Aliens on 1k nearby stars could see us, new study suggests • Hacker News Board

Re: Aliens on 1k nearby stars could see us, new study suggests

#131

Post by ben_w » Fri, Oct 23, 2020, 10:06 PM UTC

skissane wrote: post #118

ben_w wrote: post #79

Earlier quoted context omitted.

Going fast in a straight line with conventional rockets is achievable, just not very timely. Bending spacetime enough to make a difference — even just to the time taken between here and Alpha Centauri — is beyond any known mechanism humans could build, even in principle, using the total resources of our entire solar system. (Using unknown mechanisms: perhaps, but they’re unknown)

> Going fast in a straight line with conventional rockets is achievable, just not very timely. A constant-acceleration spacecraft could reach the opposite side of the galaxy in 24 years ship time. (That'd be over 100,000 years of Earth time, however.) Conventional chemical propulsion don't have high enough impulse to do that. Possibly some kind of nuclear or matter-antimatter propulsion could?

Everything would run out of fuel over that distance if you were constantly accelerating ahead [0], but you don’t need to constantly accelerate in space.

[0] spinning is accelerating, and you can do that forever, but it won’t help you get anywhere

Re: Aliens on 1k nearby stars could see us, new study suggests

#132

Post by tsimionescu » Fri, Oct 23, 2020, 10:11 PM UTC

saas_sam wrote: post #95

tsimionescu wrote: post #92

Given that life only appeared once on earth in 3.5 billion years on Earth, the Milky Way is around 14 billion years old, we don't really have a good reason to believe there were more than a handful of abiogenesis events in the history of the galaxy. Of course, its possible this is completely wrong, perhaps the Earth was completely unlucky, or perhaps there have been many abiogenesis events and they have just failed f…

Is "life only appeared once on earth" an accepted fact at this point? There was clearly at least one occurrence that led to a subsequent successful reproductive pattern from which we evolved, but prior to that, or alongside that, it strikes me as pretty unlikely that we would be able to discover other fleeting abiogenesis events. We just discovered new salivary glands in human heads. Organs. Not microscopic ones. The…

Sure, that's not impossible at all.

Still, until we find such life, the default assumption should be that it doesn't exist, and so that abiogenesis is an extremely unlikely even, even on Earth.

Re: Aliens on 1k nearby stars could see us, new study suggests

#133

Post by tsimionescu » Fri, Oct 23, 2020, 10:14 PM UTC

Baeocystin wrote: post #101

saas_sam wrote: post #95

Earlier quoted context omitted.

Is "life only appeared once on earth" an accepted fact at this point? There was clearly at least one occurrence that led to a subsequent successful reproductive pattern from which we evolved, but prior to that, or alongside that, it strikes me as pretty unlikely that we would be able to discover other fleeting abiogenesis events. We just discovered new salivary glands in human heads. Organs. Not microscopic ones. The…

No. We have a Last Universal Common Ancestor, but that says nothing about whether or not there were other independently-formed branches that were competing at the time. My personal opinion is that life under early Earthlike conditions was/is almost a guarantee. There is compelling evidence that life already existed in and survived the Late Heavy Bombardment- that's very early in our planet's history. If it was truly…

> My personal opinion is that life under early Earthlike conditions was/is almost a guarantee. There is compelling evidence that life already existed in and survived the Late Heavy Bombardment- that's very early in our planet's history. If it was truly a rare event that sparked things off, I would expect it to have occurred much later in the planet's history.

That is valid of course, but in the absence of evidence of its existence, the default assumption should be its unlikely.

Re: Aliens on 1k nearby stars could see us, new study suggests

#134

Post by tsimionescu » Fri, Oct 23, 2020, 10:18 PM UTC

delecti wrote: post #128

tsimionescu wrote: post #116

Earlier quoted context omitted.

