Tired Light

Just for clarification, Lyndon, I am not the one who will be closing this thread; so the insults directed at me are not appropriate.I am just letting you know about a long standing convention in this forum, which was in place before I arrived, and which occurs without my doing anything. The convention seems to be that a moderator asks for closing statements from all parties, and closes up. It won't be me. Look around the forum for any thread with 300 or more posts, and have a look at the last few messages to see how this seems to work.I personally think it is a very sensible principle, but it is not my principle and I'm not the one who will be applying it. It is no more censorship than time limits in spoken debate.You can start new threads, if you like; although new threads should bring up new issues and topics.For example, we could do a thread on the Pioneer anomaly. You claim to be able to explain this; which would be quite a trick given that the anomaly is a blue shift.Cheers -- SylasThis message has been edited by Sylas, 03-23-2005 05:26 PM

This is not really an answer to Lyndon's question. The paper in question is Timescale Stretch Parameterization of Type Ia Supernova B-band, at astro-ph/0104382, by various authors including Permutter. The selection was not simply based on picking Ia supernovae, though that was part of it of course.What Lyndon is referring to is that the paper uses 42 supernova; and yet the Supernova Cosmology Project has identified over 75 high redshift type Ia supernovae. Furthermore, they actually focus on only 35 of those 42.The reasons for the 7 exclusions are explained on page 4 of the paper, and the reason for the selection of 42 is that those are the ones for which a light curve analysis was available. The dataset is taken from that used in an early paper, Measurements Of Ω and Λ From 42 High-Redshift Supernovae, by Perlmutter et al, astro-ph/9812133 (1998). There is a fairly detailed discussion of the dataset in that paper (section 4), though I’d like to see a simpler and more concise statement somewhere. I will ask. They were limited to supernova actually found before reaching peak luminosity so as to obtain a good light curve; supernova which could be reliably assigned to type Ia, and supernova which were not distorted by reddening effects. (Reddening is not redshift; but a result of frequency dependent obscuring by dust clouds.) Last sentence there is not quite right. Hubble had very little to say about causes; he primarily noted the redshift distance relation. For various reasons (a problem with his standard candles) he got a far higher Hubble constant than was correct, and his value was inconsistent with Doppler shifts, as it would have had all galaxies starting out from a common start point only a couple of billion years ago. Hubble preferred the tired light idea, if anything.Rest of the post I basically agree with. Don’t be put off by these comments! All contributions welcome. There is plenty of scope here for new threads. There is nothing wrong with starting new threads to consider specifically focussed topics arising from this thread.Cheers -- SylasThis message has been edited by Sylas, 03-23-2005 09:44 PM

This is false. If it was true, we would not be able to measure any redshifts at all. But of course we can recognize shifted patterns, and use z as a measure of how far they have shifted.

You can do a visual sanity check on the spectrum to see where the various lines are located; but for calculation of redshifts you don't rely on this kind of quick visual check. You do a more careful computed analysis.