h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I spent longer than it deserved putting a response together and then the server ate it. Hate that, when you've got it all sussed out and something comes along and pisses on your fireworks.

Basically, which would you make provision for *first* if you had to choose; defence of the gravity well we're stuck in, or assurance we won't be extinct if it fails?

The problem we *do* have now, or the solution we *could be capable of having* in centuries. This was about the expense.

"Basically, which would you make provision for *first* if you had to choose; defence of the gravity well we're stuck in, or assurance we won't be extinct if it fails? "

As an engineer, I interpret the question this way:

Which is better: buying an expensive spare, or doing maintenance that will mean the spare may not be needed?

To which the answer is: analyse the consequences of failure. The more disastrous the consequences of failure, the better the justification for the more expensive course of action.

In the case under discussion, the consequence of failure is the extinction of our species. Hard to think of anything more disastrous than that. At which point, the price of securing a "spare" subset of the species elsewhere becomes almost irrelevant. We MUST do it.

SoRB

SoRB, I respect your analysis, but it seems like we're quibling over acceptable probability levels. You've stated that integrated over a long enough time period, the probability of an asteroid strike on the earth approaches one. I agree with this. But by the same logic, integrated over a long enough period of time, the probability of simultaneous asteroid strikes on both the Earth, Moon*, and Mars approaches 1. So using the "integrated-time" criteria, the Moon & Mars colonization just delay the problem further - they don't actually fundamentally solve it.

* - a single asteroid strike on the Earth could be enough to disrupt/destroy a Moon colony.


Also, here are some fundamental problems we are no where near solving.
1) How do astronauts survive the zero-G environment for the time period required to get to Mars?
2) How do astronauts survive the high levels of radiation they will be exposed to on their trip to Mars?
3) Will astronauts be able to successfully shelter in lead coffins during solar flares whilst en route to Mars?

I'm proposing that these are engineering problems, but that we don't have the fundamental science we need to begin approaching them. There are massive advances in our knowledge of biology and medicine which might allow us to heal/prevent these problems, but right now we don't have those.

Up until quite recently i was a strong defender of nasa and the space program , I too can remember as a small boy being woken up in the middle of the night , plonked in front of an an old b/w tv set and told to " watch this there going to the moon" as an imposibly huge saturn v rocket left the launch pad . I can see in my minds eye the huge bulk of the rocket sliding ever upward past the screen , the sheets of ice falling away as the rocket shook them off , the letter 'U' , more ice more rocket , 'S' more ice more rocket , 'A'. I can even now be quite emotional about it all .
But now ? I cant help thinking that all the expertise at nasa would be better employed trying to solve some very pressing problems we have here on the mother ship {earth} .
50 years before the first commercial sized fusion power station . FIFTY YEARS ! are they having a laugh or what ? We need these things in 15 not 50 .
At the begining of the 60's president Kennedy promised to put man on the moon by the end of the decade . Not because it was the aesy thing to do but because it was the hard thing to do . And they succeded , hats off to the Americans .
I believe we need some of that zietgist now .

best fishes......tod

"SoRB, I respect your analysis, but it seems like we're quibling over acceptable probability levels."

Well, yes, that's the whole essence of the argument. That, and the general human inability to actually understand probabilities.

"You've stated that integrated over a long enough time period, the probability of an asteroid strike on the earth approaches one."

Assuming by "asteroid" you just mean "big enough thing to wipe out most large life", i.e. include comets etc., then yeah.

Understand also that in this context, "long enough time period" is a time up to around 100 million years or so.

"I agree with this."

Good.

"But by the same logic, integrated over a long enough period of time, the probability of simultaneous asteroid strikes on both the Earth, Moon*, and Mars approaches 1."

No, that's NOT the case. Simultaneous strikes are MUCH less likely, so unlikely in fact that the expansion of the sun due to hydrogen depletion is a more pressing problem.

"So using the "integrated-time" criteria, the Moon & Mars colonization just delay the problem further"

True. But they *probably* delay it so far into the future that we need to be considering inter*stellar* colonisation to avoid the effects of the sun's lifecycle.

SoRB

If you're taking the non-asteroid-related destruction of earth into account (e.g. sun failing or going supernova), and this leads to a non-unity value for the time integrated probability of simultaneous extinction level asteroid strikes on Mars and the Earth, then you need to take this into account for the single asteroid strike on Earth.

I'll take your word on the time scale, so let's ignore the possibility of the destruction of the Sun as a possibly occuring before a single asteroid strike.

For example, a gamma ray burst could occur close enough to us, and aimed directly at the earth, such that all life on earth is annihilated. This would be analogous to your argument, and hence the time-integrated probability of a single asteroid strike would not be one (by the same logic you employed).


