So I have found out that the universe is isotropic and full of
radiation left over from the Big Bang. At one time this radiation was
very energetic but due to the expansion of the universe gradually
increased in wavelength. At one time much of this radiation must have
been in the range of visible light. So the the entire universe was
suffused with visible light.

Of course there were no people and no planets at this time but it is
fun to think about nevertheless. How bright was this light? What was
the temperature? The two most interesting times to know would be
when visible light was at a peak and when it completely disappeared.
Would the light ever be colored or always appear white?

It seems that if you wanted darkness you'd have to get inside a box of
matter. Did suitable matter exist? I bet it didn't so that there was
light literally everywhere.

"Patrick Powers" wrote in message
m...
So I have found out that the universe is isotropic and full of
radiation left over from the Big Bang. At one time this radiation was
very energetic but due to the expansion of the universe gradually
increased in wavelength. At one time much of this radiation must have
been in the range of visible light. So the the entire universe was
suffused with visible light.

Of course there were no people and no planets at this time but it is
fun to think about nevertheless. How bright was this light? What was
the temperature? The two most interesting times to know would be
when visible light was at a peak and when it completely disappeared.
Would the light ever be colored or always appear white?

The Sun's light is a mixture of colors, the combination
of which we call "white" (or yellow-white).

How hot is the Sun's photosphere? About 4500K.


It seems that if you wanted darkness you'd have to get inside a box of
matter. Did suitable matter exist? I bet it didn't so that there was
light literally everywhere.

Greg Neill wrote:

"Patrick Powers" wrote in message
m...
So I have found out that the universe is isotropic and full of
radiation left over from the Big Bang. At one time this radiation was
very energetic but due to the expansion of the universe gradually
increased in wavelength. At one time much of this radiation must have
been in the range of visible light. So the the entire universe was
suffused with visible light.

Of course there were no people and no planets at this time but it is
fun to think about nevertheless. How bright was this light? What was
the temperature? The two most interesting times to know would be
when visible light was at a peak and when it completely disappeared.
Would the light ever be colored or always appear white?

The Sun's light is a mixture of colors, the combination
of which we call "white" (or yellow-white).

How hot is the Sun's photosphere? About 4500K.

Almost 6000 K

Greg After the first minute after the BB it went into its radiation area
and during that time its density and gamma photons were very much like
the core of our sun.this lasted 300,000 years. Like the emission of
photons today from the suns core they are gamma photons,but after
100,000 years to get to the sun's surface they break through as "white"
light. Bert

G=EMC^2 Glazier wrote:

Greg After the first minute after the BB it went into its radiation area
and during that time its density and gamma photons were very much like
the core of our sun.this lasted 300,000 years. Like the emission of
photons today from the suns core they are gamma photons,but after
100,000 years to get to the sun's surface they break through as "white"
light. Bert

absorption, emission, absorption, emission, ....

The primary fusion processes in the core of the
Sun the summary equation works out to be

6H -- He - 2H + 26.72 MeV

The energy is carried away by gamma photons, neutrinos and
increased kinetic energy... but what is really important for you
to understand, is that the photos are absorbed and re-emmitted
averaging 170,000 years to make it to the surface.

It's not gamma that leaves the photosphere, but much longer
wavelength photons in with the peak wavelength falling in the
visible spectrum. In all those absorptions and re-emmission the
wavelength get longer as kinetic energy is imparted to the
particles in the exchange.

In the Sun, the original source of the light is the p-p chain,
Certainly in the protosun the source of light was gravitational
collapse. On the main sequence the Sun has come to equilibrium
between the energy produced by nuclear reaction in the core and
gravity trying to collapse the Sun.

Your statement, "Light comes from the acquisition of electrons by
atoms or nuclear matter", should be replaced by, "light comes from
nuclear fusion in the core of the Sun modified by successive
absorption and re-emission by matter as it works its way to the
surface".

Visual Aids
http://www.mhhe.com/physsci/astronom...r17/17f02.html
http://www.mhhe.com/physsci/astronom...r17/17f03.html
http://www.mhhe.com/physsci/astronom...r17/17f01.html

"G=EMC^2 Glazier" wrote in message
...
Greg After the first minute after the BB it went into its radiation area
and during that time its density and gamma photons were very much like
the core of our sun.this lasted 300,000 years. Like the emission of
photons today from the suns core they are gamma photons,but after
100,000 years to get to the sun's surface they break through as "white"
light. Bert


Why does it take so long for photons to break out of the sun? I've always
wondered that.

Sean

"Sam Wormley" wrote in message ...
Greg Neill wrote:

"Patrick Powers" wrote in message
m...
So I have found out that the universe is isotropic and full of
radiation left over from the Big Bang. At one time this radiation was
very energetic but due to the expansion of the universe gradually
increased in wavelength. At one time much of this radiation must have
been in the range of visible light. So the the entire universe was
suffused with visible light.

