Astronomy
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News of the Universe Frequently Asked Questions Enter the tutorial or the Italian version or the French version Cosmological fads and fallacies CMB Spectrum CMB Anisotropy Big Bang Nucleosynthesis Supernova Observations Cosmology, Religion & Kansas Send me your comments New on the tutorial: A discussion of the history of the CMB dipole discovery. A history of COBE , the COsmic Background Explorer, in pictures.
Ned Wright's Cosmology Tutorial
Astronomy is the scientific study of the universe as a whole, and of celestial bodies and the underlying physics governing these bodies. It is in some sense one of the oldest of the natural sciences, having been practiced by even very ancient civilizations, but it is also among the most modernized of the sciences, having extensively exploited both advances in technology and the rise of space exploration. The progress of technology has dramatically improved our understanding of the universe, revealing a richer tapestry than had ever been imagined before.
General Astronomy
Galaxies
At the turn of the 20th Century, a debate was raging in astronomy about faint, fuzzy objects called "nebulae." Some astronomers thought nebulae were small clusters of stars in our own galaxy. Others saw some of them as giant, distant collections of stars, some larger than the Milky Way itself. Finally, in 1924, American astronomer Edwin Hubble measured the distance to what was then called the Andromeda Nebula.