Talk:Cosmic distance ladder

Proposed merger with Extragalactic Distance Scale (May 2008)

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section.

There's strong overlap between the two subjects, but a lot of hammering out is needed to get that done. This ("CDL") page is stronger for the near-distance things. The other article ("EDS") is more like a laundry list at this point, and is more aimed at the extragalactic distances in particular. Ideally I think the two could be merged to a rather large article ... but to do it properly would make an article so large as to be a candidate for splitting. I think both articles can be fleshed out a bit more prior to a reconsideration of the merger. At this time I vote against the proposed merger with a "not at this time, but later" qualifier: both articles should be edited so as to make such a merger seamless in the future. BSVulturis (talk) 15:49, 15 May 2008 (UTC)

I agree, lots of overlap and would throw in standard candle to the mix too. WilliamKF (talk) 22:08, 23 May 2008 (UTC)

Agree, as per WilliamKF. --Cyclopia (talk) 00:06, 18 October 2008 (UTC)

• I completed the merge of Extragalactic Distance Scale and Standard candle into this article. A little more cleanup may be required and several topics need expansion.—RJH (talk) 19:12, 20 October 2008 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

"clarification"

I added a section called "clarification" because I think the article was a bit obscure for people with no idea of the concept at all. It still needs work and I wrote it largely from the top of my head, plus I'm no astronomer so it needs to be reviewed by a pro!

212.153.56.254 13:20, 6 January 2006 (UTC)

Baseline for parallax measurements

I think the baseline is normally 2 AU rather than 1 AU. The baseline is the diameter of the Earth's orbit (not the radius), doubling the baseline and doubling the angle that must be measured and thus doubling precision. But I'm not confident enough to change the text.

I do believe there's a need for this article. Good effort. --Chris Jefferies (talk) 01:14, 5 January 2008 (UTC)

The baseline across the i like pizza isoceles triangle is 2 AU. The formal development for parallax involves splitting that isoceles triangle into two right triangles, each with the short leg of the triangle between Sun and Earth (so that is 1 AU) and the long leg of the triangle being the distance between the Sun and the target star. So for measuring, yes, the baseline could be as large as 2 AU, but the parallax is defined with a right triangle whose short leg is 1 AU. BSVulturis (talk) 23:59, 12 February 2008 (UTC)

Measuring distances

My check list for inclusion:

• Trigonometric parallax
• Variables: Eclipsing binary, Cepheid variable, RR Lyrae variables, Novae
• Planetary nebula luminosity function
• Globular Clusters (via main sequence curve)
• Tip of the red giant branch
• VLBI: Radio jet proper motion
• VLBI: Maser proper motion
• Sunyaev-Zel'dovich effect
• Surface brightness fluctuation
• Tully-Fisher relation
• D-sigma relation (ellipticals)
• X-ray burster
• Brightest cluster galaxy
• Type Ia supernovae
• Gravitationally lensed quasars
• Gamma ray bursters
• Coalescing massive black holes

—RJH (talk) 16:50, 18 October 2008 (UTC)

Laymens Terms

This is a fine academic article, but heaven forbid if someone unfamiliar with astronomy wants to understand how distances are measured. Could someone please make this article a little more friendly, or perhaps introduce an article for laymen like "list of methods for measuring astronomical distances" or something similar. Thanks. 76.212.144.130 (talk) 10:10, 18 October 2009 (UTC) Sandy

I looked at the introduction, as it existed in Oct 2009, and the first part of the "Direct methods of distance determination" section. These parts (in the old version as well as the current one) seem pretty accessible to me. Which parts do you find confusing? Why are they difficult to understand? Danielx (talk) 02:18, 11 June 2010 (UTC)

Table as replacement for image

Method	Uncertainty for Single Galaxy (mag)	Distance to Virgo Cluster (Mpc)	Range (Mpc)
Cepheids	0.16	15 - 25	29
Novae	0.4	21.1 ± 3.9	20
Planetary Nebula Luminosity Function	0.3	15.4 ± 1.1	50
Globular Cluster Luminosity Function	0.4	18.8 ± 3.8	50
Surface Brightness Fluctuations	0.3	15.9 ± 0.9	50
D - σ relation	0.5	16.8 ± 2.4	> 100
Type Ia Supernovae	0.10	19.4 ± 5.0	> 1000

[Note: table created by —Preceding unsigned comment added by 86.88.102.93 (talk) 20:21, 5 January 2010 (UTC) ]

I'll replace the image (Image:Distanceindicator.jpg) with this table, now. Revert me if there was a reason someone hadn't done this already. -- Quiddity (talk) 19:45, 12 June 2010 (UTC)

Magnitude vs redshift plot

I think a plot of this should be included. Could anybody tell me why is there a difference between the Magnitude vs redshift plots of the following links?

-Bottom of (the plot before the last one) http://www.rqgravity.net/Supernova -Page 7 of http://arxiv.org/abs/astro-ph/9812473.

Thanks! --190.188.3.11 (talk) 04:17, 12 June 2010 (UTC)

Diagram of the distance ladder

The diagram given is very similar to the diagram given on page 80 of the article "The Planetary Nebula Luminosity Function", by Robin Ciardullo in L. Stanghellini et al. (eds.) "ESO Astrophysics Symposia, pages 79-90" DOI 10.1007/11604792_10, Springer-Verlag, 2006. There are some differences (the use of colors is novel, and the ordering is somewhat different). But I am concerned that this may be bordering on copyright violation. A more elaborated diagram of the same sort is on page 284 of Richard de Grijs, "An Introduction to Distance Measurement in Astronomy" (which is where I found the reference to Ciardullo). I think that I am obligated to remove this diagram.

My Perspective

Maybe this would be considered original research, but it seems to me that the title concept here is more broadly applicable than to just astronomy. The concept of using what you know to learn something you otherwise could not have known without it is applicable to virtually all of science. That's what enables more and more advancement with each successive discovery. Perhaps the introduction could say something to this effect? 76.103.93.154 (talk) 21:24, 26 October 2015 (UTC)

None of this makes any sense

Look at the amount of assumptions that are made to calculate parallax. This is dumb. And everyone who read this article is probably less intelligent after reading it. First assuming the distance of the first cluster, then basing all new calculations of the sweeping assumptions of the first. When the difference is so unbelievable negligible that pretty much everyone has to trust hubble, the flying trash can in the sky. Plus, the entry itself admits to problems with their own assumptions. Do minor defects in a lens count? How can a defect not compound after hundred billion quintillion billion miles? Doesn't light bend too? What about obstructions? How do we even know the first measurement of the closest cluster of stars is correct?

None of this makes any sense and anyone who thinks it does is lying to themselves.