Where Humans Can go in the Solar System

September 29th, 2014
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In recent years there has been much discussion about human space exploration venturing beyond the earth-moon system to take on Mars and possibly other planets.  In light of this, I decided to do a little research to determine exactly what celestial bodies are suitable for human exploration.  Certainly, humans can fly by most any part of the solar system, should they have an advanced enough spacecraft.  But there are a limited number of places where surface exploration is possible.  What qualifies these places is the ability to survive in any current or foreseeable space suite or any kind of reasonable habitation module.

Since we are far from having any kind of faster than light travel (which, if possible at all, requires warping space or using some kind of artificial wormhole) and we are not ready for multi-generational spacecraft, the solar system is pretty much what we are stuck with.

It seems the places we can actually send humans are pretty limited.  There is definitely Mars, but after that, what comes next?   Possibly some of the moons of Jupiter, assuming its worth our while to send humans there in the future.   Mars appears to be the best candidate for any kind of permanent or semi-permanent colonization or station.

Places humans could visit with reasonable habitat modules and/or spacesuits:

Mercury - Possibly on the side that faces away from the sun, but it’s questionable whether it would be worth visiting.

Venus - The temperature and pressure on the surface are far too high for a spacesuit.  Manned flybys, however, have been considered in the past.

Earth’s Moon - Yes, obviously, since it has been done.  The environment is certainly harsh, but well within the capabilities of a spacesuit.

Ceres - A dwarf planet that is the largest member of the asteroid belt.  It could be visited by humans in spacesuits for surface study, but it is so small that it would be possible to jump off it into space.  The gravity is not sufficient to allow walking around on it.  Therefore, it would be more like clinging to the surface and floating around it than it would be “landing” on it in the normal sense.

Other asteroids - Again, lack of gravity makes surface exploration in the sense of walking impossible.  It’s possible human exploration of an asteroid would be worthwhile.  Some asteroids may have orbits that make them easier to get to than mars or other planets.  The scientific value of this may be questionable.  An asteroid does not seem like a good place to position any kind of manned outpost or colony.

Mars - The environment on mars is certainly within the capabilities of a spacesuit.  The gravity is more than sufficient for relatively normal movement.  Mars is also close enough to earth to make a trip to and from Mars practical for a crew.  This is probably the best place for exploration beyond the earth-moon system, although asteroids have been suggested as well.

Phobos - The largest moon of mars, but still much smaller than our own moon and more similar to Ceres in size.  There is no atmosphere and it should be within the capabilities of spacesuits, but again, hard to really walk around on because of the small size and lack of strong gravity.  It has the advantage of being easier to take off from than the surface of mars, due to such little gravity.

Jupiter - No.  The gas giants are out of the question.  Not only is it a massive ball of gas, with nothing to stand on, but the pressure is far too high for survival, not to mention the crushing gravity.  Probes that visited the area around Jupiter discovered that it has powerful radiation belts, which could be a problem for even a manned flyby.

 Io (Moon of Jupiter) - Quite possible.  It is only slightly larger than our own moon, so it has a fair amount of gravity.  Radiation might or might not be an issue.  The distance from the sun would make it very cold, necessitating heated space suits.

Europe (Moon of Jupiter) - Also possible.  Good size, but the surface characteristics are less well known.  It is believed to be covered with either ice or a cold brittle rock.  The surface therefore may or may not be suitable for exploration.  Again, radiation and cold are issues.

Ganymede (Moon of Jupiter) - Similar to Io, but larger and thus more gravity on the surface, but still much smaller than earth.  Possible, but cold and radiation are concerns.

Callisto - Possible, rocky moon similar to Io and Ganymede

Saturn - No.  Again, as with Jupiter, the gas giant has massive gravity and no place to stand.

Titan (moon of Saturn) - It’s hard to say but it might be possible.  It’s larger than our own moon.  It has its own dense atmosphere, which is unusual for a moon.  It would be very cold and harsh, but maybe within the capabilities of future space suits and habitats.   With Saturn and its moons, the distance of the travel and thus the time exposed to cosmic radiation and weightlessness become an issue, although this could be overcome with a powerful enough rocket, such as a nuclear pulsed propulsion system.

Other moons of Saturn - Saturn has dozens of moons, with Titan being the largest.  Most of the moons are small and unappealing for manned exploration.

Uranus - No. It is a gas giant, though smaller than Jupiter and Saturn.

Moons of Uranus - Some might be possible, but the extreme distance becomes a concern.  None appear especially appealing.

Neptune – As with the others, no landing on this gas giant.

Moons of Neptune - Only one moon is of substantial size, Triton.  It might be possible, but cold, distance and radiation are issues.

Pluto and Satellites - Though no longer considered a planet, it could be a target worth investigating.  Probably not worth human exploration.  Not only is it far enough from the sun to be super cold, but the distance would necessitate many years in transit to and from it.   The same is true with other Kuiper belt objects.


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34 Responses to “Where Humans Can go in the Solar System”

  1. 1
    Robert Sneddon Says:

    Mercury has a solar “day”, it is not tidelocked facing the Sun but it is forced by gravity into a lockstep rotation of once every two Solar years. From the wiki pages about Mercury:

    Mercury is gravitationally locked and rotates in a way that is unique in the Solar System. As seen relative to the fixed stars, it rotates exactly three times for every two revolutions it makes around its orbit. As seen from the Sun, in a frame of reference that rotates with the orbital motion, it appears to rotate only once every two Mercurian years. An observer on Mercury would therefore see only one day every two years.


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  2. 2
    DV82XL Says:

    While I understand the appeal of manned missions, the fact remains that the harsh conditions mean that keep personnel both safe and functional (and the need to return them intact) will always make these far more expensive, and far riskier than robotic missions, and if the reason for mounting these things in the first place is science, more is likely to be accomplished. Automatic probes themselves are getting more autonomous, more sophisticated and last far longer than they used to, and one can see the day coming where any advantage of having a person on the spot will be marginal at best. However having said that, the limitations of the speed of light will always be an issue anywhere past the orbits of Mars and Venus and some argument could be made for humans in orbiting ships controlling remote-presence robots on some nasty surface.