If abiogenesis is common, we should expect it to keep happening everywhere around us. We should have noticed at least a few instances by now, given that we have been trying explicitly to produce it. So at the very least, we can say that the conditions for the apparition of life and the conditions for the proliferation of life seem to be quite different. Also, given the amount of isolated biomes on earth, if abiogenes…

What would abiogenesis even look like today? Some random molecules bouncing together in just the right way and spontaneously forming some organic compounds. And then a bacteria comes along and eats it, or it encounters the huge concentration of environmental oxygen and reacts. Going from inorganic sludge to life isn't "an event", it's multiple events over millions of years until the right chemicals get together and f…

Sure, that's a plausible account. However, they would only compete if they appeared in a pretty small geographical area. That still leaves it as being a relatively singular event. Maybe much more than once in a few billion years, but still much rarer than many seem to assume.

I would also note that we don't really know of any mechanism that would require millions of years for chemical reactions, or any equivalent of the theory of evolution that would work for hypothetical complex organic substances. Not to say that either is impossible!

Re: Aliens on 1k nearby stars could see us, new study suggests

#135

Post by marta_morena_28 » Fri, Oct 23, 2020, 10:20 PM UTC

jcims wrote: post #114

deeeeplearning wrote: post #71

Earlier quoted context omitted.

Given the age of the Milky Way, a civilization using even slow sub light travel with generation ships or autonomous probes could have colonized the entire galaxy many times over. Why has no one done that? Hence the paradox.

I'm fairly confident we'll eventually find that our form of life is the result of intentional or unintentional colonization of Earth. If you look at how quickly life began after the oceans settled out, then look at precisely how complex even the most primitive forms of life are (in terms of likelihood of stochastic construction to the point of sophistication to support evolutionary mechanisms) it seems incredibly unl…

Possible, but far reaching. There are other explanations:

* We are a computer simulation (hence there is no colonization, we are in an experiment)

* There are like 1,000,000,000,000,000,000 habitable planets in the universe. Just because something is "extremely unlikely" doesn't mean that it didn't happen to us. I.e. whomever this happened to, would ask himself that question. We may just be the ones it happened to.

Also: Why would they settle species from millions of years in their own past. If they wanted to colonize, they could start with their own life-forms.

Could be several things as well:

* We are a genesis project and they will simply come back later and settle in what we left behind (i.e. they let the ecosystem build for a few million years before trying out this settlement)

* They don't want to create competitors

* We are a population bomb, i.e. they just sent out billions of probes trying to populate any given habitable planet, and they couldn't just spawn themselves there and instead had to start from somewhere where a sustainable ecosystem would derive from

Re: Aliens on 1k nearby stars could see us, new study suggests

#136

Post by tsimionescu » Fri, Oct 23, 2020, 10:22 PM UTC

swebs wrote: post #127

tsimionescu wrote: post #116

Earlier quoted context omitted.

If abiogenesis is common, we should expect it to keep happening everywhere around us. We should have noticed at least a few instances by now, given that we have been trying explicitly to produce it. So at the very least, we can say that the conditions for the apparition of life and the conditions for the proliferation of life seem to be quite different. Also, given the amount of isolated biomes on earth, if abiogenes…

The entire planet is coated with bacteria and bacteriaphages. It's entirely possible that any new life created through abiogenesis is almost immediately outcompeted by evolved microbes.

In today's world, perhaps, but it must have taken vast amounts of time until the first bacteria covered the planet. If abiogenesis were a frequent event on the early earth, there should have been plenty of space for more than one lifeform to survive before life became ubiquitous. And of course it's possible, but it shouldn't be the default assumption either.

Re: Aliens on 1k nearby stars could see us, new study suggests

#137

Post by tzs » Fri, Oct 23, 2020, 10:29 PM UTC

tsimionescu wrote: post #86

deeeeplearning wrote: post #71

Earlier quoted context omitted.

Given the age of the Milky Way, a civilization using even slow sub light travel with generation ships or autonomous probes could have colonized the entire galaxy many times over. Why has no one done that? Hence the paradox.

