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Water Found Deep Inside the Moon (nationalgeographic.com)
477 points by chenster on Aug 24, 2017 | hide | past | web | favorite | 267 comments

I've always been more excited about a Moon colony than a Mars one. I mean, compared to Mars, the Moon is ridiculously close.

Many of the same benefits Musk seeks (backup for Civilization, excitement) for a fraction of the cost.

Low gravity and atmosphere on a dome would be more complicated, but again, compared to Mars, it's right there.

It would be a more humble and realistic first step, IMO.

It's questionable that it's really much lower cost. The Moon, as a vacuum body, doesn't give the option of aerobraking or atmospheric entry, which dramatically reduces delta-V. You can get a payload to Mars' surface with less propellant than getting it to the Moon's surface. And because atmosphere is everywhere (which includes oxygen in the form of CO2 and also water vapor), propellant is way easier to make, so it's easier to get your ship back.

Transit time is lower, but the currency of space travel is delta-V, and by that measure, Mars is just as close or closer.

I would guess that the Moon still slightly wins as far as transport costs, but the advantage is much smaller than you'd think, and the far greater resources available on Mars (as well as effective immunity to solar particle events and micrometeorites that Mars' atmosphere provides) tilts the situation strongly in favor of Mars for actual settlement. Joy trips may be cheaper to the Moon, however.

Per glindahl's comment from earlier, if we established a space elevator for the moon[1] it would make the delta-v issues moot. Drop off an pick up supplies at the elevator while swinging by on an continuous Earth/Moon translunar orbit.

[1] https://en.wikipedia.org/wiki/Lunar_space_elevator

There would still be some delta-v. Anyone have a handle on how much? I'm too lazy to look up the data and do the math.

First, I've neither done the requisite orbital mechanics calculations nor have I simulated this. But with that caveat, this is how I imagine it would work.

Assuming your tug is in the translunar orbit (going in a figure 8 around the Moon and Earth with the intersection being the Earth-Moon L1 point. And assuming the tug is significantly more massive than your cargo. As you cross the L1 point you can use a mass driver on the tug to 'shoot' the cargo out behind you which would decelerate it to a low delta-v relative to the elevator base (and slightly boost the tug on its way) and when you came around the other side you hook the cargo through a loop like the old mail planes did [1] and pulling it away (which would impart a small deceleration on the tug as it headed back to earth). Depending on masses and how closely you could match things, the amount of delta-v you would need for the tug to keep its orbit true should be very manageable.

[1] https://postalmuseum.si.edu/collections/object-spotlight/sky...


You might save 2km/s if you can use an elevator on the moon. Which is not a lot compared to a space elevator on Earth, but it would definitely be useful. That could be half your delta-v budget if you're going between the moon's surface and an orbit around Earth/Mars/Venus.

Translunar injection needs about 10.8 km/s, Earth's escape velocity is 11.2 km/s.

I mean to hook up with the elevator.

if we established a space elevator for the moon

Wouldn't you get the same benefit from a Mass Driver, since the moon is a vacuum body?

A mass driver doesn't let you land cargo. But as a way to get raw material off the Moon it is an excellent solution.

You could run the mass driver in reverse for landing, but you'd have to aim well.

That would be rather difficult :-) I wonder sometimes however if you've ever dropped a magnet down a conductive pipe you see how the eddy currents prevent it from falling through. If you had series of conductive rings that were of a large diameter and you had electromagnets on the outside of your cargo container could you make a landing pad that primarily used the eddy currents to slow you to landing velocity? That would be a fun problem to give the physics class.

That would be an amazing feat with the risk of destroying an extremely expensive piece of equipment.

Is it any more amazing than doing an orbital rendezvous?

You brake before getting close to whatever you want to rendevous with. You couldn't brake if you wanted to hit the nozzle of your mass driver to use it for braking.

You brake before getting close to whatever you want to rendevous with.

This makes me question whether you actually understand how orbital rendezvous works. How about as an exercise, you explain why I would say this. Otherwise, I think the resulting conversation would be tiresome and not worth my time.

The relative speed of two objects docking in orbit is very small. You brake or accelerate as you get close to matching orbits.

The relative speed of a capsule and the mass driver will be very high IF you're using the mass driver to slow down substantially. That's in the definition, you're using it to slow down so the initial relative speed at contact must be high. The higher the speed the less energy you have to waste lowering your orbit (slowing down beforehand). If you're slowing down beforehand enough that your relative speed of contact is low then you don't need the mass driver to brake.

How about you, just as an exercise, compare the difference in velocities of the mass driver and the incoming space craft with the difference of velocities of a capsule docking at the ISS.

Ok, you clearly don't understand enough to understand what you don't understand. You don't have to make the velocities or the positions of specific points on the mass driver and the orbit coincide. All you have to do is to make an orbital path coincide with a great circle pathway on the moon. We can already guide spacecraft with this degree of precision. Anyone suggesting that you'd need to make specific point on the mass driver coincide in position and velocity -- that you'd need to brake first -- just doesn't understand what the discussed device is for in the first place. Basically you've just "proved" that you can't land airplanes, because they come in too fast to brake the same 1/10th of a second they touch the tarmac. o_O

If you can't explain my analogy, then I'm just going to conclude you're trolling based on my previously stated disdain for DK syndrome.

The space elevator even on Earth in GEO is a hopeless, fool's dream.

On Earth, it's hard to build due to much higher gravity, higher required orbit, and the atmosphere. Getting much shorter lengths of much less strong fiber to Moon may be more realistic than 20.000 km of super strong carbon fiber to GEO.

I'm not too clued up on the topic, but I was under the impression that a lunar elevator would potentially require much longer cables than on Earth (primarily due to the lack of spin of the moon). From the Wikipedia article [1]

> There are two points in space where an elevator's docking port could maintain a stable, lunar-synchronous position: the Earth-Moon Lagrange points L1 and L2. L1 is 56,000 km away from the Earth-facing side of the Moon, (at the lunar equator) and L2 is 67,000 km from the center of the Moon's far side, in the exact opposite direction <snip />

> Both of these positions are substantially farther up than the 36,000 km from Earth to geostationary orbit. Furthermore, the weight of the limb of the cable system extending down to the Moon would have to be balanced by the cable extending further up, and the Moon's slow rotation means the upper limb would have to be much longer than for an Earth-based system, or be topped by a much more massive counterweight. To suspend a kilogram of cable or payload just above the surface of the Moon would require 1,000 kg of counterweight, 26,000 km beyond L1.

So, we're talking an ~80,000 km one?

[1] https://en.wikipedia.org/wiki/Lunar_space_elevator

This is correct, unlike my assumption of a shorter cable above. OTOH due to lower gravity, the tensile strength required is still much lower. To quote the very article you lonked:

> the engineering requirements for constructing a lunar elevator system can be met using currently available materials and technology.

So what you are saying is that a space elevator is theoretically possible. I think that's step 0 in building something. Being theoretically possible is the most basic prerequisite.

Just because something is theoretically possible doesn't mean it's feasible or practical to build in real life. For example, we have known that it's theoretically possible to build vacuume sealed trains, aka the hyperloop, since before the first airplane took flight. And yet whilst you see planes fly everywhere, you don't see any vacuum sealed trains.

A lunar space elevator is feasible with today's materials (just a whole lot of them, way too much for current technology to transport to the moon). Here's a nice talk by Markus Landgraf, a mission planner at ESA, at 33c3: https://media.ccc.de/v/33c3-8407-an_elevator_to_the_moon_and...

It's not just about the tensile strength of the materials. The dynamics of a lunar elevator necessitates and extraordinary amount of weight to be used as a counterweight nevermind the length of the cables themselves.

Just because something ticks the checkbox of being theoretically possible doesn't mean it's practical or feasible to build.

Maybe in a few hundred years we'll have the means to build something on that scale. It still takes $10k to put 1kg in LEO, imagine the cost of transferring to the Lagrange points.

