A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Research
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

A quasar, too heavy to be true



 
 
Thread Tools Display Modes
  #11  
Old December 21st 17, 11:09 PM posted to sci.astro.research
jacobnavia
external usenet poster
 
Posts: 105
Default A quasar, too heavy to be true

[[Mod. note -- I apologise for the delay in processing this article.
It arrived in my moderation queue on 2017-12-18, just before an
extended power/internet outage at my location.
-- jt]]

Le 17/12/2017 eM- 21:18, Phillip Helbig (undress to reply) a ecrit:
In article , jacob navia
writes:

1) At z = 1000 we have a temperature of 2,728 degrees... Completely new
and unknown processes must have been at work to form structures like a
black hole at those temperatures.


Perhaps different than for stellar-mass black holes, but not necessarily
completely new and unknown.


Not necessarily, those mysterious processes created "out of some random
fluctuation" made those seeds and that quasar comes into being just a
few hundred million years later.

OK.

Note that quasars come in huge galaxies. A survey based on on the SDSS,
was done by Matsuoka et al (https://arxiv.org/abs/1312.2417). He looked
at stripe 82 and all quasars inside it were in galaxies more than 10E10
sun masses.

[[Mod. note -- I think there's an observational selection effect he
The very first paragraph of that abstract refers to "optically luminous"
quasars. We believe that fainter quasars exist, but if (as we expect)
these are hosted in smaller/fainter galaxies, they will be hard(er) to
observe.
-- jt]]

All that in about 450 My.

And nothing less than a black hole of
1E4 solar masses. It seems (to me) impossible that gravity can condense
something at those temperatures.


Then read up on your physics.


Yes, let's do that.

Primordial black holes were a speculation within big bang theory that
was never observed. I would like to remember your own words in this
discussion group when discussing with Mr Oldershaw when you argued
against the black holes he proposed.

Observations rule out the existence of many small black holes because
they would bend light and that wasn't observed. That is what you said.

Now you propose that big black holes were created somehow from the
"start". They would become the nucleous of future galaxies.

Of course "some random fluctuation" could create anything, including a
very convenient "seed" to grow up a huge galaxy in no time.

I just find that unlikely.

2) At z = 40 we have a temperature of 112 K. Star formation happens in
clouds with temperatures between 10 to 20 K. Yes, 112 K is not "searing
hot", but hot enough to make star formation impossible.


Not all black holes must form from stars.


Yes, they could form by accretion. So just 40 million black holes of 20
solar masses each in average would create that monster one in around 500
My. And those weren't created out of stars any more, (there is no time
nor conditions to do that) but they just existed somehow. It makes one
of those (20 solar masses each!) accretting to the black hole each month
for 500 million years.

Black hole mergers release an incredibly amount of energy, so how
anything could survive in an environment where those events happen every
month is a mystery. A consequence of that is that there isn't any host
galaxy, blown away by those explosions each month...

[[Mod. note --
1. The standard scenario is that the first generation of stars to form
("population III" is the somewhat-confusing standard term) tended to
be fairly massive, so their lives were perhaps 1-3 million years
before producing supernovae and ~10 solar-mass black holes. These
are the "seeds black holes" under discussion (which could then grow
by accretion and/or mergers).
2. BH mergers do indeed release a lot of energy... but they release it
as gravitational waves, which propagate outwards and have only a minute
effect on the host galaxy.
-- jt]]

To me, all that sounds very unlikely.

3) If we assume that star formation could happen at 50 K, i.e. at z =
17, approx 228 My after the bang, that leaves 690 - 228 --462 My to
form a black hole that has an 800 Msun mass...


Not all black holes must form from stars.

I am not saying that BB theory is impossible. I am just saying that
explaining observations within that framework becomes more and more
difficult, requiring more and more "ad hoc" hypothesis (now we have
primordial black holes)


Primordial black holes are neither an ad-hoc hypothesis nor were they
thought of first to explain this observation. Do a literature search
for "primordial black holes".


