How they do that by looking at photos far away??

Saiph · Jul 10, 2005

Both the comet and the spacecraft are going at about the same speed. The spacecraft is pacing the comet, just like two cars on a freeway. Sure, they go fast, but if they're both going ~50 mph, the drivers don't see them moving very much. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

CalliArcale · Jul 11, 2005

Also, the spacecraft is able to compensate for motion -- it can physically rotate to track the comet while it has the shutter open. That cuts down on the blurring. Tempel 1 is being observed by other spacecraft as well. Various space telescopes and Earth-bound telescopes are also watching the comet. The data from all of these sources will be collected and compared to make conclusions about Tempel 1. By the way, what was said earlier about spectroscopy actually goes beyond the visible spectrum. We can only see in a narrow band of the electromagnetic spectrum. (As it turns out, this is the band in which our sun is brightest. So it makes sense for us to have turned out like this.) Longer waves are infrared, just below the visible spectrum, which some animals actually can see, and radio, which no animals can see as far as we know. These frequencies can generate heat, which is how microwave ovens work. Shorter waves are able to do serious damage to your genetic structure: ultraviolet, x-ray, and gamma ray (sometimes gamma rays are considered short x-rays). It turns out that it isn't just the visible spectrum that's interesting when trying to work out the composition of a remote object. These non-visible wavelengths are also interesting. For this reason, Comet Tempel 1 is being observed in a wide range of wavelengths, mainly from infrared through x-ray. Oh, and there's another way to work out an object's composition when you can't go out there and sample it directly. You can work out its mass, volume, and density and make some conclusions from that. But how do you measure the mass of a planet? You can't stick it on a scale. What you do is you work out its gravitational influence. Once you know how much gravitational force it exerts, you know how massive it is. The two are directly proportional. An object like Saturn can be measured crudely by working out how much it affects Jupiter's orbit, whose mass is known by how much it a <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Saiph · Jul 11, 2005

To get a mass you merely need to know the orbital characteristics of a satelite, the mass of the satellite (natural or artificial) is not required. We find the mass of jupiter and saturn by watching their moons. The reason the spacecraft can refine the mass, is not because we know it's mass, but becasue we know it's orbital elements to a much finer degree. The spacecraft can also allow us to determine masses for the moons, since nothing orbits those it's pretty hard to figure that out (but we watch how the spacecraft behaves due to their presence). <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

astralliquid · Jul 12, 2005

Oh my... all of these sound so technical for a person like me..... but I can sort of see the possiblilty of knowing the distance, elements etc .. of a planet by looking of photos and sending spacecraft there now. thanks alot... although I still don't know alot of what you are talking about <img src="/images/icons/smile.gif" /> thanks!!

Saiph · Jul 12, 2005

Here's the key pieces of information you need to know about using light to tell about an object: Atoms are composed of a nucleus and an electron. The electron "orbits" the nucleus (which is much larger), and is held in place not by gravity (like planets around the sun) but by the electrical force. The electron likes to stay in the closest possible orbit (the one with the least amount of energy...they're lazy). however, energy enters the system from time to time. It is either in the form of a collision (something hits the electron, giving it energy), or from a photon (same deal, but the photon is absorbed completely, and the electron is "excited"). When this happens, the electron has to much energy to stay in the lowest state, and so jumps up to a higher one. There's a catch however. An electron can only absorb specific amounts of energy, amounts that directly correspond with other energy levels in the atoms. Anything that does not specifically match, passes through untouched. In this sense, it's like walking up a flight of stairs. You can't take a "half step", cause you don't go anywere (or worse yet fall flat on your face). You can take three steps at once (it's harder, requires more energy)...but you can't take three and a half (or you fall on your face again). Now, a thing about light and energy...different colors of light have different energy. Red is the lowest energy (of the visible light) and blue is the highest. Lower than red (but not visible) goes infrared, microwave, and radio wave (the lowest). Higher than blue is Ultraviolet, x-rays, and gamma-rays (the highest). When you spread light out to see a spectrum, you can detect a rainbow of all these colors (the eye only picks up the standard colors, but instruments can pick up the others). Now, if someone took all the light from the light source, and spread it out into a rainbow, they would see a gap, a black line, at the color where the atom is absor <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

astralliquid · Jul 13, 2005

Its 3.00 am. I couldn't sleep well although very tired. Logon just to check. Was really surprised at the effort you put up just for my understanding. This is really better than my science class 15 years ago. I still need to digest your guide a few more times and go through some old books before I would know what more to ask. Thanks Saiph. This is really the key for me to comprehen. Hope the rest of the "regular" humans like me find those experts guide helpful too. Thanks alot again. Truly appreciate all those who took the time and effort to explain how all this works.

