"Many computer scientists have fallen into the trap of trying to define languages like George Orwell's Newspeak, in which it is impossible to think bad thoughts. What they end up doing is killing the creativity of programming." --Larry Wall
SPARK seems to be an extreme example. Though I've never used it, I venture to guess that in a quixotic effort to avoid all bugs SPARK only buries real bugs underneath a mountain of its own pedantry.
Joanne: I am not a scientist nor an engineer, and therefore my goal has never been to do scientific research.
Full stop. Why should I pay attention to the voluminous opinions of this vicarious scientist? Give me a real scientist in the field who undestands the topic from first-hand experience.
Interesting. You avoided my question, changed the subject, and made an out-of-context quote.
Notice the words I wrote right beforehand, which state the current problem of note. Here, I'll quote it for you--
We have a ball bouncing off the moon with enormous, escape-velocity-ish speed. (It's not really going to bounce but let's say it does.) It bounces inelastically and "straight up". How high does it go?
(In retrospect I said "inelastic" when I meant "elastic" but I assume you took the meaning.)
The past 8 posts in our discussion began with your initial refutation of my point-source assumption: "That only holds true when the gravitational body is small enough, or far enough away, to be dealt with as a point source. When you're close up, you can't do that and have to deal with messy integrations."
I stated that, no, it is mathematically correct to use point-source calculations. You then went on to say, "Christ. That's only true when the diameter of the sphere is than the distance of the object from the sphere" and "*Sigh*. You're neglecting tides."
I then spelled out, quite explicitly, how the problem should be solved using point-source calculations. I challenged you, asking how you would use "tides" in this problem. I'm basically calling you on it, because honestly it seems like you are taking lines out of a textbook without really understanding their application or their purview.
You neglected to take my challenge; you haven't told me how "tides" would be applied to the problem, or what exactly is incorrect about the point-source calculations. How would you do this problem differently?
Instead, you backed up 8 posts, asking me to show numbers regarding whether a uniform field can be used or not. By this time, however, I have already stated the problem as re-quoted above (what you neglected to quote). The key words are "escape-velocity-ish speed". I took the uniform-field-or-not issue out entirely by stating the problem in this way in order to address the point-source-or-not issue. Perhaps I lost you. But remember, you started by claiming point-source was invalid, I was merely following up.
You now wish to discuss the uniform-field-or-not topic. I would love to address this topic, however first things first. We must first agree whether a point-source calculation is valid or not. You claim it is not. I ask you again, show me how the problem should be done differently. Are you referring to such pedantry as nonuniform mass distribution? Show me specifically why the point-source calculation is wrong.
By the way, I fully expect you NOT to answer, as you have done before. But I'll wait.
Surely you don't mean I'm incorrect because I haven't factored in tidal effects? If so, that's the most pedantic thing I've ever heard. It's like if I'm explaining the parabolic nature of projectiles, you interrupt exclaiming, "You are wrong! You haven't accounted for the coriolis force due to the earth's rotation!" Coriolis effects have their purview, but we must be reasonable given the problem at hand (not to mention air is more significant).
Do you even acknowledge the theorem to which I'm referring? You seem to miss it. The first thing to do is to look it up or prove it yourself.
Part of what you are saying is true, but you miss the happy mathematical cancellations which occur in the unique situation of a sphere combined with the inverse-square relationship. With any non-spherical and/or non-inverse-square situation you must indeed perform integrations.
Now let's return to the original problem. We have a ball bouncing off the moon with enormous, escape-velocity-ish speed. (It's not really going to bounce but let's say it does.) It bounces inelastically and "straight up".
How high does it go?
I assume that you have recanted your assumption of a uniform gravitational field. It's not going to be even close to within an order of magnitude. That much is clear.
Our goal is to integrate force over distance, equating that with the kinetic energy at bounce-time.
Say the ball is 10 meters off the ground. What is the gravitational force? We do an integration (since we don't trust the aforementioned theorem) and find -- wow -- the force is the same as the force due to a point mass at the center of the moon.
Say the ball is 500 meters off the ground. We do the integration again, and whaddaya know, the force is again the same as the force due to a point mass.
It becomes clear that we can use a simple inverse-square in our force over distance integral. The result is 1/R - 1/r, where R is the radius of the moon and r is the unknown radius we seek. Put in all the constants, equate it with the kinetic energy at bounce-time and there's your answer.