Sure, the amount of materials needed exceeds what current technology can get even into LEO by several orders of magnitude. Nobody's proposing to actually build a lunar space elevator. All I'm saying is that a super-advanced civilisation could theoretically build one from the materials available to us today, which is not true for a space elevator from the Earth's surface.

Mars has the radiation problem while in-transit, which is still unsolved.

We have already gone to the Moon. Given that the travel time is relatively short, radiation is far less of a concern.

This is why the Moon is attractive. We know how to get there already and it's not too difficult, all things considered. The problem of how to get there and back with humans aboard has already been solved. It's never been done to Mars.

Without a magnetosphere isn't solar radiation a problem, long-term on the Moon?

Fun fact incoming: there is a mini-magnetosphere centered around Mare Crisium on the Moon.


It's only 360km across though...

TMA-1. Erm, CMA-1.

solved by piling dirt over the habitat

IMHO the radiation problem is solved by telling the astronauts that a journey to Mars increases their risk of dying of cancer in the next ten years by 30% or whatever the right number is and asking for volunteers. I'm pretty sure you'd find plenty. I would go, for example.

I was under the impression that the intricacies of creating a small biosphere on Mars pose a vastly larger obstacle than the simple issue or radiation (which can be eliminated by simply shoving enough regolith on top of your colony).

[To put things in perspective] travel time to the Moon is about 3 days, Mars would be about 150 to 300 days (source: Google).

You don't have to use the cheapest, but slowest Hohmann transfer orbit to get to your destination. You can also spend more fuel and get there faster.

A bit of searching suggests that a mildly increased delta-v budget can get your half-year trip down to a quarter-year, but beyond that you're looking at ridiculous costs.

Are you assuming travel is one-way?

That seems okay for probes and maybe problematic for people.

Although the poor slob plan comes to mind:


For me the real advantage of a moon base first is safety. If something goes horribly wrong while we are learning to live on other planets, a return to earth or a rescue mission takes far less time. I am not a space expert though, so perhaps this is wrong?

As NASA has shown in the 30 years, "safety first" does not work as a prime directive, if you want to advance space travel. Musk stated in a recent talk with NASA,"Going to Mars is not for the faint of heart." and "If safety is your top goal, I wouldn't go to Mars."

[1] https://youtu.be/Jv5LjA62Uw8?t=3480 [2] https://youtu.be/Jv5LjA62Uw8?t=3644

'Apollo: Race to the Moon' by Murray and Cox described how the Apollo engineers drew their priorities from Kennedy's speech: Man. Moon. Decade, in that order. There's a difference between genuine safety and bureaucratic safety, something NASA has admittedly forgotten.

I have head that moon dust is reputed to be a consideration, as it creates a type of environmental problem that would not be as extensive a problem on Mars. My understanding is that, due to a lack of fluid and chemical erosion, it tends to be extremely fine and abrasive, and it clings to everything due to static charge, making it hard to keep out of compartments and machinery.

They're both definitely too far for a rescue mission or evacuation that wasn't planned for in advance. In terms of the old eggs/basket metaphor, it becomes a question of whether you want to use half your straw to weave a second basket, just in case the first one breaks, or if you want to use all of the straw to make your one basket as strong, redundant, and well designed as possible.

melt sand it turns into smooth glass, wondering if you couldnt do something similar with a few focused mirrors

Your assertion about getting to Mars with less propellant is super interesting. Can you provide a source for me?

fewer than twenty five seconds of googling: https://en.wikipedia.org/wiki/Delta-v_budget

From LEO to the surface of the moon is 5.9 km/s

From LEO to the surface of Mars is 4.1 km/s

Unless I'm misreading something, both the text and graphic of that page seem to indicate it's 4.1km/s from low Mars orbit to the surface of Mars. I can't find anywhere saying it's 4.1 from LEO.

I get 2.5+0.7+0.6=3.8 to get into Mars Transfer from LEO. If we were to execute perfect aerobraking, the rest would be free. It for sure wouldn't be perfect so some fuel will be needed but not that much.

Source: https://en.wikipedia.org/wiki/Delta-v_budget#Delta-vs_betwee...

People way underestimate how far away Mars is. To give you a sense of scale, the settlers of Jamestown came from London. As the crow flies, that's about 3,790 miles.

If we treat that as equivalent to settling on Mars, then for them to settle on "the moon" would have been a mere 26 miles from London. Perhaps Canvey Island on the River Thames. If we can't manage settlements that close, we really aren't ready yet for the long voyage across the sea.

In terms of distance, sure.

In terms of delta-v, the budget for the moon is upwards of 50% that for Mars.

EDIT: The 50% figure is from memory, and upon further reflection is probably not quite right, so take it with a grain of salt. I just wanted to point out that distance is not the only relevant metric.

>The 50% figure is from memory, and upon further reflection is probably not quite right, so take it with a grain of salt.

You're actually underestimating. Mars has an atmosphere, so spacecraft can use aerobraking to significantly reduce the delta-v required to get there. The moon has no such benefit — propulsion is required all the way to the surface.

The advantage of the moon, of course, is that it's not limited to transfer windows every two years. If there's an emergency or resupply is needed (or you just want to expand the mission), another lander can be sent at any time. (With some restrictions, like hitting your desired landing spot and making sure the sun wasn't in the Apollo crews' eyes at landing. But regardless, no longer than 28 days between windows.)

You need a far bigger (heavier) craft to get to Mars. You'll need years worth of food, water, air, you'll need radiation shielding, much more space per crewmember, more redundant systems and backups, etc.

Look at the size of the Apollo.

Years? Absolutely not. Transfer can be done in about 90 days, less (30 days) if you pursue aggressive entry, high orbit refueling, and nuclear thermal propulsion. Assuming you're settling the place and not just doing flags and footprints, transfer time is the important part.

That's astoundingly quick. 30-90 days is in the same range as crossing the Atlantic via tall ship. With transfer time that low, it really does seem feasible. The two year gaps are a bit rough, but there are plenty of ways to plan for it.

Nowadays ships cross the Atlantic in less than a week.

Well, if any of these silly EmDrives ever work out, maybe we can get Mars down to that time too.

For the journey, yes. But for permanent settlement, in both cases you'll need of the order of years-worth of supplies while you become self-sufficient.

Back on-topic, the discovery of water on the moon makes this more achievable there; otherwise Mars's resources might have actually meant less resources were required.

You don't have to send all the supplies at once though (you shouldn't actually). You can send many small missions, each providing some parts of a Mars base before sending any humans. See for example the Mars Direct plan by Zubrin: https://en.wikipedia.org/wiki/Mars_Direct

But the presence of water on the Moon is more limited than the presence of CO2 and H2O on Mars. That could be significant for self-sufficiency. Especially if we could find a way to make plastics from CO2 and H2O in a reasonably small mobile device. Just grow your colony out of the stuff you suck out for the atmosphere...

You don't need radiation shielding to go to or stay on Mars. The health risk from the excess radiation is moderate, should be a very low priority for an adventurer.

Shared this video[1] about the same topic above[2]

[1] https://www.youtube.com/watch?v=h2nqgKL2JQU [2] https://news.ycombinator.com/item?id=15093353

The aerobraking advantage only works getting there, not coming back.

ACKSHULLY - aerobraking on Mars is a chore. The atmosphere is dense enough to burn you to a crisp, thin enough it won't help you slow down - much.

Look at the marvel that is the Skycrane. Not needed for the Moon.

>thin enough it won't help you slow down - much.

No. It's thin enough you can't land with parachutes alone. It's still enough that Mars Global Surveyor used it to make up a 1,250 m/s delta-v deficit.

Is landing on Mars more complex than a thick atmospheric landing on parachutes or an exoatmospheric landing on propulsion only? Yes. But the atmosphere still saves you a lot of delta-v.

[0] https://mars.jpl.nasa.gov/mgs/sci/aerobrake/SFMech.html

> It's still enough that Mars Global Surveyor used it to make up a 1,250 m/s delta-v deficit.

