Approximately what percentage of the matter in the universe is comprised of atoms?

• A. About 25%
• B. About 50%
• C. About 95%
• D. About 5%

Answer: (D)

Verified step by step guidance

1. Understand that the question is asking about the proportion of the universe's matter that is made up of atoms, which refers to ordinary matter (baryonic matter).
2. Recall that the universe's total matter-energy content includes ordinary matter (atoms), dark matter, and dark energy.
3. Know from cosmological observations that ordinary matter (atoms) makes up only a small fraction of the total matter-energy budget of the universe.
4. Recognize that dark matter and dark energy together constitute the majority of the universe's content, with atoms comprising roughly 5%.
5. Therefore, the approximate percentage of the universe's matter made up of atoms is about 5%, which is much less than 25%, 50%, or 95%.