Domain: gsu.edu
Stories and comments across the archive that link to gsu.edu.
Comments · 508
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Re:Doesn't make sense.
That's right. I used the value of the eath's diameter for its radius. Substituting half of the value in my original calculations, I come up with: 11.294 KM/s.
Also, remember that I used an upper bounds; I said that an object would fall "less than 10 meters" in 1 second, since at the end of the second it would be going 9.8 m/s^2, so even if it acccelerated constantly at the greatest speed it will reach, it will only go less than 10 meters.
More precisely, this value is:
distance = initial distance + initial velocity * time + 1/2 g times time squared.
So, d = 1/2 (9.8), or 4.9. I guess if I'd had a better conceptual understanding, I would have realized initially that after 1 second, the total displacement is just half the acceleration, since I have enough calculus to know that the derivative of a quadratic is just twice linear, and at this point we start at 0, so the graph isn't translated at all.
Anyway, if instead of 0.01 for 10 meters, I add 0.0049 KM to the original 12756 KM (now 12756/2), my answer becomes: 7.905 KM/s.
In other words, almost precisely your "8.3 km/sec or thereabouts".
So, I had just two problems.
1. I used the diameter of the Earth for its radius.
2. I did not look up the simple formula to get a more precise value than my upper bounds, and did not have the conceptual framework to quickly realize that calculation isn't necessary.
Actually, I wonder now whether my answer isn't more correct than your 8.3 km/sec...I seem to be using more precise numbers, because you're using 7000 km, whereas 12756/2 is actually 6378 KM. (And the former number comes from NASA).
Actually, now that I think about it, when I put in 14000 for 12756 in my calculations, my answer is 8.282.
In other words: Our methods produce an equally correct result.
I do wonder though why you say something like "not a bad way to do the calculation, without access to calculus." I'm in calculus 1 now, and it might be helpful if you told me what in calculus would have helped me carry out the calculations.
-Robert.
PS. It occurs to me that "7.905 KM/s" is a number I arrived at using NASA's very precise "The diameter of the Earth at the equator is 12,756 kilometers (km)" [good, apparently, to 5 significant digits] and the accepted number 9.8 m/s for g, on average.
Googling "7.905 KM/s" returns two links, the second of which says:
" See if you can show that the orbital velocity at the Earth's surface (i.e. the speed required for a frictionless train moving through an Equatorial tunnel to be in free fall all the way around the Earth) is 7.905km/s."
This page is in the webspace of Jess Brewer, who appears to be a serious researcher at the University of British Columbia.
Googling /sec instead of /s, I get a page at Purdue University reading "Thus for Earth,
vc = 7.9 km/sec (~ 5 miles/second)
(to achieve a circular orbit about the Earth)" and another (cache) by a different professor carrying out the same calculations.
Both professors are physicists.
Searching "7.90 km/s" (ie with one fewer sigfig) returns "v_cir = [ G M_E/ R_E]^{1/2} = 7.90 km s^{-1} " here. This is also an academic site.
Rounding to 7.91 returns no relavant matches, but 7.9 (as many sig. fig.s as we had from g ~ 9.8) returns too many for me to look through. Adding "orbit" I find this page says "Remember: near earth orbital velocity is 7.9 km/s." Sounds authoritative.
So you see, my calculations are quite correct. :) -
Re:farther out = more moons?
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Re:farther out = more moons?
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Re:farther out = more moons?
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Re:Very good - Binary Logic Table
> A xor A=1
Might want to re-check your math. That should be zero.
Here's a handy table to refer to which I've partially reproduced below, but in proper (ascending) binary order. You can do this enumeration to build truth tables for tertiary logic, and higher.
Notes:
1) Don't mind the table seperators - had to find some way to get around the /.'s gay lameness filter(s).
2) To lazy to fill in the names for '?' ;-)
A B | 0 N ? A ? B X R | r x b ? a ? n 1
----+ ================ ________________
0 0 | 0 0 0 0 0 0 0 0 | 1 1 1 1 1 1 1 1
0 1 | 0 0 0 0 1 1 1 1 | 0 0 0 0 1 1 1 1
1 0 | 0 0 1 1 0 0 1 1 | 0 0 1 1 0 0 1 1
1 1 | 0 1 0 1 0 1 0 1 | 0 1 0 1 0 1 0 1
0 = Hardwired to false
1 = Hardwired to true
N = AND
A = Value of A
B = Value of B
X = XOR
R = OR
And the negates in "reverse" order:
r = NOR
x = XNOR
b = Negate B
a = Negate A
n = NAND
Funny thing is, I first saw this table in one of my Logic books!