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  3. 3
    Anon Says:

    Radiation is very definitely an issue with Io and Europa (36 Sv/day at Io and 5.4 Sv/day at Europa).

    Venus is actually quite earth like at high altitude and breathable air is a lifting gas so gigantic airships might be able to work there (but your earlier post on heavy lift airships). For Mercury it’d the poles you’d want to build a base at, assuming you want a base there at all (and it is surprising that you’d think it has a dark side).

    Oh and beware of planetary chauvinism, we’re probably better off just building rotating space stations from asteroidal resources.

    Someday we’ll probably want to mine the gas giants for fusion fuel, that would tend to give us a good reason to go there and in the even longer term we could even move to the stars simply by moving from Oort cloud object to Oort cloud object and gradually diffuse our way to another star (people out there aren’t going to care about the sun).


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  4. 4
    BMS Says:

    “we are not ready for mulch-generational spacecraft …”

    I’m willing to bet that some gardeners are. ;-) But how to get that much mulch back down to earth remains a significant technical challenge.


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  5. 5
    Glenn Scott Says:

    I am very skeptical that humans will live extraterrestrially in any great numbers. The environments of the rest of the Solar System; bodies or space, is suited for robots tailored to handle the characteristics of that particular extraterrestrial environment. Earth belongs to humans; the rest of the Solar System will belong to our robotic progenies. Mining the Moon or the asteroids: The best reason to do so is for metals and fuel above Earth’s gravity well. And the best reason to do this is for large cislunar solar power systems, maybe … or to feed the self-replicating ‘bots.

    Consider this, we have a 1G, low radiation, oxygen rich, water rich, life supporting planet right under our feet. Why build a colony on Mars when you have empty Wyoming? After that you have ocean surfaces, deserts, ice sheets … Baffin Island … to go live on – all of which are much nicer than Mars or the Moon or Ceres or some orbiting Tin Can. If you want to get tougher than that, try ocean floors, sub ice, or subterranean. Any robotics, nanos, AI, self-replicating tech conceived to make possible the exploitation of the Solar System will also get used right here on Earth. Go ahead and invest in an asteroid mining company like Planetary Resources (well, that is if you were uber-rich and groovy enough to get offered shares). I’ll put my money on companies focusing this same tech on Earth.


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  6. 6
    drbuzz0 Says:

            BMS said:

    “we are not ready for mulch-generational spacecraft …”

    I’m willing to bet that some gardeners are. ;-) But how to get that much mulch back down to earth remains a significant technical challenge.

    corrected


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  7. 7
    Anon Says:

            Glenn Scott said:

    Consider this, we have a 1G, low radiation, oxygen rich, water rich, life supporting

    All of which rotating space stations can provide us.

            Glenn Scott said:

    planet right under our feet.

    But with extremely inconvenient access to freefall conditions.

            Glenn Scott said:

    Why build a colony on Mars when you have empty Wyoming? After that you have ocean surfaces, deserts, ice sheets … Baffin Island … to go live on – all of which are much nicer than Mars or the Moon or Ceres or some orbiting Tin Can.

    We could make an orbiting tin can surprisingly nice, much nicer than the middle of a desert.

            Glenn Scott said:

    Any robotics, nanos, AI, self-replicating tech conceived to make possible the exploitation of the Solar System will also get used right here on Earth.

    Maybe, or maybe they won’t as Earth would have less need for them (or more regulations against them).

            Glenn Scott said:

    Go ahead and invest in an asteroid mining company like Planetary Resources (well, that is if you were uber-rich and groovy enough to get offered shares). I’ll put my money on companies focusing this same tech on Earth.

    Companies focusing that tech on Earth aren’t going to be selling large amounts of Platnium to Earthlings.


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  8. 8
    Glenn Scott Says:

    Gravity is free on Earth, it is massively expensive in LEO or elsewhere via rotating structures. ‘Bots don;t need gravity, their homes won’t rotate.

    Inconvenient access to 0G/Freefall conditions is not a sufficient condition to necessitate humans in space in large numbers.

    The desaerts are awesomely beautiful. You can have your Tin Can, I’ll take Moab.

    Libertarianism is a weak justification for going to space. If we can do lots of stuff in space that would be illegal on Earth – like building thinking machines or self-replicating bots – I suspect we’ll end up either doing them on Earth or making it illegal in space too.

    How much platinum are you going to need to bring back to Earth to create a competitive return on capital? The multi-trillion dollar valuations for verious asteroids assume a fixed price for the precious metals, a rather generous assumption. That said, whatever tech and capital you got drilling into an asteroid and returning to Earth, could be used to mine Earth.


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  9. 9
    DV82XL Says:

    There are legitimate reasons to develop and maintain the capability to deploy people in space, landing them on other planets may not be one of them. As i wrote above, C places limits on direct command and control of robotic missions from Earthside so this might be better accomplished from a ship orbiting these worlds. Asteroid may or may not prove cost effective, the same general capacity would be needed should there be a need to deflect one of these from striking us, and again communication limits may necessitate a hands on approach. Finally, although it may be a long way off, terraforming of some of the planets may eventually be within our technological capability and the final step there would be colonization.


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  10. 10
    Anon Says:

            Glenn Scott said:

    Gravity is free on Earth, it is massively expensive in LEO or elsewhere via rotating structures. ‘Bots don;t need gravity, their homes won’t rotate.

    I doubt building a large rotating space station would really be all that much more expensive than a large space station that doesn’t rotate, in terms of materials radiation shielding is going to be dominant anyway (unless you use active shielding, better hope there isn’t a blackout in the middle of a big flare).

            Glenn Scott said:

    Inconvenient access to 0G/Freefall conditions is not a sufficient condition to necessitate humans in space in large numbers.