It took MGS 15 months (not counting delays) of aerobraking to do that. MGS only weighed 1000kg too. Maybe it could work for shipping large, pre-assembled, empty hab modules to Mars before people get there. (Low density, higher drag, no rush.) But not practical for actual human bodies or even resupply since the Hohmann transfer takes a mere 8.5 months. Adding an aerobraking maneuver could easily triple the transit time.

It only took that long because MGS was aerobraking into orbit and wasn't designed to survive the stress of lower atmosphere turbulence, so only used the uppermost layer of the atmosphere for braking. If your going to land, obviously you get to use all the atmosphere and also can use parachutes. Something a problem braking into orbit can't do.

Surface probes do direct descent trajectories. There is no extended series of repeated braking passes. You do it in one go.

> If your going to land, obviously you get to use all the atmosphere and also can use parachutes. Something a problem braking into orbit can't do.

Also, you can use lithobraking.

For a dramatic coverage of this exact subject, I highly recommend 'Curiosity's Seven Minutes of Terror' [1] from NASA JPL.

[1] https://www.jpl.nasa.gov/video/details.php?id=1090; or on Youtube: https://www.youtube.com/watch?v=h2I8AoB1xgU

Note this is before SpaceX proved supersonic retropropulsion works just fine. Atmosphere is now a huge asset for Mars EDL.

7 minutes of terror is a fantastic video, but that line in it always bugged me. Atmosphere is an enormous asset for Sending large payloads to Mars now that we know supersonic retropropulsion works just fine.

BUT ... getting from the moon back to earth is very easy and fast. From the mars not so much.

However, you might use a space elevator at L1 or L2 (or both) that allow capture of HEO or launch or inter-system vehicles with only efficient high impulse rocket motors.

Note that you could use Spectra/Kevlar or other common high strength materials with a taper ratio of only 4:1 with a lunar elevator. It might take "only" ~50 tons of spectra to hang the weight and allow lifts of a 1000kg or so... its much more doable than earth or mars.


It makes much more sense to use the moon as a stepping rock. At least my KSP experience has taught me that :)

Every experienced KSP player uses Minmus of course, not the Mun.

My experience in KSP usually ends with an explosion

Yes, so those two metrics boil down into time cost and fuel cost? Any other costs for just the transit?

Nope. Mars is actually lower than the Moon due to atmosphere.

Replying just to let you know I never thought for one second I'd see Canvey Island referenced on Hacker News.

Maybe the distance itself is why people are so excited about Mars. When you go to the Moon, human civilization is right there and can interfere with whatever you may wish to accomplish, while on mars it seems so far away that earthly powers will be hard pressed to keep control, but not far enough as to be unfeasible to go to. You can start something new, something your that's your own. It's like the difference between going to Ireland and going to America. Or at least it evokes those kinds of emotions. Truth is you'll be so reliant on Earth in both Mars and the Moon for several generations as to make this distinction moot, but humans are more emotional than rational in nature.

This is interesting, because I think both you and parent commenter identify an interesting principle when thinking about space colonization.

Maybe at the end of the day, the dumb, brute cost of traversing an extreme distance is a tougher problem than colonizing someplace nearby thats vastly less habitable. One problem is conceptually simpler but extremely costly, the other is conceivably lest costly overall despite being way more complicated.

Maybe you are right, 50 million miles is not "far away" to me.

Inasmuch as Mars with our current technology offers no back up for civilization, the same can certainly be said for the moon. I would argue over that the moon actually has some benefits Mars lacks, in addition to proximity it has a much lesser gravitational field and therefore a much lower delta V. Moon colony could realistically jumpstart space and vacuum industries beyond LEO, and frankly it would probably give us a chance to test the many technologies we'd eventually need on Mars without having to actually make the trip to Mars.

Most of all the moon would be an excellent way station for asteroid mining .

When the topic of Backup for Civilization comes up, instead of Wall-E, I tend to think of Elysium, i.e. the backup option is only for the wealthy, leaving the rest in a worse state.


> the backup option is only for the wealthy, leaving the rest in a worse state.

Like most technology, it flows from the rich to the poor eventually as it becomes cheaper. The important part you omitted is that it leaves the rest in a worse relative state. Their absolute state is no worse, and likely better.

Arguing against a backup for civilization (or more appropriately, a backup for the species) because it will be used by the rich is like arguing against a cure for cancer because the rich will benefit before anyone else. In the end, a cure existing still drastically increases the chance the poor might be able to make use of it, from zero to some non-zero amount.

This is all also ignoring the fact that when it comes to species level propagation and survival, I would rather Hitler and his closest Nazi associates makes it off world sustainably in the event of a species level disaster than nobody. My commitment to making sure Humanity survives is much more than my commitment to ensuring we are a caring and accepting civilization. We can rediscover valuing life, but once we're gone, the chances we are coming back are essentially nil.

Why is humanity's survival important?

It's important for the exact same reason you're able to ask that question. Without humanity, who asks why? Humanity is, to the best of our knowledge, the best and possibly only chance of increasing understanding of the universe. I care about that, as well as about our species generally in what is likely an evolved and chemically reinforced way. At some point that may be less true, and I would care less (but would still care).

At a meta level, if you truly don't care about the survival of your species (even if only through the survival of your own relatives and loved ones), you're an evolutionary dead end.

It sounds like you value the persistence of understanding in a way that just isn't particularly important to me. The survival of my loved ones -- and that's a category that can go across species -- is absolutely important to me. The survival of evil space Nazis? Eh.

That said, I also don't really think I see being an evolutionary dead end as too huge of a concern. Many of us appreciate things that aren't truly keen from an evolutionary perspective. Consider how many of us will remain happily childless (perhaps not yourself) well into our 30s and beyond. Not amazing for propagating our own personal genes and yet, they're decisions we actively and happily make.

> The survival of my loved ones -- and that's a category that can go across species -- is absolutely important to me. The survival of evil space Nazis? Eh.

The idea is that if it's between all people dead, or all people except evil space Nazis, I'll take evil space Nazis. Just because they are evil space Nazis now doesn't mean they will be hundreds of years from now, but they'll never get that chance if all humans are gone.

Human history is largely a story about bigoted, insular racist violent psychopaths becoming slightly less of each of those things over time. I don't see why that trend won't continue in general even if we hit a local maxima of fascist oppression from time to time (as this would be).

Because I love people, I can understand the concept of loving people in general, and want other people to be able to experience that. Human extinction means that nobody might ever experience that again, and I think that's a shame, and will do what I can to prevent that type of outcome.

> Many of us appreciate things that aren't truly keen from an evolutionary perspective.

There isn't appreciation of that type without people to do the appreciating. Your ability to appreciate it is provided by our current circumstances. I think keeping those circumstances active is worthwhile. Otherwise you are taking more than you are giving to the species as a whole, which is unsustainable if too many people do so. Even if you don't care about how sustainable it is, you would be riding on the hard work the rest of the species is putting into the system to propagate. Don't be taker.

If it's up to me between no humans and evil space Nazis? I'll take no humans every time. We're a stain on the face of existence, we pollute and destroy our environment, we abuse our own species and others as a matter of course, and we're just overall destructive. The only thing that changes that is that sometimes one or two people rise up and decide that they will resist that status quo and do something about it. To allow a group of people who are evil in the conception of a default-destructive species to be the only ones left? Better to let the species die.

I think you are deeply misjudging the complexity of the human experience and being particularly blind to or biased against our collective history. If you spend any amount of time talking to people or even just reading the personal writings left to us by the ages you quickly realize that everyone who has ever lived is no different from yourself, we simply made different choices based on the information available to us, for good or evil. Anyone, given the right conditions, is capable of being a monster or a saint.

Survival of humanity isn't important universally. The universe doesn't care. But it's the most important thing for humans.

> The universe doesn't care.

And that's exactly why it's important.

> Survival of humanity isn't important universally.

