Over the years we’ve discussed many concepts for ships that could take us to the stars (they’re all in the archives), and none of them are without problems. Although Les Shepherd was analyzing antimatter possibilities by 1952 and solar sails were already coming into the mix, I’d argue that the first design that looked like a feasible way to get a human crew up to a high percentage of lightspeed was Robert Bussard’s ramjet. Introduced in a 1960 paper, the idea was the subject of Carl Sagan’s scrutiny in Sagan and Shklovskii’s Intelligent Life in the Universe (1966), but later fell afoul of an apparent showstopper: The ramscoop produces more drag than thrust.
It’s a measure of the magnitude of the interstellar problem that so many different concepts continue to emerge. Theorists have been banging away at starship engineering for sixty years and even longer if we go back to the musings of Konstantin Tsiolkovsky and early thinkers like Olaf Stapledon and John Desmond Bernal. When Sten Odenwald talks about The Dismal Future of Interstellar Travel, he’s reflecting what people who have tried to design starships, like Robert Forward and the Project Daedalus team, also understood in their day. There are ways of getting to another star with known physics but all require huge investment for very slow journeys. In this realm, ‘fast’ means ‘decades,’ and ‘slow’ can involve thousands of years.
The difference is that people like Forward thought we would make these journeys anyway. I found myself making this case in a recent discussion among friends where the key constraint seemed to be the lifetime of the scientists who planned the mission. I’ve argued before that we need to do away with this constraint and think more in terms of continuing scientific return across generations. If we could build a craft that could send back data from a nearby star within several hundred years, would we launch it? Not with today’s thinking, but if we look long-term and reach a point where we can afford it, I’m enough of an optimist to believe that scientific curiosity runs species-wide and will transcend our human need for quick answers. Nor does this mean we stop looking for ways to make the journey faster.
Multi-Generational Perspectives
Engineering a starship is hugely problematic, and although we’ve recently looked at how it might be done if (for some reason) we had to launch something in the near-term, I think we should back starflight off into a much longer time-frame. Dr. Odenwald mentions the ‘slow boat’ method, which has been a staple of science fiction since early stories like Don Wilcox’s “The Voyage that Lasted 600 Years (Amazing Stories, October 1940). Tsiolkovsky also wrote about such vessels. My guess is that all our efforts will take place within the context of a gradually enlarging civilization that is adapting itself to deep space conditions through large habitats that lead, ultimately, to star crossings.
Image: An artist’s impression of the outer Solar System over six billion kilometers from the Sun. Will our species move ever outward over the centuries to exploit these resources? Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)
We saw yesterday in Odenwald’s essay as well as Andreas Hein’s 2012 paper that the cost of even a Daedalus-style flyby would be enormous. But we need to place such costs into the framework of a culture that will not go interstellar before it has built out into its own Solar System. We can extrapolate where the world economy is going within decades or centuries based on our best projections, but it’s much harder to get a handle on how large a system-wide economy will eventually become. We also can’t project with any certainty what kind of technologies a culture that exploits resources on this scale will develop to keep itself functional and growing.
Doubtless scientists will continue to research ways to make fast crossings to the stars, and we can hope they succeed. At the same time, an expansion into the rest of the Solar System, one that could take centuries and still not exhaust available resources, would help us master not just better propulsion technologies but the critical issues of life support in closed systems. Large habitats on the model of O’Neill cylinders are not at all out of the question as populations begin to grow off the Earth, and the availability of resources — from Kuiper Belt objects, comets in the inner and outer Oort Cloud, ‘rogue’ planets moving in the interstellar deep — may well keep the wave of expansion in play. It doesn’t bother me in the slightest that such an expansion might take thousands of years to eventually arrive at another star. We can also expect the people that eventually get there to have changed along the way as the human race begins to fork.
Choice of Vehicles
Meanwhile, a healthy system-wide infrastructure in several hundred years may well be able to afford a Daedalus-style probe, but this is surely not the spacecraft it would send. As one branch of humanity continues working outward in worldship habitats without the need for a planetary surface, those within the system may well be able to build the needed tools for beamed laser or microwave propulsion at the requisite scale. We can hardly imagine these today because we lack cheap access to space, but a permanent human presence there changes the equation as we master the techniques for building large structures off-planet, perhaps with the help of nanotechnology.
Given the cost of sending heavy payloads on fast missions, we’ll surely explore small, robotic probes as we learn whether or not human starships can be designed for missions lasting less than a lifetime. I like Sten Odenwald’s enthusiasm for what we might do with virtual technologies:
When you subtract manned exploration, which is hugely expensive, and replace it with robotic rovers that relay high-definition images back to Earth, all of humanity can participate in their own personal and virtual exploration of space, not just a few astronauts or colonists. The Apollo program gave us 12 astronauts walking on the lunar surface, a huge milestone for humanity, but today we can do the Apollo program all over again and augment it with a virtual, shared experience involving billions of people! This is the wave of the future for space exploration, because it is technologically doable today and scalable at ridiculously low cost per human involved. NASA’s Curiosity rover is only the Model-T vanguard of this new approach to human exploration. More sophisticated versions will eventually explore the subsurface ocean of Europa and the river systems on the “Earth-like” world of Titan — perhaps by the end of this century!
Surely virtual reality and shared experience using rovers is in our future, and it’s likely it will inspire missions that push ever further out, to return the datastream that a curious public will demand. Those making the slow move into the outer system and beyond can take part in this, but so can any faster spacecraft we can engineer to create a datastream from another star. Can gravitational lensing methods — think Claudio Maccone’s FOCAL mission — help us communicate with robotic spacecraft on such missions? Perhaps ‘swarm’ technologies using myriads of tiny spacecraft can make interstellar crossings at a fraction of lightspeed, and as Mason Peck has suggested, return data via a round trip return to the home world.
