The 1/3 effect of gravity would lower the amount of friction from the ground, but the same amount of force would be required to accellerate the same amount of mass to the same degree.
As long as the wind is strong enough to overcome the friction trying to keep it still, they won't really care how fast it accelerates. They can wait a few minutes as it comes up to speed:)
Also, if indeed the air is 100X more dense on Earth than on Mars, wouldn't that mean that 1/100th of the atmospheric particles would have to move at 100x the velocity?
No. The force applied by moving air on an object (or a moving object on still air -- it's all relative) varies based on the square of the speed. Double the speed, the force increases by a factor of four.
I think the theory is actually "force = mass x acceleration" (hence "acceleration = force / mass"), and since the mass of the object is the same on Mars as it is on Earth, you'd need the same (wind) force to accelerate it to a given speed.
Yes, I'm fully aware of Newton's second law. But I'm talking about friction, not F=m * a.
As a rule of thumb, it's twice as hard to push something twice as heavy, everything else being equal. This applies to rolling friction as well. I'm not talking about accelerating it -- only maintaining a given speed.
Note that this is just a rule of thumb -- it's not in the same category as F=m * a. But it's generally true.
OTOH, rolling resistance would probably be lower on Mars than on Earth...
Yes, it would be about 1/3rd as much with everything else being equal.
Mar's atmospheric pressure is only about 1% of our atmospheric pressure at most.
This means that it would require a wind about 10x as strong as here to produce the same amount of force on something like this rover.
Fortunately, the gravity on Mars is about 1/3rd of ours, so in theory you'd need only about 1/3rd as much force to move your giant beach ball, so I guess you could get the same amount of movement on Mars as you do here with only 3x as much wind.
(Some more thoughts along this line can be found here, which is a page about a simulated plane flying on Mars.)
Apparantly Mars does have strong winds, so maybe this isn't as crazy as I first thought:)
As an example, the article talks about a 20 m/s wind on Mars -- that would produce the same thrust on a stationary object as a 2 m/s wind would here on Earth -- not very much. But once the object started moving, the thrust would not drop off as fast as it does here (after all, wind won't usually push something faster than the wind is going) so if the ball was light enough, it might actually move at a decent clip. But it would have to be very light.
He should really attach a little beeper thing to it. Like a car in a parking lot, this thing could be lost very easily.
You mean something like this? At 7 g, it would double the weight of his helicopter.:) (but yes, you can buy or build similar devices that weigh less.)
Still, for larger (larger than 7 g anyways) R/C planes, these things are *very* nice. I put one in just about all my planes, and already they've saved me lots of trekking around in the woods looking for a plane of mine that I've lost...
Yes, NT SP6 from 3 years ago caused a problem accessing Notes. It did not "broke all kinds of stuff".
I was doing Tivoli support at the time. It broke our product, and there were others as well -- pretty much anything that used Winsock. I think that qualifies as `all kinds of stuff'. (And yes, our product *was* written for NT.)
More recently, Windows 2000 SP3 broke name resolution for all non-Administator users.
Here's the details. That was just a few months ago...
Back to the point - to say that MS updates are buggy and unstable and break all kinds of stuff is a lie.
I did not say that. I pointed out a case where a Microsoft patch (service packs, no less) broke many things. Certainly, it wasn't just Notes that broke.
I know about these problems, and my job isn't even really about Windows. Somebody who works a lot more with Windows probably knows dozens more -- I know of a few more, but tracking them down isn't really worth the time.
Windows works with so many different things, and has so many little quirks in there to make old applications works, it's amazing it works at all. I don't envy those guys their job at all maintaing it -- but certainly, to claim that their fixes don't break things (which wasn't the original claim -- I know that) is silly.
I don't remember ever applying a MS patch that messed up another piece of software.
You must not have applied many MS patches then.
Here is the big example that I can think of -- SP6 broke all kinds of stuff. So much stuff that MS released SP6a shortly after. And that's hardly the only example.
They don't really have an atomic clock in them. They work by getting radio signals from WWV. If you have BPL in your neighborhood, you can say goodbye to those clocks.
