When I suggested that I might switch to TelstraClear Cable Internet because of faster upload speeds and a much snappier web experience
If you like somewhere that you have that choice then you're very lucky. And you should do it. The 4 Mbps down/2 Mbps up service is the best value in internet in NZ today, assuming that you a) actually do use the internet, and b) aren't leeching things 24/7. Get the $50 10 GB/month plan if you're going to use anywhere between 6.7 GB and 16.7 GB a month. And note that that is the *total* cost -- there's no hidden cost in having to have a $35/month phone line as well before you can even order broadband, as is the case with Telecom's DSL.
Or if you're one of those strange people who actually wants to have a landline then TelstraClear only add on $20/month for that, so compared to Telecom you're effectively getting the internet for $35 or so.
The US is not the whole world. Here in New Zealand there are about as many manual transmission cars as automatics, and the only reason that there are so many automatics (there weren't in the quite recent past) is that about 50% of newly registered cars are in fact used cars from Japan (becuase they are *cheap*), which are almost invariably automatic.
Automatics have an advantage in places where you get stuck in stop/start traffic jams. Japan and the cities in the USA are like that. NZ isn't. Automatics have definite disadvantages on hilly or twisty roads, especially with smaller or more highly-tuned engines. NZ is like that. The USA mostly isn't. And most cars in NZ are 2000cc or less.
And I've used the same $1000 monitor and $300 Cambridge Soundworks speakers on my last three desktop Macs. Those are external, moveable, replaceable components on *all* computers. So how does that support a "PCs are more upgradable" argument, exactly?
Hell, you could take your monitor and speakers and hard disk from your PC and use them on a Mac Mini (or any other Mac, including an iMac or PowerBook).
I saw one of the Mac commercials talking about how Macs work out-of-the-box, and thinking about what happens when you want to upgrade.
This "you can upgrade a PC" thing is rubbish. I've always been a Mac guy but I wanted to play with Linux so I built a Pentium66 machine. Then I upgraded to a Pentium Pro 200, then to an Athlon 700, then to an Athlon 3200, and now to a Core 2 Duo.
EVERY SINGLE TIME I have wanted a new CPU I've also had to get a new motherboard because the socket had changed. and EVERY SINGLE TIME I had to get all new RAM because the RAM standards had changed. And EVERY SINGLE TIME I had to get a new video card because the standard for video card slots had changed.
Yes, even for the Athlon 700 -> Athlon 3200 move, which are both 32 bit Athlons. The RAM went from PC133 to DDR400. The AGP-Pro TNT2 video card wasn't compatable with an AGP 4x (?) motherboard.
By the time you add up motherboard, CPU, RAM and decent video card you're 90% of the cost of a whole new machine. Cases aren't expensive and neither are CD/DVD drives. It's better to just buy the case and optical drive (and KB & mouse) as well so that you have two machines instead of one and can sell the old one, or give it to your parents, or whatever.
In the real world you can't upgrade PCs any more than you can upgrade Macs. More RAM, bigger disk, new optical drive, slightly faster CPU in the same series, things you plug into USB or FireWire. That's it.
'Oh and by the way, we need people to love it the tenth, or the hundredth, or the thousandth time they hear it,' Ball said."
Why would anyone other than maybe a service technician hear the Vista startup sound a hundred times, let alone a thousand?
I've had the PowerBook I'm typing this on for a year and I've probably heard the startup sound fewer than ten times -- right now the uptime is 42 days and I think that's prbably a bit below the average time between system updates. It gets taken between home and work every day, btw, and slept and woken multiple times a day.
When I was at university we had a couple of group projects in "software engineering" papers. They were the absolute suckiest thing ever -- like working in a company where no one had the authority to make an actual decision, there were no experienced people who knew what they were doing, and where you had no possibility of firing the guy who implemented his part totally wrong, let alone the guy who did nothing at all.
From what I've heard, nothing much has changed. And how could it?
As someone now involved in hiring recent grads (e.g. one starting tomorrow and one starting in a week) the things I'm much more likely to look for are active involvement in Open Source projects, or having published a shareware or freeware program or interesting non-static web site, or having run the student network, or set up a mini ISP or VOIP PABX for their friends, or... you get the idea. Those -- and the ability to talk intelligently about things -- are more important than grades. A+'s are great if they are found with the previously-mentioned things, but a guy with B's who has *done* stuff is better than a guy with A's who has never had the urge to create something outside of class.
Orbital plane shifts are not simple. Your velocity is a vector value, not a scalar one.
Correct so far.
If I have a vector velocity in one direction, and I add another force vector perpendicular to the original, I've done two things: the resultant vector has a new direction; the resultant vector has a larger velocity than the original. So I managed to change both my orbital plane (a little) and my altitude (more than a little.) So now I need to slow down to put myself in the same altitude as I origially was.
True, but stupid and irrelevant. It's much more efficient to apply a single deltaV change. For example for a 90 degree plane change the deltaV is sqrt(2) = 1.4142 times the orbital velocity at 135 degrees to the original vector.
