Bill Bryson and the big bang

On Fri, 02 Jul 2004 10:37:55 +0200, Bjoern Feuerbacher
wrote:

[snip]

We are not communicating well, so I'll say good bye.

The effects that I was seeking in were penetration of solid structures
and production of damage within, or perhaps an image on emerging.

I have the idea that matter contracts and time `passes' slower in
space acceleration (relative to earth) in absence of much mass in the
vicinity.

I have the idea that the atmosphere as part of the earth is quite
massive judging by atmospheric pressure, and that the muon experiment
is not helpful.

I have the idea that the standard earth clock measures time by means
of radioactive decay of Cesium . . And that decay was the mechanism of
an atomic clock.

I used UVL to indicate that it was a portion of the infrared, visible,
ultraviolet light spectrum.

Finally, yes I'm familiar with the photoelectric effect, it just
seemed a little out of place.

Other points raised by you have slipped my mind.

And for some reason it comes to my mind that it was a favorite ploy of
Socrates to always answer a question with a question. (you will
probably have no idea what I'm thinking about. and think irrelevant)

ta ta

vonroach wrote:
On Fri, 02 Jul 2004 10:37:55 +0200, Bjoern Feuerbacher
wrote:


[snip]


We are not communicating well, so I'll say good bye.

The effects that I was seeking in were penetration of solid structures
and production of damage within,

For that, the energy of individual photons is mainly responsible, so
no, one couldn't "simulate" that with light of lower frequency.


or perhaps an image on emerging.

Sorry, I don't understand what you mean here.


I have the idea that matter contracts and time `passes' slower in
space acceleration (relative to earth) in absence of much mass in the
vicinity.

Where did you get that idea from?



I have the idea that the atmosphere as part of the earth is quite
massive judging by atmospheric pressure, and that the muon experiment
is not helpful.

So you attribute the muon time dilation to the mass of the atmosphere,
or what???

The speed of these muons was measured. If you calculate the time
dilation from that speed, according to SR, you get consistent results.


Further, time dilation of the decay rate of fast-moving particles was
alsp measured in the laboratory. The time dilation rate there also was
shown to be consistent with the one predicted by SR.



I have the idea that the standard earth clock measures time by means
of radioactive decay of Cesium . .And that decay was the mechanism of
an atomic clock.

That idea of you is wrong. Where did you get this from?


[snip]


And for some reason it comes to my mind that it was a favorite ploy of
Socrates to always answer a question with a question. (you will
probably have no idea what I'm thinking about. and think irrelevant)

Yes, I answered some of your questions with a question. You did that,
too. Your point?


Bye,
Bjoern

vonroach wrote:
On Fri, 02 Jul 2004 10:37:55 +0200, Bjoern Feuerbacher
wrote:


[snip]


We are not communicating well, so I'll say good bye.

The effects that I was seeking in were penetration of solid structures
and production of damage within,

For that, the energy of individual photons is mainly responsible, so
no, one couldn't "simulate" that with light of lower frequency.


or perhaps an image on emerging.

Sorry, I don't understand what you mean here.


I have the idea that matter contracts and time `passes' slower in
space acceleration (relative to earth) in absence of much mass in the
vicinity.

Where did you get that idea from?



I have the idea that the atmosphere as part of the earth is quite
massive judging by atmospheric pressure, and that the muon experiment
is not helpful.

So you attribute the muon time dilation to the mass of the atmosphere,
or what???

The speed of these muons was measured. If you calculate the time
dilation from that speed, according to SR, you get consistent results.


Further, time dilation of the decay rate of fast-moving particles was
alsp measured in the laboratory. The time dilation rate there also was
shown to be consistent with the one predicted by SR.



I have the idea that the standard earth clock measures time by means
of radioactive decay of Cesium . .And that decay was the mechanism of
an atomic clock.

That idea of you is wrong. Where did you get this from?


[snip]


And for some reason it comes to my mind that it was a favorite ploy of
Socrates to always answer a question with a question. (you will
probably have no idea what I'm thinking about. and think irrelevant)

Yes, I answered some of your questions with a question. You did that,
too. Your point?


Bye,
Bjoern

[I'll post a few thoughts, since I think others, notably Bjoern, have
probably addressed many of these points.]

"JJ" == Jim Jastrzebski writes:

JJ "Joseph Lazio" wrote in message
JJ ...

GR allows for dark energy, it's what Einstein termed the
cosmological constant. (It's called "dark energy" because
inventive theorists have realized that the cosmological constant is
just one example of a larger class of potential energy fields.)
[...]

JJ Normally, it is considered a constant needed in Einstein's
JJ equation for the equation to describe stationary space of our
JJ universe. Its original value fit for such a purpose, established
JJ by EInstein, is 4 pi G rho/c2, where G is Newtonian gravitational
JJ constant, rho is the density of the universe, and c2 is of course
JJ square of speed of light.

