More important - the most powerful cosmic rays we've detected (and we've only been looking for about 50 years) has something like 50 times more useful energy than anything we're likely to produce in a collider in the next 10 years. Since the Earth is still in one piece after lots of similar events over its 4.5 billion year history, we're in no danger of harming it with particle colliders any time soon.
I've studied Astronomy. The Chandrasekhar limit is a classic piece of Astrophysics that should be part of any popular article discussing the limiting size of an object becoming a black hole. I don't know of a mechanism that might cause a smaller body to form a black hole. That force would need to be applied in such a way as to overcome electron degeneracy pressure. How about a supernova? Let's say our Sun turns into a red giant, burning helium into carbon. Eventually it runs out of helium and the giant star (with a surface out around Earth or Mars) collapses rather suddenly (at least it's suddenly compared with its 10 billion year life). While a 1 solar mass lump of stable matter is below the Chandrasekhar limit and can't become a black hole, a 1 solar mass star could, in theory, compress its core enough to make a black hole of arbitrarily small size during its death throes.
Mind you, people have done calculations about this and they're pretty sure a 1 solar mass star can't create a black hole. What they don't know is the minimum sized star that will turn its core into a black hole, nor how much of the core collapses while the rest explodes out. That's what they're trying to find out. At least, that's my understanding.
Perhaps you can answer a question for me. If I understand the concept correctly (and stop me where I go wrong), the event horizon can be defined as the point where any light that were to be ejected (I know, I know not possible) from the singularity perpendicular to the tangent (straight "up") would stop and return. This is the Newtonian description of a black hole. The relativistic description is considerably more complicated. First of all, you must always start any relativistic description by stating your reference frame - i.e. who is making the observations? The Schwarzschild metric (which is the standard non-rotating black hole) takes the observer to be someone infinitely far away and not moving relative to the black hole.
According to that observer, there is a singularity at the event horizon. Anything inside the horizon is effectively in a different universe. Anything outside of it takes an infinite amount of time to fall all the way to the horizon. As stuff gets closer to the horizon, its time rate slows down and the radiation it emits gets red-shifted.
There's no point in saying what the distance from the horizon to the singularity is in this frame of reference because the horizon IS the singularity. Equally, the space inside had no volume; in fact, the "space" inside isn't even space-like, whatever that means.
Given the relativistic time stretching effects that this implies, as I understand it, anybody falling in would experience "the end of the universe" as time around him speeds up infinitely. Now we're in a new frame of reference, that of the person falling in. In this frame of reference, the event horizon is nothing special. In fact, for the huge black holes theoretically at the centers of galaxies, someone falling through the event horizon doesn't notice much at all, even the tidal forces are fairly tame. As far as they are concerned, time keeps marching on happily and they keep falling, and their only discomfort is the increasing tidal forces they experience. Also, the rest of the universe slows down. They categorically do not see the end of the universe.
They also never see the singularity. If they fall feet first, they don't even feel their feet hit the singularity as their brain hits the singularity before light can travel from the space-time event of "foot hits singularity" to the brain. I can do the proof, but I'm not entirely sure I understand this concept.:) This is irrelevant however since tidal forces will rip them up before they hit the singularity.
My question is, assuming that I am not simply mistaken about the relativistic effects of the event horizon, is; what happens to that item falling into the black hole when the black hole evaporates? That's a very good question. In principle, the answer is that anything that falls into the black hole hits the singularity and gets utterly destroyed. There's a lot of concern about what really happens to the "information" about what went in, but it's probably irrelevant to your question. Whatever comes out, it's not what you or I would consider to be recognizable based on what went in. If you fall in, you won't reappear after the black hole evaporates. Instead, a slew of random (or possibly not so random) elementary particles with the same total mass that you had will be emitted over the course of trillions of years. It's a brilliant paper shredder.
Given that the Sun's outer layers are made up mostly of plasma (the high temperatures strip almost all of the electrons off the hydrogen and helium atoms), generating electric currents is not an issue.
On the other hand, while electric fields are obviously present, they are weaker than the magnetic fields. The Sun has (essentially) no net charge. The electric fields are primarily created by the changing of the magnetic fields. This is generally a second order (ie. weaker) effect than the original magnetic fields. So when one is trying to get some basic understanding of the situation, ignoring the electric fields and focusing on the magnetic fields is a decent approximation to make.
