| |
 |
|
|
Science Forum Index » Astronomy Forum » Black Holes in Early Universe
Page 2 of 3 Goto page Previous 1, 2, 3 Next
|
| Author |
Message |
| Bill Sheppard |
 Posted: Sat Dec 20, 2003 5:28 am |
|
|
|
Guest
|
Quote: You have this fixed idea that black holes
are rotating very fast, but you don't give
any reasons for that belief.
The earlier poster didn't specifically state it, but conserved angular
momentum would spin up the BH. Angular momentum of the pre-collapse
body, now vectored onto the collapsed radius, would impose a very high
spin rate. oc |
|
|
| Back to top |
|
| Bill Sheppard |
| Posted: Sat Dec 20, 2003 5:49 am |
|
|
|
Guest
|
Quote: This vibratory motion is also what
causes particles to have a tough time
remaining in orbit; they either spin loose
or spin in.
Got a question.. When infalling matter from the accretion disc "spins
in", by what route does it enter the BH? Does it fall *onto* the highly
oblate, centrifugally repellant equator, or does it separate into two
flows, entering by the route of least resistance, i.e., the poles?
The reason for this question is- BH accretion dynamics have heretofore
been modeled on 'normal' stellar bodies, where the infall from the
accretion disc falls largely onto the equatorial zones.
But this model applied to BHs does not consider the BH's
extremely high spin rate. High spin-rate would dictate the poles as the
natural route of least resistance *into* the BH and the equator as the
route of most resistance. Comments... ? oc |
|
|
| Back to top |
|
| Bill Sheppard |
| Posted: Sat Dec 20, 2003 6:49 am |
|
|
|
Guest
|
Matthew M. wrote,
Quote: If an event horizon 'vibrates' like a string, >due to the exceptional
speed of rotation,
then it will make it even harder for
particles to remain in orbit around the
black hole...
On a related note, the spin rate of millisecond pulsars is limited by
just such a mechanism; where a neutron star is 'feedng' off a nearby
companion body, its spin-rate keeps rising. Eventually the spin sets up
a convulsive oscillation which is radiated off equatorially as gravity
waves. Around 700 revs per second is the upper limit. Except for this
self-limiting mechanism, the spin-rate would continue rising until the
star explodes.
In your post, you have extrapolated this model to BHs in
the early universe; BHs voraciously devouring matter would acquire
spin-rates orders of magnitude higher yet. And their highly oblate,
convulsively oscillating equators would radiate GW energy prodigiously,
as long as the 'fuel' supply remained adequate (does anybody see a
connection to the quasars here?). The early universe musta been a
churning caldron of GW energy to boot. Then, as the 'fuel' supply
dwindled, those BH 'engines' would gradually spin down, becoming the
cores of sedate galaxies of the present epoch.
Might this be a possible scenario? oc |
|
|
| Back to top |
|
| Matthew Montchalin |
| Posted: Sat Dec 20, 2003 7:00 am |
|
|
|
Guest
|
||I don't know why they should not be capable of such rotational speeds?
|
|If the rotational period is close to the speed of light, and the speed
|of light happens to be the escape velocity for anything captured by
|the black hole, then the shape of the event horizon will be elongated
|along the equator, as opposed to the poles. The greater the rotational
|period, the greater the elongation. This is reflected in the accretion
|disk that you find surrounding a black hole.
In the early universe, wouldn't it be correct to suppose that most
black holes would be highly elongated along their equators as opposed
to later on, in a universe that is cooling off, they are less elongated?
And in a very early universe, it is reasonable to suppose that black
holes were not only highly elongated, 'pancake' shaped bodies, but
they collided with each other. Certainly during the time of the great
decoupling, don't you think?
Black holes are strange creatures. They have event horizons beyond
which particles should not be able to escape because their escape
velocity would have to exceed the speed of light. The surfaces
of these 'event horizons' are likely to be highly deformed, and
vibrate at speeds very close to the speed of light. This vibratory
motion is also what causes particles to have a tough time remaining
in orbit; they either spin loose or spin in. |
|
|
| Back to top |
|
| Bill Sheppard |
| Posted: Sat Dec 20, 2003 8:29 am |
|
|
|
Guest
|
Quote: By what mechanism do you propose that >the accreting material obtains a
component of velocity directed towards
the poles???
