Mercury transit 2016: Planet about to make rare appearance as it moves across the sun

The video explains the orbital characteristics of Mercury, highlighting its 88-day journey around the Sun compared to Earth's 365 days. It discusses Mercury's transit between Earth and the Sun, which occurs about three times a year but is rarely visible due to its 7-degree orbital inclination. The transit is only visible with high-powered lenses and lasts approximately 7.5 hours. The video also describes the black drop effect, a phenomenon observed during Mercury's transit.

How long does it take Mercury to move across the sun?

What is the black drop effect observed during Mercury's transit?