Nope. I was merely supporting the tangent topic which was presented before me, and then starting another tangent topic that was merely trying to be informative from a physicists point of view. It was all sort of tangent to the article at hand.:)
Physics papers aren't just published all willy nilly. They must be reviewed by other physicists. Also, most theorists don't work alone, but instead work in a group, so there are checks and balances going on there.
I do admit, however, that theoretical physics seems harder and harder to understand. Newton's laws are far more simple to do calculations with than Relativistic Dynamics. And Newtonian Gravity seems far more simple than General Relativity. And then you have Quantum Mechanics, Quantum Field Theory, and now String Theory (which is full of unsolvable differential equations).
However, just because the mathematics and principles involved are harder to understand, doesn't mean that they are hoaxes. Indeed, despite the computational and conceptual difficulties involved in General Relativity (to which I find the conceptual difficulties fairly easy to overcome, but to which the math to solve a problem seems to take forever), the theory works far better for extreme conditions than its predecessor.
Before I conclude, I would like to point out that there is a difference between computational difficulties and conceptual. Many modern theories take very difficult mathematics to solve even seemingly simple problems. However, to build a loose conceptual notion of of, say, General Relativity, is fairly easy, given some experience with problems. I usually find it a lot easier to understand the concepts of a newe theory, and then trust that the theorists are honestly doing the math in in effort to show that the theory pans out as compared to the real world.
I've babbled on long enough; it's just my two cents as a Physicist.
Oop, If I had read farther, I would see that someone posted a link to something discussing this briefely. Furthermore, the article says the the 2.4m Hubble mirror can resolve to about 80 meters at 400,000.
But, to finish off this thread of discussion: The angular resolution (theta) of a telescope with a main optic of diameter D, at a wavelength lambda, can be found by the following equation: theta = 1.22 (lambda/D)
In this case, lambda is about 550nm (most significant for human vision), and D is 2.4m. This gives a theta of around 2.8E-7 radians.
Now, tan( theta ) = w/r. (In this case, w is the width of smallest resolution, at a distance r). Since theta Since the mean radius out to the Moon is about 384,400km, we find that the maximum resolution is 107m.
My answer of 107 meters isn't too far off of the 80m I had quoted. In fact, this is quite good for a back of the envelope calculation.
Anyway, if people care, this is how this sort of things is done.:)
If I remember to come back by later, I'd like to know where you got the Hubble specs, and I'd like to see what kind of figures you got (and what basic formulas you used). I'll try to then verify it (if I get the time).:)
The only problem is that the speed of sound is *significantly* slower at higher altitudes. And at 17,000 miles, where the air is so thin, I have no idea how much slower it is, but I wouldn't be surprised if it was by a factor of 2 or 4. But, on the other hand, this means that the Mach number can be *no less than 26*.:)
-Jeff
P.S. - The speed of sound at sea level, with it being 20 degrees celsius, is 343 m/s, which is 767 mph. So you already (accidently) took into account the slower speed of sound a little, but this is the speed of sound around 40,000 feet. , so I would expect it to be smaller:)
Don't forget that the speed of sound is a function wich, among other things, is a function of ALTITUDE.
Now, the speed of sound at sea level is around 340m/s, which gives us around 11.7g's of acceleration, and an altitude of 42,000 feet in 15 seconds.
However, the speed of sound at that altitude is significantly slower, around 290m/s-300m/s (according to my information), so our numbers for the acceleration should be a bit HIGH.
Of course, without a nice function for me to integrate against, it is a little trickier to figure out what the acceleration really is, but we can put some bounds on it. As determined, the upper limit is 11.7g's of acceleration. The lower limit will be around 10g's. (This is found by using the slowest speed of sound number that we could possibly run across).
So, with that range in mind, we can see that a reasonable estimate for the acceleration would be about 11g's +/- 1g.
There, I feel more rigorous. I feel better now.:) (This is what I get for being a physicist.)