Now of course the problem is grossly oversimplified. It's not going to bounce "straight" up, the earth may have a measurable effect if the velocity is large enough, etc. But it's a starting point at least.
If you don't agree with my method, how exactly would you do it? With tidal effects? Coriolis forces? What?
Not sure what your sentence is trying to say, but my statement is indeed true.
In an inverse-square relationship, there's a happy cancellation of forces which net to a single point source at the center of the sphere, no matter where you are outside the sphere.
It even works if you are inside the sphere! In this case, the gravitational pull is equivalent to a point source with mass equal to the sphere whose surface passes through you. The gravitational effect of the leftover "shell" completely cancels itself out.
Really, it's a nice theorem. Do the integration. I'll wait.
You are incorrect. It's a mathematical theorem that a sphere can indeed be treated as a point source in the case of inverse-square relationship.
Standing on the moon, you can think of all the moon's mass concentrated at a point in the center with you standing on a massless structure surrounding that point.
This makes the integration easy. Force goes as inverse-square. Potential energy goes as inverse-cube.
The uniform-field calculation is not within an order of magnitude.
But anyway, the whole thing is silly. If you assume no energy is lost during the bounce, it could conceivably bounce all the way back to earth!
In reality, it's going to plummet into the moon and make a crater. The energy will go into heat and into moving lunar soil.
The bounce would be large enough to invalidate your presupposition of a uniform gravitational field.
The gravitational field is dropping off with the inverse of the distance from the moon's center (i.e. the gravitational force going with the inverse square).
I find it unbelievable that you don't have this problem. I've not seen once exception in 8 years. Could you send me a message giving your exact specs please?
Thus far there have been two posts denying the existence of this problem. And I notice that I got two flamebait points.
Unfortunately I failed to mention that it's essential to open a web page with several images for the test.
I've installed linux on a variety of top-end machines over the years: from P2s with Matrox cards to P4s and AthlonXPs with GeForce4s and Radeon9800s. Each and every one has this problem.
Yes, the problem does exist. No, it's not trolling to say so.
I forgot to mention, you need to open a nontrivial web page for the test (say, http://news.google.com).
My system is nearly identical to yours. Konqueror is the worst of them all. I use Gentoo and have tried various levels of CFLAGS, all with the same effect.
To the *nix users out there, have you ever considered that XFree86... sucks?
Yes, it gets the job done. Yes, it's the most popular, it supports a plethora hardware, it is open source, etc. etc. But, all trolling aside, the thing does indeed suck.
As a longtime linux user, I can say that every single linux machine I've had, including the current latest-and-greatest, has miserably failed my Window Drag Test(TM).
To perform this test, start with a good web browser (firefox, mozilla, konqueror, galeon, whatever). Enable the equivalent of "Opaque Window Moving" on your window manager. Open a browser window and drag it to the bottom-left corner. Now drag it back. What happens? Open two windows. Drag one across the other. What happens?
What happens is smearing. Gross. Ugly. Unacceptable. Call me picky, but I don't care how much hardware you support, or how popular you are, or whatever -- if your graphical system isn't good at *drawing graphics*, then it sucks.
And this is what people notice when they first sit down in front of a linux machine. And it's killing us. Whatever the shortcomings of Windows and Macs, neither have this problem.
So this licensing issue is good news, if it can galvanize the community to pull more resources into developing alternatives to XFree86 (because it sucks!).
You must shell out lots of cash for a Qt license if you wish to distribute a commercial application for KDE/Qt. There is no such license fee for Gnome/gtk. So, in this sense, Gnome is still "more free".
Child A swims with a team for two hours a day. He eats a sensible diet. He spends a great deal of time drawing or building cool stuff with his massive lego collection.
Child B doesn't exercise. He lives on Cheetos. He's fat. He plays video games all day. His parents don't give a shit.
I have no scientific evidence in front of me, but I contend that Child A will never, ever develop ADHD.
Sure, ADHD is "real", but that's a vacuous statement. It is "really" a symptom. Child B's life is antithetical to how humans have been living on this earth for tens of thousands of years. Humans just aren't evolved to live like that -- of course something's going to happen to Child B, call it ADHD.
For God's sake stop medicating your children and take some responsiblity for their health and lifestyle.
