…that, say 2.5 billion years ago on Earth, an entire race of intelligent beings evolved, got civilized, sent off satellites into outer space, then got wiped out by some utterly huge event, so that no trace of them can ever be discovered? Does the present argument that signs of life began around 2 billion years ago exclude any such possiblility?
It’s possible, yes, although we would have to revise some things we think we know to quite a high level of certainly about history, archeology and a few other subjects.
Is there any evidence to support this view? None has yet been found. Is it a reasonable conjecture? There is no basis to think so at the moment. Are we entitled to regard it as extremely improbable? Yes.
Welcome to the Straight Dope Message Boards, curiousGuy, we’re glad to have you here. I’ve edited your thread title slightly, to help readers understand whether they’re interested. You might want to check out the Rules, Guidelines, and Etiquette – this one is under “Etiquette”: please use descriptive thread titles.
No biggie, you’ll know for next time.
It’s certainly logically possible, but the current thinking is that some sort of life existed even before the late heavy bombardment, which started 3.9 billion years ago, give or take a few weeks. .
Factual answer - sure it’s possible. Why on earth would you need a message board to answer such an open ended question?
Well, the OP postulated that they got “wiped out by some utterly huge event, so that no trace of them can ever be discovered”. So of course no evidence has yet been found; no evidence could ever be found. 
I’ve often wondered if an intelligent race evolved during the Dinosaur periods.
Fossil remains generally are found in amazingly small numbers and many created objects would leave no trace after all of this time.
I stress that this is pure musing on my part and not being put forward as my personal belief.
It’s possible that there are invisible space aliens living in an incorpereal space ship parked right over the White House. We just haven’t developed the technology to detect them.
I do wonder sometimes–if there had been cities like modern New York City built, say, two billion years ago, is it likely that there would be no trace of them left at all?
It’s basically the same as asking how long it would take for all traces of our own civilzation to disappear if all the people disappeared today.
I remember there was some book about this latter question, I never read it though.
There’s been a few threads on that here too, but I can’t find a good one at the moment. But 2 billion years is orders of magnitudes more time than is needed to erode away pretty much everything humans have ever built or made up to now. The oldest building that’s sort of standing now is is only about 5500 years old.
I have a recurring nightmare set in about the year 3000: while dredging a harbor, several huge, badly corroded metal frameworks sunken into the sandy bottom are discovered. A fringe historian claims they’re the launch towers used by the “astro-nauts” who, according to myth, ascended to the moon in small “capsules” mounted on top of huge furnaces that burned a highly flammable substance derived from fossilized plants. The historian is roundly denounced as a crank by all reputable sources, who remind people that the astro-naut stories were never meant to be taken literally and that humans cannot travel beyond the atmosphere until several major scientific breakthroughs occur.
We find fossils going back to 2.5 billion years ago, though. You’d think if we can find the bodies of prokaryotes from billions of years ago, modern space-age technologies would also leave some remenant, even if standing buildings ceratinly wouldn’t last.
Also, intelligent does not mean technological. If there were intelligent dinosaurs at the level of homo sapiens circa 100,000 BC, there would be very slim chance we would ever find convincing evidence.
Well, if the ancient society made anything out of bronze, it might have survived. Finding a bronze artifact in a pre-jurassic strata would be pretty impressive. Of course, finding some exotic plastic or ceramic (such as I assume a space-faring race would need) would be more so.
Of course, as other posters have pointed, one can speculate on literally anything, if one is conveniently indifferent to having any actual evidence.
What about space debris in orbit or on the moon? Would it even be possible for some piece of junk to maintain a stable orbit for that long? Have there ever been any searches to look for, say, discarded 7-fingered space gloves?
If they were a race like human beings there would be signs of their existence. As Bryan Ekers wrote, some materials can only exist if they are made artificially but once made will last for billions of years. If you find a billion year old sample of such a material then you know a technological civilization existed that long ago.
You could probably also deduce the absense of a technological cilization by noting the existence of natural resources in their unprocessed state. A technological civilization would have dug up and used useful metals and minerals that were easily accessible. If those materials are still in the ground, then nobody must have been around to process them.
I’m not sure on either of these scores. I’m not confident that any material would survive intact enough to be recognizable for that long, and processed materials would have plenty of time to be de-processed.
Satellites, however, probably would last long enough. Most satellites are in low-Earth orbit, which will decay from friction with traces of atmosphere within a human lifespan, but they would surely also have had use for geosynchronous satellites as well, which are high enough that they’ll last until the Sun engulfs the Earth. Their geosynchronous satellites wouldn’t be at the same height as ours, because the rotation rate of the Earth has changed, but they still wouldn’t be all that hard to spot.
This is a much riskier assumption than your first one: you’re reasoning from a sample size of one about all possible civilization-creating races. There are groups of people even today who don’t use much metal, plastic, or glass; go back a couple hundred years and there are lots of them. Add a couple cultural or religious taboos against tampering with the Earth-God, and you’ve easily got civilization that uses only biodegradable materials. Steam-era technology is certainly possible in a wood-based world (although there’s no evidence trees had evolved back then, either), and possibly later technologies that we haven’t developed because we don’t have the need.
to C K Dexter Haven
sorry about that, won’t happen again.
I am not asking whether evidence might be found. Not on Earth anyway, because the kind of destruction I am talking about is where all of the near-surface stuff gets molten and reduced to their basic elements.
(Some lost satellite sent by them, homing in back to Earth would be nice :))
My point was more along whether a possibility of such intelligence (of the space-faring type) can be ruled out, and was there enough time for this to have happened before the timeline of current theories of when life in any form started?
How about exotic isotopes or elements? If our advanced civilization started messing around in nuclear physics, that is.