The circumference of Earth is \(1 /7\) s of a light-second. Therefore, a. if you were traveling at the speed of light, you would travel around Earth 7 times in 1 second. b. light travels a distance equal to Earth's circumference in 1/7 second. c. neither a nor b d. both a and b

The circumference of the Earth is the distance around its equator. In this exercise, it is given that Earth's circumference is exactly \( \frac{1}{7} \) of a light-second. To understand this, let’s break it down: If you imagine light traveling a certain distance in one second (known as a light-second), then the Earth’s circumference is one-seventh of that distance. This comparison helps to visualize how vast the speed of light is. Remember, the actual numerical value for Earth’s circumference, which is approximately 40,075 kilometers, fits into this proportional relationship in the context of light traveling in one second.

By relating Earth’s circumference to a light-second, we can intuitively grasp distances on a cosmic scale, making such massive measurements more comprehensible.

A light-second is the distance that light travels in one second. Light travels at an astonishing speed of about 299,792 kilometers per second (km/s). Therefore, a light-second is approximately 299,792 kilometers.

This unit of distance, 'light-second', is essential in fields like astronomy where distances are vast and difficult to measure using everyday units like kilometers or miles. By using light-time units, such as light-seconds, light-minutes, and light-years, we can better conceptualize the immense scales involved in space.

In our context, if Earth’s circumference is \( \frac{1}{7} \) of a light-second, this implies that light would take one-seventh of a second to travel around the Earth once. Understanding light-seconds can provide a clearer perspective on both the enormity of space and the impressive speed of light.

Travel time refers to the duration it takes for something to move from one location to another. In this exercise, we are concerned with how long it takes for light to travel around the Earth. Given that Earth’s circumference is \( \frac{1}{7} \) of a light-second, light, traveling at its constant speed, takes exactly one-seventh of a second to circle the Earth.

To put this into perspective, if you could travel at the speed of light, you would complete one full orbit around the Earth in just \( \frac{1}{7} \) of a second. Thus, in a single second, you would be able to travel around the Earth 7 times. This concept illustrates both the incredible speed of light and introduces students to sophisticated ways of thinking about time and space.

Relating travel time to familiar concepts like the Earth's circumference and the speed of light helps us understand and appreciate how vast cosmic distances are and how quickly light can cover them.