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

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

#151

Post by sandworm101 »

tiemand wrote: post #146
rpedela wrote: post #130

Earlier quoted context omitted.

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.

One problem I have with pan-spermia is: Why is there only one tree of life? Not several independent trees. If life evolved in one of the exo-planets, is not possible that several independent forms of life evolved in several planets and some ended up on Earth.

One tree (us) either appeared first and dominated resources, or we wiped our the other trees. Evolutionary forces work at levels above species. Two trees can compete with each other.

If this happened it did so at the microbe level. Physical evidence would be extraordinarily difficult. If we did find evidence of another tree it would be so 'alien' to our tree that might mistakenly call it extraterrestrial.

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

#152

Post by nickwalton00 »

throwaway7312 wrote: post #116
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.

It sounds more like anti-natalism is your personal philosophy, and you make the same assumption the holders of most philosophical, ideological, and religious positions make: sooner or later, everyone else will realize to be true what I realize is true. The history of man suggests otherwise. The more our civilization progresses, and the more the population swells, the broader the array of philosophical positions those…

Very true. It's very hard for people who don't make children to not just get replaced with people with different beliefs.

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

#153

Post by Symmetry »

m_mueller wrote: post #91
hyperpallium wrote: post #75

Earlier quoted context omitted.

If you're a fan of Moore's Law and the Singularity, you'll love the reasoning of backtrapolating the exponentially increasing complexity of life over time... to get 0 well before the formation of the earth https://www.technologyreview.com/s/513781/moores-law-and-the...

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

If you look at probability distributions rather than single estimates for every term in the Drake Equation then the absence of visible aliens isn't so unlikely.

http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...

And just the existence of life doesn't mean there's complex life. We don't have a firm lower bound on how long life took to arise on Earth after we got liquid water on the surface but it can't have been more than 120 million years. Photosynthesis, mitochondria, and other innovations allowing for complex life like you and me took way, way longer. I made a diagram for a blog post here:

http://hopefullyintersting.blogspot.com/2018/03/the-drake-eq...

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

#154

Post by riffraff »

throwaway7312 wrote: post #112
m_mueller wrote: post #91

Earlier quoted context omitted.

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

Uncontacted tribes in the Amazon likely wonder the same thing. It's such a big Earth, yet only a few hundred humans are known to exist. Why are there no other detectable signs of human life, like smoke signals, territory markers, or emissaries from any more but a handful of other tribes? Surely if advanced humans existed, they would have contacted these tribes by now, to share technology, discoveries, and medicine. Y…

I understand the point that we might be too backwards to see the signs of hyper-advanced civilisations, but how is it that _all_ the other civilizations are super advanced to the point that any trace they leave is impossible to understand?

And, won't uncontacted tribes in the amazon have seen airplanes and such?

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

#155

Post by nickwalton00 »

JoeAltmaier wrote: post #127
kamaal wrote: post #101

Earlier quoted context omitted.

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.

Everything has some level of intelligence, but the intelligence to develop tools and civilization beyond tribes and sticks is something else.

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

#156

Post by ben_w »

dragonwriter wrote: post #129
ben_w wrote: post #66

Earlier quoted context omitted.

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.

True, although I expect the ISM pressure to be fairly directly measurable. I wonder what the magnitude of all possible affecting things is compared to the gravity of planet like objects at various distances…

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

#157

Post by stephengillie »

tiemand wrote: post #146
rpedela wrote: post #130

Earlier quoted context omitted.

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.

One problem I have with pan-spermia is: Why is there only one tree of life? Not several independent trees. If life evolved in one of the exo-planets, is not possible that several independent forms of life evolved in several planets and some ended up on Earth.

The individual nucleobases (cytosine [C], guanine [G], adenine [A] or thymine [T]) are made from the 4 most common elements, and appear to be modestly simple molecules. Is it so unbelievable that they naturally occur like methane or sodium glass?

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

#158

Post by nickwalton00 »

antisthenes wrote: post #147
vorg wrote: post #124

Earlier quoted context omitted.

> 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…

Powered by what?

I mean that would only take the energy of 200 Quadrillion Hiroshima nuclear bombs. No biggy.

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

#159

Post by Balgair »

m_mueller wrote: post #91
hyperpallium wrote: post #75

Earlier quoted context omitted.

If you're a fan of Moore's Law and the Singularity, you'll love the reasoning of backtrapolating the exponentially increasing complexity of life over time... to get 0 well before the formation of the earth https://www.technologyreview.com/s/513781/moores-law-and-the...

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

Three things:

1)

Ordinary Matter ~10^53 kg (4.9%)

  Dark Matter          ~5*10^53 kg                  26.8%

  Dark Energy          ~1.3*10^54 kg                68.3%

 Undiscovered                ?                        ?
We are only made up of up. It's ok, makes no sense to anyone else either. I put 'Undiscovered' there, as it seems we are making discoveries about the universe at a pretty rapid rate these last few centuries, so this budget is likely not even close to the real thing.

Also, people talk a lot about not meeting aliens, but just talking to them. Based on the fact that we have little/no idea how Dark Matter and Energy works, and we only really use radio signals (when funding permits), it may be like trying to whisper at the Queen of England while standing in Norway; a telephone would be much better.

2) Tom Scott on immortality and risk : https://www.youtube.com/watch?v=B5a6wrJpxP4

3) Life may be so abundant in the universe that it's not worth talking or meeting up with. What would you say to a single mayfly if you could talk to one on it's level? No scientist or other person has bothered to try, and I think there's a good reason for that.

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

#160

Post by [deleted] »

joshuahedlund wrote: post #138
throwaway5752 wrote: post #121

Earlier quoted context omitted.

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.

> continents won't have fossils if they are under frequent bombardment. Right, but if giant bombardments completely boil away the oceans and atmosphere to rain liquid rocks back down on the surface, there very very likely won't be life, either. So the claim is not just that "fossils only go back to X" but that X is so close to the end of the giant bombardments that there's almost no time left (geologically speaking -…

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