Martin

If anybody here at SFN ever wants to convert between ordinary sky coords and galactic coordinates there is an online calculator that I've sometimes used---if it is still up and running: Professor Murphy's online calculator. (Johns Hopkins) http://fuse.pha.jhu.edu/support/tools/eqtogal.html for example, the hotspot in Leo could be expressed in coordinates in two different ways ordinary:(11 h 12 m, -7.22 degrees) galactic: (264 degrees, +48 degrees) the speed that the sun and planets are heading in that direction is 1.23 thousandths of c You can get that in meters per second if you want to by multiplying 0.00123 by 299792458 meters per second. I think it comes to around 370 kilometers a second so it is more than ten times faster than the earth goes around the sun but the main thing is to know it as a fraction of the speed of light because that tells you right off the rough size of the doppler effect on the microwaves, which is the measurable thing.

this sticky seems to be growing! more people are adding astronomy links! thanks to admiral, nightsky, and nalos I just thought of a good link which is a starmap with the Microwave Background dipole temperature variation superimposed http://aether.lbl.gov/www/projects/u2/ it shows there is a doppler hotspot in the direction of Leo because we are heading in that direction at some speed like 1.23 thousandths of the speed of light---in absolute space terms I think it is a really cool map and rather old----the result was reconfirmed by satellite observatory in the 1990s--- but the original result, gotten by U2 plane flying around measuring the microwave temp in various directions, turned out quite accurate. -----------------------------

That U2 microwave sky map is so nice I went and dug up the link "...a star map with the temperature of the Background as an overlay, showing the hotspot. So you can see the stars around Leo and a kindof contour map of temp: http://aether.lbl.gov/www/projects/u2/ ...." in case someone wants more precision here is the 1996 report http://arxiv.org/astro-ph/9601151 "The Dipole Observed in the COBE DMR Four-Year Data" ----------------------------- IIRC the Background is just about 3.4 millikelvin hotter in the Leo direction when Leo is visible in the sky you can point your finger in the direction the sun and earth are traveling, in absolute terms, in space this is a combination of our motion within the MilkyWay framework and the overall motion of the MilkyWay itself, relative to background

see also another recent newscientist article with more or less the opposite conclusion http://www.newscientist.com/news/news.jsp?id=ns99996057 BTW these articles report studies of possible change in alpha which does not directly imply a change in the speed of light when journalists get hold of reports about change in alpha they tend to bend them into something about change in c because readers know what the speed of light is and dont know what alpha is since c is one of the constants entering into a formula for alpha you can always find someone interested in speculating that IF a change in alpha can be proven then it MIGHT have resulted from a change in c but it could just as well have happened that alpha changed without any change in the speed of light at all-----alpha is a number approximately equal to 1/137 which indicates the strength of electromagnetic interactions---it is like Coulomb's constant expressed in planck units the strength of electric attraction/repulsion could conceivably change slightly over time (compared, say, with gravitational interaction) without the speed of light changing Anyway, the issue of alpha changing is pretty open, you just have to read both sides and see who you think is doing the solidest research. new scientist is presenting one side and then the other just a few weeks apart---they really shouldnt drag the speed of light into it, but I guess they do that in order to tap a wider audience so its understandable

I know someone who is pretty good with latin If you want, give me a brief sample of what you want translated (no promises! but something might work out) BTW how are you at translating Latin into English?

for M equal to the mass of the sun, that formula namely 2GM/c2 gives you about 3 kilometers then if you want to calculate other BH sizes its is really simple If someone tells you that in center of some galaxy like Milky Way there is a 10 million solar mass black hole you can reckon its radius is 30 million kilometers. this works for the simplest situation where you dont assume anything fancy about the BH like that it is electrically charged or rotatating fast enough to effect the shape of its event horizon. as long as there are no extra things to worry about you just multiply the solar masses by 3 so a 10 solar mass hole has radius of 30 kilometers. planet jupiter is very roughly 1/1000 of mass of sun so a black hole with jupiter mass would have radius roughly 3 meters so you could keep it in your swimming pool or just leave it out in the back yard

JaKiri, why can they not fix the "most users ever" gizmo? I think people like to have an activity gauge and see it rise (I certainly do) and also everytime I come to the main page and see that broken gizmo, it has a bad impression because it actually gives wrong information. it says, like the most users ever was 44, about 3 minutes ago, but that is wrong, it is more like 75 about 10 days ago so the first thing i see when I get here is some (admittedly trivial) misinformation is there a technical reason that somehow makes it hard to fix?

gotcha! I like this distinction----using analogies and metaphors to shortcut the math---emphasizing accessible issues. that is talking about glad you clarified wasnt wishwash, I simply didnt get the distinction at first

I'm drifting that way too it gets confusing with all these different sources (better than having none at all tho) tonight I ran into a wonderful quote from robert frost It may have been in an article you gave a link to "We dance round in a ring, and suppose, but the Secret sits in the middle and knows."

