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Frequently Asked Questions (FAQS);faqs.102



In fact this is a mistatement of the law.  Here is one generally
accepted statement of the Second Law:

      No process is possible whose *sole* result is a heat flow out of
      a system and at a given temperature and the performance of work
      with that energy.

In other words, you can't get work except by exploiting a temperature
gradient (at least, not thermodynamically - forms of potential energy
other than heat may be used - but they can also be used to make a
heat gradient).

Notice that this statement of the second law doesn't mention the word
"disorder".  In fact, the principle of entropy increase also does not,
since entropy is a thermodynamic state variable whose definition is
independent of such ill-defined terms as "disorder".

So, where does this idea that entropy is a measure of "disorder" come
from - and what does it mean anyway?  Well, the idea comes from a
mistatement of the theory of statistical mechanics.  And the meaning
is nil - since the term "disorder" has no precise scientific meaning
anyway.

In statistical mechanics, "entropy" is defined in terms of the number
of distinct energy "microstates" that are possible within the system.
This diversity of states was (and sometimes still is) informally
called "disorder" by some statistical mechanics experts when trying to
convey a feel for the subject to lay audiences.  It was never a
technical term - and never had any specific meaning in the theory.
The term "disorder" applied in this way is misleading (or, at best,
meaningless).  A room which is messy would be informally called
"disordered" by most people - even if they're ignorant (as most are)
of the entropy of the room.  The room might actually have a *higher*
entropy after it has been cleaned.

In addition the laws of thermodynamics only apply to closed systems
(which the Earth is not).  Small parts of such a closed system can
show a decrease in entropy, but only if some other part has a higher
entropy.  Entropy in the system as a whole will always increase.

For instance, when you freeze water the molecules of H2O line up in
beautifully organised crystals.  This organisation does not violate
the second law of thermodynamics because the work done by the freezer
in extracting the heat from the water has caused the total entropy of
the *universe* to rise, even though the entropy of the *water* has
decreased.

Similarly the existence of life on earth has not decreased the entropy
of the universe, so the second law has not been violated.

5.7: How could living organisms arise "by chance"?
--------------------------------------------------

This is actually a less sophisticated version of the question above.
Consider the freezing water in the example.  The wonderful arrangement
in crystals arises from the random movement of water molecules.  But
ice crystals do not require divine intervention as an explanation, and
neither does the evolution of life.

Also, consider a casino.  An honest casino makes a profit from
roulette wheels.  The result of a spin of a particular wheel is purely
random, but casinos make very predictable profits.  So in evolutionary
theory, even though the occurance of a particular mutation is random,
the overall effect of improved adaptation over time is not.

The actual origin of life is more problematical.  If you stick some
ammonia, methane and a few other simple chemicals into a jar and
subject them to ultraviolet light then after a week or two you get a
mixture of organic molecules, including amino acids (the building
blocks of protein).  So current theories propose a "primordial soup"
of dilute organic chemicals.  Somewhere a molecule happened to form
which could make copies of itself out of other molecules floating
around in the soup, and the rest is history.  However calculations
suggest that even with an immense volume of primordial soup left for
many millions of years this is wildly improbable.  Some people give
this as evidence that God triggered the start of life.  Others (e.g.
Fred Hoyle) posit extra-terrestrial origins for life.  Still others
have suggested that the assumptions about the complexity necessary for
a self-replicating molecule are wrong.

5.8: But doesn't the human body seem to be well designed?
---------------------------------------------------------

Not to me.  Consider a few pieces of the human body for a moment.  The
back for instance.  The reason we poor humans suffer so much from back
problems is that the back is actually not well designed.  And what
about human reproduction.  Can you imagine any engineer being proud of
having designed *that*?

5.9: What about the thousands of scientists who have become Creationists?
-------------------------------------------------------------------------

This outrageous claim is frequently made by creationists, but somehow
these mystery scientists are never identified.  It is claimed that
these conversions have been caused by "the evidence", but this
evidence never seems to be forthcoming either.

