May 10th, 2011, 03:09 AM
so i love the subject of black holes therefore iv researched them alot. im confident i know damn near all there is to know about them that they have figured out as of yet.
this is where i figure ill test the smarty pants's out there and hopefully som1 will post something i dont know about black holes?
May 10th, 2011, 03:18 AM
I have a question. How is it, that your written English skills appear to have gone down a black hole without you?Originally Posted by somfooleishfool
May 10th, 2011, 03:30 AM
i have a learning dysability? nuff said rllyI have a question. How is it, that your written English skills appear to have gone down a black hole without you?
Well okay, here is an actual black hole question. If the Earth suddenly became a black hole, what would happen to the moon?
Ok, do black holes emit Hawking radiation? If so, how?
Lunar eclipses would not be possible anymore.
I suppose this is not the answer you were waiting for. A hint: What would be the value of the Schwarzschild radius?
Provide calculations to deduce the radius of the earths event horizon (and also state the proper name of this radius) if it collapsed to a black hole. The mass of the earth is approximately 9,5736*10^24 kg.
Drat :-D I din't see your post before I had submitted my own.Lunar eclipses would not be possible anymore.
I suppose this is not the answer you were waiting for. A hint: What would be the value of the Schwarzschild radius?
According to my calculations the Schwarzschildradius should be 8,87 mm.Lunar eclipses would not be possible anymore.
I suppose this is not the answer you were waiting for. A hint: What would be the value of the Schwarzschild radius?
Did anyone know that, Schwarzschild is German for Blackshield?
I didn't think about it before, but now that you point it out, I can see it.
Yes, of course.Funny, isn't it?
And yes the value of about 9 mm is correct. How many Schwarzschild radii is the distance between the Black Hole Earth and the Moon? That number should tell you that the Moon most likely wouldn't even notice much of a difference.
The quotient of, half the distance of the semi major axis of the lunar orbit in mm, and nine, would tell how many Schwarzschild radii lie between the black hole Earth and the moon.
Considering,, there should be little to no effect on the moon.
Using a rough approximation of the moon's averahe distance to the earth (380,000 km) I arrive at approximately 43*10^9 Schwarzschildradii. Quite sufficient :-DYes, of course.
And yes the value of about 9 mm is correct. How many Schwarzschild radii is the distance between the Black Hole Earth and the Moon? That number should tell you that the Moon most likely wouldn't even notice much of a difference.
So, within how many Schwarzschild radii is there a noticeable difference in curvature?
In America, million is 10^6. I got 43*10^9, which in America is billion.
Of spacetime?
My bad. Thanks for pointing it out :-DIn America, million is 10^6. I got 43*10^9, which in America is billion.
Of spacetime?
Anyone who knows "all that is known" about black holes, knows that he doesn't know a heck of a lot. If on the other hand, he doesn't realise his ignorance like Hawking, Thorne, Penrose et al., then he doesn't know squat.
We are only just scratching the surface of the subject. Our two best theories, GR and QM, are both at the boundaries of their validity when dealing with black holes.
Some of your criticism is valid, but the discussion in this thread up to now is well supported by empirical data. The problematic realm is the space inside the Schwarzschild radius close to the central object.
Tell me the name of the famous Mathematical Physicist that came up with the theory of "singularity" thus inspiring Stephen Hawking in the earlier days? when did he come up with the theory? no cheating now
Hmmmm..... We seem to be missing comentary from somfooleishfool (the OP).
Perhaps he can pose a question or a problem related to black holes that will stump the rest of us.
...or maybe not.
Chris
Yes, as gravity is the curvature of spacetime.In America, million is 10^6. I got 43*10^9, which in America is billion.
Of spacetime?
Let me put it another way. If the Earth were to become a black hole, how close to it would you have to be orbiting to notice any difference, gravitationally, between what was the Earth and what is now the black hole?
We have established that the moon would not be affected, so what about a GPS satellite? Or the ISS?
For instance, the ISS orbit deteriorates due to atmospheric friction, but if that atmosphere was not there after the Earth had collapsed into a black hole, would the ISS orbit around the black hole actually be more stable than it's current orbit around the Earth?
The mean radius of the earth is 6,371 km, the Swarzschild radius of our black hole Earth is 8.87 mm. At a distance of 6,371 km from the black hole a person or object would still be subject to only one G of force toward the black hole.
A person standing on the moon might see Einstein rings formed of debris orbiting our black hole Earth.
I really have no idea how close a person would have to be to the surface of a marble sized black hole to become spaghettified.
Sngularity theorems in general relativity are in large part due to Roger Penrose for black holes, Stephen Hawking for the big bang, or a collaboration between Hawking and Penrose.
