If the Sun Became a Black Hole, Earth Would Keep Orbiting and Freeze
From a distance, gravity depends on mass, so our planet's path would barely change.
Kurzgesagt – In a Nutshell · Black Holes Explained – From Birth to DeathSwap the sun for a black hole of the same mass, and Earth would keep circling as if nothing had happened. The orbit would barely shift. The sunshine would vanish, and we would freeze to death in the dark.
A black hole does not pull distant planets inward the way a vacuum cleaner pulls dust. From far away, what matters is how much mass is pulling and how far away it is, not what the mass looks like. With the same mass in the same place, Earth's year and orbit would stay nearly the same, but cold and dark.
Questions people ask
Why wouldn't Earth get dragged into the black hole?
Earth stays in orbit because its forward motion balances the pull of the same amount of mass at the same distance. With the mass unchanged, the pull is unchanged, so the orbit continues. Only something that wanders much closer to the black hole would be in danger of falling in.
Why would we freeze if the gravity stayed the same?
We would freeze because the sunlight and heat would stop, and almost all of Earth's warmth comes from the sun. Gravity would hold Earth in place, but it provides no warmth. Without sunlight, temperatures would fall fast, the oceans would freeze over, and plants could no longer grow.
Could people survive for a while with artificial heat?
There would be no daylight, no seasons of sun, and no solar power. People could last for a while with nuclear power, geothermal heat, and shelter, but civilization as we know it depends on the sun's steady energy.