Starship Asterisk*

Hawking has said there is no event horizon .. so what else is there not?

http://www.nature.com/news/stephen-hawk ... es-1.14583

BDanielMayfield wrote:

warmingwarmingwarming wrote:

neufer wrote:I'm perfectly copacetic with warmings's visualization of matter "(black hole or star, it doesn't really matter)" consuming space (i.e., converging spacetime). If there had been a lot more matter then all of space would have been consumed (and time ended) in the The Big Crunch. However, the Big Bang, Inflation and Dark Energy have all been having a field-day generating new space (i.e., diverging spacetime) such that the nibbling of matter doesn't really matter all that much.

Thanks for the encouragement, Neufer .. can you tell me why a Black Hole is said to increase in mass when everything that enters it is said to go into a singularity .. which as I understand it at this point is a mathematical point only .. having no mass at all. Or is my current understanding completely wrong? (As it could easily be as my most recent reading easily points out that singularities are a very, very, very complex topic.

Art spun up an artfully obtuse "answer" which was true, but failed to directly address warming³'s question, so I'm not copacetic with just leaving this alone. A very important principle of nature is conservation of energy. Energy (matter is made of energy, E=mc²) that enters a black hole is not lost to the universe, it adds to the three (and only three) properties of a black hole that can potentially be observed from the outside; mass, electric charge, and spin, aka angular momentum. There is no reason to believe that a BH's singularly has "no mass at all". But, otoh we can't even say for sure that BHs really have singularlies at their cores.

Was that helpful?

Conservation of energy is another of those general guidelines which generally come to complicated ends.

And what and where and for how long is an isolated system?

"In physics, the law of conservation of energy states that the total energy of an isolated system remains constant."

warmingwarmingwarming wrote:

BDanielMayfield wrote:A very important principle of nature is conservation of energy. Energy (matter is made of energy, E=mc²) that enters a black hole is not lost to the universe, it adds to the three (and only three) properties of a black hole that can potentially be observed from the outside; mass, electric charge, and spin, aka angular momentum. There is no reason to believe that a BH's singularly has "no mass at all". But, otoh we can't even say for sure that BHs really have singularlies at their cores.

Was that helpful?

Conservation of energy is another of those general guidelines which generally come to complicated ends.

And what and where and for how long is an isolated system?

"In physics, the law of conservation of energy states that the total energy of an isolated system remains constant."

What and where: the spacetime region of a BH's environment. For how long? "To time indefinite, or forever." I'd say what falls into a black hole is pretty darn isolated, and for what amounts to a practical eternity. With all due respect to Hawking, has the radiation named for him been observed or at least been proven to exist? And even if it does exist (which seems likely) massive BH's will evaporate at such a minuscule rate that this effect can be largely ignored. Proof:

Wikipedia gives the equation for the evaporation time t_ev of an M₀ massed BH as:

t_ev = 5120piG²M₀³/hc⁴, where h is the Planck constant. It also said that a 1 solar massed BH would take 2.098 x 10⁶⁷ years to evaporate. (Compare that to the estimated age of the universe at 1.38 x 10¹⁰ years.) Also, note that a BH's t_ev is proportional to the cube of its mass, so for instance a 5 solar massed BH would take 125 times longer to evaporate, or 2.62 x 10⁶⁹ years. Try to imagine how long it would take a SMBH to evaporate! The cube of 4.3 million is ... ouch. it is 7.95x10¹⁹, so the t_ev for the Milky Way's central SMBH would be 1.67x10⁸⁷, (if it never accretes anything during that staggeringly long duration, an impossible assumption.)

Also, all of these BH evaporation times assume that nothing new is ever added to the hole, but as we all know they like to accrete things. Conclusion, black holes last forever, in all practical terms.

Bruce

BDanielMayfield wrote:
Conclusion, black holes last forever, in all practical terms.

Nearly forever for observers on the outside.

But... those observers on the outside should also note that time nearly stops for objects falling into the event horizon.

So... do those observers who fall into the BH get to observe the black hole evaporate (as a blinding firewall)

Thats a rewriting. The one before wasnt post. Dunno why.

i finaly got the universe sandbox. i try the simulation with the black hole. So, i tought i put it in a north-sought trajectory to the sun. But no it was coming in the plane of the solar system. What a mess it make. i need to figure out how to use it. Sometime the program crash. But when it do a simulation, its great to see. Now, how to put it 90 degres above the sun and start it. i have a lot to learn and i am not in a hurry to do so. Wish me luck with this.

BDanielMayfield wrote:Conclusion, black holes last forever, in all practical terms.

No. The timeline of the Universe extends infinitely far into the future. It's more accurate to say that the lifetime of the largest black hole is just a quick flash in the infinitesimally brief young universe where there is actual structure present above the subatomic level.

If you want to argue "practical", you might also say that the Sun lasts forever, as well.

neufer wrote:

BDanielMayfield wrote:
Conclusion, black holes last forever, in all practical terms.

Nearly forever for observers on the outside.