The potential of artificial intelligence is likewise obvious as we ponder whether to send a crew of ‘artilects’ on missions whose length would challenge human crews. Perhaps some form of ‘mind uploading’ will be found that allows a human ‘presence’ aboard even such a ship as this. We can’t predict disruptive technologies, but it seems clear to me that within the context of slow, generational expansion there will be options for faster travel of at least small payloads. So I have to disagree with Sten Odenwald when he writes that “…we live in a universe where star travel seems permanently beyond reach in any kind of human future that makes scientific or economic sense.” I’ve said before that it is the business of the future to surprise us, but even lacking such surprise, a way forward emerges that is not inconsistent with what the laws of physics demand.
One thing that keeps being left out is the lengthening of the human lifespan. If we can’t live longer than 120 years or so, I do think we can at least maximize our productivity. My guess is that by 215 we will be able keep our minds and bodies functioning at near full capacity at well over 100. Then missions of 50-70 years start to look more feasible. I would also not be surprised if genetic engineering allowed us to enhance ability to live even longer within the next 1-2 hundred years. So maybe by 2215 one hundred or two hundred year missions are no longer necessarily multi-generational.
No need to take the lonnnnnnnnng view :-) One of these days, someone will demonstrate a Mach effect reactionless thruster and we will be go star-faring without mega-massive generation ships or TW lasers. The one thing about technology is that it is discontinuous. All of the naysayers begin with the assumption that we actually know everything there is to know. Michio Kaku once said that the neat thing about where we are scientifically is that we now know what we don’t know. He is, of course, wrong…we have no idea what we don’t know and I suspect that part of what we don’t know is how to do star travel in a way that seems to violate our current view of physics. Or as a science fiction writer, whose name escapes me right now, once said: “if we want to go faster than light, then we will…so there.”
So buck up…probably the day after tomorrow, some gal in her garage will invent a warp drive, take out half of Chicago when she turns it on…and we will be off to the stars next year.
It could happen….
Trivia:
The term “starship” was coined in the 1882 book “Oahspe”.
Can we do FOCAL much closer than 550 AU via synthesis techniques?
If reactionless propulsion or some warp drive were possible, One ascendant alien species would have had the means to turn the Milky Way into a dense urban hub by now. Which Means One of 3 things.
1) Can’t be done
2) We are very alone (no ETI’s for hundreds of millions of Light Years)
3) The 1st locally Intelligent Species to arise which has the potential to invent Advanced interstellar Propulsion systems (if it possible at all) is US.
Very likely One of the three is correct.
@Mike Jude I don’t think we will get very far with a Mach effect thruster because there is no space warp effect with that technology. A warp drive and negative energy are needed for FTL. I completely agree with you about the FTL though. There are not a lot of people who will want to sacrifice their entire lives to live in space in a generational worldship.
@RobFlores we don’t have yet the technology to see if the milky way is a dense hub. Were getting close though. We need interometers and polarized light detectors which require larger space and land telescopes. New and larger space telescopes being built.
Good article, Paul! I agree, we need to extend our plans for starflight into a much longer time frame- many, many generations, if we hope to make progress, even as we search for faster ways to travel. Otherwise, the limitations of physics combined with limits of our own impatience may stymie us.
The idea of embarking on ships that take many generations to reach a destination is troubling to many people (call it the Methuselah barrier), but if a robotic probe could be launched that would take longer than a single lifespan to return data, isn’t that still a worthwhile gift for our children’s children’s children?
I’ve noticed that the objections to starflight break down into several categories- mainly physical, technological, and social.
Argument #1 is the distance/time/speed argument. The stars are very far away- the nearest, Proxima Centauri is just over 25 trillion miles away from Earth, about 4.2 light years. Our Galaxy measures 100,000 light years across. At current spacecraft speeds (Voyager 1, etc.) it would take many tens of thousands of years to cruise to a nearby star. This is much longer than the whole of human history, and well outside of a spacecraft’s warranty. Thus, interstellar travel is concluded to be impractical.
The obvious objection to #1 is to travel faster, so the skeptics next examine this.
Argument #2 Light-Speed Barrier argument. No physical object can reach the speed of light, and nothing that carries energy or information can travel faster than this “cosmic speed limit”. Thus, humans cannot travel at warp speed and interstellar travel of the Hollywood fashion is not possible.
The obvious objection is that we can travel at any speed slower than the speed of light we like, even up to 99.9999% the speed of light without violating any physical law. At such speeds Special Relativity tells us that time dilation will vastly reduce the time of the voyage for the traveler. Thus, the next argument takes a more mathematical approach-
Argument #3 Near-Light Speeds As exemplified by Edward Purcell in his paper “Interstellar Communications”, the starflight skeptic calculates the mass ratios and energy requirements to reach near-light speeds with a massive rocket-propelled vessel. Typically a constant acceleration at 1 g is assumed, and the ship carries all the fuel required to fly out to another star, rendezvous, and return. The resulting numbers are outlandishly impractical and the skeptic concludes interstellar travel is preposterous for these reasons.
Adjuncts to #3-
#3 a: interstellar gas will become a deadly onrush of radiation at relativistic speeds and fry the space travelers.
#3 b: as ramjets were proposed to solve the mass-ratio problem, the skeptic rejects these as infeasible because the necessary reactions cannot be kindled and the ramscoop produces more drag than thrust.
The problem here is that the assumptions set at the beginning are bent heavily in favor of making starflight impossible. There is no reason to assume our ship must accelerate constantly and 1 g to near-light speeds, or that it must make a round trip that way, or carry all its own fuel from beginning.
Argument #4 Energy Economics Here, the skeptic uses simple mechanics to estimate the energy required to launch a probe or starship, and compares it to the total energy production of the human race to prove that we cannot ever afford to pay the cost of traveling fast enough to reach another star in a reasonable time.
Assumption: future humans will never be able to produce significantly greater amounts of energy than we do today. Obviously not necessarily accurate.
