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[Sheb]

Not exactly news, but I only recently found out about it. Have you ever heard of Wolbachia? It's a genus of endocellular parasite bacterias that transmits vertically in the eggs of many invertebrates, from insects to nematodes.

The fun part is that it has devised a lots of way to take control of its host's reproductive life to increase its fitness, from killing all males offspring (they don't transmit the parasite) to turning male into females to preventing mating between infected and uninfected insects. In some case, you have different "species" that can create fertile hybrids after a course of antibiotics. In other case, wasps that were known to only reproduce by parthenogenesis started to produce male offspring after treatment with antibiotics.

It is totally fucking awesome, and making even more of a mess of the specie concept. This is rather old, but is a good summary of how awesome Wolbachia is. (Yes, there is plenty more)

[palsch]

It looks like people think that I am anti-science.

This is wrong. I am not anti-science. But I think the modern science is too disconnected from philosophy to make progress.

I think a lot of modern philosophers would disagree with you on this.


In any case, I don't understand what you think modern science should look like?

I mean, if you want to progress our understanding at all (and I'm going to assume that by not being anti-science you would accept this as a desirable goal) then we are going to need finer study of apparently inconsequential details of the universe. The reason being that our current understanding is as good as we can get with our current study of the crude and consequential, so to make any further discoveries we need to move away from the obvious.

The clearly constructive work is done in the obvious places, but new developments come from edge cases and the harder-to-find corners. The places that aren't immediately useful. So finding a precise mass for the Higgs Boson might not give us technology overnight, but it does offer a more refined framework to hang future models on.


If you are genuinely interested in philosophy of science then read up on some structural realism (less complete but more accessible, hopefully). It is* a fairly defensible model of both reality and science, and rather matches how scientists view historical and current models (in my experience at least).

Spoiler: * (click to show/hide)

Or rather, they are. There are different formulations ranging from the soft ("scientific theories tend to preserve gross structure even as our understanding of the reality underlying that structure changes") to the hard ("only structure exists, it is meaningless to speak of individual elements being real"). If I'm honest I don't know where I'd fall on that scale, but I'd say that 'truth' about reality and science falls somewhere on it.

[Descan]

If mitochondria were originally parasitic "bacteria" that became fused with eukaryotic cells, could there be some descendants of those mitochondria that didn't fuse still swimming around? And if so, would we even be able to recognize them as such...? :u

[10ebbor10]

If mitochondria were originally parasitic "bacteria" that became fused with eukaryotic cells, could there be some descendants of those mitochondria that didn't fuse still swimming around? And if so, would we even be able to recognize them as such...? :u

Yes, and we (might) have actually found them already. Genes encoded in mitochondrial Dna are surprisingly similar to Rickettsial bacteria.

Link

[Sheb]

Well, we can (and did) compare their DNAs to existing bacteria to place them in the bacterial taxonomy. Apparently, they're in the order Rickettsiales, which also contain Wolbachia.

From wiki:


Also, apparently some nematodes cannot survive without their Wolbachia. Those might be in the process of turning into fully-fledged organelles.

[martinuzz]

Question for the astrophysicists:

If hypothetically, one would want to cause apocalypse, by crashing the moon into the earth....

What would accomplish this most efficiently?

A) transferring mass from earth to the moon
B) transferring mass from the moon to earth
C) neither

[Il Palazzo]

What makes you think transferring mass would cause the two to crash into each other? That'd only change the location of the barycentre. For the two to crash, you need to bleed out most of the orbital angular momentum.

[Silfurdreki]

Question for the astrophysicists:

If hypothetically, one would want to cause apocalypse, by crashing the moon into the earth....

What would accomplish this most efficiently?

A) transferring mass from earth to the moon
B) transferring mass from the moon to earth
C) neither

Transferring mass from the Moon to the Earth. When you've transferred all of it, you've successfully crashed the Moon into the Earth!

Doing it the other way would have the Earth crash into the Moon, and we can't have that, can we now?

[Solifuge]

If hypothetically, one would want to cause apocalypse, by crashing the moon into the earth....

What would accomplish this most efficiently?

To do it efficiently, you'd need:

A) ...a sufficiently large object to collide retrograde (on an opposite trajectory) to the Moon's orbit, negating its orbital velocity enough to let Earth's gravity pull it in... and you'd probably end up liquefying or otherwise losing a good chunk of the Moon in the process. Wrangling the object to hit the Moon would also be tricky; to do it without costing a bunch of fuel, you'd need a combination of luck, and gravity assistance from other planets, most likely.