As much as I'd like to agree with you, you're wrong. These devices use the time signal at 60 khz, not the ones at 2.5, 5, 10, 15 or 20 mhz. Here is a page that gives more details. 60 khz is outside of the 2 mhz - 80 mhz band, so it should be unaffected.
For example, in 1998, a radio-control model airplane forced the pilot of a DC-9 to change his approach to Dulles International Airport.
I have my doubts about this, but even if it did happen, I doubt the model airplane forced anything. I tend to doubt that a DC-9 pilot would even be able to see a normal sized model plane during normal flying. What seems more likely is that he saw a full sized plane way off, and thought it was a model much closer, and then over-reacted (which is probably safer than under-reacting.)
This sort of thing is usually really well documented by the FAA. Given the details given, I ought to be able to find the indident report, but I wasn't able to. But perhaps I'm just looking in the wrong place...
The sky is big. Really big. And it's hard to make two model airplanes collide when you're flying only 20 feet away from you -- to think you could do it intentionally, with the plane thousands of feet up, trying to hit a jet going hundreds of miles per hour is just crazy. Model airplanes just aren't the wonderful weapons that some journalists think they are.
Actually though, it's not too bad an analogy. While Earth based servers aren't absolutely unreachable like SPirit, they are often remote, and there are expenses associated with visiting them in person.
If you're thinking of traditional servers, sure. But the problem with Spirit is hardly unique. Satellite fail, and often people down on the ground are trying to repair them remotely just like was done with Spirit. Or suppose you're exploring the Marianas trench with some little remote controlled submersible and something goes wrong -- if it can't just float up on it's own (hopefully they usually have slightly positive bouyancy), it may very well be lost if you can't find a way to get it at least somewhat repaired.
In theory, you could retrieve these things, but the cost is probably too much to make it worthwhile.
Current remote X server: 272 MB. Local X server: 161 MB
I doubt X is really using that much memory. What's much more likely is that this is an x86 box, and your AGP arpeture size is set to 256 MB on the remote box and 128 MB on the second box. X mmaps the AGP arpeture, so that memory is included in it's memory usage as displayed by the OS. Assuming that I'm right, X is really only using 16 MB in the first machine, and 33 MB in the second.
As I write this the bid is over $8000 dollars with seven days to go.
Just because somebody has bid that much, it doesn't mean that somebody intends to bid that much. Bids for `flavor of the day' items like this and the world's largest cheetos often go way up really fast.
It wouldn't surprise me at all if many (most?) of those bids aren't serious at all. Especially those from the users with little feedback.
However, thanks to Tommy Tutone, unlike the world's largest cheeto, this number does actually have some value to a business and it obviously isn't going to expire after a few days. So he may very well get $8k for it. But now that it's on/., people will probably drive the bidding way higher, but not intend to pay.
I also predict a large slew of other xxx-867-5309 numbers showing up on Ebay in a short period of time.
One example from my campus is the retiring of the newsgroup server and telnet.
This is a pretty poor example. Usenet has hardly died out -- in fact, I'd guess that more people are using it now than at any other time. The percentage of people online using it is probably lower than it has ever been since it's inception, but with so many people out there, there's still a lot of people using it.
(Granted, many (most?) are using it for porn and warez, but that was probably true 10 years ago too.)
As for telnet, ssh is much more like telnet than WWW is like gopher. I doubt many people lament the loss of telnet access (it having been replaced with ssh)... but going from gopher to the WWW is a very different transition. WWW is everything that gopher wasn't, but gopher had a certain charm that escapes most of the WWW.
As for when I last used gopher? A few weeks ago, actually. Somebody mentioned it, and I wondered if browsers still supported it (I remember how Mosaic would support it)... and Mozilla does!
That's what coax is for. Very RFI resistant, and pretty cheap as well.
To followup to my own post, if this wire is going to something that handles only low frequencies, like a power line or a speaker wire, there's no need for even coax -- low-pass filters at both ends (some simple ferrite beads might do it) should cover that nicely, keeping the RF signal out of the electronics connected to it.