Links to some of their papers can b found here
http://www.thescienceforum.com/The-b...ogy-28430t.php
The reason I asked that earlier question is due to a post by Dishmaster.
So, I asked how small the number would have to be before you would notice a difference.
How close, in terms of Schwarzschild radii, does an orbiting object have to be to a planet, before it is so close that its orbit would be different if the planet were a black hole instead?
The Schwarzschild radius of any planet, or star, is by definition deep inside that object (otherwise it would be a black hole) and the radius at which any orbiting object would notice the difference, gravitationally, is also deep inside that object. Generally, if you can remain in orbit around an object now, you would be able to remain in the same orbit around that object if it were a black hole instead.
This all precludes any local side-effects of the gravitational collapse itself - I am talking about a simple before/after scenario here, or more accurately an either/or.
GiantEvil's question was,
Well, of course, the Earth cannot gravitationally collapse into a black hole, so for the Earth to suddenly become a black hole, some sort of magic must be involved - so I am assuming an instantaneous transition between the two states!
In which case, there is no orbiting object, orbiting any kind of planet or star (except perhaps something in close orbit around an exceptional object like a neutron star, where the tides are tremendous), that would notice the difference, gravitationally, if the thing it were orbiting were a black hole instead! The whole question is a red herring! An object would already have to be heading on a collision course with the Earth for it to be affected in any way if the Earth were a black hole instead.
:wink:
Realistically, for the Earth to collapse to a size < the Schwarzschild radius of it's mass, would require an external cause which most likely the moon would not survive.
I already knew that under the mind experiment condition of the Earth magically becoming a black hole, the moons orbit would be unaffected.
I originally posted the question for the OP of this thread who had come on like a braggart concerning their knowledge of black holes, but the OP hadn't responded, and a discussion had ensued.
This discussion has brought another question to mind.
When a person is standing on the surface of the Earth, the solid mass below them exerts a gravitational effect. How significant is the gravitational effect of the mass of the atmosphere above them?
It isn't significant at all.
Or perhaps I should say it is as significant as the gravitational effect of the mass of the rest of the atmosphere, which cancels it out exactly. It is equivalent to the scenario anywhere inside a hollow sphere, where there is no net gravitational effect from the material that makes up the shell of the sphere.
I was asking the author of the thread when he said he knows all relative info on black holes........you blew my coverSngularity theorems in general relativity are in large part due to Roger Penrose for black holes, Stephen Hawking for the big bang, or a collaboration between Hawking and Penrose.
Links to some of their papers can b found here
http://www.thescienceforum.com/The-b...ogy-28430t.php:-D
I guess the fact the OP has gone into hiding (hit and run troll?) indicates he figured he was in waaaaaaaay over his head with this crowd. Not gonna be able bluff your way through here with a "knowing everything" bluster
I got ya. I figured it like this.It isn't significant at all.
Or perhaps I should say it is as significant as the gravitational effect of the mass of the rest of the atmosphere, which cancels it out exactly. It is equivalent to the scenario anywhere inside a hollow sphere, where there is no net gravitational effect from the material that makes up the shell of the sphere.
First I drew a circle, then I picked an arbitrary point(PA) inside the circle but not at the center.
I bisected the circle with a line(LA) that passed through the center of the circle and (PA). The points where (LA) crossed the circles circumference I labeled (PB) and (PC).
I drew another line(LB) perpendicular to (LA) at (PA). The points where (LB) crosses the circles circumference I labeled (PD) and (PE).
The ratio of the distances of (LA) between (PA)(PB)/(PA)(PC) is equal to the ratios of the circles circumference between (PD)(PE)/(PE)(PD) measuring clockwise.
For clarity assume the whole construct to be rotated such that (LA) is vertical with (PA) up.
(PB) will be "up" and (PC) will be "down".
(PD) is "left" and (PE) is "right".
I really think someone need's to write a version of "Element's" that includes nudity and explosions.
This justifies my reasons for lurking in and out of the forum.... to watch every one show off their brain wavesI guess the fact the OP has gone into hiding (hit and run troll?) indicates he figured he was in waaaaaaaay over his head with this crowd. Not gonna be able bluff your way through here with a "knowing everything" bluster
Correct me if I'm wrong, but I thought the original theory of black hole formation is attributed to Oppenheimer who built on Chandrasekar's work with degeneracy of white dwarfs and neutron stars. It was followed by Wheeler in the US and either Landau or Zel'dovich in the USSR ( I don't recall which at the moment ). Only then did Penrose, Hawking and Thorne get involved.
Apparently goes even farther back in history; http://en.wikipedia.org/wiki/John_Michell and; http://en.wikipedia.org/wiki/Pierre-Simon_Laplace.
