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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

#211

Post by landryraccoon »

kentonv wrote: post #184
landryraccoon wrote: post #145

Earlier quoted context omitted.

Consuming all available resources and destroying all competing life doesn’t make sense even for us as the dominant species of a single planet. What’s the evidence that wholesale environmental destruction is a good idea on a galactic scale if it’s already known to be a terrible idea on a planetary scale?

It's a terrible idea for humans on our planet because we are squishy biological beings whose life is intrinsically dependent on the biosphere around us. Self-replicating hyper-intelligent artificial beings presumably will be able to redesign themselves to match any target environment. Note: This is not a moral judgment. I obviously think it would be awful if some AI gray goo consumed the universe and wiped out all th…

Here's the problem. It would be astoundingly unlikely that we would still exist if such a civilization existed.

For this to have happened, it must have happened much less than a million years ago, otherwise your hypothetical civilization would already have easily consumed the entire galaxy.

Since we are still here, if that civilization exists, it must have arrived on the interstellar scene less than one quarter of one tenth of one percent (This is the fundamental problem with Von Neumann probes / AI grey goo in general : They eat the galaxy way, way faster than anyone can imagine. If they exist, why are we still here?

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#212

Post by LargoLasskhyfv »

kentonv wrote: post #47

My pet theory (which is not intended to be taken too seriously) is that it is indeed a discarded light sail, and that light sail in particular was used to transport a Von Neumann probe which detached at some point after the object entered our solar system but before we first observed it. This detachment, in addition to leaving the sail tumbling, would have changed its trajectory, meaning our estimation of which direc…

Shit happens, as in https://en.wikipedia.org/wiki/Code_of_the_Lifemaker

The prologue is sufficient http://www.baen.com/chapters/W200203/0743435265___0.htm , the rest is a matter of taste.

Personally I found it to be hilarious :-)

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#214

Post by satori99 »

monkeypizza wrote: post #123
kentonv wrote: post #47

My pet theory (which is not intended to be taken too seriously) is that it is indeed a discarded light sail, and that light sail in particular was used to transport a Von Neumann probe which detached at some point after the object entered our solar system but before we first observed it. This detachment, in addition to leaving the sail tumbling, would have changed its trajectory, meaning our estimation of which direc…

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 used to boost light going to specific asteroid greenhouses.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#215

Post by neatze »

postalrat wrote: post #191
nvrspyx wrote: post #83

Earlier quoted context omitted.

> I think it's plausible that a god would not want to talk to another intelligent civilization. Why would we? We would be to a god what bacteria is to us. That may be because we can't even perceive bacteria, but if we go a little bit bigger and you could have a conversation with a dog, cat, deer, or any other animal, I bet you would. I know I personally would just to understand how those animals think and the differe…

It's hard to conceive of an intelligence as much above ours as we are above bacteria cell. But if such a thing did exist why would it want to communicate with us?

If I could talk to cell(s), morphogenesis would be my topic of discussion.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#216

Post by deepsun »

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…

Why do you want to "beat Andromeda"? You have your Von Neumann probes, they have their own. Maybe theirs are better. Why do you want yours to beat theirs?

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#218

Post by lmilcin »

forand wrote: post #195
codeflo wrote: post #189

Earlier quoted context omitted.

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/

You want to stop when you get to Mercury. In the XKCD illustration you have fallen quite a bit from Earth to Mercury and now have that as kinetic energy. You can dissipate that by hitting Mercury but that would likely have significant negative side effects.

Loosing the energy on Mercury is only part of the problem. You also have to get there.

Contrary to popular belief, going closer to the Sun is as much difficult as going further away from it. Orbits require energy to change them regardless which direction you want to do it. You can go to tables and see going to Mercury costs almost the same as going to Jupiter: https://en.wikipedia.org/wiki/Delta-v_budget

There are handy maps of Sol system if you are interested: https://forum.kerbalspaceprogram.com/index.php?/topic/131682...

You can of course minimize the energy even further using gravity assists, but this would require multi-year journey.

There is another trick when you want to go very close to the Sun, which is to go further away first, and then use much less energy to actually stop your orbital speed and fall however deep into Sun well you want. Unfortunately, Mercury is just far enough from the Sun to make it unprofitable and it also takes an awful amount of time to execute.

Re: Mystery of interstellar visitor 'Oumuamua gets trickier

#219

Post by AllegedAlec »

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/

A better image (imho): https://i.imgur.com/SqdzxzF.png
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