Gaaah!!! No, no, no!!! 5 watt transmitters in a backstage environment?!?
I did not mention a power range -- that was the parent of my post. 5 watts is enough power to talk across town (or across country with the right antenna and frequencies, but I digress...) I imagine that even 100 mW would be plenty for these people's needs.
You key up one of those things next to an unbalanced signal line, and *everyone*'s gonna know it.
Unshielded lines? There's your problem. Let's hope nobody decides to use these to mess with you:)
most cabling and playback/processing equipment is portable, and certainly not run in nice steel conduit - which, sadly, leaves it susceptible to RFI.
That's what coax is for. Very RFI resistant, and pretty cheap as well.
Using batteries as an excuse to go VoIP, which also uses batteries, doesn't make sense.
The voice of reason.
If interference is the real issue, look into low frequency radios with a 5 watt range.
The school ought to be able to have a 20 khz or so chunk of frequency allocated to it. In fact, it may already have such a frequency allocated to it -- certainly there's a lot of schools listed in the scanner lists. This frequency should be mostly free from interference (as opposed to FRS or stuff on 27 mhz, 49 mhz, 900 mhz or any of the other unlicensed bands.) If you are picking up intereference, either your radios are just crappy or somebody's causing interference. If it's the latter, get your local ham radio club (perhaps the school has one?) to track it down for you, and the FCC may require them (the source of the interference) to fix it.
If you give someone a burned DVD of all your MP3's, no one can track you.
I've heard that CD-R drives burn a unique (to the burner) serial number into every disk they burn. If true (I don't know -- it's all very hush-hush) and if DVD+-R drives do the same (I suspect that they would be similar) then you could be tracked to some degree. Certainly, if somebody had two DVDs, they could tell if they were written by the same writer or not by checking that ID. If the IDs match, and one was known written by your writer, then the other was too.
Just a minor nit. I agree with you. In any event, this sort of trading is known as `fair use'. Or at least it used to be...
The $5 models that Wal-Mart sells keep time accurate to 1 second in a year, and last several years on their included batteries.
Certainly, this would be possible, but the $5 watches I've bought didn't come anywhere near this level of accuracy. More likely was that they were off like a minute or two per year.
Still, the accuracy is very good compared to a mechanical watch, especailly an old one. And you can't beat the price.
The current batch of `atomic clocks' (they have a receiver to pick up the 60 khz time signal) are very nice -- as long as you're close enough (most of North America is) and you're not living in a big metal box, they're always accurate to a very small fraction of a second. And you can get one for around $10 if you look around...
I don't mean to excure them, but I do think it's worth wondering aloud whether they got some not-so-subtle hints that the didn't need to mention this to the public.
This is quite common, actually. Suppose you run an ISP, and the government is `interested' in one of your customer's web pages. They may subpoena you for information about this customer, and will probably also *prohibit* you from even telling the customer. Nothing subtle about it.
If you do mention it, it means a fine or jail time for you.
It's really unfair if you ask me... but of course they don't usually ask me:)
The moment they show it to you, the OSS community will 'remove' it from all the distros of Linux. Then SCO won't be able to get licensing fees from anybody.
... if it's actually infringing. SCO has already claimed ownership of errno.h, but I don't see it going away anytime soon.
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As a rule of thumb, it's twice as hard to push something twice as heavy, everything else being equal. This applies to rolling friction as well. I'm not talking about accelerating it -- only maintaining a given speed.
Note that this is just a rule of thumb -- it's not in the same category as F=m * a. But it's generally true.
Yes, it would be about 1/3rd as much with everything else being equal.This means that it would require a wind about 10x as strong as here to produce the same amount of force on something like this rover.
Fortunately, the gravity on Mars is about 1/3rd of ours, so in theory you'd need only about 1/3rd as much force to move your giant beach ball, so I guess you could get the same amount of movement on Mars as you do here with only 3x as much wind.
(Some more thoughts along this line can be found here, which is a page about a simulated plane flying on Mars.)
