Better blackholes

[TimeLaw]

So I thought about trying to make a black hole, and I must say I was very disappointed about how it turned out.

It swings around the planets like crazy instead of absorbing their mass, even though they are way inside the event horizon. I hope you manage, and that you are willing to, update the blackhole system so that the blackholes have their own mass unit size, 1 blackhole etc, and that you add an event horizon to blackhole objects.

The event horizon is the edge of where an object can't escape it's gravity anymore. Outside the event horizon it can, even if it's really hard, still escape it's pull. But once inside it's impossible. I was thinking about simulating a blackhole being launched towards our solar system and see what happened, but instead I got the same result as if I had launched a regular sun.

[Bla]

I'm not sure, but maybe the event horizon is at the surface of the body which is a black hole? That would make sense visually at least.

The mass unit "1 black hole" wouldn't work, because black holes can have very different sizes, so there isn't any reason to make any specific black hole value the basis for the unit. A "black hole" would work better as a unit for escape velocity, but then it'd be the speed of light.

Outside the event horizon, the black hole affects all other bodies just like any other body, which is also how it is in the real universe. The gravity of a black hole isn't different from the gravity of a star, it's still gravity. It's only inside the event horizon that it gets different, because nothing can escape from it.

You can simulate objects getting eaten by the black hole by enabling the "combine" collission mode, just in case you didn't know.

[atomic7732]

Maybe we should make a topic called Common Astronomy Misconceptions, and sticky it? It just seems like there are alot of posts on the same things over and over again. (No offense meant to anyone at all)

[TimeLaw]

I'm not sure, but maybe the event horizon is at the surface of the body which is a black hole? That would make sense visually at least.

The mass unit "1 black hole" wouldn't work, because black holes can have very different sizes, so there isn't any reason to make any specific black hole value the basis for the unit. A "black hole" would work better as a unit for escape velocity, but then it'd be the speed of light.

Outside the event horizon, the black hole affects all other bodies just like any other body, which is also how it is in the real universe. The gravity of a black hole isn't different from the gravity of a star, it's still gravity. It's only inside the event horizon that it gets different, because nothing can escape from it.

You can simulate objects getting eaten by the black hole by enabling the "combine" collission mode, just in case you didn't know.

It is enabled, and I always have it enabled. It still doesn't do anything but swing stuff around. And in any case, I was at a class or something where a guy with some certain title in this sort of thing explained to us that the event horizon isn't at the surface, it's on a distance around it, and that distance is defined by the mass of the blackhole, of course.

And it would make sense in the game, yes, but in reality it would not. As all light is absorbed at the event horizon it seems that the blackhole is much bigger than it actually is, but the objects and light itself just can't be seen, as it can't escape the area.

Sorry for posting in the wrong category. I thought I had this selected and was looking for it like crazy after I posted it and finally found it in the wrong one. Thanks for moving it though

This guy had some big degree in Relativity Theory, both the "regular" one and the "special" one. I'm just saying what he said, and what I remember of it. I just know that it made a lot of sense when I was listening and when I saw how it worked here I was a bit annoyed.

[Bullethead]

Question:  What mass was your black hole?

When you hit the button to turn an object into a black hole, it keeps its original mass, The vast majority of stock obects in US are way too light to become black holes in real life, so you get ridiculous results with them.  You'll see a message pop up saying the radius was changed to make the math work and this is always a HUGE reduction in size.  For instance, if you turn Earth into a black hole, it'll be about 2mm radius, meaning it will only have weird gravity effects within a few millimeters of its surface. Beyond that, it's just normal Earth gravity.

So, to make a system-eating black hole, you need a lot of mass.  Pick some huge star to begin with (I think the biggest only have about 25 solar masses) and jack the mass up to 200 solar masses or so.  THEN turn it into a black hole.

[TimeLaw]

Question:  What mass was your black hole?

When you hit the button to turn an object into a black hole, it keeps its original mass, The vast majority of stock obects in US are way too light to become black holes in real life, so you get ridiculous results with them.  You'll see a message pop up saying the radius was changed to make the math work and this is always a HUGE reduction in size.  For instance, if you turn Earth into a black hole, it'll be about 2mm radius, meaning it will only have weird gravity effects within a few millimeters of its surface. Beyond that, it's just normal Earth gravity.

So, to make a system-eating black hole, you need a lot of mass.  Pick some huge star to begin with (I think the biggest only have about 25 solar masses) and jack the mass up to 200 solar masses or so.  THEN turn it into a black hole.

I know the radius get's changed. And I changed the size of the hole to first 10 suns (it was our original sun I made a blackhole), then reset, changed to 100, reset, 1000, reset, 10000 etc etc. It still would just swing the stuff around and I know the radius get's changed due to the massive density of a blackhole. I even made a new sun, gave it 10000 in size or so and launched it towards our solar system, but it still would just swing the stuff around because it doesn't get eaten when close, it just gets a narrow angle and speed increase and woila, gone!

I really want that event horizon.

[Bla]

The mass of objects are just points, so the mass of a black hole would be a point in the center of its surface.
The surface would make sense to be the event horizon visually. Even though matter orbiting very close to the surface would be extremely warm, and therefore make a lot of radiation.

[eispfote]

Well it doesn't perfectly fit here but still...
When I set the Mass of the Sun to 200M suns, effectivly creating a Black hole, but do not change its state to Black hole it sends all the Objects in the Solar system speeding away. For the effect to take place it also doesn't matter if I lock diameter or density either way it happens. I understand the M stands for million so it should crash the solar system to have a star with 200M suns. Also Venus for example gains a velocity of 323 light which is quite impossible.

[Bullethead]

I think that all the relativistic weirdness only happens at what are relatively very small distances above the event horizon, where the gravity gradient really starts to get steep.  Beyond that, you just have normal physics, although the gravity is pretty strong compared to familiar solar system objects.

So what you should expect to see if you fire a black hole into the solar system is just the gravitational effects of
something that massive going by.  It's not going to suck in anything that's not directly in its path or close enough to get captured into an unstable orbit.  Objects not within this narrow path of destruction are just going to get slingshotted off into the void.  And that's what US shows happening.

[eispfote]

I'm not shooting a black hole in there, I just set the Suns mass to 200M suns. the weird thing is if I do so and press the "turn into black hole" button the planets start spiraling down into it. As they should as the centripetal force was just increased by a huge factor. But if I just invrease the mass and don't hit the "turn into Black Hole" button the shooting out of the system happens.
Edit: seems like I found my mistake... if I turn down the stepwidth it works. My fault for not trying that.

[TimeLaw]

I'm not shooting a black hole in there, I just set the Suns mass to 200M suns. the weird thing is if I do so and press the "turn into black hole" button the planets start spiraling down into it. As they should as the centripetal force was just increased by a huge factor. But if I just invrease the mass and don't hit the "turn into Black Hole" button the shooting out of the system happens.
Edit: seems like I found my mistake... if I turn down the stepwidth it works. My fault for not trying that.

I was the one shooting the blackhole. And by the way, while I still have it on my mind... Shouldn't the gravity have the speed of the light? I heard about an experiment that proved that gravity had a speed, and it was equal to light. And that would mean that it would take 8 minutes for us to notice if our sun had suddenly disappeared, and we would be thrown into space. Is this something you can concider then? I bet you can google the subject. I read it in a science paper some year ago I think.

[Bullethead]

I heard about an experiment that proved that gravity had a speed, and it was equal to light.

Actually, some would say faster...

I don't think gravity itself actually has a speed per se--it's just there.  This is because what we call gravity is just our perception of the curvature of spacetime around hunks of mass.  IOW, gravity is just the topography of space time and is rather analogous to earthly terrain features.  That is, you feel the effects when you're on the slope but nothing radiates out from the slope to make you think you're on a slope when you're not.  Of course, unlike on earth most of the time, spacetime's terrain features move with the hunks of mass, so can come to meet you as when a black hole flies by.  But "relatively" speaking, that's the same as if you moved onto the slope so the analogy still holds.

Now, what DOES move (at least in theory) is a gravitational wave.  These are predicted but so far unobserved ripples in the fabric of spacetime and are supposed to travel at the speed of light.  But this isn't gravity itself.  Here's what Wikipedia says about them:
http://en.wikipedia.org/wiki/Gravitational_wave