All of these “refutations” so far are based on basic assumptions which others feel are not accurate. You can’t invalidate the entire idea by highlighting one rather extravagant mission (constant acceleration rendezvous and return) and finding it to be impractical, or by drawing a line in the sand and saying “human technology will never advance beyond this point” (argument #4).g
Argument #5 Society Will Not Support Starflight This argument says that real interstellar travel is so expensive and difficult that no human (or, in SETI arguments, alien) society will be willing to pay for it- as summed up by this:
It is kind of interesting to see all these in one place! As the intro the Starflight Handbook says, I say all these arguments rely on very questionable assumptions and the road to the stars may be open to us in the centuries to come. #5 does make the important point that if we fall into apathy for space exploration, it won’t matter if we can figure out how to do starflight. We still won’t do it.
@Mike Jude
That makes about as much sense as saying that, if I want to jump to the Moon in a single bound, I will… so there. We can’t do everything we imagine, not if it isn’t in line with how the universe works (which is what the things we call “laws of physics” reveal to us). Great advances come from working with scientific laws, not fantasizing about what we could do if they didn’t apply.
We should investigate every direction, including the far-out ones like superluminal travel, but we must realize that universe may simply not work in a way consistent with our favorite space opera stories. And, as Athena Andreadis pointed out, ignoring this could well become the reason we never get to Alpha Centauri.
Paul’s article provides a good summary of many articles and discussions in recent weeks, which identifies a number of fronts for activity now which have the potential to enable options and alternatives in the near and far future which can engage broader humanity.
Then again I like the Lazarus Long approach of simply co-opting a starship. Or magsails (sans beam) could provide a slow boat to China for its economical and enterprising crew.
Personally I think ‘what we don’t know’ remains a big part of the solution space. We need to challenge the orthodoxy, particularly the orthodoxy within ourselves, to be open to the solutions we will eventually discover.
I am one of the millions of human beings who believe that travel to the stars will be in our collective future. I just suspect and believe that warp drives/ faster-than-light propulsion systems travel are highly unlikely to occur, sadly.
We’re talking about interstellar probes (and even manned flights) while living in a country that won’t even fund something like the Terrestrial Planet Finder. The U.S. has thousands of scientists and engineers who would welcome the chance to participate in an expanded space program, that controls its own currency and can create as many dollars as it wants to, and it “couldn’t” come up with the money (meanwhile giving trillions to people who already have trillions).
I have to admit to being extremely pessimistic unless there’s a drastic change in our politics and economy.
Andrew Palfreyman, the answer is: No. Simple physics means there’s no focus from the Sun’s gravity until at least ~550 AU, and probably further out due to the corona causing distortions, if you want a clean signal.
For all of you who are skeptical of FTL and think it is just a dream or fantasy at least admit that some things can be physically impossible based on today’s technology but theoretically possible and a reality in the distant future. For example: Christopher Phoenix argument number two is absolutely true but it does not disprove the potential that a warp drive is possible. Special relativity says that nothing which has mass can reach the speed of light without needing an infinite amount of energy or becoming infinitely massive and no humans can reach the speed of light but that is not true for ET’s who are more than 500,000 years more advanced than us.
Remember a warp drive drags it’s local space reference frame with it, so the spacecraft does not violate special relativity inside the local space bubble but space itself can be wrapped around the bubble faster than the speed of light since space itself is postulated to be able to travel faster than light such as the expansion of space as the result of the big bang. Space is the exception to special relativity because space does not have mass but it does have energy, the quantum vacuum zero point energy.
According to Lockheed’s secret SunkWorks project they claim that in ten years that they can make a fusion reactor which is “ten times smaller than current reactors”which “can fit on the back of a large truck!” We will still have to wait to see if it really works. http://www.reuters.com/article/2014/10/15/us-lockheed-fusion-idUSKCN0I41EM20141015
@Geoffrey Hillend
Except that warping space at the commercial level has NOT been demonstrated to be theoretically possible. Not by a long shot. Alcubierre’s metric is mathematically valid in the framework of General Relativity, but that does not indicate that it is physically meaningful or that we could practically construct such a drive. For one thing, the drive would require exotic matter with negative energy density (negative mass), if such stuff does not exist the drive cannot be constructed. And this exotic matter has serious problem associated with its existence as well (violations of the 2nd law of thermodynamics, for one thing). And we’d need several Jupiter-masses of the stuff according to one of our more optimistic theories.
This is compounded with the practical difficulties that the ship would not be able to steer or control the “warp bubble” from inside, and that it would destroy any solar systems it came near, and that superluminal flight would fry the travelers due to Hawking radiation according to those very same unsubstantiated theories of Alcubierre metrics . Glib pronouncements that we have the basic theory behind Star Trek’s warp engines that those old scientific dunderheads just refuse to look at because they are old fogies smack of pandering to popular fantasy.
And, finally, the Alcubierre drive (like any other form of FTL travel) would create time travel paradoxes, and it is suggested in the Chronology Protection Conjecture that instabilities would destroy any such structure before it could be used.
I would love to have a warp drive as much as anyone else, but my point still stands. The universe does not have to work the way our favorite science-fiction stories insist that it does. No matter how advanced a civilization becomes, its technologies will still be applications of the laws of nature and will follow through from the implications of those laws. If the light barrier is indeed impassible, we can’t engineer our way around this. Not unless nature gives us a loophole.
The problem is that faith in the near term physical reality of “solutions” to star travel like warp drives, FTL, uploading, etc. gives people impatience with and contempt for the real science and engineering that may one day get us there for real. Then they reject any serious considerations of the challenges involved because it is harshing on their squee. This is seen every time something having to do with a long-generation ship comes up around here- a bunch of commentators reflexively respond “no need to look at this stuff, ’cause someone is going to invent warp drive in their basement tomorrow”.
@Christopher Phoenix – at this point we really don’t know if the arguments are equivalent to those made against heavier than air flight or not. Your argument ends with the hope that they are and that star flight will be possible.
Certainly we should keep pushing the physics and technology to see where it leads to, but we should keep in mind that the limits are real. Theoretically we can “slow boat” to the stars with advanced technology.