Yes, it is instructive. A literature search confirms that quasars live
in big galaxies.

and requiring explanations that look less and
less probable.


By which measure?


Look at this discussion. You add hypothesis after hypothesis. These
black holes, the acceleration of black hole condensation, the
acceleration of galaxy formation...

And observations that contradict the bang start coming
almost daily now. ALMA has seen a galactic collision at 780 My and the
two galaxies are very dusty and huge... I will post another article
about that.


You have been claiming this for years, but have never come up with
anything which convincingly contradicts the big bang.


True, this was clear to me several years ago. And now those ideas are
being confirmed. The more time passes, the more unlikely the whole bb
theory becomes.

Now, if we follow bare observations. We have a galaxy, at least 1E10
solar masses and ours is 1E12 solar masses, a factor of 100. Our galaxy
is around 14 billion years old (the age of its oldest star, just around
the corner, a few dozen light years away), so 14E9 / 100 -- that galaxy
could by around 1400 Mys old. So, the universe must be *AT LEAST* 15Gy old.

Host galaxies of quasars are very difficult to see. The survey mentioned
above has around 1000 points, somehow a good sample, but still not very
precise. Also, there is no reason to suppose a linear relationship
between time and size... Old galaxies could be small also, but if they
host a quasar, I suppose they should be big. And to build big things you
need time.

A test of your hypothesis would be to observe that galaxy for a month to
see if it emits a GRB...
  #12  
Old December 22nd 17, 01:18 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default A quasar, too heavy to be true

In article , Gary
Harnagel writes:

Well, maybe no outright contradicting the BB, but it doesn't agree with the
experimental evidence without inflation:


The Big Bang means that the universe is expanding from a hotter, denser
state. Don't move the goalposts by redefining "big bang". Even so, one
can have both the big bang and inflation, which is what most
cosmologists believe.

"Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful
service by bringing all the Inflationists out of their shell, and
giving them a black eye." - Roger Penrose


Despite his substantial contributions, Penrose is now an outsider.

"Even from the beginning, inflation looked like a kluge to me-- I rapidly
formed the opinion that these guys were just making it up as they went
along" -- Neil Turok


Turok has his own axe to grind, with Steinhardt. Check it out. Do you
think that it is more believable?

And a "singularity" is certainly unphysical. It means the physics
has broken down. It would seem that alternatives might exist:


No-one believes that singularities actually exist.

https://www.edge.org/conversation/pa...aul-steinhardt

http://clearlyexplained.com/answers/membranetheory.html


Where are the testable, falsifiable predictions which differ from other
theories?
  #13  
Old December 23rd 17, 04:16 PM posted to sci.astro.research
Phillip Helbig
external usenet poster
 
Posts: 38
Default A quasar, too heavy to be true

In article , jacobnavia
writes:

Not necessarily, those mysterious processes created "out of some random
fluctuation" made those seeds and that quasar comes into being just a
few hundred million years later.


What is mysterious? Why the scare quotes? Both are indications that
you are not convinced of your own arguments, otherwise such rhetorical
devices would not be necessary.

And nothing less than a black hole of
1E4 solar masses. It seems (to me) impossible that gravity can condense
something at those temperatures.


Then read up on your physics.


Yes, let's do that.

Primordial black holes were a speculation within big bang theory that
was never observed.


What is the difference between a speculation, a hypothesis, and a
theory? One reason people don't take your arguments seriously is that
you argue rhetorically, not scientifically.

I would like to remember your own words in this
discussion group when discussing with Mr Oldershaw when you argued
against the black holes he proposed.


In a completely different mass range.

Observations rule out the existence of many small black holes because
they would bend light and that wasn't observed. That is what you said.


Yes, in the mass range Oldershaw proposed (within a couple of orders of
magnitude of a solar mass.

Now you propose that big black holes were created somehow from the
"start". They would become the nucleous of future galaxies.


It is not my proposal, but an idea with a long history in the
literature, and is not an ad-hoc hypothesis.