    Maybe not, but that never stopped people moving before.

    Besides, is it really wise to have everyone on the one planet?

            Glenn Scott said:

    Libertarianism is a weak justification for going to space.

    I’d actually go further than that and state that a libertarian society is unlikely to work in space (maybe left-libertarianism could work, but US style, the free market is always right no matter what is likely to be a recipe for disaster).

            Glenn Scott said:

    If we can do lots of stuff in space that would be illegal on Earth – like building thinking machines or self-replicating bots – I suspect we’ll end up either doing them on Earth or making it illegal in space too.

    Enforcement of those rules could be much harder against a space based group especially once we get to self-sufficiency.

            Glenn Scott said:

    How much platinum are you going to need to bring back to Earth to create a competitive return on capital?

    Depends on what it costs to mine.

            Glenn Scott said:

    The multi-trillion dollar valuations for verious asteroids assume a fixed price for the precious metals, a rather generous assumption.

    Even once the market corrects it’ll still be a pretty decent amount.

            Glenn Scott said:

    That said, whatever tech and capital you got drilling into an asteroid and returning to Earth, could be used to mine Earth.

    Doubtful, a lot of the technology will be based on the assumption that there’s almost no gravity and abundant high intensity sunlight which can be concentrated by kilometre size extremely light mirrors (that could never exist on Earth).

    There’s also the fact that you simply won’t find a mine on Earth with anywhere near the concentration of an asteroid.


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  11. 11
    Matte Says:

    Well, a Duna mission is feasible but I’d rather go for Dres. No pesky atmosphere and lower gravity than the Mun…

    Nerdy parables aside. The only resource worth mining from asteroids would probably be iridium, platinum, tantalum and uranium/thorium. Assuming they are found in high enough concentrations. I have a very hard time justifying the expense and technical dificulties of going after anything else…


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  12. 12
    Anon Says:

            Matte said:

    Nerdy parables aside. The only resource worth mining from asteroids would probably be iridium, platinum, tantalum and uranium/thorium. Assuming they are found in high enough concentrations. I have a very hard time justifying the expense and technical dificulties of going after anything else…

    U and Th will probably be in very low concentrations, at least in most asteroids (going by concentration in meteorites).

    For stuff to be used in space you may as well get it from asteroids (or the moon) rather than blast it up out of a gravity well but it’s unlikely that there’ll be much selling of anything outside the Pt group to Earth and if you can get the Pt group metals you can also get a lot of Iron and Nickel (maybe even some volatiles while you’re at it).


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  13. 13
    Robert Sneddon Says:

            Matte said:

    Nerdy parables aside. The only resource worth mining from asteroids would probably be iridium, platinum, tantalum and uranium/thorium. Assuming they are found in high enough concentrations. I have a very hard time justifying the expense and technical difficulties of going after anything else…

    Uranium’s cheap as chips at the moment and for the foreseeable future. Spot market price for yellowcake is (using your quaint and archaic 18th century US form of measurements) $35.65 per pound. Japanese researchers have proven the tech to extract it from seawater using mats of ion exchange resins and claim the price would be about $135 per pound in mass production. As for thorium there’s piles of it sitting at mineheads today unwanted and unloved and the Powerpoint Warriors pushing molten-salt thorium breeders insist is is common enough and cheap enough to meet the demand of centuries of intense consumption without having to go into space to find more.


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  14. 14
    Shafe Says:

            Robert Sneddon said:

    (using your quaint and archaic 18th century US form of measurements)

    I find it hilarious that people get their feelings so hurt over the US public’s refusal to metricize, that they feel compelled to make snarky comments about it, even though no mention of US customary units had been made, and even though the person they’re sniping at is a Swede who uses SI units. (Time to let it go?)


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  15. 15
    drbuzz0 Says:

    It’s actually common practice to use non-standard measurements for various commodities. Precious metals are priced in troy ounces. Oil in barrels, which are 42 imperial gallons. Some agricultural products are priced in bushels. Short tons is still used for many things. Some things are even priced by hundredweight.

    This happens even in countries that have fully embraced the metric system. It’s a holdover to the traditional units for such things.


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  16. 16
    DV82XL Says:

    Beyond the fact that it is in widespread use there is little to commend SI as a system of measurement. Other than its use of base ten throughout, there is nothing particularly intuitive about the scale of the individual units and in fact most of them cannot be used for everyday measuring without invoking multiples and submultiples that themselves are not human-scale. And human-scale is exactly where they are weakest, very small and very large amounts are not that bad, but in things like groceries, carpentry, sewing and such any advantage of metric is marginal indeed.


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  17. 17
    BMS Says:

            DV82XL said:

    Other than its use of base ten throughout, …

    I completely agree with this comment and will add that this consistent use of base ten makes this system of units less compatible with fractions. Having 12 inches in a foot means that it is trivial to divide a foot into 2, 3, 4, and 6 pieces. There are similar benefits to be had from clocks using numbers based on 12 to measure time, which is something that metric hasn’t changed. Nobody talks in kiloseconds instead of hours.

    But the human-scale point cannot be over emphasized.

    For scientific and engineering work, SI does get some things right over the alternative. For example, there is no one definition of BTU (British thermal unit), because it depends on what type of calorie is used, whereas the watt is well defined. The differences are small, but I’ve seen them cause some confusion.


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  18. 18
    BMS Says:

    Sorry, I meant the joule is well defined. I should be talking about compatible units.


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  19. 19
    DV82XL Says:

            BMS said:

    Having 12 inches in a foot means that it is trivial to divide a foot into 2, 3, 4, and 6 pieces.

    One of the minor tragedies is that base-12 lost out to base-10 as the standard for counting. There is no chance of changing this now of course, but it is just too bad.


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  20. 20
    Anon Says:

            DV82XL said:

    Beyond the fact that it is in widespread use there is little to commend SI as a system of measurement.