Long ago black holes were known as "dark stars".
http://en.wikipedia.org/wiki/Dark_st...ian_mechanics)
This is a particularly good reference paper, in my opinion:
http://arxiv.org/abs/astro-ph/9801252
Black Holes : A General Introduction - Jean-Pierre Luminet
Schwarzschild and Einstein had a hand in it, and Volkoff, Finkelstein, Kerr, and doubtless others too.
I think the important thing that people miss with all this is that Oppenheimer and Volkoff called them "frozen stars" for a reason. The paper Speedfreak linked to touched on this, but doesn't get there. It says "A striking consequence is that any outer astronomer will never be able to see the formation of a black hole" when it ought to say the formation of the central singularity. A star collapses while you watch, and the result is this small black thing. Light can't get out of it, or anything else. So it's a black hole regardless of what you consider to be going on inside. Only "inside" is a bit of issue in itself. For example, take a look at the gravastar which is described as "an alternative to black hole theory". It's akin to a frozen star. Note the bit that says This region is called a "gravitational vacuum", because it is a void in the fabric of space and time. The gravastar is something like a frozen star, and it features a hole in spacetime. No light gets out, it's black, and thus it's arguably more of a black hole than the traditional picture of what a black hole is.
It goes back farther than that -- to John Michell and Pierre-Simon Laplacce.
http://en.wikipedia.org/wiki/Black_hole
But the rigorous theory of actual singularities is due to Penrose and Hawking.
Note that the "singularity" at the Schwarzchild radius is not really a singularity but rather an artifact of a coordinate choice.
JEEZUS christ! im pretty sure its only been a day since i last looked on here an i only had 1 reply... i wasnt avoiding the post i just wasnt aware that i had a million replys haha.
quite frankly im DELIGHTED to discover from this topic that i know SWEET FUCK ALL about black holes. what fun would science be if u knew everything. and some ppl who wer saying i came off as a know it all or what have you, you missed my intention. i wouldv done better to phrase it more like "iv run out of direction to look for new info on black holes. iv run all the way down the rabbit hole nd found the end nd i need to find a new rabbit hole on black holes if you will
ftr i couldv already told you that the moon would have not been affected as the gravitational pull of a black hole is no stronger that the gravitational pull of the mass it was created by (plus mass of everything ever sucked in). the only reason you would think black holes have more gravity is that you can get closer to the mass. eg if you can survive just fine on the surface of the earth and the gravity is fine because u cant get any closer to the earth than that surface of the earth (debateable i guess) but if you were to find yourself in the center of the earth, you would find the gravity to be identical to the gravity you would experiance if earth were to be a black hole (or so i beleve.... might be incorrect here). at any rate it would be a similar amount of gravity i immagine.
i wont lie. that "schwazerblahblah" is a new word to me, it means the EXACT same thing as "event horizon"?
it was interesting to hear from som1 that all bodys have a "swazerblahblah" (i rlly cant remember what that word was without reading back to the post) but that it is not defined as a black hole till the "swazerblahblah" has a bigger diameter than the surface of the body.
a question for the next smart person capable of answering this. what would be the closest escape velocity to c possible, without having escape velocity c iteslf, (black hole) and what would be an example of this? eg a pulzar or something, and for that matter, any1 know the rough escape velocity of a typical pulzar?
and here something for ppl to speculate on. i remember reading somwhere, cant remember wherre. that the proposed density of the matter in a black hole contradicts the calculated *force* (cant remember what force it was, either strong force or electromagnetic force) that would be pushing the atoms apart. in other words. the atoms would be pushing apart harder than they would be pressing together or something to that affect is what i took from it.
a FURTHER thing. iv loved science since i was a wee tyke and my passion has never wained. im looking at going to university and doing a certificate in science, but iv always struggled with education, you can probably tell that just from my grammar and over all post structure. iv failed pretty much every educational endevour iv ever attempted but i hold hope that science may be different because i dont think there is a thing on this planet that fascinates me more than science (well... most sciences... some sciences can go blow a donkey :]).
having said all this my request is this, would som1 be able to post me a link or evn tell me themselves what the sort of work would be like? i just want to see if the work that i could expect to see in class would go way over my head or not. i would be doing microbiology most likely coz i place it as easier than physics. but physics is my favorate subject namely particle physics.... but i immagine particle physics will be neigh impossible for me sadly
end of post. srry for the massive post
Pursuing a course of study in physics will require that you first learn how to read, comprehend and communicate in English (or your native language - whatever that might be). This will necessarily involve big words like "Schwarzschild radius"....having said all this my request is this, would som1 be able to post me a link or evn tell me themselves what the sort of work would be like? i just want to see if the work that i could expect to see in class would go way over my head or not. i would be doing microbiology most likely coz i place it as easier than physics. but physics is my favorate subject namely particle physics.... but i immagine particle physics will be neigh impossible for me sadly
end of post. srry for the massive post
It will also require you to learn complicated mathematics and to learn how to express physical concepts in terms of mathematical equations.
