Thermodynamic Question

Can energy exist in the absence of matter? I suppose it can PASS through a
vacuum, but the energy itself would transport matter with it, right? Is it
hot in space on the side facing the sun or is the heat a result of radiation
heating the atmosphere? So, there would be radiation in space but not acual
heat?

Trying to grasp this....

Doink

Thank you! You confirm what I thought....
Radiation not convection in space. Radiation IS a particle or PUSHES a
particle?


"John Steinberg" wrote in message
...
Doink wrote:

vacuum, but the energy itself would transport matter with it, right? Is
it
hot in space on the side facing the sun or is the heat a result of
radiation
heating the atmosphere? So, there would be radiation in space but not
acual
heat?

I'll try and take a stab at a part of your question.

Here on the home planet, heat travels by convection, conduction and
radiation.

Whereas In space, only the last of the three is possible. But
there's plenty of heat in space courtesy of radiation from the sun.

Consider that in earth orbit the temperature on the sunlit side of the
planet is ~300 degrees C. Whereas on the shady side it's something
like ~-267 degrees C.

In space heat can only exist where there are heat waves. This
accounts for the enormous heat differential we experience above our own
planet.

I'm confident someone will come along to dispute and/or correct this,
but in the interim it at least serves as a jumping off point.

--
-John Steinberg
email: lid

Doink wrote:
Can energy exist in the absence of matter? I suppose it can PASS through a
vacuum, but the energy itself would transport matter with it, right? Is it
hot in space on the side facing the sun or is the heat a result of radiation
heating the atmosphere? So, there would be radiation in space but not actual
heat?


Energy
http://scienceworld.wolfram.com/physics/Energy.html

Kinetic Energy
http://scienceworld.wolfram.com/phys...ticEnergy.html

Fundamental Particles and Interactions Chart
http://particleadventure.org/particl...icle_chart.jpg

The surface of Mercury which has no atmosphere to speak of
o side facing the Sun is very very hot
o side away from the sin is very very cold

Doink wrote:
Thank you! You confirm what I thought....
Radiation not convection in space. Radiation IS a particle or PUSHES a
particle?


Radiation is either matter (like protons and electrons from the sun, for
example) or photons (again the sun provides photons in wavelengths ranging
from radio to gamma).

Doink wrote:
Can energy exist in the absence of matter?

Sure. A photon possesses energy but no mass. I'm not sure that's what
you're asking, though.

I suppose it can PASS through a vacuum, but the energy itself would
transport matter with it, right?

I'm afraid I don't quite understand what you're asking here. As Sam
pointed out, the side of Mercury facing the Sun at any time is very hot,
because it's very close to the Sun, and because Mercury rotates so slowly
that each point gets illuminated for a very long time. Putting aside the
occasional double sunset and sunrise on Mercury, each spot gets sunlight
for about one entire Mercury orbit (88 Earth days). All this happens
despite the fact that there is no matter to speak of in interplanetary
space to transfer the heat. Mercury is heated entirely through radiation;
that is, photons from the Sun impinging on Mercury's surface and heating
it.

Is it hot in space on the side facing the sun or is the heat a result
of radiation heating the atmosphere?

On the side of what, exactly? If you mean a planet like Mercury, then
it can indeed get very hot, even though it has no atmosphere. As it
absorbs heat from the Sun, it will gradually heat up. The amount of
energy it radiates back into space increases as a result. It continues
to increase until the energy it radiates into space is equal to the
energy it absorbs from the Sun. At that point, it is in thermal
equilibrium with outer space. If you were by yourself in outer space
(but in a space suit), you too would absorb heat until you reached
thermal equilibrium. I imagine space suits have to be bright in part
to avoid absorbing lots of heat.

On a planet with an atmosphere, like the Earth, things are more complex.
The Sun radiates all manner of photons, mostly visible, but with some
energy radiated in other bands of light as well. The atmosphere is
transparent to the visible radiation, so it strikes the Earth and warms
it, much as it does Mercury. As the Earth warms, it also radiates an
increasing amount of energy back into space.

However, the Earth does not radiate visible light; it is far too cool
to do that. (Good thing, too!) Instead, it radiates infra-red light.
Now, the atmosphere is not perfectly transparent to infra-red. It does
transmit some, but it blocks some, too. The energy actually radiated
out into space by the Earth is less than it would be if it had no
atmosphere, and as a result, the Earth must heat up further in order to
reach thermal equilibrium. On average the Earth is some tens of degrees
warmer because of its atmosphere than it would have been otherwise, or
so I have heard. In particular, I understand that without an atmosphere,
there would be no sizable amount of liquid water on the Earth.

