Colonizing Space

 I'm a fan of shows and movies that depict the colonization of space: Firefly, The Expanse, 2001 a Space Odyssey, etc.     I'm a true believer: Unless we manage to destroy ourselves first, the Human Race will eventually have extensive colonies in space.

 Space colonies are a lot different than colonies in the new world, India, China, Africa, etc 4 centuries ago, or by various cultures around the Mediterranean and other places 2000 years ago.   For starters, there were already people living in most of these places--they had air to breathe, soil to plant crops in, etc.  This is not true in space.  We will either have to bring these things with us or make them there.  Colonization opened people up to new diseases and other problems in the old days; that will also be true of space: Radiation poisoning, lack of gravity, price of air and water, etc.   My dad, who worked for decades designing satellites, is skeptical that we will ever be able to overcome these, but I think we will.  But it will be hard and it will take much longer than people like Elon Musk imagine.

 The first nasty problem is the difficulty in getting people and goods from Earth's surface into space.  This is very hard, but there's nothing completely intractable about it.  Chemical rockets can do it, but at great expense.  SpaceX, to their credit, have moved the needle considerably.  Several science fiction writers have proposed some sort of fusion rocket, which can be profoundly more efficient.  This will require a breakthrough to achieve, although it's superficially plausible.  Several SF stories, Such as The Expanse and Firefly have followed this route.  Breakthroughs, unlike more straightforward engineering, are difficult to predict, but I understand enough of the physics to be pretty confident that the breakthrough will happen, most likely in the next half century or so...I'm guessing it will be some sort of rocket fueled by Nuclear Fusion, but I expect to be surprised...

The next problem is gravity.  It turns out that humans need some gravity to be healthy, although we can tolerate its absence for a little while.  Many SciFi stories imply or require some sort of artificial gravity--Star Trek and Firefly are two notable cases, although little detail is given. Gravity Plating, as suggested by Star Trek, will require a pretty big breakthrough--comparable to the Warp Drive of that same milieu.  It's plausible that they are related--In Einsteinian General Relativity, gravity is an artifact of the warping space by large masses.  There may be other ways to warp space, ways which allow faster than light travel or gravity plating, but these are completely outside our present understanding of physics.  

 The Expanse does away with artificial gravity: they make it the old fashioned way, by accelerating.  In space ships, they are designed so that thrust is aligned with the axis of the ship, and any acceleration or deceleration gives the occupants a pretty realistic impression of gravity.  In the stories, which are mostly about warfare in space, accelerations well over 1 G are commonplace, but I think the vast majority of ships will remain comfortably 1 G or less the vast majority of the time.  The second way, of course, is to spin things--centrifugal space ships.  Several of the space colonies in the stories are asteroids, which have been spun up to create artificial gravity and hollowed out.   A little engineering shows that this is implausible.  A 1 G force on a several mile long cable exceeds the tensile strength of most rocky-based materials, including iron.  Centrifugal colonies will be largely artificial and their diameter will be only a few miles at most.    They may be very long--more like O'neill cylinders and less like those envisioned by von Braun and Chesley Bonnestal.   They might be made from material harvested from asteroids like Ceres, but they will not simply be those asteroids.

Present chemical drives can only produce an acceleration sufficient to get out of the earth's gravity well for a few minutes.  But if there is some sort of fusion drive that can produce a sizable fraction of a G for weeks on end, this will have a profound effect on travel around the solar system.  A ship that can accelerate for many days at one G can go to Mars in a few days.  This would profoundly change economics of a colony.   It could even bring the duration of a trip to another star down to a few decades. 

The third difficult, but not intractable problem, is radiation.  All manned space missions so far have been one of two things:  very short or, beneath the van Allen Radiation belts, which protect us from a lot of radiation.  A colony on the moon, Mars, or in a space station or elsewhere, will need considerable radiation shielding.   The simplest way to do this today is using many feet of shielding.  Heavy metals like Lead are the most effective by thickness, but a much thicker layer of dirt or water is much more effective.  I'm think that most space habitations, including those in centrifugal stations, will be protected by ten meters or more of whatever material is most convenient.  Digging deep underground will be the simplest way to provide this on a planet or moon, but an O'neill cylinder will need to have a thick shell of some sort..

 Water is relatively common in space, but it will be a limited resource for most colonies because it'll need to be mined and transported.  Air is a little more problematic, but not really.   We can breathe any non-poisonous gas mixture that contains enough Oxygen and CO2.  On earth, Nitrogen is most convenient and likely will be in space too, but we're far from limited.  Oxygen can be made from water and other things by Electrolysis and is a byproduct of photosynthesis.

 We will need plants growing in space to feed ourselves.   Simply dedicating surface area to plants is not particularly efficient: The most solar-efficient plants are well under 1%, where present photovoltaics can easily do 15%.  Put photovoltaics on all possible surfaces and grow plants underground under efficient electric lighting.  The photovoltaics are much more tolerant of radiation than plants are and are relatively easy to replace, and to manufacture from materials that we already know are on The Moon and Mars and other objects.

