On 09/08/2015 18:24, Alastair McDonald wrote:
"Metman2012" wrote in message


The term cold radiation really only applies to the radiation when it arrives
at a body. If it has originated from a cooler body then it is cold radiation
and the other body will cool. If it has originated from a warmer body then
it is hot radiation and the other body will warm.



The temperature of a body depends on the net (a word of one syllable)
radiation it absorbs and emits. There is only one source for the
emissions, the body itself, but there can be lots of sources of the
radiation it is absorbing. Obviously it is the sum of the radiation from
all those sources that will determine how the temperature of the body
itself changes. And its final temperature will be reached when that sum
equals the radiation it emits as a blackbody.

Does that make sense?

Cheers, Alastair.



The second paragraph does make sense, but I notice that no mention is
made of hot or cold radiation.

But your first paragraph is less clear (partly because I have to reread
it to see what's cooling what). My understanding is that a body will
cool by itself unless it is subject to heating from another body hotter
than itself. So without the sun, the earth would be considerably cooler.
The sun itself is cooling, or at least it would be if there were no
processes maintaining it's heat. However the fuel for these will
eventually run out and it will cool of its own accord without any
nearby cool bodies making a ha'p'orth of difference.

If you have two bodies, one hotter than the other and they are touching,
then heat flows from the warmer to the cooler until they are the same
temperature. The cooler body doesn't reduce the temperature of the
warmer body. I believe this is because of increasing entropy. My
(limited) understanding of entropy is that everything is cooling and
that eventually (next week?) we will have the heat death of the
universe. Everything will be cool (pretty cold).

I suspect that we might be in a war about semantics in this thread but I
don't think it's worth arguing over as nobody will be changing their
position on it (unless it gets very hot, or cold).

"Alastair McDonald" wrote in message ...

What are these observations and experimental results
that are at odds with the existing model?

I have given two examples of observations:snip previous detail

You're clearly missing the point, whether deliberately or not I can't tell.
The observations in the experiments you quoted are perfectly well explained
by existing theory with just one type of radiation (as others have described
in detail). Hence there is no need to invoke a more complex theory.

So let me ask the important and hitherto unanswered question again. Where
are there any experimental observations that cannot be fully explained and
understood by established theory? If you can't provide an answer to this
then it's game, set and match I'm afraid. Or to put it another way, why is
there any need to postulate the existence of totally separate hot rays and
cold rays (if such a distinction is even imaginable, but which is how
everyone is interpreting what you're writing)?

Using the term 'cold radiation' makes it sound like it's possible to imagine
a device (a laser let's say, but some equivalent in your alternative
universe) that can project a beam of cold rays, which would then be able to
cool down a target indefinitely (or at least to 0K), similar to how a
conventional laser can heat a target more or less indefinitely. This is the
bizarre concept that everyone is taking exception to, if I judge the thread
content correctly.

On Sunday, August 9, 2015 at 9:30:49 PM UTC+1, JohnD wrote:
"Alastair McDonald" wrote in message ...

What are these observations and experimental results
that are at odds with the existing model?

I have given two examples of observations:snip previous detail

You're clearly missing the point, whether deliberately or not I can't tell.
The observations in the experiments you quoted are perfectly well explained
by existing theory with just one type of radiation (as others have described
in detail). Hence there is no need to invoke a more complex theory.

So let me ask the important and hitherto unanswered question again. Where
are there any experimental observations that cannot be fully explained and
understood by established theory? If you can't provide an answer to this
then it's game, set and match I'm afraid. Or to put it another way, why is
there any need to postulate the existence of totally separate hot rays and
cold rays (if such a distinction is even imaginable, but which is how
everyone is interpreting what you're writing)?

Using the term 'cold radiation' makes it sound like it's possible to imagine
a device (a laser let's say, but some equivalent in your alternative
universe) that can project a beam of cold rays, which would then be able to
cool down a target indefinitely (or at least to 0K), similar to how a
conventional laser can heat a target more or less indefinitely. This is the
bizarre concept that everyone is taking exception to, if I judge the thread
content correctly.

