Is it true that the original nebula images are black & white, and colored afterwards to look prettier?
That's true, in a sense, but a misleading way of putting it. It's not as if the people at Space Telescope are pulling out their Crayolas.
The electronic detectors (CCDs) on HST, as on virtually all professional telescopes, are inherently monochrome detectors. During an exposure, the detector is behind one of several filters. There are filters that pass UV light, blue light, green light, red light, infrared light, etc. In many cases, the same bit of sky is observed in multiple filters, one after the other. If these happen to be red, green, and blue filters, you can put the three images in the red, green, and blue channels of a color image, and get something that's approximately true color. The filters are not designed to exactly mimic the human eye's color response; that's not an important concern from a scientific standpoint. If some other combination of three filters is used, they can still be placed in the RGB channels of an image, but the result will be a false-color image. That doesn't mean the color information is meaningless; parts of the nebula that look "blue" in the image probably have something physically different happening than parts that look "red."
Many people have an unrealistic expectation that colors in astronomical images should be exactly correct. That's a hard thing to nail down. As I mentioned above, the filters are not designed for human-vision color fidelity, since that's not relevant to the scientific goals at hand. Also, if you look at a nebula with your eye, even through a very large telescope, you vision will be dominated by the color-insensitive rods, and the nebula will appear quite washed-out. So do you want the publicity pictures to mimic this shortcoming of human vision (that we don't see much color in faint things)?
Back to the topic of the CCDs being monochrome detectors: This is true of the CCD or CMOS detectors in consumer digital cameras, too. But instead of putting the whole detector behind a colored filter, each pixel on the detector is behind a tiny red, green, or blue filter. Thus, each detector pixel is still only recording one of the three colors of light. (The new Foveon chips are an exception to this rule.)
Judicial activism has nothing to do with unconstitutional laws. It has to do with a judge considering a law "wrong" or "harsh" even though it _IS_ Constitutional.
Then there's at least 20,000 people using the term incorrectly, since this recent example was based on a (state) constitutional argument.
Judicial activism is where a judge ignores the law and just rules based on how they wish the law was. That's wrong.
It's not necessarily wrong; there are state and federal constitutions, to protect the populace from bad laws. The ability of the judicial branch to overturn unconstitutional laws is an important part of "checks and balances."
What, it's not? I mean, at least "their half" of the Earth is, isn't it? The other half would be further away, thus the total movement (towards/away from the sun, at least -- not around it) of the Earth would be roughly zero, but in a local sense, they are right.
You appear to understand, correctly, that the seasons arise from the tilt of the earth's axis, and that when it's summer in your hemisphere, your hemisphere is tilted toward the sun.
But that's not an important effect as far as the distance to the sun goes. The earth's orbit is slightly elliptical, with the sun at one focus of the ellipse. So there's a time of year when the earth is closest to the sun, and a time six months later when it's more distant. The difference in these distances, due to the shape of the orbit, is much larger than the difference in distance that arises from the earth's tilt. The earth is closest to the sun in January, and farthest in July. The difference is about 3 million miles, which is obviously a lot larger than the earth's diameter, and so clearly much larger than the effect of the tilt. Since the whole earth is closest to the sun in January, but the northern and southern hemispheres are in opposite seasons, clearly it is not the distance that's determining the season.
The tilt determines the season by making the sunlight fall more directly (more nearly vertically) and for a longer time each day during the summer.
In english, regular plurals are made by adding an -s on the end of a word, or -es if it ends in an s already. I suppose you want us to learn Latin just so we can use "medium" correctly in all cases.
So, are you cloaiming that all English plurals are regular? Or that "media" is such an obscure word that one must have studied Latin to know of it?
Some women do not understand that there is no substance anywhere in the world, synthetic or natural, that has the extremely effective skin-softening and gravity-defying effects of your love juices.
In the article it says that GPS would not be possible without the use of Relativity Theory.
Why is this?
Various reasons, including graviational redshift (or blueshift), due to the satellites being higher in the earth's potential than the receiver. Here's an overview.
Until quite recently everyone thought that CMOS was too noisy to generate really first rate pictures, but the Canons are very competitive with CCD-based SLRs.
My favorite part was about how the photographer exposed "only" 200 rolls worth of pictures by using digital!
Yeah, I think the average person has no concept of how much film the pros shoot. In one of Galen Rowell's books, he talks about an assignment he did for National Geographic. He came back with, I think, 70 rolls of Kodachrome exposed. He said the editor was incredulous, because nobody had ever shot so little film for an assignment before.
In workshops for bird or wildlife photography, I think 20 rolls/day is a typical estimate, and a lot of your time is spent finding subjects, or waiting for them to do something interesting, or waiting for the light to be right.
For the Super Bowl, the numbers come out to 40 rolls per photographer. That sounds about right to me. Figure they're getting every bit of every play that they can see from their position, and are shooting 5 frames per second or so.
Re:Tivo isn't ready to die yet
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TiVo Will Die
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Not to say never, but I believe that this announcement is a little premature.
A premature announcement that something is dying? On Slashdot? Surely you jest!
It used to be that companies would "serve" their customers. But at some point, they borrowed a new term from the livestock industry, that sounds almost the same but means something completely different.
I keep hearing scientist A complain about how they want to do X with the Hubble but now they can't because it's being cancelled. And what a pity since that was the most compelling reason for having the Hubble in the first place. And then the other side says that hubble is of limited usefulness, that it's done all it can do and that it wouldn't be worth the dough to keep it working.