Mmm, doesn't matter. In the past I've usually been quite constructive. Although I sorta thought my original post, besides the title, wasn't *bad*. Guess I attracted too much attention to myself. (Score 0, Troll, I know.):)
Yeah, it is pretty much dead, but not entierly. There are a few die hards still working on coding the occasional utility upgrade for it, and I still have my semi-popular site up. But all in all, it has sorta disappeared.
Great game though. I would love to see it ported to OS X. But, alas, Stu has no time for Bolo anymore.:(
Not better compression. PNG is the replacement to GIF, which is a lossless compression. JPEG is lossy. JPEG works really well on photos, but PNG and GIF are better suited towards computer generated graphics; things with a limited colour palette.
I graduated from UCSB about a year ago. Here are the things I found absolutely invaluable: +PDA - I never could have remembered all those damned assignments, special meetings, and so forth, not to mention the contact information for professors, staff, and friends (which seemed to change every month). +Little Screwdrivers - I had a set of Jewelry screwdrivers which were *really* helpful. (I almost picked my bedroom door lock with just those!) Of course, hammers, wrenches, and pliers are also needed. +Lock Picks - As mentioned, I tried to pick my lock using jewelry screwdrivers. A lock pick set would have been nice. Although it was mostly to satisfy my urban exploration cravings.:)
Haha. Like the time I was at UCSB, and there was a quake (can't remember how big, but it seems like it was a 5) right off the coast. I woke up to my bed shaking. I rolled over and fell asleep again before the thing ended.
We have this. We used to be paying around $60/mo for our 144k DSL (with additional IPs for all of our computers). This was the best we were able to have for a long time, because the phone lines on our hill are too old (think Oakland hills, and built in the early 60s). But now with Wireless DSL, we get insanely fast connections at something close to this price. I can get almost T1 bandwidth, on a good day.
The antenna is small and round, and is so invisible on our roof that I had to look for where it was installed.
Our reception is super good, so other's mileage may vary. We live behind wirless DSL antennas (which are on top of our neighbours house), so we get good reception no matter what direction our antenna is pointing.:)
Apple has it all figured out. They know it is 5GB, and they are sticking with that. In fact, this is the ONLY place I've seen it labelled as 10 Gig. I mean, geez, just 'cuz one guy can't count, don't blame it on Apple.
Not that I'm much in the habit of reading liscence agreements, but don't they usually have a printed version in the box, and if you read it and decide to disagree, you can return the software (maybe only to the manufacture itself) for a full refund?
I do have one use for noisy fans: As a college student, there is always a lot of noise emminating from the houses around me. Thank god (if I believed in him) for "white" noise. The volume of the fans drowns out everything except the loudest noises (like a party next door). It also drowns out people watching TV too loudly in the next room, and, when I had a room mate, his heavy breathing.:)
Granted, whenever I want to record audio through a microphone, then I get this hum in the background. All in all, however, the noise has served me well. I even usually leave on my external CD-ROM burner (mounted in an old case with a really noisy fan), just to generate more white noise.
(Oh, and don't call me crazy just because I find the hum of my computer's fans comforting).
Acceleration and Special Relativity...
on
E=MC
·
· Score: 1
OK, before I start, I will say that I'm working in Astrophysics. I have taken multiple General Relativity classes, and read many difficult books on the subject. I've even taught special relativity.
OK, here is how it goes. SPecial relativity is done in flat space time. As you are taught in beginning classes, you are limited to NO accelerations. However, when you take a more advanced course, they develop the idea of an instantaneous rest frame, and how you can use an integral over proper time to work with this acceleration. Granted, since gravity is not a force (in the GR picture it results from an extremum path in spacetime), we can't use this idea of acceleration for calcualtions.