You judge it correctly. That's exactly what the man thinks. It is perfectly loopy.

On Sunday, August 9, 2015 at 7:59:06 PM UTC+1, Alastair wrote:
On Sunday, 9 August 2015 19:34:13 UTC+1, Dawlish wrote:

It cools via net radiation balance. It is not 'made cooler'.

So if we took the cold object away, the hot one would still cool? You are saying it is not the cold object that is making it cold.

The warmer object would cool by emitting more radiation than it gained, if the surroundings were cooler. It was not being cooled **by** the colder object.

Why can you not understand this? Cold objects do not emit a form of cryogenic radiation which cools other things. That simply does not exist and you are making yourself look foolish by inventing this concept.

On 09/08/15 18:18, Alastair McDonald wrote:
"RedAcer" wrote in message
...
On 09/08/15 14:59, Alastair wrote:
On Sunday, 9 August 2015 07:30:58 UTC+1,
wrote:
....
I hope you will now realise that you are wrong, will apologise
and admit your mistake. Cold radiation does exist.

Cheers, Alastair.

There is no such thing in Physics as "cold" - just lack of heat.

I am not saying "cold" exists. I am saying "cold radiation" exists,
in the same way cold water exists.

No. You are talking about the human experience of temperature. We are
trying to explain to you how physicists, engineers, scientists talk
about heat.
(do you really have an engineering degree? - I find that hard to believe
- what was it in?)

Why do you start your post with insults? Is that the way you were taught
science at school? Oh, I have just realised, your teacher was Dawlish!

If your hands feel extremely cold and you put them in 'cold' water from
your tap you may 'feel' the water as 'warm. Conversely if you feel
extremely hot and you put your hands in water at the same temperature
you would feel it as 'cold'.
The temperature of the water hasn't changed.

If the radiation arrives at an object and it is colder it will warm it, and
we can call the radiation hot radiation, just like your hot water.
If the radiation arrives at an object and it is warmer it will cool it, and
we can call the radiation coldradiation, just like your cold water.

Your water hadn't changed and neither has my radiation.

The point of science is to use definitions and talk precisely. Why can't
you accept this.

My definition of cold radiation IS precise. It is cold radiation if it
originated from a source colder than where it is absorbed; the difference in
temperature can be as small as you like. Can't get more precise than that!

Scientists don't talk about cold radiation.

How many do you know?

Scores. I've got a degree in Physics and spent several years working on
a PhD in low temperature solid state physics.


Are gamma rays 'hot radiation' or just photons with a specific
frequency/energy?

Can't tell if it is hot radiation until I know where the photons are
arriving.

When the photon reaches a body and is absorbed by an atom how does is it
'know' if that body is hotter or colder than the one it was emitted
from. How does the absorbing atom 'know' the temperature of the body the
photon came from?



Cheers, Alastair.

On Sunday, 9 August 2015 21:41:27 UTC+1, Dawlish wrote:

So if we took the cold object away, the hot one would still cool? You are saying it is not the cold object that is making it cold.

The warmer object would cool by emitting more radiation than it gained, if the surroundings were cooler.

And if we took the cold object away and the surrounding were not cooler what would happen?

"RedAcer" wrote in message
...

How many do you know?

Scores. I've got a degree in Physics and spent several years working on
a PhD in low temperature solid state physics.

When the photon reaches a body and is absorbed by an atom how does is it
'know' if that body is hotter or colder than the one it was emitted
from. How does the absorbing atom 'know' the temperature of the body the
photon came from?

I am tempted to reply: "The photon and atom ask a passing PhD student." :-)

The photon and the atom only "know" the photon's frequency and hence its
energy. It is the difference between the absorbed photons' and emitted
photons'
energies which determines the objects change in temperature.

Cheers, Alastair.

"JohnD" wrote in message
...
"Alastair McDonald" wrote in message ...