Presuming we don't drive ourselves extinct first (and Elon Musk and Donald Trump are presently the leading individuals working towards making us extinct)  I think we will have permanent colonies in space by 2050 or so, and self-sufficient colonies some time after 2100.  The sorts of populations on Mars and Ceres envisioned in The Expanse are unlikely to occur until there is a major breakthrough, such as the Expanse's Epstein Drive, but I'd think that by 2200 there will be tens of thousands of people living, breeding and dying entirely in space.  Far from the millions portrayed by the Expanse. 

Who Was Reverend Book?

One of my favorite TV shows, 2002's martyred Firefly series, had several interesting characters.  It takes place in an imaginary solar system where there are dozens of habitable planets and moons, some of which are high-tech, urban and modern, while others are rural or even backwards.  The show takes place six years after an interplanetary civil war, after which the urban "central alliance" worlds imposed a police state over all the others, but with somewhat limited reach imposed by distance.  The circumstances present many opportunities for interesting contexts for the writers to tell their stories, putting horses and space ships in the same scenes, and allowing all sorts of social circumstances to be considered.  So much more could have been done with the show had it been continued.

One of the interesting characters is Reverend Derial Book.  He had been a monk in an abbey not too far from the Persephone Spaceport--as he puts it "out of the world" for a time, when he catches a ride of the show's namesake spaceship, the Firefly class "Serenity".  He proves very knowledgeable about spaceships and many other things, especially things related to weapons, small force fighting and apparently espionage, and has an identity card which gives him surprising rights in the alliance.  All of this is implausible for the preacher he purports to be.

My theory is that during the war, he was a secret agent for the Alliance, possibly even a highly trained Operative.  After the war, he didn't want to do this sort of work anymore, but was privy to many secrets that needed to be kept.  The deal he worked out with his bosses was that he spend some period--probably five years--completely out of the world, and was prohibited from selling his expert services and knowledge, so he couldn't work as a consultant of some sort.  Moreover, he'd done sufficient bad things that he really didn't want to be in the spy business anymore, but had earned a permanent "get out of jail free" card with the Alliance.  The abbey suited him well--it fit his new-found religiosity and allowed him to be out of the world for a while, but after the five years were up, he could go back out.  He enjoyed space travel and had many skills that would be useful, so he took a ride on what appeared to be a tramp freighter, and was in fact a pirate ship, and after the first adventure, joined the crew.

His background prevents him from telling the rest of the crew what his true history is, especially since the Captain and Zoey had fought against his side in the civil war, but he's realized that his ideas about freedom and civilization are more or less aligned with theirs, and besides, it's exciting and fun for him.  Eventually, he'll probably tell the captain about his activities during the war, but probably not for a long time yet.  As it happens, he was killed by Reavers in the movie Serenity before this occurs.  I regard the events of the movie as non-canonical and perhaps even retcon, although much of the movie does extend the story of the series.  In particular, I think Book and Wash's deaths were intended to terminate the story and make reviving the series impossible rather than being a real part of the story.

Mass of the Solar System

The Sun is 99.8% of the mass of the solar system.  Jupiter is about 70% of all the mass in the solar system that is not the sun.  Ganymede, the Moon, and all the dwarf planets and moons are all less massive than Mercury, most by a lot. The total mass of the asteroid belt and all the comets is around 3e21...way less.   It's remotely possible that there's something big in the Oort cloud, but unlikely.

The lightest brown dwarfs are believed to mass abut 2.5e28 kg, roughly 13 times heavier than Jupiter.  The lightest actual stars are believed to mass about 1.5e29, about 75 times the mass of Jupiter. 

The solar system is the sun plus little stuff.  There will never be another sun in the solar system, unless it captures a passing star.


mass in kg, diameter and distance in km

Name	Mass	Diameter	Distance from Sun
Sun	1.9891e30	1.39e6	0
Mercury	3.3e23	4889	5.7e7
Venus	4.87e24	1.20e4	1.08e8
Earth	5.97e24	1.27e4	1.50e8
Mars	6.42e23	6779	2.28e8
Jupiter	1.90e27	1.40e5	7.80e8
Saturn	5.68e26	1.16e5	1.43e9
Uranus	8.68e25	5.01e4	2.87e9
Neptune	1.02e26	4.92e4	4.5e9
Planets	2.68e27

Technical Errors in "The Martian"

Andy Weir's The Martian is one of the most technically accurate science fiction stories of all time, although it's not perfect.  I just re-watched the excellent movie, which followed the book unusually well.  This critique is based on the movie:

Martian atmosphere is about 1/10th that of earth.  The wind would not carry all that much energy, even if it's blowing 200mph, and it's hard to imagine it knocking over the MAV or carrying enough sand that the sand might do it.  The pictures of dust devils taken by the rovers are scrawny little things.  It is plausible that it might cause flight in lightweight things that aren't fastened down properly, such as satellite dishes, so the incident that seems to have killed Watney is remotely possible, but the crew would have simply hunkered down and ridden it out.