This Electronic Truth Tables describes some of the un-named ones.
Cheers
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Funny Lameness filters:
That's an awful long string of letters there.
Please use fewer 'junk' characters.
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DuhWell, duh. Tetris is based on bin packing, a classic NP-hard optimization problem. That's what makes it such a compelling game: you have to solve a really hard problem in real time.
Crispin
----
Crispin Cowan, Ph.D.
Chief Scientist, WireX Communications, Inc.
Immunix: Security Hardened Linux Distribution
Available for purchase -
So - what frequency range is the noise in?
The human ear is not linearly sensitive to different frequencies - lower frequencies ( ~10 kHz) are harder to hear. There are standard profiles - called "contours" - for measuring the output of speakers, to check how well they are adapted to the human ear.
It would be interesting to build a fan with either very large blades, or very small, that would generate low respectively high frequencies, thereby eliminating some of the perceived noise level. -
The Schwarzschild Radius
From Gsu.edu Astrophysics:
Any mass can become a black hole if it collapses down to the Schwarzschild radius ... The Schwarzschild radius (event horizon) just marks the radius of a sphere past which we can get no particles, no light, no information.
R= 2(MG)/ c^2
Therefore at 3.7 million solar masses...
the Schwarzschild radius is
1.0919401548997975x10^10 M
Which is much smaller than our solar system (the earth orbits at 150,000,000 KM).
But I imgine that they would measure the Acreation Disk.....
The Schwarzschild radius calulation is fun. One can plot density verses radius and it becomes clear that something the size of our galaxy with density of water would be a black hole...
Space is an empty place!
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Re:Yeah, fine with meto bring in actual statistics into the idea, check out the seti poll. In it they have this:
How many hours is your computer running on a typical day? (118112 responses)
Less than 24 38.26%
24, because of SETI@home 33.19%
24, but not because of SETI@home 28.56%
33% of people run their comp 24hrs just for seti. Now you were talking about "how many tons of coal are burned for seti," It has been calculated for everyone to live like a middleclass american it would take 4.2 earths. ( A similar but different idea is talked about here.) While I agree that "every little bit helps," We need to do a major change if everyone is going to be able to live at our standard.
You say how other causes are actually worthy of the "tons of burned coal" because they are much more likely to succeed and can greatly help people. Everyone that gives cycles to seti knows that the chance of finding aliens is very small, and might infact be 0, however, the gains from the discovery will be far far greater. I personally think finding larger primes or distributed.net is a waste of time, that their are more "worthy" causes, but each person has to figure out for themself what he or she thinks is important. And as you said, "As long as the people (or companies) running their programs are willing to pay the cost of running the program, I think they're great things to be contributing to." -
Re:I was lucky...One proton has a mass of 1.6726 * 10E-27 kg. Typing that into the Rest Mass Energy Calculator, that's 1.50 * 10E-10 joules.
The 730,720,000,000 anti-protons at Fermilab are thus 1096 joules (1.096 * 10E3). A gallon of gasoline has 1.3 * 10E8 joules, so Fermilab antiprotons have an energy less than 1 * 10E-5 (0.00001) gallons of gasoline.
Yes, I'm sure they used a lot more energy than that to produce those antiprotons.
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Re:I was lucky...One proton has a mass of 1.6726 * 10E-27 kg. Typing that into the Rest Mass Energy Calculator, that's 1.50 * 10E-10 joules.
The 730,720,000,000 anti-protons at Fermilab are thus 1096 joules (1.096 * 10E3). A gallon of gasoline has 1.3 * 10E8 joules, so Fermilab antiprotons have an energy less than 1 * 10E-5 (0.00001) gallons of gasoline.
Yes, I'm sure they used a lot more energy than that to produce those antiprotons.
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Re:I was lucky...One proton has a mass of 1.6726 * 10E-27 kg. Typing that into the Rest Mass Energy Calculator, that's 1.50 * 10E-10 joules.
The 730,720,000,000 anti-protons at Fermilab are thus 1096 joules (1.096 * 10E3). A gallon of gasoline has 1.3 * 10E8 joules, so Fermilab antiprotons have an energy less than 1 * 10E-5 (0.00001) gallons of gasoline.