Of course "some random fluctuation" could create anything, including a
very convenient "seed" to grow up a huge galaxy in no time.

I just find that unlikely.


"Just finding" is not science.

  #14  
Old December 23rd 17, 04:17 PM posted to sci.astro.research
Gary Harnagel
external usenet poster
 
Posts: 659
Default A quasar, too heavy to be true

On Thursday, December 21, 2017 at 5:18:17 PM UTC-7, Phillip Helbig (undress to reply) wrote:

In article , Gary
Harnagel writes:

Well, maybe no outright contradicting the BB, but it doesn't agree with the
experimental evidence without inflation:


The Big Bang means that the universe is expanding from a hotter, denser
state. Don't move the goalposts by redefining "big bang". Even so, one
can have both the big bang and inflation, which is what most
cosmologists believe.

"Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful
service by bringing all the Inflationists out of their shell, and
giving them a black eye." - Roger Penrose


Despite his substantial contributions, Penrose is now an outsider.


So the inflationists voted on physics?

"Even from the beginning, inflation looked like a kluge to me-- I rapidly
formed the opinion that these guys were just making it up as they went
along" -- Neil Turok


Turok has his own axe to grind, with Steinhardt. Check it out. Do you
think that it is more believable?


Sure they have their own ax to grind. So did Lemaitre. So does Hawking.
Is there anything to the claim made at the end of "Theory of Everything"
that Hawking is now trying to refute that time had a beginning?

And a "singularity" is certainly unphysical. It means the physics
has broken down. It would seem that alternatives might exist:


No-one believes that singularities actually exist.


Of course not, but they still exist in the mathematics used to describe the
BB and are still discussed glibly.

https://www.edge.org/conversation/pa...aul-steinhardt

http://clearlyexplained.com/answers/membranetheory.html


Where are the testable, falsifiable predictions which differ from other
theories?


It will come. And it's funny that mathematics with singularities is used
to validate predictions, no?

  #15  
Old December 23rd 17, 04:30 PM posted to sci.astro.research
Phillip Helbig
external usenet poster
 
Posts: 38
Default A quasar, too heavy to be true

In article , Gary
Harnagel writes:

"Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful
service by bringing all the Inflationists out of their shell, and
giving them a black eye." - Roger Penrose


Despite his substantial contributions, Penrose is now an outsider.


So the inflationists voted on physics?


I'm not sure what you mean here. Of course, science is not a democracy;
the majority can be wrong. However, there is a consensus that
inflation probably happened and that Penrose is probably wrong on this
point. In any case, there is debate, and the issue is not solved by
quoting arguments from only one side (especially the minority).

"Even from the beginning, inflation looked like a kluge to me-- I rapidly
formed the opinion that these guys were just making it up as they went
along" -- Neil Turok


Turok has his own axe to grind, with Steinhardt. Check it out. Do you
think that it is more believable?


Sure they have their own ax to grind. So did Lemaitre. So does Hawking.


The point is that the quote makes it sound like they have some
independent evidence against inflation, whereas in fact they are touting
their own alternative theory. As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to
another hypothesis attempting to explain the same thing.

Is there anything to the claim made at the end of "Theory of Everything"
that Hawking is now trying to refute that time had a beginning?


Whether or not time had a beginning does not alter the fact that we can
trace the evolution of the universe back to a time when it was very hot
and very dense. By convention, the time at which it had infinite
density according to a naive extrapolation (which no-one believes
accurately describes the very early universe) is known as the big bang.

And it's funny that mathematics with singularities is used
to validate predictions, no?


No, because they are not used to validate predictions in the regime with
singularities. I can navigate fine with latitude and longitude as long
as I am not at the north or south pole.

  #16  
Old December 24th 17, 09:24 PM posted to sci.astro.research
Gary Harnagel
external usenet poster
 
Posts: 659
Default A quasar, too heavy to be true

On Saturday, December 23, 2017 at 8:30:10 AM UTC-7, Phillip Helbig (undress to reply) wrote:

In article , Gary
Harnagel writes:

"Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful
service by bringing all the Inflationists out of their shell, and
giving them a black eye." - Roger Penrose

Despite his substantial contributions, Penrose is now an outsider.


