Reaching for Interstellar Flight

space.com ^ | 12/17/03 | Leonard David

[boris]

"Has it occurred to you that proving a point with negative evidence is poor logic?"

It impressed Fermi, and many others since. The entire argument, which I posted in shorthand because I am tired of repeating it, goes like this:

(a) We're children of a 3rd-generation star.
(b) If intelligent life is common then we are (among) the most primitive ones; there has been ample time for hyper-advanced technical civilizations to spring up before our advent.
(c) Some of them will be as curious--or more curious--than we.
(d) Some of them will hit upon the idea of launching a modest number (~100) of "Von Neumann robots". These machines, travelling at (say) 0.05 "c", are instructed to pick a star at random, go there, conduct extensive studies, build a copy of themselves, dump their entire memory into the scion, and then both 'parent' and 'child' probes each select another random star and the process continues.
(e) Some stars will lack proper conditions (materials) for constructing a scion, or the parent probe is destroyed. That's why you start with more than one.
(f) This process is guaranteed to result in a geometric explosion of probes, all flitting about and finding stuff out at an ever-increasing rate.
(g) Occasionally, a probe wanders home by random walk. The payoff is that it dumps the memories of itself and all of its ancestors; for a relatively small investment you get a gigantic payoff in terms of data. [Remember, you are a super-tech civilization which has had technology for thousands of years].
(h) There has been ample time--even at 0.05c--for every star in the galaxy to have been visited at least once. Where is "ours"? Actually, if intelligence is common, many races will figure this out [remember, we're dumber than they are, and we figured it out!] and there ought to be a traffic jam of probes buzzing around Sol.
(i) We fail to observe any evidence of even a single probe, much less a swarm.
(j) Therefore some assumption in this chain must be flawed. The key ones are [1] intelligent life is common and widespread; [2] technological means are sufficient to reach at least 0.05 'c'.
(k) Therefore either [1] or [2] or both must be false.

QED.

Fermi, being much smarter than us, simply asked his question; the rest was understood.

--Boris

[RadioAstronomer]

Explain how a Von Neumann robot could function the way you claim. Personally I think this argument is all wet. To even accomplish the task, each robot would have to completely recreate the infrastructure (i.e. from turning the first spade of dirt to making complex processors and propulsion devices at each viable location) needed to replicate itself prior to sending new ones off to the next star system.

[Alamo-Girl]

Thanks for the ping!

[inquest]

Where did you read that we're a 3rd-generation system? I thought we were 2nd-generation. How do we distinguish between the two?

[Junior]

I'm probably wrong, but I was under the impression that quantum tunneling permitted FTL travel; the particle literally moves from Point A to Point B without crossing the intervening distance. Theoretically, if the tunneling were instantaneous, the particle has "moved" FTL (though it really hasn't moved at all).

[RadioAstronomer]

Where did you read that we're a 3rd-generation system? I thought we were 2nd-generation. How do we distinguish between the two?

Could be both, however, a second generation star is not out of the question. This is just one site of many that postulates either: :-)

http://www.rwc.uc.edu/koehler/biophys/7b.html

[tortoise]

I'm probably wrong, but I was under the impression that quantum tunneling permitted FTL travel; the particle literally moves from Point A to Point B without crossing the intervening distance. Theoretically, if the tunneling were instantaneous, the particle has "moved" FTL (though it really hasn't moved at all).

The particle does cross the gap, but the tunneling isn't instantaneous. Part of this has to do with us not really knowing where the particle actually is before it crosses the gap. Tunneling phenomenon are really psuedo-FTL.

[RightWhale]

we observe LIGHT being too slow to escape from gravity wells

That's part of the problem. What we see is no more than an approximation of what is really happening. The speed of light is meaningless in the face of infinite refractive index.

[boris]

"Explain how a Von Neumann robot could function the way you claim. Personally I think this argument is all wet. To even accomplish the task, each robot would have to completely recreate the infrastructure (i.e. from turning the first spade of dirt to making complex processors and propulsion devices at each viable location) needed to replicate itself prior to sending new ones off to the next star system."

If you posit advanced nanotechnology, such objections become bootless.

--Boris

[irv]

You didn't answer my question.

Incidentally, every assumption in there is an ASSUMPTION. Unproven and, under current conditions, unprovable.

Your conclusion may well be correct, but your argument still stinks.

[greenwolf]

pyramid info scheme...

Is that only supposed to work within our own galaxy, or is it supposed to be intergalactic? I would guess that the distances between galaxies have to be greater than the distance between any two stars within our own galaxy.

Also is there not some third assumption in the picture, i.e. that the robot probes would be able to travel vast distances without suffering damage from debris, dust, and radiation?