The Aries 4 MAV is already on Mars, 4 years ahead of its use.  Mission planners expect it to still be standing when the Aries 4 mission arrives, despite frequent sandstorms that apparently can knock a MAV over?

It is inconceivable that a month long surface mission wouldn't have several redundant transceivers that could quickly reestablish communication between a marooned spaceman and earth, even if the primary went back into space with the rest of the crew.  For example, I'd think each rover would have had a high gain antenna analogous to the one on Pathfinder--about a foot in diameter: a phased array with relatively low bandwidth and only needs to be aimed in the right general direction to obtain maximum gain.  Not quite enough bandwidth for SDTV video, adequate for voice, and more than adequate for TTY and still photography.

It doesn't make much sense to have a specialist botanist on an early Mars exploration mission.  A different specialty scientist who happened to have a background in botany, perhaps, but not a specialist.   Had I been in Andy Weir's place, I'd have had Watney have been a farm boy who grew up to be a scientist (geologist perhaps?) and astronaut.  Growing potatoes in martian soil and human manure is pretty basic farm stuff.   I'm pretty sure I could do it and I'm not a farm boy or botanist at all.

Watney manages to keep his potato harvest healthy for over a year after the breach, in the same atmosphere he's living in.  It's probably impossible to keep bacteria and fungus from his own body from infecting them.   I can't keep potatoes for more than a few months, unless I freeze them.    The originals from earth probably survived this way too: vacuum packed and frozen.  He'd have protected his harvest exactly this way, and they would have survived the HAB breach, and he could have started up his garden again.

The HAB is soft skinned.  This is plausible as a covering for non-human stuff and even short term habitation, but unless there is some sort of magic radiation shielding developed between now and then, totally implausible for a month long habitation.  The astronauts might survive, but probably not for long enough to make it home.  I think the only real answer is to put the dwelling underground.

The same point holds for the Hermes interplanetary ship.  They got a lot right for the Hermes design, but there's no evident shielding, which should probably be ten feet thick or more around crew areas.

A great deal of space on the Hermes is given to human-occupied areas in microgravity.  I would doubt there would be many--airlocks and docking berths--but you wouldn't expect the astronauts to need to go through them very often.

The calculations Rich Purnell needs to solve to work out the maneuver are mathematical and demand high precision, but are not especially complex.  He wouldn't need a supercomputer to solve them.  The laptop on his desk would be ample.  (had he been doing it in 1966, he might have needed a supercomputer, but the PC I'm using to type this is about 300 times faster than a CDC 6600, the fastest machine of 1966).   Even if he did need a supercomputer for some reason, he wouldn't have needed to leave his office to do it.  (that said: I met an "Orbits" guy when I worked at Lockheed Missiles and Space.  The eccentric Rich Purnell character is totally plausible.)

The MAVs (both Aries 3 and 4) are entered through an airlock in the middle of the floor.  Underneath that floor is the second stage of the ascent rocket and underneath that is the first stage.   Wrong.  The astronauts would climb up the MAV on the outside and enter through a door in the side.

When Watney enters the MAV with his EVA suit on, he enters through this same airlock door, and closes and fastens it.  It is obviously a big heavy thing.   I'd think it'd have been among the first things to be tossed overboard.

The nose cone is shown sliding right past the MAVs attitude control jets.  Watney is going to need those.  He'd have figured out some way to guarantee not breaking them.

I don't understand why they needed to blow the airlock door.  They can override other safeties, why not that one?   It does make a fun plot element though.

We see personal laptop computers from Commander Lewis, Johansen and Watney, and we can be sure the others left theirs behind too.  Why is it that only Lewis has recorded music on hers?


addenda:
Water has recently been discovered on Mars, trapped in rocks, plentiful and reasonably easy to obtain.  This spoils one of the central plot elements, although Weir couldn't have known that when he wrote the book.

I read Weir's latest, Artemis.  It's almost as good as The Martian.  

SETI

I am certain that there is extraterrestrial life out there and I am pretty sure some of it is intelligent.  The universe is so vast and the number of planets so enormous that anything else strains credulity.   But the distances are so vast and the number of dead planets so enormous that the chances of us discovering them or them discovering us is so small that the possibility of that happening also seems pretty small.   The distances are enormous.  Most of the stars we see are hundreds of light years away and those are our nearby neighbors.  Our galaxy is over 100,000 light years across.  The nearest big galaxy, Andromeda, is 2.5 million light years away.   The laws of physics that we know preclude travel faster than the speed of light.  To send a fleet of a million probes, to visit every star in our galaxy, traveling at light speed, would take half a million years.

But, you ask, isn't it possible that there's a way to travel faster than light?  You'd have to do this by warping space through a higher dimension, most likely time.  We know a little about this: Galaxy-sized masses warp space enough that light is curved a few micro-seconds of arc.  Enough to detect with powerful instruments, but the space-warp available from this is not actually any faster than the speed of light.  I remain hopeful that some unknown technology allows us to do this but we are very far from any plausible breakthrough.    Let's say that such a breakthrough occurs--we can go 1000 times faster than light--our million probes would still take at least 500 years to visit every star.    Even at 1000 times light speed, our nearest star is a day and a half away.