So the inflationists voted on physics?


I'm not sure what you mean here. Of course, science is not a democracy;
the majority can be wrong. However, there is a consensus that
inflation probably happened and that Penrose is probably wrong on this
point. In any case, there is debate, and the issue is not solved by
quoting arguments from only one side (especially the minority).


The "arguments" from the "other side" are taken as FACT:

https://www.space.com/52-the-expandi...-to-today.html

"The universe was born with the Big Bang as an unimaginably hot, dense point.
When the universe was just 10-34 of a second or so old -- that is, a hundredth
of a billionth of a trillionth of a trillionth of a second in age -- it
experienced an incredible burst of expansion known as inflation, in which
space itself expanded faster than the speed of light."

The only argument I see FOR inflation is the uniformity of the CMBR.
Steinhardt has another take on it.

"Even from the beginning, inflation looked like a kluge to me-- I
rapidly formed the opinion that these guys were just making it up
as they went along" -- Neil Turok

Turok has his own axe to grind, with Steinhardt. Check it out. Do you
think that it is more believable?


Sure they have their own ax to grind. So did Lemaitre. So does Hawking.


The point is that the quote makes it sound like they have some
independent evidence against inflation, whereas in fact they are touting
their own alternative theory.


Sure. It's another way to explain a conundrum: How the heck did the CMBR
get so uniform? I think it's a good thing to have alternate theories. It
keeps one's mind loosened up and not moribund.

As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to
another hypothesis attempting to explain the same thing.


So he was a smart guy and found a way to propose a theory consistent with
both GR and his religion.

Is there anything to the claim made at the end of "Theory of Everything"
that Hawking is now trying to refute that time had a beginning?


Whether or not time had a beginning does not alter the fact that we can
trace the evolution of the universe back to a time when it was very hot
and very dense.


Sure, but not so dense that collapse is inevitable. And it doesn't matter
that quantum effects "may" prevent a singularity. It's unlikely that they
can be responsible for an expansion. It seems to me that expansion is
possible only if the initial size/mass is great enough (i.e., greater than
the Schwarzschild radius.

Note that a mass with density only that of water and with a radius out to
the asteroid belt would form a black hole from which nothing could escape.

There are various estimates for the mass of the universe:

http://hypertextbook.com/facts/2006/...cPherson.shtml

varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infinity).
For the mass range indicated, the Schw. radius varies from 16000 to 160
trillion light-years, it being 1.6 billion light-years for M = 1e55 kg.

By convention, the time at which it had infinite
density according to a naive extrapolation (which no-one believes
accurately describes the very early universe) is known as the big bang.


So what do you think obviates infinite density? More importantly, what
prevents all the initial matter from being inside the Schw. radius?

And it's funny that mathematics with singularities is used
to validate predictions, no?


No, because they are not used to validate predictions in the regime with
singularities. I can navigate fine with latitude and longitude as long
as I am not at the north or south pole.


There is no new physics at the poles. You just need a different math.
In the case of cosmology, are you hoping for a new mathematics or a new
physics? Steinhardt's theory proposes a new physics, but he needs a new
mathematics to make predictions to validate his theory.

A question I've had: How can the CMBR be light from the BB? Shouldn't
that light have passed us long, long ago?

[[Mod. note -- That's a FAQ. See, for example
http://www.askamathematician.com/201...ady-passed-us/
https://www.quora.com/Why-is-the-cos...d-still-around
-- jt]]
  #17  
Old December 25th 17, 09:20 PM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default A quasar, too heavy to be true

In article , Gary
Harnagel writes:

The "arguments" from the "other side" are taken as FACT:

https://www.space.com/52-the-expandi...-bang-to-toda=

y.html

space.com is hardly the best place to see what scientists really
believe.

