Question: Wait, since the Sun will begin to expand (during the forming of a black hole). How will it eventually engulf Earth? Wouldn't the Earth's orbit around the Sun grow bigger while the Sun while the Sun is expanding, and grow small when the Sun runs out of helium and starts to shrink into a White Dwarf Star?

Hayley Evers-King answered on 12 Mar 2013:

The sun will expand, but it won’t get more ‘massive’ so its gravity won’t change and the orbit of the Earth will stay the same. The sun will have the same amount of mass as it does now, but the area it takes up will be bigger and engulf the Earth. Think about how much space a tonne of feathers would take up, compared a tonne of bricks, they would weigh the same (a tonne) but you would need a lot more feathers and they would take up more space. The sun will also never form a black hole, it’s just not big enough, more likely it will form a white dwarf (as you say) and these don’t form black holes.