Re: 95 per cent of the components on each satellite will burn up
I've always assumed the other 5% is propellant expended during in orbit station keeping ... i.e. Krypton.
32 posts • joined 21 Jun 2009
You've got that the wrong way around. We ARE apes, and primates. Specifically humans belong to the group "great apes" along with Chimpanzees, Bonobos, Gorillas and Orangutans. All great apes are primates, not all primates are apes though... primates include all the other monkeys and lemurs.
Yes, and the oxidant used to deal with the unburnt fuel in petrol engines exhaust stream is... drum roll please ... NOx. Diesels can't use the same catalyst tech as they are sub stoichiometric in the fuel air ratio used, and thus only produce Nox and soot, not unburned HC. The rhodium based cat needs the H in the HC's, so doesn't deal with the soot as it is nearly pure C.
The problem is not with indows signature validation though is it?
The issue, as I see it (& please correct me if I am wrong), is a developers signature credentials (private key, or password for same, and the cert) have been knicked and now are in the hands of malware authors, without the certificate authorities revoking the certificate.
normal = 6ft+ does it? erm, no.
The average man in England is apparently 5'9" whilst the average woman is 5'3" (see http://www.bbc.co.uk/news/uk-11534042 which references an ONS report from 2010)
Unless of course you are Dutch, as the Netherlands is one of the few countries where the average height of a man is now over 6ft.
Indeed I thought the main reason the brakes and the steering on cars are only ever "electronically assisted" was the very simple design regulation of "fail safe", i.e. if your alternator fails (can happen) and the battery subsequently *completely* discharges (running the cars electronics, head lights, stereo etc) you can still steer and stop because the controls are mechanically linked to the actuators at the wheels (by cable, hydraulics, rack & pinion, whatever).
[the throttle on the other hand these days is often entirely electric, the pedal is just connected to a rheostat or similar]
The reason fly-by-wire is acceptable in aviation and not domestic automobiles is the regulation of maintenance of the vehicles, i.e. cars are maintained by the cheapest grease monkey you can find or not at all.
"IBM says that the amount of yammering and bickering about steampunk has increased by a factor of eleven in the past three years"
Given the growth of twitter, facebok, social media and the general cloud of tw@ts that inhabits them, could this statement not be true about almost anything at all... such as "the amount of bickering and yammering about creationism has increased eleven fold over the last three years"... doesn't mean I'm going to buy an iPhone case with a picture of Adam, Eve and a "friendly" dinosaur on it anytime soon.
Me too... it's perfectly feasible for heavy rain to be more common and leave the annual total unchanged. That is if you get your annual rainfall in half a dozen deluges rather than 200 instances of drizzle, heavy rainfall has become more common. If you are going to attack the Met Office for "getting it wrong" please use a better argument than that.
Frankly I think the money spent on the Met Office is well spent. Remember climate science is not all they do. Their short range forecasts are very good and allow me to cycle to work most days in confidence that I won't get rained on the way home nine or ten hours later.
I expect most of the commenters here would have the Met Office burned as witches if they were spot on anyway.
the problems are
- purifying water to the required degree of purity (accuracy), even dissolved gases (oxygen, nitrogen and others are all soluble in it to varying degrees) will affect the density of the water.
- 1 litre of water doesn't have a mass of 1 kg (density at 4 Celcius is 0.99997 g/ml, this is at it's densest)
- the density of water varies with both temperature & pressure
It's a nice idea but utterly unworkable in practice.
Re: "True but I think you'll find this is actually well below the active size, which IIRC is around the 50-70 micrometre size, rather than nanometre size"...
Yeah, that's why I enclosed the "nano" in quotes, although PM10's are alledgedly quite dangerous too ... and that's particles in the sub 10 micron range (think diesel exhaust, without a particulate trap).
You did read the bit where it is described they used molybdenum oxides to modify the graphene?
It won't end up as "just", carbon dioxide, methane etc after breakdown. You'll still have molybdenum oxides in there. The safety sheet for molybdenum trioxide includes phrases like "do not breathe dust" and "limited evidence of carcinogenic effects". There are a great many "molybdenum oxides" to choose from though, unfortunately they are often very complex structurally and effectively mixed valence (as opposed to the simple trioxide & dioxide). That might explain the obseved improvements in electron mobility, as the complex moly oxides can act as both an electron donor and an acceptor.
Like all complex materials disposal will be likely be a bitch, if only due to the (quite possibly trace) heavy metals used to get the electronic properties just right. Also any dust with just the right "nano" size is harmful to the lungs; whether the particles are inert or not.
... but no, the powers that be have actually killed it. I'll file this change alongside the all the other UI freakery of late, like Metro/Modern/Notro (whatever the $%^&* it's called this week).
Ho Hum. Is there a special "retro" section where us luddites can go to get the "Most Commented" whilst we are moaning about the rise of mechanical weaving looms?
ok... so you got a potential of 2.4v and sustained it for six hours? The vital missing piece of information here is the *current* of that discharge (if they just wired a volt meter to it we are talking about micro-amps). As in how many amp hours did they store in the battery? I expect the energy density they got was somewhat less than a commercial battery (given the compromises they'd have to make to make it paintable) and the volume is by definition low as it's just a layer of paint.
