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Journal Journal: Vos nescitis quicquam...

vos nescitis quicquam, nec cogitatis quia expedit nobis ut unus moriatur homo pro populo et non tota gens pereat here.

Biblical, "You do not realize that it is better for you that one man die for the people than that the whole nation perish." John 11:50 (spoken by an antagonist.)

Comment Re:Ok, how many more are there? (Score 3, Interesting) 234

The question "are these sufficiently different to be two species" is inherently a fuzzy one. We tend to be a bit more picky when dealing with our near relatives, so we might call these a different species when for two squirrel groups with a similar level of difference we might call them subspecies. I've seen it argued that an objective taxonomist would put humans, chimps and gorillas all in the same genus, we've classified this lineage into four - gorilla, pan, homo and (extinct) austalopithecus.

Comment Re:Fascinating! (Score 3, Informative) 234

Can we sequence DNA from them? Probably, but not certainly. Ancient DNA is a very tricky business. The preservation of DNA depends a lot on the conditions they've been in since death. Cold and dry is ideal. I know we've sequenced DNA over 30,000 years old, I'm not sure what the record is.

Ancient human DNA is even trickier. If you're dealing with ancient bison DNA, you can largely avoid contamination problems by keeping the remains away from any modern bison. Keeping your human remains (and DNA samples extracted from them) away from modern humans isn't so easy. In this case, the cat is already out of the bag - the samples have been exposed to modern human DNA for decades. All is not lost, but it makes the job harder, and the outcome more open to doubt.

Can we clone them? Absolutely not with current technology. We can't clone a cow from a fresh steak, yet alone 10,000 year old bones. It is conceivable that future technology would allow it. I don't think you'll ever get it past an ethics committee though.

Comment Re:Do microlensing surveys this? (Score 1) 244

The fine article says that this result is extrapolated from microlensing survey results.

I have a peripheral connection with MOA myself. Phil Yock was my MSc cosupervisor (pre-MOA) and later I travelled to the telescope and helped with some setup, mostly of the computers. I also told them that I didn't think using "sleep 30" to control the exposure time was a good idea.

Comment Re:You want to stop at this dwarf star? (Score 1) 244

If the planet is travelling at more than the escape speed from the galaxy, it won't be in the galaxy any more. If it travelling at less than this escape speed and your ship is travelling at the same speed, you're taking at least a couple of thousand years to get to the nearest star. (And this is all before considering the chances of finding such a fortuitously placed planet.)

(Orbital speed of the sun around galactic center = approx 220 km/s, on approx circular orbit. Escape velocity = sqrt(2)*circular orbit velocity = 310 km/s. 310km/s approx = speed of light/1000, which implies 4200 years to travel 4.2 light years. Actually, it is a little better than this: this formula assumes all the mass is inside the orbit of the sun. Accounting for the galactic mass outside the solar orbit will raise the escape velocity somewhat. But then you need to consider the planets velocity relative to the sun, which means we need to subtract a 220 km/s vector off its galaxy-centric velocity, and that will decrease the relative speed, because it has to be travelling vaguely parallel to the sun's motion to be of any use at all.)

Comment Re:You want to stop at this dwarf star? (Score 1) 244

This was my thought too. If you're going to reach the alpha Centauri system in under a thousand years, you need to be going faster than 1200 km/s. How do they propose to refuel from something they're passing at 1200 km/s? The alternative -- expending fuel to slow down, refuel, then expend fuel to get back to speed -- is more than a little self defeating.

Comment A computer game idea (Score 4, Interesting) 479

Quantum mechanics, special relativity and general relativity are all very hard to learn, in part because they are so counterintuitive. Imagine a computer game which throws you into a universe where SR (or quantum mechanics or GR) have large, easily measurable effects - e.g. the speed of light is about 50m/s. After you've spent enough time zipping around on your relativistic motorcycle shooting zombies (or whatever), you should be able to intuitively understand SR, and the mathematics will become easy. (Well, as easy as Newtonian physics, anyhow.)

Comment Cost/benefit (Score 4, Insightful) 652

It isn't the number of people that die that determines whether it is worthwhile, it is the cost/benefit ratio. Fortunately, TFA provides some of the needed information, but it doesn't seem very consistent.
"But regulators say that 95 to 112 deaths and as many as 8,374 injuries could be avoided each year by eliminating the wide blind spot behind a vehicle." (Compared to the 200/17000 numbers, it looks like they believe the cameras will about halve the number of accidents.)
"...regulators predicted that adding the cameras and viewing screens will cost the auto industry as much as $2.7 billion a year, or $160 to $200 a vehicle." Wikipedia says 5.5 million vehicles sold in USA in 2009. (I presume this is new sales only.) This would imply about $500 per vehicle to reach $2.7 billion.
"For the 2012 model year, 45 percent of vehicles offer a rearview camera as standard equipment." Is that 45% of vehicles sold, or 45% of models? If 45% of vehicles, then only 55% are going to have extra cost if the cameras are required.

Optimistic cost/benefit ratio: 112 deaths prevented per year, 55% of 5.5 million vehicles at $160 per vehicle = 484 million dollars per year = $4.3 million dollars to save one life and 75 injuries. (75=8374/112)
Pessimistic cost/benefit ratio: 95 deaths prevented per year at a cost of $2.7 billion per year = $28 million to save one life and a bunch of injuries.

(Note that the cost is up-front, but the benefit is spread out over the ~10 year lifetime of the vehicle, which makes the investment a little less attractive, but I'm not trying to account for this.)

Comment Re:Both sexes are valuable (Score 3, Insightful) 248

Lack of recombination is generally a Bad Thing, hence no other asymmetric pairs. So the questions are why does the X-Y system lead to asymmetry, and why do we have X-Y rather than a system which allows full symmetry (e.g. temperature dependent sex determination, as in many reptiles)?
    While I'm sure it has been thought about, I don't know the answer to the first question. It seems quite viable to have a single sex determining gene (SRY in nearly all mammals) but still have full symmetry and recombination everywhere except in the middle of that particular gene. One possibility is that faulty male-specific genes (other than SRY) would not be selected against so strongly, as half the time they are in a female where the fault has no effect. With asymmetry this is not the case, so long as the gene has migrated to the Y chromosome.
    The answer to the second question might simply be contingency of history: if we evolved from temperature-dependent sex determination, but became live-young-bearing-with-regulated-temperature, clearly a new sex determination method is needed, and maybe X-Y (or W-Z) was easier to evolve to than some other environmental selection method. It isn't hard to see how a gene affecting the threshold temperature in a temperature-dependent system could mutate into an XY or WZ system.

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