Even if this claim were true, it would not be a reason to become a
creationist.  The only reason for adopting creationism as a scientific
theory would be the production of convincing evidence.

Firewalking
===========

WARNING: Whatever the truth about firewalking may be, it is a
     potentially dangerous activity.  Do not attempt it without
     expert guidance.

[Please could one of the firewalkers on the net contribute a paragraph
or two for this section. PAJ]

6.1: Is firewalking possible?
-----------------------------

Yes.  It is possible to walk on a bed of burning wood without being
hurt.

6.2: Can science explain firewalking?
-------------------------------------

There are a number of theories which have been put forward to explain
firewalking.  Any or all may be the explanation for a particular
event.

o The dry wood coals used by firewalkers conduct heat very poorly.
  The coal itself may be very hot but it will not transfer that heat
  to something touching it.

o The coals are a very uneven surface, and the actual surface area of
  foot touching the coals is very small.  Hence the conduction of heat
  is even slower.

o Firewalkers do not spend very much time on the coals, and they keep
  moving.  Jan Willem Nienhuys <[e-mail]> adds that about 1
  second total contact time per foot seems on the safe side.

o Blood is a good conductor of heat.  What heat does get through is
  quickly conducted away from the soles of the feet.

o The "Leidenfrost" effect may play a part.  This occurs when a cold,
  wet object (like a foot) touches a hot, dry object (like a burning
  coal).  The water vaporises, creating a barrier of steam between the
  hot and cold objects.  Hence the two objects do not actually touch
  and evaporation from the cold object is much slower than might
  otherwise be expected.  Since steam is a relatively poor conductor
  of heat the foot does not get burned.  Jearl Walker, of Scientific
  American's "The Amateur Scientist" column, explains the Leidenfrost
  effect in the August 1977 issue; he walked across coals unharmed and
  attributes this to the Leidenfrost effect.  Other scientists believe
  that the Leidenfrost effect is unimportant in firewalking.

Some skeptics have challenged firewalkers to stand on hot metal plates
instead of coals.  Others have pointed out that making such a
challenge in the belief that the firewalker would be seriously hurt is
of dubious morality.

New Age
=======

7.1: What do New Agers believe?
-------------------------------

An awful lot, it would seem.  New Age seems to be a sort of
"roll-your-own" religion.  Some of the more common threads include:

o Divination, especially Tarot, I-Ching, and Western and Chinese
  Astrology.

o Green politics, especially the more extreme "deep green" movements.

o Flying saucers.

o "Alternative" health (see above).

o Vegetarianism.

o Pacifism.

o Conspiracy theories to explain why the rest of the world does not
  follow the same beliefs.

o Rejection of science and logic as tools for understanding the
  universe.  A reliance on feelings and intuition as guides to action.

o Pseudo-scientific jargon.  New Agers talk about "rebalancing energy
  fields" and "vibrational frequencies".  These sound vaguely
  scientific but in fact have no meaning at all.

o Eastern religions, especially "cult" religions.  Mainstream eastern
  religions such as Hinduism and Sihkism don't seem to attract New Age
  believers.  Most New Agers are actively against organised
  Christianity, but some favour heretical variants such as Gnosticism.

Not all of these are bad just because New Age people follow them, but
the rejection of logical argument as a basis for belief and action
often leads to bizarre beliefs and futile actions.  A recent example
was the vandalism of a GPS satelite while it was waiting to be
launched.  The vandals claimed that GPS was part of a nuclear
first-strike system.  In fact ICBMs use inertial guidance instead of
GPS, and have done for decades.

[Would any New Agers out there like to try summarising their beliefs
in a few paragraphs for this section? PAJ]

7.2: What is the Gaia hypothesis?
---------------------------------

There are several versions:

Religious: The planet (or the ecosphere) is aware, or at least alive,
       and tries to preserve itself.