Basically, I need [2 * (launch energy) * sin(angle change)] Joules of energy to make an orbital plane change. If you try to change your plane by 90 degrees, it costs you 2x the launch-energy to do so. (Please pardon the simplifications... I'm not up to typing long equations here in ascii.)
So a 180 degree plane change (reversing your orbit) is free? I think you should check your equation;-)
Try 2*(orbital speed)*sin(angle change/2).
Which, ta da, gives 2*orbital speed for reversing, and 1.4142 for a 90 degree plane change. Note: orbital speed, not launch "energy" (deltaV, presumably), which includes losses irrelevant to orbit changes.
And that's not even the most efficient way to do it. It's pretty obvious that you can do better by boosting to a higher orbit before doing the plane change. This lets you swap kinetic energy for potential energy, do the plane change at far lower velocity, and then swap the potential energy back to kinetic.
For example, from any circular orbit you can raise the high point to infinity by increasing your speed to sqrt(2) times the orbital velocity, that is a deltaV of 0.4142 of the orbital velocity. Once at the high point you have (essentially) zero velocity and can make an arbitrary plane change for free, and then fall back to your low altitude in the new orbital plane and use another 0.4142 of circular orbit velocity (at that altitude) to slow back down into a circular orbit. Total deltaV is 0.8284 times orbital velocity to e.g. reverse your orbit. That's a just a little bit less than 2 * orbital velocity.
This is a very efficient way to make any plane change whatsoever, but it takes a very long time. Compromises can be quicker while being not much more expensive. For example, for a 90 degree plane change you can do a 0.25 * orbital speed burn, boosting apogee to 3.57 times the original orbital radius at 0.35 times the original speed, do a 0.5 times original speed burn to change planes, and then fall back to the original altitude and do another 0.25 times original speed burn to leave you in the new circular orbit. Total deltaV expenditure: 1.0 times orbital speed. That's considerably cheaper than the 1.4142 times orbital speed deltaV of doing it directly (let alone the 2.0 times orbital speed of your method).
And yes, IAARS.
Oh?::raises eyebrow:: Not the type that saves marooned satellites obviously::grin::
>What's wrong with just launching it into the sun?
Simple:
Actual Earth orbital speed: 29.8 km/s Orbital speed required for Solar escape from Earth's orbit: 42.1 km/s Orbital speed required to drop it into the sun from Earth's orbit: 0 km/s
Forgetting for the moment the 11 km/s needed to get it away from the earth permanently (which is the same in either case, and gets added to the other numbers), you need 29.8 km/s to drop it into the sun, or (42.1 - 29.8) 12.3 km/s to make it leave the solar system forever.
Which is easier?
Bear in mind that twice the velocity change requires four times the fuel, three times the velocity change requires nine times the fuel etc.
As RAH said: reach low earth orbit and you're halfway to anywhere.
Oh, and the mathematically-inclined will notice that 42.1/29.8 = sqrt(2). This is not a coincidence.
Again, there's a reason airplane racing has never "taken off" (so to speak). It sounds good on paper (machines blazing through the air at hundreds of miles per hour!! Wow!!), but in practice there's not much to watch, and it's too much like a boat race. The first one to get the upper hand will almost always win.
That's certainly not true in yachting. The problem is that yacht races tend to be held over too large an area for spectators to be able to see most of the race. GPS and computer graphcs have solved that problem for TV coverage.
There is the same problem, but even more so in sailplane racing. Where Americas' Cup yacht races are held over an 18 mile long course, sailplane races are typically held over 150 - 300 mile long courses. Because the speeds are so much higher it takes about the same amount of time to complete a race.
Last week we held our first Gliding Grand Prix here in New Zealand. It is a new format for glider racing, with simultaneous starts, a race course designed to be more spectator-friendly by bringing the gliders back over the airfield during the race, and a complete TV package using live 3D computer graphics (fed by in-glider GPS via Iridium phones), live in-cockpit video cameras, and chase helicopters (which worked well other than the helicopter sometimes not being able to keep up with the gliders on the final 30 km sprint back to the airfield).
You can get an idea of the TV coverage available from movies. That is, frankly, only a shadow of what it was really like. Hopefully you'll get a chance to see it on ESPN or something soon.
There are not enough variables to introduce strategy during the race.
Both yachting and gliding have huge numbers of variables. In gliding, for example, the fastest way to the next turn point can often involve sidetracking 20 or 30 km from the direct path, and different pilots will have quite different ideas about the best place to go. Then there are the questions of how fast or slowly to fly at each point in time, whether to fly high or low, whether to fly low along a ridge, or try to take a thermal to 8000 or 10000 ft, or try to find mountain wave and climb to 20,000 or 25,000 ft or more.
A rocket race will be worse -- they're not even as maneuverable as an airplane. It'll be more like a drag race, except they'll be gone so fast you can't see anything.
As a matter of fact, these are airplanes -- airplanes with a rocket attached instead of a piston or jet engine.