But... those observers on the outside should also note that time nearly stops for objects falling into the event horizon.

So... do those observers who fall into the BH get to observe the black hole evaporate (as a blinding firewall)

Nope. Final answer.

Chris Peterson wrote:

BDanielMayfield wrote:Conclusion, black holes last forever, in all practical terms.

No. The timeline of the Universe extends infinitely far into the future. It's more accurate to say that the lifetime of the largest black hole is just a quick flash in the infinitesimally brief young universe where there is actual structure present above the subatomic level.

If you want to argue "practical", you might also say that the Sun lasts forever, as well.

So Hawking radiation (HR) is an established fact?

Assuming HR is real, the t_ev clock gets reset every time more energy or matter falls into the BH. If the overall rate of accretion is greater than the evaporation rate complete evaporation can be put off indefinitely.

I don't want to argue "practical" since it is such a subjective word, that wouldn't be very practical. However, I would agree that our universe is infinitesimally young compared to how old it will become in the course of infinite time to come. Therefore, considering something as brief as the MS lifetime of the Sun or the current age of the universe as "forever" wouldn't be very practical either.

Bruce

BDanielMayfield wrote:
Assuming HR is real, the t_ev clock gets reset every time more energy or matter falls into the BH. If the overall rate of accretion is greater than the evaporation rate complete evaporation can be put off indefinitely.

Even if each of the largest (10¹⁵ solar mass) galactic clusters were to end up as a 10¹⁵ solar mass BH
the Universe would still only live for ~2 x 10¹¹² years.

(I suspect that much of the galactic cluster mass would end up as gravity waves first, however.)

Chris Peterson wrote:

BDanielMayfield wrote:Conclusion, black holes last forever, in all practical terms.

No. The timeline of the Universe extends infinitely far into the future. It's more accurate to say that the lifetime of the largest black hole is just a quick flash in the infinitesimally brief young universe where there is actual structure present above the subatomic level.

If you want to argue "practical", you might also say that the Sun lasts forever, as well.

If we agree that the universe had a beginning .. Big Bang or whatever else we may conceive of .. then most views are that it will have an end .. yes, the timeline is already long, and may continue to be long, but compared to infinity (eternity actually though why debate the difference in meaning for this purpose) any amount of time is a flash in the pan.

warmingwarmingwarming wrote:

Chris Peterson wrote:

BDanielMayfield wrote:Conclusion, black holes last forever, in all practical terms.

No. The timeline of the Universe extends infinitely far into the future. It's more accurate to say that the lifetime of the largest black hole is just a quick flash in the infinitesimally brief young universe where there is actual structure present above the subatomic level.

If you want to argue "practical", you might also say that the Sun lasts forever, as well.

If we agree that the universe had a beginning .. Big Bang or whatever else we may conceive of .. then most views are that it will have an end ..

Why does a beginning imply an end? In fact, the majority of cosmologists believe that the Universe will continue expanding forever, approaching a limit of either absolute zero or an infinite energy density, depending on the nature of dark energy.

neufer wrote:

BDanielMayfield wrote:
Assuming HR is real, the t_ev clock gets reset every time more energy or matter falls into the BH. If the overall rate of accretion is greater than the evaporation rate complete evaporation can be put off indefinitely.

Even if each of the largest (10¹⁵ solar mass) galactic clusters were to end up as a 10¹⁵ solar mass BH
the Universe would still only live for ~2 x 10¹¹² years.

(I suspect that much of the galactic cluster mass would end up as gravity waves first, however.)

Where did you get the ~2 x 10¹¹² years lifetime for the universe from, Art?

Ann

Ann wrote:
Where did you get the ~2 x 10¹¹² years lifetime for the universe from, Art?

A one solar mass BH has a life time of ~2 x 10⁶⁷ years.

A 10¹⁵ solar mass BH has a life time {10¹⁵}³ longer.

neufer wrote:

Ann wrote:
Where did you get the ~2 x 10¹¹² years lifetime for the universe from, Art?

A one solar mass BH has a life time of ~2 x 10⁶⁷ years.

A 10¹⁵ solar mass BH has a life time {10¹⁵}³ longer.

Ah! Thanks!

Ann

Chris Peterson wrote:

warmingwarmingwarming wrote:

Chris Peterson wrote: No. The timeline of the Universe extends infinitely far into the future. It's more accurate to say that the lifetime of the largest black hole is just a quick flash in the infinitesimally brief young universe where there is actual structure present above the subatomic level.

If you want to argue "practical", you might also say that the Sun lasts forever, as well.

If we agree that the universe had a beginning .. Big Bang or whatever else we may conceive of .. then most views are that it will have an end ..

Why does a beginning imply an end? In fact, the majority of cosmologists believe that the Universe will continue expanding forever, approaching a limit of either absolute zero or an infinite energy density, depending on the nature of dark energy.