What if some other intelligent species is out there, looking for us?  If they already have 1000x light speed travel and did a search using a million probes to find us, they are at least a few hundred years more technically advanced.  Could we, using the highest technology available to us, successfully hide from the best technology the 18th century had to look for us?  Of course we could.  We could paint an orbiting telescope flat black and spy on them from space.  We could find places where they aren't and send a lander--appearing at worst to be a meteorite.  We could send out drones from that lander to watch from a distance.  We'd design the drones so they'd easily be mistaken for a bird or some other creature.

Or you point out that we're sending out massive quantities of radio waves.  That's true, but each of these signals, on an interstellar scale, is pretty weak, and while individually coherent, from 100 light years away it's likely just a bunch of incoherent noise, and compared to what the sun generates, pretty weak at that.   It may be enough to help them find us--but the waves only travel at light speed, which means the probe that detects them must be within a sphere about 100 light years in radius of us.  It shortens the search, but only a decade or so. 

The bottom line is that an intelligent extraterrestrial that wants to hide from us, will successfully hide from us.  If they want us to see them, we will.   Searching for ExtraTerrestrial Intelligence is basically a fool's errand at this point in human development.  Once we have the technology to actually embark on the faster than light search, this may change.  But for now, if they're looking, they're gonna find us, whether we're helping or not.

That said, I certainly don't object to privately funded SETI projects.  There's lots of peripheral research being done, some of which may prove useful regardless of whether there are extraterrestrials involved or not.  The SETI Institute in California does lots of space-related research, lots of it interesting and potentially useful, and as far as I can tell, only a small fraction is actually in pursuit of aliens.  It's just that I think there are better things to spend my tax money on.   On the other hand, I think the search for extraterrestrial life in the solar system is a worthwhile goal.   We're still in the early days of exploring the solar system and it's entirely possible that there's life on one of the moons of the gas giants, or much less likely, on Mars in the dim past.  Odds are very unlikely that it's even multicellular life but whatever it is, we'd like to know about it.   (life has existed on earth for well over 3B years.  Multicellular life for less than 1B)

addenda 18Dec2017
Over the weekend, the pentagon's own UFO research organization came to light.   There are lots and lots of UFO sightings, many of them by completely credible people.  I've seen two myself.  One turned out to be a rocket launch from nearby Vandenberg Air Force Base in unusual atmospheric conditions, which left a long glowing trail.  The other was almost certainly a meteor falling close enough that I could see it tumble and burn, but it might have been falling space debris.   Strictly speaking, there was a time when, for me at least, they were unidentified.  I know someone who managed to get a flying saucer photo published: it was a lid from a cooking pan, tossed in the air and spinning fast, and in poor focus.  An at least superficial investigation should be easily available.  A central clearing house can quickly dismiss the vast majority for what they are.  Occasionally something mysterious does turn up, and these should be investigated.  Yes, there are plenty of cranks in the world

Terraforming Jupiter

One of my favorite TV shows was the short lived Firefly series.  The premise of the show was that the Earth had been "used up" and that a bunch of humans had headed into space, finding another star system with dozens of planets that were near enough in size and temperature that they could be terraformed and turned into habitable enough planets they could be colonized.  The recent discovery that there are 7 roughly earth sized planets in the "habitable zone" around the red dwarf star TRAPPIST-1 suggests one way this could happen.  TRAPPIST-1 is about 40 light years from earth, which would take thousands of years to reach with a plausible rocket, which predicates effective hibernation or perhaps even full stasis for such a colony to get there.

But there's another alternative.  What if we blow up Jupiter and move the fragments into orbits close to that of earth?   Jupiter is a gas giant, which means it's mostly hydrogen, but there's a metal and rock core--it's been catching asteroids, meteors and comets for 5 billion years.  Estimates are that the core is between 12 and 45 times the mass of Earth.  The show predicates cheap, safe energy of sufficient efficiency that it can power a Firefly-sized spaceship between planets with no visible fuel tanks.  This can only be nuclear or perhaps something even better.   Since we don't really have such a technology yet, it's not exactly clear how to make a bomb that would get deep enough into Jupiter to blow up the core into suitably sized chucks, but if we have such an abundance of nuclear or better energy, we can probably figure that out.  Once the Jupiter fragments are out there, we can use solar sails or our nuclear rockets to move them into orbits at a distance from the sun to keep them comfortable, and at a sufficient density to accommodate billions of people fleeting Earth.  This will take a lot of energy, but the spin and kinetic energy of Jupiter is substantial and if we can figure out a way of redirecting it, there's more than enough for the purpose.

Once we have a bunch of rocks that are big enough to have gravity appropriate for human habitation--between .3 and 2G--they will quickly turn themselves into spheres on their own, and the terraforming process can begin.  Left to their own devices this would take a billion years and if we're fleeing Earth we won't be able to wait that long, but presumably the terraforming technology will be able cool them down quickly enough.