If I have, say Dreamweaver running side-by-side with Safari and Navicat, then when I'm working with one of those applications my cursor already tends to be in that application's "neighborhood". So yes, such a small point would be harder to hit starting from halfway across the screen, but usually I'm starting from just a few inches away. Given those circumstances, such a menu is no harder a target to hit than an application window's toolbar or tabs.
That's very true.
Those things are hard to hit too.
I might also mention that "whacking" the cursor against the top of the screen is usually a two motion affair. Once to whack it to the top left, and again to move left or right to the desired position.
I honestly don't find that, although that's a valid technique and quite likely a pretty good one if the angle of movement is acute. But usually I find that moveing the cursor in the right direction to hit the menu I want is easy. You can see how you're doing on the way and unconsciously correct midcourse -- I think this plays to our primative hunter ability to catch balls etc.
Any decent OS or web browser will let you scale up font sizes. The end result is that your text is the same size, but smoother.
I *hate* OSes that do that! If I'm paying top dollar for lots of pixels it's because I want to put lots of text on that screen. If you feel that you need more pixels in each character in order to make them readable then I suggest you're using the wrong fonts.
The *right* fonts, by and large, are the twenty year old ones that came with the original Macintosh, especially Monaco (and Geneva for variable width). Monaco 9 is still today very hard to beat as a font for terminals or programming. And it's not just Mac-heads who think so -- I know lots of Windows and Linux people who swear by it (or close clones) as well.
Just make sure you remember to turn anti-aliasing *off* for those fonts. They're perfect already, and hand-optimized pixel by pixel by the best in the world (Susan Kare) in a way that a smoothing engine can never match.
The other half, however, is inherent in their single shared menu design. Yes, I know about the usability studies, but the majority of those stem from the time when most Apples had a single 9" screen. If you've ever used a Mac with a 30" widescreen display, I think you'll agree that the top menu bar, as with the split screen setup, often seems a long ways away from your current work window.
MacOS has always had very nice mouse acceleration that allows you to move the cursor huge distance with a flick of the wrist. Perhaps Windows has caught up now, I'm not sure. The latest KDE seems pretty good.
But the biggest issue is that even on huge screens Fitt's law still applies.
I assume that you're going to be making your windows bigger on a big screen. Why else buy it? There can't be too many people buying a 30" screen to put 50 80x24 terminal windows on it. If your application windows are bigger then that makes a Windows-style menu almost as far away as a Mac-style one. But on a huge screen that menu becomes a *tiny* target and harder to hit. The Mac menu remains infinitely tall, and you just whack the cursor up against it. The Mac retains its advantage, and I think maybe even increases it.
Re:The right programming language helps hugely
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When Bugs Aren't Allowed
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· Score: 4, Interesting
I've participated in the ICFP before (one-man team on Java, program died in the first round, so there are my cards on the table),
My cards on the table are that I've entered each of the last six years with 3 - 5 person teams using Dylan, collecting 2nd place twice and Judge's Prize twice.
but one of the reasons the International Conference on Functional Programming Contest is consistently won by Functional Programmers is that it appeals heavily towards them both in terms of getting the word out to people and in terms of task selection.
Getting the word out doesn't seem to be the problem. Last year for example there were 161 first-round entries. Only 38 entries -- 24% of the total -- were in one of the languages I mentioned as being consistently sucessful: 1 in Dylan, 16 in Haskell and 21 in OCaml.
I also disagree about task selection. C and C++ and Java are every bit as suited to the sort of tasks in the ICFP contest as they are to the things they are normally used for. What they are not suited to is doing them in a short period of time, in an exploratory programming manner, and without bugs.
Type safety, fast compiled code, garbage collection -- all of these were all but irrelevant to the last two years' tasks. The main stumbling block both years had been writing parsers.
Parsers aren't the problem. C has had parser generators for thirty years and besides the messages to be parsed were totally trivial. Dylan doesn't yet have any good tools for writing parsers, but it doesn't matter because we were able in the first eight hours of the contest to hand write a complete and correctly functioning (but stupid) program using nothing more complex than regular expressions, leaving the remaining 64 hours to think of something clever to do. Anyone using Perl or Python or Ruby probably finished the infrastructure even quicker than we did.
The right programming language helps hugely
on
When Bugs Aren't Allowed
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· Score: 5, Interesting
The site is slashdotted at the moment, so I can't read the article.
A good example of people writing complex but bug-free software under time pressure is the annual ICFP Programming Contest. This contest runs over three days, the tasks are complex enough that you usually need to write 2000 - 3000 lines of code to tackle them, and the very first thing the judges do is to throw corner-cases at the programs in an effort to find bugs. Any incorrect result or crash and you're out of the contest instantly. After that, the winner is generally the highest-performing of the correct programs.
Each year, up to 90% of the entries are eliminated in the first round due to bugs, usually including almost all the programs written in C and C++ and Java. Ocassionally, a C++ program will get through and may do well -- even win, as in 2003 when you didn't actually submit your program but ran it yourself (so it never saw data you didn't have a chance to fix it for). But most of the prize getters year after year seem to use one of three not-yet-mainstream languages:
You can argue about why, and about which of these three is the best, or which of them is more usable by mortals (I pick Dylan), but all of them are very expressive languages with uncluttered code (compared to C++ or Java), completely type-safe, produce fast compiled code, and use garbage collection.
