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Mystery of interstellar visitor 'Oumuamua gets trickier

scientificamerican.com

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Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#221

Post by oefnak »

satori99 wrote: post #214
monkeypizza wrote: post #123

Earlier quoted context omitted.

Excellent page discussing the physics of colonizing mercury: https://einstein-schrodinger.com/mercury_colony.html "Colonization of Mercury appears to be a very real and practical possibility, whereas colonization of Mars or the other planets, moons or asteroids is really more in the realm of fantasy." A big advantage of Mercury over mars is higher light intensity: "One very important advantage is the high solar light…

Kim Stanley Robinson wrote a book, 2312 , which featured an equatorial city on Mercury mounted on massive concrete rails. The expansion of the concrete rails on the day side permanently keeps the city in the planets relatively pleasant pre-dawn zone. The city only needed to move at walking pace to stay ahead of the sunrise. IIRC one of the major mercurian industries was maintaining massive solar reflectors that were…

What if the city would have engine trouble, though...

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#222

Post by microtherion »

edgyquant wrote: post #170
microtherion wrote: post #161

Earlier quoted context omitted.

But this is not the only way you can deploy machine learning techniques. You could deploy unsupervised learning to first learn what visual features are common in such images, and then successively refine until you end up with a set of images containing very rare phenomena. That could give human evaluators then a considerable head start. In fact, this idea seems so obvious that it must have been tried already…

Has it? I'm very interested in using data science for astronomy as it was my childhood passion and I'd love to read anything you can provide.

I'm sorry, this was pure speculation on my part, I don't have actual knowledge of this happening.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#223

Post by satori99 »

oefnak wrote: post #221
satori99 wrote: post #214

Earlier quoted context omitted.

Kim Stanley Robinson wrote a book, 2312 , which featured an equatorial city on Mercury mounted on massive concrete rails. The expansion of the concrete rails on the day side permanently keeps the city in the planets relatively pleasant pre-dawn zone. The city only needed to move at walking pace to stay ahead of the sunrise. IIRC one of the major mercurian industries was maintaining massive solar reflectors that were…

What if the city would have engine trouble, though...

It had no engines. The sun-side tracks thermal expansion provided the energy to keep pushing the city into the night-side.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#224

Post by joubert »

kentonv wrote: post #128
throwaway316943 wrote: post #116

Earlier quoted context omitted.

I’m not sure that reasoning holds up. There’s no reason to believe that “mushy human emotional ideas” are not the norm. There’s no data to support that claim since humanity is the only example we have of intelligence. So for the sake of the argument I’m going to define alien intelligence as similar to human intelligence. I’d also inquire what the point of having a Von Neumann probe consume all of a system would be? I…

Once a civilization is capable of building Von Neumann probes, it would be silly for them not to do so. They are basically free, since they are self-replicating. Of course a civilization is going to want to control and harness as many resources as it possibly can. We may not be able to imagine what they'd want to build out of whole star systems, but I absolutely don't believe that civilization will ever run out of th…

> In 4.5 billion years, the Milky Way will collide with Andromeda. This presents us with a literal galactic-scale single-turn prisoner's dilemma: If intelligent life exists in Andromeda, they may already be preparing to conquer the Milky Way. If they are, and we don't prepare to fight back, they will obviously win. We won't have any ability to communicate with Andromeda to find out their intentions until it's too late. The earlier we start preparing, the more likely we are to survive.

I'm trying to imagine what to do now in preparation for a hostile encounter in 4.5 billion years that isn't already happening organically. By "organically", I mean both "in the course of gradual or natural development" and "w.r.t. living matter", given the time scale.

Do you have ideas?

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#225

Post by lmilcin »

codeflo wrote: post #189
lmilcin wrote: post #187

Earlier quoted context omitted.

Big disadvantage of Mercury is its depth in Sun's gravitational well. This is worse than planetary escape velocity, because you have to pay it on both ways (to get to Mercury as well as get back). Another problem is radiation which this close to Sun and with no atmosphere is pretty huge issue. Light intensity is irrelevant. Energy in the form of light is pretty much free within solar system unless it is somehow obstr…

Can you explain why you have to pay for the Sun's gravitational well on the way to Mercury? From the famous XKCD illustration[1] I get the impression that it might be hard to "stop at" Mercury since the pull of the Sun is relatively strong. Is there no clever trajectory that comes close enough to Mercury to get caught in its orbit? [1] https://xkcd.com/681/

I think Randall's image is a bit misleading. I mean it is correct and fun, but for an uninitiated person it might cause impression that going down the well costs zero energy.

