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Why we are unlikely to ever leave the solar system.

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Re: Why we are unlikely to ever leave the solar system.

#91

Post by scott_s »

rosser wrote: post #47
netcan wrote: post #41

Earlier quoted context omitted.

Why is that your guess?

Not the GP, but, in short, because space is very, very big, and very, very empty. By way of extremely loose analogy, consider a large pea (1 cm in diameter) hanging by a string in the middle of a football stadium. Let's say that represents our solar system (minus the Oort cloud) and its environs. That's a slightly scaled-down version of Stross' analogy, where the diameter of the solar system (again, minus the Oort cl…

Yes. For more perspective, the average density of the universe is roughly 3-6 hydrogen atoms per cubic meter.

Re: Why we are unlikely to ever leave the solar system.

#92

Post by troels »

adrianN wrote: post #83
troels wrote: post #80

Earlier quoted context omitted.

? I thought it was the mass that made a black hole - not the density ?

No, you just require a sufficient pressure to overcome the repulsive forces between the particles to collapse them to a singularity. That's why people were afraid of the LHC.

Ah .. And normally (If that is a word which makes sense in this context), the mass of a giant object (Like a star) would be the way to create this pressure? But theoretically you could do it by other means?

Re: Why we are unlikely to ever leave the solar system.

#93

Post by scott_s »

ramidarigaz wrote: post #65
scott_s wrote: post #23

Earlier quoted context omitted.

Simple probability dictates that it is only a matter of time before a sufficiently large body travels through the Solar System with sufficient velocity (including direction) to reach somewhere else in sufficient time (but not too fast that we can't perform an orbital intercept) that we can essentially build a colony on it. Not really. You could also say that "simple probability dictates that it is only a matter of ti…

Hmmm... I don't think your analogy is correct. There is a very solid reason that all the air in the room will never only be in one half of that room. It's a matter of pressure, not probability. I don't think the 'rogue' planets are subject to such things, and on a sufficiently long time scale, it could very well be possible for one to travel through our system.

In support of what the others have said, the reason that we say all of the air in a room will end up on one side is the second law of thermodynamics: entropy in a closed system only increases. That is statistical mechanics, which is very much a matter of probability. The probability that the second law of thermodynamics will be violated is so vanishingly small that we say it will never happen.

Re: Why we are unlikely to ever leave the solar system.

#94

Post by JanezStupar »

zeteo wrote: post #10
cletus wrote: post #6

That's a good, grounded assessment of the scale of the problem. I too believe that the human colonization of space, even near-space (ie within the orbit of the Moon) is a long way off. The energy costs are simply too high and resources too cheap on the Earth to make it viable (in spite of typical SF fodder of asteroid mining). This is a problem because with 6.5 billion people we're using up resources. Fast. Anyway, I…

>Just think about computer chips. On any long voyage they'd break down so you need to be able to make new ones. Chips are small and light enough that you can bring along a thousand times more chips than you need, at negligible additional cost. PCBs are a bit more trouble, but those are much easier to produce and recycle.

They would still age. Were talking thousands of years here. In space, with all the radiation. In interstellar space.

Re: Why we are unlikely to ever leave the solar system.

#95

Post by maxerickson »

Groxx wrote: post #73

> Try to get a handle on this: it takes us 2-5 years to travel two inches [in their relative scale - e.g., Voyager probes] What? No it doesn't. We can do massively better than this, right now. As in, today's technology. No problem. Why haven't we? It's frickin' expensive. But the long-range probes we've launched have been pretty damn near coasting their entire trip, with a few course corrections. They were pushed, an…

The 400 megatons comes from the estimate that the trip would require 2e18 joules (which is about 22x the 9e16 joules up there).

And he is getting away from conventional rockets, the 2e18 estimate assumes that the energy required to move the ship is coming from elsewhere, not carried along with the ship.

So he assumes a very small ship and mysterious ways of propelling it in order to sketch an estimate of the minimum amounts of energy involved. Ripping an even bigger hole in physics might throw acceleration and momentum out the window, but assuming 100% efficient transmission of energy across 24 light years already requires something pretty strange to us.

(his comparisons to present day production levels seem more illustrative than pessimistic)

Re: Why we are unlikely to ever leave the solar system.

