Chapter 34, Problem 15RQ

To determine

The type of matter that is visible.

Answer to Problem 15RQ

The matter or object that can reflect or can emit light is visible. The directly visible matter includes planets, stars and many more.

Explanation of Solution

The sensation of sight occurs when an object emits or reflects the light that falls on it. The Sun, stars have their energy and emit light that is visible to humans. Planets, on the other hand, reflect the light that falls on it by the Sun.

The visible universe, including Earth, the Sun, other stars, and galaxies, is made of protons, neutrons, and electrons bundled together into atoms. The discoveries in the 20th century surprised many scientists, the ordinary or baryonic matter makes up less than 5% of the mass of the universe. Except for this percentage, the rest of the universe is made of an invisible, mysterious substance called dark matter.

The human can't see the dark matter and even it is hard to detect with current instruments. But scientists are confident that it exists because of the gravitational effect it appears to have on galaxies and galaxy clusters. The rest matter other than dark matter is visible to humans and is known as visible matter.

Conclusion:

Therefore, the matter or object that can reflect or can emit light is visible. The directly visible matter includes planets, stars and many more.