And how many total programmers are using Dylan in this contest?:)
Not many. Just us. Unfortunately most people have not yet heard of the Dylan programming language.
Otherwise, you'll have severe selection bias - especially in contests with such a small number of Dylan users, but even if there were more. Really, contests like this are pretty useless for language evaluation - only individual-evaluation
I guess I'll have to take that as a compliment:-)
I agree that contests such as this can't prove that some language is superior to others since, yes, it is possible (though very unlikely!!) that I and my friends are all super-geniuses who could do equally well using Brainfuck or INTERCAL.
What it does prove though is that there is nothing seriously wrong with Dylan that would prevent you from using it to write a complex program very quickly, in a situation requiring high performance and absolute correctness. I don't know if you read the rules, but if a program ever crashed, or took more than 5 seconds to respond to the server, or responded with an illegal message then it was instantly out of the entire contest. That's what happened to the vast majority of C and C++ and Java programs, and that is what always happens to them.
and even that, only after a significant number of contests have been completed by the participants.
How many is significant? A Dylan entry has won prizes in each of 2001, 2003 and now 2005, despite there being only one Dylan entry each year up against hundreds of entries in other languages.
You can choose to think that my friends and I are geniuses, or you can think that maybem, just maybe, there's something worth investigating in this Dylan thing.
>I would never have thought that Haskeel and Dylan would have even placed
Not that the language is irrelevant, mind you, but with this few entrants, I wouldn't go looking for correlations.
161 entries isn't small.
And bear in mind that this isn't the first time Dylan has done well. In addition this Judges' Prize *and* 2nd place this year, Dylan programs got the Judges' Prize in 2003 and 2nd place in 2001 (losing to Haskell that time as well).
It took me more time to format and write this comment than it took me to find this: Toshiba Satellite
You left out a couple of critical points:
- "starting at 3.62 kg". The iBook is 2.2 kg, and I'd consider *that* marginally too heavy.
- "up to 2 hours battery life". The iBook gets up to six hours.
- how well is a Unix supported on it? I'm betting: not well.
No one ever said you can't get a cheap x86 laptop. but you can't get one that is simultaneously as small, cheap, fast, and with as good battery life as an iBook.
You can see here, that it was a well entrenched NeXT slogan by late 1992. The earliest quote from Jobs using it as a slogan I could find was in January of that year.
Here's one, clearly connected with Apple, from four years earlier, in 1998. I'm pretty sure, but can't prove, that it was used in connection with the Mac pretty much from the earliest days.
If someone would like to invest in Apple right now, they might not have $8,000 available to buy 100 shares. On February 28, they'll be able to buy 100 shares for $4000 or so, which perhaps they can afford.
It would seem to be a heck of a lot less paperwork to just make the minimum tradeable parcel be 50 shares instead of 100. Then they wouldn't have to send out new certificates to everyone.
Actually, I've got no idea why it's so high in the USA in the first place. Here in New Zealand most companies keep their shares in the range from $10 - $10 and have a minimum trade size of 100, so you need no more than $1000 to invest (and our dollar is worth less than a US$ anyway).
Wow, the TI-89 uses an RC oscillator for its clock!
So they haven't changed, then.
I remember overclocking TI-58/58C/59 programmable calculators in 1980. They too had just a simple RC oscillator.
I seem to recall that they worked fine at up to about five times the standard speed, with the one exception that the magnetic card reader in the TI-59 didn't work when overclocked.
Orbital insertions are two orders of magnitude harder.
No, orbital insertions require nearly 10 times the speed (or 100 times more energy). That doesn't mean that they are 100 times harder, and certainly not 100 times more expensive.
Getting out of the atmosphere is the hard part. Once you're in vacuum all you need to do is burn more fuel, for longer. That's easy, and fuel is cheap. And manage the reentry, which we also know how to do.
Yes, this is jus a first step, but it's a lot further towards going orbital than you seem to think.
And once you're in orbit... you're halfway to *anywhere*:-)
The Wright Brother's big advance was controlled, powered flight.
Actually, it was mostly the "controlled" part. They flew gliders before they flew powered aircraft, and they went back to gliders afterwards and had ten and thirty minute glider flights before they ever flew for that long in a powered aircraft.
One of Burt Rutan's big accomplishments with SS1 is in fact a way to safely control the reentry with the "feathering" tail.
Of course Rutan didn't perform any of the fundamental research that lead to the first manned flights, so his efforts are piggy-backing on those of NASA.
Yes, I agree that Rutan can only do this so cheaply because he's learned from previous efforts by NASA.
The big question is: why hasn't NASA learned the same things yet?
Slashdot Mirror
Hey dtrace is great. But you know where the largest number of computers running dtrace are?
#1 is on Macs
#2 is the iPhone and iPod Touch (will be #1 soon)
Solaris is orders of magnitude down on either of those.