However, the “easier” we make the technology, the more we run up against the Fermi question. One possible implication of Rob Flores “3 answers” (#2) is that habitable, advanced life bearing worlds may be extremely rare and therefore there are no attractive destinations, just places with raw materials to replicate traveling wordlets. I hope that is wrong and that answer #3 is correct. However it might mean that it may apply to the whole universe, not just our galaxy.
@Christopher Phoenix
“That makes about as much sense as saying that, if I want to jump to the Moon in a single bound, I will… so there. We can’t do everything we imagine, not if it isn’t in line with how the universe works (which is what the things we call “laws of physics” reveal to us).”
You are insinuated a false sense.
The laws of physics don’t deny Mike Jude the ability to jump to the moon in a single bound. Neither can they deny everything we imagine.
“As Shakespeare once said, ‘There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.'”–Michio Kaku
@Joëlle B.
You are insinuated a false sense.
Um, do you really think that physics imposes no limits on what we can do? Mike Jude cannot, and will not ever, leap to the Moon in a single bound. I specifically chose that scenario because it is so ridiculous that even the most starry-eyed dreamer will understand that there are some things we can imagine that cannot happen.
I can’t believe I even have to spell this out- do you really think there is some way that Mike Jude’s muscles can give him enough kick to give him over the 11 km/s needed to escape the Earth? All without having is body ripped apart by the acceleration of attaining those speed over the distance of one kick, burning up in the atmosphere from friction, and (assuming he miraculously reached space) dying of asphyxiation while getting a mega-sunburn? I suppose you think Superman is realistic too.
Other than reaching orbit by jumping, the list of things we cannot do within the bounds of physics includes pinpointing the position and velocity of an electron with perfect accuracy, building an engine that produces more energy than it consumes, creating or destroying a single electric charge, accelerate on object to a certain velocity without paying for the objects increase in kinetic energy as determined by KE=.5M*Vsquared, or changing the center of mass of a closed system. Read any good physics textbook.
I usually consider this guy who runs the “Do the Math” blog a bit pessimistic, but he hit the nail on the head with this blog post.
Without any sense of limits, we will never make any progress. And I never said that everything we imagine runs contrary to the laws of physics. I simply stated that our most cherished dreams of Star Trek style travel almost certainly do and we must be willing to realistically appraise that.
Yeah, and we should totally default to a guy who makes his whole image off of pandering to “geeky” SF fans who want their lightsabers.
@Alex Tolley
Exactly!
On the Fermi question- I am not convinced that there is a paradox, as we cannot be certain that our specific assumptions about the behavior of advanced civilizations are correct (unchecked exponential growth, for one thing). We have not yet conducted an exhaustive search for signs of advanced societies through our current astronomical and SETI programs. Nor can we rule out that Earth was visited before there were humans around to observe and record the visitors.
And, if aliens long ago launched Von Neumann probes, is it not possible that by the time they filled the whole galaxy, the probes had evolved to the point they no longer fulfill their original mission and seek resources for their own activities while ignoring Earth-like planets, for instance? A barren solar system with only comets and asteroids would suffice for them. We may not observe them because they are not interested in us.
Again, to Christopher Pheonix:
The laws of physics are not what are preventing Mike Jude from jumping to the moon, only the above limits you have forced him to be contained to in the example.
Some of the factors against Alcubierre drive expressed above are not in accord with current thinking about this admittedly highly theoretical subject. For example there are theoretical conjectures for generating negative mass and there are notions that no time dilation (or other relativistic effects) pertain to someone inside the bubble.
What we can and will do in the very near term (in the 2020’s) is search for evidence of gravitational waves through very long baseline radio astronomy; e.g. SKA. This type of research should help us understand more about space warping effects that transcend speed of light limits that orthodoxy would suggest are beyond our capabilities. The general relativity theory supporting Alcubierre space-time metrics may or may not result from this research, however evidence of FTL inflationary expansion of space itself is supported (although not proven) by our astronomical observations to date. Understanding more about the nature of the space-time fabric through observation will be a practical and publicly supported way to take gain the knowledge to take this concept to the next step.
Or, everything around us is built up by parts of Von Neumann probes. Humanity was build on a pile of Von Neumann junk. It stares us right in the face and it’s all we know, it’s our reality –thus making us oblivious to the fact that we never were alone. Maybe the planets around the stars are made from scraps coming from the universe-wide Von Neumann junkyard. Don’t forget, it’s was my idea ;)
@ Christopher
Also, I see nothing in physics or biology that would disallow a species similar to that of ‘Kryptonians’ [or even a universe very similar to that of Star Trek]. They will more than likely not look anything like us, so far as our anthropomorphic desires displayed in comics and other art, but to rule out extraterrestrial life and the diversity it may imply in correlation with our imagination as an impossibility is 100% erroneous. Do I know the specifics of how their evolution may have taken place and led to their relatively “superhero” state (as related to our human state)?–Nope. But that doesn’t mean a damn thing; I also don’t know the specifics of how life on our own planet started. Let’s find out!
As for quantum uncertainty, there is hot debate going on in uncovering peculiarities as we go deeper and start moving towards experimenting with the hypotheses that have given us such growing pains–i.e. in that, although true for uncertainties in states, the precision limit is violated if applied to measurement; violation of the Heisenberg uncertainty principle in the presence of closed timelike curves; and the elimination of uncertainty altogether in a MIW (many-interacting-worlds) approach to quantum mechanics.
