# Tag Info

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$G$ was historically calculated from the Cavendish experiment, involving balls and a torsion balance. The earth's mass was actually calculated before the sun's mass. Using the assumption that the earth was a sphere, its circumference and thus its radius could be determined through geodesy, as was done historically even before Newton. The acceleration of an ...

3

The positions of stars on the sky are defined against a co-ordinate reference frame that is ultimately defined by the positions of very distant radio sources (quasars at high redshift) that are assumed to be "stationary" in terms of their celestial grid co-ordinates (see International Celestial Reference Frame) All stars can have their positions precisely ...

3

Spectroscopic parallax is the technique whereby you estimate the absolute magnitude (i.e. the brightness it would have if it were placed at 10 pc) by estimating what "type" of star it is using information fro a spectrum. It can be applied to any kind of star where (a) you have a reasonable chance of determining the type of star from its spectrum and (b) ...

3

Olbers’ Paradox says that in an infinite universe every line of sight will end on a star. That statement is incomplete. The paradox requires not only an infinite universe, but also one that is both static and infinitely old. Neither of the second two statements are true for our universe. Your question considers the effect of aging. As our position ...

3

I don't think there is an exact definition. The term is used as a means of referring to an array of observation times of some astronomical phenomenon. In common usage, the terms "long cadence", or less often "low cadence", means that there is generally a longer time interval between observations. On the other hand, a "short cadence" or "high cadence" means ...

2

$\theta$ is half the difference in direction of 2 measurements of the position of the star taken 6 months apart.

1

In the search by parameters screen you'll notice you can set limits on the morphological type. The types are given names, but the limits are input as though they are ordered. A little experimenting confirms the numbers you see reported as "type" correspond to the limits options, in the order of the drop-down menu. That is, we have: -3: dS0 5: Sb ...

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