Yes, I'm sure they used a lot more energy than that to produce those antiprotons.
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Re:a better analogy
Just in case you're not kidding Note that the length shortens with higher velocities, while the mass increases.
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Re:The most amazing website on physics...
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Re:The most amazing website on physics...
This link is valid, you just have to remove the extra space that
/. put into it. Or, if you are lazy, you can just click here. -
hyperphysics
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Re:The problemBoy, you must be a gas at parties.
A quick Google search shows that Georgia State University seem to think they are equal ("The mass of an object is a fundamental property of the object; a numerical measure of its inertia..."), and the University of Cincinati indicates that the m in f=ma represents inertia ("inertia is the resistance to changes in velocity").
If you can find a reference that claims they are not equal, I'd love to see it. In the mean time, you might want to consider lightening up a bit. You seem to have totally missed the point of my post in a misguided effort to discredit an essentially irrelevant physics analogy.
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Re:Only one kind works.
If you could come up with a final filter for the screen that converted, say, the vertical component of linearly-polarized light into right-circular and the horizontal into left-circular, you could then use circularly polarized glasses and defeat linearly-polarized. But I don't know of any physical mechanism (let alone one that could be turned into a cheap thin film) that would do this, even for monochrome, let alone the near-octave of light used by color displays or the full-octave for black-and-white.
That's easy do to. It's commonly known as quarter wave plate. Put it in front of your h and v polarized screen and rotate it to 45 degrees from h/v. It will turn h polarized in to right (or left) and v polarized into left (or right, depending on the rotation of the qw plate). See here how it works.
So stock polarizing sunglasses read all these screens, no problem.
Or just take the top plate from your old LCD pocket calculator/alarm clock/whatever. -
Re:This is good -- citations?
Uhh, I call foul to your claims.
I call foul on your figures first. Emission levels are here. The carbon emissions for a modern coal-fired plant are 263gC/kWh. You are claiming 920gC/kWh. To compare, an oil-fired plant is 213gC/kWh and a gas-fired plant is 113gC/kWh! This is one THIRD of the Mazda 626's 350gC/kWh. I expect there's a mistake in your calculations.
But the problems in your argument aren't over. You're comparing coal-fired power plants against an oil-fueled 626! Coal is a poor alternative to oil. Energy densities here. Coal is at best 31MJ/kg. Oil is at worst 41MJ/kg. Gasoline in your 626 is 45MJ/kg. These energy densities influence CO2 emissions. To use a tired cliche, you're comparing apples and oranges.
Also I call foul with your conclusion. You only compared CO2 emissions per kWh and then concluded that the EV1 has better mileage!? If you want to compare mileage then you need to use the same fuels in the two cars and the plant and concentrate on the miles travelled!
But let's do some napkin calculations to get a feeling for "mileage". The electrical transport cost of overhead powerlines is less than 10%. Motors are 95% efficient. The best gas-fired plants are now exceeding 50% efficiency. So the fuel->wheel efficiency is 43%. Even the most efficient diesel generators as used on hybrids are less than 40% efficient. Cars range between 25% and 35% with petrol. So the plants use fuel more efficiently and therefore have the better "mileage".
We can also do some napkin calculations for cost. Cost calculator here. A car will typically cost 3x more per kWh than the plant. This is because plants get huge economies of scale and use much cheaper fuels. Cost alone proves nothing but combined with my previous arguments it proves that purely electric vehicles - not hybrids - are the best choice.
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I like the Pound-Rebka Experiment
They dropped photons off the roof of a building and measured their blue shift at the bottom, confirming general relativity. One description of the experiement is here.
Pound is an interesting guy. He experimented with using microwaves to heat people instead of wasting energy heating entire buildings. He tested it out by rigging his microwave oven to operate with the door open. He told me that he had to bypass three interlocks, but that he got it working: there was a nice warm glow, like standing in front of a campfire.
Needless to say, don't try this at home unless you're a damn competent physicist. -
Ted Taylor also talked about Orion to John McPhee
You can also read about Project Orion in John McPhee's book The Curve of Binding Energy . This book is mostly a long conversation between McPhee and Ted Taylor, (more) a physicist and ex- nuclear weopons engineer. In the early 70's Taylor becomes worried about how easy it is to build a fission bomb. Taylor and McPhee drive around and survey the security of nuclear materials while Taylor talks bomb theory and practice. The title comes from the curve on this page.