By the way, I don't mean to imply that Mercury is hot enough to radiate
significantly in the visible. It isn't; it's too cool by a factor of
several times, depending on what you mean by "radiate significantly."

So, there would be radiation in space but not acual heat?

If by heat, you mean molecules in motion, then by definition, there can
be no heat without matter.

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

On Tue, 16 Nov 2004 16:26:24 -0800, "Doink" wrote:

Can energy exist in the absence of matter?

Yes.

I suppose it can PASS through a
vacuum, but the energy itself would transport matter with it, right?

No. Radiation is not the same as matter. Radiation can be seen as a transport of
particles (photons), but photons are not a state of matter.

Is it
hot in space on the side facing the sun or is the heat a result of radiation
heating the atmosphere? So, there would be radiation in space but not acual
heat?

Empty space has no temperature. Of course, there is no such thing as empty
space. The "space" in the vicinity of Earth's orbit has a temperature of about
3000F, because that is the temperature of the very thinly distributed atoms and
molecules in this space. They are so thinly distributed, however, that this
temperature has very little impact on anything among them. They cannot transport
very much energy. An object in space will be heated radiatively by the Sun, or
lose heat to space if it is shaded. I believe the equilibrium temperature around
the Earth is about 30K. In deep interstellar space, between galaxies, the
equilibrium temperature is just a little above the background temperature of the
Universe itself, 3.7K.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Tue, 16 Nov 2004 16:26:24 -0800, "Doink"
wrote:

Can energy exist in the absence of matter? I suppose it can PASS through a
vacuum, but the energy itself would transport matter with it, right? Is it
hot in space on the side facing the sun or is the heat a result of radiation
heating the atmosphere? So, there would be radiation in space but not acual
heat?

Trying to grasp this....

And the reason solar panels work on satellites without gaining weight
is?

And the reason solar panels work on buildings when the air is still
cold is?

And the messages from probes carry what matter with them when they
arrive at our listening stations?


Remove the del for email

What is Meditation?

Mark



Sam Wormley wrote:

Doink wrote:
Thank you! You confirm what I thought....
Radiation not convection in space. Radiation IS a particle or PUSHES a
particle?


Radiation is either matter (like protons and electrons from the sun, for
example) or photons (again the sun provides photons in wavelengths ranging
from radio to gamma).

Doink wrote:

Thank you! You confirm what I thought....
Radiation not convection in space. Radiation IS a particle or PUSHES a
particle?

I'll try to explain, though I'm an engineer/computer guy, not a physicist.

Radiation travels as quantum packets called photons which have energy
but no mass. They have both a particle nature (photon energy, bhavior as
particles)and a wave nature (wavelength, wave interference)(experiments
to prove either nature are successful).

Photons move at the speed of light, which is constant in all frames of
reference. Don't start getting into this much further unless you want
learn the very unintuitive but true theory of relativity (from someone
who is better than I am at explaining it).

[deleting John Steinberg's perfectly good explanation of heat transfer]


--
Pat O'Connell
[note munged EMail address]
Take nothing but pictures, Leave nothing but footprints,
Kill nothing but vandals...

In message , Doink
writes
Thank you! You confirm what I thought....
Radiation not convection in space. Radiation IS a particle or PUSHES a
particle?

Radiation carries both momentum and energy. Photons have no rest mass
and move at the speed of light. (Anything with rest mass is stuck
strictly at v c). If you enclose some space with electromagnetic
radiation or photons in it (eg light) you have energy in the volume but
no rest mass.


"John Steinberg" wrote in message
.. .
Doink wrote:

vacuum, but the energy itself would transport matter with it, right?

Not with it.

But it does exert a small force on any matter that is out there. That is
how some comets end up with two tails - one driven by the influence or
radiation pressure from the sunlight, and the other by the recent
trajectory of the comet.

Is
it
hot in space on the side facing the sun or is the heat a result of
radiation

If you put something in sunlight above the Earth's atmosphere. Sunlight
delivers about 1kW/m^2 of heating to it. The heat is a result of the
surface absorbing the energy of the sunlight making atoms vibrate until
it reaches a temperature where it radiates energy at the same rate as it
is arriving.

Temperature becomes rather poorly defined in a near perfect vacuum.

Regards,
--
Martin Brown