Unless there is something there that cares about it, there is little reason for the universe to exist - nothing would know the difference.

Which is why it actually is important universally.

> But it's the most important thing for humans.

No, it's more important for the universe to have humans, than it is for humans to have a universe.

If the universe did not have humans (or another sentients) then it might as well not exist. AKA: Humans super important to the universe.

If humans did not have a universe, then humans would not exist. If humans did not exist then nothing is important to them.

That seems like a circular argument. It's not important for the universe to have a purpose, or to "care"...except to us. Things don't need a reason to exist.

What is the difference between a universe that doesn't exist, and one that no one notices exists? There is no difference.

The difference is itself: one universe exists, one doesn't. Notice doesn't define existence. Measurability doesn't define existence. Meaning doesn't define existence.

Why are you saying that the universe might not exist if it were not for humans. I have a few questions for you.

1. What if humans become extinct in a few hundred years? Should the universe then not exist anymore and make more lifeforms?

2. What if there are billions of other "intelligent" species in the universe? Why should the universe care about one specific species that is actually not that great, and very destructive.

3. What if this universe is just an experiment, a petridish and we are just one out of billions of parameters.

4. What if our kind of intelligence is really not that impressive, what if intelligence of dark matter entities, which we don't know about anything is much more powerful, what if even that is not that impressive?

Again, the universe doesn't care. It is not a person, it doesn't have a plan, it is neutral, unless we met our "gods" one day. Humans are just a blip among much larger things that are happening in the universe.

> Why are you saying that the universe might not exist if it were not for humans.

I didn't say that. I said there is no difference between a universe not existing, and one that has no one who notices that it exists.

Re: 1 and 2 I said "(or another sentients)".

3: I guess you are implying someone made the universe and is running it? In that case, they are the ones aware of it, so that counts.

4: Hu?? What are dark matter entities? We notice the universe and care that it exists. That's enough. The specific level of intelligence, (or aggression for that matter) does not matter.

> Again, the universe doesn't care.

That's the point. WE care, and we are the ones that give the universe a "voice" as you will. We speak for it, we do the "caring" for it. Without us (or other sentients) it might as well not not exist.

> Humans are just a blip among much larger things that are happening in the universe.

Just because someone is big doesn't make it important. Importance comes from meaning. A really big explosion in space, that does noting at all, is completely unimportant. While a tiny little seed that someone wanted to plant matters a lot.

I care and I am part of this universe, like you and every other human on this planet.

So at lest partially universe care about humanity.

"We are the universe experiencing itself"

Because the universe drives towards increased complexity.

Solar fusion creates heavier elements. Gas clouds collapse into stars and planets.

Life, while insignificant on a mass scale, nonetheless represents one of the greatest increases in complexity and diversity the universe has thus far produced.

For that reason alone, it's sacred, and should be cherished.

To date, humanity has been the only species with a demonstrated ability to reliably lift portions of the Earth ecosystem out of the planetary gravity well.

It is therefore essential to creating self-sustaining spores filled with Earth-life.

Humanity must survive if Earth-life is to survive.

As such, humanity also gets to pick the species (or subspecies) that get included in the spores. Autotrophic algae will likely get a guaranteed berth on the ship, whereas elephants are going to have to breed themselves down smaller and smarter if they want off this rock.

It's literally the definition of the word: of great significance or value; likely to have a profound effect on success, survival, or well-being

why would it not be? Life exists to create more of itself. We inherently want there to be more of us.

Pipe down, Skynet.

Elysium isn't about space stations, it's about wealthy enclaves. Those already exist, and our society is becoming more stratified every year. There's no need for the very rich to leave the planet for that.

Backing up the species is about keeping a strong diverse stock of human genetics and knowledge somewhere safe from whatever harm might befall the earth.

Under those terms, I for one do not care whether it's rich people or poor people. I doubt I'll be in the 0.00001% of the population who are part of it regardless.

At this point, no amount of money will save you, we need Earth for food at the very least. That may change, but not soon.

For another take on backing on human civilization, check out Neal Stephenson's novel Seveneves. Humanity evacuates 1500 people to orbit as moon debris decimates all remaining life on the earth's surface. As a story, it's pretty dry, but as a thought experiment, it's very interesting.


I wouldn't call it dry. I thought the writing style was a little juvenile, but the ideas are generally interesting as you said, the descriptions of technology are fairly detailed and I thought of it as a rollicking adventure by the end.

Dry implies flat and drab to me. If anything, I think Stephenson's flaw as a writer is that he comes across as an excited boy who just wants to tell you everything he's been researching, rather than show you naturally with a well-written story.

I was totally engaged by Seveneves, right up until the time jump, at which point I completely lost interest. The hard rain stuff at the beginning is totally fascinating.

Same experience. It was like it was written by two different authors (one fantastic and one awful).

You can also rotate the crew on the moon. Can send things to the moon you didn't anticipate. Can send replacement/repair parts.

Can't do that for Mars.

Of course you can, it just takes a few orders of magnitude longer.

If the one specialist in your mission dies and it takes 8 years to send a new one, that's not called an effective replacement.

It doesn't take 8 years to get to mars unless you are waiting for the most efficient orbits with chemical rockets. NERVA was built and successfully tested 50 years ago, and it will get you to mars in a few months.

Just send the information and teach a new specialist onlune.

(And don't forget to take an ebook-reader with you in the spaceship with an extensive e-books library).

Has it ever taken 8 years to send something to the moon?

At least in the US, if we urgently needed to send something to the moon in 8 years, we would not be able to do it. Between politically making it happen, deciding who spends the money on it, choosing a contractor that represents the right disadvantaged special interest group, years of contract negotiation, town hall discussions, environmental impact studies, project management failures, budget overruns, pork barrel carve-outs and jobs programs for various congresspeople's districts, etc. it would take way more than 8 years.

Depending on how you count, e.g. May 1961 (Freedom 7 flight) to July 1969 (Apollo 11 flight), yes.

By then you'll be dead if you actually needed those replacement parts.

Mars has atmosphere for aerobraking and ISRU possibilities that the moon does not. In many ways, it is much more practical from a spaceflight standpoint. That's not to say that there aren't possibilities for both, but Mars is seen as the preferred choice for a variety of sound reasons.

The Martian atmosphere is next to worthless for aerobraking human-scale infrastructure.

One of the most significant points in the Moon's favor is the (relative) ease with which a space elevator could be built. It doesn't need unobtainium, current structural materials are strong enough.

SpaceX have run the simulations and while Red Dragon is possible, there's no way they can adapt Dragon to land on the Moon without adding an extra stage. That difference is entirely down to Aerobraking. Even the thin atmosphere of Mars makes a huge difference.

Anyone who plays KSP can confirm this for you, especially using the Real Solar System mod, though the same lessson is apparent even in the stock game.

We can also look at delta-V charts. Earth to the Moon is like 16.4km/s, Earth to Mars is like 14.3km/s using every available aerobraking opportunity (6.4km/s saved) and assuming 500m/s for the final powered landing. (The Red Dragon plan called for aerobraking from 6km/s to 540m/s and then switching to thrusters.)

Is that 2.1km/s really a whole extra stage? Or can it be met by reducing cargo capacity somewhat?

Two interesting points about Red Dragon - it wasn't feasible to put parachutes on it so its aerobraking would have been greatly limited. It wouldn't have much surface to use for deceleration in that case. I'm curious just how long it would have spent aerobraking, SpaceX's docs don't seem to mention that. And it was cancelled a few months ago with the intent of designing a "vastly" heavier lander, for which aerobraking will be that much less practical.

edit: But I can do a back of the envelope calculation. Decelerating 6500kg from 6km/s to 540m/s is 116G joules. The diameter is 3.6 meters so a molecule of air in from of the Dragon would be displaced (on average) 0.53 meters. Let's assume the atmosphere is a constant density (0.020 kg/m^3). Assume a drag coefficient of 0.05 (and ignoring the lifting body effect) that is around 200kN of force, tapering down to 1.5kN. That is like 3000 km of aerobraking at maximum atmospheric density and should take around 2300 seconds. But that depends a lot on the deorbit profile. I'm going to need a bigger simulation...