You're speaking for 'the majority' who are not here to confirm what you say .. but the latest news is that the increasing expansion rate means the universe is to end with a bang .. or big rip as it's commonly called.
However .. not all cosmologists believe that, of course. http://www.wired.co.uk/article/how-will-universe-end

But the big rippers carry a lot of weight. http://www.telegraph.co.uk/news/science ... claim.html

neufer wrote:

Ann wrote:
Where did you get the ~2 x 10¹¹² years lifetime for the universe from, Art?

A one solar mass BH has a life time of ~2 x 10⁶⁷ years.

A 10¹⁵ solar mass BH has a life time {10¹⁵}³ longer.

Still, a twinkling of an eye compared to eternity.

warmingwarmingwarming wrote:

neufer wrote:
Even if each of the largest (10¹⁵ solar mass) galactic clusters were to end up as a 10¹⁵ solar mass BH the Universe would still only live for ~2 x 10¹¹² years.

[A one solar mass BH has a life time of ~2 x 10⁶⁷ years.
A 10¹⁵ solar mass BH has a life time {10¹⁵}³ longer.]

(I suspect that much of the galactic cluster mass would end up as gravity waves first, however.)

Still, a twinkling of an eye compared to eternity.

I have been waiting ~2 x 10¹¹² years to hear those words from you, "warming."

Arthur .. do you really mean that?

warmingwarmingwarming wrote:
Arthur .. do you really mean that?

Do you have a towel

neufer wrote:

warmingwarmingwarming wrote:
Arthur .. do you really mean that?

Do you have a towel

Amen to your need and joy to you .. and almost now I need one, here in Hawaii, having first read a book on Hula, which I first witnessed in its sacred form 10 years ago, then following that book another on `Iolani Luahine, one of the women who recovered Hula from the sacrilege of its vaudeville era .. but a tissue had to suffice.

May the secrets of the ke ao holoʻokoʻa (universe) be received with kindness by our minds and spirits.

neufer wrote:
Do you have a towel

Douglas Adams wrote:
Any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still know where his towel is, is clearly a man to be reckoned with.

warmingwarmingwarming wrote:

Chris Peterson wrote:

warmingwarmingwarming wrote: If we agree that the universe had a beginning .. Big Bang or whatever else we may conceive of .. then most views are that it will have an end ..

Why does a beginning imply an end? In fact, the majority of cosmologists believe that the Universe will continue expanding forever, approaching a limit of either absolute zero or an infinite energy density, depending on the nature of dark energy.

You're speaking for 'the majority' who are not here to confirm what you say .. but the latest news is that the increasing expansion rate means the universe is to end with a bang .. or big rip as it's commonly called.

I'm merely pointing out the consensus position... somewhat more significant that a simple majority.

Whether the Universe ultimately cools down or achieves an infinite energy density remains uncertain, as we still don't have a good understanding of dark energy. However, it doesn't matter for my purpose here, because in either case the Universe extends infinitely far into the future. The Big Rip does not produce an "end" to the Universe in a finite time.

Didnt know a naked singularity could exist.

https://www.sciencedaily.com/releases/2 ... 113758.htm

``Scientists have found new ways to detect a bare or naked singularity, the most extreme object in the universe. This finding has possible astrophysical implications.

When the fuel of a very massive star is spent, it collapses due to its own gravitational pull and eventually becomes a very small region of arbitrarily high matter density, that is a`Singularity', where the usual laws of physics may breakdown. If this singularity is hidden within an event horizon, which is an invisible closed surface from which nothing, not even light, can escape, then we call this object a black hole. In such a case, we cannot see the singularity and we do not need to bother about its effects. But what if the event horizon does not form? In fact, Einstein's theory of general relativity does predict such a possibility when massive stars collapse at the end of their life-cycles. In this case, we are left with the tantalizing option of observing a naked singularity.``

Doum wrote:Didnt know a naked singularity could exist.

We don't know if they can. We don't even know if singularities exist inside the event horizon of a black hole.

The article is better summarized by noting that an observational method has been identified (on theoretical grounds) that provides an opportunity to test for the existence (but not non-existence) of hypothesized naked singularities.

Chris Peterson wrote:

warmingwarmingwarming wrote:

Chris Peterson wrote: Why does a beginning imply an end? In fact, the majority of cosmologists believe that the Universe will continue expanding forever, approaching a limit of either absolute zero or an infinite energy density, depending on the nature of dark energy.

You're speaking for 'the majority' who are not here to confirm what you say .. but the latest news is that the increasing expansion rate means the universe is to end with a bang .. or big rip as it's commonly called.

I'm merely pointing out the consensus position... somewhat more significant that a simple majority.

Whether the Universe ultimately cools down or achieves an infinite energy density remains uncertain, as we still don't have a good understanding of dark energy. However, it doesn't matter for my purpose here, because in either case the Universe extends infinitely far into the future. The Big Rip does not produce an "end" to the Universe in a finite time.

Where do you reference that what you say is the consensus position?

The Big Rip, if it happens, produces an end to the universe, period, whether you call that a finite time or not, because matter is pulled apart to the utmost position where no matter is left to exists.