[Brett66]

"If we are lucky…very, very lucky, we might have a solution to the propellantless propulsion side of this interstellar propulsion problem within the next ten years," March said.

Ok, this is fascinating. I recieved an email from Paul March about a year ago in response to a "Machian Propulsion" system I described on my website. He told me he's been working on the propellentless drive theory of Dr. James Woodward,the Woodward drive, as it's been coined.He said that they should have a working prototype for testing beyond the lab in couple of years, he even gave power/thrust figures for what he believes this inertial propulsion device can achieve. I never even recognized who Paul March was until I read this article.

My website reference:

Machian Propulsion

Woodward's Home Page:

Dr. James F. Woodward

[boris]

"Is that only supposed to work within our own galaxy, or is it supposed to be intergalactic? I would guess that the distances between galaxies have to be greater than the distance between any two stars within our own galaxy.

Also is there not some third assumption in the picture, i.e. that the robot probes would be able to travel vast distances without suffering damage from debris, dust, and radiation?"

Good questions. The original idea applied only to the Milky Way Galaxy. The age of the galaxy and the probable ages of advanced ET civilizations allow ample time for every star to be visited at relatively (sorry) modest velocities. 0.05 c is "assumed" to be within their capabilities. Other galaxies are MUCH further away and 0.05 c would be a stretch. On the other hand, their technology might be much more capable. (and, BTW, there is nothing prohibiting alien life forms which live for centuries or millennia, making slow trips much easier than for mayflies like us).

Regarding robot damage, of course. Remember though we are dealing with advanced technological civilizations 10,000 or 100,000 years more advanced than we. Self-repairing robots, nanotechnology, and other measures we cannot imagine could be applied to the problem. Plus, as I noted, you expect attrition, so instead of 100 probes maybe you launch 1000.

A civilization with technology 100,000 years beyond our own would probably not notice the difference in cost between launching 100 and 1000--or 10,000 such probes.

-------------------

If Drexler's projections for nanotechnology on Earth are even 25% correct, eventually economics will cease to be relevant. Literally anything could be made for almost nothing. In such a society, the only valuable commodities would be energy, creativity, and originality...

--Boris

[boris]

"Incidentally, every assumption in there is an ASSUMPTION. Unproven and, under current conditions, unprovable."

This whole thread is speculative in nature.

Refute my argument, item by item.

--Boris

[greenwolf]

I could think of one or two other possible assumptions being overlooked here, nonetheless a certain case could be made for thinking ourselves to be relatively alone based on the line or argument in question. Thanks.

[irv]

Refute my argument, item by item.

Negative arguments can't be refuted and you know it. They have no basis in fact or logic, therefore they are unresponsive to same. My original question was if you had any awareness that you were using such poor "logic.". I see now that the answer is no.

[mhking]

Just damn.

If you want on the new list, FReepmail me. This IS a high-volume PING list...

[Qwinn]

There's a thousand possibilities you could be ignoring.

A) Assuming there are more advanced civilizations (and I'm not even buying that as a necessity), what if Von Neumann robots -were- created at some point in time, and wound up being hijacked or misused to become a serious danger (think Stargate's Replicators) and are absolutely -banned- by those governments? It could be as unthinkable to take that risk again, for all we know. I came up with that within two minutes of reading your theory. I could probably come up with another dozen if I spent a day on it. All you're showing is a lack of imagination.

Now, as to your lack of logic:

B) There's a difference between "common" and "easy" or "quick". You postulate that if evolving species and advanced intelligence is common, it had to be quick too.

I also find the notion that intelligence is the "intent", or "endpoint" of evolution to be silly. Sure, ONCE intelligence is introduced to a planet in a particular species, that species will likely dominate their planet, but you still need the freakishly unlikely set of genetic accidents for it to happen.

Now, GIVEN ENOUGH TIME, even the freakishly unlikely becomes likely. The odds of intelligence developing through random mutation is an unknown variable X. X could mean that there's even odds that it'll happen once in a million years, once in a billion years, once in a hundred billion years - we have no idea. X could be anything. You are assigning a low value to X based on zero evidence. Even -with- "billions and billions", it may -take- billions and billions of planets working for fifteen billion years to produce the first half-dozen or so intelligent civilizations.

It may easily be that, given -another- ten billion years, there'll be a hell of a lot more advanced races out there, and we happen to be ahead on the curve. No one can know. But you're conveniently introducing your own timetable for the likelihood of such a thing occuring with zero data for backup beyond our own experience.

Qwinn

[magslinger]

Clarke's first law states that:

"When a distinguished but elderly scientist states that something is possible he is almost certainly right. When he states that something is impossible, he is very probably wrong."

[xrp]

Snowball Earth hypothesis??? Link please, sounds like a great read.