Strong: The planet/ecosphere reacts to preserve a homeostasis; if, for
    example, global warming raises the temperature then various
    changes in the planet's biota will occur which will (in some
    period of time) lower the temperature.

Weak: Life affects the conditions of life.

No scientist would disagree with the weak version given here; at the
other extreme, the "religious" version is not science (unless we can
find signs of that awareness).

Not only can we look at the ozone hole, global warming, or human
pollution, but the presence of oxygen in the atmosphere is also due to
the presence of life.

The strong hypothesis is very much a matter of debate.  Most
scientists don't believe it, some don't think it's science, but others
feel they have good evidence.  Some point to Le Chatelier's principle
(a system in equilibrium, when disturbed, reacts to as to tend to
restore the original equilibrium).  However the ice ages suggest that
the Earth is not in long-term equilibrium.

Was Nostradamus a prophet?
--------------------------

Almost certainly not.  His supporters are very good at predicting
events after the fact, often relying on doubtful translations of the
original French to bolster their case.  But they have had absolutely
no success at predicting the future.  Up until a few years ago most
Nostradamus books were predicting a nuclear war in the next few years.

The prophecies are very general, with lots of symbolism.  It is very
easy to find connections between these symbols and almost anything
else, particularly if you allow multi-lingual puns and rhymes.

A good general reference on Nostradamus is:

    The Mask of Nostradamus
    James Randi
    Charles Scribner's Sons
    ISBN 0-684-19056-7
    BF1815.N8R35  1990

7.4: Does astrology work?
-------------------------

No.  A number of studies have been done which have failed to find any
predictive power in astrology.  Psychologists have also done studies
showing that people will agree with almost any statement made about
them provided that it is a mild compliment.

7.4.1: Could astrology work by gravity?
---------------------------------------

Some people argue that we are affected by the gravity of the planets
(just as tides are caused by the gravity of the Moon and Sun), and
that this is the connection between the motion of the planets and
mundane events on Earth.

Leaving aside the fact that astrology doesn't work (see above),
gravity is simply too weak to do this.  Gravitational force on a mass
(such as a human being) decreases with the square of the distance to
the other mass.  But the Earth is affected just as strongly by the
other mass, and accelerates slightly towards it.  So the net effect on
us is nil.  What is important is the difference in gravity between the
two sides of the mass.  This decreases with the *fourth* power of the
distance (i.e. very fast) but increases with the distance between the
near and far sides.  Hence the Moon and Sun cause tides because the
Earth is very large.  But the difference in gravity between one end of
a human and the other is absolutely miniscule.

Also, if this were the mechanism behind astrology then the most
significant thing in astrology would be the phase of the Moon, with
the time of day coming second.  The position of the planets would be
completely irrelevant because they are so much further away than the
Moon and so much smaller than the Sun.

7.4.2: What is the `Mars Effect'?
---------------------------------

French scientist Michael Gaugelin [spelling?] has discovered an apparant
correlation between the position of some planets at the time of birth
and the career followed as an adult.  The strongest correlation is
between the time when Mars rises on the day of birth and athletic
prowess.  This is the cause of considerable controversy, and anything
I say will probably be flamed.  However:

o The Effect seems to come and go depending on exactly what the sample
  population is.  Most of the controversy seems to revolve around who
  did what to which sample populations.

o `Mundane' mechanisms for the Mars Effect correlations have been
  proposed which invoke the age grouping of school athletic
  activities.

o Nothing found by Gaugelin bears any resemblance to classical
  astrology, so claims that Gaugelin has somehow "validated" astrology
  are bogus.

Strange Machines: Free Energy and Anti-Gravity
==============================================

8.1: Why don't electrical perpetual motion machines work?
---------------------------------------------------------

Electrical perpetual motion machinists usually present a machine that
causes a small battery to generate a huge amount of power.  The most
common problem here is that the "huge amount of power" was incorrectly
measured.  AC power measurements are tricky; you can't just multiply
the voltage and current, because they may be out of phase.  Thus,
measuring 10 Volts and 10 Amps could indicate anything from 0 to 100
Watts, depending on the power factor.  In addition, most AC meters
expect a sinusoidal wave; if they are given some other wave they may
be totally wrong.  A simple argument against these machines is; "If
they can provide so much energy, why do they need the battery to keep
going?"