You're clearly missing the point, whether deliberately or not I can't
tell. The observations in the experiments you quoted are perfectly well
explained by existing theory with just one type of radiation (as others
have described in detail). Hence there is no need to invoke a more complex
theory.

So you agree that you can cool a body, or in the Pictet case a thermometer,
with radiation?

Fine, that's all I want to hear. I call that "cold radiation." Does that
make me the idiot that Dawlish is portraying?

So let me ask the important and hitherto unanswered question again. Where
are there any experimental observations that cannot be fully explained and
understood by established theory?

There are not any. I am giving you the established theory.

If you can't provide an answer to this then it's game, set and match I'm
afraid.

It has been game set and match for quite a while. There is no way that
you will accept what I have to say. This is just
a Kangaroo Court with me as a victim. Dawlish has persuaded every one to
distrust me, and just look how much he is enjoying it.

Or to put it another way, why is there any need to postulate the existence
of totally separate hot rays and cold rays (if such a distinction is even
imaginable, but which is how everyone is interpreting what you're
writing)?

As I explained elsewhere, cold radiation is just shorthand for radiation
from a colder object. Change "cold radiation " to "RFACO" if you like. I'll
still believe in it, much to Dawlish's delight.

Using the term 'cold radiation' makes it sound like it's possible to
imagine a device (a laser let's say, but some equivalent in your
alternative universe) that can project a beam of cold rays, which would
then be able to cool down a target indefinitely (or at least to 0K),
similar to how a conventional laser can heat a target more or less
indefinitely. This is the bizarre concept that everyone is taking
exception to, if I judge the thread content correctly.

Well then you must have accepted the drivel that Dawlish has been spouting.

I am not proposing a laser device to cool objects to 0K, though they do
exist https://en.wikipedia.org/wiki/Laser_cooling

I am saying with a flask full of ice and two concave mirrors it is possible
to lower the temperature in a thermometer. Note, the temperature does not
even reach 0C, far less 0K.

Actually, what the more intelligent here are objecting to is the idea that
the Earth cools at night because the incoming radiation is from a cold
source, i.e. cosmic background radiation. They seem to be arguing it is
because the Earth emits radiation that is lost to space (a rather vague
and unscientific idea , IMHO), and therefore cold radiation does not exist.

I am saying that if the net radiation an object absorbs and emits is
negative then it will cool. If it is positive it will warm. Since the
emissions are set by the objects temperature then if the incoming radiation
is from a cooler source the objects temperture will fall. I am calling that
radiation cold radiation. Dawlish say I am a fool for saying cold radiation
exists, but it would still exist under any other name.

Why not have a go at Dawlish? Get him to explain his ideas. Oh, perhaps not.
You will probably end up worse off, just like me. :-(

Cheers, Alastair.

"Metman2012" wrote in message
...
On 09/08/2015 18:24, Alastair McDonald wrote:
"Metman2012" wrote in message


The term cold radiation really only applies to the radiation when it
arrives
at a body. If it has originated from a cooler body then it is cold
radiation
and the other body will cool. If it has originated from a warmer body
then
it is hot radiation and the other body will warm.

The temperature of a body depends on the net (a word of one syllable)
radiation it absorbs and emits. There is only one source for the
emissions, the body itself, but there can be lots of sources of the
radiation it is absorbing. Obviously it is the sum of the radiation from
all those sources that will determine how the temperature of the body
itself changes. And its final temperature will be reached when that sum
equals the radiation it emits as a blackbody.

The second paragraph does make sense, but I notice that no mention is made
of hot or cold radiation.

In general, each of the several sources will be emitting either cold or hot
radiation and you need to sum them. However, an object in a room will only
have one source, the walls of the room. If the object has been there long
enough, it will be at room temperature and so the input radiation will be
neither hotter nor colder (compared with the radiation being emitted.)

