Does mass matter to measure mass?

January 2025

We ran this question in October 2023 and couldn’t believe no one got it right. So let’s try this again.

Q: The two spacecraft of the Gravity Recovery and Interior Laboratory mission were identical, according to NASA. They had to have the same mass to do their job of accurately measuring variations in lunar gravity. True or false, and why?

Send a response of up to 250 words to aeropuzzler@aerospaceamerica.org. By responding, you are committing that the thoughts and words are your own and were not created with the aid of artificial intelligence. DEADLINE: noon Eastern Jan. 17.

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FROM THE DECEMBER ISSUE:

We asked you to play a fictitious game that requires stringing together relevant words into a sentence and leaving out any extraneous words. We didn’t receive any valid responses, so we asked John Hansen of Keysight Technologies to show us his answer. Words from the game are in red in his sentence below.

“Reynolds Number is the only phrase that would not fit in my sentence: Based on the ground-breaking work of 19th century Austrian mathematician Christian Doppler, we know that the frequency of an acoustic or electromagnetic wave shifts when a transmitter and receiver/reflector are in motion relative to other just as the frequency of the horn of a passing train shifts frequency, and this phenomenon can be tapped to find exoplanets through Doppler Spectroscopy or find objects in motion using Moving Target Indicator (MTI) radar.”