How is the light seen from the stars, related to Newton's Particle Theory?
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The stars emit particles that reach us.
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Interesting. I vaguely remember a "great attractor" from chaos theory, but what I find when I look it up now is that it refers to a cluster of galaxies, "in the direction of Centaurus and Hydra" where nobody is sure why they're grouped like that.\n\nHere's a direct quote from another source though which I think directly addresses what you're asking about: The galaxy rotational problem refers to the phenomenon of the descrepency between the observed rotational motion of the matter of the galactic disc from the predictions of Newtonian dynamics. (See links below and search for "12.25.I".)\n\nI think in layman's terms what they're boggling about is the "bar" shape that occurs in most galaxies, our own apparently included. A recent issue of Scientific American had a very good theory on how that occurs and why.\n\nIf I'm getting the gist of it right, they're not sure why clusters of stars occur in a semi-pinwheel pattern, since based on observed mass there simply isn't enough to cause such a structure to form or remain stable.  The theory in SciAm had something to do with a coincidence of travelling wave patterns rather than any deep dark mysteries of physics, filiments, or anything else.\n\nSee http://www.sciam.com/, October 2005 issue, p. 43, "Ripples in a Galactic Pond." Very nice article and they explained it more clearly than anything I could put together.
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I would like to to add a few words to a great input other people have already provided.\n\nIn Astronomy, as in all sciences, one can detect an object in one of two ways: either by observing it directly, or observing the effect that it has on other, more easily observed, objects. \nIt's always been known that there was matter in the night sky that we couldn't really directly see. When astronomers use telescopes, or even radio telescopes, they can only see objects which emit light or radio waves. Not all of the matter in the Universe does this - for instance, we wouldn't be able to see planets like our own, because they would be too dim to see. \nAll the mass of of all the planets in our solar system, though, is significantly less than one percent of the Sun's mass. So worrying about matter that didn't shine - non-luminous matter - wasn't of great concern. \nThe first evidence: Clusters of Galaxies The first evidence that there was a significant amount of matter that we couldn't readily see was in investigating clusters of galaxies, which are simply aggregates of a few hundred to a few thousand clusters otherwise isolated in space.\nWhat is Dark matter? This still is an open question.  There are many possibilities, and nobody really knows much about this yet.  Here are a few of the many published suggestions, which are being currently hunted for by experimentalists all over the world.  Remember, you need at least one baryonic candidate and one non-baryonic candidate to make everything work out, so there may be more than one correct choice among the possibilities given here.\nThe baryons are a family of subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons). The term "baryon" is derived from the Greek barys, meaning "heavy," as they are heavier than the other main groups of particles. http://en.wikipedia.org/wiki/Baryon \n•Normal matter which has so far eluded our gaze, such as: \n dark galaxies \n brown dwarfs \n planetary material (rock, dust, etc.) \n•Massive Standard Model neutrinos.  If any of the neutrinos are massive, then this could be the missing mass.  On the other hand, if they are too heavy, as the purported 17 keV neutrino would have been, massive neutrinos create almost as many problems as they solve in this regard. \n•Exotica (See the Particle Zoo FAQ entry for some details. http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/particle_zoo.html) \n\nHere are a wew references \nWhat is the Universe Made Of? http://map.gsfc.nasa.gov/m_uni/uni_101matter.html \nCosmic Hide and Seek http://www.eclipse.net/~cmmiller/DM/ \n\nDark Matter, Cosmology, and Large-Scale Structure of the Universe http://www.astro.queensu.ca/~dursi/dm-tutorial/dm1.html \n\nExperiment\nExperiment with simulation of cluster of galaxies  http://www.astro.queensu.ca/~dursi/dm-tutorial/cluster-sim.html \n\nWhat is dark matter? http://math.ucr.edu/home/baez/physics/Relativity/GR/dark_matter.html
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Relative motion between objects was not new to Newton and his contemporary scientists.\n\nEvery experimental result proved and confirmed again and again Newton’s laws of motion even in the frames of reference moving relative to each other.\n\nLatter with the improvement in measuring technology and particles moving nearly equal to the velocity of light, their behavior contradicted Newton’s laws.\n\nEinstein with a firm belief that any physical law (including Newton's law) must be the same in any reference frame moving relative to each other postulated that speed of light is independent of the source of light.\n\nThis explained every experimental result well and obeyed Newton’s laws.\n\nThe only difference is that  the basic quantities mass , length and time which during Newton’s time was thought of absolute in the sense that  they will not change with the velocity of the frame in which they are , is now considered to vary with the speed of the reference frame, and the velocity of light is independent of the motion of the source.
