Spiral galaxies

1845 Spiral galaxies

The book of science

Tom Sharp

William Parsons astronomy

Spiral galaxies

Leviathan of Parsonstown


Speculum, an alloy of copper and tin, was the same metal that William Herschel used for the 6.2-inch mirror for the telescope that he made and set up in his garden where he discovered Uranus in 1781.

The mirror for Herschel’s 40-foot telescope was 49.5-inches in diameter, but compared to Herschel’s 6.2-inch mirror, William Parsons’ 72-inch mirror could make visible astronomical features that were over a hundred times fainter. However, this was still not powerful enough to distinguish individual stars, even though Parsons believed the spiral nebulae were composed of stars and not gas.

We will always, it seems, struggle against our limitations to understand the intricacies of our universe, and of our own lives.

See also in The book of science:

Readings on wikipedia: