If every galaxy out there each became a single black hole...?

Question

would they then be attracted back together and possibly recycle the whole universe?

Answer 1

Simple answer: no.

It is a common misconception that a black hole is an infintely powerful attractor and that everything gets sucked in. This is simply incorrect. Hold on to your hat; this may get complicated, but I'll keep it as simple as I can.

All mass has a gravitational force. Let's concentrate on a planet, like Earth. There is a huge amount of material there, and it has gravity. Gravity acts to attract towards the centre of the mass, so on Earth all objects are attracted to the centre of the planet. The force of attraction depends on the mass of the object and the distance you are from the centre. The closer you are the greater the force.

The Earth's gravity holds you on the surface but also holds the Moon in its orbit 250,000 miles away. The force the Moon feels due to Earth's gravity is considerably less than the force you feel standing on the surface. This force you feel is called your weight.

Now let's imagine that you can compress the Earth to one half its present size. All the matter is now concentrated in a smaller space. How does that affect things? Well, to you on the surface you would feel heavier, because you are now closer to the centre of mass of the Eartrh. But the Moon is still 250,000 miles away, and the Earth's mass has not changed, so the Moon still feels the same force from Eartrh's gravity as it did before.

If you halve the Earth's size again you will get even heavier, but the Moon still feels the same force from the same mass because it has not changed its distance from the centre.

A black hole comes about after a particularly massive star exhausts its fuel and collapses under its own gravity. A vast amount of matter is compressed into a tiny space. Now you can get much closer to the centre of mass, and so now you can get close enough to feel a much greater pull of gravity than you could before the star collapsed. But if, for instance, the star had a planet around it, that planet would continue merrily in its orbit because the mass of the black hole is the same as the mass of the original star, and hence the planet still feels the same gravitational force (in fact it would feel less because there is always some loss of mass during the collapse of the star, so it would actually move away).

So, to answer the original question, if all the galaxies became black holes they would still feel the same pull of gravity from each other because the black hole cannot have more mass than the original object that collapsed to form it.

Answer 2

No, black holes have the same mass and gravitational attraction as the original object. They would have the same motion as before. They don't hunt down things to suck them in.

Answer 3

Eventually all the black holes would merge forming one giant black hole and sit for eternity doing nothing
Black holes are useless celestial bodies that do not exist

Answer 4

no. black holes have the same mass as the object they were created from so they would have the same gravitational field strength.

Answer 5

no, the mass will be the same, just more concentrated, so the gravitational forces will be the same.

Answer 6

No.