8.2: Why don't mechanical perpetual motion machines work?
---------------------------------------------------------

Mechanical perpetual motion machines depend on rising and descending
weights.  The problem is that the amount of energy that you get out of
a descending weight is exactly the same amount that it took to raise
the weight in the first place: gravity is said to be a "conservative"
force.  So no matter what the weights do, you can't get energy out.

8.3: Why don't magnetic perpetual motion machines work?
-------------------------------------------------------

Magnetic motors have a clever arrangement of magnets which keeps the
motor rotating forever.  Not surprisingly, whenever someone tries to
build one, the motor rotates for a while and then stops -- this is
usually attributed to the magnets "wearing out".  These motors usually
rely on using magnets as low-friction bearings, meaning the "motor"
can coast for a long time, but it doesn't supply any power.  Magnetism
is like gravity; you can store potential energy and get it back, but
you can't get more energy no matter what you try.

8.4: Magnets can levitate.  Where is the energy from?
-----------------------------------------------------

Levitating magnets do not require energy, any more than something
resting on a table requires energy.  Energy is the capacity for doing
work.  Work can be measured by force times distance.  Although the
magnets are exerting a force the levitated object is stationary, so
the magnets aren't supplying any energy.

8.5: But its been patented!
---------------------------

So what?  Patent offices will not grant a patent on a "perpetual
motion machine" but if you call it a "vacuum energy device" and claim
that it gets its energy from some previously unknown source then you
can probably get a patent.  Patent offices are there to judge whether
something has been invented before, not whether it will work.

8.6: The oil companies are conspiring to suppress my invention
--------------------------------------------------------------

This is a conspiracy theory.  See the entry on these in section 0.

8.7: My machine gets its free energy from <X>
---------------------------------------------

A number of machines have been proposed which are not "perpetual
motion" machines in the sense of violating the law of conservation of
energy.  Mostly these are based on bogus science.  One inventor claims
that atoms of copper wire are being converted to energy in accordance
with Einstein's "e=mc^2".  However he fails to explain what causes
this transformation and how this energy is converted into electrical
energy rather than gamma rays.

Occasionally one sees a machine which could work in theory but would
produce very tiny amounts of energy.  For instance, one can set up a
gyroscope which always points in one direction (this is how the
gyrocompass in an aircraft works).  The earth will rotate underneath
this once every day (to an observer standing on the Earth it looks
like the gyro is rotating).  So you could attach gears and a generator
to the gyroscope and use this rotation to get electricity.  The
4,320,000:1 gearing required is left as an exercise for the student,
as is naming the source of the energy it would generate.

8.8: Can gyroscopes neutralise gravity?
---------------------------------------

Gyroscopes (or gyros) are a favorite of "lift" machine inventors
because many people have come across them and they behave rather
oddly.  However there is nothing all that mysterious about the
behaviour of gyros.  You can use Newtonian physics to explain them.
Briefly, if you imagine a bit of metal on the edge of a spinning gyro,
then to turn the gyro you have to stop the bit of metal moving in its
current direction and start it moving in another direction.  To do
this when it is moving fast you have to push it rather hard.  Nothing
about this makes the thing get any lighter (in fact to be pedantic,
the gyro gets very slightly heavier when it spins, in accordance with
Einstein's theory of relativity.)

8.9: My prototype gets lighter when I turn it on
------------------------------------------------

Weighing something which is vibrating on ordinary scales is a sure way
of getting a wrong answer.  The vibration from the machine combines
with "stiction" in the scales to give a false reading.  As a result
the weight reductions reported for such machines are always close to
the limits of accuracy of the scales used.

