1
vote
2answers
73 views

any unique phenomenon when the cores of two planets are aligned with their star's core?

Imagine a line passing through the cores of two planets (in the same planetary system) and their star. Have we ever witnessed this - either with both planets on the same side of the star or on ...
12
votes
4answers
377 views

Doesn't gravity attract objects in space until they collide?

If the formula to calculate the force of gravity of two objects is: $$F1 = F2 = G * (M1 * M2/r^2)$$ Why do planets stay in orbit? Or is there another formula at work?
12
votes
3answers
274 views

Does a planet's mass or gravity affect the height of it's mountains?

According to this Wikipedia page, the top five highest mountains on Mars (and the highest on Venus) are all taller than Mount Everest (and Mauna Kea as measured from the ocean floor). Does a planet's ...