Please give us your opinion about this debate on quantum mechanics

I have been arguing with another poster about physics, quantum
mechanics, whether a broken glass tumbler can spontaneously put itself
back together, and Everett's interpretation. None of us is a
physicists, and I would appreciate your critique on my claims bellow:


Neil Kelsey wrote:
Dianelos Georgoudis wrote:
Neil Kelsey wrote:
[snip]
...Now that I've gone through this, I think the glass tumbler
spontaneously reassembling DOES violate the Laws of Physics, and is
therefore impossible.

You know the "Laws of Physics" are not like the "The Bible": absolute
and everlasting.

You got that backwards.

I meant that the laws of physics simply represent our best way of
mathematical modeling our observations and are not fixed nor perfect.
Neither should they revered in any way.

Science's understanding of nature evolves as older
laws are refined or replaced by newer ones.

Take gravity, for instance. Gravity is a force of nature whether humans
exist to understand it or not, and whether our understanding of it
becomes more refined or not.

According to our best theory about gravity (namely Einstein's general
relativity) there isn't such a thing as "force of gravity". An
apple doesn't fall because of the attractive force that the mass of
the earth applies on it (as Newton's older mechanics had it), but
because earth curves space around it and this curvature makes it
accelerate. So, according to our current state of knowledge to say
"gravity is a force of nature" is erroneous. (The terminology
"the four fundamental forces of nature" is very misleading, because
gravity is included as one of these four forces and gravity is *not* a
force.)

Look: All our knowledge is made by us, humans. Therefore if X stands
for some knowledge (e.g. that "gravity is a force") it's always
unjustifiable to say "X is true whether humans exist to understand it
or not". Because if we did not exist or did not understand X, how
would *you* know that X is true? Very simply I ask you not be feel so
certain, because it's not reasonable. After all, science is *not*
about certainty; it's about the best understanding we have currently
reached.

Quantum mechanics is
currently our most tested theory and therefore the most trusted. The
law of physics that quantum mechanics describes is the current 800
pound gorilla.

Is that your opinion? It's not mine..

Not only my opinion. Maybe you'd like to check this out:
http://arxiv.org/PS_cache/quant-ph/pdf/9512/9512028.pdf

And quantum mechanics does predict that a broken glass
can spontaneously put itself back together, even though such an event
is exceedingly improbable.

I think it falls into the supernatural category (for reasons described
previously), and quantum mechanics does not allow for the supernatural,
as much as you seem to want it to.

I agree that quantum mechanics does not allow for the supernatural, but

it certainly allows for what appears to us to be deeply weird. But the
success of a scientific theory is not measured by how comfortable we
feel with it, but by how well it describes phenomena.

It is true that this event violates several
older (so-called classical) physical laws including the law of gravity
(after all the chards must fly up against the force of gravity in order
to go to their correct place), the second law of thermodynamics (as at
the spontaneous reassembly of the glass entropy will decrease), and the
conversation of energy (as energy released by the breaking of the glass
must somehow return into the system). Even so any physicist will tell
you that according to our best understanding about nature such an event
*can* happen.

Disagree. If you understood about molds and glassmaking, you would
realize that it would be impossible to hide the seams where the shards
fused back together, at LEAST at a microscopic level, and thus the
glass tumbler spontaneously reassembling into its original factory
condition is a supernatural act of "God," and is impossible. I'm sure
many physicists would agree with me, too.

I don't think that many physicists would agree with you that
according to quantum mechanics it's impossible for a broken glass
tumbler to spontaneously reassemble itself into its original condition.

You dislike the weirdness of quantum mechanics and refuse to imagine
that nature could really behave like that. If so you are in good
company: Einstein too found it impossible to believe, and famously said

"God does not play dice with the universe". Still quantum mechanics
is undoubtedly the best description of the behavior of matter we have.
If you don't agree then please state which scientific theory you
think describes matter better than quantum mechanics.

Please consider that quantum mechanics predicts tunneling
effects which *also violate the classical laws of physics* and even so
they do happen: we have observed them happening; we have even built
machines that use them in order to work.

The classical laws of physics describe the macroscopic world quite
nicely.

Classical physics cannot describe the big bang which is certainly a
macroscopic event. Nor can it describe black holes. Actually it cannot
describe a light bulb.

Quantum mechanics describes the subatomic world.

Quantum mechanics describe all behavior of matter. At larger
agglomerations of matter the predictions of quantum physics become -
in most but not all cases - similar to the predictions of classical
physics. This only means that classical physics gives a good
approximation in these cases, and therefore, as a practical matter,
applies to these cases. But it is wrong to believe that quantum
mechanical phenomena are esoteric things observed only within
complicated experiments. For example when you see the simmering colors
of an oil slick you are seeing a quantum effect. Actually when you see
the light of light bulb or even from a burning log, you are seeing a
quantum effect. Not to mention the light coming from the sun - which
is a huge nuclear reaction that also cannot be described through
classical physics.

