| Topic: |
Science > Physics |
| User: |
"Robert Karl Stonjek" |
| Date: |
03 Jul 2003 05:17:35 AM |
| Object: |
Article] Solar sailing 'breaks laws of physics' |
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99993895
Hunt for banned weapons goes ballistic
Forget Hans Blix, the UN and inspectors schooled in the art of
uncovering biological, chemical and nuclear agents. There is a quicker
way to prove the existence of weapons of mass destruction.
Gather the latest intelligence, decide where the weapons are stashed,
and fire a high-velocity projectile at the target. High-tech sensors
packed into the projectile will then instantly beam back confirmation
that the weapons are there.
It is a high-risk concept that raises many questions, not least its
technological feasibility and the political ructions that would follow
if such a device were ever built or used. But the US military is taking
the idea seriously, New Scientist has learned.
In 2002, in a two-page research paper commissioned by the army, experts
from the Institute for Advanced Technology at the University of Texas,
Austin, detailed real test results of a prototype projectile designed to
verify the existence of WMDs. They say such a device offers a way to
inspect for weapons without permission or cooperation.
http://www.newscientist.com/news/news.jsp?id=ns99993897
--
Kind Regards,
Robert Karl Stonjek.
.
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| User: "Mathew Orman" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 07:24:00 AM |
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"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message
news:3pTMa.550$JI4.8858@news-server.bigpond.net.au...
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99993895
Hunt for banned weapons goes ballistic
Forget Hans Blix, the UN and inspectors schooled in the art of
uncovering biological, chemical and nuclear agents. There is a quicker
way to prove the existence of weapons of mass destruction.
Gather the latest intelligence, decide where the weapons are stashed,
and fire a high-velocity projectile at the target. High-tech sensors
packed into the projectile will then instantly beam back confirmation
that the weapons are there.
It is a high-risk concept that raises many questions, not least its
technological feasibility and the political ructions that would follow
if such a device were ever built or used. But the US military is taking
the idea seriously, New Scientist has learned.
In 2002, in a two-page research paper commissioned by the army, experts
from the Institute for Advanced Technology at the University of Texas,
Austin, detailed real test results of a prototype projectile designed to
verify the existence of WMDs. They say such a device offers a way to
inspect for weapons without permission or cooperation.
http://www.newscientist.com/news/news.jsp?id=ns99993897
--
Kind Regards,
Robert Karl Stonjek.
Who cares what the scientists say!
They are at least 80 years behind the engineering technology.
Engineers know that it works and they tested it.
Newscientist is promoting fallacy at the expense of tax payers and
it is a billion dollar a year fraud!
For the hard evidence that falsifies GR, SR, QM and QED see:
www.ultra-faster-than-light.com
Sincerely,
Mathew Orman
www.ultra-faster-than-light.com
www.radio-faster-than-light.com
.
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| User: "Mathew Orman" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 08:02:59 AM |
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"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message
news:3pTMa.550$JI4.8858@news-server.bigpond.net.au...
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99993895
Hunt for banned weapons goes ballistic
Forget Hans Blix, the UN and inspectors schooled in the art of
uncovering biological, chemical and nuclear agents. There is a quicker
way to prove the existence of weapons of mass destruction.
Gather the latest intelligence, decide where the weapons are stashed,
and fire a high-velocity projectile at the target. High-tech sensors
packed into the projectile will then instantly beam back confirmation
that the weapons are there.
It is a high-risk concept that raises many questions, not least its
technological feasibility and the political ructions that would follow
if such a device were ever built or used. But the US military is taking
the idea seriously, New Scientist has learned.
In 2002, in a two-page research paper commissioned by the army, experts
from the Institute for Advanced Technology at the University of Texas,
Austin, detailed real test results of a prototype projectile designed to
verify the existence of WMDs. They say such a device offers a way to
inspect for weapons without permission or cooperation.
http://www.newscientist.com/news/news.jsp?id=ns99993897
--
Kind Regards,
Robert Karl Stonjek.
Who cares what the scientists say!
They are at least 80 years behind the engineering technology.
Engineers know that it works and they tested it.
Newscientist is promoting fallacy at the expense of tax payers and
it is a billion dollar a year fraud!
For the hard evidence that falsifies GR, SR, QM and QED see:
www.ultra-faster-than-light.com
Sincerely,
Mathew Orman
www.ultra-faster-than-light.com
www.radio-faster-than-light.com
.