Since we're engineering these new planets, it seems to me the way to do it is to have them in groups.  The Earth and Moon orbit each other around their common center of gravity--there's no reason they shouldn't be about the same size.  A third planet could orbit their common CG at a greater distance.   A bunch of such groups could be placed in such groups around the Sun, all in the same circular orbit...We'd probably use the same orbit that Earth-that-was is in.  If the mass of each is about the same, it'll be billions of years before they collide with each other.

Going to the Moon

The last man to have stood on the Moon, Gene Cernan, died today at 82.  Our goals as a nation, as a species, seem to have changed since he climbed back onto the lunar lander in 1972.

When I was a kid, the plan was to launch ever increasing explorations into space--first low earth orbit, then the moon, then perhaps permanent manned space stations, ultimately to include Mars and other planets, along with the asteroid belt.  It was presumed that we'd have hundreds or even thousands of people permanently in space by the start of the 21st century.  Just look at the vision of the great movie 2001: A Space Odyssey.

That didn't happen.  It turns out that the space program was largely a byproduct of the military's quest for ever more powerful weapons.  The boosters used to put men into orbit in the Mercury and Gemini program were re-purposed ICBMs and the vast majority of things actually put into for the first 30 years or so of space flight were spy-in-the-sky stuff, like the KeyHole orbiting cameras.  Even the first planned space station, the Manned Orbiting Laboratory, was really a spy satellite and when robots fulfilled the things capabilities, it was cancelled.

But there are commercial purposes to space.  Weather and communications satellites are extremely valuable.  There is science that can be done better in space than on the ground--the space telescope and robot missions to other planets are illustrations.  There is enormous mineral wealth up there too.  It's much easier to get stuff from space, even from the asteroid belt, onto the earth than it is to get stuff up there.  It's easier yet to use it up there.  The time will come, I believe that a large fraction of our satellites will actually be built in space.  Nearly everything we need is there--but not the people to do the work.

Robots do a lot of things well, but they need a guiding hand.  And that hand cannot be more than a tiny fraction of a light-second away, lest the latency overwhelm the control.  The only way to build a satellite in space is for at least some of the workers to be up there.  This means permanent occupation.  I think the way to do it either to do a rotating ring style space station, or even an O'Neill cylinder.  They are impractical much smaller than about 1000 foot diameter (where 1.2 RPM would give 1/4rd G).   A cylinder 1000 feet in diameter and 100 feet long would have 31,400 square feet of bottom floor space, and would probably be built 10 floors deep or so which probably means a population of a hundred or so.   That's a big thing.

The moon is almost as good and has some advantages. The moon's gravity well is 1/6th what the earth's is, which means it takes a lot less energy and fuel than getting off of earth.  Unfortunately, there's no atmosphere to slow landings, so landing takes just as much energy as taking off.  But as SpaceX has been demonstrating, computers are getting pretty good at this.   Most of the people will need to live underground, to protect them from radiation, but there's no shortage of material.  The biggest problem is water.  But there's lots of oxygen, lots of silicon with which to make solar panels, lots of metals, etc.   The weakest link is hydrogen, which may be available in the minerals, but may be difficult to extract.   And there are so many advantages to building satellites on the moon that it's hard to imagine we won't eventually do that.

We can also build gigantic space telescopes and radio telescopes, completely free from atmospheric and radio interference, by simply building them on the far side of the moon.   Who knows what else?

Life on Other Planets?

Is there life on other planets?  Of course there is.  There are 100 billion stars in this galaxy and it looks like the majority of them have planets.   There are at least 100 billion galaxies in the universe.  that's 10,000,000,000,000,000,000,000 (10 septillion) stars with planets.  most of them will not be inhabited, but even if only one in a trillion is inhabited, that's 10 billion planets with life.  I'm confident will be far higher than that.

The circumstances that allow life as we understand it are fairly narrow: 

• the ambient temperature needs to stay fairly close to the melting point of water: a little above it and not too far below it.  too hot and too much of the water will be vapor.
• the ambient temperature can't vary too much.
• enough gravity that most of the water will stay liquid.
• not so much gravity that complex molecules break down.
• enough solar energy to provide a source of energy
• not so much solar that complex molecules will break down
• enough radiation to generate some mutation.
• not so much that a species can't be stable long enough to reproduce widely.
• has another big planet in the same system that cleans out most of the asteroids
• has a relatively circular orbit (to keep temperature constant)

the only specific chemistry that this requires is water.  Our life is based on carbon and water, but silicon or potentially any other chemistry is conceivable.


So far, there is only one planet that we know meets all these criteria, and it's the one we live on. About 3000 exoplanets have been detected so far and only one of them doesn't have obvious disqualifying factors.  The Kepler spacecraft is looking at 145,000 stars and has only detected planets on a few thousand of them.  The mechanism used wouldn't detect a system with one of the poles pointed at us--around half of the stars examined--and virtually all qualifying planets are below the minimum size that can be detected with Kepler. 


Of course, it may not be necessary for the physics we're familiar with to be relevant at all:

They're Made Out of Meat
A Fire Upon the Deep


The Drake equation: calculates the number of extraterrestrial civilizations that might be able to generate signals that we can detect.   Most of the parameters are unknown.