    You mean other than the fact that it is a system and not a hodgepodge of different measures chucked together seemingly at random and with no thought as to how they fit together? That it doesn’t needlessly have multiple different units for the same thing?

            DV82XL said:

    Other than its use of base ten throughout, there is nothing particularly intuitive about the scale of the individual units and in fact most of them cannot be used for everyday measuring without invoking multiples and submultiples that themselves are not human-scale.

    The problem with designing a measurement system to have a human scale is that when you do that you end up with lots of units that don’t make sense (and is a foot really the size of a foot or is a lot bigger than any but a few real feet?).

            DV82XL said:

    And human-scale is exactly where they are weakest,

    Or did you grow up with the old measurements? I strongly suspect that the arguments against metric is just old fashioned conservatism.

            DV82XL said:

    very small and very large amounts are not that bad, but in things like groceries, carpentry, sewing and such any advantage of metric is marginal indeed.

    Yes, I’m sure 4 and 15/16th of an inch is easier than 125 mm.

    The small size of the millimetre means it’s about the smallest human scale measurement you can get so can be used for pretty much all human scale things without any resort to fractions.

            BMS said:

    I completely agree with this comment and will add that this consistent use of base ten makes this system of units less compatible with fractions.

    True to a point but is there another system of units which uses a different base and not some hodgepodge of different bases? I can’t think of one.

    Using the same base as our numbering system does itself have some massive advantages, namely that you can remove or add a prefix merely by moving a decimal point, for dividing a larger unit like the kilometre up into sub units it’s hard to beat.

            BMS said:

    Having 12 inches in a foot means that it is trivial to divide a foot into 2, 3, 4, and 6 pieces.

    While a metre can be divided into 250 mm easily enough, thirds are harder of course but 333 mm is usually close enough. You’ll have repeating fraction problems no matter what base you choose.

            BMS said:

    There are similar benefits to be had from clocks using numbers based on 12 to measure time, which is something that metric hasn’t changed. Nobody talks in kiloseconds instead of hours.

    Time is difficult as you have to match the natural variations over a day and year but I suspect that base 10 would work well enough for that but to truly get the full benefit from metric time you’d probably need complete control over the seasons so you can indeed have a year be a base^power multiple of a day, maybe someone will try it in a space habitat someday (actually I’d be surprised if it never gets tried).

    There was also the fact that the people who created the French revolutionary calender screwed it up by making it too dependant on France (while the metric system they also created at the same time was designed to be truly international from the beginning). Also if you change the length of the week make sure you keep the same proportion of rest days.

            BMS said:

    But the human-scale point cannot be over emphasized.

    Even bringing it up is overemphasising it.


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  21. 21
    Anon Says:

            DV82XL said:

    One of the minor tragedies is that base-12 lost out to base-10 as the standard for counting. There is no chance of changing this now of course, but it is just too bad.

    Nowadays we’d probably be better off with base 16 for commonality with our computers, even if we miss out on terminating 3 fractions.


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  22. 22
    DV82XL Says:

            Anon said:

    True to a point but is there another system of units which uses a different base and not some hodgepodge of different bases? I can’t think of one..

    And your point is? What huge advantage is there in having a single base in this regard? Inasmuch as metrification had to be shoved down the throats by legislation in those countries previously using the Imperial system there didn’t seem to be a burning desire for that particular aspect of the reform. On top of which, the one major advantage of swift calculation is somewhat moot given the almost universal use of calculators.

    This is not to say SI is useless, as BMS accurately stated, it is ideal for science and engineering, it’s just not all that intuitive for everyday use, which is why it faces continued resistance in the US and why it is still used informally in officially metrified countries. even among those raised and educated in metric.

            Anon said:

    Even bringing it up is overemphasising it.

    Nonsense. In the end these are just tools, and utility of a tool, rather than some abstract aesthetic factors are always going to take precedent. On top of which, guaranteed that if a novel system of measurement were being designed from scratch today. human-scale factors would be a major design requirement.


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  23. 23
    BMS Says:

            Anon said:

    You mean other than the fact that it is a system and not a hodgepodge of different measures chucked together seemingly at random and with no thought as to how they fit together? That it doesn’t needlessly have multiple different units for the same thing?

    Well, there are those who think that it’s best to use the right tool for the job, and then there are those who are so fixated on hammers that they think that everything should be a nail.

            Anon said:

    The problem with designing a measurement system to have a human scale is that when you do that you end up with lots of units that don’t make sense (and is a foot really the size of a foot or is a lot bigger than any but a few real feet?).

    And then there are those who take things way too literally.

    But since you’ve brought up the foot, I should mention that I’ve found that I can pace out distances on the ground, in feet, by using my feet (in shoes, of course) to a surprising amount of accuracy, considering the crude, but readily available, tool that I’m using. And I wear what is probably one of the most common sizes of shoes for adult males. I’ve never been able to pace out meters as effectively or accurately.

            Anon said:

    Nowadays we’d probably be better off with base 16 for commonality with our computers, even if we miss out on terminating 3 fractions.

    Why? The whole purpose of having computers is for them to do the calculations, not us. Computers just enable us to combine this “hodgepodge” of units that you complain about far more easily. In most circumstances, the cost of conversion is only one multiplication operation. The convenience of base 12 is that it simplifies doing common fractions in one’s head and it simplifies the result. If a computer is available, the base is irrelevant.


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  24. 24
    DV82XL Says:

    Admittedly any argument about what the common base for everyday counting should be is as sterile as it is moot, however in Pre Roman Europe there were several competing bases used by various cultural groups. The ones that contributed to the development of the English language apparently used base-12, (which is why there are unique words for eleven and twelve) and there are clear vestiges of base-20 in French as seen in numbers like 80 which is quatre-vingts, literally four-twenties (think “four-score”). There is also evidence of the use of other bases among some isolated tribes, however this is rather thin (although elsewhere in the world the record ii clearer)

    Nevertheless it was the rise of Rome and their system of counting that prevailed, yet there is absolutely nothing that commends this base mathematically beyond the number of fingers we have.


