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Comment by jph | Hacker News Reader

Dr. Drake is especially famous for the Drake Equation (as the article mentions) which is a fascinating way to think about how many intelligent civilizations might be findable.

https://exoplanets.nasa.gov/news/1350/are-we-alone-in-the-un...

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I’ve heard that the Drake equation was originally (?) intended to be a parable that makes you think about whether our civilization is likely to destroy itself before making a noticeable impact on the universe, in order to promote nuclear disarmament

As far as I know, the concept of the 'great filter' was invented by (the now canceled) Robin Hanson.

Hanson gave it that name in the 90s but it’s implied in Drake’s equations - I think people in the 1960s were aware of the subtext

I’ve studied this a lot but it’s been awhile. Drake et al we’re doing this during the Cold War and were definitely aware we could wipe ourselves out either with weapons or through ecological disaster. The L term is specifically about civilizations destroying themselves (although it can also be advances in technology which end radio-as-we-know-it).

The great filter is an attempt to explain the Fermi Paradox. Fermi was there, but the paradox necessarily came after the Drake equation.

I would bet a million dollars that there are no other intelligent civilizations in the universe.

I would take that bet. The observable universe is estimated to have 10^21 stars and the actual universe is infinite.

I'm not sure what you mean by the "actual universe" but there's no proof that space is infinite. Unfathomably vast yes, but still finite.

what's the proof it's finite?

Our senses are finite; we cannot directly know infinity through them. Because of that, I think the burden of proof is on the claim that it is infinite.

Isn't space itself continuously expanding?

Expansion of space doesn’t preclude the universe being infinite.

by actual universe, I meant total universe ( opposed to the observable universe). All of the evidence we have collected so far suggests that the universe is flat and infinite. While some finite universes could be proven, so far we have not.

The size of the actual universe is irrelevant for this discussion since anything outside the observable universe does not have any casual connection to us.

But of course you are right about the absolutely staggering number of stars in the observable universe.

>The size of the actual universe is irrelevant for this discussion since anything outside the observable universe does not have any casual connection to us.

I don't see how causality plays into the question at hand. The parent post didn't bet that we could interact with alien life, but if it exists at all. If it can be demonstrated that the actual universe is infinite, it will follow that alien live exist, independent of if we can interact with it.

This is logically incorrect. The universe may well be infinite, but that doesn’t imply it must harbour life

I believe this would be correct if there were no examples of life already extant - but the fact that we exist shows that the probability of life and civilization arising is strictly greater than 0. Given an infinite universe with a flat probability distribution (i.e. there's nothing particularly special about our little corner), any >0 probability will occur an infinite number of times.

I highly doubt the actual universe is really infinite, however. Incomprehensibly big, yes.

Not enough proof to win the bet, so right now you're losing.

Right now, nobody has proof. While aliens can be discovered at a future date, you can never prove that they don’t exist. It is a very safe bet because they can not prove a negative.

Can you unpack your reasoning here? The likelihood of civilizations occurring/existing in parallel leads me to a similar conclusion.

Not OP, but I fully agree with them. Incoming ballpark figures I and hand waving. If, today, with our current technology, we decided to explore/colonize every star and planet in our galaxy, launching 3 ships per day that travel at single digits percent of c, we could investigate every planet in our galaxy in about a billion years. That's pretty much worse case technological scenario, because at some point in the next thousand or million years we'll have even more incredible technology to build more and fly faster. Probes that can constantly accelerate at 1g will reach other galaxies on the order of millions of years. If they self replicate, or have pioneers that can rebuild civilization on the order of a few thousand years and continue exploring, we're still within that 1 billion year limit to colonize at worst the entire galaxy, and realistically the entire universe. Earth has been around for 5 billion years, and the greater universe for 15. Humans have only existed for 10,000 years. ET should have been here long before we even came into existence.

We only have a few thousand years of reliable history and in many places, far less than that. It's perfectly reasonable in your scenario that ET was here long before we were, missed us by a couple of million years and left.

If you look at the history of human exploration, discovering new lands has not led to immediate settling or the establishment of long-term relationships with the locals.

Assuming they do not have a prime directive.

If the universe is infinite and life is possible ( as we know it to be), then life will occur an infinite number of times.

If we just look at the observable universe, number of stars, number of planets, and habitats we see even in our own solar system, there are a lot of shots on goal.

I don't think that's the right way to think about infinity. Just because the chances are infinite and you know goals are possible, it does not mean that there will be infinite goals. There are infinite numbers between 4.0 and 6.0 but only one of them is a prime.

> There are infinite numbers between 4.0 and 6.0 but only one of them is a prime.

Primality only applies to natural numbers, so there can't be primes between 4.0 and 6.0. There is one between 4 and 6, but that's a finite range.

The concept holds. Perhaps the example isn't great, I'm not sure - but since when does 'the set of numbers between 4.0 and 6.0' not include the natural number 5?

That's a set of real numbers, and primality is not defined for real numbers, so 5.0 can't be a prime. The whole concept is just not applicable unless were talking about natural numbers, in which case the set is finite.

Who said it's the set of real numbers? I don't remember adding any notation that specified the set must be real numbers.

But you can't score 4.1 goals. You can't take 5.9 shots on goal. Goals and attempts are integers. Ask Sheffield United.

I feel like this misses the point. Infinite outcomes != all outcomes.

What you stated is certainly true, but Infinite outcomes == all possible outcomes in infinite quantity, and we know that life is possible.

> infinite outcomes == all possible outcomes in infinite quantity

No it doesn't. This is a common misunderstanding of infinity. Infinite is absolutely not the same as all.

Why take a bet on something that can never be verified?

Can you point out anything that exists only exactly once in the universe?

First tell me what intelligent means....then we can make that bet ;)

https://xkcd.com/384/

The alt text is so great for this one

Sorry, but I always thought the equation meaningless...

I agree - it's basically just a way to arrive at a meaningless number by multiplying a whole lot of wild-ass guesses together.

Do we have anything better, though?

Yeah, that's probably the point. You have to start somewhere.

Personally I'm blown away that some parameters, like the fraction of those stars that have planets, we are able to capably plug values in for.

I really never thought we'd be able to get statistics for things like that in my lifetime.

I mean short of faster-than-light travel, I had assumed ignorantly that astronomy would be stuck more or less where it is for centuries to come.

I wrote a presentation for undergrad on the equation; and that was the focus. I went through each value and talked about the bounds for each value and arguments for those bounds. We’re still incredibly ignorant, but the bounds on the values have improved a lot. At the time the equation was written, it was assumed other stars had planets, but it wasn’t known and the value could have been anything. Now we know the f_p ≈ 1.

Amazing isn't it? I really appreciated 'archives of the universe', which describes the chronological advancement of astronomy since the ancient Greek. Often by simply annotating the original works or papers. Amazing to see how humanity has gained insight piece by piece, thanks to the hard work of a select group op people.

https://cmsw.mit.edu/archives-of-the-universe-marcia-bartusi...

I see it as a way of focusing the discussion. The numbers we could plug into it are mostly all wild guesses, but the exercise of plugging in different numbers can still be instructive.

For example, we now know there are a huge number of planets out there, and even planets in the habitable zone. Yet we haven't found any extraterrestrial life, so that suggests maybe the other factors are smaller than we initially would have guessed.

Because....?

It is a fabulous equation which describes the factors that would contribute to alien life. It can inform how to think and pursue SETI and gauge our current knowledge. Any result that you see bandied about is meaningless because we don't know the inputs.

And deeply flawed...

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