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Re:Reminds me of...
...use the electron's spin (+half or -half) to store the same
... informationDoesn't the Pauli Exclusion Principle limit this seriously? After all, in every atom (of a given element), each electron must have certain preoccupied states... The only way to convey information by using ions (i.e. less, or more electrons for the same atom); and keeping electrically imbalanced material is a bit more difficult...
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Re:10000 years
Excuse me?
Actually half the reason we have as much waste as we do is because of the moratorium on breeder reactors. The U-238 (nuclear waste/depleted Uranium) coming out of traditional Light Water Reactors can be used in Breeder Reactors to generate more power (and reducing the need to store waste materials). This end product of the process, however, is weapons grade Plutonium-239 and some more U-238 (a smaller amount of U-235 is required as an initiator for the reaction).
http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/ fasbre.html
What alarmists also fail to note is that the resulting Plutonium can be used to fuel yet another form of nuclear reactor. Plutonium Pellet based reactors are not only very efficient, but also one of the safer forms of reactor.
Unfortunately concerns about both weapons grade and reactor grade plutonium (the latter produced in small amounts by standard reactors) being potentially used in nuclear weapons has prevented the widespread construction of breeder reactors and a number of moratoriums for such projects came into being.
Most of the problems occurring in areas such as Iraq caused by depleted uranium dust are related to children ingesting it from untreated drinking water that has become contaminated by UN/NATO forces spent ammunition.
The "military" aspect is also at the root of the public's biggest misconception about plutonium; that the radiation off of plutonium is the "strongest". Plutonium in fact gives off mostly alpha particles which can be stopped by shielding as weak as a piece of normal writing paper or the layer of dead skin cells that covers your body.
Plutonium is however very toxic and radioactively hazardous if ingested or placed on open wounds/etc.
http://www.vnh.org/BUMEDINST6470.10A/Plutonium.htm l
Something else that bothers me about everyone screaming bloody murder over the Yucatan and similar storage facilities is this bizzare belief by people that these materials are somehow magical evil concoctions that were given form in a lab. Most people honestly do not understand that uranium is mined from the ground like any other ore. And that the danger posed by nuclear waste is less one of radiation than of toxicity (radioactive damage stems mainly from consumption or absorbtion into the bloodsteam). The concept of shorter half-lifes being more radioactive also seems to elude people.
You are in far far more danger from walking into your house then you are from nuclear storage.
Most people in the US that are getting into a panic over relatively safe nuclear materials being stored in secure facilities many miles away are not even aware of how near they live to a superfund site. Most superfund sites revolve around heavy metals and other exceedingly toxic substances and are far more common than people think.
Nuclear power is (right now) one of the cleanest and safest power sources available. Too many people are stuck in some sort of a terrified cold war stupor and have been failing to do enough research.
And everyone reading this has to go read Zodiac -
Re:Better in space?
Optical aperture synthesis is working quite well from the ground at specialist observatories. COAST gets fringes from 5 telescopes and synthesises a baseline of 67m, while CHARA has achieved fringes from 2 telescopes separtaed by 400m. It has 6 telescopes in all. The combination of beams is, however, not done in software because we don't have instruments capable of recording the detailed phases of a beam of light, as can be done in the radio. All these optical interferometers use light pipes and mirrors on trollies to match path lengths and to directly combine the beams of light coming from the sub-telescopes.
The key with these projects though is that they all use small sub-telescopes, so can only observe fairly bright objects. Still, it can give you images of the surface of a star like Betelgeuse.
Getting to fainter objects means going to larger apertures for the sub-telescopes, and that brings problems. With the small telescopes the wavefront across them is affected in the same way by the atmosphere, so things are coherent when they're combined. With a large aperture (like the VLT primaries at 8m) the wavefront is not the same across the mirror, so this needs to be corrected before the individual telescopes can be combined. This is a major sticking point that has taken a long time to sort out. The corrections needed still limit these systems to quite bright obejcts, though. -
Re:Why don't superconductors weigh less?It's been a long time since I did this (1988), but in my senior year of high school a couple friends and I made a superconductor with our physics teacher. With it we successfully reproduced magnetic levitation via the Meissner Effect: "If a small magnet is brought near a superconductor, it will be repelled becaused induced supercurrents will produce mirror images of each pole. If a small permanent magnet is placed above a superconductor, it can be levitated by this repulsive force."