Quantum phenomena modelled by interactions between many classical worlds
pop description: http://theconversation.com/when-parallel-worlds-collide-quantum-mechanics-is-born-32631
article: http://journals.aps.org/prx/abstract/10.1103/PhysRevX.4.041013
preprint: http://arxiv.org/abs/1402.6144
Open timelike curves violate Heisenberg’s uncertainty principle
pop description: http://phys.org/news/2013-02-spacetime-violate-heisenberg-uncertainty-principle.html
preprint: http://arxiv.org/abs/1206.5485
And if you’re adventurous, see also: http://arxiv.org/abs/1006.0338
Furthermore, we don’t have to really look to our imaginations at all to see amazing things taking place within the biological kingdom that, when applied relatively to humans, would be deemed super-heroic. A nice example is the Paratarsotomus macropalpis, which is able to run at 322 body lengths per second (and even on 140 degree F concrete). This is 20x more body lengths than a Cheetah’s ability, or a human running at 1,300 mph! Investing time in life’s peculiarities, like this particular case (and many more related, and yet to be discovered!), provides a tremendous base of inspiration for implementable technologies and insight into the potential of animal physiology.
http://www.sciencedaily.com/releases/2014/04/140427191124.htm
Whoops… “you are insinuating a false sense” somehow got outside of that blockquote tag. It is meant to be part of the full quote.
One final thought, Michio Kaku likes to classify technologies ranging from those that are possible within our current paradigm of physics (Class I) through those that are almost certainly impossible in the ultimate sense (Class 3)*. A few (Class II) – like traversable wormholes- cannot be completely ruled out for arbitrarily advanced civilizations until we have a better understanding of the physics involved. However, the chances of one working are iffy at best and would probably involve engineering on an unimaginably vast scale.
Without being able to speak about the ultimate limits physics places on even arbitrarily advanced societies, Michio Kaku could not hope to even hazard a guess at what science-fiction technologies are impractical or outright impossible and which we might someday possess. :-)
Too bad his TV show degenerated to the “whiz-bang wowee” approach of science popularization.
*Michio places only two in this category: precognition and perpetual motion machines.
And, if aliens long ago launched Von Neumann probes, is it not possible that by the time they filled the whole galaxy, the probes had evolved to the point they no longer fulfill their original mission and seek resources for their own activities while ignoring Earth-like planets, for instance?
Or alternatively their job was to seed the galaxy with life and depart the systems once that was achieved.
Unfortunately when discussing the Fermi question, the underlying assumption for any answer is that all ETI (or their machines) act similarly to ensure the solution is universal. How likely is that?
@Christopher
Insinuated* (used as a verb): in that the same way you are beguiled to ignore the laws of physics that allow Mike Jude to jump to the moon, he could also ignore the limits you set on him to disallow the jump; I mean, who are you but a nobody to Mike Jude?!
And you would seem more the geek for riding Kaku’s lightsaber and then proceeding to criticize him when he is not a part of the discussion to defend himself from unwarranted disrespect of his very important popularization of physics to the lay community. Obviously, I quoted the doctor to play off of Mike Jude’s comment and give the reader something extra to think about; nonetheless, by default in doing so, Kaku (and I) defaulted to Shakespeare, who has very little to do with “wanting lightsabers”, but a lot to do with dreams.
I hope you have sweet ones, while me and Mike Jude go jump some moons and you are left, by default, to your Star Wars conventions, drinking from your poisoned cup of whine, Horatio.
@Jöelle B
You have a very peculiar conception of physics. I have not “forced” Mike Jude to be contained by anything. His inability to jump to the Moon follows from basic physics as it applies to gravity wells, jumping, and the human body.
Consider. The force with which Mike Jude would have to kick off is determined by the speed he would have to attain in that one kick- the Earth’s escape velocity. To estimate this very roughly- lets say Mike Jude weighs in at 65 kg. (the average human mass). The minimum speed to reach the moon is 11,068 m/s (escape velocity). I will be generous and assume Mike’s legs can continue to kick off against the ground for a distance of 1 meter before he takes leave of the ground and the propulsive phase of his jump is over. So he must attain this speed over a distance of 1 meter only.
How much work must his muscles do? KE=.5M*V^2, so KE=.5*65*11,068^2= 4*10^9 joules, or 4 gigajoules. The average energy of a person jumping as hard as they can is listed as 3*10^2 joules at this Wiki page. Still think a person can jump to the Moon? But, wait, it gets worse!
S=.5(Vi+Vf)*t rearranging… t=S/{.5(Vi+Vf)}
t=1 m/{.5(0+11,068)} t=0.00018 sec.
Mike must attain this colossal speed in under two millionths of a second! What will be his acceleration?
d=.5a*t^2 rearranging… a=(2*d)/t^2
a=(2*1)/(0.00018)^2 a=620,000,000 m/s^2
Mike has to accelerate at a 620,000,000 m/s^2, wee-hoo. But how much force will he experience?
F=m*a F=65 kg.*620,000,000m/s^2 F=4.03×10^10 Newtons.
That’s 4×10^9 gees of force!! Mike will be smashed utterly. At this point I’m not sure any material structure could withstand these forces, let alone fragile human tissue. Fortunately they don’t have too, because our muscles cannot generate enough force to accelerate us this fast.
This must be why NASA is working on a new generation of crew carrying vehicles rather than simply imposing the cost-saving measure of having astronauts jump the much shorter distance to ISS. :-)
Note that all I used above were formulas from BASIC PHYSICS. Still think that physics has nothing to say about our ability or inability to do, um, things involving forces and accelerations like jumping to the Moon? Even the limitation of our bodies stem from things like the tensile strength of our tissues and the power our muscles can output.
I’ve not exactly memorized the powers that Superman has evinced over his career in comics and movies, however, those that I have seen have certainly violated numerous physical laws- flying in space without pushing on a thing (conservation of momentum), breaking the light barrier that way, traveling backwards in time… even his X-ray vision makes no sense. And the explanation that he gets his powers from yellow sunlight similarly makes no sense.
If in the broad sense you meant that an alien species might have a much tougher physiology adapted to the harsh conditions on their own planet, and thus possess apparently “superhuman” qualities (the ability to hibernate, greater body strength due to being built for a higher gravity field, etc.), sure, aliens might have some cool adaptations. But those powers might not be readily transferable to an Earth environment if, for example, an alien’s ability to fly depended on a much thicker atmosphere and lighter gravity field than Earth’s- or if the alien cannot eat any of our food.