Of course there were no people and no planets at this time but it is
fun to think about nevertheless. How bright was this light? What was
the temperature? The two most interesting times to know would be
when visible light was at a peak and when it completely disappeared.
Would the light ever be colored or always appear white?

The Sun's light is a mixture of colors, the combination
of which we call "white" (or yellow-white).

How hot is the Sun's photosphere? About 4500K.

Almost 6000 K

Okay, 6000K.

The very top of the photosphere is at about 4500K, and the
temperature rises to about 7600K at a depth of 400km. Of
course, the Sun becomes more opaque with depth. I suppose
the 6000K figure is the net result of the light contributions
from all depths that make it out.

Greg Neill wrote:

"Sam Wormley" wrote in message ...
Greg Neill wrote:

"Patrick Powers" wrote in message
m...
So I have found out that the universe is isotropic and full of
radiation left over from the Big Bang. At one time this radiation was
very energetic but due to the expansion of the universe gradually
increased in wavelength. At one time much of this radiation must have
been in the range of visible light. So the the entire universe was
suffused with visible light.

Of course there were no people and no planets at this time but it is
fun to think about nevertheless. How bright was this light? What was
the temperature? The two most interesting times to know would be
when visible light was at a peak and when it completely disappeared.
Would the light ever be colored or always appear white?

The Sun's light is a mixture of colors, the combination
of which we call "white" (or yellow-white).

How hot is the Sun's photosphere? About 4500K.

Almost 6000 K

Okay, 6000K.

The very top of the photosphere is at about 4500K, and the
temperature rises to about 7600K at a depth of 400km. Of
course, the Sun becomes more opaque with depth. I suppose
the 6000K figure is the net result of the light contributions
from all depths that make it out.


Using Wien's Law (and measuring the wavelength of the Solar spectrum)
http://scienceworld.wolfram.com/physics/WienLaw.html

results in a "surface temperature" of just under 6000K
Ref: http://www.edu-observatory.org/eo/sun.html

"Sam Wormley" wrote in message ...
Greg Neill wrote:


The very top of the photosphere is at about 4500K, and the
temperature rises to about 7600K at a depth of 400km. Of
course, the Sun becomes more opaque with depth. I suppose
the 6000K figure is the net result of the light contributions
from all depths that make it out.


Using Wien's Law (and measuring the wavelength of the Solar spectrum)
http://scienceworld.wolfram.com/physics/WienLaw.html

results in a "surface temperature" of just under 6000K
Ref: http://www.edu-observatory.org/eo/sun.html

The 6000K figure (closer to 5800K) is the effective temperature
of the Sun's "surface", t_eff. t_eff is the value commonly
used by astronomers when describing the temperatures of
stars.

The temperature of the photosphere does vary with depth as I
noted. The cooler bits higher up in the photosphere are evidenced
in the limb darkening effect, where the Sun's brightness appears
to dim near the edges -- most of these photons come from the
upper portions of the photosphere.

When all is said and done though, I admit that I erred when
I provided the 4500K value to the OP. It's the value of t_eff,
6000K for the Sun, that gives the equivalent black body spectrum.

In sci.physics, Sam Wormley

wrote
on Sat, 22 May 2004 18:18:47 GMT
:
Greg Neill wrote:

"Patrick Powers" wrote in message
m...
So I have found out that the universe is isotropic and full of
radiation left over from the Big Bang. At one time this radiation was
very energetic but due to the expansion of the universe gradually
increased in wavelength. At one time much of this radiation must have
been in the range of visible light. So the the entire universe was
suffused with visible light.

Of course there were no people and no planets at this time but it is
fun to think about nevertheless. How bright was this light? What was
the temperature? The two most interesting times to know would be
when visible light was at a peak and when it completely disappeared.
Would the light ever be colored or always appear white?

The Sun's light is a mixture of colors, the combination
of which we call "white" (or yellow-white).

How hot is the Sun's photosphere? About 4500K.

Almost 6000 K

According to celestia (a program which simulates an
impossible spacecraft traveling in the neighborhood of
the solar system, with some gorgeous views), the Sun's
temperature is 5860 K, and the Sun is a G2 V.

It also states Arcturus has a surface temperature of 4900K
(class K2 III) and Antares has 3720 K (class M1 I-b).

And then there's Spica, with a temperature of 25400 K (!!)
befitting its class B1 V status. Interestingly, Spica
is only 2.52x the Sun's size -- smaller than Vega, which
only manages 9520 K despite its 2.68x size.

Fun little program. :-)

--
#191,
It's still legal to go .sigless.