Thus, the superconductor is not affecting the gravitational field. It is in a sense becoming a magnet itself, producing an exact-opposite magnetic field. This new field simply repels the magnet, producing levitation. By far the coolest effect was spinning/flipping the magnet over the superconductor and having it remain levitated, as the superconductor's magnetic field was always a mirror of the magnet's.
Now, in this I am not talking about the article or paper (I just started reading it). I'm simply talking about the magnetic field that is induced in a superconductor by magnets. My only experience and knowledge of the subject was the experiment in high school.
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Re:Why don't superconductors weigh less?It's been a long time since I did this (1988), but in my senior year of high school a couple friends and I made a superconductor with our physics teacher. With it we successfully reproduced magnetic levitation via the Meissner Effect: "If a small magnet is brought near a superconductor, it will be repelled becaused induced supercurrents will produce mirror images of each pole. If a small permanent magnet is placed above a superconductor, it can be levitated by this repulsive force."
Thus, the superconductor is not affecting the gravitational field. It is in a sense becoming a magnet itself, producing an exact-opposite magnetic field. This new field simply repels the magnet, producing levitation. By far the coolest effect was spinning/flipping the magnet over the superconductor and having it remain levitated, as the superconductor's magnetic field was always a mirror of the magnet's.
Now, in this I am not talking about the article or paper (I just started reading it). I'm simply talking about the magnetic field that is induced in a superconductor by magnets. My only experience and knowledge of the subject was the experiment in high school.
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Re:New Scientist Article
Thanks for the clarification! I scoured the web for the real journal article but didn't find it. I did find an abstract for one of the 1993 papers you mentioned, so I wondered about the mass discrepancy. Better luck helping reporters get it straight in the future. Take their presence as a sign that your work is interesting to lay people.
Since I'm a little rusty, I dug up some articles about type I and II supernovae, and white dwarves and the Chandrasekhar limit. I also found a stellar who's who which says HR 8210 is IK Pegasi, at RA 21h26m Dec +19.3. My Sky Atlas 2000.0 shows a 6th-magnitude star there, but it's not marked.
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Re:Here is anouther solution for you.
the L-R channel is broadcast on a 34 KHz subcarrier.
A slight correction: It is 38kHz, see second box down. But who is counting. This makes sense as it is pretty easy to frequency double the 19kHz pilot and demodulate the L-R subband.
The site also claims that the channels are only 15kHz. Elsewhere I have seen claims of 17, 18, and even 19 kHz. -
Re:Talking at work
I'm bored, so I'm going to keep you honest.
:)
Actually, quantum physics does imply there are a finite number of states. Time, space, energy, motion, even Heisenberg's uncertainty are all descreet, quantisized values.
We thus have a system with an upper and lower limit on where the electron can be at any moment, and what vectors it may have. This means there is a finite number of possible states that can exist, and while that number is impossibly huge to contemplate, it is not infinite.
But 'discrete' and 'finite' and 'bounded' are not the same thing.
Counterexample: Consider the available electron energy states of Hydrogen. Discrete? Yes. Bounded? Yes. Finite? No - the energy levels (n>0) go like -1/n^2. COUNTABLY infinite, but definitely infinite. The electron can always be pushed into your favorite higher energy state (asymptotically approaching the ionization energy) by absorbing a photon of the right frequency.
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What about the Hall effect?
One really cool old experiment was when Hall showed that if you take a strip of metal in a magnetic field and send current through it, there will be a voltage difference between the two sides of the strip. Based on only this, it was determined that the charge carrying particle in "electricity" is the electron. It might not be quite as cool as Millikan's oil drop experiment, but it shows something mind-bogglingly fundamental with an extremely simple apparatus.
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Hogwash!
Evidently, the something-for-everyone model epitomized by Heathkit and the Amateur Scientist column can't compete anymore. Specialized sources and Internet newsgroups cater to each skill level. But much of the mentoring and serendipity that the diverse community of amateurs offered has been lost. It is hard not to regret its passing.
What an idiot. We have just largely stopped using magazines in light of the Internet.
I've learned almost everything I know about electronics from the Internet.
Look at these books! Look at them! All Free, as in Liberty AND No-Cost. These are some of the very best books I have found on electronics, on-line or off. Forest Mims the Third, eat your heart out.
Do we want to talk about mentoring and serendipity?