When I suggested that I might switch to TelstraClear Cable Internet because of faster upload speeds and a much snappier web experience
If you like somewhere that you have that choice then you're very lucky. And you should do it. The 4 Mbps down/2 Mbps up service is the best value in internet in NZ today, assuming that you a) actually do use the internet, and b) aren't leeching things 24/7. Get the $50 10 GB/month plan if you're going to use anywhere between 6.7 GB and 16.7 GB a month. And note that that is the *total* cost -- there's no hidden cost in having to have a $35/month phone line as well before you can even order broadband, as is the case with Telecom's DSL.
Or if you're one of those strange people who actually wants to have a landline then TelstraClear only add on $20/month for that, so compared to Telecom you're effectively getting the internet for $35 or so.
The US is not the whole world. Here in New Zealand there are about as many manual transmission cars as automatics, and the only reason that there are so many automatics (there weren't in the quite recent past) is that about 50% of newly registered cars are in fact used cars from Japan (becuase they are *cheap*), which are almost invariably automatic.
Automatics have an advantage in places where you get stuck in stop/start traffic jams. Japan and the cities in the USA are like that. NZ isn't. Automatics have definite disadvantages on hilly or twisty roads, especially with smaller or more highly-tuned engines. NZ is like that. The USA mostly isn't. And most cars in NZ are 2000cc or less.
And I've used the same $1000 monitor and $300 Cambridge Soundworks speakers on my last three desktop Macs. Those are external, moveable, replaceable components on *all* computers. So how does that support a "PCs are more upgradable" argument, exactly?
Hell, you could take your monitor and speakers and hard disk from your PC and use them on a Mac Mini (or any other Mac, including an iMac or PowerBook).
I saw one of the Mac commercials talking about how Macs work out-of-the-box, and thinking about what happens when you want to upgrade.
This "you can upgrade a PC" thing is rubbish. I've always been a Mac guy but I wanted to play with Linux so I built a Pentium66 machine. Then I upgraded to a Pentium Pro 200, then to an Athlon 700, then to an Athlon 3200, and now to a Core 2 Duo.
EVERY SINGLE TIME I have wanted a new CPU I've also had to get a new motherboard because the socket had changed. and EVERY SINGLE TIME I had to get all new RAM because the RAM standards had changed. And EVERY SINGLE TIME I had to get a new video card because the standard for video card slots had changed.
Yes, even for the Athlon 700 -> Athlon 3200 move, which are both 32 bit Athlons. The RAM went from PC133 to DDR400. The AGP-Pro TNT2 video card wasn't compatable with an AGP 4x (?) motherboard.
By the time you add up motherboard, CPU, RAM and decent video card you're 90% of the cost of a whole new machine. Cases aren't expensive and neither are CD/DVD drives. It's better to just buy the case and optical drive (and KB & mouse) as well so that you have two machines instead of one and can sell the old one, or give it to your parents, or whatever.
In the real world you can't upgrade PCs any more than you can upgrade Macs. More RAM, bigger disk, new optical drive, slightly faster CPU in the same series, things you plug into USB or FireWire. That's it.
'Oh and by the way, we need people to love it the tenth, or the hundredth, or the thousandth time they hear it,' Ball said."
Why would anyone other than maybe a service technician hear the Vista startup sound a hundred times, let alone a thousand?
I've had the PowerBook I'm typing this on for a year and I've probably heard the startup sound fewer than ten times -- right now the uptime is 42 days and I think that's prbably a bit below the average time between system updates. It gets taken between home and work every day, btw, and slept and woken multiple times a day.
When I was at university we had a couple of group projects in "software engineering" papers. They were the absolute suckiest thing ever -- like working in a company where no one had the authority to make an actual decision, there were no experienced people who knew what they were doing, and where you had no possibility of firing the guy who implemented his part totally wrong, let alone the guy who did nothing at all.
... you get the idea. Those -- and the ability to talk intelligently about things -- are more important than grades. A+'s are great if they are found with the previously-mentioned things, but a guy with B's who has *done* stuff is better than a guy with A's who has never had the urge to create something outside of class.
From what I've heard, nothing much has changed. And how could it?
As someone now involved in hiring recent grads (e.g. one starting tomorrow and one starting in a week) the things I'm much more likely to look for are active involvement in Open Source projects, or having published a shareware or freeware program or interesting non-static web site, or having run the student network, or set up a mini ISP or VOIP PABX for their friends, or
Orbital plane shifts are not simple. Your velocity is a vector value, not a scalar one.
... I'm not up to typing long equations here in ascii.)
;-)
::raises eyebrow:: Not the type that saves marooned satellites obviously ::grin::
Correct so far.
If I have a vector velocity in one direction, and I add another force vector perpendicular to the original, I've done two things: the resultant vector has a new direction; the resultant vector has a larger velocity than the original. So I managed to change both my orbital plane (a little) and my altitude (more than a little.) So now I need to slow down to put myself in the same altitude as I origially was.