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  25. 25
    Anon Says:

            DV82XL said:

    And your point is? What huge advantage is there in having a single base in this regard?

    Having the same base as the numbering system is the big advantage, it means you can convert with simple digit shift operations.

            DV82XL said:

    On top of which, the one major advantage of swift calculation is somewhat moot given the almost universal use of calculators.

    But to use a calculator you need to have a calculator on you, I don’t make a habit of carrying a calculator around with me everywhere I need to go.

            DV82XL said:

    This is not to say SI is useless, as BMS accurately stated, it is ideal for science and engineering, it’s just not all that intuitive for everyday use,

    Not if you were raised to think in feet and inches by parents who thought in feet and inches even if the school system taught real measurements (of course this will correct itself over several generations as people end up with jobs that require them to use metric).

    Whenever I see people saying that the system they grew up with is more intuitive I’m suspicious, not just in terms of measurement systems but also how long the week should be, it’s possible that what a person was taught when they were young is indeed the best match to humans but it’s also possible they’ve become a match to it (kind of like how polyglots who design their own language tend to make something very similar to their native language even despite knowing lots of others).

            DV82XL said:

    which is why it faces continued resistance in the US and why it is still used informally in officially metrified countries. even among those raised and educated in metric.

    All change encounters resistance, doesn’t mean the reasons given for opposing the change are valid.

            DV82XL said:

    Nonsense. In the end these are just tools, and utility of a tool, rather than some abstract aesthetic factors are always going to take precedent.

    Tools need to be designed well, not thrown together with little thought for how they’ll work or how they’ll interact with other tools.

            DV82XL said:

    On top of which, guaranteed that if a novel system of measurement were being designed from scratch today. human-scale factors would be a major design requirement.

    Yes, but would you design anything that didn’t have a single base unit for each quantity and prefixes?

            BMS said:

    Well, there are those who think that it’s best to use the right tool for the job, and then there are those who are so fixated on hammers that they think that everything should be a nail.

    There are also those who think you shouldn’t use multiple different sizes of screw (many of which are obscure) when a single size (with screws and drivers available everywhere) will do the job.

    A decimalised imperial system had one been created before the UK decided to switch to metric might have been able to mount some serious competition to metric but it wasn’t made (though I understand the decimal inch to be quite common in US engineering) and doesn’t appear to offer much other than slightly better backward compatibility with one of the many legacy measurement systems out there (before metric almost every country had its own foot).

            BMS said:

    But since you’ve brought up the foot, I should mention that I’ve found that I can pace out distances on the ground, in feet, by using my feet (in shoes, of course) to a surprising amount of accuracy, considering the crude, but readily available, tool that I’m using. And I wear what is probably one of the most common sizes of shoes for adult males. I’ve never been able to pace out meters as effectively or accurately.

    Good for you, but there are also plenty of people out there who can estimate a metre but couldn’t tell you how many feet away something is.

            BMS said:

    Why? The whole purpose of having computers is for them to do the calculations, not us.

    But we need to program the computers for them to be able to do that and making things even just a little easier on those programming them would seem to be an argument in favour of base 16 if we were to switch bases, admittedly programmers tend to be highly numerate so are more able to handle such complexities.

            BMS said:

    Computers just enable us to combine this “hodgepodge” of units that you complain about far more easily.

    If you’re near a computer with a unit conversion program you know how to use, that isn’t all the time.

            BMS said:

    In most circumstances, the cost of conversion is only one multiplication operation.

    Yes, which is still harder to shifting digits and still adds an additional source of error, it’s also something that only those who are highly numerate are truly comfortable at (yes, we do have widespread innumeracy (how else does the anti-nuclear movement persist?), but for now at least we’ve got to accept that fact and things designed to be easy even for the innumerate are likely to be easier for the highly numerate as well, though it would get rid of the numerical errors that come from converting numbers between base 10 and base 2).

            BMS said:

    The convenience of base 12 is that it simplifies doing common fractions in one’s head and it simplifies the result.

    Base 16 would be inferior if the fraction has a 3 in the denominator but better if there’s an 8, if we’re more likely to repeatedly halve than to divide into three then base 12 would be superior.

    Also base 12 is between two primes which means that it tends to give unwieldy non-terminating fractions, base 16 has a composite number on one side tending to give shorter sequences to repeating fractions.

            BMS said:

    If a computer is available, the base is irrelevant.

    Yeah, but you can’t count on a computer being available at all times and even people who program computers often do things in their head and if you use a base that isn’t a power of 2 you are going to get numerical errors from repeating decimals (0.1 in binary is repeating, so is 0.1₁₂).

            DV82XL said:

    Admittedly any argument about what the common base for everyday counting should be is as sterile as it is moot, however in Pre Roman Europe there were several competing bases used by various cultural groups.

    There have been many different bases used by different societies and the base we count in is probably one of the things we’re least likely to change (we’ll probably fix the mess with our calenders before we change base).

            DV82XL said:

    The ones that contributed to the development of the English language apparently used base-12, (which is why there are unique words for eleven and twelve)

    The Wikipedia duodecimal article seems to indicate otherwise.


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  26. 26
    DV82XL Says:

            Anon said:

    Having the same base as the numbering system is the big advantage, it means you can convert with simple digit shift operations.

    On the other hand in Imperial you don’t often have to: if you are working in inches, you stay in inches, same with feet, yards and miles. Its more or less the same for weight and volume as well, there is little call to shift units in human-scale work.

            Anon said:

    But to use a calculator you need to have a calculator on you, I don’t make a habit of carrying a calculator around with me everywhere I need to go.

    Just about everyone carries a phone these days, and just about ever phone has a calc app,

            Anon said:

    Not if you were raised to think in feet and inches by parents who thought in feet and inches even if the school system taught real measurements (of course this will correct itself over several generations as people end up with jobs that require them to use metric). Whenever I see people saying that the system they grew up with is more intuitive I’m suspicious, not just in terms of measurement systems but also how long the week should be, it’s possible that what a person was taught when they were young is indeed the best match to humans but it’s also possible they’ve become a match to it (kind of like how polyglots who design their own language tend to make something very similar to their native language even despite knowing lots of others).

