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Comment Re:Thought Experiment (Score 1) 165

I was out walking today through a forest that was originally planted

Was it used for that purpose? The fact that it's still there suggests not.

I carefully used the word "originally" when I originally wrote that. Not because I expected your response, but it suffices.

You seem to be thinking that the trees I was walking amongst were the ones that were planted in the 1300s? No - they had been harvested one at a time, according to their individual shape and size and the lumber needed for a particular ship, from around 200 to 450 years after planting. In each gap left by each harvested tree, others were planted according to the needs of that century while continuing to serve the needs of centuries past. That century's trees were local use as the re-forestation efforts of the 14th century had relieved the military's shortages, and changed ship building techniques reduced the need for particular shapes of lumber. Without the drive of legislation, the new plantings were changed from oak to the more useful (locally) ash and elm. At least, that's what the owner's tax and payment records tell the historians. Those smaller trees were managed by "coppicing" (check your local forester's dialect for their word) with the trees in a continuous state of replenishment from then until the woodland fell out of use in the early 1900s. (There are a few dozen larger uncoppiced trees ; no one knows why they were treated differently. But they change the ecology of the forest considerably.)

Most (not all, "most") coppiced broadleaved forests in the country were grubbed out and replaced with imported conifer species for clear-felling on a 1-2 century cycle during the last century, particularly in the immediate aftermath of the great pit-prop crisis of Word War 1. Which is precisely why this particular piece of woodland was saved from being grubbed out in the early 1970s (for arable, not forestry ; meh), to be used instead as a nature reserve. Then we had the nightmare of Dutch Elm Disease, which I grew up fighting to control in that wood, and which has now been replaced as a bogey-man by Ash Dieback. Fortunately, since we have a range of tree species in the wood, we can lose any one species without losing the woodland as a whole. That's judgement, not luck.

Forest management is a lot more complex than "see it, fell it, move on to the next mountain". Particularly if you don't have a next mountain to move on to.

Comment Re: Lots of children have the wrong DNA. (Score 1) 241

It seemes very reasonable to suggest that

any concept supported by claims as strong as "It seemes very reasonable to suggest that ..." is screaming out to be tested, because if there's one thing we know about people, it's that people are very good at fooling other people. That is why the professions of "confidence trickster" and "politician" exist.

Where I'd look for data would be cases where the volition of the (putative) parents isn't involved in selecting the children to be tested - when checking siblings (cousins, IIRC going further out isn't much better than random chance) as organ or particularly bone marrow donors for a victim.

Good luck getting your proposal to access such data past the ethics committee.

Comment Re:Sail Problems (Score 1) 165

In either case, the solar wind and the sun's gravity can alter the trajectory of the sails.

The influence of other star's gravity is calculable. (Unless there's something gravitating and dark out there.) The influence of interstellar winds ... is a fair question. So you send your first few probes off to see how they behave. It's not as if they'll contain anything you're more emotionaly attached to than some bits of wiring and (maybe) an AI.

The Oort cloud also requires consideration. If the sails are not punctured by the particles in the Oort cloud, impacts of those particles on the sails will decelerate them.

In the days before the first probes to Jupiter, exactly the same concerns were raised about going through the Asteroid Belt. We've not had a probe damaged out of - is it about a dozen that have gone through? We have every reason to expect the Oort Cloud to be more diffuse. In either case, suck it and see. Send probes out. Once you've built the lunching lasers (or while you're building them), the incremental cost of each launch is going to be pretty small.

If the sails are punctured, they will become useless in decelerating the sensors when the target star is approached.

They don't work like wind sails. Yes, you'd lose some efficiency. The triangle bounded by the three nearest shroud anchor points would limit the damage. A factor to include in your sail design, certainly. But not a show-stopper.

Comment Re:Quantum entanglement (Score 1) 165

we can send one every week

Well, not quite. You're constrained by the efficiency of your reflector, the maximum temperature your (electronics, mirror coatings, sail, shrouds, whatever is the most temperature-sensitive component of your actual vehicle design) can stand, and your launch laser. So you fire the laser until the probe has the velocity you can dispose of at the destination (which is what this paper is about), then leave it to fly. Re-point laser and launch again. You might not get one launched a week, but several a year is probably feasible. By the time they're flying past Eris, they're probably at cruising speed already.

Comment Re:Its pretty important... (Score 1) 306

Agreed, but when the water comes up, they'll have to deal with it - either through construction or relocation or both.

Let's say that tomorrow, scientists make a huge discovery that completely changes the climate models. It turns out that not only is mankind not responsible for climate change, but it is indeed fluctuations in the sun. How does this change our mitigation efforts? The answer is that it does not. Either way, we have to respond to higher water levels and a warming climate.

Comment Re:Thought Experiment (Score 2) 165

The missions being envisioned here are for small robots that can be accelerated and decelerated with reasonably foreseeable technologies

No. The only forces being modelled for deceleration in the target systems are those of light pressure and gravity - which we can calculate from the light flux (observed at Earth), the range (parallax), and orbital mechanics.

Once someone has a design for a probe (mass, sail area, reflectivity) then the analysis can be re-done to calculate the travel times (and important things, like how much ahead of the proper motion of the target object you have to aim. to hit the target) with your actual device. This analysis compared travel times for otherwise identical probes dispatched to different targets, and an optimal course strategy for getting there quickest and slowing down to orbital speeds at the far end. There are a few other constraints (e.g., a maximum probe temperature of 100C / 373K, to allow plausible electronics to survive) which could be revisited with an actual "release to manufacturing" design, but this paper provides a road map for how to optimise the trajectory once you get to that point.

Comment Re:Thought Experiment (Score 2) 165

the time frame isn't useful, the data wouldn't be obtained in our lifetime, and then what?

Coincidentally, I was out walking today through a forest that was originally planted in the 1300s, in order to provide timber for the anticipated navy of the 1600s. Even though the people who planted the trees wouldn't see them grow to a usable size.

Lordy! - they must have been superhumans, those Mediaeval foresters. Able to think centuries ahead, where modern people just cannot do that any more.

Comment Re:Thought Experiment (Score 1) 165

we aren't going to travel between the stars until we figure out something a whole lot better than chemical rockets and probably FTL drive...

And just where did anyone involved with this make any suggestion that it involved any human - or even any mammal - ever reaching another star system? I as sure as hell didn't see that, and I did read the fucking paper.

It is a moot point (cue grammar Nazis who think that it's "mute") whether a VonNeumann robot with the pinnacle of 22nd century software counts as a human descendent. But that's potentially enough for "human-sourced machines" to distribute themselves across the galaxy before the Earth becomes uninhabitable. But that may not involve actual humans.

As for it being a planning optimisation study - well, yeah, it is. There are no designs for even getting any data back from this sort of mission. But for any mission that is powered from the Solar System by projected beams, the same considerations of travel time will apply, even if the actual mission takes 3 centuries rather than their theoretical 75+46 years.

Comment All those little changes add up... (Score 3, Insightful) 371

...and they usually add up to a giant, steaming pile of crap.

I worked on a project once that did its best to implement all user requests in its product. By the time I started working on it, there were at least seven different ways to do any basic function, because different users thought it would be great if they each had their own way of doing the same damn thing.

The result? The software was bloated, and damned near impossible to adequately test. The permutations possible to do the exact same task were staggering. This resulted in a lot of weird bugs that weren't found during testing. It made the software brittle, and in the end the same users that wanted all these different ways of doing the same task (multiplied by a few dozen different tasks I might add) weren't happy with the resulting complexity. All that stuff that users thought would be simple and a good idea, in combination, sucked.

Sometimes it's a developers job to say no. It can be very difficult to decide when that time is, but projects that never say no are doomed to failure. Sometimes an over-arching vision as to how the product should work needs to win out over every single good idea some random user has.

I sometimes work with physical tools. And there are times when I'm using a wrench, but need to put it down and start using a hammer. I don't think it's unreasonable of the tool manufacturer to reject it when I suggest to them it would be great if they welded a hammer to all of their wrenches so I didn't have to put one tool down to use the other.


Comment Re:Could be useful (Score 1) 90

That kind of thing has been around forever - in the early 90s my college ran their computer lab with dual partitions on the hard drives: a write protected system partition and a user partition that was cleared every night.

But Chromebooks are still easier to manage - if they turn on at all, you know they are good to go. No set up at all, no drive images, nothing - just turn it on and go.

Comment Re:Its pretty important... (Score 1) 306

The climate will reach a point-of-no-return where no amount of mitigation will ever fix it. Ever.

I really don't know what you mean. The coastline will change, people will have to be moved or the coastline will have to be fortified. That is mitigation. Current farmland will become marginal and marginal farmland will become fertile. Moving stuff around is mitigation. It's not even really a choice - mitigation just has to happen so that people can go on living.

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