Saiph · Jul 13, 2005

One of the basic things to look up is the model of the atom, and it's "energy levels". Also light and spectra are good too. Google does wonders. Or ask away. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

astralliquid · Jul 13, 2005

Since spent so much time on this, I hope you can spend a few more minutes explain this part which I don't get it. "Now, if someone took all the light from the light source, and spread it out into a rainbow, they would see a gap, a black line, at the color where the atom is absorbing that specific color of light. This is an absorption spectrum, and happens whenever a gas is "backlit" by a light source. As each atom has a specific arrangement of energy levels (determined by the makup of the nucleus and number of orbiting electrons), they also have a specific pattern of black lines to be observed. These act as a fingerprint. Identify the pattern, and you identify the element. " Can you give more detail example? Took what light? spread it out into a rainbow? Where am I standing? Where I am looking at? I need some perspective to be able to visualize.....is the black lines horizontal or vertical? "...blue photon will likely be going in an entirely different direction...so you still see a black line if you look straight tot he light source (most of the blue photons are absorbed, and sent in other directions, only a few are sent to you). " Same to the above example... I don't know how to visualize... Other than that your explaination on the colours, atom, nucleas, energy gave me new meaning to things we took for granted.. I am begining to understand what was so interesting about science class... Btw I am typing in the dark now <img src="/images/icons/smile.gif" /> was in a sleepy mode but your post woke me up.

astralliquid · Jul 13, 2005

You know...googling would only return non layman answers which will ..well sound over technical again... I really like your layman explaination.. I believe alot of the "regular un-scientific" readers will find it useful too..

ldyaidan · Jul 13, 2005

Wow! Great info, folks! Thanks! I learned a lot, and they weren't even my questions! Astralliquid, welcome to SDC! You'll find most of the people here are very intelligent, friendly, and happy to answer questions. I'm just a "normal" person too, and have always had great experiences here. Rae

Saiph · Jul 13, 2005

actually, there are many layman answers out there, and google tends to turn those up first. I'd love to give you a more thurough example (looking at that one...it can be hard to follow without a solid grounding in some of the science...my bad). Right now, I'm off to work (I get to process astronomy photographs...yay!) and I'll whip up something afterwards. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

formulaterp · Jul 14, 2005

"Can you give more detail example? Took what light? spread it out into a rainbow? Where am I standing? Where I am looking at? I need some perspective to be able to visualize.....is the black lines horizontal or vertical? " astralliquid, You may well have done this back in high school chemistry class, but just forgot. Students use a bunsen burner to heat up various elements and look at the flame through a simple spectroscope/spectrometer. They then sketch the resulting spectral lines and compare the differences caused by substituting different elements. This is the very basis of spectroscopy. Please see the following link which describes how to make a simple spectroscope and gives examples of the images you would see. http://www.scitoys.com/scitoys/scitoys/light/cd_spectroscope/spectroscope.html This should at least give you a basic perspective. Spectroscopy is a very refined science within astronomy and I'm sure Saiph can provide more detailed answers to specific questions.

glutomoto · Jul 15, 2005

"You know...googling would only return non layman answers which will ..well sound over technical again..." Maybe some pictures would help, I like to click on the images label to get search results like the following. Google search results for images of "Spectrograph" Google search results for images of "Absorption lines" Google search results for images of "Prism" <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

le3119 · Jul 15, 2005

Q: How the hell do scientists know the ingredient, gases, elements in far away planets just by looking at far away blurry photos? A: Every element absorbs certain frequencies of the spectrum. Super sensitive spectrometers analyze the light from those images and can read the composition of the objects by looking at the absorption lines. Q. How will crashing into a comet tell us what is inside it just by looking at those photos??? A: Same method. The probe and other sensors in orbit analyzed the debris absorption lines. Q. How do they know the other planets are 15 million light years from us just by looking at photos!!??? A. This is complicated. We know the distances to the nearest stars by a method callled Parallex, nothing to do with the photos. We also can estimate the distances to further objects by knowing certain universal constants, analyzing certain kinds of objects we know are a certain distance out....and basically we have decades of experience calculating the distances with more accurate telescopes. Q. How do they know the other planets are rocky like us 15 million light years away just by looking at photos!!??? A. We haven't found planets that far away. We have within about 10,000 Ly, within our galaxy. Again, reading the spectra of what little light reflects off the planets, we conclude that some planets must be rocky like Earth, because they orbit too close to their star - the heat wouldn't allow the planet to be a gas giant like Jupiter, the gas would just boil away. So we figure they must be very hot rocky worlds.

nexium · Aug 3, 2005

I think your intuition is correct, that we can't know that hot jupiter is correct from the photos. We are making educated guesses. Sometimes the evidence comes from several (we think) independent sources, then confidence is high. All theories are subject to major revisions tomarrow, however the probability is low for major changes in some of the therories we use. Neil

nexium · Aug 3, 2005

Excellent explanation except calcium is orange, soduim is yellow. Often both are present giving an in between tint. A prism will separate the colors into a rainbow, allowing an estimate of how much of each element. This field is called spectography. Neil

nexium · Aug 3, 2005

Saiph rarely makes an error, or even a false inference. Most of the rest of us are a bit flaky with some of our answers and comments. Neil

nexium · Aug 3, 2005

I have not actually seen spectograpy, so I may have some of this wrong. Very high magnication is required, so most of the light comes from a single star. I'll guess the rainbow is projected onto a screen a foot wide and 2 inches tall, so both the bright lines and the dark lines are 2 inches long and parallel to each other. Elements and compounds and parts of compounds can be identified. Similar spectroscopes are used for chemical analysis, with very reliable results, by heating the sample hot enough to glow. Neil

How they do that by looking at photos far away??

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