I was considering the likelihood of life in the universe. I know other scientists and scholarly types have tackled the problem. I had a rogue thought that I found interesting.

The sheer size of the universe is the most often heard variable in the equation. Well, cause it's infinite. But local space is finite, subjectively so. We can only experience that which is in our light cone(Hawking). That is a finite region, hypothetically measurable.

The second variable is time. Spontaneous emergence of life is an "event", plotted 4 dimensionally, to include time with the 3 spatial dimensions. Recognition of other life by them contacting us would mean they are sapient. Life emerged on Earth around 4 billion years ago. Which means, only 10 billion years had passed since the big bang. It took nearly 30% of the current age of the universe for life to "mature" into sapience on a planet.

The first 70% consisted mostly of manufacturing all the building blocks required. Sufficient complexity requires sufficient variety in constituent compounds. The stars had to produce more complex forms of matter before complex life could emerge.

It's actually quite impressive how recently it's estimated the big bang happened, considering all that had to happen. We're out of the gates a bit early I think, so don't be surprised if competition doesn't show up for a few billion years.

On a related topic, I always thought that the evolutionary time scale seemed short to me, it seems like it would take a lot longer to reach the complexity we have (even for other animals). Which is why I understand why people are skeptical of evolution, except that their chosen alternative is that everything poofed into existence.

Still, given that it happened here, isn't the probability fairly high that it happened somewhere else, even in that finite region?

On a related topic, I always thought that the evolutionary time scale seemed short to me, it seems like it would take a lot longer to reach the complexity we have (even for other animals).

I'm sure there are stable population combinations that aren't conducive to higher intelligence. If massive lizards ruled the Earth, no amount of intelligence would be able to spontaneously develop to "overcome" them. They rule, and would eat us. Only if the game changes, and populations drastically alter, would conditions be favorable to intelligent life again. I'm not saying this is a theory or even a hypothesis, but it follows concepts from game theory. Certain environments would favor intelligence, other environments wouldn't. What the ratio is, I have no idea. In an ideal situation, sentient life may be able to develop in as little as a billion years. But it's a hit and miss process, with various plateaus and setbacks along the journey.

As for biogenesis.

The elephant in the room variable is the rarity of the event. One in a trillion to the hundredth power? Any number we throw out there is a wild guess due to the complexity of nature. My point was that we can't really get a grasp on that probability since we only have one case study; ourselves. But since our development came relatively early in the life of the universe, I would say the probability is very good. A 100 billion year old universe would have had a lot longer to spawn life, and we could reasonably expect neighbors. But at 14 billion years old, we're near the starting gates still, so even if the chance of life emerging is high, it's likely we won't see other sapient life yet. I hope we do, but won't be surprised if we don't.

I scattered some carrot seeds in my garden this morning. I know if I stay there and watch them second by second, day by day, some will sprout much earlier than others. They sprout after about 2 weeks. Watching it minute by minute, I'd be waiting there for hours and even days while one lone sprout is barely visible. It's the first amongst many. But sure enough, after another month, the growth is homogenous across the board. We don't have to "see" the event happen. Once the lifeform is mature, it's existence extends into the future.

An empty universe around us could mean 2 things. One is, the emergence of life is so rare we're the only ones around. The other is, we're the first sprout in our region and just gotta give it a few billion years(that's a single day in the analogy of my carrot). Being exasperated at not finding life "yet" ignores the fact that we may have to wait another billion years.

Interbane wrote:. . . An empty universe around us could mean 2 things. One is, the emergence of life is so rare we're the only ones around. The other is, we're the first sprout in our region and just gotta give it a few billion years(that's a single day in the analogy of my carrot). Being exasperated at not finding life "yet" ignores the fact that we may have to wait another billion years.

I was thinking something along these lines with regard to the SETI program. It does seem likely that life exists elsewhere in the cosmos, but the chances of us communicating with this other "intelligent" life (defined as life that has developed to the same technological plateau as we have) relies on many contingencies. One is that another intelligent life form has developed sentience at roughly the same time we did and another is that they will necessarily develop radio signals and beam them into space at the time that we are searching for them.

Our time on earth has been just a tiny blip, and it's certainly possible (Jared Diamond would say probable) that we will be a short-lived species. What are the chances that other intelligent life forms have emerged and are at the same technological plateau as we are at this point in time?