True, but stupid and irrelevant. It's much more efficient to apply a single deltaV change. For example for a 90 degree plane change the deltaV is sqrt(2) = 1.4142 times the orbital velocity at 135 degrees to the original vector.
Basically, I need [2 * (launch energy) * sin(angle change)] Joules of energy to make an orbital plane change. If you try to change your plane by 90 degrees, it costs you 2x the launch-energy to do so. (Please pardon the simplifications
So a 180 degree plane change (reversing your orbit) is free? I think you should check your equation
Try 2*(orbital speed)*sin(angle change/2).
Which, ta da, gives 2*orbital speed for reversing, and 1.4142 for a 90 degree plane change. Note: orbital speed, not launch "energy" (deltaV, presumably), which includes losses irrelevant to orbit changes.
And that's not even the most efficient way to do it. It's pretty obvious that you can do better by boosting to a higher orbit before doing the plane change. This lets you swap kinetic energy for potential energy, do the plane change at far lower velocity, and then swap the potential energy back to kinetic.
For example, from any circular orbit you can raise the high point to infinity by increasing your speed to sqrt(2) times the orbital velocity, that is a deltaV of 0.4142 of the orbital velocity. Once at the high point you have (essentially) zero velocity and can make an arbitrary plane change for free, and then fall back to your low altitude in the new orbital plane and use another 0.4142 of circular orbit velocity (at that altitude) to slow back down into a circular orbit. Total deltaV is 0.8284 times orbital velocity to e.g. reverse your orbit. That's a just a little bit less than 2 * orbital velocity.
This is a very efficient way to make any plane change whatsoever, but it takes a very long time. Compromises can be quicker while being not much more expensive. For example, for a 90 degree plane change you can do a 0.25 * orbital speed burn, boosting apogee to 3.57 times the original orbital radius at 0.35 times the original speed, do a 0.5 times original speed burn to change planes, and then fall back to the original altitude and do another 0.25 times original speed burn to leave you in the new circular orbit. Total deltaV expenditure: 1.0 times orbital speed. That's considerably cheaper than the 1.4142 times orbital speed deltaV of doing it directly (let alone the 2.0 times orbital speed of your method).
And yes, IAARS.
Oh?
>What's wrong with just launching it into the sun?
Simple:
Actual Earth orbital speed: 29.8 km/s
Orbital speed required for Solar escape from Earth's orbit: 42.1 km/s
Orbital speed required to drop it into the sun from Earth's orbit: 0 km/s
Forgetting for the moment the 11 km/s needed to get it away from the earth permanently (which is the same in either case, and gets added to the other numbers), you need 29.8 km/s to drop it into the sun, or (42.1 - 29.8) 12.3 km/s to make it leave the solar system forever.
Which is easier?
Bear in mind that twice the velocity change requires four times the fuel, three times the velocity change requires nine times the fuel etc.
As RAH said: reach low earth orbit and you're halfway to anywhere.
Oh, and the mathematically-inclined will notice that 42.1/29.8 = sqrt(2). This is not a coincidence.
Again, there's a reason airplane racing has never "taken off" (so to speak). It sounds good on paper (machines blazing through the air at hundreds of miles per hour!! Wow!!), but in practice there's not much to watch, and it's too much like a boat race. The first one to get the upper hand will almost always win.
That's certainly not true in yachting. The problem is that yacht races tend to be held over too large an area for spectators to be able to see most of the race. GPS and computer graphcs have solved that problem for TV coverage.
There is the same problem, but even more so in sailplane racing. Where Americas' Cup yacht races are held over an 18 mile long course, sailplane races are typically held over 150 - 300 mile long courses. Because the speeds are so much higher it takes about the same amount of time to complete a race.
Last week we held our first Gliding Grand Prix here in New Zealand. It is a new format for glider racing, with simultaneous starts, a race course designed to be more spectator-friendly by bringing the gliders back over the airfield during the race, and a complete TV package using live 3D computer graphics (fed by in-glider GPS via Iridium phones), live in-cockpit video cameras, and chase helicopters (which worked well other than the helicopter sometimes not being able to keep up with the gliders on the final 30 km sprint back to the airfield).
You can get an idea of the TV coverage available from movies. That is, frankly, only a shadow of what it was really like. Hopefully you'll get a chance to see it on ESPN or something soon.
I have some photos on my site, and there are more on the official site.
There are not enough variables to introduce strategy during the race.
Both yachting and gliding have huge numbers of variables. In gliding, for example, the fastest way to the next turn point can often involve sidetracking 20 or 30 km from the direct path, and different pilots will have quite different ideas about the best place to go. Then there are the questions of how fast or slowly to fly at each point in time, whether to fly high or low, whether to fly low along a ridge, or try to take a thermal to 8000 or 10000 ft, or try to find mountain wave and climb to 20,000 or 25,000 ft or more.
A rocket race will be worse -- they're not even as maneuverable as an airplane. It'll be more like a drag race, except they'll be gone so fast you can't see anything.
As a matter of fact, these are airplanes -- airplanes with a rocket attached instead of a piston or jet engine.
1) It's an option in those OSs.