Your posts so far demonstrate that you have a very long way to go and a lot of hard work ahead of you if you want to study physics seriously.
If the learning disability you mentioned in your second post is the reason for your poor (and inappropriate) communication skills then you will first have to overcome this deficit. If you're unable to do so then my advice to you would be that you continue to read about physics (and science, in general) as a hobby.
I would also strongly suggest that you refrain from presenting yourself as having expert scientific knowledge in posts to any science forums. You clearly don't have any such knowledge and you will quickly be exposed as a fraud.
Chris
From what you have displayed in this thread, any university work, even from an online diploma mill, will be WAY over your head.having said all this my request is this, would som1 be able to post me a link or evn tell me themselves what the sort of work would be like? i just want to see if the work that i could expect to see in class would go way over my head or not. i would be doing microbiology most likely coz i place it as easier than physics. but physics is my favorate subject namely particle physics.... but i immagine particle physics will be neigh impossible for me sadly
end of post. srry for the massive post
You might look into something compatible with your location and capabilities. New Zealand needs shepherds.
From what you have displayed in this thread, any university work, even from an online diploma mill, will be WAY over your head.
You might look into something compatible with your location and capabilities. New Zealand needs shepherds.
i didnt ask ur opinion on whether i was capable of it. i asked what the work was like.
english can be learned. my english is rubbish not SO much in regard to my disability but more perhaps because of my lack of education. i left school early.
Just to add...
You were right to say you might be incorrect here!
Not quite exactly the same thing. An event horizon forms at the Schwarzschild radius once a massive body has collapsed within it. The Earth has a Scharzschild radius, but it does not have an event horizon.
It might be better to say a black hole doesn't form until the body gravitationally collapses such that it has a smaller radius than its Schwarzschild radius, rather than the other way round.
also i read back over what i have written and i can see where you are coming from. i was a bit inapropriate and i apolagise. i had just assumed i was talking to people of my age group and i have only just concidered that thier wil be people on here expecting i higher standard of conversation.
ill end on this note. im pretty sure i remember hearing somewhere that albert einstein had learning difficulties. at a guess i would say maybe asbergers syndrome. who says its a disability in all aspects of life
apprieciatedJust to add...
You were right to say you might be incorrect here!
Not quite exactly the same thing. An event horizon forms at the Schwarzschild radius once a massive body has collapsed within it. The Earth has a Scharzschild radius, but it does not have an event horizon.
It might be better to say a black hole doesn't form until the body gravitationally collapses such that it has a smaller radius than its Schwarzschild radius, rather than the other way round.
Einstein had no learning disabilities, he was just rebellious and anti-authoritarian. Which, in the time and place where he attended school, was no way to endear oneself to the dozent's.
Here is a black hole question:
Do some or all black holes collapse in on themselves and die?
If yes, is it possible that as they collapse in on themselves and appear to die, they are kind of squeezed out of this universe and explode into a new one? Is it possible that the death of a black hole in one universe is actually the birth of a new universe?
I hope I've made my question clear but if not, I'll try explain more clearly.
Rich.
No, they actually collapse in on themselves and persist.
So they never ever disappear / die?No, they actually collapse in on themselves and persist.
Possibly, but not commonly.
http://en.wikipedia.org/wiki/Hawking_radiation
Hawking radiation is a process whereby a black hole might be dissipated, but the process might require a time longer than the predicted life for the universe.
I'm not sure that there is a "predicted life for the universe". If I understand the current interpretation of accelerated cosmic expansion, the universe may just continue to expand forever. Even for the largest black holes, "forever" is a long enough time for them to dissipate by the emission of Hawking radiation.
Chris
But, if the "big Bounce" theory is correct then I guess GiantEvil could be right, too.I'm not sure that there is a "predicted life for the universe". If I understand the current interpretation of accelerated cosmic expansion, the universe may just continue to expand forever. Even for the largest black holes, "forever" is a long enough time for them to dissipate by the emission of Hawking radiation.
Chris
Makes me wonder what the point in wondering is!
I was thinking heat death of the universe, and the point where life as we know it could no longer exist. According to this wiki article the final heat death of the universe would coincide with the evaporation of the last black hole.I'm not sure that there is a "predicted life for the universe". If I understand the current interpretation of accelerated cosmic expansion, the universe may just continue to expand forever. Even for the largest black holes, "forever" is a long enough time for them to dissipate by the emission of Hawking radiation.
Chris
Personally, I don't like the heat death idea, I find it slightly depressing.
http://en.wikipedia.org/wiki/Heat_death_of_the_universe
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