"The universe was born with the Big Bang as an unimaginably hot, dense po=

int.
When the universe was just 10-34 of a second or so old -- that is, a hund=

redth
of a billionth of a trillionth of a trillionth of a second in age -- it
experienced an incredible burst of expansion known as inflation, in which
space itself expanded faster than the speed of light."


Yes, this is the standard idea.

The only argument I see FOR inflation is the uniformity of the CMBR.


The fact that the CMB power spectrum looks like what one would predict
from amplified quantum fluctuations is another good argument. ANY good
theory has to explain the uniformity of the CMB.

Steinhardt has another take on it.


That's fine. The way forward is to propose experiments which will
distinguish between hypotheses.

As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to
another hypothesis attempting to explain the same thing.


So he was a smart guy and found a way to propose a theory consistent with
both GR and his religion.


Yes, Lema=EEtre was a priest, but the idea that he favoured the big bang
since it is consistent with his theology goes against all we know about
him.

Sure, but not so dense that collapse is inevitable. And it doesn't matte=

r
that quantum effects "may" prevent a singularity. It's unlikely that the=

y
can be responsible for an expansion.


Who said that they are?

It seems to me that expansion is
possible only if the initial size/mass is great enough (i.e., greater tha=

n
the Schwarzschild radius.


The Schwarzschild radius is not applicable here; it is applicable in
static asymptotically flat space-times.

Note that a mass with density only that of water and with a radius out to
the asteroid belt would form a black hole from which nothing could escape=

..

There are various estimates for the mass of the universe:

http://hypertextbook.com/facts/2006/...cPherson.shtml

varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infini=

ty).
For the mass range indicated, the Schw. radius varies from 16000 to 160
trillion light-years, it being 1.6 billion light-years for M = 1e55 kg.


Don't be confused by dimensional analysis; the universe is not a black
hole, even if it is dense enough.

So what do you think obviates infinite density?


The answer will be given by a theory of quantum gravity. Do you have
one?

There is no new physics at the poles. You just need a different math.
In the case of cosmology, are you hoping for a new mathematics or a new
physics? Steinhardt's theory proposes a new physics, but he needs a new
mathematics to make predictions to validate his theory.


He needs falsifiable predictions to which can differentiate his theory
from others.
  #18  
Old December 26th 17, 09:09 AM posted to sci.astro.research
Gary Harnagel
external usenet poster
 
Posts: 659
Default A quasar, too heavy to be true

On Monday, December 25, 2017 at 1:20:57 PM UTC-7, Phillip Helbig (undress to reply) wrote:

In article , Gary
Harnagel writes:

The "arguments" from the "other side" are taken as FACT:

https://www.space.com/52-the-expandi...-to-today.html


space.com is hardly the best place to see what scientists really
believe.

"The universe was born with the Big Bang as an unimaginably hot, dense
point. When the universe was just 10-34 of a second or so old -- that
is, a hundredth of a billionth of a trillionth of a trillionth of a
second in age -- it experienced an incredible burst of expansion known
as inflation, in which space itself expanded faster than the speed of
light."


Yes, this is the standard idea.


Which came from space.com, so I don't understand your snide comment.

The only argument I see FOR inflation is the uniformity of the CMBR.


The fact that the CMB power spectrum looks like what one would predict
from amplified quantum fluctuations is another good argument. ANY good
theory has to explain the uniformity of the CMB.


Steinhardt's idea is one BIG quantum fluctuation.

Steinhardt has another take on it.


That's fine. The way forward is to propose experiments which will
distinguish between hypotheses.


It's hard to propose experiments for something SO big. What Steinhardt
needs are some little predictions, though.

As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to
another hypothesis attempting to explain the same thing.


So he was a smart guy and found a way to propose a theory consistent with
both GR and his religion.


Yes, Lema=EEtre was a priest, but the idea that he favoured the big bang
since it is consistent with his theology goes against all we know about
him.


You think his belief system had NOTHING to do with it? Each of us has our
own model of the universe that we have developed over our lives. I have
mine and you have yours ... and Lemaitre had his.

