Black Holes: Vacuums of the Universe

• vesc = (2GM/R)1/2

• By Micah Burgdorf

Gravity

• Gravity is the attractive force that all matter produces that pulls toward it other matter.

• Gravity is the basis of a blackhole without The measure of the force of gravity depends upon the mass of an object.

• Mass is sort of like the weight of an object, but without the Earth’s own gravitational pull on the object.

Creation

• There are two forces working in a star, gravity and explosions.

• When the fuel runs out in a massive star (say 3 times the mass of our own Sun), the star explodes in a supernova (a gigantic explosion).

Creation

• The supernova on the outside hides the implosion happening on the inside caused by the gravity.

• The gravity pulls all the matter back into the center only much more dense.

• The decrease of the size of the matter increases the density to the point that space time becomes bent, as in the diagram.

• Space-time forms a hyperbola in the presence of a black hole.

Warps in Space-Time

• All matter can create a warp in the space-time continuum due to their gravitational field.

• Even our own Sun warps space-time, but since it is less dense than a black hole it can not puncture it.

Space-Time Continuum?

• Best if I start at the beginning (not the big bang, that's later). I'm sure you've heard the much bandied about description of this universe wrapped up with the neat little label ‘space time.’ I'm going to ask you to imagine that we're living in a two-dimensional world just like living in a piece of paper. Why? See, space time for a three dimensional world plus the time dimension is a 4D shape, which, understandably, humans have a tough time picturing. Space time for a 2D universe like that paper would be a 3D thing, which I can describe to you rather well (if I do say so myself!). Thus, please, don't tax my poor brain by asking me to describe anything higher than three dimensions.

Space Time Continuum?

• So, we've got this infinite 3D jello-mold of the universe, here, to serve as my analogy (wobble, wobble). Let's take a slice---schlok! What does this slice represent? This is the shape of space time at a certain time. See, over there is a star---see how the jello bends down? Over yonder is a black hole---look at the point on that sucker! See, there, that double-bumped dip is a binary system. These dips in space time are called gravity wells. The presence of matter or energy (lots and lots of energy) warps space time. Anyway, when space time bends, it manifests as something we call 'gravity.' The more stuff, the more bend. The more bend, the more gravity. If you get enough stuff within a certain area, you pop! right through the jello slice and get a black hole.

Why are They Black Holes?

• It is said that black holes have such strong gravity that not even light can escape one.

• Yet light has no mass to be attracted by the black hole.

• It is the warp in Space-Time that captures light. The warp transforms all straight lines into curved lines.

Why are They Black Holes?

• So the straight path that light follows becomes curved, some rays become stuck in an orbit (Photon Sphere).

• In the pictures to the right you see an actual star (the medium sized dots) and their images (the smaller dots).

• These images are made from the light of the stars moving toward the black hole are sent around the black hole (the large dot).

Warped Physics

• When one reaches the Event Horizon (not the terrible movie, but the radius in which nothing not even light can escape its warp), all of the normal laws of physics will be thrown out the window.

• For these conditions new equations need to be created. For this position physicists such as Karl Schwarzchild, Reissner-Nordstrom, and Kerr.

• We’ll go into them later.

Karl Schwarzchild

• Before we get into the most basic type of black hole, I would like to introduce Karl Schwarzchild.

• Karl Schwarzchild created the Schwarzchild Radius. This radius, described by the formula Rs=GM/c2, is the position of the event horizon. Where G is the gravitational constant, M is the mass of the Black hole, and c is the speed of light.

Static Black Holes

• Static black hole have only one event horizon and one photon sphere.

• There’s nothing out of the ordinary with this class.

• The event horizon is one Schwarzchild Radii from the singularity. While photon sphere exists 1.5 Radii from the singularity.

Charged Black Holes

• Charged- Instead has Two event horizons! In between the two one can move forward and backward through time as easy as walking.

• Since this has a charge we must consult Reissner-Nordstrom.

Reissner-Nordstrom

• According by Reissner-Nordstrom the two event horizons are a result of the charge.

• Now here is the interesting part, as the charge grows and approaches the mass of the black hole the event

horizons begin to merge together.When the charge exceeds the mass the event horizons disappear! This means that something would be able to move in and out at will.

Rotating Black Holes

• Rotating black holes have two event horizons and Two Photon Spheres! The second sphere and horizon is created by the dragging of space-time behind the black hole as it spins.

• But there is also something called the Ergosphere.

Ergosphere?

• The outer boundary of the ergosphere is the static limit of the rotating black hole. What's a static limit? It's where you can no longer stay still, even if you were going at the speed of light. For static black holes the static limit is the event horizon, since after you cross that, even if you go the speed of light, you are pulled towards the singularity.

However, you can enter and leave this region whenever you like, unlike the abandon-all-hope-ye-who-enter-here static limit/event horizon of the other two black holes. You can merrily weave in and out of the ergosphere with no nasty side-effects. It's a place of quirky space time of the black hole that we

can actually visit and leave.

How Can We be Sure?

• We can be sure that blackholes exist not only for the fact of mysterious eclipses of stars or that strange images, but also some massive stars have been seen orbiting invisible objects.

Uses

• If humanity should ever actually reach a black hole there are speculations as to the possible uses for such a phenomenon.

• A black hole could be used as a dumpsite or there are theories to use it as an immense power source since it contains a great deal of

compressed atoms. There is even talk that a black hole can be used as an inter-dimensional gateway. This would make definate use of a charged black hole.

Bibliography

• For more information try these sites:

• <http://www.physics.syr.edu/courses/PHY312.985pring/projects/jebornak/>

• <http://archive.ncsa.uiuc.edu/Cyberia/NumRel/EinsteinTest.html>

• <http://casasrv.colorado.edu/~ajsh/home.html>

• Now I think your brain deserves a rest.