R_* is the rate of star creation (known)
f_p is the fraction of stars that have planets (still unknown but appears to substantial)
n_e is the number of planets per such star that could contain life (still unknown, but in our system, if we count all moons and planets, it's about 2%)
f_l is the fraction that actually go on to develop life (totally unknown)
f_i is the fraction that develop intelligent life (totally unknown)
f_c is the fraction that release detectable signals into space. (totally unknown)
L is the average length that such civilizations are able to communicate (totally unknown)

he omitted one: fraction that are close enough that any signal might be detected.   It's hard to imagine this coming from anywhere outside of our galaxy and probably only the local quarter.


The first four terms address the same question I'm asking.  The only one that's still completely unknown is f_l, the fraction of planets or moons that actually develop life.  The earliest fossil record found so far of life on earth is about 3.5 Billion years ago.  The first time life as we know it could possibly have formed--the first time that liquid water was available on earth--was about 4.4 Billion years ago.   So we know life started at some time in the first 900m years that it was possible.  There's not much left of the fossil record from that long ago, so it's probable that it was a lot longer than 3.5B year ago.

Life tooled along making stromatolites and other primative things, until about 1.2B years ago, some protozoa figured out how to reproduce sexually.  This created lots of new things: species that would breed true, yet allowed a lot of very small variation, to allow evolution by natural selection to take place.  It took another 650m years for the real excitement to happen, in what's called the Cambrian Explosion, when all of the multicellular phyla of plants and animals evolved. 

So we took at least 3 Billion years to develop above the protazoa stage (and most of that to develop to the protazoa stage), and more than another half billion years to develop intelligence.  if this is typical, chances are pretty good that whatever life we find will be very, very simple.  We know that over 3/4ths of the time that life has been possible on earth, that it has existed.  It is entirely possible that the first life occurred in the first few million years, or even earlier. As it stands, it seems like that 3/4ths is a plausible guess for f_l.

So far, we have only sent missions capable of detecting life to one of the extraterrestrial bodies in our planet where life would be at all possible, Mars, and we know that it's unlikely there because atmospheric pressure is too low to sustain liquid water and temperature too high to allow a permanent frozen shell.   There are a handful of moons that probably do have liquid water, around Jupiter and Saturn, although in all cases, it's under a very thick layer of ice.   Until we find out whether there is life there, we really have no handle on that all important term: f_l.  But we have the beginnings of a handle on some of the others.  Life on about 1 in 200 planets seems possible based on what we know.  And since most stars that have any planets probably have multiple planets, the number of stars with life is probably similar.

Secession

A Texas man fired on police Monday and declared that he was a sovereign citizen and had seceded from the United States, calling his sovereign state "Doug-i-stan."  Much of human advancement and exploration has been driven by this instinct, from the first humans to leave east Africa a million years ago to the colonization of the New World and Australia just a few centuries ago.  Doug is a crazy, but it's a type of crazy that is a major part of the human condition.

In the 1600s, crossing the Atlantic to come to America required a substantial investment...you had to buy space on a ship and convince that ship to cross a very dangerous ocean and go to a place that that was almost completely unexplored and was known to have large numbers of dangerous, inscrutable people living there.  But a lot of people took the challenge.  A lot of them sold themselves into a type of temporary slavery called "indentured service" to pay the fare.  Many did not like the situation they were in: oppressive local leaders trying to take their profits or force them to behave or believe in ways they didn't like...But the realization that freedom could be obtained by simply moving into the next valley, or later on, to the next territory.  It was harder and more dangerous than staying put but you had a better chance of controlling your own life.

As long as there was open, arable land available, these adventurous souls could try out whatever lifestyle they pleased, and the homestead act of 1862 made even more available.  Violence, against natives, thieves, encroachment from other groups, animals, was commonplace and often necessary for survival, so guns, while terribly expensive, became an important part of many of these little cultures.  Going out into the "back 40" to practice or hunt was not just a right, it was often necessary.   But homesteading was far cheaper, and far more practical for the poor farm families of the 1870s than it was at any time before or since.

But today there is no more open land.  Many of the descendants of the homesteaders lost their farms in the dust bowl and depression, but a lot are still there and still have the craving to be able to hunt on their own, to be able to graze on land that doesn't seem to be occupied at the moment (or steal it even if it is), to express themselves in whatever way comes to them.    The homestead act had required that homesteaders not have been in rebellion to get the land; it had been a way to draw many potential confederate soldiers away from battle; but many of them were inclined to support the "states rights" cause even though they were far too poor to have owned slaves, and many of our rural areas still have this inclination very strongly.  They haven't quite internalized the fact that not only is the homestead act over, the possibility of such a thing is over and trying to act in ways that were appropriate in the 1860s through'80s is just not possible in today's society.