Sure, but not so dense that collapse is inevitable. And it doesn't
matter that quantum effects "may" prevent a singularity. It's unlikely
that they can be responsible for an expansion.


Who said that they are?


I think we'll have to look outside our universe for the that, but it COULD
be quantum effects (brane theory is a quantum theory).

It seems to me that expansion is possible only if the initial size/mass
is great enough (i.e., greater than the Schwarzschild radius.


The Schwarzschild radius is not applicable here; it is applicable in
static asymptotically flat space-times.


It seems to be quite close to that now. Why propose that it was different
in a past that we can't detect?

Note that a mass with density only that of water and with a radius out
to the asteroid belt would form a black hole from which nothing could
escape.

There are various estimates for the mass of the universe:

http://hypertextbook.com/facts/2006/...cPherson.shtml

varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes
infinity).
For the mass range indicated, the Schw. radius varies from 16000 to 160
trillion light-years, it being 1.6 billion light-years for M = 1e55 kg.


Don't be confused by dimensional analysis;


That's NOT "dimensional analysis." You might repeat your claim that the
Schwarzschild model doesn't apply.

the universe is not a black hole, even if it is dense enough.


How do you know this?

So what do you think obviates infinite density?


The answer will be given by a theory of quantum gravity. Do you have
one?


Not me! :-)

There is no new physics at the poles. You just need a different math.
In the case of cosmology, are you hoping for a new mathematics or a new
physics? Steinhardt's theory proposes a new physics, but he needs a new
mathematics to make predictions to validate his theory.


He needs falsifiable predictions to which can differentiate his theory
from others.


Indeed. There are quantum gravity theories that equate to GR in the weak
field. String theory is one of them. But perhaps they'll only get
differentiation under conditions we can never find without our own black
hole to play with.

  #19  
Old December 26th 17, 07:40 PM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
external usenet poster
 
Posts: 273
Default A quasar, too heavy to be true

In article , Gary
Harnagel writes:

The "arguments" from the "other side" are taken as FACT:

https://www.space.com/52-the-expandi...-big-bang-to-=

today.html

space.com is hardly the best place to see what scientists really
believe.

"The universe was born with the Big Bang as an unimaginably hot, dens=

e
point. When the universe was just 10-34 of a second or so old -- tha=

t
is, a hundredth of a billionth of a trillionth of a trillionth of a
second in age -- it experienced an incredible burst of expansion know=

n
as inflation, in which space itself expanded faster than the speed of
light."


Yes, this is the standard idea.


Which came from space.com, so I don't understand your snide comment.


space.com is basically an internet newspaper. Some things they write
are formally correct, some are not. At best, you could argue that
space.com takes the standard scenario as "fact" instead of "hypothesis".

It's hard to propose experiments for something SO big. What Steinhardt
needs are some little predictions, though.


Indeed.

As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to=


another hypothesis attempting to explain the same thing.

So he was a smart guy and found a way to propose a theory consistent =

with
both GR and his religion.


Yes, Lema=EEtre was a priest, but the idea that he favoured the big ban=

g
since it is consistent with his theology goes against all we know about=


him.


You think his belief system had NOTHING to do with it? Each of us has ou=

r
own model of the universe that we have developed over our lives. I have
mine and you have yours ... and Lemaitre had his.


Yes, he was a priest, but, unlike some other scientists who are
Christian (i.e., Christian scientists, not necessarily Christian
Scientists), such as Don Page, he managed to keep the two areas
separate. The Big Bang really has little to do with the biblical
creation story, apart from the fact that in both the universe is not
infinitely old. This is a superficial similarity.

Sure, but not so dense that collapse is inevitable. And it doesn't
matter that quantum effects "may" prevent a singularity. It's unlike=

ly
that they can be responsible for an expansion.


Who said that they are?


I think we'll have to look outside our universe for the that, but it COUL=

D
be quantum effects (brane theory is a quantum theory).


I meant "Who said that they are responsible for expansion?"