Here's the problem. Scientist A says HST is useful, but the guy who says otherwise isn't Scientist B. He's Uninformed Slashdot Moron A. There is no question in the scientific community that HST is useful, and that installing the upgrades (already built and paid for) would be money well spent, especially compared to ISS.
There are many excellent posts here, by real astronomers, explaining why neither ground telescopes nor JWST can do everything HST does (besides JWST not existing yet). That far more scientists want to use HST than there's time for, even without the new instruments, also speaks to the telescope's importance to the scientific community.
Since space is flat, that is, light travels in a straight line, there must be this mysterious force ("Dark Matter") driving the expansion.
No, this is the so-called "dark energy" that's driving the expansion. "Dark matter" acts through the gravitational force, to help keep galaxies and clusters bound. You were on the right track, until you suddenly wrote "dark matter" instead of "dark energy."
Again, these are two completely separate concepts. One makes things fly apart, the other helps keep things together.
What are the observations of "more gravitational attraction" that you refer to?
Since the 1930's, it has been known that stars in galaxies orbit the center of the galaxy more quickly than they should, based on the visible matter. This requires extra "dark matter" to provide enough gravitational force to result in the observed rotational speed.
You are contradicting yourself. It is a case of astronomers being unable to find the matter.
No, I'm not contradicting myself. I was indicating that it's not simply being able to find something "normal," like a lost set of keys. The stuff we can't find is fundamentally different from normal "stuff."
We know too little about "big bang nucleosynthesis" to make any conclusions
Not true. The theoretical predictions of BBN, from particle physics, are in good agreement with observations of deuterium abundance, and the CMB power spectrum. You might not say it's rock-solid, but BBN appears to be generally sound.
To dump money into a project that is at the end of it's lifespan, granted the project was wildly successfull.
Not "was." Is. HST continues to be an incredibly successful scientific tool. With the SM4 upgrades, which are finished, paid for, and sitting uselessly on the ground, it would be an even more useful tool. Your picture of HST as an obsolete, no-longer-relevant observatory is utterly false.
Slashdot Mirror
The electronic detectors (CCDs) on HST, as on virtually all professional telescopes, are inherently monochrome detectors. During an exposure, the detector is behind one of several filters. There are filters that pass UV light, blue light, green light, red light, infrared light, etc. In many cases, the same bit of sky is observed in multiple filters, one after the other. If these happen to be red, green, and blue filters, you can put the three images in the red, green, and blue channels of a color image, and get something that's approximately true color. The filters are not designed to exactly mimic the human eye's color response; that's not an important concern from a scientific standpoint. If some other combination of three filters is used, they can still be placed in the RGB channels of an image, but the result will be a false-color image. That doesn't mean the color information is meaningless; parts of the nebula that look "blue" in the image probably have something physically different happening than parts that look "red."
Many people have an unrealistic expectation that colors in astronomical images should be exactly correct. That's a hard thing to nail down. As I mentioned above, the filters are not designed for human-vision color fidelity, since that's not relevant to the scientific goals at hand. Also, if you look at a nebula with your eye, even through a very large telescope, you vision will be dominated by the color-insensitive rods, and the nebula will appear quite washed-out. So do you want the publicity pictures to mimic this shortcoming of human vision (that we don't see much color in faint things)?
Back to the topic of the CCDs being monochrome detectors: This is true of the CCD or CMOS detectors in consumer digital cameras, too. But instead of putting the whole detector behind a colored filter, each pixel on the detector is behind a tiny red, green, or blue filter. Thus, each detector pixel is still only recording one of the three colors of light. (The new Foveon chips are an exception to this rule.)
But that's not an important effect as far as the distance to the sun goes. The earth's orbit is slightly elliptical, with the sun at one focus of the ellipse. So there's a time of year when the earth is closest to the sun, and a time six months later when it's more distant. The difference in these distances, due to the shape of the orbit, is much larger than the difference in distance that arises from the earth's tilt. The earth is closest to the sun in January, and farthest in July. The difference is about 3 million miles, which is obviously a lot larger than the earth's diameter, and so clearly much larger than the effect of the tilt. Since the whole earth is closest to the sun in January, but the northern and southern hemispheres are in opposite seasons, clearly it is not the distance that's determining the season.
The tilt determines the season by making the sunlight fall more directly (more nearly vertically) and for a longer time each day during the summer.
Reckless drivers, on the other hand...
In workshops for bird or wildlife photography, I think 20 rolls/day is a typical estimate, and a lot of your time is spent finding subjects, or waiting for them to do something interesting, or waiting for the light to be right.
For the Super Bowl, the numbers come out to 40 rolls per photographer. That sounds about right to me. Figure they're getting every bit of every play that they can see from their position, and are shooting 5 frames per second or so.
Chinese Restaurant Without MSG in Food and Real Vegetarian Option? No! Lying about it.
</LionelHutz>
There are many excellent posts here, by real astronomers, explaining why neither ground telescopes nor JWST can do everything HST does (besides JWST not existing yet). That far more scientists want to use HST than there's time for, even without the new instruments, also speaks to the telescope's importance to the scientific community.
Again, these are two completely separate concepts. One makes things fly apart, the other helps keep things together.
Since the 1930's, it has been known that stars in galaxies orbit the center of the galaxy more quickly than they should, based on the visible matter. This requires extra "dark matter" to provide enough gravitational force to result in the observed rotational speed.