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| User: "Frodo Morris" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 10:36:05 AM |
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Mathew Orman wrote:
Newscientist is promoting fallacy at the expense of tax payers and
it is a billion dollar a year fraud!
New Scientist is a magazine run for profit. Which taxes go to it? Oh
and New Scientist is a British magazine, how many dollars was that
again? Do they not trade in Sterling like everyone else?
--
FM
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| User: "Mathew Orman" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 12:27:47 PM |
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"Frodo Morris" <graham.lee@invalid.wadham.oxford.ac.uk> wrote in message
news:3F044D65.8000400@invalid.wadham.oxford.ac.uk...
Mathew Orman wrote:
Newscientist is promoting fallacy at the expense of tax payers and
it is a billion dollar a year fraud!
New Scientist is a magazine run for profit. Which taxes go to it?
Both British and American pay for government education.
Oh
and New Scientist is a British magazine, how many dollars was that
again? Do they not trade in Sterling like everyone else?
--
FM
Think a little!
Where does the fallacy comes from?
Do you think that British have their own SR, GR, QM and QED?
Do you think that Newscientist is getting the biggest profit out of Britain?
Sincerely,
Mathew Orman
www.ultra-faster-than-light.com
www.radio-faster-than-light.com
.
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| User: "Octa Ex" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
23 Jul 2003 12:55:25 AM |
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On Thu, 3 Jul 2003 15:02:59 +0200, "Mathew Orman" <orman@nospam.com>
scribed these bits:
"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message
news:3pTMa.550$JI4.8858@news-server.bigpond.net.au...
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
If the mirror does not move then it has extracted no power, so there
is not problem with a force with no movement or power.
However if the mirror does move there will be a doppler shift in the
reflected light and the entropy will have increased and temperature
decreased. The temperature of the light would be about that of the
sun surface, and its radiating into pretty cool space.
Any way the mirror is not going to be 100% reflective
so its going to absorb, and reradiate at a lower temperature any way.
.
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| User: "Douglas Eagleson" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 08:07:18 PM |
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"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message news:<3pTMa.550$JI4.8858@news-server.bigpond.net.au>...
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99993895
Hunt for banned weapons goes ballistic
Forget Hans Blix, the UN and inspectors schooled in the art of
uncovering biological, chemical and nuclear agents. There is a quicker
way to prove the existence of weapons of mass destruction.
Gather the latest intelligence, decide where the weapons are stashed,
and fire a high-velocity projectile at the target. High-tech sensors
packed into the projectile will then instantly beam back confirmation
that the weapons are there.
It is a high-risk concept that raises many questions, not least its
technological feasibility and the political ructions that would follow
if such a device were ever built or used. But the US military is taking
the idea seriously, New Scientist has learned.
In 2002, in a two-page research paper commissioned by the army, experts
from the Institute for Advanced Technology at the University of Texas,
Austin, detailed real test results of a prototype projectile designed to
verify the existence of WMDs. They say such a device offers a way to
inspect for weapons without permission or cooperation.
http://www.newscientist.com/news/news.jsp?id=ns99993897
****************************************************
A quanta and the concept of heat are cutting edge theory
questions. I never considered assigning a temperature to
the photon itself. I like physics theory where the reflection
alters the flight of the carrier of momentum.
The resulting theory is odd, but it is proven true in
experiments on earth.
So a thermodynamic idea to disprove the light's propulsive
power is more odd.
I like solar sails, cheap energy. And to idea of a mile
square sail is neat. So the engineer gets to develop
the starcraft!
And interplanetary exploration is that simple. Engineering.
Light cords of kevlar, and get a robot to weave it in space!
And then place fancy film over it with a film factory attachment
the robot carries.
So one mile square and fifty pounds mass. Little spider bots
with some poly goo canisters. Maybe a few internet
experts can figure out its exit velocity from this solar system?
I can design this so the little robots actually work.
Except my other star drive idea is neater.
Douglas Eagleson
Gaithersburg, MD USA
note: It goes faster than my heavy ship.
.
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| User: "Starblade Darksquall" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 03:36:34 PM |
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"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message news:<3pTMa.550$JI4.8858@news-server.bigpond.net.au>...