I'd say that it is a constant in the Einstein field equations, a
particular value of which can produce a static Universe.

JJ About half a century ago there were speculations that if the
JJ cosmological constant had a different value, e.g. zero (as was
JJ assumed by Misner, Thorne, and Wheeler school of cosmology with
JJ its calling the cosmological constant "the greatest Einstein's
JJ blunder") the solutions of Einstein's equation would show
JJ expansion of space.

There's absolutely nothing in general relativity that would allow one
to "deduce" a value for the cosmological constant any more than there
is anything in Newtonian gravity that would allow one to "deduce" the
value of G. At our current level of understanding, the best one can
hope is to measure G or the Hubble parameter or the cosmological
constant. Half a century ago the experimental limits on the
cosmological constant were fairly weak but consistent with zero. In
the absence of any other information, it was logical to set it to
zero.

JJ Those speculations resulted in "big bang" model. But it turned
JJ out that the cosmological constant can't be equal zero since then
JJ the predicted expansion would have been decelerating while
JJ observations, done in January 1998, have shown that the "observed
JJ expansion" looks like accelerating (...). [...]

No, one can obtain a Big Bang model for any number of values of the
cosmological constant \Lambda. For instance, \Lambda = 0.0001 would
produce a Big Bang model as would \Lambda = 1000. (In the latter
case, of course, the Universe would have expanded so quickly that we
wouldn't be here to write about it.) For that matter, the current
experimental limits \Lambda ~ 0.7 are quite consistent with a Big Bang
model.

[...]
JJ But why do you think that we need "dark energy". What observations
JJ require it to be there?

There are a number. The Type Ia supernovae are the most famous.
However, off the top of my head, observations of clusters of galaxies,
the cosmic microwave background, galaxy number counts, radio galaxy
number counts all point toward a non-zero cosmological constant or
dark energy. The constraints on dark energy become even tighter when
one considers these experiments collectively rather than individually.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

[I'll post a few thoughts, since I think others, notably Bjoern, have
probably addressed many of these points.]

"JJ" == Jim Jastrzebski writes:

JJ "Joseph Lazio" wrote in message
JJ ...

GR allows for dark energy, it's what Einstein termed the
cosmological constant. (It's called "dark energy" because
inventive theorists have realized that the cosmological constant is
just one example of a larger class of potential energy fields.)
[...]

JJ Normally, it is considered a constant needed in Einstein's
JJ equation for the equation to describe stationary space of our
JJ universe. Its original value fit for such a purpose, established
JJ by EInstein, is 4 pi G rho/c2, where G is Newtonian gravitational
JJ constant, rho is the density of the universe, and c2 is of course
JJ square of speed of light.

I'd say that it is a constant in the Einstein field equations, a
particular value of which can produce a static Universe.

JJ About half a century ago there were speculations that if the
JJ cosmological constant had a different value, e.g. zero (as was
JJ assumed by Misner, Thorne, and Wheeler school of cosmology with
JJ its calling the cosmological constant "the greatest Einstein's
JJ blunder") the solutions of Einstein's equation would show
JJ expansion of space.

There's absolutely nothing in general relativity that would allow one
to "deduce" a value for the cosmological constant any more than there
is anything in Newtonian gravity that would allow one to "deduce" the
value of G. At our current level of understanding, the best one can
hope is to measure G or the Hubble parameter or the cosmological
constant. Half a century ago the experimental limits on the
cosmological constant were fairly weak but consistent with zero. In
the absence of any other information, it was logical to set it to
zero.

JJ Those speculations resulted in "big bang" model. But it turned
JJ out that the cosmological constant can't be equal zero since then
JJ the predicted expansion would have been decelerating while
JJ observations, done in January 1998, have shown that the "observed
JJ expansion" looks like accelerating (...). [...]

No, one can obtain a Big Bang model for any number of values of the
cosmological constant \Lambda. For instance, \Lambda = 0.0001 would
produce a Big Bang model as would \Lambda = 1000. (In the latter
case, of course, the Universe would have expanded so quickly that we
wouldn't be here to write about it.) For that matter, the current
experimental limits \Lambda ~ 0.7 are quite consistent with a Big Bang
model.

[...]
JJ But why do you think that we need "dark energy". What observations
JJ require it to be there?

There are a number. The Type Ia supernovae are the most famous.
However, off the top of my head, observations of clusters of galaxies,
the cosmic microwave background, galaxy number counts, radio galaxy
number counts all point toward a non-zero cosmological constant or
dark energy. The constraints on dark energy become even tighter when
one considers these experiments collectively rather than individually.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

"Joseph Lazio" wrote in message
...
[I'll post a few thoughts, since I think others, notably Bjoern, have
probably addressed many of these points.]