#97

Post by hackermom »

jacobolus wrote: post #36
mmaunder wrote: post #35

I dislike the word "never". As individuals and as a species we are addicted to short term gratification measured in years or decades. We also have a narrow view of the concept of "self" and what constitutes consciousness and experience. If we could stand building for the future and experiencing by proxy, a few more options become available: e.g. We could transport a set of human "blanks" or a "blank" creating machine…

Okay. You just wave 5 or 6 magic wands and then it works out. Isn’t that precisely what the essay claimed?

His point is that exactly every single notable achievement in the history of mankind has been preceeded by people saying things just like these - skeptics who keep saying "it can't be done" up until the very last second before "it" is done.

It was said about crossing the seas. It was said about colonizing the surface of the planet. It was said about diving deep into the seas and it was said about taking off ground. It was said about leaving the atmosphere. It was said about reaching out into space. It is currently being said by some about colonizing our solar system, and most people currently feel that the thought of us not colonizing our solar system is ridiculous, and in time the thought of us not leaving this solar system to go on to the next one will be considered just as ridiculous. "Scientists" like these often suffer from the common problem of never being able to see farther than their own nose; they constantly forget that we grow, and grow, and grow. Without meaning to sound pretentious and cheesy, here's a nice quote from a certain sci-fi series that came to mind: "It's our destiny to walk among the stars", and you can be damned sure that we will, providing we won't kill ourselves on the way.

Re: Why we are unlikely to ever leave the solar system.

#98

Post by scott_s »

jacobolus wrote: post #36
mmaunder wrote: post #35

I dislike the word "never". As individuals and as a species we are addicted to short term gratification measured in years or decades. We also have a narrow view of the concept of "self" and what constitutes consciousness and experience. If we could stand building for the future and experiencing by proxy, a few more options become available: e.g. We could transport a set of human "blanks" or a "blank" creating machine…

Okay. You just wave 5 or 6 magic wands and then it works out. Isn’t that precisely what the essay claimed?

I suspect most people have not read the full essay, so they never saw this paragraph:

The long and the short of what I'm trying to get across is quite simply that, in the absence of technology indistinguishable from magic — magic tech that, furthermore, does things that from today's perspective appear to play fast and loose with the laws of physics — interstellar travel for human beings is near-as-dammit a non-starter. And while I won't rule out the possibility of such seemingly-magical technology appearing at some time in the future, the conclusion I draw as a science fiction writer is that if interstellar colonization ever happens, it will not follow the pattern of historical colonization drives that are followed by mass emigration and trade between the colonies and the old home soil.

Many people here are arguing for "magic tech that ... does things that from today's perspective appear to play fast and loose with the laws of physics." I suspect that many of the people doing this either don't realize they are, and/or don't really understand physical laws as we currently understand them.

Re: Why we are unlikely to ever leave the solar system.

#99

Post by billswift »

hackermom wrote: post #97
jacobolus wrote: post #36

Earlier quoted context omitted.

Okay. You just wave 5 or 6 magic wands and then it works out. Isn’t that precisely what the essay claimed?

His point is that exactly every single notable achievement in the history of mankind has been preceeded by people saying things just like these - skeptics who keep saying "it can't be done" up until the very last second before "it" is done. It was said about crossing the seas. It was said about colonizing the surface of the planet. It was said about diving deep into the seas and it was said about taking off ground. I…

http://en.wikipedia.org/wiki/Columbus_Was_a_Dope

Re: Why we are unlikely to ever leave the solar system.

#100

Post by sharpneli »

waterlesscloud wrote: post #33
scott_s wrote: post #19

Earlier quoted context omitted.

The limits he talks about are fundamental. We would have to be very wrong about much of physics to invalidate his arguments.

It is virtually certain that we are very wrong about much of physics. Perhaps not in ways that solve these issues. But we're still almost certainly wrong about things we consider very fundamental.

At the same time we are very certain on some issues.

As an example there will not be a theory which says "You can lift yourself up" and suddenly people grabbing their own belts could lift themselves up into the air.

Any future theory will predict exactly the same things as current theories on the cases where current theories have been experimentally verified.

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