B) ...to cover it in rocket thrusters, with enough fuel to burn for billions of years and negate it's momentum as above. I... think you could just do retrograde thrusters on one half, due to tidal locking with Earth. I haven't done the math, but it would most likely take more fuel than Earth could ever produce, using current means. Maybe reliable antimatter harvesting from the magnetosphere would make it more feasible?

C) ...a spiky heart-shaped mask that grants you the power of a god. And no giants, or plucky time-travelling elves to oppose you.

[palsch]

Very crude first approximation;

The mutual attraction between the earth and moon is;

F = G M_E M_M / r²

For the sake of convenience I'm going to use non-standard units for force and acceleration, just so I can define G and r to be 1 and simplify the first equation to just be;

F = M_E M_M.

Acceleration of a body is just force over mass, so acceleration of the moon would be;

F/M_M = M_E

Completely independent of the mass of the moon. This is the gravitational acceleration at a given point. You can see this is similar for the earth. We are interested in the net acceleration, which is to say;

F/M_M + F/M_E = M_E + M_M

As you can see, any transfer of mass between the earth and moon will fail to change the net acceleration experienced. Any decrease in the acceleration of the moon would be compensated for by an increase in the acceleration of the earth, and vice versa.

It would, however, change the nature of the orbit somewhat. This is modelling the two objects as point masses. You could shake things up a bit (literally) by changing that and introducing other factors into the equation, but that's more maths than I feel like right now.

[10ebbor10]

Russia's BN-880 reactor went critical a few hours ago. Link.

It's a rather interesting Fast breeder reactor.

[Sheb]

Somehow "Reactor went critical" raise all kinds of red flags in my mind. :p Still, that's pretty cool. I wonder what's the cost vs. a standard reactor.

[palsch]

Somehow "Reactor went critical" raise all kinds of red flags in my mind. :p Still, that's pretty cool. I wonder what's the cost vs. a standard reactor.

I'm reading 15% more than VVER. Actually that whole section is interesting;

Construction is well advanced on Beloyarsk 4 which is the first BN-800 from OKBM Afrikantov, a new, more powerful (2100 MWt, 880 MWe) FBR, which is actually the same overall size and configuration as BN-600. It has improved features including fuel flexibility – U+Pu nitride, MOX, or metal, and with breeding ratio up to 1.3. The MOX is quoted as having 20-30% fissile isotopes.  However, during the plutonium disposition campaign it will be operated with a breeding ratio of less than one. It has much enhanced safety and improved economy - operating cost is expected to be only 15% more than VVER. It is capable of burning 1.7 tonnes of plutonium per year from dismantled weapons and will test the recycling of minor actinides in the fuel.

Russia expected to have 40 tonnes of separated plutonium stockpiled by 2010, and after some furnishes the initial core load, the rest was expected to be burned in the BN-800 by 2025. The timing of this has slipped about four years.

In 2009 two BN-800 reactors were sold to China. Construction is delayed from intender start in 2013.

OKBM Afrikantov in Zarechny is developing a BN-1200 reactor as a next step towards Generation IV designs. Rosenergoatom is ready to involve foreign specialists in its project, with India and China particularly mentioned. Rosatom's Science and Technology Council has approved the BN-1200 reactor for Beloyarsk, with plant operation from about 2020. It will be 2900 MW thermal at 550°C, giving 1220 MWe and 60-year life. Thermal efficiency is 42% gross, 39% net. Breeding ratio 1.2 initially with MOX fuel, later 1.35, and then 1.45 with nitride fuel. It will have 426 fuel assemblies and 174 radial blanket assemblies surrounded by 599 boron shielding assemblies. OKBM envisages about 11 GWe of such plants by 2030, possibly including South Urals NPP.

So they are basically intended to burn 40 tonnes of weapon-grade plutonium first, then start using it as an actual breeder. Sensible given some of the fears around such reactors is proliferation. The delays mentioned are recent delayed; the design was originally soviet planned but was abandoned with the collapse and then revised in the early 90's.

[scrdest]

Somehow "Reactor went critical" raise all kinds of red flags in my mind. :p Still, that's pretty cool. I wonder what's the cost vs. a standard reactor.

Actually IIRC a nuclear reactor going critical means that it started working. The Bad Thing is it going prompt-critical. Then again, I don't know shit, so I need someone to whale on me here.

[Sergarr]

Somehow "Reactor went critical" raise all kinds of red flags in my mind. :p Still, that's pretty cool. I wonder what's the cost vs. a standard reactor.

Actually IIRC a nuclear reactor going critical means that it started working. The Bad Thing is it going prompt-critical. Then again, I don't know shit, so I need someone to whale on me here.

I think it works that way.
I probably should know better about things like this, because I study in NRNU...