It was out of frustration that I compiled Lessons in Electric Circuits from notes and ideas I had been collecting for years. My primary goal was to put readable, high-quality information into the hands of my students, but a secondary goal was to make the book as affordable as possible. Over the years, I had experienced the benefit of receiving free instruction and encouragement in my pursuit of learning electronics from many people, including several teachers of mine in elementary and high school. Their selfless assistance played a key role in my own studies, paving the way for a rewarding career and fascinating hobby. If only I could extend the gift of their help by giving to other people what they gave to me . . .
There you go.
If anything, I'd say that amateur science and learning and construction is more popular now, because it is more accessible.
It just doesn't take the form of magazine articles.
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Re:Liar!
We've known that light can slow down since 1850. The speed of light does change when traveling through various things, depending on its index of refraction. So, you are not correct -- light can be and is slowed down easily.
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Re:no way
Uh, you're serious? Your post sounds like you're serious... but to actually believe that... well, I don't want to be insulting...
Anyway, there are lots of benefits of exercise.
Here's some info, gathered from a Google search:
http://www.csmngt.com/ABenefits.htm
http://www.gsu.edu/~wwwfit/benefits.html
So if you still think that exercise isn't important or valuable, I would guess that you're experiencing denial.
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Re:Whay can't this be done on a planet scale?
Ah, ha! I found it
:-)
See the CHARA site here -
This was patented 20 years ago
Someone seems to have had remarkable foresight, patenting this 20 years ago. They proposed the use of liquid metal though, as I guess it would carry the heat away better (as in fast breeder reactors)
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Re:Oh God NOOO!!! The /. interface for this sectio
Yah but unlike MacOS it is not shipped as part of the system unless I want it to be.
I also do not plan on BUYING WinXP.
Hell I refuse to even PIRATE it.
I am that f*cking opposed to blue curvy shit.
I actualy don't care WHAT color it is. It is the curvy shit part that gets to me. That and the pseudo-transparency.
Oh, and by the way. The base color of the fade is color is r21, g105, b103.
By comparison, slashdot by default uses r0, g102, b102 (which is close, the curvy thing has r8, g102, b103 on its upper left curved boarder).
r0, g102, b102 is obviously equal parts green and blue though.
Mabye the blue amplifier[1] in the brains of these AC respondants are outa synch?
[1] may be bullshit, just found that link a few minutes ago. :) -
Some useful links......for people who are wondering what this is all about:
- The CIE color space: A pretty decent introduction to what the CIE color space is
- Color FAQ: I haven't read through this, but it seems to be a more extensive coverage of color and how it's much more than RGB, HSV, or CYMK.
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More jokes
Further jokes (including the ones above, I'm guessing this is where the poster got them) are here.
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Re:Billions and billions...
I too had a recent revelation.
Given the local density of the universe, there should be around 100 star systems within 20 lightyears of the Earth. In fact, we've already identified 76 such star systems. For those that are interested this site lists the closest 26 stars (as opposed to star systems, which might be binary, trinary, etc.). There is also a more technical listing of the 100 closest known star systems (out to 24 lightyears).
Expanding away geometrically there would be about 1,700 star systems within 50 lightyears, and 13,000 within 100 lightyears. Fact of the matter is we don't even know which stars most of these are, since the majority of stars are relatively small and small stars rarely have their distance calculated.
If we ever do figure out how to get up close to light speed, then there is plenty of real estate to explore. Hell, if it turns out that life really is quite common, then maybe little green men actually can afford to come visit us. -
Re:Delays due to molecular friction?
The electrons move (as a result of an applied voltage) at what is known as the drift velocity. A example in copper is also available.
Current doesn't stop (your "current move, current not move" parenthetical). Current is not a thing, but is a description of a situation: moving charge is a current. An Ampere is defined as one Coulomb of charge passing a reference plane in one second.
How fast a signal propagates down a wire is its group velocity.
The "friction" mentioned by the original poster I interpret to be a flawed understanding of how resisivity works. Electrical signals travelling through resistive materials are attenuated, not slowed down, due to the resistance. Changes in velocity are due to changes in the dielectic constant. -
Re:Delays due to molecular friction?
The electrons move (as a result of an applied voltage) at what is known as the drift velocity. A example in copper is also available.
Current doesn't stop (your "current move, current not move" parenthetical). Current is not a thing, but is a description of a situation: moving charge is a current. An Ampere is defined as one Coulomb of charge passing a reference plane in one second.
How fast a signal propagates down a wire is its group velocity.
