Mine is. :(

Quote: Original post by owl
You just got it all wrong, I never said "don't make assumptions" I said: "I woudln't". What I said before weren't *my* assumptions.

Which theory says that black hole isn't much different than neutron star? As far as I know, light can escape from neutron stars(escape speed ~1/3 speed of light), while it can't from black holes, by definition. That seems like a pretty important distinction to me. Speed of light is not just another arbitrary value, it's a universal constant. Also, we pretty much know what happens in the surface of a neutron star, according to existing theories, while we don't really know what happens inside a black hole, since it needs to merge quantum mechanics and gravity. Again, seems like an important difference. Am I wrong?

Also, where I was not polite? It actually seems you are not the polite one. You started with a pretty rude first post, even though I even apologized from the beginning if my opinions were naive. I just decided not to give it much atention.

Quote: Original post by mikeman

Quote: Original post by owl
You just got it all wrong, I never said "don't make assumptions" I said: "I woudln't". What I said before weren't *my* assumptions.

Which theory says that black hole isn't much different than neutron star? As far as I know, light can escape from neutron stars(escape speed ~1/3 speed of light), while it can't from black holes, by definition. That seems like a pretty important distinction to me. Speed of light is not just another arbitrary value, it's a universal constant. Also, we pretty much know what happens in the surface of a neutron star, according to existing theories, while we don't really know what happens inside a black hole, since it needs to merge quantum mechanics and gravity. Again, seems like an important difference. Am I wrong?

Also, where I was not polite? It actually seems you are not the polite one. You started with a pretty rude first post, even though I even apologized from the beginning if my opinions were naive. I just decided not to give it much atention.

Don't be too distraught. There's more than just overt rudeness in this thread, and somehow I found a way to chuckle at it.

I'll give you an example:

Person A: We have observations, and this has given us a law of nature.

Person B: But consider if it wasn't a law, even though we have never seen anything to contradict it. If this were the case, then we'd need to have to 'X' in order to explain it, even though we have no hope of ever directly detecting 'X'.

Person A: Speculating that 'X' exists in order to justify breaking a law of nature, without any kind of hope for evidence whatsoever, is not science. Stop asking loaded questions, it's rude. Learn how diffusion works, and why it increases entropy over time. Now, consider what anti-diffusion would be, given that it would decrease entropy over time. Don't say gravitation, because gravitation works to increase entropy (a black hole has maximal entropy, not zero). You're out of answers, aren't you? Didn't you say that you're a physics professor? Well, I'm a janitor. Oh well, I hope the book sales are good. Could you pass along some references regarding your academically published work on the subject? Oh there aren't any? Nevermind. Wait, didn't you recently hand out a verbal scolding to pseudoscientists? Altogether, this is a very sad conversation Person B. You should really practice what you preach, and stop confusing the hell of poor [you know who you are].

[Edited by - taby on February 14, 2010 6:54:30 AM]

Quote: Original post by taby

Quote: Original post by mikeman

Quote: Original post by owl
You just got it all wrong, I never said "don't make assumptions" I said: "I woudln't". What I said before weren't *my* assumptions.

Which theory says that black hole isn't much different than neutron star? As far as I know, light can escape from neutron stars(escape speed ~1/3 speed of light), while it can't from black holes, by definition. That seems like a pretty important distinction to me. Speed of light is not just another arbitrary value, it's a universal constant. Also, we pretty much know what happens in the surface of a neutron star, according to existing theories, while we don't really know what happens inside a black hole, since it needs to merge quantum mechanics and gravity. Again, seems like an important difference. Am I wrong?

Also, where I was not polite? It actually seems you are not the polite one. You started with a pretty rude first post, even though I even apologized from the beginning if my opinions were naive. I just decided not to give it much atention.

Don't be too distraught. There's more than just overt rudeness in this thread, and somehow I found a way to chuckle at it.

I'll give you an example:

Person A: We have observations, and this has given us a law of nature.

Person B: But consider if it wasn't a law, even though we have never seen anything to contradict it. If this were the case, then we'd need to have to 'X' in order to explain it, even though we have no hope of ever directly detecting 'X'.