Apparantly Mars does have strong winds, so maybe this isn't as crazy as I first thought :)
As an example, the article talks about a 20 m/s wind on Mars -- that would produce the same thrust on a stationary object as a 2 m/s wind would here on Earth -- not very much. But once the object started moving, the thrust would not drop off as fast as it does here (after all, wind won't usually push something faster than the wind is going) so if the ball was light enough, it might actually move at a decent clip. But it would have to be very light.
Still, for larger (larger than 7 g anyways) R/C planes, these things are *very* nice. I put one in just about all my planes, and already they've saved me lots of trekking around in the woods looking for a plane of mine that I've lost ...
More recently, Windows 2000 SP3 broke name resolution for all non-Administator users. Here's the details. That was just a few months ago ...
I did not say that. I pointed out a case where a Microsoft patch (service packs, no less) broke many things. Certainly, it wasn't just Notes that broke.I know about these problems, and my job isn't even really about Windows. Somebody who works a lot more with Windows probably knows dozens more -- I know of a few more, but tracking them down isn't really worth the time.
Windows works with so many different things, and has so many little quirks in there to make old applications works, it's amazing it works at all. I don't envy those guys their job at all maintaing it -- but certainly, to claim that their fixes don't break things (which wasn't the original claim -- I know that) is silly.
Here is the big example that I can think of -- SP6 broke all kinds of stuff. So much stuff that MS released SP6a shortly after. And that's hardly the only example.
This sort of thing is usually really well documented by the FAA. Given the details given, I ought to be able to find the indident report, but I wasn't able to. But perhaps I'm just looking in the wrong place ...
The sky is big. Really big. And it's hard to make two model airplanes collide when you're flying only 20 feet away from you -- to think you could do it intentionally, with the plane thousands of feet up, trying to hit a jet going hundreds of miles per hour is just crazy. Model airplanes just aren't the wonderful weapons that some journalists think they are.
In theory, you could retrieve these things, but the cost is probably too much to make it worthwhile.
It wouldn't surprise me at all if many (most?) of those bids aren't serious at all. Especially those from the users with little feedback.
However, thanks to Tommy Tutone, unlike the world's largest cheeto, this number does actually have some value to a business and it obviously isn't going to expire after a few days. So he may very well get $8k for it. But now that it's on /., people will probably drive the bidding way higher, but not intend to pay.
I also predict a large slew of other xxx-867-5309 numbers showing up on Ebay in a short period of time.
Of course, it's open source, so feel free to add the button yourself.
I really miss TA. I hope it gets a true sequel, with modern graphics ... that would kick so much ass!
And Ground Control didn't even come close to the greatness that was TA :)
(Granted, many (most?) are using it for porn and warez, but that was probably true 10 years ago too.)
As for telnet, ssh is much more like telnet than WWW is like gopher. I doubt many people lament the loss of telnet access (it having been replaced with ssh) ... but going from gopher to the WWW is a very different transition. WWW is everything that gopher wasn't, but gopher had a certain charm that escapes most of the WWW.
As for when I last used gopher? A few weeks ago, actually. Somebody mentioned it, and I wondered if browsers still supported it (I remember how Mosaic would support it) ... and Mozilla does!
Archie searched ftp sites for a given file. There was a central server that polled all the known sites occasionally, and it handled your requests.
Veronica indexed gopher sites, much like google does web sites.
Of course, you could have learned all this much faster by just using google.
Of course, you probably already know all this :)
Just a minor nit. I agree with you. In any event, this sort of trading is known as `fair use'. Or at least it used to be ...
Still, the accuracy is very good compared to a mechanical watch, especailly an old one. And you can't beat the price.
The current batch of `atomic clocks' (they have a receiver to pick up the 60 khz time signal) are very nice -- as long as you're close enough (most of North America is) and you're not living in a big metal box, they're always accurate to a very small fraction of a second. And you can get one for around $10 if you look around ...
It was mediocre. Not awful, just mediocre.
If you do mention it, it means a fine or jail time for you.
It's really unfair if you ask me ... but of course they don't usually ask me :)
Had you shorted their stock right when all this happened, you'd have lost a *bundle*.