The light from a star 100 light years away takes about 100 years to reach Earth. How long will the star appear to us after it explodes (if it explodes now)?
Show answer & explanation
Correct answer: B
Explanation
Correct Answer:
In 100 years
Explanation:
Light travels at a finite speed, meaning the information and light emitted from an event in space take time to travel across the universe. Since the star is 100 light years away, any light or visual signal generated by an explosion happening "now" will take exactly 100 years to travel through space and reach Earth's observers. Therefore, the explosion will appear to us on Earth in 100 years.
Key Points:
A light-year is a unit of distance, not time, representing the distance light travels in one Earth year.
Because of the time delay, we always view astronomical objects as they were in the past, not as they are at the present moment.
Important Questions and Answers:
Question: What is a light-year a measure of?
Answer: Distance (the distance light travels in one Earth year).
Question: If the Sun were to suddenly disappear, how long would it take for us to notice on Earth?
Answer: About 8 minutes and 20 seconds (the time it takes sunlight to travel from the Sun to Earth).