For Red Dragon they were going to add an asymmetrical 'sled' under the capsule that alters its geometry to form a lifting body, so it could spend significantly more time up in the atmosphere braking than most custom designed landers would. The sled would be jettisoned immediately before the propulsive landing.

It's not an ideal design, but this way they would only have had to make minor changes to the capsule, mainly to add more fuel for the landing than the regular design.

Okay, I concede it is totally possible. After including Nasa's atmosphere model and some drag coefficients from super-sonic bullets, it looks like Red Dragon's aerobraking maneuver would take 1600 seconds, cover 4800km and leave them with 3600 meters of altitude. (Those supersonic drag coefs were what really made the difference since they are around 0.3 at hypersonic and rise to 0.6 as it slows.)

If your plans for an extraterrestial base require building something as expensive as a space elevator, you'll never get the funding. Any plan for human settlement must be splittable into reasonable annual budgets. Being to ambitions is what killed many previous missions.

The same can be said of a space elevator around Mars too, of course. (Though not the earth).

"Mars' atmosphere is in the perfect goldilocks zone of being a total headache" - https://www.youtube.com/watch?v=h2nqgKL2JQU

Thank you, i couldn't remember where I had heard this before.

Okay, I'm basing this mostly on playing Kerbal Space Program, but hear me out here...

I believe the extra delta-V you need to get to Mars is less than the delta-V you need to slow down to land on the Moon.

Especially since a Moon colony would make building and sending future stuff sooo much easier, a very big part of what we work on now and what costs us money (the big decider, whether we like it or not) is "how do we get that off of Earth and into space". If we could assemble on the Moon first, Mars and beyond would be much easier to reach.

And for almost everything that is not launching related (radiation, resources, ...) a Moon colony faces the same difficulties with better recovery possibilities in case of catastophic failure, so it's a better learning ground (I mean, if your food producing bio dome or whatever dies for some reason you probably want to be on the Moon with emergency supply very close rather than out there on Mars).

The only downside I see is that a Moon colony would not offer the same quality of "backup for civilization" as Mars would, and it's also a harder sell on the public and politician I think.

I'm all for building Lunar outposts, but colonization is not really practial. Luna simply doesn't have the natural resources to sustain a civilization. Yes there is water in the regolith, but nowhere near as much as on Mars. And critically, Carbon, Nitrogen, Phosphorus, and Sulfur are only present in trace amounts. Nearly all of the elements essential to life will have to be imported, either from Earth, from Mars, or from asteroid miners. I'd love to visit, but nobody is going live there permanently any time soon.

I imagine the first step for producing food in loco would be hydroponic agriculture on either place. Tiny bits of dissolved nutrients (extracted or brought along) should be fine. Actually building soil would be a second step.

Once you get there, almost everything is a little easier on Mars, but getting there (and back?) is a heck of a lot harder.

"Carbon, Nitrogen, Phosphorus, and Sulfur are only present in trace amounts"

Is this because we havent found them yet, an educated guess or the moon somehow gets rid of these?

It's because the Moon lacks an atmosphere.

CO (and then CO2) form at high temps, so elemental carbon doesn't have much chance to condensate to a "rock" form in regards to non-stellar celestial bodies. These float off into space, no atmosphere to contain them.

At the temperatures/pressure of the moon, Nitrogen rapidly boils off and floats away as well.

Not sure about Phosphorus and Sulfur, but I'm sure they can be either directly or indirectly related back to the moon's lack of an atmosphere as well.

Wut? Pretty sure phosphorus never goes atmospheric

Exactly. Hence why I didn't want to specifically comment about phosphorus on the moon, as I have no idea.

The moon was mostly cast off from the Earths upper crust during an impact when earth was still forming. As a result it's mostly composed of lighter materials and lacks heavier metals and elements brought the the surface on Earth due to magma flows in the mantle and vulcanism.

I rather have Civilization backup in Mars. If the Earth goes, the Moon wouldn't be in a very good shape. Just like I wouldn't go hide in the kitchen, while the living room is burning down.

This is one of the biggest points people miss when talking about civilization back ups. I tend to think of it in IT terms: the moon is like an offline but onsite backup. It will protect you from most internal cockups where as Mars is more like an offsite backup which will protect you should your building (Earth) get taken out

Meteor impacts and supervolcanoes seem to be the near-term worst case scenarios, neither which change the state of living on the moon. I don't know that the metaphor of them being under the same roof works.

I know the risks are astronomical (literally), but anything significant enough to alter Earth's mass would also alter the moons orbit.

I just think if we are talking about an extraterrestrial base for the sake of "backing up" the human race then it is prudent to pick a location that isn't in any way dependant on the master copy.

However I appreciate other concerns also take priority as well (cost, practicality, etc) but if the topic were strictly just about backing up humanity then my ideal candidates would be Mars plus some location outside of our solar system. But I'm venturing well into the realm of sci-fi now.

What's the point of a backup though if you can't restore?

I'm not sure I understand your point. Are you implying we shouldn't be backing up the human race because "what's the point if Earth is destroyed?"

If there's humans, the possibility to restore exists.

If there's no humans, the possibility to restore is gone.

It's not necessarily a either or situation. I can certainly see this work out in a way where you can iterate quickly on the moon resulting in technologies maturing quickly that you will eventually need on Mars and ultimately get you there faster than trying to go straight to Mars.

I'm having trouble thinking of catastrophes that could take out both. Well, I can think of a few (bio-weapon, nearby supernova) but they would take out a Mars colony just as easily.

I think they meant that if we have civilisation collapse on Earth then the Lunar folk are screwed too, because their supplies would be cut off permanently.

Why would the Moon be any less independent than Mars? It is only 20% less delta-V to ship something there. It is just as much in their interests to become self-sufficient.

Depends how much supply they have. A mature lunar colony should have a stockpile and equipment sufficient for reconstructing any equipment needed.

At that point, asteroid mining may be cheaper than launching resources from earth.

The biggest problem is getting into orbit.

https://api.media.ccc.de/v/31c3_-_6180_-_en_-_saal_2_-_20141... Around 19'th minute.

Then again, Mars is far so it would take some time to get there. Then again again, most of the ships wouldn't have to have people aboard. Edit: It helps that Mars has an atmosphere of sorts.

No reason that 7 billion humans can't work towards both at the same time. Many technologies (like cheap, reusable heavy-lift rockets) will be useful for both. Bezos seems interested in the Moon and Musk in Mars, but I don't think you would hear either of them saying one place must have a colony before starting to work towards the other. Let a thousand flowers bloom.

Closeness aside, the gravity on mars complicates a lot of things from landing to taking off - which currently dictates that this is a one-way trip.

A moon base is much simpler in both scenarios and return trips are achievable (has already been done FORTY YEARS AGO).

I have to admit I was initially put off by the guy's voice and hair, but it's a thrilling talk.

When he says the real science is on Mars, though, I'd raise the challenge and say it's on Europa, Enceladus, Io, Ganymede and Callisto. I mean hot oceans protected from radiation through tick ice. What else do you need?

We may find fossil and even bacterial life on Mars (and that would possibly be the greatest human discovery yet), but I bet we can find a thriving ecosystem full of complex multicelular life on one of those Moons.

The Moon can be useful as an outpost, like Antartica. In contrast Mars can be made into an actual home for us.

Also, as others have pointed, closer/further is a tricky thing when talking about interplanetary travel: http://www.marssociety.org/home/about/faq/#Q12

There's at least one colonization plan floating around using what's essentially Apollo-era hardware for getting to Mars for that Delta-v related reason.

Agree with all of that, been saying it for years. Even people who aren't into the whole space exploration thing do agree that the Moon would be much better for the foreseeable future.

