Balck Holes too soft - Page 5

Sirkit · #41 April 3rd, 2001, 12:21 AM

Of course I ment detection from Earth, but a quick point of order all black holes have an accreation disc, this area in with space is warped by the intence gravity exists wether there is something there on not the size of this area is determined by the overall desity of the hole the shape is determined by its rotation, also time is warped arount the hole this may affect how quickly the crew of a ship can respond and how quickly the signal they transmit will reach the general empire but in general loosing a ship to a black hole wouldn't be a common thing if the captain has some idea of stellar cartography and how vectors work, if he/she doesn't he/she shoudent be in space!

Now to the statment that black holes are in the middle of nowhere, not really, black holes are thought to exist in the center of our galaxy. Since early stars witch would form early in the universe time scale would be massive black holes should be damn near everywhere, assuming that the large stars were even half as plentiful as the ones witch exist now they may in fact be in the area of several thousand in the general vacinity of Sol (an estimate I will admit).

Suicide Junkie may I ask where you knowlege of stellar phenomenon is derived?

TallTroll · #42 October 10th, 2001, 03:32 PM

Tee-hee-hee, cool thread! To throw another twist in, did you know that is it perfectly possible (at least theoretically) to make minute BHs?

A BH forms when the gravitational forces in a region of space become so large that the energy required for anything to escape becomes infinite.

Normally, the only way to do that is to pile so much mass up in a small volume that gravitational collapse results (ie big stars going nova, then collapsing back all the way)

But...on totally the other end of the scale, hands up those who know which parameter of a photon is inversely related to its energy?...Yes, you boy

Please Sir, wavelength!

Correct, boy! So, as wavelegth decreases, energy increases. As e=mc^2, we see that a photon of a given energy can be said to possess the equivalence of a certain amount of mass (as well as a tiny amount of "real" mass - thats why solar wind works).

A photon can also be said to occupy (on average) a small, finite volume of space at any time. It therefore possesses a calculable "density" (mass/volume=density, e=mc^2, =>(e/c2)/volume=density).

If its wavelength can be sufficiently reduced, and its energy thus increased to the point where that density is high enough to cause gravitational collapse, voila, a microscopic BH!

In case you are wondering, yes photons DO undergo gravitational interactions, hence the already referred-to "gravitational lensing" effect, so this is (sort of!) feasible

I seem to remember reading that the particle accelerator that could actually get a photon up to the required speeds would need to stretch out about as far as the orbit of Pluto... so no worries just yet!

BeeDee10 · #43 October 10th, 2001, 06:50 PM

quote:
Originally posted by TallTroll:
But...on totally the other end of the scale, hands up those who know which parameter of a photon is inversely related to its energy?

Actually, I suspect you wouldn't be able to get a photon pumped up to a high enough energy to collapse it into a black hole. High-energy gamma rays have a tendancy to decay into electron-positron pairs (the reverse of the antimatter annihilation reaction), with the chances of pair formation going up with the photon's energy. I've never heard of the possibility of black hole formation, so I suspect that photons would decay before they reach that point.

Suicide Junkie · #44 October 10th, 2001, 08:17 PM

quote:
Now to the statment that black holes are in the middle of nowhere, not really,
...
they may in fact be in the area of several thousand in the general vacinity of Sol (an estimate I will admit).
Suicide Junkie may I ask where you knowlege of stellar phenomenon is derived?

This is kind of late, but since the thread's resurfaced, and I've noticed that comment, I should respond.

Sirkit, you have almost answered your own question here.
I was not implying that all black holes are "in the middle of nowhere", or denying that there were any near any specific place.
I merely said that the ones that happen to be solitary are hard to detect. If the hole is drifting alone, it will not have an appreciable accretion disk (since there is no nearby source of gas, such as a red giant), and its gravitational influence on its distant neighbours will be minor.
Gravitational lensing would be noticable, but you'd have to be looking right at the hole while stars move behind it.

And yes, I do know that the center of the galaxy is likely a giant black hole, but we were discussing star-scale BHs, so I didn't mention it.

quote:
also time is warped arount the hole this may affect how quickly the crew of a ship can respond and how quickly the signal they transmit will reach the general empire

Sure, a little bit, but even if your black hole was large enough that you could survive the gravitational shear past the event horizon, the delay would only become noticable to humans (fractions of a second) when the ship is less than a few seconds from the event horizon. (eg. from aBHoT)
More important would probably be the fact that the message would take decades to reach home without using the Warppoint you arrived from.

Most of my info in this thread came from "A brief history of time" - S. Hawking (some good blackhole stuff & I belive I quoted it somewhere below), or "Scientific American" magazine for general ideas.

Puke · #45 October 10th, 2001, 09:12 PM

quote:
Originally posted by BeeDee10:
Actually, I suspect you wouldn't be able to get a photon pumped up to a high enough energy to collapse it into a black hole

I thought they were designing a new super collider for that very purpose? i have been hearing an awful lot about 'mini black holes' in the press in the Last 12 months or so. or is that a different principal that is being discussed in the popular science rags these days? I recall them also theorizing that they could use a laser to create mini-black holes.. probably in effect by adding energy to photons, id guess.

------------------
"...the green, sticky spawn of the stars"
(with apologies to H.P.L.)

Kadste · #46 October 10th, 2001, 09:57 PM

Puke,

I think you are right. Check this link
http://www.nature.com/nsu/011004/011004-8.html

The Large Hadron Collider at the CERN physics lab near Geneva is 27 kilometers in diameter. The article states that they will create a black hole every second.

------------------
In difficult ground, press-on;
In encircled ground, devise stratagems;
In death ground, fight.
Sun Tzu (circa 400 B.C.)

BeeDee10 · #47 October 11th, 2001, 05:07 AM

quote:
Originally posted by Kadste:
The Large Hadron Collider at the CERN physics lab near Geneva is 27 kilometers in diameter. The article states that they will create a black hole every second.

Right, but photons are not hadrons. They're leptons, IIRC. Hadrons are big, massive things like protons. They can be accelerated to any energy level one likes; it's only when they're collided at high speeds that black holes might get made, depending on how physics turns out to work (it's not _known_ that black holes will be produced, it's only predicted by some of the proposed theories).

TallTroll · #48 October 11th, 2001, 03:09 PM

>> High-energy gamma rays have a tendancy to decay into electron-positron pairs

True, the Pair Formation Threshold is only 1.022 MeV, but note that this only makes it POSSIBLE for a high-energy photon to decay. An interaction with matter is required to trigger the decay.

Pair production is a collision process, so as long as you are able to keep your photons away from heavy nuclei, you'll be fine.

The real problems occur when you consider that you need either a ridiuclously strong field, or a massive accelerator to achieve the required energy.

We either need to learn to produce stable magnetic fields many orders of magnitude stronger than anything we can manage today, or produce really high quality vacuums. If you need an accelerator than can realistically be measured in AU, you don't have much chance of getting a photon to survive the round trip without hitting something, unless you can COMPLETELY empty the chamber. Even interstellar space has a density of about 1 - 100 atoms/cm3.

As Pluto is about 38.5 AU away (approx. 3.6 billion miles, I think), you can see that you need a VERY clean acceleration chamber for any significant chance of a photon surviving the trip.

Theoretically possible to do it then, but much engineering needed first

Verigen · #49 October 11th, 2001, 04:50 PM

Going back to the original topic of this thread I would say that Black Wholes should neither pull in ships or leave them be. If we were talking in the game sense doesn't a turn just stop time for you and start it for the next player? I would say that in this case the black whole should only slow down the ships perhaps makeing movement half of normal. The damage that they do should also be increased to compensate for the new larger ships being built in the various mods that have been released. No ship should be able to survive a black hole no matter what the size!!!

BeeDee10 · #50 October 11th, 2001, 09:43 PM

quote:
Originally posted by TallTroll:
True, the Pair Formation Threshold is only 1.022 MeV, but note that this only makes it POSSIBLE for a high-energy photon to decay. An interaction with matter is required to trigger the decay.

Cool, I wasn't aware of that detail.

quote:
you can see that you need a VERY clean acceleration chamber for any significant chance of a photon surviving the trip.

But how does one "accelerate" (actually, add energy to) a photon directly once it has been emitted, without having it interact with matter? The only thing I can think of offhand would be by dropping it down an intense gravity well, and it seems somewhat perverse to contemplate sending a photon into a black hole in order to boost it to the energy level necessary for it to turn into a black hole.

I suppose you could also accelerate _yourself_ to near lightspeed, so that the photons you encounter along the way will appear to be so intensely blueshifted that they turn into super-high-energy gamma rays from your frame of reference, but I suspect it will be hard to report what you observe afterward.
I just dabble in this stuff, though, so if I've made any further oversights I will renounce my skepticism gracefully.