Person A: Speculating that 'X' exists in order to justify breaking a law of nature, without any kind of hope for evidence whatsoever, is not science. Stop asking loaded questions, it's rude. Learn how diffusion works, and why it increases entropy over time. Now, consider what anti-diffusion would be, given that it would decrease entropy over time. Don't say gravitation, because gravitation works to increase entropy (a black hole has maximal entropy, not zero). You're out of answers, aren't you? Didn't you say that you're a physics professor? Well, I'm a janitor. Oh well, I hope the book sales are good. Could you pass along some references regarding your academically published work on the subject? Oh there aren't any? Nevermind. Wait, didn't you recently hand out a verbal scolding to pseudoscientists? Altogether, this is a very sad conversation Person B. You should really practice what you preach, and stop confusing the hell of poor [you know who you are].

Hm...well, you got me confused...what are you saying here? Care to explain it? :P If this is referring to me, I think I did everything I could, I even apologized beforehand for the naiveness of this thread, I just happened to stumble upon some resources that talked about the similarity between big bang/black hole, and most importantly I couldn't figure out why big bang didn't form a black hole by definition. Your answer about entropy satisfied me.

Quote: Original post by mikeman
Hm...well, you got me confused...what are you saying here? Care to explain it? :P If this is referring to me, I think I did everything I could, I even apologized beforehand for the naiveness of this thread, I just happened to stumble upon some resources that talked about the similarity between big bang/black hole, and most importantly I couldn't figure out why big bang didn't form a black hole by definition. Your answer about entropy satisfied me.

No, not you. You're enjoyable to talk to, and you don't ask loaded questions as far as I can tell (you actually want an answer).

As an aside, I find these fora to be bizarre sometimes. Just yesterday there were bastions of science raining fire and brimstone down upon someone for demonstrating the work that they and their teacher performed. Not a single one of them came to discuss the advanced science in this thread. I surely would love to assume that it's because the majority of them are still stuck on trying to grasp the not-so-advanced algebra behind special relativity, but to make such an assumption without evidence would be... unscientific. :) /rant

Quote: Original post by mikeman
Also, could someone with some proper physics understanding, unlike me, explain in simple terms how the Universe is not a black hole? According to Big Bang, there was a tremendous amound of matter/energy in a single point, which does sound like a black hole. Furthermore, the timespace is expanding, as we know, faster than the speed of light, so, like black holes, nothing(not even light) can escape or reach the boundaries of the universe(event horizon?). Can it be expanding because the Big Bang was not a momentary event, but it's part of a continous flow of matter between the 'parent' and out universe, which means that matter keeps coming to our universe, warping spacetime more and more, causing it to 'expand'?

Any opinions or links to material about this would be welcome :)

AFAIK,in accordance with "multiverse" theory our universe is a bubble with reduced number of dimentions in 11-D space with another energy than another 11-D space around."Our" vacuum has a very tiny,but not equal to zero negative energy and it causes anti-gravitation ,forcing our universe to spread with acceleration.Another words,we are always in the boundaries of "parent" universe.
There is a horrible theory that one day somewhere in the some point "our" vacuum will return to "normal" 11-D state,and it will be the BIG END.Speading with light speed "bubble in bubble" can reach us in any moment of time("If I'll fly to heavens let's someone take my wheel. It's very hard to drive home in 11-dimentional space"[smile])
Black holes itself doesn't exist ,only event horisons. In our "normal" time current (faraway from huge mass,event horisons etc) black holes -i.e. singularity points- will form in the infinite future.

Though I know about multiverse after reading a books,there are nice videos about subject -

">More about multiverse

[Edited by - Krokhin on February 14, 2010 12:34:42 PM]

Just for the record, the false vacuum argument does not require string theory, 11 dimensions, or a multiverse. It requires pretty much just the Higgs field, as far as I know, which springs from plain old quantum field theory in 4D.

As for the brane collision "Big Bang" theory about how our "bubble" is embedded in a higher dimensional arena, see http://discovermagazine.com/2004/feb/cover. Do note the lack of the word multiverse in the article.