I think the 0-step should be a sort of treaty to decide which set of laws and jurisdiction should have a space colony on the moon. Not easily solvable

It wouldn't really be relevant. For why, read The Moon is a Harsh Mistress.

TLDR: The moon colony will be able to make its own rules and keep earth at bay.

I'm sorry but this is just silly. Just because something happened in a novel published more than 50 years ago does not at all make it likely to happen in real life. The Moon is much less habitable than we thought it would be in the 60s, meaning any moon colony will be very dependent on the Earth for the foreseeable future and the rock launcher wouldn't be bulidable with the kind of infrastructure in the novel.

The point is it's really hard to impose laws and forms of government on peoples living days or months away from you. Sooner or later they'll want to make their own.

Same lesson as KSRobinson's Mars series. Same lesson as the United States secession and rebellion against Great Britain.

You make the government local, or the local government that eventually forms will rebel. Then it will beat you, because it can react to the local situation more quickly.

You might be able to control the Moon from Earth, but Mars will definitely be self-governing. It's all about the latency.

Why didn't Canada rebel? Australia? Falkland Islands? Malta? India? Nigeria? Belize? Tunisia? Samoa? Puerto Rico? The Philippines? Guam? Most of the Caribbean? In fact, off the top of my head the only times that you saw a colony rebel in a circumstance like that was the U.S and Haiti. Now you can point pout that most of the countries I mentioned are independent or quasi-independent today but most of them got that status after WW2 when it was actually much much easier to travel. And all of those countries also had the benefit of being able to have a breathable atmosphere, a magnetic field, and land which you can grow crops on none of which Mars or the Moon have which would make them much more dependent on their home nation.

I'd guess that was because there are more factors in play than just distance. But I get the sense that you're trying to invert a logical implication somewhere.

The comparison you should be making is the rebellion of a distant colony versus a more local rebellion. I.e. why did the American Revolution succeed, but the Whiskey Rebellion fail?

You said "You make the government local, or the local government that eventually forms will rebel. Then it will beat you, because it can react to the local situation more quickly. You might be able to control the Moon from Earth, but Mars will definitely be self-governing. It's all about the latency." Which sounds like you think distant colonies successfully rebelling is a rule of history that means Mars will inevitably be self-governing. I pointed out that in fact, most colonies did not rebel and only became self-governing in the 1900s it no longer took months or weeks to travel to them.

The Whisky rebellion was essentially an armed tax protest, of the kind that happened fairly often in American history and before independence. Its goal was never to topple the US government or create a separate nation.

Says who? Plenty of empires had people living that far without rebellions breaking out. Yeah the US rebelled against Britain but Canada, Australia, and a bunch of other places didn't. Hell, most of England was more than a couple days away from London for most of English history without breaking away. Let alone a larger country like China.

How much of the British Empire still reports to Britain?

One of my all time favorite books.

I like how the power roles between the sexes on the moon are reversed too. The matriarch has all the power because women are scarce and they take on many husbands out of this need. They always hold the cards and culturally everyone accepts this.

Also, because the value of women is so high no man ever dares attack one less they be sent out an airlock. It is cultural justice. No trial. A man just knows that if he is seen assaulting a woman, he is dead. The community can't afford to lose a single female.

Plus with all the talk of the A.I. Armageddon the book plays right into that discussion.

The American west was once very lopsided as well, males became cowboys and the women rarely traveled west. In one generation the few women out west had equal numbers of both gender kids and now that history is not important to the culture.

The book is interesting, but it was written for a society that doesn't exist. Women and men will not be as lopsided in a colony. The first few ships might be mostly male construction workers, but after that expect to see a much closer balance.

Many societies have historically been matriarchal. It just happened that Christianity, Islam (maybe Judaism? not sure...) were patriarchal and societies that embraces these religions came to dominate most of the other society/ peoples.

I do hope the future will be more "centrist", neither patriarchal nor matriarchal.

Will be in how much time? Considering the first man who went to the moon needed to place a national flag on it asap, I think we are risking a serious conflict and IF we could avoid it better we do whatever is possible BEFORE having people fighting directly on the moon.

Mars is effectively a vacuum (for people purposes) anyways, just like the moon. And both are bone-dry, which means lots of static charges when you go outside.

The main difference is that Mars has sufficient weather that the dust is roundish, whereas the moon dust is composed of extremely sharp shards.

IMHO, if we can't make a go of it on the moon, we have no business going to Mars.

You know there is water on both right?

If only there was an article which talked about water on the moon...

But seriously, since you're going to be unnecessarily pedantic, you're still wrong. Bones (even dry ones on earth) have a MUCH higher percentage of water content than the average location on Mars or the Moon.

Perhaps you could explain why nit-picking is so important? HN isn't a science forum. There's no expectation that people post full scientific justification (with references) for what they say.

It should be about people making polite conversation. Instead, you're missing the point entirely. Which is sad.

just like there is water in the most arid deserts on earth ... and still they are a jungle compared to moon and mars. So I think, boone-dry is a quite correct description ...

Adj. 1. bone dry - without a trace of moisture; as dry as a weathered bone

metapher - something not allways meant to be literal in a scientific sense. Bone dry is a very good description for a desert for a ordinary human beeing, as it means you wont find water you can use

For a desert on a planet, but not for an entire planet. You sound ridiculous claiming Mars is bone-dry. It is not a "very good description". It is false.

No, he is using the word incorrectly. They are not bone-dry.

Mindless pedantry.

And it's right bang smack in the habitable/goldilocks zone.

Would digging a big valley (no dome), and putting air in it be ridiculously inefficient? Of course you'd lose some over time, but at what rate?

The moon is a pretty terrible backup for Civilization.

A lot of the things (majority) that would eradicate life on earth would also eradicate life on the moon.

Someone else asked this as well but I haven't seen a good answer: what scenario destroys moon and earth but leaves Mars fine? I can think either of stuff that only impacts earth like meteors, nukes etc on one hand and issues like a supernova or a stray planet coming through the solar system on the other hand.

So, why is Elon Musk not excited about Moon?

As an amateur Musk watcher I actually think he will be interested in the moon or more likely some sort of permanent space station as I think he's only now realizing how difficult mars would be as a first goal (also he's very good at surprises)

I wonder if launching a trip to Mars would also be easier from the moon?

Yeh seriously, I've always said it as well. Establish a base there first, figure out what works, and what doesn't work. I really think Mars is just too much, too fast. It's way too harsh, and a one way trip. At least we can realistically send help to the moon.

I'm guessing the long 28 day(day) cycle is the biggest issue, along with few natural resources.

Although the Moon is much closer and "right there" for us, it's subject to numerous meteoric incidents, some of which are disastrous enough to wipe out any settlement we set up there.

Moreover, only half of the Moon sees the light of the Sun. This fact alone reduces available surface for settlements to only half of the Moon.

While the Moon could be a temporary backup plan, in the long-term, you're going to need to terraform a planet and make a suitable atmosphere, both of which are not possible to do to the Moon.

Edit: Thanks to the commentators below who mentioned that while the Moon is tidally locked to the Earth, most of its surface does indeed receive light from the Sun.

Only one question though: If that is true, then why do they call it "the dark side of the Moon"? (Honest question)

> Only one question though: If that is true, then why do they call it "the dark side of the Moon"?

This doesn't refer to sunlight, it refers to radio communications. The back of the Moon, relative to Earth cannot receive any kind of signal we can send without some kind of artificial relay. Because the moon it tidally locked with the Earth the same side always faces us.

So the back side is always dark to our radio even though it has about a 28 earth long "day". Any (non-polar) spot on the Moon gets about 14 Earth days of light and then another 14 of darkness, corresponding with the phases of the moon we see here.

> Moreover, only half of the Moon sees the light of the Sun.

I'm no astronomer but the moon is tidally locked to the earth and not the sun, which means that the moon should have sunrises/sunsets...

