Chapter 4 Questions


Question:

What role do light and gravity play in the universe?

Answer:

Light is a consequence of the electromagnetic force. This force and gravity are the two long-range forces that control the large scales in the universe. Gravity shapes the universe and is probably connected to the existence of space and time themselves. Light, or more generally electromagnetic radiation, fills the universe and was once a dominant factor in the evolution of the cosmos.

Question:

Do strong and weak forces have repulsive forces like electromagnetism or are they only attractive like gravity?

Answer:

The strong and weak forces are a bit different from the other two. It is better to think of them as the regulators of particle interactions, the strong force for particles composed of quarks (e.g. nucleons), and the weak force for the leptons (e.g., electrons, neutrinos). The strong force's most familiar manifestation is to bind the nuclei of atoms together, acting there as an attractive force. The weak force governs neutron decay, electron-neutrino scattering, and other similar sorts of things. These forces involve the exchange of massive particles, which means they have a limited range, unlike electromagnetism and gravity.


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Copyright © 1998 John F. Hawley