Maybe we could do that. But the laser pulses short and narrow and therefore dense enough are two black holes made of pure light. Two black holes, leaving the scene with the exact speed of light.
Not much different from the already mentioned solution, albeit even cooler.
Black holes have rest mass, made of light or not, so this is impossible. Can you spot the error?
It is true that black holes have rest mass, regardless of the form of mass-energy used to create them. As such it is impossible for them to travel at the speed of light. However the error-hint you give is misleading.
one photon has no rest mass, while a bunch of photons in a box (photon gas) does.
This is true but innaplicable. Making a black hole out of photons requires that the photons are not all moving in the same direction. For an explanation see here. Alternately, simply consider the case where all the energy is concentrated into a single (ridiculously) high energy photon. As you observe, “one photon has no rest mass”. No black hole is formed by a single (unconfined) photon. The explanation is somewhat similar to why you don’t form a black hole if you travel really fast.
You CAN have a black hole made of only photons. Of neutrinos even.
You can indeed (and such black holes are even more cool). However I believe the formation of a black hole from photons requires that the photons aren’t all propogating in the same direction. This is a good thing because if you did have a black hole traveling at the exact speed of light then, well, reality is all broken down. Black holes have rest mass; speed of light travel is off limits. In general it doesn’t really matter (so to speak) whether the mass-energy that they are created from is photons or a mix of paperclips and left over Babyeater offspring.
Imagine a laser beam pulse, 1 nanosecond long. A foot long and an inch tick cylinder of light is traveling with the speed of light, into the darkness of space. When it passes by an atom, there is a brief gravity effects between the two. The atom and the beam.
Now imagine two parallel beams, 1 kilometer long. The gravity effect is even larger. You can pile as many laser beams together, as you wish. You can make them (light) years long. Eventually, the passing atom can’t escape the beam’s gravity field, for the escape velocity is greater than c. The beam is a black hole.
In that case it didn’t form a black hole until it interacted with the atom, and at that moment it slowed down from light speed. How do I know?
Until the atom came along, you’re free to use any old reference frame without complicating matters terribly. So you can arbitrarily red-shift that laser pulse to the point that the energy density is trivial.
If you do that, you shift energy into the atom. So, it’s the collision that allows it to condense into a black hole.
It is rather interesting question, what happens when the pure light black hole interacts with an atom. I have no idea, except that is interesting to consider this kind of questions. What happens under some peculiar circumstances. Do the current theories work there or break down?
As I mentioned before, there is no such thing as a “pure light black hole”. All uncharged black holes are pure vacuum, regardless of how they formed. There are also no beam-shaped black holes (all black holes are spherical in shape, this is a well known result in General Relativity), though a regular black hole can theoretically form from light alone (kugelblitz) under certain rare circumstances.
Your model has a number of technical errors which prevent it from working. For example, you cannot form a black hole by shooting a light pulse from a laser, except maybe by focusing it, in which case the center-of-mass velocity will be sublight and you end up either creating multiple black holes or feeding a single one, depending on the details. Moreover, while light does curve spacetime, it’s not as simple as the gravitational attraction between massive bodies. There are many known solutions which include perfect null fluid (that’s what a continuous beam of light is), none are trivial.
If you still think that you can think up something that 100 years of GR research by the geniuses like Einstein, Hawking and others did not notice, consider learning the subject seriously first.
That certainly works, in theory, though to emit the sun’s mass as light in a short enough time, you will have to outshine a quasar by orders of magnitude (try a Fermi estimate on this). It will probably heat up the dust around the Sun enough to bake and evaporate all of the Solar system in its heat and scattered laser light. Also note that this would not contradict my assertion that stuff has to travel outward, not just disappear.
What if we turn the suns mass into two lasers that shot out equally from the poles?
Maybe we could do that. But the laser pulses short and narrow and therefore dense enough are two black holes made of pure light. Two black holes, leaving the scene with the exact speed of light.
Not much different from the already mentioned solution, albeit even cooler.
Black holes have rest mass, made of light or not, so this is impossible. Can you spot the error?
Hint: bar cubgba unf ab erfg znff, juvyr n ohapu bs cubgbaf va n obk (cubgba tnf) qbrf.
