here, suspect the problem here is distance.

Our own galaxy is huge - billions of stars. Now add the other galaxies, and we see that the universe is much larger than we can comprehend.

[Kernel Sohcahtoa]

I personally think it's naïve to state, frankly, that there are no other advanced life forms in the universe.  Earth is 4.5 billion years old, give or take, and there are stars in our own galaxy that are much older.  I, like many others have stated here, suspect the problem here is distance.

Our own galaxy is huge - billions of stars.  Now add the other galaxies, and we see that the universe is much larger than we can comprehend.

Well said.  This thread reminds me of the following dialog  from the movie Contact (1997).  

"Young Ellie: Dad, do you think there's people on other planets?

Ted Arroway: I don't know, Sparks. But I guess I'd say if it is just us... seems like an awful waste of space."

[Angrboda]

Until we know how life began on this planet, speculating on whether it might occur on other planets seems premature. Most abiogenesis theories look for easily repeatable conditions to lead to life. If life is very improbable given the background conditions, this approach may never bear fruit. Still, it's awfully early to bet against life being sufficiently probable for such a research strategy to bear fruit.

[Edwardo Piet]

I don't believe this for a second.

And even if it's true, meh, there are other galaxies.

[Anomalocaris]

What's 'unknown' about ET not being here now ?


You hiding him in your crawlspace ?

What is known about what evidence they would leave you from having been here?

[ErGingerbreadMandude]

Nah I don't think aliens exist. We already have older planets than earth in our very own solar system. These planets already have had huge amounts of different gasses and chemicals and reactions for more years than earth. Yet, we only find life on earth.

Life is supposed to modify itself to survive in a given environment so the argument that the environmental conditions are severe in other planets falls apart, besides, severe environmental conditions relative to what?

What we see today is over 4.5 billion years of some chemical reactions just happening to take place in the right order, in the right place, under the right circumstances. So 4.5 BILLION years of just seemingly random events taking place in just the right way to give us what we see today. Can you imagine another planet undergoing the EXACT same kind of events that took place on earth down to a T? It's just awfully unlikely even taking into consideration the size of our universe.

I mean, if you have an infinite number of monkeys typing on an infinite number of typewriters you'll eventually get a Shakespeare. Maybe the Shakespeare is us?

[ignoramus]

I don't think anyone's saying they've been here, just whether they're out there at all in the first place...

[Anomalocaris]

Until we know how life began on this planet, speculating on whether it might occur on other planets seems premature.  Most abiogenesis theories look for easily repeatable conditions to lead to life.  If life is very improbable given the background conditions, this approach may never bear fruit.  Still, it's awfully early to bet against life being sufficiently probable for such a research strategy to bear fruit.

I think the origin of life reaseatch community does not on the whole hold that abiogenesis is relatively improbable. The rise of prokaryotic cells seems at the present to be reasonably probable in relatively common environments over geologically brief timescales. So the equivalent of prokaryotic cells on earth may be expected to be ubiquitous.  

Instead some seem to hold that complex organisms capable of evolution into sophisticated behavior and intelligence require cellular complexity and metabolic efficiency equivalent to eukaryotic cells. On earth no prokaryotic cell bridged the gulf to the complexity and efficiency of true eukaryotic cells even though some prokaryotic cells seems to have independently evolved features analogous to some parts of the repertoire of eukaryotic cells. As a result some Researchers have argued the development of eukaryotic cell does not easily follow from normal development of prokaryotic cells, but instead require an particular set of interplays between specific prokaryotic cells that is of much lower probability than abiogenesis itself. As a result the rise of the equivalent of eukaryotic cells, and hence complex life able to evolve intelligence, may be far more unlikely than abiogenesis,  and may be comparatively quite rare.