33 posts • joined Thursday 17th September 2009 20:46 GMT
Re: Acceptable losses?
If the asteroid was disintegrated far enough way some of the fragments would surely miss. A suitably placed explosion would give the fragments extra momentum in all sorts of directions. If the extra momentum were perpendicular to the main track, the fragments would be on a different trajectory, if the extra momentum were along the main track the fragments would reach the Earth impact point sooner or later than the Earth and miss. Of course a lot of fragments and dust would still hit earth but a lot would also miss - unless I'm missing something.
I read the other day that comet C/2013 A1 (possibly up 50km in radius) may impact a planet late next year. This was officially discovered in January 2013 which doesn't give much time to do something about it. Fortunately its heading for Mars not Earth - and just because its well out of the ecliptic plane we've only just noticed it. This doesn't give me much confidence in present threat discovery..
How reliable are the figures?
A quick Google revealed a large number of "check your broadband speed sites".
So I decided to try them. It's about 1015 and I'm in suburban Wolverhampton. Here's successive download speeds from 10 different measurement sites.
36.7, 53.0, 29.3, 57.6, 39.1, 18.1, 62.1, 56.1, 60.6, 60.0
Virgin media are supposed to provide 60 Mbd so not too many complaints but the variations suggest that either speeds can widely over a short time scale or that some of the measuring tools are not too accurate. In either case I think we ought to know more about the methodology behind the report.
Upload speeds were consistently in the range 2.7-2.9 Mbd.
In many cases they never started dreaming let alone have stopped.
In 1993 I started using WWW and thought it rather amazing, I'd already been using the Internet's anonymous FTP archives extensively (remember Archie?), the potential was pretty obvious - but trying to persuade university brass to back development of our own resources was another matter. They were more interested in the possibilities of training people to use Microsoft Office.
In 1993 I already had a home computer and home Internet seemed an obvious development. Whether I'd have anticipated a 60 Mb permanently on home connection is another matter.
Re: And it's actually *programmable*
Used to programme this machine back in the 1960's.
The relays are used to decode instructions and set up the required data paths, basic addition and subtraction are purely electronic limited in speed by the switching speed of the cold cathode decatrons. The electronic parts of the addition process took about 30-40 mS + extra for carry cycles. Multiplication used "shift-and-add" - a bit like long multiplication - and required relay intervention to set up the shifted data paths, the operation was so slow you could actually see the partial products build up. Division was similar although the need to count the number of operations made it even slower. The (shifted) divisor was repeatedly subtracted from the dividend until a sign change was detected, it was then added back once and new cycle of subtractions started with an increased shift - again it was possible to watch the quotient being built up.
Incidentally division by zero was a particular problem as the repeated subtraction of zero never resulted in a sign change. If this happened a "watch dog" circuit noted that no new instructions had been read in for some time and, depending on the setting of a control switch, either blew a hooter or shut the machine down.
Addition and subtraction took place directly between memory locations, multiplication and division proceeded via a special memory location called the accumulator.
The dekatrons are visual and it is possible to stand in front of the machine and determine the contents of any memory location by the simple expedient of looking at it. An excellent feature for the introductory programming courses held at Wolverhampton.
Programmes were normally read from paper tape, each instruction being read from tape before execution, this operation contributed significantly to the slowness of the machine. If you wanted a programme loop you need to make the tape into a physical loop using a paste-pot. There was also a technique for incorporating something called a "block number" in amongst the orders on the tape, this functioned in exactly the same way as a label in a more modern programming language.The original "Gloy" paste pot I used in the 1960's was still in the spares box when the machine moved to Bletchley Park!
It was also possible to store instructions in memory (like a modern computer) but with only 90 memory locations this was rarely done. It was actually slower to read instructions from memory than it was to read them from paper tape. [Not quite sure why].
There were further problems with loops, the mechanical readers are rather heavy handed and after several passes had a tendency to poke extra holes in the tape. Solutions included the use of, expensive, linen based paper tape and repeating the "loop body" multiple times on a larger physical tape. I remember one large loop that was routed round an Anglepoise lamp on the other side of the room.
The most interesting task I programmed on this machine was a key (as in door key) design programme for a local firm of lock and key manufacturers [Messrs Chubb]. The problem was that on a mortice key (the sort with sticking pieces of metal called wards) only certain combinations of ward length were valid, a single ward sticking up above its neighbours would be weak, adjacent wards of the same height were a security problem etc.. Along with another schoolboy (I was let off school for a day a week to use the WITCH) we programmed the WITCH to print out all the valid combinations.
Like all machines of its period, the WITCH had what can only be called "presence", a wall of flashing lights, clacking relays, clattering tape readers and the slightly asthmatic whirr of the output printer springing into life.
Remembering the state the machine was in when it reached Bletchley Park, the fact that it has been restored without any significant replacements is a tribute to both the original designers and the restoration team.