It is? The only way I've found on Windows and X is to lie about the DPI.
2) Wait until you get older and your sight starts to fail.
It's ok so far at 43.
If I have, say Dreamweaver running side-by-side with Safari and Navicat, then when I'm working with one of those applications my cursor already tends to be in that application's "neighborhood". So yes, such a small point would be harder to hit starting from halfway across the screen, but usually I'm starting from just a few inches away. Given those circumstances, such a menu is no harder a target to hit than an application window's toolbar or tabs.
That's very true.
Those things are hard to hit too.
I might also mention that "whacking" the cursor against the top of the screen is usually a two motion affair. Once to whack it to the top left, and again to move left or right to the desired position.
I honestly don't find that, although that's a valid technique and quite likely a pretty good one if the angle of movement is acute. But usually I find that moveing the cursor in the right direction to hit the menu I want is easy. You can see how you're doing on the way and unconsciously correct midcourse -- I think this plays to our primative hunter ability to catch balls etc.
HIgher resolution != Smaller text
Any decent OS or web browser will let you scale up font sizes. The end result is that your text is the same size, but smoother.
I *hate* OSes that do that! If I'm paying top dollar for lots of pixels it's because I want to put lots of text on that screen. If you feel that you need more pixels in each character in order to make them readable then I suggest you're using the wrong fonts.
The *right* fonts, by and large, are the twenty year old ones that came with the original Macintosh, especially Monaco (and Geneva for variable width). Monaco 9 is still today very hard to beat as a font for terminals or programming. And it's not just Mac-heads who think so -- I know lots of Windows and Linux people who swear by it (or close clones) as well.
Just make sure you remember to turn anti-aliasing *off* for those fonts. They're perfect already, and hand-optimized pixel by pixel by the best in the world (Susan Kare) in a way that a smoothing engine can never match.
The other half, however, is inherent in their single shared menu design. Yes, I know about the usability studies, but the majority of those stem from the time when most Apples had a single 9" screen. If you've ever used a Mac with a 30" widescreen display, I think you'll agree that the top menu bar, as with the split screen setup, often seems a long ways away from your current work window.
MacOS has always had very nice mouse acceleration that allows you to move the cursor huge distance with a flick of the wrist. Perhaps Windows has caught up now, I'm not sure. The latest KDE seems pretty good.
But the biggest issue is that even on huge screens Fitt's law still applies.
I assume that you're going to be making your windows bigger on a big screen. Why else buy it? There can't be too many people buying a 30" screen to put 50 80x24 terminal windows on it. If your application windows are bigger then that makes a Windows-style menu almost as far away as a Mac-style one. But on a huge screen that menu becomes a *tiny* target and harder to hit. The Mac menu remains infinitely tall, and you just whack the cursor up against it. The Mac retains its advantage, and I think maybe even increases it.
I've participated in the ICFP before (one-man team on Java, program died in the first round, so there are my cards on the table),
My cards on the table are that I've entered each of the last six years with 3 - 5 person teams using Dylan, collecting 2nd place twice and Judge's Prize twice.
but one of the reasons the International Conference on Functional Programming Contest is consistently won by Functional Programmers is that it appeals heavily towards them both in terms of getting the word out to people and in terms of task selection.
Getting the word out doesn't seem to be the problem. Last year for example there were 161 first-round entries. Only 38 entries -- 24% of the total -- were in one of the languages I mentioned as being consistently sucessful: 1 in Dylan, 16 in Haskell and 21 in OCaml.
I also disagree about task selection. C and C++ and Java are every bit as suited to the sort of tasks in the ICFP contest as they are to the things they are normally used for. What they are not suited to is doing them in a short period of time, in an exploratory programming manner, and without bugs.
Type safety, fast compiled code, garbage collection -- all of these were all but irrelevant to the last two years' tasks. The main stumbling block both years had been writing parsers.
Parsers aren't the problem. C has had parser generators for thirty years and besides the messages to be parsed were totally trivial. Dylan doesn't yet have any good tools for writing parsers, but it doesn't matter because we were able in the first eight hours of the contest to hand write a complete and correctly functioning (but stupid) program using nothing more complex than regular expressions, leaving the remaining 64 hours to think of something clever to do. Anyone using Perl or Python or Ruby probably finished the infrastructure even quicker than we did.
The site is slashdotted at the moment, so I can't read the article.
A good example of people writing complex but bug-free software under time pressure is the annual ICFP Programming Contest. This contest runs over three days, the tasks are complex enough that you usually need to write 2000 - 3000 lines of code to tackle them, and the very first thing the judges do is to throw corner-cases at the programs in an effort to find bugs. Any incorrect result or crash and you're out of the contest instantly. After that, the winner is generally the highest-performing of the correct programs.