AIDS
====

9.1: What about these theories on AIDS?
---------------------------------------

There are two AIDS theories that often appear in sci.skeptic.  The
first is Strecker's theory that the CIA invented HIV by genetic
engineering; the second is Duesberg's theory that HIV has nothing to
do with AIDS.

9.1.1: The Mainstream Theory
----------------------------

The generally accepted theory is that AIDS is caused by the Human
Immunodeficiency Virus (HIV).  There are two different versions of
HIV: HIV-1 and HIV-2.  These viruses are believed, on the basis of
their genetic sequences, to have evolved from the Simian
Immunodeficiency Virus (SIV), with HIV-2 being much more similar to
SIV.  Several years after the initial HIV infection, the immune system
is weakened to the point where opportunistic infections occur,
resulting in the syndrome of AIDS.  A good reference for more
information on the "mainstream" view of AIDS is:

    The Science of AIDS : readings from Scientific American magazine.
    New York : W.H. Freeman, c1989.

9.1.2: Strecker's CIA Theory
----------------------------

Strecker's theory is that the CIA made HIV in the 1970's by combining
bovine leukemia virus (BLV) and sheep visna virus (OLV).  The evidence for
this theory is that the government was looking at biological warfare around
then, and that there are some structural similarities between HIV and BLV
and visna.  The evidence against this theory is:

a: HIV has been found in preserved blood samples from the 1950's.
   [Anyone have a reference for this?]
b: We didn't have the biotechnology back then for the necessary gene
   splicing.  (But maybe the CIA has secret advanced technology?)
c: The genetic sequences for HIV, SIV, BLV, and OLV are freely
   available (e.g. from genbank).  You can look at them and compare
   them yourself.  The HIV sequence is totally different from BLV and
   OLV, but is fairly similar to SIV, just as the scientists say.

Also see the question in section 0 about Conspiracy Theories.

9.1.3: Duesberg's Risk-Group Theory
-----------------------------------

Duesberg's theory is: HIV is a harmless retrovirus that may serve as a
marker for people in AIDS high-risk groups.  AIDS is not a contagious
syndrome caused by one conventional virus or microbe.  AIDS is
probably caused by conventional pathogenic factors: administration of
blood transfusions or drugs, promiscuous male homosexual activity
associated with drugs, acute parasitic infections, and malnutrition.
Drugs such as AZT promote AIDS, rather than fight it.  His theory is
explained in detail in "Human Immunodeficiency Virus and Acquired
Immunodeficiency Syndrome: Correlation but not Causation", Proc. Natl.
Acad. Sci. USA V86 pp755-764, (Feb 1989).

He claims as evidence for his theory:

a: HIV does not meet Koch's postulates for the causitive agent of an
   infectious disease.
b: The conversion rate from HIV infection to AIDS depends greatly on
   the country and risk group membership, so HIV isn't sufficient to
   cause AIDS.
c: The HIV virus is minimally active, does not seem to infect many
   cells, and is suppressed by the immune system, so how could it
   cause problems?
d: It takes between 2 and 15 years from HIV infection for AIDS to
   occur.  HIV should cause illness right away or never.
e: HIV is similar to other retroviruses that don't cause AIDS.  There
   seems to be nothing special about HIV that would cause AIDS.
f: AIDS patients suffer very different diseases in the US and Africa,
   which suggests that the cofactors are responsible, not AIDS.
g: How could two viruses, HIV-1 and HIV-2, evolve at the same time?
   It doesn't seem likely that two deadly viruses would show up
   together.

Virtually the entire scientific community considers Duesberg a flake,
although he was a respected researcher before he came out with his
theory about AIDS.  There is no suggestion that his theories are the
result of a political agenda or homophobia.