Again, the analogy of a centrifugal pump. It naturally intakes by way of
the hub, not the rim of the spinning impeller wheel. This is an
_analogy_, remember, not meant to imply a BH *is* a pump.
Picture the BH in side-on view, in extreme close-up. The
infall from the accretion disc must follow the route of least resistance
_into_ (not 'onto') the BH. This would force the infall to divide into
two flows, riding 'up and over' the final hump, then plunging down the
twin 'bathtub drain' vortices head-on into the poles. The higher the
spin rate, the more acutely the infall must favor the poles.
Of course, if a non-rotating BH were to exist, it would
accrete in the same manner as any other object. But in the real
universe, all stars rotate, and when collapsed to a neutron star,
angular momentum imparts spin rates that can go to hundreds of revs per
second (as seen in millisecond pulsars). When collapsed to a BH,
spin-rates would go orders of magnitude higher yet.
The extreme spin-rates of BHs dictate their polar-accretion
dynamic.. AND the essential _gravitic bipolarity_ of all (spinning) BHs.
This bipolarity would be obvious only in extreme close-up; at distance
it drops below resolution and the BH becomes a monopolar point source.
oc |
|
|
| Back to top |
|
| Jonathan Silverlight |
| Posted: Sat Dec 20, 2003 9:06 am |
|
|
|
Guest
|
In message <Pine.LNX.4.44.0312190241090.25489-100000@lab.oregonvos.net>,
Matthew Montchalin <mmontcha@OregonVOS.net> writes
Quote: On Fri, 19 Dec 2003, variable magnitude wrote:
|> You don't think that black holes are capable of rotational periods close
|> to the speed of light?
|
|I don't know why they should not be capable of such rotational speeds?
If the rotational period is close to the speed of light, and the speed
of light happens to be the escape velocity for anything captured by
the black hole, then the shape of the event horizon will be elongated
along the equator, as opposed to the poles. The greater the rotational
period, the greater the elongation. This is reflected in the accretion
disk that you find surrounding a black hole.
You have this fixed idea that black holes are rotating very fast, but
you don't give any reasons for that belief.
--
Rabbit arithmetic - 1 plus 1 equals 10
Remove spam and invalid from address to reply. |
|
|
| Back to top |
|
| Painius |
| Posted: Sat Dec 20, 2003 9:37 am |
|
|
|
Guest
|
"Matthew Montchalin" <mmontcha@OregonVOS.net> wrote in message news:Pine.LNX.4.44.0312200354400.3782-100000@lab.oregonvos.net...
Quote:
In the early universe, wouldn't it be correct to suppose that most
black holes would be highly elongated along their equators as opposed
to later on, in a universe that is cooling off, they are less elongated?
And in a very early universe, it is reasonable to suppose that black
holes were not only highly elongated, 'pancake' shaped bodies, but
they collided with each other. Certainly during the time of the great
decoupling, don't you think?
Black holes are strange creatures. They have event horizons beyond
which particles should not be able to escape because their escape
velocity would have to exceed the speed of light. The surfaces
of these 'event horizons' are likely to be highly deformed, and
vibrate at speeds very close to the speed of light. This vibratory
motion is also what causes particles to have a tough time remaining
in orbit; they either spin loose or spin in.
And after several black holes collide and become one
giant black hole, perhaps the deformed and vibrating
event horizons lead to a gathering of gas and dust in
the form of a spiral? These nebulas give birth to stars
which become the visible spiral arms of galaxies?
happy days and...
starry starry nights!
--
Life without love is
A lamp without oil,
Love without prejudice,
A tool without toil--
World without soil.
Paine Ellsworth |
|
|
| Back to top |
|
| John Zinni |
| Posted: Sat Dec 20, 2003 11:34 am |
|
|
|
Guest
|
"Bill Sheppard" <oldcoot@webtv.net> wrote in message
news:29068-3FE46F7F-20@storefull-3172.bay.webtv.net...