Each year, up to 90% of the entries are eliminated in the first round due to bugs, usually including almost all the programs written in C and C++ and Java. Ocassionally, a C++ program will get through and may do well -- even win, as in 2003 when you didn't actually submit your program but ran it yourself (so it never saw data you didn't have a chance to fix it for). But most of the prize getters year after year seem to use one of three not-yet-mainstream languages:
- Dylan
- Haskell
- OCaml
You can argue about why, and about which of these three is the best, or which of them is more usable by mortals (I pick Dylan), but all of them are very expressive languages with uncluttered code (compared to C++ or Java), completely type-safe, produce fast compiled code, and use garbage collection.
Jet powered bird-man flight seems to give the ability to cover distance without losing altitude, but the jets are not powerful enough to climb
They'e plenty powerful. See what they can do on an aircraft:
http://www.silentwingsairshows.com/jet.html
And how many total programmers are using Dylan in this contest? :)
:-)
Not many. Just us. Unfortunately most people have not yet heard of the Dylan programming language.
Otherwise, you'll have severe selection bias - especially in contests with such a small number of Dylan users, but even if there were more. Really, contests like this are pretty useless for language evaluation - only individual-evaluation
I guess I'll have to take that as a compliment
I agree that contests such as this can't prove that some language is superior to others since, yes, it is possible (though very unlikely!!) that I and my friends are all super-geniuses who could do equally well using Brainfuck or INTERCAL.
What it does prove though is that there is nothing seriously wrong with Dylan that would prevent you from using it to write a complex program very quickly, in a situation requiring high performance and absolute correctness. I don't know if you read the rules, but if a program ever crashed, or took more than 5 seconds to respond to the server, or responded with an illegal message then it was instantly out of the entire contest. That's what happened to the vast majority of C and C++ and Java programs, and that is what always happens to them.
and even that, only after a significant number of contests have been completed by the participants.
How many is significant? A Dylan entry has won prizes in each of 2001, 2003 and now 2005, despite there being only one Dylan entry each year up against hundreds of entries in other languages.
You can choose to think that my friends and I are geniuses, or you can think that maybem, just maybe, there's something worth investigating in this Dylan thing.
161 entries isn't small.
And bear in mind that this isn't the first time Dylan has done well. In addition this Judges' Prize *and* 2nd place this year, Dylan programs got the Judges' Prize in 2003 and 2nd place in 2001 (losing to Haskell that time as well).
It took me more time to format and write this comment than it took me to find this: Toshiba Satellite
You left out a couple of critical points:
- "starting at 3.62 kg". The iBook is 2.2 kg, and I'd consider *that* marginally too heavy.
- "up to 2 hours battery life". The iBook gets up to six hours.
- how well is a Unix supported on it? I'm betting: not well.
No one ever said you can't get a cheap x86 laptop. but you can't get one that is simultaneously as small, cheap, fast, and with as good battery life as an iBook.
You can see here, that it was a well entrenched NeXT slogan by late 1992. The earliest quote from Jobs using it as a slogan I could find was in January of that year.
Here's one, clearly connected with Apple, from four years earlier, in 1998. I'm pretty sure, but can't prove, that it was used in connection with the Mac pretty much from the earliest days.
If someone would like to invest in Apple right now, they might not have $8,000 available to buy 100 shares. On February 28, they'll be able to buy 100 shares for $4000 or so, which perhaps they can afford.
It would seem to be a heck of a lot less paperwork to just make the minimum tradeable parcel be 50 shares instead of 100. Then they wouldn't have to send out new certificates to everyone.
Actually, I've got no idea why it's so high in the USA in the first place. Here in New Zealand most companies keep their shares in the range from $10 - $10 and have a minimum trade size of 100, so you need no more than $1000 to invest (and our dollar is worth less than a US$ anyway).
Wow, the TI-89 uses an RC oscillator for its clock!
So they haven't changed, then.
I remember overclocking TI-58/58C/59 programmable calculators in 1980. They too had just a simple RC oscillator.
I seem to recall that they worked fine at up to about five times the standard speed, with the one exception that the magnetic card reader in the TI-59 didn't work when overclocked.
Orbital insertions are two orders of magnitude harder.
... you're halfway to *anywhere* :-)
No, orbital insertions require nearly 10 times the speed (or 100 times more energy). That doesn't mean that they are 100 times harder, and certainly not 100 times more expensive.
Getting out of the atmosphere is the hard part. Once you're in vacuum all you need to do is burn more fuel, for longer. That's easy, and fuel is cheap. And manage the reentry, which we also know how to do.
Yes, this is jus a first step, but it's a lot further towards going orbital than you seem to think.
And once you're in orbit
The Wright Brother's big advance was controlled, powered flight.
Actually, it was mostly the "controlled" part. They flew gliders before they flew powered aircraft, and they went back to gliders afterwards and had ten and thirty minute glider flights before they ever flew for that long in a powered aircraft.
One of Burt Rutan's big accomplishments with SS1 is in fact a way to safely control the reentry with the "feathering" tail.
"budget embarrassingly smaller than NASA's"
Of course Rutan didn't perform any of the fundamental research that lead to the first manned flights, so his efforts are piggy-backing on those of NASA.
Yes, I agree that Rutan can only do this so cheaply because he's learned from previous efforts by NASA.
The big question is: why hasn't NASA learned the same things yet?