Some of the arguments against him are:

a: People who receive HIV tainted blood become HIV+ and come down with
   AIDS.  People who receive HIV-free blood don't get AIDS (unless
   they get HIV somewhere else).  Thus, it is the HIV, not the
   transfusion, that causes AIDS.
b: The risk factors (homosexuality, drug use, transfusions, etc.) have
   been around for a very long time, but AIDS doesn't show up until
   HIV shows up.  People who engage in homosexuality, drug use, etc.
   but aren't exposed to HIV don't get AIDS.  On the other hand,
   people who aren't members of "risk groups" but are exposed to HIV
   get AIDS.  Thus, it is the HIV, not the risk factors, that causes
   AIDS.
c: With a few recent exceptions, everyone with an AIDS-like immune
   deficiency tests positive for HIV.  Everyone with HIV apparently
   gets AIDS eventually, after an average of 8 years.
d: Koch's postulates are more of historical interest than practical
   use.  There are many diseases that don't satisfy the postulates.
e: It is not understood exactly how HIV causes AIDS, but a lack of
   understanding of the details isn't a reason to reject HIV.
f: A recent study matched up people in the same risk groups and found
   those with HIV got AIDS but those without HIV didn't.  The study
   was titled "HIV causes AIDS".

More information can be found in published rebuttals to Duesberg, such as in
Nature V345 pp659-660 (June 21, 1990), and in Duesberg's debate with
Blattner, Gallo, Temin, Science V241 pp514-517 (1988).


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From: [e-mail] (Barry Brumitt)
Newsgroups: rec.skydiving,news.answers
Subject: rec.skydiving FAQ (Frequently Asked Questions)
Summary: This posting contains a list of Frequently Asked Questions
    (and their answers) about skydiving, learning to skydive, and
    the newsgroup rec.skydiving. It should be read by anyone
    intersted in the sport of skydiving and before posting to
    the rec.skydivi
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Last-modfied: 1992/12/12



            Rec.Skydiving F.A.Q. Sheet
            =-=-=-=-=-=-==-=-=-=-=-=-=


    PARACHUTE : An aerodynamic deceleration device.
        (Federal Aviation Administration)


This posting constitutes a dynamic compilation of Frequently
Asked Questions concerning the sport of skydiving, related activities,
and the news group rec.skydiving. It is posted on or about the second
Monday of every month.

Additions, corrections, or suggestions can be posted or emailed to
[e-mail]. The original version was written by
[e-mail], who is currently too busy to maintain it.

First, the news group rec.skydiving is an unmoderated group for
the discussion of issues relating to sport skydiving.  It obviously
is not limited to skydiving as there are many sports that share
technology, history, common interests, and avid proponents; but these
tend to be minor distractions for the hard core jumper:-).  News or
events to be held, or post-event reviews are commonly posted, as are
questions about equipment, skills, regulations, theory, etc.  And plain
ol' reminiscing over "the good ol' days" by the old timers, and long
exuberent descriptions of newcomer's first jumps are posted here as well.

Skydiving is not just a sport, it's a lifestyle (not to be confused
with bungee jumping which is just a sport:-)

It seems there are a great many new readers every year of rec.skydiving,
many of which stumbled across it and found it interesting
but have never jumped.  After a time, they seem to always ask the same
questions.  So in an effort to promote the sport, minimize redundant
postings, and in general continue the comaraderie of fellow free spirits
here is now the "Rec.Skydiving F.A.Q. Sheet".  If your question is not
answered in this document, please feel free to post it to the net.  If
we get tired of answering it (:-),  we'll append it to the FAQ sheet.
The information disseminated in this FAQ sheet is generally related
to the sport within the United States.  However, much of the information
is applicable world wide as well.  If you need specifics for a given
geographical area, post it.  Someone from that region can then reply.

The questions are not ordered in their "asking frequency".  Instead,
I have tried to order them so as to provide the information in a more
easily understood manor.

The Most Frequently Asked Questions are:

    -.    How does one learn to skydive?
    -.    What are the physical requirements?
    -.    What does the training consist of?
    -.    How do I tell a good Drop Zone from poor one?
    -.    What if my parachute doesn't open?
    -.    How hard is the landing?
    -.    How much does it cost?
    -.    How do you breathe in freefall?