Attending the re-boot ceremony I was given a lapel name badge that described me as "Wolverhampton WITCH", I'm keeping it for Halloween!
A version of the Difference Engine has been built out of Meccano (so much for engineering tolerances),
Perhaps the analytical engine team should consider .....................
Re: There's an opportunity here
Would those be metric pints by any chance?
Re: You'll fit right in
On my first visit to Germany a few years ago, I flew into Dusseldorf to catch a train to Essen. DeutscheBahn did their best to make me feel at home, producing a train that was slow, dirty and late. The Ruhr river looked like a country brook. Essen was fascinating, practically every building in the city centre had been destroyed by allied bombing during the (don't mention), except for Mr. Krupp's factory which they'd somehow missed and had since been converted into a branch of Ikea. Wandering around the city on Saturday afternoon (all the shops closed at 4 o'clock) I found myself looking at a row of little Swastikas and pictures of Adolf Hitler - I thought the philatelist's shop could have chosen it's window display more carefully.
BAE - is that British Aerospace Engineering? A British company manufacturing computers, that can't be right surely?
Re: Slightly OT
Skylon gets as much speed as it can whilst still in the atmosphere to take advantage of "free" atmospheric fuel oxidant and then goes up to clear the resistance of the reminder of the atmosphere. The animation shows the early part of the climb to orbit which would be nearly vertical just like the climb to orbit of a conventional rocket.
Incidentally I am puzzled by one aspect of the animation. Skylon is shown travelling east-to-west over Capri, Southern Italy and Sicily. I thought west-to-east orbits were energetically preferable.
Re: Defeating the object.
Hmm. Yes there's an awful lot of hydrogen about, but on this planet, you need energy to separate it from other elements, usually oxygen, where is that coming from - an oil-fired power station perhaps? Hydrogen gas also has a low energy density per unit volume - certainly compared with petroleum - so hydrogen powered vehicles need either huge gas bags, weighty compressed hydrogen cylinders or expensive cryogenic systems.
Hear! hear! - but
So you have the right to exploit, the right to extort, the right to misuse the law to your own advantage ...... I find it worrying that so often discussion of rights seem to revolve around what I, as an individual, can do. A duty to consider and care for others less fortunate than oneself is surely every bit as important a part of the human condition as the rights we seem so happy to claim.
When I was younger, we here in England often saw the USA as a big hearted generous open innovative society if a bit vulgar. Alas no more.
What has that got to do with the Internet? Not a lot - but remember that the development of the Internet protocols (TCP etc.,) was funded by the US government who then, apparently, told Berkeley that they couldn't charge for what they'd developed because the tax payers had already paid for it and they shouldn't have to pay twice. I leave it readers to imagine what would happen today.
To be followed by the telephone sanitisers and advertising account executives .......
Great news that the future of Bletchley Park is now more secure.
But I hope restoration and conservation doesn't alter the overwhelming slightly "down-at-heel" 1940's period flavour of the place. Anybody at all interested in the history of computing should make every effort to visit it, and allow a full day.
I also hope the relationship between the National Museum of Computing and the Bletchley Park Trust can be clarified to the benefit of all concerned.
I particularly enjoy going to see the first computer I ever programmed on display rather than hidden and forgotten in a dusty museum store. They've even got a photograph of me standing in front of it 1961 - that's half a century ago.
Slightly off-topic, does anybody know why the movie "Enigma" which was set at Bletchley Park wasn't shot on location?
Oh happy memories. My first escape from mainframes, Cobol and Fortran
(and ICL's George 3) was Unix V6, PDP/11's and C, happy hours reading the source
code and eventually fixing two bugs in the kernel source. Gosh I could
read the source code of an operating system - and understand it!
So our solar system was originally like many other recently discovered
solar systems with a gas giant close to the star. What caused the disruption
that ejected the gas giant and re-arranged the solar system in its present
life-friendly form? Was it a likely event or something rare and improbable?
I suppose the most likely cause was another star passing close to the solar
system, I've no idea how likely this would be but I imagine most such close
encounters would not result in re-arranging the solar system into a life
friendly form. It is remarkable that after the disruption the solar system
settled into nice stable nearly circular orbits. It also suggests that the inner
planets were not necessarily formed at their current distance from the sun.
Coupled with the need for the "late heavy bombardment" to fill Earth's oceans
the "rare Earth" point of view looks even more convincing.
Distance on the surface of the Earth ~ 732Km
Straight line distance through the Earth ~ 731.24Km
[Maximum depth is about 10.5 Km assuming smooth
Earth.]That's a difference of ~760m. The quoted 60 nS
difference corresponds to about 18m path length
"The Difference Engine" is a great read.
For a factual account Tom Standage's "Victorian Internet"  is also well worth a read.