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
So maybe it absorbs some heat. Remember, it's in space, so it will
probably radiate quite a bit of energy too, since the thermal
temperature of space is particularly low. So it will end up warmer
than the space around it but cooler than the radiation, meaning it
will radiate energy outward.
I don't doubt the laws of thermodynamics, but we don't need a PERFECT
mirror, now do we? No, we don't. We just need a good one. As long as
the radiation is a lot hotter than the space region where you'll be
travelling, then there's really no problem.
Perhaps, though, someday we'll learn how to use neutrinos. They're
said not to interact with matter, but they do interact via the weak
force, and since fusion from light elements produces neutrinos,
perhaps you could learn how to absorb neutrinos using heavy elements,
but not too heavy since it would be too hard to propogate. I'm
thinking of somewhere along the mass of Iron or greater. It would
convert to an element with one more proton and electron, and one less
neutron.
Of course, I know what you're going to say. It's impossible, since the
likelyness that a neutrino will react that way is so slim, probably
outweighing the fact that neutrinos go so fast.
I'm just throwing ideas out here. I really have no idea of their
practicability or anything.
(...Starblade Riven Darksquall...)
.
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| User: "Edward Green" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
04 Jul 2003 06:59:13 PM |
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"Steve Harris" <sbharris@ix.RETICULATEDOBJECTcom.com> wrote in message news:<be26km$ddi$1@slb6.atl.mindspring.net>...
I think Gold is out to lunch.
He is retired: Is that permanently out to lunch?
Reduce the process to the
simplest possible interaction: Compton scattering. The
electron does not change temperature because an electron
does not HAVE a temperature. It's a "perfect" mirror. The
photon undergoes a wavelength shift anyway, but that's the
momentum transfer to the electron. Carnot's rule is upheld
because the photon is downshifted and gains entropy while
losing (free) energy, but this has nothing to do with the
temperature of the "mirror."
The whole business about perfect mirrors is a semantic red herring;
the argument is scholastic in flavor, rather than physical. If you
want a detailed refutation you can say that a mirror subject to recoil
-- like your Compton electron -- cannot be a "perfect" mirror as
defined.
....
.
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| User: "Edward Green" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
16 Jul 2003 01:00:10 AM |
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(Gregory L. Hansen) wrote in message news:<be5593$594$4@hood.uits.indiana.edu>...
In article <2a0cceff.0307041559.502a56af@posting.google.com>,
Edward Green <nulldev00@aol.com> wrote:
The whole business about perfect mirrors is a semantic red herring;
the argument is scholastic in flavor, rather than physical. If you
want a detailed refutation you can say that a mirror subject to recoil
-- like your Compton electron -- cannot be a "perfect" mirror as
defined.
At first I thought he was making some special point about perfect mirrors
and solar sails. But then I realized that he was just pulling it from the
same shelf as massless string and frictionless pulleys. He just did his
analysis assuming 100% reflection, the same as probably most of us here
did. The perfect mirror isn't essential to his argument, it's just a
simplifying assumption.
In other respects already covered in this thread, though, he's out to
lunch.
Oh yeah? Go back and check this material out from the first post:
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when
photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there
is
no temperature change when the photons are reflected, it is
impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any
machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
That's a mixture of direct quotation and attribution, and it certainly
sounds as if the "perfect mirror" was central to his argument.
The best that could be hoped for in salvaging some dignity from this
is that he was trying to pull a Mencken Bathtub (that's an earler
version of the Sokal, brother Gorgias :-). Inventing fictitious
almost right sounding "rules" and specious sophistical arguments ...
he's certainly making a credible attempt at a history of the bathtub,
let me tell you.
[As "hoaxes" go I always thought that Mencken's was particularly lame,
since he merely made stuff up, but not, if I recall, inherently
impossible stuff. Sokal -- and Gold -- go farther, since they spout
actual nonsense (and let's not forget those French brothers), relying
on the embarassment factor already mentioned to prevent their audience
from admitting that they don't really understand what everybody else
is pretending to understand.
A lot like the Lem story where it is discovered that _all_ the robots
on a certain robot planet, accusing each other of being muclids in
disguise, are in fact muclids in disguise.]
.
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| User: "Gregory L. Hansen" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 03:46:03 PM |
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In article <4aa861fb.0307031236.2fdbac4b@posting.google.com>,
Starblade Darksquall <Starblade13@Yahoo.com> wrote:
"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message
news:<3pTMa.550$JI4.8858@news-server.bigpond.net.au>...