It is true that black holes have rest mass, regardless of the form of mass-energy used to create them. As such it is impossible for them to travel at the speed of light. However the error-hint you give is misleading.
This is true but innaplicable. Making a black hole out of photons requires that the photons are not all moving in the same direction. For an explanation see here. Alternately, simply consider the case where all the energy is concentrated into a single (ridiculously) high energy photon. As you observe, “one photon has no rest mass”. No black hole is formed by a single (unconfined) photon. The explanation is somewhat similar to why you don’t form a black hole if you travel really fast.
There is no error here.
http://en.wikipedia.org/wiki/Kugelblitz_%28astrophysics%29
You CAN have a black hole made of only photons. Of neutrinos even.
I tentatively suggest that there may be an error in a detail here, albeit not the one shminux suggests.
You can indeed (and such black holes are even more cool). However I believe the formation of a black hole from photons requires that the photons aren’t all propogating in the same direction. This is a good thing because if you did have a black hole traveling at the exact speed of light then, well, reality is all broken down. Black holes have rest mass; speed of light travel is off limits. In general it doesn’t really matter (so to speak) whether the mass-energy that they are created from is photons or a mix of paperclips and left over Babyeater offspring.
Of course you can. But they cannot travel at light speed.
The so called Kugelblitz can of course travel with the speed of light.
www.en.wikipedia.org/wiki/Kugelblitz_(astrophysics)
Imagine a laser beam pulse, 1 nanosecond long. A foot long and an inch tick cylinder of light is traveling with the speed of light, into the darkness of space. When it passes by an atom, there is a brief gravity effects between the two. The atom and the beam.
Now imagine two parallel beams, 1 kilometer long. The gravity effect is even larger. You can pile as many laser beams together, as you wish. You can make them (light) years long. Eventually, the passing atom can’t escape the beam’s gravity field, for the escape velocity is greater than c. The beam is a black hole.
Traveling with the speed of light!
You can fix the broken link by escaping the first closing parenthesis:
[a](http://somewhere.com/something(stuff\))In that case it didn’t form a black hole until it interacted with the atom, and at that moment it slowed down from light speed. How do I know?
Until the atom came along, you’re free to use any old reference frame without complicating matters terribly. So you can arbitrarily red-shift that laser pulse to the point that the energy density is trivial.
If you do that, you shift energy into the atom. So, it’s the collision that allows it to condense into a black hole.
It is rather interesting question, what happens when the pure light black hole interacts with an atom. I have no idea, except that is interesting to consider this kind of questions. What happens under some peculiar circumstances. Do the current theories work there or break down?
I don’t know the answer, who does?
As I mentioned before, there is no such thing as a “pure light black hole”. All uncharged black holes are pure vacuum, regardless of how they formed. There are also no beam-shaped black holes (all black holes are spherical in shape, this is a well known result in General Relativity), though a regular black hole can theoretically form from light alone (kugelblitz) under certain rare circumstances.
Your model has a number of technical errors which prevent it from working. For example, you cannot form a black hole by shooting a light pulse from a laser, except maybe by focusing it, in which case the center-of-mass velocity will be sublight and you end up either creating multiple black holes or feeding a single one, depending on the details. Moreover, while light does curve spacetime, it’s not as simple as the gravitational attraction between massive bodies. There are many known solutions which include perfect null fluid (that’s what a continuous beam of light is), none are trivial.
If you still think that you can think up something that 100 years of GR research by the geniuses like Einstein, Hawking and others did not notice, consider learning the subject seriously first.
I haven’t invented a thing in General Relativity, black holes and so on. I have no intention.
We all are just talking and linking here. You have started this thread and you obvously dislike some comments.
Where does the momentum come from to accelerate the atom? From deflecting the photons, which then diverge?
That certainly works, in theory, though to emit the sun’s mass as light in a short enough time, you will have to outshine a quasar by orders of magnitude (try a Fermi estimate on this). It will probably heat up the dust around the Sun enough to bake and evaporate all of the Solar system in its heat and scattered laser light. Also note that this would not contradict my assertion that stuff has to travel outward, not just disappear.