But Kryptonians as shown in the various Superman comics and movies are not exactly realistic.
As to a universe similar to Star Trek- the various technologies portrayed are incredibly unlikely to ever exist in the forms shown on screen and the aliens are just people with some make-up speaking English. Let’s be honest, even if we DO invent an FTL drive the universe is not very likely to be like that at all.
Half the time the show is not even consistent in its timeline from series to series. It is one of those things you can enjoy, but only so long as you don’t think too hard about it.
As for Paratarsotomus macropalpis, that is an interesting little critter. :) But it is very unlikely a human size creature could run that fast because of the cube-square law. Little tiny bugs have so much less mass then us, the forces on their bodies from accelerating or falling cannot hurt them- while it is entirely different for us, and even more so for an elephant. If we jumped as high as a cricket does in terms of body lengths, we’d bound over buildings, but other limits keep us from doing that (like being smashed).
Jöelle, even our ideas about quantum uncertainty change in the future (and consider that those articles are talking about multiple universes and time travel, I suspect they are largely speculative), quibbling over how certain we are about certain aspects of physics won’t change the fact that the abilities of every civilization are ultimately bound by natural laws.
Also, keep in mind that future theories in physics must agree with the predictions our current understanding of physics where verified by observation and experiment. This is called the correspondance principle. We can state with confidence that we have some understanding of what is going on- lasers lase, semiconductors semiconduct, satellites go into orbit- and this understanding will apply to any civilization throughout our universe. They may understand things we don’t, but they will still be bound by what we already understand.
@Christopher
The key to your answers and overcoming your insinuation lies in understanding that everything you wasted your time typing can be circumvented within the laws of physics, even if we ignore violations (or unnecessary trajectories) of correspondence* [the same principle which the MIW team acknowledges in the above paper]; where the moon, Mike Jude, or the Earth are located; what they are and are not (or can and can’t be, given enough probability); what Mike Jude, or the moon, or Earth can become or protect herself with, so that irreversible mechanical deformation from gravity is irrelevant; and undiscovered laws or scalar dimensions (or potentials) evident to us through mathematics and our intuitive imagination.
“They may understand things we don’t, but they will still be bound by what we already understand.”
This statement is no different than sending Mike Jude to jump to the moon, because of something he said or halfway denying the existence of Kryptonians–So too, they may misunderstand things we do and bind us by what we don’t; unbound to all we understand, yet binders of all we can. (^_^)v
And violation or elimination of uncertainty, means certainty: a possible endpoint for our changing views. The good thing about these speculations is they can be tested, so that they are no longer speculation! :)
@Christopher, Jöelle
I suppose our hypothetical Kryptonian might be able to “jump” to the moon by some techniques:
1. Nullify gravity and wear a frictionless spacesuit.
2. Become inertialess and wear a frictionless spacesuit.
3. Jaunt rather than jump (c.f. “The Stars My Destination” – Bester)
4. ST transporter beaming.
5. Mind upload and reembodiment on the moon.
6. Warp/fold space so that the moon’s surface is but a short jump from the surface of the Earth.
Of course these “solutions” alter the conditions of the test (Kirk – Kobayashi Maru) in that we change the meaning of “jump” and/or allow technology to be used. The point is not to overturn physics, but to offer “jumping” alternatives that may be possible until proven otherwise, because, as Christopher points out, no evolved organism is going to be able to jump from our Earth’s surface to our moon using biological energy under current conditions.
Christopher Phoenix writes “Except that warping space at the commercial level has NOT been demonstrated to be theoretically possible. ”
It does not have to be proved to be an engineering possibility within human capability to be a useful concept for re-evaluation of aspects of the ET hypothesis. Since the metric exists, we might examine the possible consequences for a truly technically advanced civilization that might be able to engineer space in the necessary way. Since the rise of UFO reports, the typical argument among scientists, beyond the usual explainations, has been the impossibility of interstellar travel to debunk any reports of alleged UFO sightings regardless of the status of the observer, or the quality of the observation for the small percentage of reports that otherwise would be credible.
Also, as I understand it, the theoretical amount of exotic matter necessary has been reduced from something on the order of a Jupiter sized mass to something on the order of the mass of the Voyager probe. The radiation problem I thought was more of a problem for life outside but near the warp bubble than for life in the warp bubble.
I would also like to add that Kal-El a.k.a. Clark Kent is an especially exotic hunk of matter, who need not require any of that Alex Tolley!
Christopher Phoenix:
Exponential growth is not so much a conscious behavior, but the default consequence of self-reproduction and even the slightest tendency to colonize new territory. It takes very careful, conscious behavior to limit such growth as long as there is untouched territory available.
If we hypothesize that the Earth has been visited long before there were humans, we need to explain why the visits have stopped, and why no beings or their machines stuck around. Did they disappear only from here, or everywhere? And how could that happen?
Lastly, our solar system is every bit as useful as any other barren solar system, without making any assumptions about the ETI. Over the eons, it would not escape being used. Why would it? Why, especially, would it not have been used long before there were humans around?
There are, of course, answers to these questions, but most of them are very contrived, and leave one with the impression that the desired outcome has been postulated. Even the name “Fermi paradox” smacks of this, as it implies that the obvious solution is somehow out of the question: That we are indeed alone.
Alex Tolley:
True. The most likely assumption that could apply to all ETI is the simplest: They do not exist.
Re: exotic matter. Does not the very concept of a form of matter that no one has ever detected in the known universe, give one pause especially when one wants to use such exotic matter as a source of propulsion for the mythical warp drive?
@Joëlle B
Quite frankly, it is quite difficult to make sense of the gobbledygook you just typed… something about two speculative papers on timelike curves and the many worlds interpretation of quantum mechanics allowing people to circumvent classical mechanics and jump to the Moon?- however, I tire of this “clap you hands if you believe!” approach to science, so I’ll take you up on testing your speculations!