It seems to me that expansion is possible only if the initial size/ma=

ss
is great enough (i.e., greater than the Schwarzschild radius.


The Schwarzschild radius is not applicable here; it is applicable in
static asymptotically flat space-times.


It seems to be quite close to that now. Why propose that it was differen=

t
in a past that we can't detect?


Because the Schwarzschild radius, as I already mentioned, applies in an
asymptotically flat spacetime. That does not describe the universe.

Note that a mass with density only that of water and with a radius ou=

t
to the asteroid belt would form a black hole from which nothing could
escape.

There are various estimates for the mass of the universe:

http://hypertextbook.com/facts/2006/...cPherson.shtml

varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes
infinity).
For the mass range indicated, the Schw. radius varies from 16000 to 1=

60
trillion light-years, it being 1.6 billion light-years for M = 1e55=

kg.

Don't be confused by dimensional analysis;


That's NOT "dimensional analysis." You might repeat your claim that the
Schwarzschild model doesn't apply.


The mass and radius of a spatially closed universe correspond to those
of a black hole, basically because of "dimensional analysis", not
because the universe is a black hole.

the universe is not a black hole, even if it is dense enough.


How do you know this?


Maybe the moderator can insert some standard text here. Basically, a
black hole is a region WITHIN space(time).

[[Mod. note -- Ok. This is basically a question of what we mean by
the phrase "black hole". The standard definition is that it's a region
from which light rays can't escape to "far away" (from the black hole
region). Among other things, this definition relies on their being a
set of events (points in spacetime) that we're willing to call "far away"
(from the black hole(s)).

But there's no meaningful way to say that some points in spacetime are
"far away" from the entire universe. So, there's no meaningful way to
even ask the question "is the universe a black hole".
-- jt]]

Indeed. There are quantum gravity theories that equate to GR in the weak
field. String theory is one of them.


Also a problem of a lack of testable predictions.
  #20  
Old December 29th 17, 04:04 AM posted to sci.astro.research
Gary Harnagel
external usenet poster
 
Posts: 659
Default A quasar, too heavy to be true

On Tuesday, December 26, 2017 at 11:40:23 AM UTC-7, Phillip Helbig (undress to reply) wrote:

In article , Gary
Harnagel writes:

Which came from space.com, so I don't understand your snide comment.


space.com is basically an internet newspaper. Some things they write
are formally correct, some are not. At best, you could argue that
space.com takes the standard scenario as "fact" instead of "hypothesis".

It's hard to propose experiments for something SO big. What Steinhardt
needs are some little predictions, though.


Indeed.

You think his belief system had NOTHING to do with it? Each of us has
our own model of the universe that we have developed over our lives.
I have mine and you have yours ... and Lemaitre had his.


Yes, he was a priest, but, unlike some other scientists who are
Christian (i.e., Christian scientists, not necessarily Christian
Scientists), such as Don Page, he managed to keep the two areas
separate.


I didn't realize that about Don Page, or much about him at all. From this
little treatise:

http://www.preposterousuniverse.com/...and-cosmology/

One Bob Zannelli responded, "Don Page is a first rate cosmologist, and a very
nice guy to boot. He is scrupulously honest and while I reject his evangelical
Christianity I have great respect for him."

I don't understand your denigration of him.

[[Mod. note -- For an overview of Don Page's work, see
http://arxiv.org:443/find/astro-ph/1.../0/1/0/all/0/1
Note that just searching on "Page_D" produces a mixture of Don Page's
work and those of a different person, Dany Page.
-- jt]]

The Big Bang really has little to do with the biblical creation story,
apart from the fact that in both the universe is not infinitely old.


Well, we can argue THAT sometime :-) I mean, it all depends upon the nature
of God and the definition of the universe.

This is a superficial similarity.


I agree. Either can have a previous genesis depending ....

I think we'll have to look outside our universe for the that, but it
COULD be quantum effects (brane theory is a quantum theory).


I meant "Who said that they are responsible for expansion?"