The "friction" mentioned by the original poster I interpret to be a flawed understanding of how resisivity works. Electrical signals travelling through resistive materials are attenuated, not slowed down, due to the resistance. Changes in velocity are due to changes in the dielectic constant. -
Re:Nature never fails to amaze meFission has happened in nature too...
Basically, about 1.8 billion years ago, an area of africa containing Uranium 235 fissioned (?is that a word?) naturally, over a period of around a million years.
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Re:BuckyballsAccording to this article [physicsweb.org], buckyballs hold the record for highest-temperature superconductor.
Small correction. The article says that C-60 is non-copper-oxide superconductor with the highest transition temperature.There are high-Tc superconductors with transition temperatures way higher than that. Strange quaternary alloys (YBCO, or Yttrium-Barium-Copper-Oxide, is probably the most common) where the ratios of components must be just right are some of the highest transition temperature SC's. The highest transition temperatures, IIRC, occur around 150K or so. This is good news because liquid nitrogen temperature is 77K, which is cheaper than milk in bulk quantities. Thus, for some superconducting applications, you don't need expensive 4K liquid Helium refridgerators, but can make use of a dewar filled with cheap liquid nitrogen.
Here is a link with various copper-oxide superconductors described.
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Re:Oh man
So what pray tell is the half life of a neutron?
About 10 minutes. HTH. -
500,000,000 volts at 10,000 amps
A lightning discharge is perhaps 500,000,000 volts at 10,000 amps.
Interesting references:
Great Lightning Photos -- West Virginia Lightning
Frequently Asked Questions (FAQ) about Lightning
Human Voltage -- What happens when people and lightning converge
Lightning Concepts -
Inverse Square LawYes, light does obey the Inverse Square Law. A laser does not because the light has been manipulated to make the photons travel parallel to each other, thus it does not "spread its influence equally in all directions". A laser is following the geometry applicable to parallel lines (depending upon accuracy of construction), not a sphere.
Any point source which spreads its influence equally in all directions without a limit to its range will obey the inverse square law. This comes from strictly geometrical considerations. The intensity of the influence at any given radius r is the source strength divided by the area of the sphere.
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Re:OK, so...
Actually neutrinos are generated and escape the supernova well ahead of the photons (the internal process of a supernova is quite complex, and stars are *HUGE*), and the photons never do catch up. (ref-1) (ref-2)So, neutrinos can actually provide early warning*about a supernova. Light from SN1987a was in fact preceeded by neutrionos that arrived 18 hours ahead of time (ref-1) (ref-2).
Here is a really good page (among a bunch) that explains supernovae.
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Counterpoint
For one, it doesn't matter how many CDs you purchase a year it doesn't justify pirating ANY amount of other music.
Why is is that "music piracy" is so reviled as an evil action while the actions of the music industry, one of the most immoral industries out there (next to the software industry) is hailed as "providing a valuable service"?
Sure, CDs are overpriced and that's not good but you are still depriving the artist of their well deserved income. Buying 30 CDs a year doesn't mean anything to an artist whos CD you -didn't- buy.
Artists do not have a right to make money, much like corporations do not have a right to profit.
Without the RIAA, how the hell would any amount of artists got where they are today?
This is an ad crumenam argument.
All governing bodies have some amount of evil, and it's easy to overlook the good when all you care about is what they are depriving you of (free music).
I believe that music, like software and information, should be free. How much do you charge for something that can be duplicated infinitely at nominal cost?
What makes you think that Micorosoft should give away upgrades to their software, simply because you personally gauge the price to be too high? I know it's a fair whack, but to think that you are getting all that product (consider the developer's time that went in to making this stuff) and you just think you are welcome to free upgrades? Try that at your local car dealer...(I hate to use that analogy.. but everyone else seems to relate to it all the time...). And then, you go on to say that WPA is not a bad thing and it's Microsoft's right to include it. Two faced?
Not at all. Microsoft is a monopoly. They have to play by different rules.
Everyone's entitled to an opinion I guess, but this is clearly just a college kid that's pissed he doesn't get enough pocket money. Hardly ground breaking news Tim.
Yes. Opinions are like assholes: everyone has one, and they all stink. But there are larger issues at work here, work like monopoly power and freedom. This is hardly about poor college kids whining about not getting free stuff. -
Re:huhIt's not a troll -- it's more truthful than you think. See here
(not a goat sex link)
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Save the Bonobos