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Old August 6th 15, 02:52 PM posted to uk.sci.weather
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Default Cold Radiation

Dawlish,

On Page 576 of University Physics with Modern Physics, Technology Update, Thirteenth Edition (2010), which continues to set the benchmark for clarity and rigor combined with effective teaching and research-based innovation, they write:

"Radiation. Heat transfer by radiation is important in some surprising places. A premature baby in an incubator can be cooled dangerously by radiation if the walls of the incubator happened to be cold, even when the air in the incubator is warm. Some incubators regulate the temperature measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects radiate cold which cools adjects objects. The latter is difficult to demonstrate because it is more difficult to maintain a constant cold temperature than a high temperture. The latter is easy using electrical heating. However, holding a thermnometer over an object taken from a freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and admit your mistake. Cold radiation does exist.

Cheers, Alastair.


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Old August 6th 15, 03:06 PM posted to uk.sci.weather
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Default Cold Radiation

On Thursday, August 6, 2015 at 3:52:09 PM UTC+1, Alastair wrote:
Dawlish,

On Page 576 of University Physics with Modern Physics, Technology Update, Thirteenth Edition (2010), which continues to set the benchmark for clarity and rigor combined with effective teaching and research-based innovation, they write:

"Radiation. Heat transfer by radiation is important in some surprising places. A premature baby in an incubator can be cooled dangerously by radiation if the walls of the incubator happened to be cold, even when the air in the incubator is warm. Some incubators regulate the temperature measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects radiate cold which cools adjects objects. The latter is difficult to demonstrate because it is more difficult to maintain a constant cold temperature than a high temperture. The latter is easy using electrical heating. However, holding a thermnometer over an object taken from a freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and admit your mistake. Cold radiation does exist.

Cheers, Alastair.


'Cold objects radiate cold which cools adjects objects.' I knew you still believed this, despite all you were shown by many people last time you tried it.

Utter rubbish. You have totally misinterpreted the link and what you propose is physically impossible. There *cannot* be an overall transfer of cold to warm. Photons are emitted by all objects with a temperature above absolute zero, but heat will **always** move from warm to cold. 'Cold radiation' does not exist in our known physical universe.

I suggest you go back and read about the laws of thermodynamics.
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Old August 6th 15, 03:13 PM posted to uk.sci.weather
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Default Cold Radiation

On Thursday, August 6, 2015 at 3:52:09 PM UTC+1, Alastair wrote:
Dawlish,

On Page 576 of University Physics with Modern Physics, Technology Update, Thirteenth Edition (2010), which continues to set the benchmark for clarity and rigor combined with effective teaching and research-based innovation, they write:

"Radiation. Heat transfer by radiation is important in some surprising places. A premature baby in an incubator can be cooled dangerously by radiation if the walls of the incubator happened to be cold, even when the air in the incubator is warm. Some incubators regulate the temperature measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects radiate cold which cools adjects objects. The latter is difficult to demonstrate because it is more difficult to maintain a constant cold temperature than a high temperture. The latter is easy using electrical heating. However, holding a thermnometer over an object taken from a freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and admit your mistake. Cold radiation does exist.

Cheers, Alastair.


This explains it to you. You can access any number of other academic explanations. You will not find a single one which tells you that heat moves from cool to hot, unless and external energy supply is applied. Now stop this silly belief you have and don't make this proposal again.

http://theory.uwinnipeg.ca/mod_tech/node79.html
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Old August 6th 15, 03:19 PM posted to uk.sci.weather
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Default Cold Radiation

On 06/08/15 15:52, Alastair wrote:
Dawlish,

On Page 576 of University Physics with Modern Physics, Technology
Update, Thirteenth Edition (2010), which continues to set the
benchmark for clarity and rigor combined with effective teaching and
research-based innovation, they write:

"Radiation. Heat transfer by radiation is important in some
surprising places. A premature baby in an incubator can be cooled
dangerously by radiation if the walls of the incubator happened to be
cold, even when the air in the incubator is warm. Some incubators
regulate the temperature measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects
radiate cold which cools adjects objects. The latter is difficult to
demonstrate because it is more difficult to maintain a constant cold
temperature than a high temperture. The latter is easy using
electrical heating. However, holding a thermnometer over an object
taken from a freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and
admit your mistake. Cold radiation does exist.

Cheers, Alastair.


I think you are getting confused with the human feelings of hot and
cold. If you stick with the words 'higher and lower temperatures' and
use well defined objects and laws, viz black-body, black-body radiation
and Stefan-Boltzmann law, then rewrite what you are trying to say and it
may clarify things?

