Posts by mad physicist Fiona
14 posts • joined Wednesday 14th March 2012 01:15 GMT
Re: Excuse me?
Even state-owned universities in the US get most of their income from tuition fees, endowments and alumni. Very little state subsidy - it's anti free market, you know. What there is tends to be in the form of grants for specific research projects in the same way as many companies sponsor research.
Re: Sounds like Nemesis all over again
No, as I said, do the sums. That is all that is needed for a parallax measurement of a single star. According to the Tycho-2 catalogue here there are 5,227,058 stars between 9th and 12th magnitude. That makes 10,454,116 observations which is obviously a very small needle in a very large haystack.
Look at the list of nearby stars - they were generally detected not by parallax but by proper motion, and parallax only then used to measure the distance to the star in question, i.e. once it had already been identified. The problem with Nemesis is that it would have the same proper motion as our own solar system, and therefore not moving with respect to us, save for a very small orbital movement which to all intents and purposes looks the same as a much more distant star.
As for the detection of that brown dwarf recently that is precisely what I alluded to in my earlier post: you can detect those "easily" by looking for a bright IR source with no corresponding visible source. You can't do that for stars on the main sequence.
Re: Sounds like Nemesis all over again
Both red and brown dwarves have been proposed at different points. The brown dwarf alternative is increasingly difficult to defend since infra-red sky surveys should have picked it up by now. The red dwarf alternative is much more difficult to dismiss since a nearby red dwarf to all intents and purposes looks identical to a much more distant red giant. To distinguish between them needs full spectroscopy of each candidate star individually, which is both costly and time consuming.
The magnitude range for a red dwarf has been estimated at between 9 and 12. That covers millions of stars. You can dismiss a lot of those immediately because they are the wrong overall colour (i.e. not red) but it still leaves you with tens to hundreds of thousands of possible candidates.
Re: Why did nobody found out that Enigma was cracked
There was an awful lot of double-bluff going on. Letting Coventry be bombed to bits was the most notable one but there were plenty of others: One tactic was to thoroughly depth-charge an area of sea that was presumed to be empty. This had the the effect of a) suggesting faulty intelligence at work and b) the co-ordinates so bombed, which they made sure it was within sight of German intelligence, could be used as a fresh crib to break a new day's codes.
Sounds like Nemesis all over again
A lot of people have been very dismissive of the Nemesis hypothesis over the years but personally I've always found it unlikely, but been unwilling to entirely rule it out. You do the sums and a red dwarf could in fact be very close by, but next to impossible to distinguish from all the other background stars.
Re: That's naughty...
The SDK and kernel are two separate bodies of code. The what the kernel's licence says is a complete irrelevance to the licensing of something else.
Posted in The new Mac mini eviscerated with ease
Re: Oh dear...
I've just given you another one. If you'd read the comments you'd have seen someone had found the exact device around an hour after this went up. It's an ethernet transformer. You don't get a thumbs up for going to the Delta website and plumping for the first thing mentioned on the front page with a "that's close enough" attitude.
Re: Security @RICHTO
Actually NT 3.x was a relatively pure microkernel system with external device drivers. It was only with NT 4.0 that the video driver was moved back into the kernel to boost performance.
Re: DSLR for planetry imaging
The CCD cells are on a 4.3µm pitch but they are binned for movie mode - you only get 1080p resolution. Have a nice time enjoying those three pixel images.
Re: DSLR for planetry imaging
I was one of the thumbs down. I didn't comment at the time simply because I couldn't be bothered to go through the sums to show why.
DSLRs _are_ completely unsuited to planetary imaging. It isn't just the lack of movie mode on many models - sensor size is an equally important factor that is endemic to the format.