Yeah, it does. The real concern is that the moon-day is a full month long and there is no atmosphere transferring heat; any permanent structures on the surface will get very very cold during those two weeks in the dark. If we don't solve this with suitable solar-charged batteries we would need multiple outposts -- say 4 of them dotted around the Moon -- with colonists rotating through the cities to stay in the Sun. But that's also kind of a non-starter because the distance between those cities is something akin to the distance between Denver and New York City -- it's not impossible but it's also a nontrivial drive to be doing every week just to remain in the sunshine.

Why not poles?

I'm glad you asked! So there's an important physics reason why the equator is warm and the North and South poles are cold on this planet, and it has to do with how you point a surface. If you ever find yourself in a dark office with a bright desk lamp (or maybe your home office or kid's bedroom might be suitable) you might even try this experiment: take a flat surface, a notepad or steno pad, and hold it up facing the light source, then slowly tilt it away and look at the color of the surface; you'll notice that it doesn't sharply transition from illuminated at 0 degrees to dark at 90 degrees -- instead it smoothly varies like the cosine of that angle.

This mathematical effect is incredibly important, it means that sunlight, during the day, averages out to being half as strong as its maximum over the whole of the Earth's surface. The calculation isn't even particularly difficult: the surface area of a sphere is well-known to be 4πr², half of that or 2πr² is illuminated at any one time, but the actual irradiation that we receive is proportional to the cross-section area, which is just the area of the circle: πr². So if the Sun-directly-overhead light were to be illuminating that entire half of the world, we would get k·2πr² light for some k, but instead we only get k·πr² light for that same k, so it works out to be 1/2 when averaged over the whole surface of the Earth.

While I was at university a fellow student asked me to guess the coldest place in the Solar System. I guessed "the middle of the dark side of Mercury." I guessed this for a couple reasons: (1) I knew I needed a rock without an atmosphere since atmospheres sustain convection currents that transmit energy, and (2) I figured since Mercury is so close to the Sun it's probably tidally locked to the Sun and therefore this part probably has not seen a speck of sunlight in millions of years.

It turns out that general relativity makes point #2 wrong and my friend gleefully informed me that he was looking at an article (there were many, so let's take [1] as representative) suggesting that it might be in a crater on the South pole of the Moon. This has basically the same reasoning of (1) and (2) above, except substituting the shadow of a crater for the shadow of tidal locking. But Mercury is still in the running -- the only issue is that we might not be looking at the dark side of it, but rather, again, at its poles.

[1] https://www.space.com/7311-moon-craters-coldest-place-solar-...

Mercury won't be under any serious consideration for habitation for a long time. It is down at the bottom of the biggest gravity well within a few light years. Too much delta-V to come or go. It is the least explored inner planet for a reason.

I think you are drastically overstating the difficulty of heating a lunar polar base. You are surrounded by vacuum, one of the best insulators around. It can be used.

Of course a lunar base would probably be underground (for more radiation protection) and the lunar soil would quickly wick heat away. Simple to deal with. Excavate a small cavern and suspend the base inside the cavern. Aluminize the cavern walls if possible. Now the colony has its own thermos bottle and staying warm is easy.

Sunlight is just as intense at the lunar poles as the equator. The ground receives less solar energy, but that doesn't mean that less energy is present. In fact there is more solar energy available at some sites since the panels could receive light continuously instead of in 28 day cycles. (Might require putting the panels up on a tower to help reduce libration shadows?)

A solar panel tower at the North Pole of the Moon might be a really good idea for solving these problems, yes.

Vacuum is only one of the best insulators around if you're near other warm things, I'm afraid. Out in space the dominant form of heat exchange is the Stefan-Boltzmann law, which says that if you have a half-acre of total surface area on your moon-base, and it's at 300 kelvin, then you need to supply about a megawatt to keep it warm.

It's not an insurmountable problem, of course -- Tesla just announced a battery for Australia at 129 MW-hrs, which would sustain the thing for 5 days, which is not enough but it's only a half-order of magnitude off. (I'm also not considering something like nuclear heating; it's not uncommon to have a 1000-megawatt nuclear reactor in the US and that's just the power output, not the heat -- so it's not a terribly bad way to go if you can shield the rest of the base from it. The only hazard with that is one recently discussed by John Oliver on his show, firing nuclear things into space is heavily, heavily complicated by the nowhere-near-close-enough-to-zero failure rate of launch rockets and the insanely-scary-cost of distributing a bunch of reactor-grade nuclear fuel into the atmosphere.)

I still think you are overstating things. Stefan-Boltzmann is just a fancy way to say radiation. That is more or less a solved problem with nested shells. Each layer of shell cuts the losses in half. But let's ignore that for now, since more than one layer of shell complicates construction.

Historical aside: before we had good solar panels, people tried crazy stuff like the Phaeton satellite that used a generator spun by a heat engine powered by liquid mercury heated by parabolic reflectors. Let's bring that idea back.

1MW only requires a 30 meter by 30 meter thermal solar collector. Pump that 1MW of heat into the hab and run a heat engine, using the shell of the hab as the thermal sink. Now that constant 1MW drain is a required feature.

That's a very interesting point, thank you for the explanation!

why general relativity makes mercury tidal locking wrong? I've heard it's not 1:1, but I don't see any connection

Actually looking into it a bit more to answer your question, I'm entirely confusing two different things. Mercury is tidally locked 3:2, it rotates 3 times for each 2 times it orbits -- but that is a result of history and not general-relativistic corrections, which are necessary to explain a different value (the precession of its orbit).

In fact our best understanding of why Mercury has the 3:2 relationship appears to be (if I'm reading these papers right) "because of historical reasons." That is, now that it's in that state, that state is stable and unlikely to decay to the 2:1 or 1:1 state, but getting into that state is much less clear and potentially requires that in the past, the other planets of the Solar system had nudged Mercury into a more eccentric orbit than it has now. The claim is that the eccentricity of that orbit caused the 3:2 resonance, then in more recent history these perturbations from other planets averaged out more to make Mercury's orbit less eccentric, but it still holds on to the resonance from its past.

Put a couple large mirrors in orbit around the moon.

So, why wouldn't a parabolic mirror in orbit that bounces the light down to solar arrays on the moonbase work?

>If that is true, then why do they call it "the dark side of the Moon"?

It's the side we can't see from Earth. It's dark as in unreachable by line of sight or light, eg radio communication, from Earth. "Far side of the moon" is the preferred term but "dark side" is popular and persists.

> Moreover, only half of the Moon sees the light of the Sun.

What do you mean by this? The moon is tidally locked to the Earth, but the entire surface sees sunlight over the course of ~a month with the exception of a handful of polar craters where small portions are perpetually in shadow.

Factually this is correct: only half of any planet in the solar system sees light of the Sun at any given moment. :)

Only with a literalist interpretation of said fact. :)

> Moreover, only half of the Moon sees the light of the Sun

That's not true. There is a side of the Moon that's always facing away from us on Earth but each side of the Moon actually gets about 2 weeks of sunlight followed by 2 weeks of darkness.

It's tidally locked, so you couldn't you put the settlement on the Earth-facing side and not have to worry as much about meteors?

Well, it's like holding a shield of a radius of only 6,371 km with an arm of 384,400 km long.

Or to put it in human terms, like holding a shield of 1.25 cm of radius with your arm of 75 cm.

It will not protect you really very much.

That seems to make sense, but if you look at the moon from Earth, you see an awful lot of craters...

I was thinking the same thing. Earth will shield the moon on the Earth-side, mostly.

Mars is immune to large meteors (actually asteroids)? When did this happen?

As others have said, a Moon's day lasts about an Earth's month.

There's hope for light most of the year at the poles: https://en.wikipedia.org/wiki/Peak_of_eternal_light

I used to fantasize about exploiting the temperature gradient between hemispheres for generating electricity on worlds with long days like Mercury and the Moon when I was a kid.

> then why do they call it "the dark side of the Moon"?

Because four billion wordwide population - all living - have a Computer God Containment Policy Brain Bank Brain, a real brain, in the Brain Bank Cities on the far side of the moon we never see.

