Space Is Full of Planets, and Most of Them Don't Even Have Stars • Hacker News Board

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#121

Post by throwaway5752 » Wed, May 30, 2018, 12:29 PM UTC

zeth___ wrote: post #87

quietbritishjim wrote: post #77

Earlier quoted context omitted.

> life appeared so soon after the Earth became solid It took hundreds of millions of years, possibly up to a billion years, for basic life to form on Earth. I would say that is not "soon"; it's a really long time . The obvious response to that is, yes it seems like a long time, but it's not much on geological time scales. But it feels to me that there's an implicit circular argument here: the whole reason that geolog…

Life shows up in the fossil record more or less as soon as rocks on the Earths surface start forming. The first billions years on earth mostly involved the planet getting hit by large things and the surface melting. Repeat every millennium.

You just explained why there's no fossil record from early earth, unless I'm misunderstanding you and that was your point.

Ocean floor is continuously destroyed as it's subducted, and continents won't have fossils if they are under frequent bombardment.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#122

Post by hvidgaard » Wed, May 30, 2018, 12:33 PM UTC

zaarn wrote: post #117

hvidgaard wrote: post #114

Earlier quoted context omitted.

When I think about it, maybe it isn't a problem after all. I would think that you can measure gravity and see black holes before you hit them.

Measuring gravity is hard. What you can do is measure gravity at both ends of your ship and if they differ by a lot you're currently being shredded apart by a blackhole.

I'm sure that we'll have that figured out once we can manage interstellar travel.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#123

Post by Brockenstein » Wed, May 30, 2018, 1:01 PM UTC

pavlov wrote: post #113

Aaargh20318 wrote: post #102

Earlier quoted context omitted.

Personally I think the answer is anti-natalism. Once life gets more intelligent it takes a relatively short time (compared to the age of the universe) to get to the point where they realise it's unethical to create new life and choose to go extinct. As a result, intelligent life around the universe only exists as short 'blips', being around for too short a time to ever meet other species.

The default for unintelligent life is to survive at all cost and fill every niche. You're suggesting that intelligence flips that purpose so that every sentient species eventually becomes depressed suicidal existentialists?

All at the same time, united in a single goal...

Seeing the wide spectrum of intelligence and education that humans manage it's hard for me to believe we'll ever reach a point of uniformity as a species were something like self-imposed extinction would be plausible.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#124

Post by vorg » Wed, May 30, 2018, 1:04 PM UTC

brazzy wrote: post #56

itronitron wrote: post #26

Interstellar travel now seems a lot more hazardous than it did before. To quote one of my TAs in college, "it's the stuff you can't see that gets you" ...

Quite the opposite, actually. At near lightspeed, a pea-sized rock will kill your spaceship just as dead as a planet. So you actually want your interstellar masses to be as concentrated as possible.

> At near lightspeed, a pea-sized rock will kill your spaceship

Why travel in a spaceship? If there's 100,000 starless planets for every star in the galaxy, then travel between stars on one of them instead. Build the habitations 10 km below water to avoid radiation. Travel at 0.1% light speed instead and get to the nearest star in 5000 yrs. Enjoy the journey, and slip into an orbit around the target star.

Speaking of pea-sized rocks, periodically fire one laden with electronics/optics/quantumics at the target star at near light speed and receive its transmissions for recon.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#125

Post by ekianjo » Wed, May 30, 2018, 1:10 PM UTC

hyperpallium wrote: post #95

m_mueller wrote: post #91

Earlier quoted context omitted.

What about Fermi's paradox though? I mean, where is everyone?

It's addressed in the article: it takes a long time for complex life to arise, so we are among - or the - first.

any evidence to support that extraordinary claim?

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#126

Post by Brockenstein » Wed, May 30, 2018, 1:17 PM UTC

kamaal wrote: post #101

quietbritishjim wrote: post #84

Earlier quoted context omitted.

Humans are really just an example, I regret mentioning it. All significant developments in life (e.g. multi-cellular lifeforms, post-Cumbrian explosian animals) took hundreds of millions to billions of years.

In fact given the fact evolution is a process without a goal. Intelligence could be even more rare among multicellular lifeforms.

Or the consequence of great intelligence is an evolutionary dead end. What if intelligent life becomes smart enough to destroy itself, but doesn't survive quite long enough to use that intelligence to save itself.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#127

Post by JoeAltmaier » Wed, May 30, 2018, 1:19 PM UTC

kamaal wrote: post #101

quietbritishjim wrote: post #84

Earlier quoted context omitted.

Humans are really just an example, I regret mentioning it. All significant developments in life (e.g. multi-cellular lifeforms, post-Cumbrian explosian animals) took hundreds of millions to billions of years.

In fact given the fact evolution is a process without a goal. Intelligence could be even more rare among multicellular lifeforms.

I remember reading that 4 or 5 intelligent hominids coexisted in Africa a million years ago. More or less intelligent. It can't be that rare then.

In fact, dolphins. Octopi. Yeah, pretty much a given I'd imagine, in the right complex ecosystem, that intelligence is a thing.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#128

Post by perfmode » Wed, May 30, 2018, 1:19 PM UTC

coldtea wrote: post #100

m_mueller wrote: post #91

Earlier quoted context omitted.

What about Fermi's paradox though? I mean, where is everyone?

Fermi's paradox is just a hand-waving argument involving tons of unknown probabilities. It's not a given that alien civilizations "should" have developed this or that technology that we ourselves don't have.

it’s a probabilistic argument, so it is inherently about “should”

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#129

Post by dragonwriter » Wed, May 30, 2018, 1:20 PM UTC

ben_w wrote: post #66

everdev wrote: post #46

Earlier quoted context omitted.

Well, if there's not much around it, it might be hard to detect it's gravitational effects. I'd imagine you could detect it blocking a circular patch of sky more easily and from farther off than you could detect the gravitational pull on your spacecraft. Just don't steer twords the black disc and you'll be fine.

Four ships (or a ship and three probes) arranged in a tetrahedron, where the distance between each pair is precisely measured with a laser or similar. Changes to the edge lengths of the formation show a nearby gravity gradient. What’s one wavelength per minute if the formation is 1000km?

> Changes to the edge lengths of the formation show a nearby gravity gradient.

Or changes in density or relative velocity of the interstellar medium, etc.; gravity isn't the only feature that can alter the formation.

Re: Space Is Full of Planets, and Most of Them Don't Even Have Stars

#130

Post by rpedela » Wed, May 30, 2018, 1:21 PM UTC

perl4ever wrote: post #19

Based on the inverse correlation between star size and frequency, this doesn't surprise me at all. It seems like there is an obvious further inference to make - people have debated whether life originated on earth or not. Given that the vast majority of planets do not have a star, and given that we know there are chemotrophs even on Earth that prove it is possible to live without a sun, it seems overwhelmingly likely…

I generally don't like the assumption that life had to come from space because we don't know how life is created and it appeared so soon in the history of Earth. That is certainly a possibility, but it also possible that creating life from chemistry is easy. Just because we haven't figured it out yet doesn't mean it is hard. Obviously figuring out how it works is hard, but the mysterious mechanism may be simple.