Comments on: The Walk Up Mount Wilson http://asymptotia.com/2007/08/03/the-walk-up-mount-wilson/ Mon, 13 Oct 2008 07:31:49 +0000 http://wordpress.org/?v=2.5.1 By: nc http://asymptotia.com/2007/08/03/the-walk-up-mount-wilson/#comment-68614 nc Sat, 04 Aug 2007 17:58:56 +0000 http://asymptotia.com/2007/08/03/the-walk-up-mount-wilson/#comment-68614 <blockquote>... My point is this: What was the key foundation upon which Hubble stood to find this astounding Andromeda result? Surely, everybody else had access to the information about the various galaxies (or “nebulae” as they mistakenly called them then) out there? Why did they miss something that seems so obvious to us today? Ah, here comes one of those great pieces of “bread and butter” physics. ...</blockquote> Yes the Cepheid variables were the crucial distance yardstick for Hubble. Of course there is a deeper problem here, in that Hubble assumed that there was one type of Cepheid variable, when there are two, so he underestimated the distance of the yardstick by an order of magnitude. Hubble's results indicated a Hubble parameter of 540 km/s/megaparsec, and this suggested an age for the universe of 2,000 million years, far less than the age of the Earth. The error, that there are two types of Cepheid variable, was only discovered in 1952, 23 years after Hubble's discovery. <em>[.... snip.... -cvj]</em>

… My point is this: What was the key foundation upon which Hubble stood to find this astounding Andromeda result? Surely, everybody else had access to the information about the various galaxies (or “nebulae” as they mistakenly called them then) out there? Why did they miss something that seems so obvious to us today?

Ah, here comes one of those great pieces of “bread and butter” physics. …

Yes the Cepheid variables were the crucial distance yardstick for Hubble. Of course there is a deeper problem here, in that Hubble assumed that there was one type of Cepheid variable, when there are two, so he underestimated the distance of the yardstick by an order of magnitude. Hubble’s results indicated a Hubble parameter of 540 km/s/megaparsec, and this suggested an age for the universe of 2,000 million years, far less than the age of the Earth. The error, that there are two types of Cepheid variable, was only discovered in 1952, 23 years after Hubble’s discovery.

[.... snip.... -cvj]

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