But your first paragraph is less clear (partly because I have to reread it
to see what's cooling what). My understanding is that a body will cool by
itself unless it is subject to heating from another body hotter than
itself. So without the sun, the earth would be considerably cooler.

It is certainly true that without the sun the earth would be considerably
colder :-)

Howerver, if you put an object in a room its temperature will change to that
of the room. If you put it in a freezer it will cool, because the walls of
the freezer are emiting cold radiation. There is also some conduction. But
in neither case will the object cool to a temperature lower than its
surrounding.

The surroundings of the Earth is space, and that radiates at a temperature
of about -270 deg. C, - pretty cold! During the day we are warmed by the
Sun, emitting at 5,000 deg . C, but it is far away, and the radiation
ariving at Earth is about 1kW per square metre. At night the heat from the
background radiation is practically zero, so the surface of the Earth cools
pretty quickly. What prevents it from freezing over at night are the
greenhouse gases which absorb radiation from the surface during the day and
reemit it back to the surface at night.

The sun itself is cooling, or at least it would be if there were no
processes maintaining it's heat. However the fuel for these will
eventually run out and it will cool of its own accord without any nearby
cool bodies making a ha'p'orth of difference.

The Sun is actually warming and expanding. One day it will envelope the
Earth (in four billion years time) and then collapse and cool due to lack
of fuel and the cold background radiation.

If you have two bodies, one hotter than the other and they are touching,
then heat flows from the warmer to the cooler until they are the same
temperature. The cooler body doesn't reduce the temperature of the warmer
body. I believe this is because of increasing entropy. My (limited)
understanding of entropy is that everything is cooling and that eventually
(next week?) we will have the heat death of the universe. Everything will
be cool (pretty cold).

In fact the cooler body does reduce the temperature of the hotter, but only
to the average temperature of the two. The warmer body will also cause the
temperature of the cooler body to rise to the average temperature. When that
happens the entropy has increased and the two objects cannot spontaneously
become hot and cold again as that would cause the entropy to decrease, which
is forbidden by the second law of thermodynamics.

If the two objects are not touching they will exchange radiation until they
are at the same temperature, with the cold object radiating cold radiation
and the hot object radiating hot radiation.

I suspect that we might be in a war about semantics in this thread but I
don't think it's worth arguing over as nobody will be changing their
position on it (unless it gets very hot, or cold).

It not just about semantics. It is also about my reputation. It has been
destroyed by Dawlish ridiculing me for maintaining that bodies absorb
cold radiation. I have just realised that his problem is he is
misinterppreting the Second Law of Thermodynamics. He think it means
that heat only travels from hot to cold, but of course as you have pointed
out it, it states entropy increases. Hot becomes colder and cold becomes
hotter. Heat travels in both directions, just as does radiation. Thanks!

HTH,

Cheers, Alastair.

On Sunday, 9 August 2015 16:47:13 UTC+1, RedAcer wrote:
On 08/08/15 12:26, Alastair wrote:
I learnt my Kinematics at University while studying for an
engineering degree, not from some smart alec teacher. Yours wasn't
Dawlish by an chance? OK the centrifugal force is not a force field
like gravity, magnetism, etc., but the centrifugal force can be
calculated, see your link which describe it
http://scienceworld.wolfram.com/phys...ugalForce.html . That
link is proof enough for me. Strange that one can get so many hits
for centrifugal force if it does not exist.

Nonsense. If you were in a seat on a roundabout facing inwards then you
would feel a force pressing into you back forcing you to move in a circle.
Try this experiment. Take a short piece of sting with a weight on the
end and whirl it round in a vertical circle. As the weight is at the top
of the circle, let go. If there was a centrifugal force it should move
outwards. It doesnt though. It will move off horizontally at a tangent
to the circle.

Hmm, some doubtful stuff there. From the point of view of the rotating body centrifugal force certainly exists and is a useful if non-rigorous concept. When you let go of the string the body the body certainly does initially accelerate outwards at a rate determined by the previous centrifugal force.

Tuor Hughes, Warlingham, Surrey.