Go outside sometime when the Moon is out try jumping to it (take a running start if you have to). If you indeed get to the Moon, be sure to take so pictures and pick up a Moon rock for scientists to analyze to prove your story. Since you can magically make physics irrelevant you should have no problem with lack of atmosphere or intense solar rays. If you can do all this, return, and prove your story, I will concede the point.
After all, as Carl Sagan once said, extraordinary claims require extraordinary proof.
However, I hold the view that your attempt at trans-lunar jumping will get about as far as the guy in the Monty Python skit about jumping across the English Channel. :-)
So, go and do it and return with adequate proof- otherwise, stop jumping all over me for daring suggest that Star Trek TV series and DC comic books might not be an accurate portrayal of our future in space. Get it? Jumping all over me? Yes, I’m hilarious. :-)
By the way, Superman was made up by two high school students living in Cleveland, Ohio in 1933- I hardly need to halfway deny his existence, do I? He is fictional. If you don’t believe me go read theWiki article.
@Eniac
Of course, it is that “untouched territory” that is the problem- sooner or later, it runs out. Population growth is limited not by the organisms themselves but by the resources and living space in the local ecosystem. Population booms inevitably lead to busts.
And I can imagine lots of ways that “they” could suffer a collapse of culture or other calamity that leaves an area of space void of visitors for a while. Space voyagers are likely to be as bad off as Polynesians in their catamarans- many expeditions may not make it, and even successful colonies could lose the level of technology they arrived with.
Also, I find it peculiar that we assume self-replicating probes must be both immortal and intent on reproducing with the unrestrained enthusiasm of cancer cells. Wouldn’t such a machine prove a hazard to the very alien cultures that its creators sent it to find? Perhaps they find something repugnant in the idea of turning entire solar systems into a techno-scrap heap.
As for alien artifacts- here I begin wondering just how long advanced technology will remain recognizable as such once dumped somewhere. A 100,000 years from now, what would a smart-phone or crashed airplane look like? Could future archeologists find the rocket pads at Cape Kennedy? We can probably rule out a civilization on the scale of Earth civilization today having been created here by aliens in the past- or can we? Might we be likely to simply interpret the remains we see as being natural in origin? Not many studies have been done on this, disregarding “ancient aliens” pseudoscience.
One thing is clear. As our SETI searches continue and broaden in scope- from the traditional search for radio messages to attempts at detecting the activities of Type-II civilizations- continuing to turn up negative results will indicate that something is wrong with our basic assumptions, whatever that something is.
I think we should refine the statement that “we are alone”, though. A better way to state is that intelligent life may be such a rare outcome of evolution that the nearest places it arose may be far, far too distant for us to come into contact with it. That does not mean that distant galaxies in the universe may not be graced by conscious beings. Nor does it rule out microbes or even multicellular life nearby.
Christopher Phoenix: Yes, the territory runs out, but after that happens our own system would be settled, or not? Yes, an individual society might find a way to destroy themselves (completely, though? Without remnants to start over?), and leave some territory empty “for a while”. How long, though, you think, until neighbors move in on the newly vacated territory? A blink of the eye in cosmic terms, I would think.
And I am not talking about artifacts. I am talking about life itself. Life does not go extinct. Ours hasn’t in 4 billion years, despite being confined to one single planet. Spread it over the galaxy, and the chance of it going away is that of a snowball on the sun.
Froget about “contact” in the traditional sense. By far the most likely way we would ever make contact with space-faring ETI is by them having settled our system long ago. Again, this is because of the deep time noted by the above article. The fact that this has not happened means there was no such ETI anywhere within the spatial limits of where such ETI would reasonably spread to in a few Gy. Unless you posit interstellar travel to be impossible, that means the entire galaxy.
Intergalactic colonization can reasonably be held impossible, so I grant you that there may be other galaxies that are inhabited by ETI, but to me that is “alone” enough.
Of course, there might also be some very disciplined ETI out there in our galaxy who would not dream of ever sending colonists (or replicators) to neighboring systems in a billion years, but I find that very hard to believe.
“After all, as Carl Sagan once said, extraordinary claims require extraordinary proof.”
Not really. All claims require the same level of objective evidence. This claim has been used to simply discount much evidence that does not come from the “right” institutions, people, journals ect. in spite of reported or demonstrated facts.
@Christöpher Phoënix
Theoretical would be a better word for those two papers, and yes they are very testable (as discussed! read read read & calculate) and I encourage you to explore further (as none of them initially necessitate time travel and can be done by current technology cf. http://arxiv.org/abs/1401.0167 ). Investigate all authors involved in the links above in the previous post, for good reading; they are even very accessible for dialogue if you have questions!)–in doing so we may tackle quantum gravity and unity between quantum and classical mechanics! VERY EXCITING times in this Golden age of physics. I am very proud to be alive during this period of humanity’s existence and it is completely OK to be optimistic about how far we’ve come and how far we’ve still got to go!! Of course it is the scientific way to be reasonably skeptical, but I am a light-hearted individual, who likes the most bang for each buck in every moment of life. I am simply contrasting your abhorrent skepticism with playfulness.
I apologize if what I typed looked as ‘gobbledygook’ to you; maybe it wasn’t as effective as it could have been due to the reader’s (un)familiarity with imagination, Shakespeare’s work, the above articles linked and mythology :) )–an extremely rich cultural contribution we have inherited, which, in another universe, may have taken more hold than it has here [though, as far as we’re concerned in that regard, English has become the dominant language on the planet in this universe, whether we like it or not XD (very fun using it, if I might say!)]. Think how different cultures paint their bodies, wear costumes and partake in a plethora of diverse rituals and arts–if we are a part of a collection of universes, in the same way we’re a collection of particles, planets, star systems, galaxies, superclusters etc., then the probability subsists for such evident surrealistic reality if you ever get the hints, and we should be prepared depending on the success of the experimentation, tests and where they can lead if we can get rid of our inhibitions! On the other end of the circuit, who knows who you’ll contact–could even be another you! :D
Of course the ideas must be tested [the faster the better], but it got me excited!