Slashdot Mirror
"Many computer scientists have fallen into the trap of trying to define languages like George Orwell's Newspeak, in which it is impossible to think bad thoughts. What they end up doing is killing the creativity of programming." --Larry Wall
SPARK seems to be an extreme example. Though I've never used it, I venture to guess that in a quixotic effort to avoid all bugs SPARK only buries real bugs underneath a mountain of its own pedantry.
Talk about convex manifolds embedded in 1-logarithmic 2-space! LOL
Full stop. Why should I pay attention to the voluminous opinions of this vicarious scientist? Give me a real scientist in the field who undestands the topic from first-hand experience.
Thought so.
Interesting. You avoided my question, changed the subject, and made an out-of-context quote.
Notice the words I wrote right beforehand, which state the current problem of note. Here, I'll quote it for you--
We have a ball bouncing off the moon with enormous, escape-velocity-ish speed. (It's not really going to bounce but let's say it does.) It bounces inelastically and "straight up". How high does it go?
(In retrospect I said "inelastic" when I meant "elastic" but I assume you took the meaning.)
The past 8 posts in our discussion began with your initial refutation of my point-source assumption: "That only holds true when the gravitational body is small enough, or far enough away, to be dealt with as a point source. When you're close up, you can't do that and have to deal with messy integrations."
I stated that, no, it is mathematically correct to use point-source calculations. You then went on to say, "Christ. That's only true when the diameter of the sphere is than the distance of the object from the sphere" and "*Sigh*. You're neglecting tides."
I then spelled out, quite explicitly, how the problem should be solved using point-source calculations. I challenged you, asking how you would use "tides" in this problem. I'm basically calling you on it, because honestly it seems like you are taking lines out of a textbook without really understanding their application or their purview.
You neglected to take my challenge; you haven't told me how "tides" would be applied to the problem, or what exactly is incorrect about the point-source calculations. How would you do this problem differently?
Instead, you backed up 8 posts, asking me to show numbers regarding whether a uniform field can be used or not. By this time, however, I have already stated the problem as re-quoted above (what you neglected to quote). The key words are "escape-velocity-ish speed". I took the uniform-field-or-not issue out entirely by stating the problem in this way in order to address the point-source-or-not issue. Perhaps I lost you. But remember, you started by claiming point-source was invalid, I was merely following up.
You now wish to discuss the uniform-field-or-not topic. I would love to address this topic, however first things first. We must first agree whether a point-source calculation is valid or not. You claim it is not. I ask you again, show me how the problem should be done differently. Are you referring to such pedantry as nonuniform mass distribution? Show me specifically why the point-source calculation is wrong.
By the way, I fully expect you NOT to answer, as you have done before. But I'll wait.
Surely you don't mean I'm incorrect because I haven't factored in tidal effects? If so, that's the most pedantic thing I've ever heard. It's like if I'm explaining the parabolic nature of projectiles, you interrupt exclaiming, "You are wrong! You haven't accounted for the coriolis force due to the earth's rotation!" Coriolis effects have their purview, but we must be reasonable given the problem at hand (not to mention air is more significant).
Do you even acknowledge the theorem to which I'm referring? You seem to miss it. The first thing to do is to look it up or prove it yourself.
Part of what you are saying is true, but you miss the happy mathematical cancellations which occur in the unique situation of a sphere combined with the inverse-square relationship. With any non-spherical and/or non-inverse-square situation you must indeed perform integrations.
Now let's return to the original problem. We have a ball bouncing off the moon with enormous, escape-velocity-ish speed. (It's not really going to bounce but let's say it does.) It bounces inelastically and "straight up".
How high does it go?
I assume that you have recanted your assumption of a uniform gravitational field. It's not going to be even close to within an order of magnitude. That much is clear.
Our goal is to integrate force over distance, equating that with the kinetic energy at bounce-time.
Say the ball is 10 meters off the ground. What is the gravitational force? We do an integration (since we don't trust the aforementioned theorem) and find -- wow -- the force is the same as the force due to a point mass at the center of the moon.
Say the ball is 500 meters off the ground. We do the integration again, and whaddaya know, the force is again the same as the force due to a point mass.
It becomes clear that we can use a simple inverse-square in our force over distance integral. The result is 1/R - 1/r, where R is the radius of the moon and r is the unknown radius we seek. Put in all the constants, equate it with the kinetic energy at bounce-time and there's your answer.
Now of course the problem is grossly oversimplified. It's not going to bounce "straight" up, the earth may have a measurable effect if the velocity is large enough, etc. But it's a starting point at least.