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Old August 6th 15, 04:32 PM posted to uk.sci.weather
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Default Cold Radiation

On Thursday, August 6, 2015 at 10:52:09 AM UTC-4, Alastair wrote:
Dawlish,

On Page 576 of University Physics with Modern Physics, Technology Update, Thirteenth Edition (2010), which continues to set the benchmark for clarity and rigor combined with effective teaching and research-based innovation, they write:

"Radiation. Heat transfer by radiation is important in some surprising places. A premature baby in an incubator can be cooled dangerously by radiation if the walls of the incubator happened to be cold, even when the air in the incubator is warm. Some incubators regulate the temperature measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects radiate cold which cools adjects objects. The latter is difficult to demonstrate because it is more difficult to maintain a constant cold temperature than a high temperture. The latter is easy using electrical heating. However, holding a thermnometer over an object taken from a freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and admit your mistake. Cold radiation does exist.

==========

It does not and cannot, in the sense that I think you are representing it. But you need to define what you mean by "cold" (see RedAcer's reply). Ypu seem just to be citing relative temperatures.

In your example of the incubator, the hypothetical baby is not cooled by cold "radiating" from the incubator wall. Instead, in a properly working incubator the baby is radiating energy and steadily emitting warmth which is radiated back equally by the incubator and the air therein.

All objects above absolute zero emit energy. But the baby may cool if an incubator wall is colder than it should be, not because the wall is "radiating cold" but because it is radiating less energy back to the baby than the baby is emitting. There is net radiation from the baby to its surroundings, and thus it cools (absent any biological processes). "A premature baby in an incubator can be cooled dangerously by radiation...": yes, by radiation *from* the baby (being greater than that towards it) is what this means - not "cold radiation" in the other direction.

And of course a thermometer will measure a lower temperature adjacent to an object that is emitting less radiation.

Stephen


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Old August 6th 15, 06:14 PM posted to uk.sci.weather
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Default Cold Radiation

On Thursday, August 6, 2015 at 4:19:35 PM UTC+1, RedAcer wrote:
On 06/08/15 15:52, Alastair wrote:
Dawlish,

On Page 576 of University Physics with Modern Physics, Technology
Update, Thirteenth Edition (2010), which continues to set the
benchmark for clarity and rigor combined with effective teaching and
research-based innovation, they write:

"Radiation. Heat transfer by radiation is important in some
surprising places. A premature baby in an incubator can be cooled
dangerously by radiation if the walls of the incubator happened to be
cold, even when the air in the incubator is warm. Some incubators
regulate the temperature measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects
radiate cold which cools adjects objects. The latter is difficult to
demonstrate because it is more difficult to maintain a constant cold
temperature than a high temperture. The latter is easy using
electrical heating. However, holding a thermnometer over an object
taken from a freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and
admit your mistake. Cold radiation does exist.

Cheers, Alastair.


I think you are getting confused with the human feelings of hot and
cold. If you stick with the words 'higher and lower temperatures' and
use well defined objects and laws, viz black-body, black-body radiation
and Stefan-Boltzmann law, then rewrite what you are trying to say and it
may clarify things?


All solid objects emit radiation based on their temperature. An ideal object which emits a Planckian spectrum is called a black body, but the radiation emitted by non-ideal bodies is often called blackbody radiation too. The term cavity radiation is also used since, a cavity produces the thermodynamic equilibrium which is required for true black-body radiation.

If you place two object at different temperatures side by side with a gap between them, then the hotter object (with a higher temperature) will radiate with a greater intensity than the cooler object (with a lower temperature, since the power they emit is determined by the Stefan-Boltzmann Law J = sT^4, where s is the Stefan Boltzmann constant 5.67 E-8 W / sq m K^4. The cooler object will warm (i.e. its temperature will rise) because it is gaining more radiation than it is losing, and the warmer object will cool because it is emitting more radiation than it is absorbing. This is an example of the First Law of Thermodynamics. Eventually both objects will acquire the temperature of their surroundings, since each of their other five faces will be exchanging heat with that.

Now are you convinced? No, I didn't expect you would be. But the clue is in the first sentence of the book that I quoted. "Heat transfer by radiation is important in some SURPRISING places." It may be surprising that cold radiation exists, but that does not stop it being true.
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Old August 6th 15, 06:17 PM posted to uk.sci.weather
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Default Cold Radiation

On Thursday, August 6, 2015 at 5:32:08 PM UTC+1, Stephen Davenport wrote:
On Thursday, August 6, 2015 at 10:52:09 AM UTC-4, Alastair wrote:


And of course a thermometer will measure a lower temperature adjacent to an object that is emitting less radiation.