On another tangent, let P*dt be the probability of an extinction-level asteroid strike on Earth at any instant of time. Then the probability of an extinction level asteroid strike occuring within a time interval T is given by the integral
Integral(P*dt) with limits 0,T

For us, the time interval is (for example) the end of the Sun. So the total probability that an extinction level asteroid strike will occur before the death of the sun is
T*P

where T is the time remaining until the sun dies. Now, T is constantly decreasing (a la death clock), therefore the total probability of an extinction level asteroid strike occurring before the death of the sun is always decreasing. Therefore, as time passes, the importance we place on averting species extinction by the asteroid collision is continually decreasing.

Given this information, why start on the project to diversify to Mars now, given that the probability of the asteroid strike occuring will be reduced before we even finish the project, without us having to have done anything?

Your argument is sound mathematically, but if you actually do the sums you can see why although the *logic* underpinning it is sound, it doesn't actually change what you should do.

"If you're taking the non-asteroid-related destruction of earth into account (e.g. sun failing or going supernova)"

There are three basic mechanisms by which this planet may be rendered uninhabitable by natural means:

1. Impact by object - comet, asteroid, whatever. Known to have occurred relatively frequently in the geologic past at intervals of tens or hundreds of millions of years, with none for about 65 millions years. Therefore virtually certain to occur within the relatively near future, i.e. within 10 million years, and possibly (although not necessarily probably) within 50 years.

2. Star lifecycle - solar expansion due to hydrogen depletion. Absolutely certain. Will not occur for *billions* of years, however.

3. Extra-solar catastrophe - supernova or similar in stellar neighbourhood. This possibility can be ignored because there's (a) no way to predict it and (b) no way to avoid it. If it happens, we're gone, and there's nothing we can do about it. So that leaves (1) and (2).

"let's ignore the possibility of the destruction of the Sun as a possibly occuring before a single asteroid strike."

Wise.

"For example, a gamma ray burst could occur close enough to us, and aimed directly at the earth, such that all life on earth is annihilated."

As I say - there's nothing we can do about that. If it happens, everything for dozens or hundreds of light years around will die. There is no realistic possibility of avoiding it any time in the next 1,000 years, barring functioning warp drive. But let's not get silly...

"T is constantly decreasing (a la death clock), therefore the total probability of an extinction level asteroid strike occurring before the death of the sun is always decreasing."

Well... yes. But by how much?

"Therefore, as time passes, the importance we place on averting species extinction by the asteroid collision is continually decreasing."

Also true.

"Given this information, why start on the project to diversify to Mars now, given that the probability of the asteroid strike occuring will be reduced before we even finish the project, without us having to have done anything?"

Let's say you built a house.

I do a survey of the area, and tell you that on any given day, there's a 1 in 100 chance of a massive but very localised earthquake destroying your house and killing you and all your family. So basically, over the course of a year, the odds are 3:1 on. It's going to happen. It could happen tomorrow, or next week, or next year, but it's happened at regular intervals before and it's pretty certain to happen again. It happened to a house down the street only last week, but you didn't take the hint.

You *could* spend a LOT of money buying another house down the street, so that if either of them gets hit with a quake, at least some of your family survive. It's expensive, but it's your *family*, right?

Now, I *also* tell you that in 70 years' time, there will be a volcanic eruption which will destroy your house completely, and not only your house, but all the houses nearby and anywhere you can reasonably expect to be able to buy one. No odds on this, it's GOING to happen, definitely, just not for 20 years.

So your kids look up to you and say "Daddy... are you going to buy us another home so at least some of us can grow up?".

And using your logic, you say "No, kids, because it will take me a couple of days to save up the money, and by the time I've done that, we'll be two days closer to the volcanic eruption that will kill you all anyway in 70 years, so what's the point?"

And the kids look depressed. "Plus," you add, "I can't save up for a new house, because I need to spend the money right now on repairing the roof of this one."

And at this point your kids beat you to death.



The point is that there are orders of magnitude of difference between the timescale of likely object-impact extinction events, and the timescale of the certain solar-lifecycle extinction event. IF we manage to survive the coming impact events, it's likely that by the time of the solar-lifecycle event we'll have populations outside the solar system, whether in FTL ships or generation ships.

What this is all coming round to is, we DO need to invest as soon as possible in getting the hell off this planet and starting self-sustaining colonies elsewhere. The fact that, in ten *billion* years time, those colonies will eventually perish shouldn't stop us aiming for them. We'll need them sooner than that, guaranteed.

SoRB

Well there went my contribution. Fascinating stuff though

Therefore virtually certain to occur within the relatively near future, i.e. within 10 million years, and possibly (although not necessarily probably) within 50 years."

How is this not the gambler's fallacy? Random event hasn't happened recently in the past, so we're "due up" for it to occur soon?

Whilst struggling to keep up with the swapping of math lessons, I confess to being more intrigued with SoRB's dedication to species salvation.

At first I was tempted to put it down to fascination with Star Trek, or Battlestar Galactica, but as he expounds his argument I see that it is a genuine belief that mankind should achieve space travel.