For people that disagree, they obviously haven't taken more than special relativity for engineers. It isn't meant as an insult, mearly to let you know your place.;)
Slashdot Mirror
Nope. I was merely supporting the tangent topic which was presented before me, and then starting another tangent topic that was merely trying to be informative from a physicists point of view. It was all sort of tangent to the article at hand. :)
-Jeff
Physics papers aren't just published all willy nilly. They must be reviewed by other physicists. Also, most theorists don't work alone, but instead work in a group, so there are checks and balances going on there.
I do admit, however, that theoretical physics seems harder and harder to understand. Newton's laws are far more simple to do calculations with than Relativistic Dynamics. And Newtonian Gravity seems far more simple than General Relativity. And then you have Quantum Mechanics, Quantum Field Theory, and now String Theory (which is full of unsolvable differential equations).
However, just because the mathematics and principles involved are harder to understand, doesn't mean that they are hoaxes. Indeed, despite the computational and conceptual difficulties involved in General Relativity (to which I find the conceptual difficulties fairly easy to overcome, but to which the math to solve a problem seems to take forever), the theory works far better for extreme conditions than its predecessor.
Before I conclude, I would like to point out that there is a difference between computational difficulties and conceptual. Many modern theories take very difficult mathematics to solve even seemingly simple problems. However, to build a loose conceptual notion of of, say, General Relativity, is fairly easy, given some experience with problems. I usually find it a lot easier to understand the concepts of a newe theory, and then trust that the theorists are honestly doing the math in in effort to show that the theory pans out as compared to the real world.
I've babbled on long enough; it's just my two cents as a Physicist.
-Jeff
I think the question is: :)
How many people didn't?
-Jeff
P.S. - The stains, oh the stains.
Haven't I heard this joke a couple times before?
But, to finish off this thread of discussion:
The angular resolution (theta) of a telescope with a main optic of diameter D, at a wavelength lambda, can be found by the following equation:
theta = 1.22 (lambda/D)
In this case, lambda is about 550nm (most significant for human vision), and D is 2.4m. This gives a theta of around 2.8E-7 radians.
Now, tan( theta ) = w/r. (In this case, w is the width of smallest resolution, at a distance r). Since theta
Since the mean radius out to the Moon is about 384,400km, we find that the maximum resolution is 107m.
My answer of 107 meters isn't too far off of the 80m I had quoted. In fact, this is quite good for a back of the envelope calculation.
Anyway, if people care, this is how this sort of things is done.
If I remember to come back by later, I'd like to know where you got the Hubble specs, and I'd like to see what kind of figures you got (and what basic formulas you used). I'll try to then verify it (if I get the time). :)
So now this begs the question: Is the performance loss due to emulating AltiVec outweighted by either the higher clock speeds of the Intel chips?
-Jeff
The only problem is that the speed of sound is *significantly* slower at higher altitudes. And at 17,000 miles, where the air is so thin, I have no idea how much slower it is, but I wouldn't be surprised if it was by a factor of 2 or 4. But, on the other hand, this means that the Mach number can be *no less than 26*. :)
:)
-Jeff
P.S. - The speed of sound at sea level, with it being 20 degrees celsius, is 343 m/s, which is 767 mph. So you already (accidently) took into account the slower speed of sound a little, but this is the speed of sound around 40,000 feet. , so I would expect it to be smaller
Now, the speed of sound at sea level is around 340m/s, which gives us around 11.7g's of acceleration, and an altitude of 42,000 feet in 15 seconds.
However, the speed of sound at that altitude is significantly slower, around 290m/s-300m/s (according to my information), so our numbers for the acceleration should be a bit HIGH.
Of course, without a nice function for me to integrate against, it is a little trickier to figure out what the acceleration really is, but we can put some bounds on it. As determined, the upper limit is 11.7g's of acceleration. The lower limit will be around 10g's. (This is found by using the slowest speed of sound number that we could possibly run across).
So, with that range in mind, we can see that a reasonable estimate for the acceleration would be about 11g's +/- 1g.
There, I feel more rigorous. I feel better now. :) (This is what I get for being a physicist.)
