Bug 434991

SUMMARY
The answers in the solar system activity have inconsistent units, and the numbers don’t always correspond to the units used. Some questions use ‘days’, others ‘Earth days’. Some questions use ‘years’, other ‘Earth years’. For the questions that use ‘days’, the answer is actually wrong: The numbers listed seem to correspond the number of Earth days, not the number of days. (Though I haven’t checked all questions.)

For example, the question ‘How long is a year on Mercury?’ have the response options in ‘days’ units, ‘365 days’, ‘433 days’, ‘88 days’ and ‘107 days’, with ‘88 days’ as the ‘correct’ answer. But the *actual* correct answer is ‘88 Earth days’ (which is actually only 0.5 (solar) *day*, since Mercury spins so incredibly slowly). Source: https://solarsystem.nasa.gov/planets/mercury/in-depth/
On the other hand, the question ‘How long is one rotation on Mercury?’ (correctly) lists the response options in ‘Earth days’ units, with ‘59 Earth days’ as the correct response.

(BTW, note that this is different than the ‘Day’ value listed on the NASA site. The ‘Day’ is the number of *solar* days, i.e. the time needed for the sun to return to the same place in the sky, which is 176 Earth days, but the planet only needs ~59 Earth days to complete a rotation.)

The same hold for the ‘years’ value. This needs to be changed to ‘Earth years’. (If not, the answer to all the questions would obviously all be ‘1 year’ …)

STEPS TO REPRODUCE
1. Launch the solary system activity.
2. Click on a planet.
3. Answer the questions until you get a ‘How long is one rotation on PLANET?’ or ‘How long does it take for PLANET to make one revolution around the Sun?’.

OBSERVED RESULT
Some response options are days, some Earth days, some years and some Earth years.

EXPECTED RESULT
The only two response options should be Earth days and Earth years. (Except for the questions about Earth itself; then they can be ‘days’. I think having ‘Earth days’ here would be confusing, though not incorrect.)