Solar sailing 'breaks laws of physics'
So maybe it absorbs some heat. Remember, it's in space, so it will
probably radiate quite a bit of energy too, since the thermal
temperature of space is particularly low. So it will end up warmer
than the space around it but cooler than the radiation, meaning it
will radiate energy outward.
"A solar sail that absorbed photons would heat up within seconds, Gold
argues. The claim has been greeted with skepticism."
Idiots, all. Of course the solar sail will heat up, that's not a
controversial statement. It also doesn't imply anything about the
operation of the solar sail, so long as it doesn't turn incandescent.
I don't doubt the laws of thermodynamics, but we don't need a PERFECT
mirror, now do we? No, we don't. We just need a good one. As long as
the radiation is a lot hotter than the space region where you'll be
travelling, then there's really no problem.
For weight reasons, solar sails must be thin enough that you get to
optimizing areal density versus transmitted light. No, it won't be a
perfect mirror. It will be a pretty typical mirror, but big.
Perhaps, though, someday we'll learn how to use neutrinos. They're
said not to interact with matter, but they do interact via the weak
force, and since fusion from light elements produces neutrinos,
perhaps you could learn how to absorb neutrinos using heavy elements,
but not too heavy since it would be too hard to propogate. I'm
thinking of somewhere along the mass of Iron or greater. It would
convert to an element with one more proton and electron, and one less
neutron.
Of course, I know what you're going to say. It's impossible, since the
likelyness that a neutrino will react that way is so slim, probably
outweighing the fact that neutrinos go so fast.
I'm just throwing ideas out here. I really have no idea of their
practicability or anything.
(...Starblade Riven Darksquall...)
The solar wind will be a lot easier to exploit with a superconducting loop
that reflects the charged particles with a magnetic mirror. There are
some technological issues to sort out, but it has good potential since
mass increases as the area of a solar sail but only as the radius of a
wire loop.
--
"Is that plutonium on your gums?"
"Shut up and kiss me!"
-- Marge and Homer Simpson
.
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| User: "Uncle Al" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 04:17:27 PM |
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Starblade Darksquall wrote:
"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message news:<3pTMa.550$JI4.8858@news-server.bigpond.net.au>...
[snip]
Perhaps, though, someday we'll learn how to use neutrinos. They're
said not to interact with matter, but they do interact via the weak
force, and since fusion from light elements produces neutrinos,
perhaps you could learn how to absorb neutrinos using heavy elements,
but not too heavy since it would be too hard to propogate. I'm
thinking of somewhere along the mass of Iron or greater. It would
convert to an element with one more proton and electron, and one less
neutron.
[snip]
http://w0rli.home.att.net/youare.swf
Your grammar also sucks. Countable quantities are "fewer" not "less."
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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| User: "Al Jackson" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
04 Jul 2003 07:22:12 AM |
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I notice that Tommy Gold's paper is only published online at physics
ArXiv , which means it will likely not be submitted to a refereed
journal.
Tommy Gold has had a strange career in astrophysics. His early work
was good
physics and later he was one of the first to figure out that pulsars
were neutron stars.
But at other times he seems to go just loony toons.
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| User: "" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 05:37:01 PM |
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In article <2a0cceff.0307030715.3f5424d4@posting.google.com>, (Edward Green) writes:
"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message news:<3pTMa.550$JI4.8858@news-server.bigpond.net.au>...
Solar sailing 'breaks laws of physics'
... Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
Gold is obviously wrong.
Spectacularly wrong, in fact.
The key is that the solar sail is supposed
to work in an anisotropic radiation environment. Since an anisotropic
radiation environment is not an equilibrium environment (temperature
difference between outgoing and incoming modes of EM field), it is
clearly thermodynamically permissible to extract useful work from it.
Ture, but before we even get to this, there is conservation of
momentum. The photons change momentum on reflection, so the momentum
of the sail changes as well. This is related to what you mention
above, since obviously in an isotropic radiation environment the total
momentum of the photons is zero and there is nothing to change.
...
If you proposed to run a solar sail in an isotropic radiation
evironment, then you would be in big trouble, no matter how cleverly
you silvered, half-silvered, or matted one surface or the other. That
would be analogous to trying to ratchet work out of a heat bath.
