# I Black holes

1. Jul 6, 2016

### Bujon

So having considered the classical depiction of a black hole resembling a whirlpool, my thought process is that a black hole must be a 3-d phenomenon. Therefore I can not see how a event horizon/swirlpool model could be plausible unless the centre of a black hole was spinning and literally was only attracting matter on a 2-d plane. Is it possible a black is more like a bubble in the bath water, an empty vacuum which doesn't actually have an even horizon as such, perhaps magnetic in nature in the 3-d. Be interested to hear your thoughts.

2. Jul 6, 2016

### Drakkith

Staff Emeritus
The event horizon of a black hole is 3d, not 2d. The 2d whirlpool depiction is completely inaccurate. It is not magnetic in nature, but gravitational.

3. Jul 6, 2016

### Bujon

Can gravity pull from a centre point equally 3dimensionally? And is that just down to the mass? If that was the case then whatever your approach to a black hole would mean you were going to be sucked toward it, and the event horizon would be your point of no return, which I can grasp. Just not sure how something could orbit a black hole without seeing stuff from above and below and beyond that black hole on every point on the x and y and z axis being sucked in.

Last edited: Jul 6, 2016
4. Jul 6, 2016

### Drakkith

Staff Emeritus
Of course! That's exactly how it works. Take for example the Earth. Every single point-like portion of the Earth exerts a gravitational force on all objects in all directions, with the force being inversely proportional to r2, where r is the distance between the object and that portion of the Earth. The total gravitational force exerted by the Earth on an object is just the sum of the force exerted by all of these portions.

Contrary to what you've heard or read, black holes do not "suck in objects". Gravity from a black hole works just like the gravity from the Sun. The planets are not being sucked into the Sun, are they? Gravity from a 1-solar mass black hole would be identical to gravity from the Sun until you were closer than one solar radii to the black hole, at which point the gravitational force is simply larger than that of the Sun, increasing further as you get closer to the black hole. Objects still do not get sucked in.

5. Jul 6, 2016

### Bujon

Ok well explained, so a black hole in that case represents a stable system. They are not necessarily 'growing' eating up everything in sight, but more have finished the main course and are now sat bulging on the sofa so to speak.

6. Jul 6, 2016

### Drakkith

Staff Emeritus
You could think of it that way, sure.