Thermodynamic Question

"Doink" wrote in message ...
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?

Electromagnetic radiation (EMR) is the form of pure energy moving through
space. A form of EMR infrared can transport heat from a hotter to a
cooler body.

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

The word *hot* is a qualitative way to describe matter with
a higher relative temperature. A body facing the sun grows hotter
because it absorbs radiation and its temperature is raised. It's
the body that is hot and not space.


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

Actually there is. Heat is the flow of energy between bodies
as a result of differing temperatures. The radiation is the
flow of energy from between bodies that differ in temperature
in a vacuum. Usually heat flows from a higher to lower
temperature body. If the bodies touch or are embedded in an
atmosphere then you also have convection and conduction.
You can also move heat the other way but at the expense
of work and moving *more* heat between the two bodies in question
and the rest of the universe. Thats why you put your air
conditioner in the window, and why if you stand behind your
refrigerator you feel heat.


Trying to grasp this....

So are thousands of chemistry majors and pre-engineering
students around the world.
--
Hilton Evans
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http://www.chempensoftware.com


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Well, according to the current scientific model (the Standard Model
of Quantum Mechanics), the three main forces (electromagnetism,
strong nuclear force, weak nuclear force) result from the exchange
of certain particles (bosons) between certain other particles
(fermions). What we customarily think of as "energy" is the boson
particle that carries the electromagnetic force--the photon. What we
customarily think of as "matter" is the collection of fermion
particles (electrons, groups of quarks forming protons and neutrons).
Photons have zero rest mass and thus aren't really thought of as
"matter". Radiant energy in a vacuum is a collection of photons
travelling through space. These particles are not carrying any
matter particles (fermions) with them.

Quantum dynamical particles can be considered either as particles
(discrete bits of something) in the conventional sense, or as waves.
Hence we speak of photons as having a wavelength (long-wave photons
are called "radio waves"; shorter wavelength as light, shorter still
as X-rays). The fermions also have a (very short) wavelength, and one
can "look at" something by bouncing electrons off it in the same
general manner as shining a light (bouncing photons) off something.
This is the principle of the electron microscope.

Photons of wavelengths just below the red end of the visible spectrum
(infrared), when absorbed by molecules of matter, tend to make those
molecules vibrate. This rate of vibration we call "temperature".
Infrared photons are called "radiant heat" because of this property.

Temperature is a property of matter. The "temperature" of a vacuum
could be considered to be the temperature that a piece of matter would
assume, were it placed in that location in space. So in this sense
all space has a temperature by virtue of the photons travelling
through it (even the emptiest vacuum of space is perfused with the
background radiation from the Big Bang--microwave wavelength photons
that give a temperature a tad above absolute zero).

Einstein's theory of relativity says that mass and energy are
equivalent (the famous E = mC**2). Photons, being a form of energy,
therefore have mass (but not "rest mass"--a mass when not moving
relative to the observer) and are acted on by the force of gravity.
The gravitational attraction of the Sun is strong enough to visibly
bend the paths of light photons travelling near it.

So, yes, energy can exist in the absence of matter, and energy
passing through a vacuum (photons) doesn't transport matter with it.
A piece of matter in space tends to be heated on the side facing the
sun (due to the solar photons hitting it) and cold on the other side
(where very few photons hit it). What we call "heat" is photons of
a specifc range of wavelengths that cause molecular vibration
(temperature) when absorbed.

-Paul W.

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....

Doink


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