Discuss the discovery of galaxies, and the scientific debate that led astronomers to identify them as distant clouds of billions of stars
What will be an ideal response?
In the middle 1800s, astronomers were first able to build telescopes large enough to see galaxies clearly. Due to their nebulous appearance and spiral shape, they were called "spiral nebulae".There was disagreement over whether galaxies were within our own galaxy, or distant objects outside of our galaxy. Astronomical technology was not sensitive enough to resolve the issue until the early 1900's. In 1920, Edwin Hubble was able to use a telescope much larger than its predecessors and more sensitive photographic techniques to take more detailed pictures of galaxies.Hubble's images showed individual stars in nearby galaxies. More importantly, Cepheid variables could be seen, and their period measured. The measurement of the period of the Cepheids allowed astronomers to calculate their distance, which was clearly outside of the Milky Way.
You might also like to view...
Potential Energy: A 7.0-?C point charge and a 9.0-?C point charge are initially extremely far apart. How much work does it take to bring the 7.0-?C point charge to the point x = 3.0 mm, y = 0.0 mm, and the 9.0-?C point charge to the point x = -3.0 mm, y = 0.0 mm? (k = 1/4??0 = 9.0 × 109 N ? m2/C2)
A. 95 J B. 190 J C. 63 J D. 16 J
Answer the following statement(s) true (T) or false (F)
1. A quanton moving in a system whose V (x) is given by the box potential energy function can never be unbound, no matter what its total energy might be. 2. An electron moving near a proton can never be unbound, no matter what its energy might be.
A series LC circuit contains a 100-mH inductor, a 36.0-mF capacitor and a 12-V battery. The angular frequency of the electromagnetic oscillations in the circuit is
A. 36.0 × 10?4 rad/s. B. 6.00 × 10?2 rad/s. C. 2.78 rad/s. D. 16.7 rad/s. E. 277 rad/s.
The tilt of Earth's axis greatly affects the
A) change of Earth's seasons. B) hours of daylight. C) intensity of sunlight that reaches Earth's surface. D) distribution of heat energy, hours of daylight, and the change in seasons.