As for black hole formation, it takes only elementary general relativity to show that it does not take an infinite amount of time for matter to fall to the centre. A year or two back a couple of people tried to show that matter instead gets stuck on its way to the event horizon, never passing it. That's a basic confusion about the time coordinate (see Kruskal-Szekeres coordinates versus the highly flawed Schwarzschild coordinates). How the paper ever got recognition was a great mystery to pretty much every physicist that I talked to about it.

[Edited by - taby on February 14, 2010 5:29:08 PM]

Quote: Original post by taby
Just for the record, the false vacuum argument does not require string theory, 11 dimensions, or a multiverse. It requires pretty much just the Higgs field, as far as I know, which springs from plain old quantum field theory in 4D.

Well,I meant exactly superstring theory, this kind of Big-End with increasing the number of dimensions seems me more funny:

Quote:
Not all models of the evolution of the universe include its death in the distant future. There is a scenario in which the final can occur even tomorrow. It was first proposed by Moscow physicists MB Voloshin, I.Yu. Kobzareva and L.B. Okun in 1975, but in their work contained errors. Five years later, Americans Sidney Coleman and Frank De Lucca clarified this scenario. At that time it was believed that the vacuum of our world, most likely, is true (see sidebar) and has zero energy. Coleman and De Lucca, in contrast, suggested that our vacuum is false, then there is an extremely long-lived (as the physicists say, metastable) excited state with positive energy. They showed that the mechanism of quantum tunneling makes possible the spontaneous conversion of false vacuum in the true in a tiny region of space. Born a bubble of true vacuum will expand, causing matter internally with entirely new physical properties and completely destroy our false-vacuum world. Where would such a bubble may arise, to us he gets the speed of light and, therefore, without any warning.

Replacement of this scenario occurs and the latest version of quantum gravity, based on the theory of superstrings. "This theory also suggests that the vacuum is metastable. He can tunnel into a state with zero energy density, but it may happen that this density is negative. In the first case, our world will acquire six more spatial dimensions, ie space-time will be the not four-and ten-. Of course, this would be a world with completely different physics, we can not survive there. The second option is worse. If the density of vacuum energy somewhere to fall below zero, the space will be absorbed by the public collapse of a bubble, expanding at light speed - explains Professor Andrei Linde of Stanford University. - Coleman and De Lucca allowed a final opportunity, but do not take it seriously. In late May, I and my colleagues have published estimates, which suggests that this option should not be discounted. However, it does not mean the end of the entire Multiverse, as it will appear new worlds born of cosmic inflation. So the universe as a whole is still immortal.

Quote:
As for black hole formation, it takes only elementary general relativity to show that it does not take an infinite amount of time for matter to fall to the centre. A year or two back a couple of people tried to show that matter instead gets stuck on its way to the event horizon, never passing it. That's a basic confusion about the time coordinate (see Kruskal-Szekeres coordinates versus the highly flawed Schwarzschild coordinates). How the paper ever got recognition was a great mystery to pretty much every physicist that I talked to about it.

May be,but in which time-coordinate system? As for me,I prefer my system,faraway from this outrage[smile]

[Edited by - Krokhin on February 15, 2010 4:42:17 AM]

AFAIK, there are black holes in our universe.

If our universe would be a giant black hole, what would such a black hole inside that black hole be?

Stuff to think and ponder about for nights of no sleep!

Quote: Original post by Lode
If our universe would be a giant black hole, what would such a black hole inside that black hole be?

Probably I can mistake,but a charged black hole may have two event horisons (temporal onion). After crossing of each horison time and space coordinates switch the roles,and so on.there are a lot of very interesting theories.
But in realty many things looks different-for example,the latest supernova in Magellan Cloud.Firstly, it was a blue (not red!!) supergiant star,secondly- now astronomers can see nothing on that place and discuss about: how much time the forming of event horison itself takes at all? (Here I can mistake again,cuz it's four years old data,and now may be something has apeared)

[Edited by - Krokhin on February 15, 2010 6:22:13 AM]