Exactly.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
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| User: "" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
05 Jul 2003 12:42:35 AM |
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In article <2a0cceff.0307041540.e1aac32@posting.google.com>, (Edward Green) writes:
meron@cars3.uchicago.edu wrote in message news:<he2Na.51$Y4.12555@news.uchicago.edu>...
In article <2a0cceff.0307030715.3f5424d4@posting.google.com>, (Edward Green) writes:
"Robert Karl Stonjek" <stonjek@ozemail.com.au> wrote in message news:<3pTMa.550$JI4.8858@news-server.bigpond.net.au>...
Solar sailing 'breaks laws of physics'
... Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
Gold is obviously wrong.
Spectacularly wrong, in fact.
The key is that the solar sail is supposed
to work in an anisotropic radiation environment. Since an anisotropic
radiation environment is not an equilibrium environment (temperature
difference between outgoing and incoming modes of EM field), it is
clearly thermodynamically permissible to extract useful work from it.
Ture, but before we even get to this, there is conservation of
momentum. The photons change momentum on reflection, so the momentum
of the sail changes as well. This is related to what you mention
above, since obviously in an isotropic radiation environment the total
momentum of the photons is zero and there is nothing to change.
Right. Well, I demolshed his specious argument -- which makes me feel
like a clever fellow for up to 10 seconds :-) -- on its own terms.
Then we can worry about minor laws like the conservation of momentum.
Maybe he was "refuting" some version of the solar sail which was
supposed to work in deep space, in an essentially isotropic
environment. It might seem like a reasonable idea that a mirror
silvered on one side and flat black on the other would be propelled
even in isotropic radiation. Of course that _would_ violate
thermodynamics.
That's the case where Uncle Al's argument applies since this sail will
heat up and by the time it'll reach equilibrium with its surroundings,
it'll be propelled no more.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
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| User: "Ed Keane III" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 10:37:03 AM |
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Robert Karl Stonjek <stonjek@ozemail.com.au> wrote in message
news:3pTMa.550$JI4.8858@news-server.bigpond.net.au...
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99993895
Better yet try
http://www.arxiv.org/html/physics/0306050
A *perfect* mirror being one that reflects all wavelengths of light at any
angle. Gold argues that a photon reflected by such a mirror will not have a
lower temperature after being reflected and so according to the laws of
thermodynamics, specifically Carnot's rule governing heat engines, can not
impart energy to the mirror. He is saying that this means that if a solar
sail were moved by photons from the sun this would involve free energy from
nothing.
An obvious problem with this argument is that nothing is *perfect*. The
proposed sails will use metallic reflectors and they absorb energy.
Electromagnetic energy in the form of light, or radio waves, makes the
electrons in the metal vibrate. It is possible to avoid this by using
dielectric reflectors. The problem with these is that they do not reflect
well at all angles. Since this would not be an issue for a solar sail let's
say, for the sake of argument, that such a sail is possible to construct.
This still would not be a perfect mirror. For that it would need to have
infinite mass. From a classical viewpoint a perfect mirror would be so rigid
that an individual particle would not be able to vibrate so that the energy
would be reflected by the entire mirror. The quantum view would be that the
entire mirror reflects each individual photon. The imperfection of both
views is that the entire mirror must be as rigid with respect to its
surroundings (specifically the emitter) as it is to its individual
components. In fact a perfect mirror is one that reflects with virtually no
loss of energy, that loss being inversely proportional to its mass if it is
free floating.
I also think some of Gold's analysis of thermodynamics is faulty. He states
that a black body will only absorb radiation until it has reached thermal
equilibrium. While there is no net absorption of energy when at thermal
equilibrium it still absorbs radiation. The only alternative is to reflect
or to be transparent. He actually goes so far as to say that if the sail
were black instead of reflective it would work until it reaches thermal
equilibrium and then stop absorbing.
Things get any stranger when he says that the momentum of light is a scalar
and heat energy is vector quantity. He even says that the motion of a
Cooke's radiometer would spin in the opposite direction than it does if he
was wrong, the obvious reason for its spin being that there is no radiation
pressure on the mirrored side.
-Ed
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| User: "Eric Prebys" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
03 Jul 2003 01:34:10 PM |
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Robert Karl Stonjek wrote:
Solar sailing 'breaks laws of physics'
The next generation of spacecraft propulsion systems could be dead in
the water before they are even launched. A physicist is claiming that
solar sailing - the idea of using sunlight to blow spacecraft across the
solar system - is at odds with the laws of thermal physics.