Quote: This vibratory motion is also what
causes particles to have a tough time
remaining in orbit; they either spin loose
or spin in.
Got a question.. When infalling matter from the accretion disc "spins
in", by what route does it enter the BH? Does it fall *onto* the highly
oblate, centrifugally repellant equator, or does it separate into two
flows, entering by the route of least resistance, i.e., the poles?
The reason for this question is- BH accretion dynamics have heretofore
been modeled on 'normal' stellar bodies, where the infall from the
accretion disc falls largely onto the equatorial zones.
But this model applied to BHs does not consider the BH's
extremely high spin rate. High spin-rate would dictate the poles as the
natural route of least resistance *into* the BH and the equator as the
route of most resistance. Comments... ? oc
By what mechanism do you propose that the accreting material obtains a
component of velocity directed towards the poles??? |
|
|
| Back to top |
|
| G=EMC^2 Glazier |
| Posted: Sat Dec 20, 2003 12:01 pm |
|
|
|
Guest
|
Hi oc If the black hole is spinning close to "c" at its equator at the
exact center of its axis poles it has no motion. It would make it easier
for matter to fall into the poles. That is true here on Earth,but a
black hole the difference is billions of times greater. Bert PS On
Earth it is half of one percent greater at the poles than the equator |
|
|
| Back to top |
|
| Greg Neill |
| Posted: Sat Dec 20, 2003 12:15 pm |
|
|
|
Guest
|
"John Zinni" <j_zinni@NOCRAP.sympatico.ca> wrote in message
news:9T_Eb.25303$CK3.2735475@news20.bellglobal.com...
Quote: "Bill Sheppard" <oldcoot@webtv.net> wrote in message
news:29068-3FE46F7F-20@storefull-3172.bay.webtv.net...
This vibratory motion is also what
causes particles to have a tough time
remaining in orbit; they either spin loose
or spin in.
Got a question.. When infalling matter from the accretion disc "spins
in", by what route does it enter the BH? Does it fall *onto* the highly
oblate, centrifugally repellant equator, or does it separate into two
flows, entering by the route of least resistance, i.e., the poles?
The reason for this question is- BH accretion dynamics have heretofore
been modeled on 'normal' stellar bodies, where the infall from the
accretion disc falls largely onto the equatorial zones.
But this model applied to BHs does not consider the BH's
extremely high spin rate. High spin-rate would dictate the poles as the
natural route of least resistance *into* the BH and the equator as the
route of most resistance. Comments... ? oc
By what mechanism do you propose that the accreting material obtains a
component of velocity directed towards the poles???
Also, the event horizon "surface" of a black hole isn't a
surface at all. It represents a demarcation boundary where
the escape velocity is the speed of light. Infalling material
doesn't feel a centrifugal force due to the hole's spin,
although it will feel an effect due to the frame dragging that
occurs. |
|
|
| Back to top |
|
| Matthew Montchalin |
| Posted: Sat Dec 20, 2003 5:20 pm |
|
|
|
Guest
|
On Sat, 20 Dec 2003, Jonathan Silverlight wrote:
|>If the rotational period is close to the speed of light, and the speed
|>of light happens to be the escape velocity for anything captured by
|>the black hole, then the shape of the event horizon will be elongated
|>along the equator, as opposed to the poles. The greater the rotational
|>period, the greater the elongation. This is reflected in the accretion
|>disk that you find surrounding a black hole.
|
|You have this fixed idea that black holes are rotating very fast, but
|you don't give any reasons for that belief.
Isn't just about everything 'really' fast in the very early universe?
The mechanisms whereby black holes are created, is the same then and now,
but for the frequencies of their creation. In the early universe, they
'collided' a lot more often, in the later universe, they 'collide' a
lot less frequently. |
|
|
| Back to top |
|
| Matthew Montchalin |
| Posted: Sat Dec 20, 2003 5:22 pm |
|
|
|
Guest
|
On Sat, 20 Dec 2003, Bill Sheppard wrote:
|>You have this fixed idea that black holes
|>are rotating very fast, but you don't give
|>any reasons for that belief.
|
|The earlier poster didn't specifically state it, but conserved angular
|momentum would spin up the BH. Angular momentum of the pre-collapse
|body, now vectored onto the collapsed radius, would impose a very high
|spin rate. oc
If there is a limit to which a black hole can spin, it is the same limit
for which a black hole can move through space - the speed of light.