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Well if you look at the spectrum of a star you'll see a smooth continuum as well as the spectral lines.  Those lines are either absorbtion lines or emission lines of such things as Hydrogen, Helium, Calcium, Iron and a whole heap of others and we know the wavelength of those lines very well so by comparing what we measure them to be with what we have determined in the lab we can calculate how fast the star is moving towards or away us (radial velocity).\n\nThen once we know the radial velocity we just measure where the peak in the continuum is, correct for the radial velocity to find what the wavelength where the emission actually peaks and then since the star is very close to a blackbody we can calculate the temperature (a blackbody of a given temperature will peak at a given wavelength).
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It is Olbers' Paradox.\n\nWhy isn't the night sky as uniformly bright as the surface of the Sun?  If the Universe has infinitely many stars, then it should be.  After all, if you move the Sun twice as far away from us, we will intercept one quarter as many photons, but the Sun will subtend one quarter of the angular area.  So the areal intensity remains constant.  With infinitely many stars, every angular element of the sky should have a star, and the entire heavens should be as bright as the sun.  We should have the impression that we live in the center of a hollow black body whose temperature is about 6000 degrees Celsius.  This is Olbers' paradox.  It can be traced as far back as Kepler in 1610, and was rediscussed by Halley and Cheseaux in the eighteen century; but it was not popularized as a paradox until Olbers took up the issue in the nineteenth century.
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Greetings,\n\nYou will sometimes see pictures of stars with points, reference to the link below.  The gentleman who took the picture placed string in a cross-hair pattern over the objective (the opposite end from the eyepiece) to make the points of the stars.  When he was asked why he does this Mr. Russel stated that he just like the way it looked.\n\nThe points on stars in most photographs are generally derived from either slight overexposure or the telescope being out of collimation slightly.\n\n-matt
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There's a relative way to interpret your question as well.  \nWhen you look at the stars, you're seeing them because of the light that travels from them to you.  It takes time for the light to reach you.  So, you're not seeing the stars as they are "now".  You're seeing them as they were in the past.  They may not even be there any longer.  They may have gone nova or even supernova (if big enough), but the information of that event traveling at the speed of light hasn't reached us yet.  Just  remember it's all relative.  So, depeneding on which oberserver you ask and how you define certain terms...just how many stars that you can see are really there?
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A basic observable quantity for a star is its brightness. Because stars can have a very broad range of brightness, astronomers commonly introduce a logarithmic scale called a magnitude scale to classify the brightness.\nThe Magnitude Scale:\nThe magnitudes m1 and m2 for two stars are related to the corresponding brightnesses b1 and b2 through the equation:\nm1-m2=2.5(logb1-logb2)=2.5log(b1/b2)\nwhere "log" means the (base-10) logarithm of the corresponding number; that is, the power to which 10 must be raised to give the number. Because this relation is logarithmic, a very large range in brightnesses corresponds to a much smaller range of magnitudes; this is a major utility of the magnitude scale.\nThe preceding equation gives us a way to relate the magnitudes and brightnesses of two object, but there are several ways in which we could specify the brightness and this leads to several different magnitudes that astromers define. One important distinction is between whether we are talking about the apparent brightness of an object, or its "true" brightness. The former is a convolution of the true brightness and the effect of distance on the observed brightness, because the intensity of light from a source decreases as the square of the distance (the inverse square law). The apparent magnitude of an object is the "what you see is what you get" magnitude. It is determined using the apparent brightness as observed, with no consideration given to how distance is influencing the observation. Obviously the apparent magnitude is easy to determine because we only need measure the apparent brightness and convert it to a magnitude with no further thought given to the matter. However, the apparent magnitude is not so useful because it mixes up the intrinsic brightness of the star (which is related to its internal energy production) and the effect of distance (which has nothing to do with the intrinsic structure of the star).Clearly, a star that is very bright in our sky could be bright primarily because it is very close to us (the Sun, for example), or because it is rather distant but is intrinsically very bright (Betelgeuse, for example). It is the "true" brightness, with the distance dependence factored out, that is of most interest to us as astronomers. Therefore, it is useful to establish a convention whereby we can compare two stars on the same footing, without variations in brightness due to differing distances complicating the issue. \nAstronomers define the absolute magnitude to be the apparent magnitude that a star would have if it were (in our imagination) placed at a distance of 10 parsecs (which is 32.6 light years) from the Earth. I can do this if I know the true distance to the star because I can then use the inverse square law to determine how its apparent brightness would change if I moved it from its true position to a standard distance of 10 parsecs. There is nothing magic about the standard distance of 10 parsecs. We could as well use any other distance as a standard, but 10 parsecs is the distance astronomers have chosen for this standard. A common convention, and one that we will mostly follow, is to use a lower-case "m" to denote an apparent magnitude and an upper-case "M" to denote an absolute magnitude. \nNotice the very important point that I can determine the apparent magnitude m of a star simply by measuring how bright it appears to be, but to determine the absolute magnitude M the distance to the star must also be known. As we shall see, determining distances to stars is a quite non-trivial matter in the general case.You might think that introducing the apparent and absolute magnitudes would resolve ambiguities about what we mean when we refer to the brightness of a star, but there is a further complication. The brightness of an object (whether apparent or absolute) depends on the wavelength at which we observe it, as we saw clearly in the discussion of
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A star produces it's own light, a planet does not, it merely reflects the light of the star. Because a star producing it's own light, it will glow brightly, dim, then glow again........this is the twinkling effect, much like the flame from a match, or any burning fire. :)
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This should help you:  http://www.le.ac.uk/physics/faulkes/web/stars/o_st_overview.html
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Corpuscular theory- that light is made up of particles.  Although some ancient Greek philosophers postulated that light was made up of particles, this hypothesis is most strongly associated with Isaac Newton.\n\nWave theory- that light is a wave phenomenon.  Again, many people are associated with this idea, but the first to put it on a solid mathematical footing is Christian Huygens.  Maxwell did not discover the wave theory of light so much as explain it.  He linked light with electromagnetism, by showing that electromagnetic theory predicted the existence of waves with the properties exhibited by light waves.\n\nQuantum theory of light- that light is "quantized", that is, it only comes in certain discrete amounts, and that these quanta, called photons, obey certain probabilistic laws.  This theory has it's origins in the work of Planck, who showed that energy in certain situations was quantized, and Einstein, who applied this energy quantization to light to explain the photoelectric effect.
