Why Is It Surprising to Find Spiral Arms in Spiral

question 81

Multiple Choice

Why is it surprising to find spiral arms in spiral galaxies?

• A) Spiral arms require new stars, and previous new stars should have already used up the interstellar medium; no new stars should be forming now.
• B) The variations in speed of the stars across galaxies are not high enough to twist the shape of the arms into a spiral.
• C) There is no known mechanism to generate spiral arms.
• D) The motions of the stars and differential rotation of the galaxy should have wound their arms tightly and made them blend and disappear.

---

Definitions:

Social Evolution

The process by which societies and cultural practices develop and change over time.

Human Survival

Refers to the ability of humans to continue living and thriving, often despite adverse conditions or challenges.

Social Cost

Refers to the total impact of an activity on society, including negative effects that are not usually accounted for in the marketplace.

Environmental Damage

Harm caused to natural environments due to human activities, often impacting ecosystems, biodiversity, and public health.