In many ways this is regrettable.  The homesteads of the future will be on the Moon, on Mars, perhaps on asteroids or O'Neill cylinders, or even on planets around undiscovered stars.   It will take a much larger investment--of talent, of training, of treasure--to achieve these, and there won't be many openings for non-wealthy, poorly educated, but determined and hard working farmers.  The craving to do whatever you please, even at the risk your own survival, is strong in the human race.  But there is no space left for "sovereign citizens" like Doug, and if they shoot at people, they must be dealt with as criminals.  I'd like to leave the Dougs and the Cliven Bundy's of the world alone, to find out just exactly how hard it is to live a truly "sovereign" life, but unfortunately they are our neighbors and we need to keep our other neighbors safe.

Centrifugal Spaceships

Back when we still thought we were going to spend the next 50 years exploring space, one of the popular ideas was to implement artificial gravity by putting passengers and crew into a big centrifuge.  Wernher von Braun, Chesley Bonestell, Arthur C Clarke and many others included giant, rotating space stations as part of their imagery.   These guys understood that lack of gravity was a real problem and thought dealing with that was critically important.  As real experience with humans in space as been accumulated, the consequences of "microgravity" have been recognized to be even more serious than they'd feared, leading to bone loss and other problems.  So why is it that we haven't built spinning space stations?

The reason is that there turned out to be lots of other problems that were equally, or maybe even more serious.  Simply getting stuff up there has proven incredibly challenging, and the economics have worked out that many, small, unmanned satellites provide a much better return than putting humans up there.  Secondly, the reality turned out to be that the political advantage gained by the space race was fairly limited to "beating the Russians".  Once that was accomplished, there was really very little popular support for the space race.  So there was little support for big ideas like the space station in the image above (by Bonestell), which inspired Arthur C Clarke and Stanley Kubrick in their movie 2001: a Space Odyssey.  The space station we've actually got, 12 years after 2001, has a pressurized volume of 29,600 cubic feet--about what 3700 square feet of building have.  Much of this is filled with equipment, so the living space is really no more than that of a moderate family house.

If all that space were organized into a ring like the one above-12 feet wide by 8 feet high, the ring would be a mere 64 feet in diameter.  To spin it fast enough to make a 1/6th G (lunar gravity) would take 7RPM, or fast enough to make 1 G, it would take 17RPMs.  Ridiculously fast, and not really practical if you're trying to take a look outside or dock a spaceship.  To get it down to the stately speeds we saw in "2001", it would have to be a half mile or more in diameter.  At that size, lunar gravity can be simulated with just one RPM.  The centrifuge inside the "Discovery" spaceship, where we first met movie astronaut Frank Poole jogging, was about 50 feet in diameter, so it would have to spin even faster.  I'm sure for really long trips, like the one they're on in the movie, space ships would have to contain such centrifuges.   I think that's about the smallest practical human centrifuge though.    Eventually, we'll have big, kilometer diameter or bigger space stations, and I have great hope for O'Neill Cylinders some day in the future.  But not for a while yet.

Going Halfway

Someone¹ once said "There is nothing so useless as half of a bridge.  You've wasted resources that could have been used on something useful, and you still can't get across the river."  There are a lot of things which are like bridges, and are worse than useless if you don't finish them.  But there are a lot of things that are worth starting even if you can't finish.  If you're starving, it's worth eating a little, even if you can't afford a full meal.  Likewise, if you've got a federal deficit, raising taxes on rich people will reduce the political pressure to resolve the problem and not hurt the economy in any way that is borne out by economic history, even though it won't completely solve the problem.

There are lots of cases where going halfway is a lot worse than finishing the job.  The space shuttle was conceived as a much bigger project, with more, larger vehicles.  Cost cutting reduced the efficiency of the ultimate design to the point that the total cost of the program was 450% (correcting for inflation) of the predicted cost of the more ambitious program delivering less than 10% of the projected payload to space.  Most experienced engineers have been involved in projects where cutbacks intended to reduce development time or costs had the effect of increasing them--while damaging the product more than could possibly be made up by reduced costs².

When deciding to cut back a project, be it a small engineering project or a national health care system, it's important to try to decide if you're saving money or producing half of a bridge.  The evidence is pretty overwhelming--single payer healthcare, such as US medicare or the British national health, is far cheaper and produces better outcomes than piecemeal "market based" systems.  People must have adequate health care.  Cutbacks to medicare and medicaid will either make healthcare more expensive, or kill thousands.

¹ I think this may have been the military strategist Karl von Clausewitz, but I haven't been able to find the reference.
² My own experience with this was Microsoft C6.  We'd planned an 18 month development cycle, but about 4 months in, this was shortened to 6 months.  Three years later, we finally shipped a vastly inferior product to the one we'd have built on the original schedule, at perhaps triple the cost, to great loss of market share and prestige, and provoking most of the technical talent to leave the team.

Steam Engines in Space

Much current power generation is done with steam.  Water is confined in a "boiler" and exposed to some heat source (burning coal, nuclear fission, concentrated solar energy, etc.) and boiled.  This produces steam, which is passed through a pipe to a turbine or reciprocating piston(s) to produce rotary motion.  Usually this is used to power a generator, but sometimes the rotary motion is used directly--a steam locomotive for example.

