[LEAPSECS] Coming of age in the solar system
seaman at noao.edu
Sun Sep 5 10:31:26 EDT 2010
On Sep 5, 2010, at 12:11 AM, Poul-Henning Kamp wrote:
> Too bad I don't live in your "real world", in my "real world" paperwork is a very good candidate for the 95% missing mass of the universe.
"Missing mass" was a term introduced following a result from Fritz Zwicky in the 1930's that clusters of galaxies were lacking enough overt mass to bind them together. That galaxies do indeed cluster is an observed fact, however.
The missing mass has since been located. It is now referred to as "dark matter". Two observational results produced this change in viewpoint, terminology, and research directions. First, the mass of the individual galaxies in those clusters is now known to be greater than a simple accounting of the mass of the constituent stars, gas, and dust (the galaxy rotation curves are flat when they would otherwise slope downwards). Vera Rubin gave an excellent overview of this painstaking work at a recent NOAO symposium:
The second observationally established fact was the result of opening an x-ray window onto the universe and discovering that clusters of galaxies contain large stores of hot intergalactic gas. This gas would itself not be bound absent the presence of dark matter. See Nobel laureate Riccardo Giacconi's book "Secrets of the Hoary Deep" for a discussion of this.
What is dark matter? This is a subject of active investigation (along with the even more mysterious "dark energy"). The point to make is that the leading candidates are various classes of weakly interacting particles that are not remote in time and space, but rather are interpenetrating the world around us (and within us).
The real world isn't some rhetorical construct to be tossed around with air quotes.
> The main issue for this particular company, is that there is no economical way to test that a GPS based timing infrastructure handles leap-seconds correctly.
Astronomers may be blinded by science, but doesn't such a current lack describe rather a massive business opportunity? The ultimate source of all economic activity is entrepreneurial adaptation to real world possibilities.
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