That of course is true, if you are stationary. Then you just start falling like apple from apple tree. But almost no objects in space are stationary, typically everything orbits something and frequently multiple things at the same time. Think about a rocket that is on an orbit around Earth. It is not free to fall to Earth, it must expend delta V to slow down enough so that its perigee is within Earth atmosphere (and typically well within atmosphere or it will just bounce off it).

At the same time, the rocket orbits the Sun, so even if it leaves Earth it still is not free to "fall" into Mercury. It must expend delta V to slow down so that its perihelion lowers at least to Mercury orbit.

So the graph on xkcd is correct, but with regards to bowling balls you might want to shoot up or let fall down from a position that is stationary in some celestial body's frame of reference.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#226

Post by mgr86 »

hossbeast wrote: post #69
davrosthedalek wrote: post #41

Earlier quoted context omitted.

Yes, if Charles Darwin would publish a book today, with a focus on a layman reader, and then give interviews, instead of publishing his findings in journals, I would be skeptical.

But he is publishing in journals. The article cites his papers.

It’s a very “academic” thing to do. Cite yourself as often as you can.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#227

Post by vivekd »

kentonv wrote: post #182
pavlov wrote: post #158

Earlier quoted context omitted.

“Of course a civilization is going to want to control and harness as many resources as it possibly can.” This may be an entirely human-centric assumption. Maybe there are a million civilizations out there living in balance with their local planetary environments, entirely without the expansionist curiosity and destructive drive that leads humans to seriously contemplate things like von Neumann probes?

The desire to survive and expand is not a human trait, it is a natural result of evolution. Any successful evolved species will have this desire because those that don't, don't get anywhere. Interstellar civilizations are unlikely to be biological, but evolution still applies. All it takes is for one civilization in the whole galaxy to decide to build Von Neumann probes, and they'll have taken control of all unoccupi…

Is it? Evolution itself seems like an expansionary process but it doesn't seem to follow that the outcomes of the evolutionary process are expansionary. It seems like many species are evolved to very specific environments like caves or thermal vents that they will stay in for generations if not for thr duration of their existence as species.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#228

Post by mirekrusin »

Gibbon1 wrote: post #155
sulam wrote: post #60

The subhead is "Aliens? Or a chunk of solid hydrogen? Which idea makes less sense?" The better version would be: "Journalism? Or Clickbait? Which idea makes less sense?" "Scientific American" indeed.

I think it's extremely low density collection of dust particles held together by electrostatic forces. AKA a cosmic dust bunny.

Maybe interesting idea for long distance engine, worth exploring.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#230

Post by rendall »

bluedays wrote: post #100
rendall wrote: post #28

Earlier quoted context omitted.

"what if aliens were watching this?" There is an archetype of the Mysterious Stranger, an innocent, naive observer of our culture, who finds us incomprehensible because we are Just Terrible. We make war, pollute, enslave, etc, while this archetype is pure. Examples: K-Pax, Powder, Dostoyevski's The Idiot, Crocodile Dundee all have elements of this archetype The thing is, the only reason this archetype has any meaning…

I don't think that's true. I could conceive of an alien "prime directive" like in Star Trek. So saying that it's out of the question is definitely not something that I believe. Humans, after all, are constantly observing other species. Why wouldn't aliens?

Can you expand? I don't see the logical connection between "I can conceive it" and therefore it's possible.

I mean, it's possible aliens are so similar to us we could communicate and share values. I just don't see why we would expect it, given that they will have evolved in a completely different environment with completely different evolutionary pressures. We would be far more likely to figure out what whale songs mean than communicate meaningfully with aliens

I'll leave aside my personal favorite pet answer to the Fermi Paradox that we have not evolved the ability to even perceive aliens; but suffice to say when I mean aliens are different, I mean different, not just basically people with funny ears

So, to my mind, the question to answer is not "Why wouldn't aliens?" but "Why would they? How would it even be reasonably possible?"

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