Why do astronomers use light-years to measure distances in space?

Question

A. The movement of the stars makes it impossible to measure in Earth units.
B. The speed of light is slow enough to provide accurate measurements.
C. Equipment isn't sophisticated enough to measure any other way.
D. The distances are too great to measure in Earth units.


12. What happens during a lunar eclipse?

A. Earth's shadow falls on the moon.
B. The moon's shadow falls on Earth.
C. Earth moves out of the plane of the moon-sun orbit.
D. The moon moves out of the plane of the Earth-sun orbit.

Answer 1

Am I the only one who finds multiple-choice questions irritating, when the answer offered is imprecise and inaccurate (as (D) is in the first question)?

To say "well it's near enough, tick that box, it will do, it's what they want" is just so antithetical to the Scientific Method. We should be training young scientists to be clear, articulate and accurate, and to query any and every formulation that falls short of those standards.

To try and be more precise than the formulaion in D: the measurements of distance we use depend on what we are measuring,

For Near Earth Objects (asteroids that come close to earth eg) miles kilometres and fractions or multiples of the Lunar Distance (average Earth-Moon distance) are the most appropriate

For distances within the Solar System, fractions and multiples of 1 Astronomical Unit (AU) (93 million miles, the average Earth-Sun distance) are the most appropriate, Thus being told Jupiter is 5 AUs from the sun and Pluto is an average of 39 AUs from the sun are easy to grasp where saying the same thing in millions or billions of miles is much harder to visualise.

For our nearest neighbours in the Milky Way, light years are the most appropriate, Most people know that the trinary system of Alpha Centauri is 4.2 light years away and that Sirius is about twice that, and while the numbers remain of that order of magnitude, comparisons are relatively easy to make,

For distancs across the Milky Way, parsecs are more common. For distances to other galaxies, Kiloparsecs and gigaparsecs are the most commonly used units. You wouldn't use inches, would you?

The second answer is A and the person who pointed out that B describes a total eclipse of the sun made a very helpful distinction, My frustration is that the multiple-choice question format actively discourages this kind of insight from being made and turns knowledge into a commodity, into what you need to know to answer Trivial Pursuits questions and pub quizzes, but without any real understanding of the issues involved.

M-CQs rather lower the tone of the conversation, I would assert!

Answer 2

Why are you asking us?

And, surely, 'Earth units' relates to any unit of measurement in comman usage on the planet Earth, and so would include light years. And astronomical units (approximately the mean distance between the Earth and the Sun).

I am impressed with your grammar, though. You've even got your apostrophes in the right places. I mean, apart from the minor fact that you should end list items with a semi-colon, it's almost spot on. It's a shock to find a correctly spelt word around here.

Answer 3

for the light years, the distances are too great...

during a lunar eclipse the earths shadow falls on the moon

Answer 4

D
A
i don't know why but the a 's are not working for some reason so if you see the * than that is an a

Answer 5

D is the answer for 1'st one. A for 2'nd.

Answer 6

All of this information is in your text book. It would have taken you less time to find it in the text than to type the question and answers.

Answer 7

Actually, professional astronomers tend to use parsecs, not light years.

Answer 8

11. D

12. A

Hope this helps!

Answer 9

D. (the best, if not exactly correct, answer)
A. ( a solar eclipse would be B)

Answer 10

because they can