If there is a basis for arguing that angular momentum is not conserved,
what would it be? |
|
|
| Back to top |
|
| Matthew Montchalin |
| Posted: Sat Dec 20, 2003 5:26 pm |
|
|
|
Guest
|
On Sat, 20 Dec 2003, Bill Sheppard wrote:
|The reason for this question is- BH accretion dynamics have heretofore
|been modeled on 'normal' stellar bodies, where the infall from the
|accretion disc falls largely onto the equatorial zones.
| But this model applied to BHs does not consider the BH's
|extremely high spin rate. High spin-rate would dictate the poles as the
|natural route of least resistance *into* the BH and the equator as the
|route of most resistance. Comments... ? oc
For particles affected by gravity, they tend to be swept in along
the equator, don't they?
But for particles not affected by gravity, they ought to come in from
more or less anywhere, not being favored by the equator any more than
by the pole. |
|
|
| Back to top |
|
| Matthew Montchalin |
| Posted: Sat Dec 20, 2003 5:36 pm |
|
|
|
Guest
|
On Sat, 20 Dec 2003, Bill Sheppard wrote:
| In your post, you have extrapolated this model to BHs in
|the early universe; BHs voraciously devouring matter would acquire
|spin-rates orders of magnitude higher yet. And their highly oblate,
|convulsively oscillating equators would radiate GW energy prodigiously,
|as long as the 'fuel' supply remained adequate (does anybody see a
|connection to the quasars here?).
If we cannot tell the difference between time going forward, and time
going backward, an early universe populated with rapidly spinning
"pancake-shaped" black holes, are as likely to collide as split apart.
The mechanism for splitting apart probably depends as much on Hawking
radiation as vibratory 'stringing' of the event horizon, where particles
are as likely to fall in, as fall out.
|The early universe musta been a churning caldron of GW energy to boot.
Yes.
|Then, as the 'fuel' supply dwindled, those BH 'engines' would gradually
|spin down, becoming the cores of sedate galaxies of the present epoch.
| Might this be a possible scenario? oc
It's certainly a scenario that is highly seductive. But the decoupling
mechanism of the early universe is bound to have a great deal to do with
the frequency of black holes splitting apart in the later universe.
For instance, in a very cold universe with particles few and far between,
a rapidly rotating black hole is bound to have consumed its accretion
disk, or thrown off that which cannot be consumed. If there are any
particles around to fall in a black hole, they are as likely to come
from one direction as any other. I assume that a BH in a cold universe
can start out "pancake-shaped" for its high rotational velocity, but
its speed of rotation will tend to persist for want of tidal interactions
with other massive bodies. The mechanism to slow the BH down is infall
of cold particulate matter from all directions, not from an accretion
disk per se. The universal infall from all directions will probably
cause the BH to become less elongated and more spherical. |
|
|
| Back to top |
|
| Bill Sheppard |
| Posted: Sat Dec 20, 2003 5:54 pm |
|
|
|
Guest
|
Bert wrote, re. the polar accretion dynamic of BHs:
Quote: On Earth it is half of one percent greater
at the poles than the equator..... That is
true here on Earth, but a black hole the
difference is billions of times greater.....
It would make it easier for matter to fall
into the poles.
Yeah, Bert. Consider your frequent 'What if' scenario where the Earth is
shrunk to a BH the size of a pea (actually it would be closer to the
size of a grape if you figure out its Schwartzchild radius). Imagine the
1035-mph equatorial velocity being suddenly imparted to that grape's
circumferance. There'd be some losses in the transfer no doubt, but the
spin rate would be enormously high, on the order of half million RPM
(for a grape with a circumferance of 1¼ inch). Somebody doublecheck
the math!<g> oc |
|
|
| Back to top |
|
| |
Page 2 of 3 Goto page Previous 1, 2, 3 Next
All times are GMT - 5 Hours
The time now is Mon Dec 01, 2008 10:47 am
|
|