What Do You Know About Cosmic Rays?

Explanation
The term "cosmic rays" was coined by Robert Millikan in the 1920's. This suggests that it was during this decade that Millikan first used the term to describe high-energy particles from outer space.

Explanation
Cosmic rays are high-energy radiation that mainly originate outside the Solar System. They are composed of protons, electrons, and atomic nuclei that travel through space at nearly the speed of light. These particles are thought to come from various astrophysical sources, such as supernovae, black holes, and active galactic nuclei. While some cosmic rays may penetrate the Solar System and reach Earth's atmosphere, their primary origin is outside the Solar System.

Explanation
The correct answer is 85 because it is the closest percentage to the estimated proportion of protons in galactic cosmic rays (GCRs). GCRs are composed of high-energy particles, including protons, which are the most abundant type of particle in these cosmic rays. While the exact percentage may vary, studies indicate that protons make up around 85% of GCRs, making this the most accurate answer choice.

Explanation
This energy corresponds to speeds greater than 87 percent of the speed of light.

Explanation
GCRs (Galactic Cosmic Rays) are high-energy particles that originate from outside the solar system. They have an average life of 10 million years, which means they can travel through space for that long before decaying or interacting with other particles. To maintain a constant population of GCRs, they must be replenished at an average power level of about 10^41 ergs per second.

Explanation
Supernova explosions are extremely powerful events that release an enormous amount of energy. These explosions occur about every 50 years in the galaxy, making them a significant source of power.

Explanation
The correct answer is 80. It is believed that cosmic rays are made up of a combination of different materials. Among these materials, approximately 80% is thought to have a composition similar to that of the solar system.

Explanation
Physicists divide cosmic rays into two categories. This means that they classify cosmic rays into two distinct groups based on certain characteristics or properties. Without further information, it is not possible to determine the specific criteria used to categorize these cosmic rays.

Explanation
In 1912, Victor Hess conducted a series of experiments using a balloon to measure radiation levels at high altitudes. He observed that the radiation levels increased with altitude, which contradicted the prevailing belief that radiation came from the Earth. This led to the discovery of cosmic radiation, which is a form of high-energy radiation that originates from sources outside of Earth, such as the Sun and distant galaxies. Therefore, 1912 is the correct answer as it marks the year when the existence of cosmic radiation was first discovered.

Explanation
The energy of cosmic rays is measured in electron volts. Electron volts (eV) are a unit of energy commonly used in atomic and particle physics to describe the energy of individual particles. Cosmic rays consist of highly energetic particles, such as protons and electrons, that originate from outer space. Since electron volts are a suitable unit for measuring particle energies, they are used to quantify the energy of cosmic rays. Proton volts and neutron volts are not commonly used units for measuring cosmic ray energy.