There are problems of resiliency and energy storage that could be more or less fundamental problems. It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel, and civilizations may tend to collapse for various reasons before reaching such technological peaks. It's also entirely possible that w…

> It could take millions if years of technological civilization to produce a machine capable of sustaining life for the hundreds of thousands of years necessary for interstellar travel.

For a generation ship, are you referring to all the machinery that can maintain a balanced ecosystem of plants and animals and humans in order to provide food for the people during the trip to the new planet, and to make all the things needed to keep those people healthy during the trip such as medicine and drugs?

If so, there may be a way around that. Send all your colonists as frozen embryos or frozen sperm and eggs. Your ship only needs life support then to keep alive the people who run the ship. For food, don't grow it. Take it with you.

At first taking your food with you seems absurd, but if you had a food with the same caloric density as rice, enough of it to provide 2000 calories/day to one human for 100k years would fit in a sphere with a radius of 24.4 meters. So once your technological civilization figures out a way to preserve food such that they can make a rice ball equivalent with a 100k year storage life, a generation ship with a small crew becomes a whole lot more feasible.

For replacement crew throughout the journey, you can do a mix of using whatever kids the crew produces the old fashioned way and using kids produced from some of the frozen embryos/eggs/sperm.

I think technological civilizations will reach the point of being able to do this well before they are millions of years old. We aren't too far from being able to do it ourselves. We are probably farther out on the propulsion for the ship itself.

Re: Aliens on 1k nearby stars could see us, new study suggests

#138

Post by apacehead51 » Fri, Oct 23, 2020, 10:32 PM UTC

If the planet is in the habitual zone for a given star with H2O then there is a biological chance some form of life exists. The evolutionary cycle for advances species development on the planet is the question. The human race did not evolve in a few million years. If there is a living advances species they could be very primitive compared to humans or much more advanced. There are so many variables that even science has not fully developed to come up with a plausible answer.

Re: Aliens on 1k nearby stars could see us, new study suggests

#139

Post by AndyPa32 » Fri, Oct 23, 2020, 10:34 PM UTC

dyingkneepad wrote: post #117

vl wrote: post #112

Earlier quoted context omitted.

Basically there is not need and motivation for humans to colonize anything outside the Earth. It's just too far, too expensive and too uncomfortable. Humans evolved specifically to live on Earth, to live somewhere else, they need to be severely altered. Now you just seeded civilization of another species, that might turn out to be confrontational or outright hostile. Why would you do that? Too see how well this works…

> Basically there is not need and motivation for humans to colonize anything outside the Earth. Our current gas emissions would disagree. Also, asteroids, gamma ray bursts, curiosity, sheer ambition, etc, etc. The thing is: we don't need to convince all of mankind to colonize another planet. All it takes is a few people. Crazy rich Mr. Musk is one example. He may not be able to achieve it, but maybe all we need is a…

> Our current gas emissions would disagree.

While at first it might seem that Mars or any other planet is the solution to our environmental problem, the easiest solution to the problem would be fixing this planet. Colonizing Mars would take up so many resources that fixing Earth might be more cost-effective.

Re: Aliens on 1k nearby stars could see us, new study suggests

#140

Post by psychoslave » Fri, Oct 23, 2020, 10:34 PM UTC

Osiris wrote: post #124

jcims wrote: post #114

Earlier quoted context omitted.

I'm fairly confident we'll eventually find that our form of life is the result of intentional or unintentional colonization of Earth. If you look at how quickly life began after the oceans settled out, then look at precisely how complex even the most primitive forms of life are (in terms of likelihood of stochastic construction to the point of sophistication to support evolutionary mechanisms) it seems incredibly unl…

This is an interesting idea. Look at how religion explains the origin of life: A lifeform not from this planet, far more advanced than us, gave "the breath of life", and calls us their "children". The vastness of this universe leads me to believe that it's impossible to dismiss the idea that there is an intelligence/lifeform sufficiently advanced as to appear to be a God to us.

That doesn't explain where the said intelligence /lifeform would come from itself, so what the point of such a theory?