There are a number of interesting ways of measuring the Universe.

For the Solar System there is the use of lasers.

For within our Milky Way (The Galaxy), there are: trigonometric parallax, binary and multiple stars, the motion of nearby stars, etc.

For extragalactic measurements, there are: Cepheid variable stars, type Ia supernovae (particularly useful for accuracy at great distances) and type II supernovae, novae, RR Lyrae variables, etc.

For secondary indicators, there are HII regions and globular clusters, etc.

For great cosmological distances, there is Redshift (using look-back time - FROM the REDSHIFT), always used in combination with other distance measurements.

A greater combination of these methods is used for increased accuracy.

To me, it has always been fascinating that so many methods have been found for measuring the Universe.

I have found that the text, *The Cosmological Distance Ladder* (1985) perhaps out of print, is excellent for explaining these methods in great detail. It is written by one of my favorites, Michael Rowan-Robinson. Hopefully, there may be a newer edition with additional and more recent methods.

ljbrs [img]/phpBB/images/smiles/icon_smile.gif[/img]

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*Nothing is more damaging to a new truth than an old error.* Goethe

<font size=-1>[ This Message was edited by: ljbrs on 2001-12-23 19:05 ]</font>