No, this anti-matter cannot form stars. According to the Nature paper, the anti-matter is purely positrons. No anti-protons, so it can't form anti-hydrogen.
The gist of the paper is: we see lots of gamma rays that correspond to electron-positron annihilations. This glow is not symmetric. It has more or less the same distribution as a class of exotic systems which are capable of producing a lot of energy. If some of that energy is converted into electron/positron pairs, and if the positrons can escape the system and reach the "safety" of interstellar space, they should form a cloud which is about the right shape to match this glow.
I read (some of) the Nature article. They are not using the spectrometer data at all - except by way of saying "there really is ice there". What they are doing is measuring, using infrared cameras only, how quickly the surface changes temperature due to seasonal changes. Water (ice) has a huge specific heat capacity, so it changes temperature more slowly. The more ice mixed in with the dust/rock, the more slowly it changes temperature.
To get depth, they note that the surface temperature changes first, then the temperature change slowly trickles down to deeper layers. So stuff that changes temperature really fast has no matter near the surface, stuff that changes slow has some water near the surface, and stuff that changes initially very fast but then stops and lets everything else catch up and surpass it has ice but its buried deep.
Naturally it's more complicated than this. They used computer simulations to help figure out what their observations probably meant in terms of amount of ice and depth of ice, but that's the gist it (as far as I can tell).
1) What's the minimum spot size of the laser at that range? I'm guessing it's the 10cm to 1m range. I don't know about pointing out the interesting bits...
2)...but I think the potential for shaping the large spot size should not be ignored. From now on, every movie is a Godzilla movie!
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More important - the most powerful cosmic rays we've detected (and we've only been looking for about 50 years) has something like 50 times more useful energy than anything we're likely to produce in a collider in the next 10 years. Since the Earth is still in one piece after lots of similar events over its 4.5 billion year history, we're in no danger of harming it with particle colliders any time soon.
Given that the Sun's outer layers are made up mostly of plasma (the high temperatures strip almost all of the electrons off the hydrogen and helium atoms), generating electric currents is not an issue.
On the other hand, while electric fields are obviously present, they are weaker than the magnetic fields. The Sun has (essentially) no net charge. The electric fields are primarily created by the changing of the magnetic fields. This is generally a second order (ie. weaker) effect than the original magnetic fields. So when one is trying to get some basic understanding of the situation, ignoring the electric fields and focusing on the magnetic fields is a decent approximation to make.
No, this anti-matter cannot form stars. According to the Nature paper, the anti-matter is purely positrons. No anti-protons, so it can't form anti-hydrogen. The gist of the paper is: we see lots of gamma rays that correspond to electron-positron annihilations. This glow is not symmetric. It has more or less the same distribution as a class of exotic systems which are capable of producing a lot of energy. If some of that energy is converted into electron/positron pairs, and if the positrons can escape the system and reach the "safety" of interstellar space, they should form a cloud which is about the right shape to match this glow.
It's up now: http://www.nature.com/nature/journal/v451/n7175/full/nature06490.html
I read (some of) the Nature article. They are not using the spectrometer data at all - except by way of saying "there really is ice there". What they are doing is measuring, using infrared cameras only, how quickly the surface changes temperature due to seasonal changes. Water (ice) has a huge specific heat capacity, so it changes temperature more slowly. The more ice mixed in with the dust/rock, the more slowly it changes temperature.
To get depth, they note that the surface temperature changes first, then the temperature change slowly trickles down to deeper layers. So stuff that changes temperature really fast has no matter near the surface, stuff that changes slow has some water near the surface, and stuff that changes initially very fast but then stops and lets everything else catch up and surpass it has ice but its buried deep.
Naturally it's more complicated than this. They used computer simulations to help figure out what their observations probably meant in terms of amount of ice and depth of ice, but that's the gist it (as far as I can tell).
1) What's the minimum spot size of the laser at that range? I'm guessing it's the 10cm to 1m range. I don't know about pointing out the interesting bits...
...but I think the potential for shaping the large spot size should not be ignored. From now on, every movie is a Godzilla movie!
2)