I could accept the 'desirability' of building the necessary technology -if it were not likely to swallow the GDP of all the developed economies, but I simply cannot see it being accomplished on the scale SoRB envisages.

That then begs the question "who should go?" and perhaps why? Earlier I slipped in question as to why mankind should be saved at all. After all we have seen many 'civilsations' come and go here on the Blue Planet, and we are not doing very well at the moment in terms of justification of salvation.

Perhaps sometime between the next 50 and 1,000,000 years ,when the rock hits,it is our time to go...........

Novo

"How is this not the gambler's fallacy? Random event hasn't happened recently in the past, so we're "due up" for it to occur soon?"

I didn't and wouldn't say we're "due up" for it to occur soon.

I'm drawing the distinction between two events: solar lifecycle extinction, and rock impact extinction.

The first DEFINITELY WILL happen, at a more or less predictable time in the very, very, very far future - ten *billion* years, or thereabouts - and DEFINITELY WILL NOT happen any sooner.

The second is 99.999999% certain to happen before that, fairly likely to happen in the next ten million years or so, but - and this is the important point - there's a small but finite probability that it will happen IN MY LIFETIME.

I come back to my point that I believe we have a limited window of opportunity to avoid this fate. I believe that, if we do not achieve sustainable self-sufficient colonies offworld within the next two or three centuries, we never will, and the species is doomed. If we DO achieve it, then barring unpreventable occurences such as a nearby supernova, the species could conceivably be immortal. Which surely should be our aspiration.

I wonder how much of my belief in this stuff is related to the fact that I neither have nor want children...

Wanting to survive is probably justification enough. The way you put it novo, suggests a divine mandate we'd be interfering with by trying to ( do *not* go there).

I have a moment's reprieve - I'm no mathematician but I got from the link I gave earlier that of 156 predicted to approach Earth to within 2 million km in the next 200 years, 19 could pass within the range of the moon's orbit, and 5 are determined most likely so to do.

Whatever the legitimacy of expecting Apocalypse Soon, we have plenty of tables on which to place our chips, and no notion of the size of the casino.

Can I just say that SoRB's 'Window of opportunity' is the most cogent argument for manned space exploration I have heard. Anyone (with more knowledge than I) care to rebutt it?

Chris (cannot reproduce the pwer of two!)

I didn't mean to imply a divine mandate. Sorry if that's the impression created.

I was merely thinking that in terms of the entire universe, and its possible contents, does a warlike species such as ours have the right to expect infinite longevity?

We ourselves have exterminated a few species on this planet. Do we expect the opoertunity to take that supremacy attitude to places where no man has been.....?

Just a speculation that as a species, we may not be immortal.

Novo

"does a warlike species such as ours have the right to expect infinite longevity?"

How about "does the only known intelligent species in the cosmos have the right to attempt to escape possible extinction."

Letting the only creatures in the known Universe capable of sentient thought die as payback for a handful of Dodos doesn't seem like a good plan by anyone's standards.

Hi Psycorp603

I wasn't suggesting any sort of plan, acceptance of the inevitable included.

And what makes you think that 'we' are the only creatures in the 'known' universe that are sentient?

Do you know ,or suspect something that the rest of us don't?

I come at this with SoRB's wish to see it happen. About 40 yers ago I built my own 6" reflecting telescope ( mirror grinding and all), and marvelled at the universe in the night skies over East Anglia.

I have no illusions about our sentience, nor about our feeling of self importance. I simply beg the question that it is our inheritance. Incidentally I absolutely do not believe we are the only sentient beings in the entire universe.

Novo

"And what makes you think that 'we' are the only creatures in the 'known' universe that are sentient?"

Beause in the bits of the Universe we know, we haven't found intelligent life. We might, we might not. If they're there, they're in a bit we don't know. Do you know something we don't? Little green men under your bed perhaps? Or have you been on a flying saucer?

"I absolutely do not believe we are the only sentient beings in the entire universe."

Chances are that we aren't. We're still the only one we know about though, and there's still a possibility (however slim) that intelligent life (or just life in general) is just a total unrepeatable fluke.

Even if the spontaneous appearance of intelligent life hasnt been repeated in the vastnes of the universe doesnt mean it is *unrepeatable*

Who knows evolution might even give us another dodo if it has happened once it *can* happen again.

M a few pages into a bok called "the End of Science" one of the ideas in it is that we ave become decadent and self destructive because there is nothing much left for us to do. Too much of our effort is frittered on self destructive violence or polluting the planet by producing and powering gadgets that we dont need.

Maybe reaching for the stars would be a better use of our time than the things we are up to at the moment? Perhaps not killing ourselves so quickly is a better reason for getting out there than hedging our bets against destruction by asteroid impact?

one love

"Even if the spontaneous appearance of intelligent life hasnt been repeated in the vastnes of the universe doesnt mean it is *unrepeatable* "

If you look my last post, you'll find I didn't say that it IS unrepeatable, just that it COULD BE.