@William F Collins
Using the Casimir vacuum in quantum field states is usually doctored up as a means to overcome the negative mass requirement. The problem is the averaged null energy condition, which can be falsified, but we’re still not quite there yet. Exotic matter has not been observed at all, and we probably won’t ever find anything quite like it if we’re stuck on the ground, or even our own solar system; at least that’s how it would appear at this point in the game. Right now, it simply doesn’t exist. :)
There are a few CD posts on wormholes and time travel (some of which may be out of date per the <Voyager probe mass requirement as brought up by Robert), but here are ones that may be of immediate use for educational purposes (arXiv is also useful, but flooded with some fodder you may have to keenly sift through with particular discernment and Christopher Phoenix-like skepticism): :)
https://centauri-dreams.org/?p=13568
https://centauri-dreams.org/?p=24183
@William F Collins
Another thought–
Some background story on how ‘exotic matter’ and traversable wormholes came to be can be found here, thanks to Al Jackson: https://centauri-dreams.org/?p=31687#comment-122687 & original paper here: http://authors.library.caltech.edu/9262/1/MORprl88.pdf
As the above example teaches us (and many more, unsaid in this post), and with much love and regards to Dirac, I think it is important to take Martin Reese’s position of “science fiction leads to science” approach, (cf. https://centauri-dreams.org/?p=31230 per Gregory Benford, 2013) and Einstein’s approach to imagination… We won’t get anywhere if we don’t push ourselves to think in different ways and overcome our limits to escape our impending doom! We should carry ourselves in a way that expresses supramundane freedom and unshroud all doubt, all of the time.
Robert:
I am afraid you are wrong and Carl is right. In statistics, this is known as “adjustment for multiple testing”, and in science, more colloquially, as “publication bias”. An extraordinary claim is one that will be tested much more often, and negative results, as usual, will generally be disregarded. Therefore, we need to put a higher threshold on positive evidence for extraordinary claims.
ENIAC, to me the origin of the expression “Fermi Paradox” is crystal clear as it came from an incident where Fermi was expressing surprise at the belief in a Milky Way full of ETI’s by colleagues who simultaneously acknowledged that their trace was not already here on Earth. A mighty paradox indeed! Today ‘Fermi Paradox’ is typically put to a slightly different purpose were it may mislead a few.
Here is a documented history of the origins of the Fermi Paradox, courtesy of the Los Alamos National Laboratory (LANL):
http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0055&numPages=20&fp=N
The document in PDF format:
http://www.osti.gov/accomplishments/documents/fullText/ACC0055.pdf
To quote:
“Enrico Fermi’s famous question, now central to debates about the prevalence of extraterrestrial civilizations, arose during a luncheon conversation with Emil Konopinski, Edward Teller, and Herbert York in the summer of 1950. Fermi’s companions on that day have provided accounts of the incident.”
“Therefore, we need to put a higher threshold on positive evidence for extraordinary claims.”
Well said, and valid point. Although, if the doorsill dilates, I’m going through!
And thanks to ljk for the links.
@Joëlle B
Joëlle B, I am not a humorless nerd with no interest in history, mythology, literature, or capacity for imagination… I have read Shakespeare and am familiar with the above quote (Hamlet, Act I, scene V). I read widely in mythology and folklore. I have always enjoyed both science fiction and some fantasy. And I also have read the work of famous authors such as Hemingway, Chekhov, and Bukowski, so I am not ignorant of modern literature. Neither am I a snob- Edgar Alan Poe and H.P. Lovecraft rank highly amongst my favorite authors. :-)
So I hardly think it is fair to insinuate that I have little education or interest beyond the domains of science and mathematics. And it is best to refrain from statements like the yours above if you want to engage in a serious discussion with someone.
There is a certain saying I like- “Keep an open mind, but not so open that your brain falls out.” :-) I try to keep an attitude of open but rigorously informed skeptical inquiry. In a field as nascent, oft ridiculed, and prone to wild hypothesizing as interstellar flight you need this attitude.
I think that I should explain my original “bone of contention” with Mike- I was objecting to the attitude that it is inevitable that we shall invent FTL travel, simply because we have the desire to do so. In order for us to be able to travel faster than light, the universe will have to turn out to operate under laws of physics that allow for loopholes around the light barrier.
We can’t safely assume that the universe will turn out to work a way in which we get we want, just because we want it. If that was so, we would have invented perpetual motion machines centuries ago.
I wholeheartedly support all serious efforts to investigate possible means of FTL transport like wormholes and the like. It is very exciting to live in an age where the mathematics of such things can be assigned as homework in a class on general relativity. And, in the long view, if wormholes can be used for interstellar travel by very advanced civilizations, it will totally change our outlook on starflight… but we must also be prepared to confront the possibility that traversable wormholes may not be possible in nature at all.
In the meantime, decades of high-energy physics experiments have accelerated subatomic particles to almost the speed of light for decades with no trace of entry into a superluminal world. No speculative method of “warping” spacetime has emerged that does not require vast quantities of exotic “negative matter”. And there is no verified observational evidence for wormholes or any other kind of FTL travel so far… nor is there an easy solution to the causality paradoxes they could create.
I think we should not ignore tedious, but basically possible concepts like long-generation ships in favor of fantasizing over methods of travel that so far have not proven themselves capable of moving so much as a single electron- let alone a human.
By the way, I would absolutely love if I were to be proven wrong and a wormhole to Gliese 581 opened in latter decades of the 21st century, but it just does not seem very likely. :-)
“And it is best to refrain from statements like the yours above if you want to engage in a serious discussion with someone.”
I feel that the discussion exchanged between us has been deeply important, at least personally, and I thank you for being a special kind of person to allow me to engage in unique introspection.
“Keep an open mind, but not so open that your brain falls out.”
It is long fallen; and it might be because I often hold the opposite view.
Cheers.