The key question is how long could you run a smart phone (or other useful device) from a painted battery? and how big an area would you need to paint? If it turns out you need an area the size of parachute to get useful quanties of stored energy it's a whole lot less exciting...
Never mind the techniques apparent sensitivity to such mundane substances as air or water.
Still keep working on it...
standard batteries (of the sort invented by Volta more than a hundred years ago) rely on the transfer of electrons between two different metals through an electrically conductive solution ... if you used two steel plates the voltage you'd experience between them would be zero.
If you used a copper plate and zinc plate you get a bit more than one volt, if you're sticking them in the ground then the ground water will be your electrolyte... if you want to go around contaminating ground water in this manner (the more reactive of the two metals dissolves in the electrolyte during discharge) be my guest just don't come running to me when the Environment Agency come after you.
yep you are pretty much right... although the "proton" is effectively covalently bound to a single water molecule forming H3O+, this is in turn merely hydrogen bonded to an inner circle of three (via the three H's, to form "H9O4+"), and they in turn are H-bonded to another six H2O's, forming as you say a species of formula H21O10+ (no super or sub scripts in plain text, but you get the gist). However the inner three and the outer six are only hydrogen bonded to the inner H3O+ which is by standard convention actually a single molecule, not an aggregation of ten molecules that is only transiently stable; the outer six are so weakly bound they exchange with molecules in the bulk quite rapidly.
Finally most of these arguments are fairly moot as the extra H+ in H3O+ (I know I've simplified again) can hop from one H2O to the next, thereby leading to ion transport speeds in aqueous solution that far exceed what would be expected if something as large as H9O4+ or H21O10+ were trying to move about (this is also true of OH- too).
Still thumbs up for making me remember the rest of it.
but that 2% excess CO2 emission has increased the atmospheric concentration of CO2 from ~280ppm to ~380ppm. An increase of about 35%.
The CO2 in the atmosphere is in equilibrium with the CO2 dissolved in the oceans. That is a 35% uptick in atmospheric CO2 will eventually lead to a similar uptick in CO2 concentration in the ocean (it's far from saturated in this regard, it's not a fizzy drink yet). However this step is lagging, it takes time for the CO2 concentration of the ocean bulk to even out, quite a lot of it is more than a mile from the surface.
In turn the dissolved CO2 is also in reversible equilibrium (by reaction with water) with carbonic acid (H2O + CO2 <-> H2CO3). Pushing in more CO2 drives the equilibrium over to the H2CO3 side. H2CO3 is acidic (weakly), in that it disassociates into "free protons"* and bicarbonate.
pH is the negative logarithm of "free proton"* concentration... so increasing atmospheric CO2 inevitably leads to the pH of sea water decreasing, that is acidification (by definition, frankly).
* I'm forced to point out at this point that "free protons" do not exist in even very acidic water solutions. Assuming they exist is a gross simplification. The acidic species in aqueous solution is actually H3O+, that is the acidic proton attaches itself to a near by water molecule.
"73 per cent felt the data they got was accurate"
but that's all you get, a feeling. At the end of the day you can't search the internet youself, you can only compare Google's results against the rest. And only then if you can be bothered.
I imagine a more telling statistic would be what percentage of users use more than one search engine for a given query to even allow objective comparisons to be made. I expect that number to be close to zero.
ok... admittedly some of this is sourced from wikipedia (so take it with a pinch of "bloke down the pub said"), the earth's inventory of nuclear fuel is supposedly worth 2.5 YJ of energy, that's 2.5 x 10^24 J. Which if I've got my maths right is ~700 million TWh; or at a rate of 5000TWh/year is 138 thousand years worth. I think we can consume it a tad faster than that. ;-)
NB: Thorium is much more abundant than Uranium, and could (again *supposedly*, it's a wiki fact) last hundreds of years (or more). Giving plenty of time to sort out fusion.
Then there's geothermal. That isn't sun derived either. This is already producing 67TWh every year, and that's just the low hanging fruit (like Iceland and the other hot spots).
I'm willing to concede that even geothermal & nuclear are at least partially "sun derived" if you count the supernova that formed all the nuclei heavier than Iron in the first place, and geothermal heat is a mixture radioactive decay heat from early in the earth's history and gravitational potential converted to heat from the earth's formation.
but I've often felt the rise of NoSQL, in particular columnar databases and key/value object stores, is also related to the use (over use) of automated development strategies, namely auto written ORM/DataAccess layers. These will find much better performance when storing a serialized object in a key/value store as opposed to storing each field nicely in it's own typed column. Some systems I've seen have hugely terrible performance when using RDBMS's as the back end store because they effectively issue trillions of single row selects as they build up the objects to satisfy a multirow "query", when they *could* have leveraged the SQL language to get the same job done directly against the RDBMS, but for whatever reason didn't.
I'm not sure that the correct fix for such perf and throughput issues is rejecting the relational paradigm... perhaps the data access layer needs to be more intelligently written with respect to set based operations.
Or perhaps I'm a dinosaur who hates change?
the RTG is powered by the thermal energy released in the radioactive decay of Pu-238, which has a half life of 87 years or so. So in 87 years the thermal power of the RTG reduces by half. However the RTG's electrical power generation is not dependent on the thermal power of the heat source in the business end... but on temperature difference between it and it's heat sink (the heat sink is effectively cooled by the inky cold blackness of space). The rate of heat loss to the environment by black body radiation (the primary mechanism in a vacuum) is proportional to the fourth power of the temperature (Stefan-Boltzmann law). This is applicable because the hot end will not *only* be cooled by the RTG transferring heat to it's heat sink but by radiating energy directly into space (this is unavoidable, no insulation is perfect).
What this means is that the electrical power available from a thermo electric RTG falls away more steeply than the half life of the radio isotope used would naively suggest. (i.e. after less than one half life, 35 years is 0.4 half lives, the thermal power of the Pu-238 should be ~76% of what it was at launch, but the RTG is only now putting out 60% of launch power).
Now I'm sure all you gadget fans realise that a) gadgets consume juice, and b) heaters consume lots of juice. Therefore to manage the dwindling energy budget on the probe the NASA engineers have to gradually turn stuff off.
Plus I expect the reduced temperature difference in the RTG has reduced the voltage available too... this will further impair the probes ability to power it's gadgets.
Still a great effort from these wonderful probes... they'll likely outlast the civilization that built them (they'll be shutdown by then but still).
I take your point, these CTE's based on data modification statements that return data *could* be useful... . However I wasn't criticising CTE's.
What I was objecting to was the authors statement of "the only other way to perform this task is...", where he then went on to describe possibly the most stupid way of transferring data between tables short of cut'n'pasting data and storing it in Excel prior to "uploading" it back to the database.
Quote "Under normal circumstances, such an operation would require someone to use a database client to access the database table, select the data, download it to their client, delete that data, then upload it manually into the second table."
Seriously? does the author even understand the products that he's talking about?
How about this (excuse the lack of error handling, but you get the picture)
INSERT INTO TableB (ColA, ColB) SELECT ColA, ColB FROM TableA WHERE ColC = ?;
DELETE FROM TableA WHERE ColC = ?;
No data transfer to the client required... The only network traffic required here is sending the statements down the wire and receiving the appropriate success/fail code and optionally the number of rows affected.
"While no-one can completely defend against such sustained and concentrated malicious attacks ... "
if it was SQL injection, then yes you can completely defend against "little bobby tables" and all his "insert into dns..." chums.
Unless of couse it wan't SQL injection in the deeply orthodox sense.
so you'd attempt a landing on a surface where local gravity gives your craft a weight of 2750 Newtons* but your main engine is only capable of 0.1N* of thrust?
To land at say 0mph (locally stationary) you'd need an engine capable of equalling the local gravitatonal attraction... or ~27,500 times more powerful.
I'd hazard it would hit Vesta with a fair old thump (i.e. a crippling impact) if it attempted a landing.
* I've revised the weight and thrust figures to appropriate units of force (newtons) from the units of mass (grams) at a rate of 10N/kg (approx the acceleration due to gravity at the earhth's surface) ... as I consider this the appropriate rate, and it's easier maths than 9.8N/Kg
I'll get me coat cos I'm obviously taking it too seriously
"... Depending on what article you read, between 600,000 and 1m people were tasked with cleaning up and preventing a much worse disaster immediately after the initial incident. Many of them suffered huge radiation doses..."
so a *million* people were involved in clearing up Chernobyl? This doesn't quite sound credible to me.
Correct me if I make a mistake or an incorrect assumption but my thought process goes like this:- Chernobyl is in Ukraine (and I know it was Soviet Republic at the time, but bear with me) which has 32 million people aged 16-64 (I'm making an assumption that it's population hasn't changed in twenty years... it's currently slowly declining, like much of western europe). Belorus the other nearby country (ex Soviet Repulic) is approximately one third the size and has a working age population of 6.9 million. I'm assuming that the elderly and children would not be involved and that people would not be bought in from further afield (and therefore the population of the Ukraine itself can be used a reasonable estimate of the population of a similarly sized area centred on Chernobyl/Prypiat).
This means that what you are trying to tell me is that 3.1% of the working population of the country was involved in the clean up. If you assume that only men of working age are involved then it rises to 6.5% of men in the entire Ukraine (that's just less than one in fifteen). If you notice that the population density of Belorus is actually lower than Ukraine, you require even higher proportions of working age men to be involved (as our guess at the population of a Ukraine sized chunk of the USSR goes down as we include chunks of Belorus instead of the furthest parts of Ukraine).
Sorry, I don't buy it. If you'd put it at a hundred thousand I might have beleived you without thinking about it much, but a million? That number would count as an Extraordinary Claim.
over a billion (or so) years the moon has contracted by 0.005% (if I'm to beleive the previous posters)... could this not be simply explained by the moon cooling down? that is simple thermal shrinkage - no black holes, no clangers, no NASA conspiracy, just simple GCSE level physics
just a thought.
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