"JJ" == Jim Jastrzebski writes:

[...]
JJ But why do you think that we need "dark energy". What observations
JJ require it to be there?

There are a number. The Type Ia supernovae are the most famous.
However, off the top of my head, observations of clusters of galaxies,
the cosmic microwave background, galaxy number counts, radio galaxy
number counts all point toward a non-zero cosmological constant or
dark energy.

How do they point? By doing what? E.g. how the existence
of "clusters of galaxies" imply "dark energy"? Or couldn't Ia
supernovae or CMB exist without "dark energy"?

-- Jim

"Joseph Lazio" wrote in message
...
[I'll post a few thoughts, since I think others, notably Bjoern, have
probably addressed many of these points.]

"JJ" == Jim Jastrzebski writes:

[...]
JJ But why do you think that we need "dark energy". What observations
JJ require it to be there?

There are a number. The Type Ia supernovae are the most famous.
However, off the top of my head, observations of clusters of galaxies,
the cosmic microwave background, galaxy number counts, radio galaxy
number counts all point toward a non-zero cosmological constant or
dark energy.

How do they point? By doing what? E.g. how the existence
of "clusters of galaxies" imply "dark energy"? Or couldn't Ia
supernovae or CMB exist without "dark energy"?

-- Jim

"JJ" == Jim Jastrzebski writes:

JJ "Joseph Lazio" wrote in message
JJ ...

JJ But why do you think that we need "dark energy". What observations
JJ require it to be there?

There are a number. The Type Ia supernovae are the most famous.
However, off the top of my head, observations of clusters of
galaxies, the cosmic microwave background, galaxy number counts,
radio galaxy number counts all point toward a non-zero cosmological
constant or dark energy.

JJ How do they point? By doing what? E.g. how the existence of
JJ "clusters of galaxies" imply "dark energy"? Or couldn't Ia
JJ supernovae or CMB exist without "dark energy"?

No, various properties are difficult to understand without allowing
for some kind of dark energy. For instance, in the case of the cosmic
microwave background, one observes oscillations in its intensity.
Those oscillations are understood quite easily in terms of pressure
fluctuations in the early Universe as the CMB was forming. The linear
size of those fluctuations is given roughly by vt, where v is the
sound velocity in the plasma near the time of the formation of the CMB
and t is the age of the Univese at the time when the CMB formed.

We observe the angular size of the oscillations. Knowing their linear
sizes, allows one to determine the angular distance to these
oscillations. Based on general relativity, one knows an expression
for the angular distance to an object based on parameters such as the
density of matter, the Hubble constant, and the density of dark
energy. One can then determine which set of parameters is allowed by
the observations.

Of course, if one has just one observation (just Type Ia supernovae or
just the CMB) there are degeneracies in the constraints on the
cosmological parameters. However, different observations are
sensitive to different combinations of the cosmological parameters.

An example of this is Figure 4 of Allen et al. (2004,
astro-ph/0405340, URL:http://arxiv.org/abs/astro-ph/0405340) in
which they show the constraints placed by a couple of different
methods.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

"JJ" == Jim Jastrzebski writes:

JJ "Joseph Lazio" wrote in message
JJ ...

JJ But why do you think that we need "dark energy". What observations
JJ require it to be there?

There are a number. The Type Ia supernovae are the most famous.
However, off the top of my head, observations of clusters of
galaxies, the cosmic microwave background, galaxy number counts,
radio galaxy number counts all point toward a non-zero cosmological
constant or dark energy.

JJ How do they point? By doing what? E.g. how the existence of
JJ "clusters of galaxies" imply "dark energy"? Or couldn't Ia
JJ supernovae or CMB exist without "dark energy"?

No, various properties are difficult to understand without allowing
for some kind of dark energy. For instance, in the case of the cosmic
microwave background, one observes oscillations in its intensity.
Those oscillations are understood quite easily in terms of pressure
fluctuations in the early Universe as the CMB was forming. The linear
size of those fluctuations is given roughly by vt, where v is the
sound velocity in the plasma near the time of the formation of the CMB
and t is the age of the Univese at the time when the CMB formed.

We observe the angular size of the oscillations. Knowing their linear
sizes, allows one to determine the angular distance to these
oscillations. Based on general relativity, one knows an expression
for the angular distance to an object based on parameters such as the
density of matter, the Hubble constant, and the density of dark
energy. One can then determine which set of parameters is allowed by
the observations.

Of course, if one has just one observation (just Type Ia supernovae or
just the CMB) there are degeneracies in the constraints on the
cosmological parameters. However, different observations are
sensitive to different combinations of the cosmological parameters.

An example of this is Figure 4 of Allen et al. (2004,
astro-ph/0405340, URL:http://arxiv.org/abs/astro-ph/0405340) in
which they show the constraints placed by a couple of different
methods.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html