    There is nothing intuitive about SI in terms of scale, people might get used to it if they have no option but that hardly changes the fact that most of the multiples and submultiples are of an awkward size for everyday use.

            Anon said:

    All change encounters resistance, doesn’t mean the reasons given for opposing the change are valid.

    Nor does it necessarily imply the reasons aren’t valid. This is not an argument.

            Anon said:

    Tools need to be designed well, not thrown together with little thought for how they’ll work or how they’ll interact with other tools.

    Agreed, and the argument I am making is that it was not designed well and the slight advantages of decimal throughout and dimensional convertibility is lost for common use on everyday problems. Most people don’t need to convert quickly from cubic volume to fluid measure in any routine activity. If you do (in science and engineering) indeed use metric

            Anon said:

    Yes, but would you design anything that didn’t have a single base unit for each quantity and prefixes?

    I don’t know, I’ve not given it much thought, but I’m sure I would not base it on fractions of some imaginary line running through Paris, France

            Anon said:

    There are also those who think you shouldn’t use multiple different sizes of screw (many of which are obscure) when a single size (with screws and drivers available everywhere) will do the job.

    I don’t know what you mean by size in this context because as stated the notion is ludicrous. The size of any fastener is based on the job it’s expected to do, and there is no one-size solution, even theoretically.

            Anon said:

    A decimalised imperial system had one been created before the UK decided to switch to metric might have been able to mount some serious competition to metric but it wasn’t made (though I understand the decimal inch to be quite common in US engineering) and doesn’t appear to offer much other than slightly better backward compatibility with one of the many legacy measurement systems out there (before metric almost every country had its own foot).

    Decimal inch is still very common in engineering even internationally in some areas and will remain so precisely for backward compatibility. The cost of full conversion being far to high.

    I will leave BMS to answer the items directed at him/her.


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  27. 27
    Anon Says:

            DV82XL said:

    On the other hand in Imperial you don’t often have to:

    Except when you do or even when someone gives you mixed measurements (e.g. something foot something).

            DV82XL said:

    if you are working in inches, you stay in inches, same with feet, yards and miles. Its more or less the same for weight and volume as well, there is little call to shift units in human-scale work.

    Sometimes, in fact doing that as often as you can is a good idea but if you measure by the inch and buy by the yard…

    While those who measure by the millimetre and buy by the metre have a much easier time.

            DV82XL said:

    There is nothing intuitive about SI in terms of scale, people might get used to it if they have no option but that hardly changes the fact that most of the multiples and submultiples are of an awkward size for everyday use.

    The centimetre is of human scale though the millimetre is usually better (the great thing about millimetres is that they are small enough that you almost never need any fractions, with inches fractions are commonplace).

            DV82XL said:

    Agreed, and the argument I am making is that it was not designed well and the slight advantages of decimal throughout and dimensional convertibility is lost for common use on everyday problems. Most people don’t need to convert quickly from cubic volume to fluid measure in any routine activity. If you do (in science and engineering) indeed use metric

    Which would mean leaning even more measurements.

            DV82XL said:

    I don’t know, I’ve not given it much thought, but I’m sure I would not base it on fractions of some imaginary line running through Paris, France

    I could imagine worse ways to do it though if I were designing a new measuring system I probably wouldn’t do it, the 21 cm hydrogen line might make a decent standard, easy to measure, truly universal and a good size.

    But when it comes down to it it’s unlikely that any measurement system could provide enough of a gain over SI to be worth change (if metric had never come along and we were still living with multiple different feet for every country then we would need something different, though in that case a decimalised imperial would probably be the best option).

            DV82XL said:

    I don’t know what you mean by size in this context because as stated the notion is ludicrous. The size of any fastener is based on the job it’s expected to do, and there is no one-size solution, even theoretically.

    Yes, but is there any point in using uncommon screw sizes when standard easily obtainable ones do the job?


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  28. 28
    DV82XL Says:

            Anon said:

    Except when you do or even when someone gives you mixed measurements (e.g. something foot something).

    Sometimes, in fact doing that as often as you can is a good idea but if you measure by the inch and buy by the yard…

    While those who measure by the millimetre and buy by the metre have a much easier time.

    The point is that these don’t happen that often such that they represent such a huge advantage and again it is offset by awkward scaling

            Anon said:

    The centimetre is of human scale though the millimetre is usually better (the great thing about millimetres is that they are small enough that you almost never need any fractions, with inches fractions are commonplace).

    Better than most of the rest but hardly enough to be really convenient. And so what about fractions? When you use the term millimeter or centimeter you are stating fractional quantities, no different than saying half or quarter when it comes right down to it.

            Anon said:

    Which would mean leaning even more measurements.

    This doesn’t make any sense against the passage quoted. Perhaps you were referring to something else?

            Anon said:

    I could imagine worse ways to do it though if I were designing a new measuring system I probably wouldn’t do it, the 21 cm hydrogen line might make a decent standard, easy to measure, truly universal and a good size.

    A complete system of measurment based on the Planck units has been suggested

            Anon said:

    But when it comes down to it it’s unlikely that any measurement system could provide enough of a gain over SI to be worth change (if metric had never come along and we were still living with multiple different feet for every country then we would need something different, though in that case a decimalised imperial would probably be the best option).

    No we are stuck with SI that’s clear, but Imperial is not going away in English speaking nations as long as its still used in the U.S.

            Anon said:

    Yes, but is there any point in using uncommon screw sizes when standard easily obtainable ones do the job?

    No one will use non-standard fasteners if standard ones are available regardless, except in repair situations on items that were made with such.


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  29. 29
    BMS Says:

            Anon said:

    But to use a calculator you need to have a calculator on you, I don’t make a habit of carrying a calculator around with me everywhere I need to go.

    You do realize that this is an argument for favoring a system of units that results in small numbers for commonly encountered quantities and that is based on numbers composed of factors that simplify division in many cases, don’t you?

    Not having a calculator available is an argument against metric. Metric simplifies the math if you’re dealing with situations that involve order-of-magnitude-scale differences. That’s what it was designed for. Other than that, it doesn’t have any clear advantages over other standard unit systems and, in fact, is less convenient for every-day tasks than the units that are typically used in the US.

    If you’re near a computer with a unit conversion program you know how to use, that isn’t all the time.

    The “units” program has been available on Unix-like systems since at least Version 7, which was released in 1979. Perhaps it was available earlier, I don’t know. The modern version of this program understands over 2500 different types of units, from standard SI to such obscure measures as the ancient Egyptian royal cubit and the Scot furlong.

    For computers this is a trivial problem. All you need is a simple program (by modern standards) and an accurate database of conversion factors. Note that I’m talking about doing serious calculations here, such as what would be expected for scientific or engineering work, not everyday mental estimations. For everyday stuff, units that lend themselves to quick mental calculations are the most convenient.

    Look … ultimately, all units are arbitrary. They are conventions, not magic nor a religion. Each convention has its pros and cons, and we’ve laid out some of them here.

    The reason that the systems of units based on the old English units have persisted is because they’re really convenient. It’s clearly a case of if it ain’t broke, don’t fix it.

    I don’t have anything against SI. In fact, when doing engineering work, I prefer to use SI, when I can. On the other hand, I don’t see what advantage ordering a 50 cl of beer over ordering a pint of beer gets me. In both cases, I get just about the same amount of beer.


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  30. 30
    Anon Says:

            DV82XL said:

    The point is that these don’t happen that often such that they represent such a huge advantage and again it is offset by awkward scaling

    Scaling of SI units has never seemed awkward to me, as I said, I suspect this to be more a matter of what you’re used to than any intrinsic property of the size of the units (provided they’re about the right order of magnitude).

            DV82XL said:

    Better than most of the rest but hardly enough to be really convenient. And so what about fractions?

    For those of us who are highly numerate it’s not such a big deal but there are people who will have trouble, not so much isolated fractions, but when you have multiple different fractions appearing all over the place like 9/16th alongside 1/8 which happens with inches (decimal inches do solve that problem though).

            DV82XL said:

    When you use the term millimeter or centimeter you are stating fractional quantities, no different than saying half or quarter when it comes right down to it.

    Except that it is always the same denominator, that makes things a lot easier.

            DV82XL said:

    This doesn’t make any sense against the passage quoted. Perhaps you were referring to something else?

    Keeping the obsolete units for things outside science and engineering does mean that those in science and engineering will have to learn them as well as metric, admittedly those in science and engineering are better able to handle it but it also has the effect of keeping those not in science and engineering away.

    I’m aware of that one along with the parsec, fortnight system (the attoparsec and microfortnight are quite convenient) and people have come up with a bunch of others, some as jokes, some for specific purposes to simplify calculations (e.g. Planck units), some for fiction.

            DV82XL said:

    No we are stuck with SI that’s clear, but Imperial is not going away in English speaking nations as long as its still used in the U.S.

    Even the US is estimated to be about 40% metric and in the long term at least I’m not aware of any countries which switched away from metric (though there are cases where metrication was abandoned and then bought back).

    Outside the US it’ll be a generational change that could take a hundred years and the EU isn’t going to delay single labelling requirements forever (once that happens it’ll probably speed up the process in the UK).

    It does appear that it’s mostly feet and inches which stick around post-metrication, probably because most people very rarely need to buy things by the length.

            BMS said:

    You do realize that this is an argument for favoring a system of units that results in small numbers for commonly encountered quantities and that is based on numbers composed of factors that simplify division in many cases, don’t you?

    Which would be an argument for more use of the deci- centi- deca- and hepto- prefixes, although in practice it turns out that even people who aren’t highly numerate can handle thousands of millimetres just fine, the point is that you should be using a single unit, not mixing feet and inches (yes, you can get that from decimal inches).

    There’s a reason that the prefixes that aren’t the power of 3s are considered deprecated (except in area and volume where you do tend to need them to avoid unmanageable numbers, though imperial and USCS produce some real abominations there (e.g. acre foot)) and that is that real world experience has shown that the millimetre is more useful than the centimetre.

            BMS said:

    Not having a calculator available is an argument against metric. Metric simplifies the math if you’re dealing with situations that involve order-of-magnitude-scale differences. That’s what it was designed for.

    Which does show up in the real world.

            BMS said:

    Other than that, it doesn’t have any clear advantages over other standard unit systems and, in fact, is less convenient for every-day tasks than the units that are typically used in the US.

    Well if you’re doing work on something originally designed using strange units and you’ve spent your whole life using those same strange units then anything different is going to feel worse even if it were about the same in effectiveness so it’s only when you need to do something that is really cumbersome in the old system that metric would feel better.

            BMS said:

    For computers this is a trivial problem. All you need is a simple program (by modern standards) and an accurate database of conversion factors. Note that I’m talking about doing serious calculations here, such as what would be expected for scientific or engineering work, not everyday mental estimations. For everyday stuff, units that lend themselves to quick mental calculations are the most convenient.

    SI can do that (at least outside of EM, but that’s a specialised area where cgs is somewhat appropriate, though really mks versions of the cgs EM units would be nice).

            BMS said:

    Look … ultimately, all units are arbitrary. They are conventions, not magic nor a religion. Each convention has its pros and cons, and we’ve laid out some of them here.

    Except for things like Planck units.

    But when I look at the old Imperial system or the USCS I have a hard time seeing the pros, they seem confined to “old people don’t know anything else” or “it’s the way we’ve always done things”.

            BMS said:

    The reason that the systems of units based on the old English units have persisted is because they’re really convenient.