An important but subtle component of a steam locomotive is what's called the "steam dome".  This is a dome on top of the boiler, where the steam collects.  It relies on gravity--water stays in the boiler, while the "dry" steam floats on top and in the dome.  It's important to keep water out of the steam tubes and pistons: it cools the steam, reducing pressure, and if there's enough of it, can prevent the piston from moving and break something.

As far as I can tell, conventional steam locomotives need gravity or something like it (e.g. centrifugal force) to operate.  There are heat engines which do not require this separation of dry steam, such as the Stirling Cycle, so it's still possible to produce rotary power in space.  It's also possible to make a direct ejection steam rocket which could operate in zero-g.

Going to the Moon

Neil Armstrong and Buzz Aldrin walked on the moon 43 years ago this year.   Three years later, we packed it in and switched over to providing bus service to low earth orbit.   The vision provided by one of the great movies of the time, 2001: A Space Odyssey, suggested that 11 years ago, we'd have space stations that were big enough to require bus service and populated enough to justify artificial gravity by rotating them, and at least two permanent bases on the moon.  The cold war was still going full force.

Last week, Newt Gingrich proposed a permanently manned base on the moon by "the end of his second term", which in his delusional grandeur would occur in 2021.   Newt doesn't understand this, but this is a very Keynesian idea, and could well be the most sane thing he has said during his entire campaign.  The space program used to be a great impetus for innovation and new technologies.  The computer, microelectronics in general, networking, numerous material, chemical, and other new industries were created by the space program.  Most of these things would likely have happened eventually anyway, but the confidence that there would be a lucrative business providing these things accelerated all these industries by many years.  It cost $23.9B (about $170B today) over about 15 years, and created over 350,000 direct jobs.  Most of these didn't last the full life of the program, but lets say it was about half--that's $50 or $60K per job in current dollars.  And that's only direct jobs.  It doesn't count the new industries it created or expanded.   A business is much more inclined to open a new production line if it knows that (say) half its production will be bought by the government.  Then there are also the people providing lunch and housing for the workers. How many job/years did Apollo create indirectly? tens of millions? compare this to the piddly 12000 job/years created by the $7B Keystone XL (about $500K/job).

Space exploration is best done by robots.  They're much more tolerant of radiation, they don't have health problems related to low gravity and boredom, they allow larger teams to participate over dramatically longer time periods.  Unfortunately, they do have long time delays, so it really helps to have a human close up.  For this reason, we really do need to have colonies over the long term.  There are lots of potentially useful things we can "harvest" from space.  Pure exploration is the most obvious and probably the most valuable over the long term, but there are lots of shorter-term wins.  For example, there are a bunch of production processes that can only be done in a vacuum or zero gravity.  This is difficult or impossible to achieve on earth.  There are minerals in the asteroid belt that can be enormously valuable here on earth. They may be even more valuable in space--if we learn to mine them, we don't need to lift them off the earth, which will make the colonies cheaper.   Radio takes an hour or more to get to the asteroids, so we need to send a few humans with our mining robots.  This will be way cheaper if they live in a space station or on the moon.

The real point of space exploration is the creation of new things, things we could have never imagined had we not tried to do it.   Would the iPhone have happened without the space program?  Maybe, but probably not for another 10 years or so.

Olbers' Paradox

I just read the wikipedia article on Olbers' Paradox.  What a bunch of nonsense!

The paradox goes like this:   The night sky appears dark.  Yet when we use magnification to look at any dark area of the sky, it's all full of stars, with dark areas between.  When we use even more magnification to look at those dark areas, there are even more stars in there.  The statement is then that if we look at the sky at any angle, we'll eventually run into a star.  So if there are so many stars, why is it that the sky appears dark and not bright?  So then the article goes on to blather about the cosmic background radiation and this being proof for the big bang, and a bunch of other silly explanations.  

Olbers' Paradox is one of those things that is only a paradox if you don't quite get the concepts of infinitesimal and relativeness.  Darkness is a relative thing.  The space between stars is dark because we can't see anything there.  Because our eyes (or whatever tool we're using) aren't capable of getting enough photons to trigger a sensor, we record it as dark.  That's really the end of the necessary explanation.  If we use a more powerful sensor, the threshold changes along with the shrinking field of view, but there's still a minimum.  We would still perceive this as a dark sky even if the universe was actually infinite.  A star that's too far for whatever sensor we're using would be registered as dark, even if it's actually shining bright.

Zeno's Paradox is another of the same sort of thing.  In it, in order to get from A to B, you must first travel halfway.  In order to get from A to halfway, you must first get to half halfway.  And so on.  So if there's an infinite regression of these halfways, then how can we ever get anywhere?  Again, the answer is simply that when you split the distance, you also split the time it takes to get there.  You can always split time and distance farther.  As long as you split them at the same rate, there is no paradox.

(Actually, there is a limit to this sort of splitting, caused by quantum effects.  This impacts our sensors at a much larger scale than it impacts reality.  It's interesting, but not in any way relevant to either paradox)