Cheating your way out of the Second Law and into Perpetuum Mobile.

[Rock Brentwood]

Is there a way to radiate entropy out into interstellar space, in
some kind of "entropy beam", in sufficient quantity as to enable
to the Earth (or Solar System) to maintain a constant or even
decreasing entropy?

[Phillip Helbig (undress to reply)]

Post by Rock Brentwood
Is there a way to radiate entropy out into interstellar space, in
some kind of "entropy beam", in sufficient quantity as to enable
to the Earth (or Solar System) to maintain a constant or even
decreasing entropy?

Although I don't think it has anything to do with the title of your
post, my guess is that that is already the case. The Earth is not a
closed system and as such there is no reason to expect its entropy to
increase. Most solar radiation is re-radiated in the infrared. Just
like a refrigerator can remain cool because that is more than
compensated by the heat produced outside of the cool space by the motor,
the huge increase in entropy in the Sun can more than offset a
decreasing entropy on Earth.

My guess is that in the traditional sense, the entropy of the Earth is
roughly constant. How that changes if one takes information content
into account is probably a different question.

[Thomas Koenig]

Post by Rock Brentwood
Is there a way to radiate entropy out into interstellar space, in
some kind of "entropy beam", in sufficient quantity as to enable
to the Earth (or Solar System) to maintain a constant or even
decreasing entropy?

Of course (at least as far as Earth is concerned).

Earth receives a stream of entropy from the sun via solar radiation
(approximately the energy of the solar radiation impacting Earth divided
by the black-body temperauter of the Sun) and emits entropy into space
via radiation, approximately the same amount of energy from the sun
divided by the temperature of Earth as a black body. Because that
temperature is much lower than that of sunlight, Earth generates
a lot of entropy.

The Second Law states that the change in entropy of any system has
to be larger than, or equal to, the sum of the entropies going
over the boundariy of that system. So yes, the Earth's entropy
could decrease, by quite a lot.

[Sylvia Else]

Post by Rock Brentwood
Is there a way to radiate entropy out into interstellar space, in
some kind of "entropy beam", in sufficient quantity as to enable
to the Earth (or Solar System) to maintain a constant or even
decreasing entropy?

No. Entropy is not similar to energy. Rather it is a measure of the
disorder in a system. It's not something that can be extracted and sent
elsewhere.

Sylvia.

[Stefan Ram]

Post by Sylvia Else
No. Entropy is not similar to energy. Rather it is a measure of the
disorder in a system. It's not something that can be extracted and sent
elsewhere.

Entropy is an extensive property of a system, similar to
momentum. As such, it /can/ be exchanged. A change dS of
entropy S is connected with a change T dS of heat energy,
where T is the temperature of the system. When entropy dS
is leaving a system, it has to go somewhere (into another
system). That's pretty much "extracted and sent elsewhere".
Such an exchanged is caused by a difference in temperature
at the boundary of two systems. The entropy will move from
the system with the higher temperature to the system with
the lower temperature.

Unlike for momentum, there is only half a conservation law
for entropy. While entropy cannot be reduced in a closed
system, it /can/ be created. When entropy is exchanged,
in the process, there might be additional entropy created.
When the temperature difference between two systems is
smaller, there is less entropy created in the exchange.

[Thomas Koenig]

Post by Sylvia Else

Post by Rock Brentwood
Is there a way to radiate entropy out into interstellar space, in
some kind of "entropy beam", in sufficient quantity as to enable
to the Earth (or Solar System) to maintain a constant or even
decreasing entropy?

No. Entropy is not similar to energy. Rather it is a measure of the
disorder in a system. It's not something that can be extracted and sent
elsewhere.

Of course you can send entropy elsewhere - any heat exchanger does so.

Transfer a heat stream Q (in W) at temperature T (in K), and you get
an entropy stream of Q/T.

Related question: How do you decrease the entropy of a glass of water?
Answer: Put it in a fridge (or empty it).