What Objects Did Harlow Shapley Use as "Signposts" to Figure

question 27

Multiple Choice

What objects did Harlow Shapley use as "signposts" to figure out the extent of the Milky Way Galaxy and the location of its center?

• A) thick clouds of cold hydrogen giving off 21-cm radiation
• B) globular clusters
• C) HII regions
• D) dust clouds
• E) big arches advertising "billions and billions sold"

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Definitions:

Pigouvian Tax

A tax imposed on any market activity that generates negative externalities, intended to correct the market outcome.

Sulfur Dioxide

A colorless gas with a sharp smell, produced by burning fossil fuels and volcanic eruptions, often associated with air pollution and acid rain.

Marginal Social Cost

The total cost to society of producing one additional unit of a good or service, including both the private costs and any external costs.

Pigouvian Taxes

Taxes designed to reduce external costs.