Since we're talking about the Canon 550D consider that it uses a 22.3mm sensor. This is a comparatively large sensor that is great for photographers since it reduces the cropping factor, but is a positive disadvantage in this application. The pixels are arranged on a 13.8µm pitch. A prime focus image of Ganymede at opposition (the most favourable time) is 25µm diameter even at the relatively generous 2400mm focal length of a Celestron C11. That makes a prime focus image area of less than 3 pixels. No amount of post processing can do anything with such limited information - even calculating the Strehl ratios (the first stage of the staking process) is more speculation than concrete mathematics.
Compare with one of the webcam derived imagers such as the NexImage 5 with a pixel pitch of 2.2µm. That gives you an image area of 101 pixels. That's enough for the stackers to begin working profitably with the data collected. The effective resolution can then be boosted by perhaps a factor of 10 or more as a side effect of the stacking process, depending on how many images you have to work with.
In practice however, you'd want to use eyepiece projection on both imagers rather than prime focus to get a decent resolution in the first place. Not a problem with the small sensors of the webcam imagers but if you extend the image over the much greater area of the DSLR sensors the curvature of the focal plane is magnified and completely takes over. The CCD sensor is flat, but the resulting focal "plane" is not. As a consequence only a portion of the image can be in focus at any given focus setting.
The OP's comments do not suggest a suggestion of appropriate tools based on knowledge and experience, but a case of techno-lust - looking around for relatively high-end equipment and assuming it must be exceptional regardless of the circumstances. I wouldn't knock that camera for wide field work, but it is a patently ridiculous suggestion for something like this.
Posted in Russia plans manned moon shot by 2030
Re: The race to the moon started when?
There was no race to the Moon. After they had men in orbit the Russians looked at their next goals and decided against a manned mission to the Moon. It is only American propanga that portrays a "race" to the Moon - a race with precisely one competitor. A race which ultimately led nowhere - it was 40 years since they were last there, they couldn't go there today and haven't been anywhere else since.
In contrast ventures such as the ISS would have been completely impossible if it was not for decades of Russian experience and expertise developed on their own space station programme.
Re: Whoever designs system that have changable clocks will always have problems
No, it is not me that has missed the point: if you define an internal representation in terms of a monotonic counter that is no longer UTC, even if the epoch is defined in terms of UTC: that simply calibrates the meaning of the counter against the real world: it is _not_ itself UTC and immune to this kind of snafu. Windows uses such a monotonic timer internally, not UTC. Nothing uses UTC, at least you haven't given an example of a system that does yet.
Re: Re cortezcortez
Sorry, but you can't simply make up constitutional law like that. They are nothing to do with the UK and Westminster has absolutely NO powers over them. The only connection is as the nam implies through the crown, not Westminster.
It's always a good idea to ensure you yourself have a basic grasp of the facts before accusing others of ignorance and pontificating.
Re: Whoever designs system that have changable clocks will always have problems
"Storing and processing in UTC removes >99% of the complexity."
You've obviously never done any of this work. How does defining everything to UTC solve the problem of six different units in customary use - seven if you include the week (which you need to to accomodate daylight savings)? Determining a time offset from UTC or any other time zone is a matter of one extra term in an expression referring to a lookup table. Add automatic detemination of daylight savings and you are still only looking at a dozen or so lines of code.
Compare that dozen lines to the amount needed simply to deal with all those units. Leap years and leap seconds notwithstanding, months are still not the same length, and yes handling leap years alone (yet alone leap seconds) takes vastly more than that 0.1 line of code that is allowed for in your 99% assertion. An assertion now shown as the ignorant crap it really is, to the extent that you have demonstrated that not only do you not understand the problem, but fail to grasp even its dimensions.
As a final case in point: how many systems actually deal in UTC internally? I'll give you a clue - it isn't ALL "real" systems, in fact I can't think of any more recent than MS-DOS. Windows doesn't and Unix certainly doesn't, both use simple synthetic escalating timers of the nature suggested by Refined Chap. They convert to natural units as and when needed. What do you know that the designers of those systems don't? Or more realistically, what did they realise based on factors that you haven't even considered?