Both NASA and the European Space Agency are developing solar sails and,
although never tested, the concept is quite simple. A solar sail is
essentially a giant mirror that reflects photons of sunlight back in the
direction they came from.
Although photons do not have mass, they are considered to have momentum,
so according to the law of conservation of momentum, the photon loses
some of its energy to the sail as it bounces off, giving the sail a
shove in the opposite direction.
But Thomas Gold from Cornell University in New York says the proponents
of solar sailing have forgotten about thermodynamics, the branch of
physics governing heat transfer.
Perfect mirrors
Solar sails are designed to be perfect mirrors, meaning that they
reflect all the photons that strike them. Gold argues that when photons
are reflected by a perfect mirror, they do not suffer a drop in
temperature.
That brings in a thermodynamic law called the Carnot rule, which
basically states that you never get something for nothing: if there is
no temperature change when the photons are reflected, it is impossible
to extract any free energy from them to push the sail along.
"Carnot's rule says there must be a degradation of energy in any machine
that turns out free energy," Gold says. "A mirror does not have any
degradation."
This does not mean sunlight cannot exert a force - comet tails point
away from the Sun, and are often cited as evidence in favour of solar
sails. But Gold says this is because a comet tail is not a perfect
mirror: it absorbs some of the light. In this scenario Carnot's rule
says some energy can be extracted, so long as the object absorbing the
light remains cooler than the radiation itself.
Thomas Gold is a retired astronomy professor, who has
apparently forgotten whatever physics classes he ever took.
His argument is completely wrong. Energy transfer in
full elastic E&M collisions has been demonstrated at
many energy scales.
Like any elastic collision, if one object gains
energy, the other object must lose it. What this means
in the case of a solar sail is that the reflected light
will be slightly red-shifted relative to the incident light.
This is really easy to calculate if you think about
photons, somewhat more difficult but possible if you
think about solving for a moving reflecting boundary.
Realize that if his argment were correct, not only
would Compton scattering not be possible, but those
cool little spinning globes wouldn't work either.
Read the rest at NewScientist
http://www.newscientist.com/news/news.jsp?id=ns99993895
Thanks, I'll be writing them presently.
-Eric
Hunt for banned weapons goes ballistic
Forget Hans Blix, the UN and inspectors schooled in the art of
uncovering biological, chemical and nuclear agents. There is a quicker
way to prove the existence of weapons of mass destruction.
Gather the latest intelligence, decide where the weapons are stashed,
and fire a high-velocity projectile at the target. High-tech sensors
packed into the projectile will then instantly beam back confirmation
that the weapons are there.
It is a high-risk concept that raises many questions, not least its
technological feasibility and the political ructions that would follow
if such a device were ever built or used. But the US military is taking
the idea seriously, New Scientist has learned.
In 2002, in a two-page research paper commissioned by the army, experts
from the Institute for Advanced Technology at the University of Texas,
Austin, detailed real test results of a prototype projectile designed to
verify the existence of WMDs. They say such a device offers a way to
inspect for weapons without permission or cooperation.
http://www.newscientist.com/news/news.jsp?id=ns99993897
--
Kind Regards,
Robert Karl Stonjek.
--
-------------------------------------------------------------------
Eric Prebys, Fermi National Accelerator Laboratory
Office: 630-840-8369, Email:
WWW: http://home.fnal.gov/~prebys
-------------------------------------------------------------------
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| User: "Phil Karn" |
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| Title: Re: Article] Solar sailing 'breaks laws of physics' |
15 Jul 2003 08:58:57 PM |
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Eric Prebys wrote:
Realize that if his argment were correct, not only
would Compton scattering not be possible, but those
cool little spinning globes wouldn't work either.
Those little spinning vanes in the bulb work by an entirely different
principle. The bulb isn't evacuated, so when sunlight falling on the
black side of the vanes heats the surface, the surface heats the air
adjacent to it. The air expands and spins the vanes away from their
black sides.
This force greatly exceeds the photon pressure which would tend to drive
the vanes in the opposite direction. But in a vacuum, only the photon
pressure is left so it would spin the other way.
And this is exactly what happens in a number of AMSAT (ham radio)
satellites built since the 1970s. They generally have blade turnstile
antennas, with one side of each blade painted white and the other side
black. And they do indeed spin away from their white sides.
Phil
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