In 1917,Harlow Shapley Plotted the Positions of Almost a Hundred

question 132

Multiple Choice

In 1917,Harlow Shapley plotted the positions of almost a hundred globular clusters.But the galactic plane is cloaked by gas and dust,and the best way to "see" through this is with long-wavelength radio waves.However,in 1917 radio astronomy did not exist.How did Shapley accomplish his task?

• A) He could only see globular clusters that were relatively close to the Sun.
• B) He concentrated on using the long-wavelength end of the visible spectrum: red. This worked well because globular clusters are old and are dominated by red stars.
• C) The globular clusters are mostly in a halo up off the galactic plane, so the dust was not a great problem.
• D) In order to form a globular cluster, a great deal of interstellar dust is used up. Thus, globular clusters create holes in the dust and are relatively easy to see.

---

Definitions:

Market System

A system where economic decisions and the pricing of goods and services are guided purely by the interactions of a country's individual citizens and businesses.

Centrally Planned System

An economic system in which decisions about production and distribution are made by a centralized authority rather than by market forces.

Free-Market System

An economic system based on supply and demand with minimal governmental control, where prices are determined by the interactions between consumers and businesses.

Marxist Economy

An economic system based on the socio-economic theories of Karl Marx, focusing on the role of labor in the development of an economy and the concept of class struggle.