Stephen,

Less radiation is colder radiation. It is being emitted from a colder object.

Cheers, Alastair.
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Old August 6th 15, 06:37 PM posted to uk.sci.weather
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Default Cold Radiation

On Thursday, August 6, 2015 at 2:17:56 PM UTC-4, Alastair wrote:



Stephen,

Less radiation is colder radiation. It is being emitted from a colder object.

========

But with respect that's not COLD radiation!

Stephen.
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Old August 6th 15, 06:43 PM posted to uk.sci.weather
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Default Cold Radiation

"Stephen Davenport" wrote in message
...
On Thursday, August 6, 2015 at 10:52:09 AM UTC-4, Alastair wrote:
Dawlish,

On Page 576 of University Physics with Modern Physics, Technology Update,
Thirteenth Edition (2010), which continues to set the benchmark for
clarity and rigor combined with effective teaching and research-based
innovation, they write:

"Radiation. Heat transfer by radiation is important in some surprising
places. A premature baby in an incubator can be cooled dangerously by
radiation if the walls of the incubator happened to be cold, even when the
air in the incubator is warm. Some incubators regulate the temperature
measuring the baby's skin ..."

Hot objects radiate heat which warms adjacent objects. Cold objects
radiate cold which cools adjects objects. The latter is difficult to
demonstrate because it is more difficult to maintain a constant cold
temperature than a high temperture. The latter is easy using electrical
heating. However, holding a thermnometer over an object taken from a
freezer will cause the temperature shown to drop.

I hope you will now realise that you are wrong, will apologise and admit
your mistake. Cold radiation does exist.

==========

It does not and cannot, in the sense that I think you are representing it.
But you need to define what you mean by "cold" (see RedAcer's reply). Ypu
seem just to be citing relative temperatures.

In your example of the incubator, the hypothetical baby is not cooled by
cold "radiating" from the incubator wall. Instead, in a properly working
incubator the baby is radiating energy and steadily emitting warmth which is
radiated back equally by the incubator and the air therein.

All objects above absolute zero emit energy. But the baby may cool if an
incubator wall is colder than it should be, not because the wall is
"radiating cold" but because it is radiating less energy back to the baby
than the baby is emitting. There is net radiation from the baby to its
surroundings, and thus it cools (absent any biological processes). "A
premature baby in an incubator can be cooled dangerously by radiation...":
yes, by radiation *from* the baby (being greater than that towards it) is
what this means - not "cold radiation" in the other direction.

And of course a thermometer will measure a lower temperature adjacent to an
object that is emitting less radiation.

Stephen


Yes, Stephen is correct. All objects above absolute zero are emitting
radiation. A thermometer in a medium at constant temperature will only read
a constant value if the amount of radiation it is emitting is exactly
balanced by that it is receiving from its surroundings, e.g. it is in
radiative equilibrium. The amount of radiation emitted by the surroundings
will depend on their temperature. If a portion of the surroundings at a
given temperature is replaced by one at a lower temperature, the amount of
radiation received by the thermometer will fall, and the indicated
temperature of the thermometer will fall until the radiation emitted by the
thermometer matches the new value coming from its surroundings, and it
regains radiative equilibrium.

--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
http://www.woksat.info/wwp.html



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Old August 6th 15, 06:45 PM posted to uk.sci.weather
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Default Cold Radiation

In message ,
Alastair writes
All solid objects emit radiation based on their temperature. An ideal
object which emits a Planckian spectrum is called a black body, but the
radiation emitted by non-ideal bodies is often called blackbody
radiation too. The term cavity radiation is also used since, a cavity
produces the thermodynamic equilibrium which is required for true
black-body radiation.

If you place two object at different temperatures side by side with a
gap between them, then the hotter object (with a higher temperature)
will radiate with a greater intensity than the cooler object (with a
lower temperature, since the power they emit is determined by the
Stefan-Boltzmann Law J = sT^4, where s is the Stefan Boltzmann constant
5.67 E-8 W / sq m K^4. The cooler object will warm (i.e. its
temperature will rise) because it is gaining more radiation than it is
losing, and the warmer object will cool because it is emitting more
radiation than it is absorbing. This is an example of the First Law of
Thermodynamics. Eventually both objects will acquire the temperature of
their surroundings, since each of their other five faces will be
exchanging heat with that.


That is all absolutely true. But it ISN'T "cold radiation". Everything
that happens is due to radiation of heat.
--
I'm not paid to implement the recognition of irony.
(Taken, with the author's permission, from a LiveJournal post)



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