If you don't agree with my method, how exactly would you do it? With tidal effects? Coriolis forces? What?
Not sure what your sentence is trying to say, but my statement is indeed true.
In an inverse-square relationship, there's a happy cancellation of forces which net to a single point source at the center of the sphere, no matter where you are outside the sphere.
It even works if you are inside the sphere! In this case, the gravitational pull is equivalent to a point source with mass equal to the sphere whose surface passes through you. The gravitational effect of the leftover "shell" completely cancels itself out.
Really, it's a nice theorem. Do the integration. I'll wait.
You are incorrect. It's a mathematical theorem that a sphere can indeed be treated as a point source in the case of inverse-square relationship.
Standing on the moon, you can think of all the moon's mass concentrated at a point in the center with you standing on a massless structure surrounding that point.
This makes the integration easy. Force goes as inverse-square. Potential energy goes as inverse-cube.
The uniform-field calculation is not within an order of magnitude.
But anyway, the whole thing is silly. If you assume no energy is lost during the bounce, it could conceivably bounce all the way back to earth!
In reality, it's going to plummet into the moon and make a crater. The energy will go into heat and into moving lunar soil.
The bounce would be large enough to invalidate your presupposition of a uniform gravitational field.
The gravitational field is dropping off with the inverse of the distance from the moon's center (i.e. the gravitational force going with the inverse square).
It would bounce much, much "higher".
I use fluxbox exclusively.
I find it unbelievable that you don't have this problem. I've not seen once exception in 8 years. Could you send me a message giving your exact specs please?
Thus far there have been two posts denying the existence of this problem. And I notice that I got two flamebait points.
Unfortunately I failed to mention that it's essential to open a web page with several images for the test.
I've installed linux on a variety of top-end machines over the years: from P2s with Matrox cards to P4s and AthlonXPs with GeForce4s and Radeon9800s. Each and every one has this problem.
Yes, the problem does exist. No, it's not trolling to say so.
I forgot to mention, you need to open a nontrivial web page for the test (say, http://news.google.com).
My system is nearly identical to yours. Konqueror is the worst of them all. I use Gentoo and have tried various levels of CFLAGS, all with the same effect.
This could be a great opportunity.
... sucks?
To the *nix users out there, have you ever considered that XFree86
Yes, it gets the job done. Yes, it's the most popular, it supports a plethora hardware, it is open source, etc. etc. But, all trolling aside, the thing does indeed suck.
As a longtime linux user, I can say that every single linux machine I've had, including the current latest-and-greatest, has miserably failed my Window Drag Test(TM).
To perform this test, start with a good web browser (firefox, mozilla, konqueror, galeon, whatever). Enable the equivalent of "Opaque Window Moving" on your window manager. Open a browser window and drag it to the bottom-left corner. Now drag it back. What happens? Open two windows. Drag one across the other. What happens?
What happens is smearing. Gross. Ugly. Unacceptable. Call me picky, but I don't care how much hardware you support, or how popular you are, or whatever -- if your graphical system isn't good at *drawing graphics*, then it sucks.
And this is what people notice when they first sit down in front of a linux machine. And it's killing us. Whatever the shortcomings of Windows and Macs, neither have this problem.
So this licensing issue is good news, if it can galvanize the community to pull more resources into developing alternatives to XFree86 (because it sucks!).
Perhaps I missed something, but your response appears to be a complete non sequitur.
How does counting commercial GNOME/GTK applications verses commercial KDE/Qt applications change the fact of their underlying licenses?
You must shell out lots of cash for a Qt license if you wish to distribute a commercial application for KDE/Qt. There is no such license fee for Gnome/gtk. So, in this sense, Gnome is still "more free".
Child A swims with a team for two hours a day. He eats a sensible diet. He spends a great deal of time drawing or building cool stuff with his massive lego collection.
Child B doesn't exercise. He lives on Cheetos. He's fat. He plays video games all day. His parents don't give a shit.
I have no scientific evidence in front of me, but I contend that Child A will never, ever develop ADHD.
Sure, ADHD is "real", but that's a vacuous statement. It is "really" a symptom. Child B's life is antithetical to how humans have been living on this earth for tens of thousands of years. Humans just aren't evolved to live like that -- of course something's going to happen to Child B, call it ADHD.
For God's sake stop medicating your children and take some responsiblity for their health and lifestyle.