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Analyzing light can tell you almost anything about the universe.  You can calculate just how excited every photon is, what color or what "brand" of light is emitted from any given star in the entire visible universe.  Photons behave certain ways when they interact with certain substances, so how light bounces or reflects or refracts or in other ways interacts with planets and their atmospheres can give us an idea as to what makes it up.  By combining what we can determine from gravitational influence and the amount of energy and type of light emitted from a star, we can find out how massive a star is and what makes it up.  Light is really the only data we have about the universe--luckily, light is qualitative and quantitative and we can learn a heck of a lot from it.  Every single reaction that takes place on an astronomical scale has a tag associated with it--something it gives off 999,999 times out of a million, where if astronomers see it, they know what's going on.  By seeing light--which is more than visible light, but radio waves, UV rays, and gamma rays--they can postulate anything that's going on, even billion of light years away.
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The Big Bang theory offers a resolution of your question (also known as Olbers's Paradox). In a universe with a beginning we can receive light only from that part of the universe close enough so that light has had time to travel from there to here since the Big Bang (about 10 billion years ago). So, even if space extends infinitely far, only a limited region, and a limited number of stars, are visible to us. And the accumulated light from this limited number of stars is not sufficient to spoil the darkness of the night sky.\n\nGod is spelled B-I-G B-A-N-G\nPBrax@netscape.com
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Are you including the stars that are being created, as well as those that do not actually exist anymore but have died out/ supernova'd/ etc. that we are just still seeing since the light has to travel so far?  \n\nI would be interested in how you determined this number ^_^
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Well, we know that the white star must be hotter...for stars, the bluer it is, the hotter.  Similarly, the redder it is, the colder it is.\n\nIn general, white stars have a surface temperature around 10,000 Kelvin, while red stars are around 3000 Kelvin.  For simplicity's sake, let's say the white star is 3 times hotter.\n\nBy The "Stefan-Boltzmann" law, hot things emit more light...a whole lot more, in fact: the amount of light emitted goes as the temperature to the fourth power.  A chunk of white star material that's 3 times hotter than a chunk of red star material will emit 3 raised to the fourth power, or 81 times as much light.\n\nSo, if they're the same brightness and distance, there must be a whole lot more "cool chunks" in the red star to appear just as bright as the "hot chunks" of the white star...it's the same way that two 50-watt light bulbs will be just as bright as a 100-watt light bulb.\n\nTherefore, the red star is much larger.
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Astonomers look at: (1) how fast galaxies are rotating, (2) how galaxies are moving relative to each other in clusters, and (3) how galaxies focus light from object beyond them ("gravitational lensing"). They then calculate how much mass there must be in those galaxies to explain those phenomena. Then they measure how much light is coming out of those galaxies and use that to estimate how much mass is in the galaxies. \n\nThe two techniques give very different numbers for the mass in the galaxies. The light measurement method yields a much smaller answer for the masses. Therefore, there is matter in the galaxies that is emitting little or no light.\n\nWhat dark matter is made of is a matter for speculation. Some of it may be neutrinos, which are abundant subatomic particles that were previous thought to have no mass but were recently determined to have a little mass. They are very, very numerous. Some may be "exotic" matter that we yet know nothing about.\n\nIt may be more mundane, however. We know that in our neighbor of the Milky Way, most of the starlight comes from just a handful of very bright stars, while most of the mass is in a large number of small, very dim stars.