Question

The radius of the moon is 1.74x10^6m, the radius of the sun is 6.96 x 10^8m, the average moon earth distance is 3.84 x10^8m and the average sun-earth disatnce is 1.496 x10^11m. What is the apparent angle the diameter of the moon subtends as seen from the earth in units of rad?

Answer 1

I know this is a relatively simple equation but Im missing the answer. Any suggestions I would be so grateful

Answer 2

All the sun stuff is irrelevant in this case.

It doesn't give you the earth radius - so there may be some assumption here:

two options shown below:



You know the distance from earth to moon. You know the radius of the moon.

So if you look at HALF the angle subtended you can calculate it using the Tan function.

Simply double that to get the whole angle.

NOW - the assumption there is that the distance is measured from surface of earth to centre of the moon - which is evidently unsound.

BUT radius of earth is approx. 6*10^6m so the error in distance if oyu include the radius or not, is about 1.5% and will not change the angle very significantly.

Answer 3

E= earth
rm = radius moon
dm = distance to moon