Jim, if not too much trouble could you post a link here (in this sticky thread) to a star map or a set of star maps. the idea being if someone shows up at SFN asking something like where's Arcturus? where and when can I see the constellation Pegasus? (not those particular questions but ones like them) then we have the link to give them, for star maps

Ive done enough talking on this thread for a while and there are probably half a dozen people around who can explain the SR speed limit---or know another SFN thread where it is derived if something has positive rest mass it cant go c it has to go some speed less than c I dont know how anything could be turned into pure energy by being accelerated----I suspect it couldnt but dont know if something has zero mass, thinking of a photon, I dont see how it can go any speed but c although in various media light waves can have different speeds, and phase velocity and group velocity can be different I still cant picture anything which people would call a photon travelling faster than c. so I am going to pass, on what MadHatter is talking about here and hope someone else responds the Special Rel speed limit is totally real for me and I believe in it with absolute conviction----it just does not apply over vast distances of curved space, to the case of recession speeds (the rate those distances increase)---so it confuses me to be told about something going 300c in an earthbased experiment. Somethings wrong, or something i didnt get.

thanks to admiral and to jim for adding good links to this sticky hope more do jim's link is a good way to get the latest news, I noticed 3 items from today 29 June including a nasa picture of NGC 7331 some 50 million LY away in Pegasus a galaxy some call a "twin" of the milkyway "... Since we're inside our galaxy, many of its interesting features are shrouded by dust, so looking at NGC 7331 is like looking into a mirror 50 million light-years away...." congratulations on having that site. do you update the main page fairly regularly so it really is fresh news, as I experienced just now, that would be great!

actually I just checked at Ned Wright's site he has something on latest research he calls "News of the Universe" http://www.astro.ucla.edu/~wright/cosmolog.htm#News which I see he has updated as recently as 22 June but he is still going with the estimate of 13.7 billion years that actually came out last year I dont think there'v been any more recent measurements that challenge this, but if anyone finds any please report them! anything more reliable and accurate than the WMAP (wilkinson microwave anisotropy probe) would be a welcome surprise

just to check the popular article quoted here, I used Siobahn's calculator and it said indeed the signal we are getting from the black hole is 12.7 billion years old and that the black hole was 1.06 billion years from the beginning http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html I just put z = 5.47 into the calculator (also H = 71, and Omega = 0.27, and Lambda = 0.73, which are the latest parameters i've seen) Sayonara I have not seen any new estimates which would lead to an age of the universe like you say. Everybody is using the WMAP data, that I know of, that came out this year and it leads to age-estimate of 13.7 billion years. If you see that other estimate on the web somewhere, please give us a link! It would be very surprising and I would like to see it.

the popularization article refers to this technical article by Romani and others: http://arxiv.org/abs/astro-ph/0406252 this is what was just published in Astrophysical J. Letters it says the redshift is z = 5.47 this is not the highest redshift for a galaxy a team in france has observed a galaxy with redshift z = 10 that would be even farther and older and just as massive BUT it is not a black hole

it is indeed, if it is as old as they say: 12.7 billion years (only had a billion years to accumulate) for some masses to compare with I happened to find this----dates from 2002 and last modified 2004, so it isnt obsolete information http://curious.astro.cornell.edu/milkyway.php says estimated mass of milkyway is a trillion solar masses and the mass of the visible stars is roughly a tenth of that that is the mass in stars is roughly 100 billion solar masses (but I have also heard 200) the rest of the mass of the MW would be gas, dust, dark matter we also have a black hole at center of MW but it is only some 10 million solar masses IIRC. It has been observed swallowing stuff and stars swinging fast around it. But unless stuff just happens to be falling in you cant see it. Anyway it is small: a few million solar masses. so the puzzle here is they have found a youngish hole with a mass of 10 billion. it is not a real difficult paradox but it does make you wonder how such a size hole could accumulate so fast.

JaKiri thanks for responding! Tycho, there are two theories of Relativity the 1905 "special" theory does not allow FTL speeds einstein's later theory, the 1915 "general" theory of rel allows FTL recession speeds the later theory also allows a preferred frame of reference and a universal idea of simultaneity, and as developed in the Friedmann equations model actually predicts this (the standard cosmology metric has a preferred frame which is the CMB frame, stationary w/rt "hubble flow" or w/rt the expansion of the U, which is essentially same as being stationary with respect to microwave background) and cosmologists constantly make use of the CMB frame and the notion of a universal absolute time (simultaneity and time are not "relative" in the sense of the 1905 theory) when people talk about "Relativity" it is important for them to make it clearly explicit what theory they mean because the two theories say different things (although because one is local and the other global they do not actually contradict each other) if people just say "Relativity" then confusion can arise recession speed is different from local speeds of encounter the point is that over vast distances there can be a significant amount of curvature between you and it and special rel does not apply to curved frameworks, it only applies to local flat frameworks

I agree with cap'n the new posts per day is a fun statistic to have I hope Sayonara will update it for us for the time being I will add it to my signature most new posts in one day 425 on 28 June or something like that