This was last month. Another analysis this month by a different organization reached the opposite conclusion.

[1]: https://scripps.ucsd.edu/news/analysis-rusty-lunar-rock-sugg...

Lets hope they don't find oil there...

As you probably know, that's impossible since fossil fuels (as the name suggests) are formed from the remains of prehistoric organisms. Since the Moon is lifeless, it has no fossil fuels.

But I wouldn't mind if the moon did experience a resource rush (unless it sparked a conflict). At least we would finally get to see a moon base.

Fossil fuels are known as biogenic oils or the like.

It has been theorised, but neither proven nor disproven, that abiogenic oils might exist. (Earth is likely only the biogenic kind, but other planets may differ).

That is to say, petroleum compounds can be formed without the need for biological materials, but rather through pressure, heat, and bedrock.

If they did then it would essentially be proof of extraterrestrial life, no?

Non biological oil exist. It can't form on Earth since the algae completely change our atmosphere, but it can form in other celestial bodies.

It would be pretty useless there too, since there is no oxygen to burn it.

That would be incredible though

It would be quite difficult to burn oil without oxygen.

Unrelated to the article, but WOW did anyone else see the giant full view height ad video at the top? I have ad blocker off for NatGeo. It's followed by a giant banner. I can't imagine how much crazier ads have been getting and most of us don't even notice 'cause we have ad blocker.

I just got a new laptop and hadn't got around to installing uBlock yet. I'm comfortable saying the mainstream web is literally unusable without ad blocking. I watched the download notifications in the status bar iterate through dozens of ad servers, for 1-2 minutes, per page. I could barely scroll at all. I couldn't tell where the actual content was. All 3 columns full of ads. You have to hunt for isolated paragraphs of content.

The other glaring thing I noticed is the browser becomes a festering petri dish of promiscuous cookie-sharing. Every site obviously knows everything I'm doing on every other site.

> a festering petri dish of promiscuous cookie-sharing

Shouldn't that be impossible? What browser lets one site access another's cookies?

I mean tracking in general. I feel violated every time FB or Google reveal they clearly know where I've been recently.

Afaik, there may not be sharing across domains, but there surely is across pages.

Pixel tracking is trivial to implement.

> I can't imagine how much crazier ads have been getting

I would certainly argue the way this comment (and many others in a lot of threads about ads here or elsewhere) seems to imply that ads are at their worst ever.

I mean either people forgot or are too young to remember, but in the 2000's alone ads had both their "pop up and sound and unclosable javascript spam" and their "flash everywhere turning your modern supercomputer speed into that of a 80's calculator" eras, and probably a lot of other ad-cancers that my brain chose to forget. The entire reason the ios/flash debate happened was because 1 - flash was on every page and ad, 2 - flash was eating every resources you would throw at it and still need more.

I mean, I agree totally that the web without ad blockers is insane, but I think many also see how it used to be as much better than it actually was.

I remember those days. Back then I'd say 99.97% of those horrible ads you describe were on spam / bad websites. The normal, good sites that we went to every day had very, very tame ads. For the most part, as long as you visited reputable sites back then, the ads were not a big deal.

Today the reputable sites are an absolute mess with huge, bloated and completely unusable ads. So yes the ads back then on non-reputable sites were worse because of what the browser makers allowed websites to do but when you compare the reputable websites? There is no contest that today is far, far worse.

Remember pop-unders? I don't miss closing my browser and finding a dozen ads hiding under the window.

Of course in that time you had no tab indicator to nicely tell you who was playing sound.

Nothing quite like those search that took you on sketchy websites and their porn pop under blasting orgasmic noises in your home / office while you frantically try to find who does that (and then close everything because it's taking too long).

"The good old time", as they say.

Sound indicators ... that time? Like a year ago?

I understand your jest, but for reference by "that time" I referred to back when pop under were still a thing.

Searching for which tab makes sound is one thing, searching for it and not finding it anywhere because it's a pop under positioned at the bottom right of your screen is a whole other experience.

I was there, and I only started using ad blockers a couple of years ago. It is much, much, much worse now.

Different opinions then I guess.

I prefer a (collection of) ads that obfuscate the entire page I'm trying to read but doesn't bother me while I look at something else and happily let me close and go away than something that makes everything a hog and crash my browser randomly while I might not even see it because it's five tabs away in the footer of some website.

Ads were terrible, they continue to be terrible, they used to and still do provide most of the money needed to run sites, and it's still hard to get users to pay for content like articles on the internet. We still haven't solved these fundamental problems with funding quality content on the web. There are models that kinda work, but ads sadly seem to work the best in terms of giving everyone access "without paying", even though you're paying with your privacy, time, and eyeballs. Many people prefer this vs something like paywall games or subscription-only services.

I subscribe to a lot of sites and newspapers and they still show me their ads.

What's more amazing is that they never learn. As if blasting us with more and more ads that take over your entire browser. Will somehow put everyone at ease. The advertising industry is the next big reboot on the web as far as I'm concerned.

The advertising industry's policy seems to be that the well is infinitely deep, and therefore no amount of shitting into it is too much.

I'm not sure what you expect them to learn.

Only use "cleaner" ads ? It will pay less, ads don't pay much any more, you need the big, splashy, if-possible-exclusive-and-targeted ads to get money now.

Offer subscriptions ? They already do that, and they publish quality original content, so it's not the case of journal-X publishing the same press release as everyone and complaining that people don't subscribe.

At this point, they can only do two things with people who don't subscribe: block them from accessing content, thus losing lots of traffic and conversion possibilities, or show them intrusive ads, make a little money off of them, and hope a few subscribe.

One argument could be that "those ads are turning people off of subscribing and ultimately makes them lose money", but in every debate on this matter I have never seen it substantiated with actual numbers, and especially in the case of a household name like National Geographic I sincerely doubt it, at least not in any meaningful way.

People didn't start using ad blockers, because sites had a couple well placed ads. If everyone is blocking your ads, maybe it's time to change all those reasons you gave me for "how they work".

I think you misattributed or misundertood my intention here.

I am in now way arguing that those more and more terrible ads did not cause the surge in ad blocker usage, and what I said is not affected in any way by how many people are using ad blockers on NG.

Fact is, revenue per ad viewed has been crashing down for all type of ad.

A site like NG can either block their free access and force a subscribe (lose attention and name recognition), give it for free fully but remove incentive to subscribe (lose revenue), or change their ad type to more intrusive ad that pay more to compensate.

I'm sincerely open to discussion if you disagree, about what they could potentially do that isn't one of those three, but the revenue per ad viewed falling is not in their control, it's a global market trend since several years.

How about, beautiful, site specific, non-intrusive, relevant ads? Charge less if you have to. Enough with the Tabula bullshit, and Amazon selling me something I already purchased(why is this even a thing). You'd be surprised how many loyal people to a site would be willing to white list, knowing the advertising isn't going to shit on their experience.

If they continue down the current path, they are going to die one way or another. At some point the people working there are going to stop being proud of their work when it's presented in such a shit fashion and they will stop writing for NG.

I understand that business needs may require a publication to lower their standards but it seems like they have dropped below where the floor should be. When I load the page, there's a giant Microsoft video at the top of the screen. Microsoft should be ashamed of that as well.

Wow yeah I instantly hit "Back" and have now blacklisted national geographic. Seriously, national geographic? Thing's have gotten that bad I am now blocking NG? Sigh.

I liked grubbers dubbing of a "dickbar" but this kind of ad deserves its own moniker. PrickPage?

NatGeo was purchased by FOX recently, if that insight helps...

I don't know, I distinctly remember in the late 2000s there being all these insane "take over the entire page" flash ads for cars on sites like New York Times.

They are aggressive with ads because everyone is using ad blocker and no one clicks on ads. Content and infrastructure are not free. What do people expect to happen??

Maybe ads are getting more aggressive because we are all using ad blocker?

The inverse is also possible.



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