-Jeff
Mmm, doesn't matter. In the past I've usually been quite constructive. Although I sorta thought my original post, besides the title, wasn't *bad*. Guess I attracted too much attention to myself. (Score 0, Troll, I know.) :)
Follow-up: Dang... someone beat me to it... took too long typing. :)
Without buttons... hmm... that makes it difficult. You need some sort of actuator. And I suppose telepathy is out of the question? :)
Yeah, it is pretty much dead, but not entierly. There are a few die hards still working on coding the occasional utility upgrade for it, and I still have my semi-popular site up. But all in all, it has sorta disappeared.
:(
Great game though. I would love to see it ported to OS X. But, alas, Stu has no time for Bolo anymore.
Not better compression. PNG is the replacement to GIF, which is a lossless compression. JPEG is lossy. JPEG works really well on photos, but PNG and GIF are better suited towards computer generated graphics; things with a limited colour palette.
I graduated from UCSB about a year ago. Here are the things I found absolutely invaluable: :)
+PDA - I never could have remembered all those damned assignments, special meetings, and so forth, not to mention the contact information for professors, staff, and friends (which seemed to change every month).
+Little Screwdrivers - I had a set of Jewelry screwdrivers which were *really* helpful. (I almost picked my bedroom door lock with just those!) Of course, hammers, wrenches, and pliers are also needed.
+Lock Picks - As mentioned, I tried to pick my lock using jewelry screwdrivers. A lock pick set would have been nice. Although it was mostly to satisfy my urban exploration cravings.
Haha. Like the time I was at UCSB, and there was a quake (can't remember how big, but it seems like it was a 5) right off the coast. I woke up to my bed shaking. I rolled over and fell asleep again before the thing ended.
We have this. We used to be paying around $60/mo for our 144k DSL (with additional IPs for all of our computers). This was the best we were able to have for a long time, because the phone lines on our hill are too old (think Oakland hills, and built in the early 60s). But now with Wireless DSL, we get insanely fast connections at something close to this price. I can get almost T1 bandwidth, on a good day.
:)
The antenna is small and round, and is so invisible on our roof that I had to look for where it was installed.
Our reception is super good, so other's mileage may vary. We live behind wirless DSL antennas (which are on top of our neighbours house), so we get good reception no matter what direction our antenna is pointing.
Apple has it all figured out. They know it is 5GB, and they are sticking with that. In fact, this is the ONLY place I've seen it labelled as 10 Gig. I mean, geez, just 'cuz one guy can't count, don't blame it on Apple.
Not that I'm much in the habit of reading liscence agreements, but don't they usually have a printed version in the box, and if you read it and decide to disagree, you can return the software (maybe only to the manufacture itself) for a full refund?
I do have one use for noisy fans: As a college student, there is always a lot of noise emminating from the houses around me. Thank god (if I believed in him) for "white" noise. The volume of the fans drowns out everything except the loudest noises (like a party next door). It also drowns out people watching TV too loudly in the next room, and, when I had a room mate, his heavy breathing. :)
Granted, whenever I want to record audio through a microphone, then I get this hum in the background. All in all, however, the noise has served me well. I even usually leave on my external CD-ROM burner (mounted in an old case with a really noisy fan), just to generate more white noise.
(Oh, and don't call me crazy just because I find the hum of my computer's fans comforting).
OK, before I start, I will say that I'm working in Astrophysics. I have taken multiple General Relativity classes, and read many difficult books on the subject. I've even taught special relativity. OK, here is how it goes. SPecial relativity is done in flat space time. As you are taught in beginning classes, you are limited to NO accelerations. However, when you take a more advanced course, they develop the idea of an instantaneous rest frame, and how you can use an integral over proper time to work with this acceleration. Granted, since gravity is not a force (in the GR picture it results from an extremum path in spacetime), we can't use this idea of acceleration for calcualtions. For people that disagree, they obviously haven't taken more than special relativity for engineers. It isn't meant as an insult, mearly to let you know your place. ;)