Digital store and forward communications networks - just like the Internet -
in the 18th (yes 18th) century.
Now just let's get things straight.
The Enigma supplied by the Poles was an early version which none the less provided clear insight into how it operated. That alone was not enough to decrypt Enigma messages. You also needed to know various initial settings which changed on a frequent (daily) basis. The genius of BP was in building machines and procedures for recovering the settings on a regular basis.
The U110 recovery was of the more complex naval Enigma machine, significantly different from
that the Poles had in the 1930's. As well as recovering this machine, vital code books (giving initial settings) were also recovered from U110.
The Colossus proto-computers, of course, had nothing to do with Enigma.
Robert Harris's fictional account "Enigma" gives a good feel of BP and the cracking of Naval Enigma. The movie "Enigma" was, to me, a bit of a disappointment and why wasn't it shot on location at BP?
I also am known by my second Christian name. This caused considerable confusion when work place acquired a clever 'phone system with an extension/user database populated from the staff list. I used to regularly receive 'phone calls asking for "John" - my first Christian name.
To add to the complications I also have three Christian names and I have known systems that address me as Mr. <first Christian name> <third Christian name>.
Too many people making assumptions rather than doing some serious leg work researching the options when designing systems using names. It would be nice if some national or professional agency could give general advice to coders on the ground on such issues, even nicer if they could get it right.
And Strauss's "Blue Danube Waltz" as background music for the orbital rendezvous?
FOSS needs support
About 3 years ago the company where I work part-time wanted a new e-mail system but didn't have any funds for it. An old PC, SuSE Linux and the Courier mail package later they had such a system - which had over 2 years continuous up time until we had a power outage that exceeded the capacity of the UPS. It is also compatible with and integrated with MS Active Directory for user authentication. Support has consisted entirely of adding things that weren't in the original request - such as automatic "sig" addition, archived mail recovery and automatic enrolling of new staff in role-specific group aliases.
Well what was the problem?
To quote from elsewhere on the Register a "real time data dissemination issue". Of course it isn't easy to know exactly what this piece of gobbledegook means but it sounds like either a low
level driver problem, a protocol problem or possibly a clock synchronisation problem unless anybody has any further insights. These are not easy things to detect during testing especially if the testing was as badly conducted as some of the posts seem to indicate.
At Uni I used to tell students that "if two people can interpret a (communications) protocol differently, they will" and practical work quickly confirmed this.
As an aside a previous poster referred to the LSE web site, according to Netcraft this runs Linux and is hosted in Italy.
And what is that frayed wire dangling from the ceiling (oops sorry no ups and downs in space) above the happy astronaut? There is a serious risk that, in the weightless conditions of space, the astronaut could accidentally float into it.
And the Greeks had problems .....
The ancient Greeks knew how to build steam engines - but why
bother when you've got slaves to do the work? The Anitkythera
mechanism seems to have been a toy for the amusement of
nobility rather than a practical device for the everyday world of
commerce and trade. The Greeks were also
stymied by an unbelievably clumsy way of writing numbers.
And the military dictatorship that was Rome had little time for anything
that wasn't immediately practical.
None of these problems were related to their religious beliefs however.
It should be noticed by those who enjoy knocking the effect of religion
on scientific development that modern science was born and grew up
in a very specifically Christian environment. This may be a pure
coincidence of course.
Since this collection didn't reach it's ridiculous reserve does BP get to keep Google's $100K and use it for something useful?
Is Turing that important a figure in the history of computing anyway? He wrote academic papers on the principles of computability and could reasonably be described as a founding father of what is now called computer science. The honours, however, must go to the many early engineers who struggled with unfamiliar concepts and technology at its limits to make the earliest computers possible. They were more concerned with getting the machines to do basic arithmetic reliably and usefully than with the theoretical limits of computability. It is to them that the title "founding fathers of computing" should go.
"The Colossus does not count"
The reason that the Colossus does not count as the world's oldest working computer
is simply that the machine on display at Bletchley Park is only about 10 years old.
There are other replicas and rebuilds of early machines around such as
the Manchester Baby, the Atanasoff machine and the Zeus Z3, the WITCH
however is original and is, AFAIK, the 3rd oldest surviving computer, the
oldest being Australia's CSIRAC and the 2nd oldest the Pilot ACE in the
London Science Museum.
The main problem with decatrons was comparatively slow switching, the ones used in WITCH are HivAC GC10B's - they glow purple - some high speed (and high voltage) ones are used in the multiplication and division unit, these have a pinkish glow.
It was a most impressive sight at night !
A really neat side effect of the use of decatrons was that you could see exactly what number was in every memory location simply by standing in front of the machine and looking at it -
great for programme debugging.
You could also stand in front of the multiplication/division unit and watch it doing long multiplication and long division step by step.
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