> The ABC's of Distances > It is almost impossible to tell the distances of objects we see in the > sky. Almost, but not quite, and astronomers have developed a large > variety of techniques. Here I will describe 26 of them. I will ignore > the work that went into determining the astronomical unit: the scale > factor for the Solar System, and just consider distances outside of > the Solar System.
Yes, thanks, Wright's website is a valuable information for distance, and I have visited it before.
I did not see a category of where you measure the size of an object related to the magnification of the telescope, and given several assumptions and thus tell us the distance. Example: if you see a elephant in Africa the size of a bee, then you know the elephant is approx X number of kilometers away.
Likewise, if we can see a quasar as a faint red spot on the telescope, means the quasar cannot be billions of light years away but rather millions of light years at most.
Enrico, do you know of a website that discusses the maximum resolution of the Hubble Space Telescope in seeing a distant object such as a average galaxy or a supernova? It is funny how physicists trained in optics can tell you the limit of resolution of a light-microscope, but that noone in optics is seeming to talk about the upper limit of resolution of a astro body at a distance.
Is it that everyone in astronomer believes there is no upper limit to seeing distant objects? Do they think that infinity is the upper limit? Have they ever heard of loss of light intensity over distance and that every light source will be diffused if traveled far enough.
What is the upper limit of Hubble Space telescope? Is it 400 million light years? Perhaps far less than 400 million light years.
Does Wright have another website where he discusses the diminuation of light as it travels large distances? Space is almost a vaccuum but it also has some diminuation or scattering properties. And Space has alot of things "in the way" so that light from say the quasars have a good chance of encountering objects in the way.
It is easy to find where biology observing in light-microsopes comes to the end of feasibility of seeing. We cannot see viruses in light-microscopes because of resolution and the optics of light just are not capable of going that small.
But the astronomers seem to have shyed or shied away from thinking, computing and informing about where the telescopes cease to see astro bodies at a far distance.
Now the best flashlights of a double AA batteries cannot be seen at a distance of 10km in pure darkness. The dirt and other things in the air diminish the light, but also the luminosity or power intensity drops off as the inverse square of distance.
So that biologists over the past 200 years have been rather good at informing people as to what a microscope of light with lens can actually see on the slides and where the limit of viewing is of tiny objects.
But the astronomers over the past 100 years have been rather derelict in such duties as knowing and figuring out the limits of any and all and the best telescopes. Instead, the astronomers seem to run on a notion that there is no upper limit to viewing astro bodies and that a star or galaxy or quasar can exist at infinity and they would see it in their Hubble Space telescope.
So, Enrico, what is a good website that talks in depth about the upper limit of Hubble Space Telescope? The physics of Optics probably would say the upper limit of Hubble Space Telescope is about 400 million light years for a supernova and beyond 400 million light years, you just cannot see the supernova.
Edward L. Wright's website is a good website, even though it is missing a chief ingredient of distance measure, which I will get to shortly. And this feature is missing in the whole of astronomy. Why it is missing I have no idea, other than to say that astronomers and physicists have been very sloppy for the past 100 years of telescopes. One would have thought that the physicists and astronomers could have taken clues from the biologists with microscopes and have realized that various threshold distances are to be obtained from the mere existence of the instruments used to measure length in biology as well as distance in astronomy. Biologists know very well that they cannot measure the length of a virus in a light-microscope, but try telling the astronomers that their seeing of quasars and their speculation that they are 4 billion light years away, try telling them that such is an impossibility due to just their instruments involved.
So what Wright's distance measures is missing is perhaps the most reliable and trustworthy of all the distance measures, --- the actual telescope itself.
The Doppler shift gives the redshift of a distant object which is our best indicator of its distance, but we need to know the Hubble constant, Ho. --- end quoting ---
So let me ask a few questions of Wright. Is the Hubble Space Telescope our very best telescope to the visible light region? If yes is the answer then the next question is whether this telescope can pick up a person standing on Pluto with a double AA battery flashlight that is pointed at the Hubble telescope? If the answer is yes, then put the flashlight on the nearest exoplanet and ask the same question. Ask the same question until I find at what distance is the Hubble telescope unable to see the flashlight? Mind you, the Hubble is the best of the telescopes and it has a distance upper limit. An upper limit for a flashlight as well as an upper limit for a Supernova. At some distance from Earth, the Hubble telescope cannot see a Supernova. I reckon that distance is 400 million light years.
What that means, since the astronomy and physics communities believes that Quasars are some fancy energy object and that they are billions of light years away, yet the Hubble telescope and other telescopes can resolve their image as "faint red spots".
So, yes, the quasars appear as objects in the telescopes, meaning that the objects are no more than 400 million light years away.
You see, the biologist knows that he cannot see a virus in a light microscope because of the physics involved with light and optics of a light microscope. But the astronomer was too daft to realize that the instruments of telescopes were the finest measuring of distance tools here on Earth. And that the Hubble, in the fact that it can "see quasar objects" means that they are of millions of light years or less, but never billions of light years.
I do not know why the astronomers and physicists were so derelict of their jobs of learning, telling why a telescope is a distance instrument and why the physicists never bothered to find out the upper limit of distance by the individual specific telescopes used.
So Mr. Wright should have started off with A in his ABC's of distance by having the TELESCOPE instrument as a distance measure in itself. And that the last category of redshift is mostly a fantasy category of huge errors.
Approximately 90 percent of AP's posts are missing in the Google newsgroups author search starting May 2012. They call it indexing; I call it censor discrimination. Whatever the case, what is needed now is for science newsgroups like sci.physics, sci.chem, sci.bio, sci.geo.geology, sci.med, sci.paleontology, sci.astro, sci.physics.electromag to?be hosted by a University the same as what Drexel?University hosts sci.math as the Math Forum. Science needs to be in education?not in the hands of corporations chasing after the next dollar bill.?Besides, Drexel's Math Forum can demand no fake names, and only 5 posts per day, of all posters which reduces or eliminates most spam and hate-spew, search-engine-bombing, and front- page-hogging. Drexel has?done a excellent, simple and fair author- archiving of AP sci.math posts since May 2012?as seen?here: