| From: Craig | 4/02/99
12:19:22 |
| Subject: Singularities | post id:
280 |
| What is a
singularity? | |
| From: Jason from Hobart | 4/02/99
12:22:21 |
| Subject: re: Singularities | post id:
282 |
| The way I understand it, a
singularity is supposed to be the "core" of a black hole. It's matter from
the collapsed star that has been compressed to a "point in space" that
doesn't follow the "normal" laws of the
universe. Jason | |
| From: steve | 4/02/99
12:34:57 |
| Subject: re: Singularities | post id:
290 |
| Mathematically, a singularity is
a point on a function which is infinite. For example, tan(90degrees). More accurately, it is a point that approaches infinity as x approaches y. | |
| From: James Richmond (Avatar) | 15/02/99
22:36:23 |
| Subject: re: Singularities | post id:
1252 |
| Singularities can arise in the
mathematics describing a physical system in two ways. Firstly, we can make
a bad choice in how to model the system mathematically. For example, our
model might omit an important part of what is physically happening in the
system, either because we didn't think of it, or thought we could safely
ignore it. In the general relativistic analysis of black holes,
singularities can arise due a bad choice of a reference frame in which we
choose to look at the hole. Such singularities are problems with the mathematics, and do not relate to any problem in the real world. In other words, these singularities are "removable". For example, suppose we analyse the motion of an object falling into a black hole. If we choose to look at the motion from the point of view of a stationary observer outside the hole, the mathematics predicts that it will take the infalling object an infinite amount of time to reach the event horizon. This is a singularity due to a bad choice of reference frame. We can fix the problem and remove the singularity by looking from the point of view of the infalling object. In its own reference frame it falls through the event horizon and to the centre of the hole in a finite time, and nothing special happens at the event horizon. The second type of singularity is real, and tells us something about the physical system we are studying. The singularity at the centre of a black hole is non-removeable - it's always there no matter which reference frame we use. This means that the laws of physics as we currently understand them break down at the centre of a black hole. At present there is no known way to get rid of this singularity. Perhaps we will eventually manage to do so when we find a satisfactory theory of quantum gravity. In any case, we know that something interesting is going on at the centre of a black hole. | |
| From: Martin Smith | 16/02/99
13:00:51 |
| Subject: re: Singularities | post id:
1292 |
| Jame's said The singularity at the centre of a black hole is non-removeable - it's always there no matter which reference frame we use. This means that the laws of physics as we currently understand them break down at the centre of a black hole. At present there is no known way to get rid of this singularity. Perhaps we will eventually manage to do so when we find a satisfactory theory of quantum gravity. This seems a bit ambiguous. If the singularity is 'non-removable', how can it perhaps one day be removed? The singularity may not be real. As you say all that may be lacking is the understanding (the theory if you like). Current theory is unable to say what is going on. No matter what model we use it tends to a singularity. That does not mean that such a model does not exist. Martin | |