    Not really, it’s more a case of people not wanting change or just not being in a situation where they use metric (I noted before that it’s feet and inches that stick around, gallons and all the other volume measures (except for things like beer at a bar where the measurement is part of tradition) die off pretty quickly).

            BMS said:

    It’s clearly a case of if it ain’t broke, don’t fix it.

    If you’re not using the system that most of the rest of the world is then unless you’ve got a damn good reason then it is broke, even if it is an equally good system which it very much is not (decimalisation and reduction to one unit for each quantity could fix it but once you’re done with that you’ve just reinvented metric with different base units).

            BMS said:

    On the other hand, I don’t see what advantage ordering a 50 cl of beer over ordering a pint of beer gets me. In both cases, I get just about the same amount of beer.

    In each individual case of a single unit there may be no difference but it’s when everything comes together that there difference appears.

    Also, there is only one Litre, but there are two different pints currently in use, Americans if they ordered 50 cl of beer would get more than a pint while British would feel cheated.


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  31. 31
    Shafe Says:

            Anon said:

    Even the US is estimated to be about 40% metric and in the long term at least I’m not aware of any countries which switched away from metric (though there are cases where metrication was abandoned and then bought back).

    I have to believe that 40% is grossly overestimated. I doubt 5% of the population could tell you their own height in metric. I worked for a time at a US office of SNC Lavalin, a Canadian company, on petrochemical plant projects. Mechanical, process, and structural engineers there worked with flow rates in gallons per minute, lengths in feet and inches (fractional), temperature in Fahrenheit, weights in pounds (or kips). The Texas DOT moved to metric years ago and finally gave up on it. In the intervening time, engineers were metricizing common English units rather than designing in metric units (think converting a 4″ paint stripe to 100.2 mm.) While I know other engineering disciplines/industries commonly use metric, the only time I have used metric at an engineering company was while working overseas and I implemented it for compatibility with local construction practices.

    BTW, while there’s been discussion here about decimal inches, surveyors and civil engineers commonly use decimal feet, as inches yield unwieldy numbers. Road lengths are measured in stations (i.e. hundreds of feet.) Both of these are convenient and easy to work with, though I have found that meters are also very convenient at this scale. I’m ambivalent about which to use from an engineering standpoint, but I recognize potential difficulty in metric construction when contractors, laborers, and tradesmen are accustomed to English units.

            Anon said:

    There’s a reason that the prefixes that aren’t the power of 3s are considered deprecated (except in area and volume where you do tend to need them to avoid unmanageable numbers, though imperial and USCS produce some real abominations there (e.g. acre foot)) and that is that real world experience has shown that the millimetre is more useful than the centimetre.

    I use the acre foot on a daily basis. It’s perfectly rational to express runoff volumes in terms of the customary area (acres) times the rainfall depth. And when speaking in terms of the volumes used for storm water detention or retention, the quantities expressed in acre feet tend to be very manageable, especially when compared to gallons, cubic feet, liters, or cubic meters.

    As an aside, every civil engineer in the US should be able to recite instantly the conversion from acres to feet.


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  32. 32
    DV82XL Says:

    In the end these older units are so deeply entrenched in some domains that it will be far more than a generation before they not in use there. Continuity, the cost of retooling and back compatibility will keep full metrification from happening for some time. Metric was not well designed, or indeed well thought out and largely owes its wide adoption to the sorry state of international weights and measures used in cross-border trade and the growing desire to implement tariffs at the time than any burning desire for decimalization per se. As for the human scale issue, one only has to look at common kitchen measures that have been redefined in metric, but are still used in the old form like the 250ml Cup, the 15ml Tablespoon and so on and a quick perusal of an extensive list of local measurements around the world shows that a number of them have been redefined this way (officially, even in some European nations) and not as necessary as multiples of ten. Apparently utility of a unit of measurement is more important in these jurisdictions than some nerdly aesthetic.


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  33. 33
    BMS Says:

            Anon said:

    Also, there is only one Litre, but there are two different pints currently in use, Americans if they ordered 50 cl of beer would get more than a pint while British would feel cheated.

    Well … that’s because the British have these weird rules about how much “head” there needs to be on a glass of “draught” beer. They need that extra room to hold the mandatory foam. ;-)

    Look … I’m not pretending that there is only one set of non-metric units. Those two pints belong to different systems. It doesn’t matter that they use the same name.

    In my refrigerator, the milk and the apple juice are both in half-gallon (or two-quart) containers. These numbers are easier to remember and conceptualize than 1.89 L.

    Yes, they could have upped the amount by 6% and gone with two liters. The only item in my refrigerator that is truly metric like that is the two-liter bottle of Coca-Cola, but I note that on the side of the bottle, the serving size is given as 12 oz.

    The best support for the human scale argument is to note how many items that are distributed in metric quantities use metric sizes that have been chosen to approximate simpler English-unit-based quantities. DV82XL has already mentioned a few.

    Aside from soft-drink bottles, the only major inroads that metric has made into volumetric measures in the US is alcoholic beverages (the exception being beer). I suppose this is understandable given how international the alcohol business is, and the change was made at a time when there was still a sizable, but unsuccessful, push to afflict metric completely on Americans. But even so, the most standard container is 750 ml, which was chosen because it’s approximately (to within 1%) the size of a “fifth” — i.e., one-fifth of a US gallon. Once again a unit that is built up from human-scale considerations and ease-of-use with fractions (i.e., the system is based on single or multiple factors of two) has determined the most commonly encountered size.


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  34. 34
    Vanzetti Says:

    >>Ceres: A dwarf planet that is the largest member of the asteroid belt. It could be visited by humans in spacesuits for surface study, but it is so small that it would be possible to jump off it into space. The gravity is not sufficient to allow walking around on it. Therefore, it would be more like clinging to the surface and floating around it than it would be “landing” on it in the normal sense.

    This isn’t true at all. Escape velocity from Ceres is 500 m/s.


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