Another variable is proximity. I'm not sure how far into the deep reaches of space SETI is searching, but in the grand scope of the universe, we can only search a very small percentage of space.

Still another assumption is that we are at the pinnacle of intelligence and that we will be around for eons, still beaming radio signals into space. Isn't it possible that beaming radio waves is only a temporary behavior of a still-developing species. Radio waves (electromagnetic signatures) may be obsolete a couple of decades.

I saw a video once of a christmas tree with lights on it.

Using that as an analogy, imagine any individual ight being a sentient race.

The duration of the light being the length of the culture's ability to interact with other species. As in, radio communication all the way to inter-planetary travel and dare say beyond.

How often will two lights ignite at the same time, and within talking distance of one another?

We have been a sentient race for a few dozen thousand years, but have only JUST figured out telecommunications. And almost immediately afterwards we gained the ability to utterly annihilate ourselves on a scale which had never been seen before.

It may be that we are the first civilization in our event horizon. It may also be that we are the thousandth, but all other civilizations have either annihilated themselves, or threw themselves back into the stone age the way we did after the collapse of classical civilization and the re-surgeance of magical thinking.

Maybe we are late to the party and all those transmissions from our nearby neighbors have already been broadcast and rushed by, never to be heard from again.

Statistically the number may be minute that there is other life and that it will have developed at the same time as us so that we could interact with one another. Granted.

But as for the emergeance of life in general, i am pretty confident that it is actually hard not to have life if the conditions are right. Matter IS self organizing. Gravity and chemistry conspire to bring things together and once elements are close they interact. Life is nothing more than a self sustaining chemical reaction. Is it amazing that we exist? Yes. Perhaps. But on the other hand, of the two planets which could possibly support life, one certainly does (earth) and the other may have at one point (mars).

In fact there are some suspicious methane emissions on mars that may point to sub-surface microbial life still on that planet. Then of course there are the moons of jupiter, where it seems that Europa actually has a liquid ocean beneath it's surface of ice. In which case, there is almost certainly some kind of life.

Taken in that light, considering the relative few number of planets in our own solar system, consider that out of those few there is already a rich history of life on one of them, and possible life on others, life may not be that hard to find.

So far the exo-planets we've been able to detect are hot-jupiters, or other close-in satelites. We need to be able to get a good look at other goldie-locks planets. And when we do, i will not be at all surprised to see it squirming with life.

Yet another assumption is that sentient life is necessarily going to be technologically-advanced. It's hard to imagine, but certainly life forms may be extremely developed with highly-developed language, but which are not driven as we are to manipulate the environment or to have to fight for dominance. In fact, one could argue that a highly sentient species would learn to coexist with other creatures and in harmony with nature. Such a species would likely be around for much longer too.

agreed.

we may be better off understanding alien intelligence if we studied other forms of intelligence right here on earth.

great apes, whales, dolphins, and to an extent, squid are all local intelligences which we could do well to try understanding.

Dolphins are a great example of what you were saying.

No matter how intelligent a dolphin is, what would ever make it think to invent a tool? It spends almost the entirety of it's life free floating in the water. Rarely does it ever brush up against any surface that is solid, and that is usually another dolphin, or a food item.

Species like that, it seems to me, would never invent a radio tower.

We have been a sentient race for a few dozen thousand years, but have only JUST figured out telecommunications. And almost immediately afterwards we gained the ability to utterly annihilate ourselves on a scale which had never been seen before.

We have communications a mere million years after becoming sentient. That is an eyeblink. Sentience lead to technology much much faster than life lead to sentience. Read that carefully if it didn't make sense, sorry.

johnson1010 wrote: Dolphins are a great example of what you were saying.

No matter how intelligent a dolphin is, what would ever make it think to invent a tool? It spends almost the entirety of it's life free floating in the water. Rarely does it ever brush up against any surface that is solid, and that is usually another dolphin, or a food item.

Species like that, it seems to me, would never invent a radio tower.

It's not that hard to imagine that dolphins or their descendants could invent a tool - some kind of bait or trap that could then get more sophisticated, or even to move back onto land.

And besides, imagine someone observing early humans without any preconceptions. They eat, sleep and reproduce just like every other animal. What would they ever need modern technology for?