According to the law of Universal Gravitation, what would happen to Earth if the sun were somehow replaced by a black hole of the same mass?

Question

wolfe8 · Answer

Welcome to OpenStudy. This is more of a physics question but let's think of what the gravitation law is. Can you state it?

aayushi.somani · Answer

Our Sun is actually too small to end up as a black hole. It simply does not contain enough matter to exert that kind of gravitational force on itself. A star has to be more than about 10 times the mass of our Sun to become a black hole.If the Sun were somehow compressed enough to become a black hole, it would be less than 6 kilometers (well under 4 miles) across. It would exert no more gravitational force on Earth or the other planets in the solar system than it does now. Why? Because it would contain no more matter than it does now and it would be no closer to the planets than it is now.

wolfe8 · Answer

I was thinking this was more of a trick question. Since gravity depends on the mass of earth and the sun/black hole (distance is same here), the gravity would be the same and so nothing happens. Except we lose out energy source of course.

aayushi.somani · Answer

@wolfe8 black hole is something which is so compact that even light cannot pass through it.. and black holes r much larger then the size of our sun..! if a blackhole of the size of our sun then it would be a very small blackhole..as i stated earlier.

wolfe8 · Answer

But look at the question. It's asking based on the law of gravitation, which is the product of the two bodies' mass over the distance between them. Since both distance and mass are the same, it shouldn't change anything in terms of gravitational pull.

aayushi.somani · Answer

see thats what i am saying the distance would not be the same..! black hole is compact..! soo the diameter of sun would decrease to about 10km..!

wolfe8 · Answer

But we take the bodies as point mass in calculation in this theory.

aayushi.somani · Answer

but if we are taking black holes in note.. how will u consider it a point mass?? then according to this there would be no difference between both the situations while there is a lot of difference.