If one posits extreme temperatures at the "beginning" then it seems that
you're dealing with photons (or perhaps other relativistic particles),
so expansion is inevitable.

It seems to me that expansion is possible only if the initial
size/mass is great enough (i.e., greater than the Schwarzschild
radius.

The Schwarzschild radius is not applicable here; it is applicable in
static asymptotically flat space-times.


It seems to be quite close to that now. Why propose that it was
different in a past that we can't detect?


Because the Schwarzschild radius, as I already mentioned, applies in an
asymptotically flat spacetime. That does not describe the universe.


Well, that flat claim of yours doesn't agree with observation:

https://en.wikipedia.org/wiki/Flatness_problem

Note that a mass with density only that of water and with a radius
out to the asteroid belt would form a black hole from which nothing
could escape.

There are various estimates for the mass of the universe:

http://hypertextbook.com/facts/2006/...cPherson.shtml

varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes
infinity).
For the mass range indicated, the Schw. radius varies from 16000 to
160 trillion light-years, it being 1.6 billion light-years for
M = 1e55 kg.

Don't be confused by dimensional analysis;


That's NOT "dimensional analysis." You might repeat your claim that the
Schwarzschild model doesn't apply.


The mass and radius of a spatially closed universe correspond to those
of a black hole, basically because of "dimensional analysis", not
because the universe is a black hole.


You'll have to explain that in much more detail. I don't see (1 - 2*G*M/rc^2)
as "dimensional analysis."

the universe is not a black hole, even if it is dense enough.


How do you know this?


Maybe the moderator can insert some standard text here. Basically, a
black hole is a region WITHIN space(time).

[[Mod. note -- Ok. This is basically a question of what we mean by
the phrase "black hole". The standard definition is that it's a region
from which light rays can't escape to "far away" (from the black hole
region). Among other things, this definition relies on their being a
set of events (points in spacetime) that we're willing to call "far away"
(from the black hole(s)).

But there's no meaningful way to say that some points in spacetime are
"far away" from the entire universe. So, there's no meaningful way to
even ask the question "is the universe a black hole".
-- jt]]


Of course, this ASSUMES that the FLRW metric describes our universe. Since,
as Don Page pointed out in the link given above, "We simply do not know
whether or not our universe had a beginning."

My belief system says that it didn't. And I reject the "bounce" model, too.
IOW, "big bangs" happen repeatedly without bouncing. In such a universe
(multiverse?) curvature is only a "local" phenomenon.

Indeed. There are quantum gravity theories that equate to GR in the weak
field. String theory is one of them.


Also a problem of a lack of testable predictions.


Sure, but there are hints that may lead to testable predictions. One is
that gravity "leaks." Another is the possibility of "Alice" matter:

https://en.wikipedia.org/wiki/Mirror_matter

The weak interaction breaks parity. Why? Is it possible that not only
does gravity leak, but parity does, too? Are dark matter and Alice matter
the same thing? Beta decay is due to the weak interaction, and anomalies
in the beta decay of several isotope species have been noted:

https://arxiv.org/abs/0808.3283

Is dark matter in an adjacent brane? Is the weak interaction another way
to probe adjacent branes? Perhaps the assertion that string theory can
make no predictions is itself a belief system.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Could Delta IV Heavy use the same technique as Falcon Heavy Alan Erskine[_3_] Space Shuttle 1 May 20th 11 07:56 AM
Whoa, it can't be true, it can't be true, William Shatner knows,he'll protect us LIBERATOR[_3_] History 2 March 24th 09 06:28 PM
Heavy H = Lots of Heavy Compounds G=EMC^2 Glazier Misc 3 November 12th 05 07:12 PM
Since Boeing and LM are partnering 50/50 and Boeing already has Delta IV Heavy does that mean we'll never see the Atlas V Heavy? D. Scott Ferrin History 5 May 6th 05 05:34 PM
Delta IV Heavy: Heavy Enough for Mars Damon Hill Policy 1 December 22nd 04 08:39 PM


All times are GMT +1. The time now is 08:31 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.