Question 326
EasyOriginal questionA light-year sounds like a measure of time, but it is a measure of distance: the distance that light travels in one Earth year. Light is the fastest thing there is, moving at about 300,000 kilometres every second, so in a year it covers about 9 trillion kilometres.
need such a large because the distances in space are so . Sunlight takes about 8.3 minutes to reach us from the Sun, which is about 150 million kilometres away. The nearest star beyond the Sun, Proxima Centauri, is 4.3 light-years away. The Pole Star, Polaris, is about 320 light-years away, and the centre of our own , the Milky Way, is about 26,000 light-years away.
Because light takes time to travel, looking far into space means looking back in time. The Andromeda galaxy, our nearest large neighbouring galaxy, is 2.5 million light-years away, so we see it as it was 2.5 million years ago. One very distant galaxy, called GN-z11, is about 13.4 billion light-years away; its light shows us the universe as it was only about 400 million years after the Big Bang.
What does a light-year measure?
Show the answer and explanation
Correct answer: B
Explanation
"A light-year sounds like a measure of time, but it is a measure of distance: the distance that light travels in one Earth year."
Worth noting
The word "year" is the trap; the passage says plainly it is not a measure of time.
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