•3. What is the ratio of the mass of Earth
to the mass of the moon?
(Hint: look in appendix A of the
text for these values.)
•
•Just take the ratio of masses. From table A-6, we have 6x1024 kg/7x1022 kg. 1024/1022 is 102 = 100. 6/7 is just under 1. So the answer is close to, but less than 100,
without needing a calculator.
Scientific notation makes it easy, and often in astronomy
we’re not concerned with super precise answers. Remember that Earth is about 100 times
more massive than the moon, not 81 times, or 60 times, or
whatever. This approach lets you
find the best multiple choice answer quickly.