They are two
different things.

No. On the one hand, to my knowledge, it's not possible to use
quantum mechanics to compute the orbit of Mercury, whereas general
relativity succeeds splendidly in that. On the other hand though,
it's not like physical reality is divided into two regions: one
classical and one quantum mechanical. Physical reality is coherent -
we believe that axiomatically. It's our current state of knowledge
about our physical observations that is incoherent, as our two basic
theories, quantum mechanics and general relativity, contradict each
other. Because we believe that physical reality is coherent we also
believe that there must be one coherent formalization of our
observations of it. That's why physicists try to find a unified
theory that integrates in one mathematical framework the predictions of

both quantum mechanics and general relativity. This has proven to be a
very difficult task, but I have personally little doubt that they will
succeed in the end.

We have observed subatomic particles tunneling, not
closed systems like a complete human falling up.

In physics "closed system" describes a physical system in which the
interactions with its environment are negligible. A human body or an
apple are not considered closed systems, especially while falling.

Besides, if it were
tunneling the object would not appear to "fall" up either; it would be
in one location and suddenly be in a different location. It would be
teleporting. If you teleported to a higher elevation, then you would
fall down as originally planned. But a closed system like a human is
not going to spontaneously teleport complete and whole anyway, there
isn't enough time in the universe (let alone the lifespan of the object
in question) for that to happen.

It's not a question of time, but of probability. Even if an event
predicted by quantum mechanics is very unlikely to happen in the time
scale of the universe, it may happen; it may actually happen in the
next five seconds.

Neil, I think you are very mistaken in this. I mean you cannot simply
declare "I don't agree with this" or "I am not convinced by that" or
"This is impossible" - just because you wish to hold on to a personal
view of "Laws of Physics".

I'm not, I'm actually explaining why I think you're wrong (unlike
unsupported assertions that you're making, such as "The law of physics
that quantum mechanics describes is the current 800 pound gorilla.").

Well, ok, I hope I did offer some support to that assertion by pointing

you to that link above.

I
told you why I think the glass tumbler reassembling is impossible (zero
odds). I told you why I think the objects flying up is impossible (zero
odds). I've explained why and where I disagree with you. Just because I
disagree with your interpretation of quantum mechanics doesn't mean I'm
clinging to my won interpretation. I am strictly a layman, and I read
as much as I can about the subject, relying on actual experts (which
you're not) to explain the discoveries and problems with quantum
mechanics, and do my best to understand them. And sometimes I disagree,
even with some of the experts.

Fair enough. I even agree that you can and should disagree even with
the experts if you are not convinced. Even though in most cases this is

not a wise thing to do, especially if you didn't make the effort to
understand the experts' reasoning. After all, there are
fundamentalists who feel equally entitled to disagree with the experts
who insist that the earth is more than 6010 years old. Fundamentalists
explain why they disagree: they claim that God could very well have
created the earth in 4004 bc complete with much older looking fossils.
But why God do this? To test our faith, of course - a fundamentalist
might answer.

That's dogmatism.

Dogmatism: arrogant assertion of opinions as truths. Do you want me to
recite how many sentences you've begun with "it is a well known fact"
or "It is true that" or "any physicist will tell you that?" If anyone
is being dogmatic it's you. I'm perfectly willing for an actual expert
on physics (which you're obviously not; neither am I) to correct my
misconceptions, but I won't go down without a fight.

Again, fair enough. I was lazy. So here is my understanding:

In the beginning of the twentieth century physicists observed that
elementary particles (such as photons or electrons) behaved in a way
that was contrary to what they had expected according to classical
physics. For example when they shot a photon towards the center of a
wall they observed that some of them did not strike the wall in the
center (as they should according to classical laws) but fell clearly
off-center. It turned out that how probable a photon would be observed
in a particular place could be described as a mathematical wave. You
know that a wave can interact with itself canceling itself out in some
places and in some other places increasing its latitude; you can
observe this happening if you throw a small stone into a tranquil
swimming pool and observe the wave being reflected from its walls and
fall back on itself. It turns out that's exactly how photons were
observed to behave. In other words you could shoot only one photon and
depending of the geometry of its environment (some slits here, a mirror

there) the photon would actually interfere with itself as if it were a
wave. Therefore people say, somewhat misleadingly, that matter has a
dual nature: particle and wave. In fact science doesn't know anything
about the "nature" of matter; that's a philosophical concept.
Science simply found out that particles are detected in very small
places (as if they were very small balls of matter) but that the
probability of discovering them in some particular place can be
computed by using the mathematical formula of a wave.

Now, exactly the same behavior was observed when the same experiments
were made using electrons instead of photons, even though the
wavelength in this case was much smaller and the effect much weaker.
Physicists simply found that the best way to mathematically predict the

probabilistic results of their experiments was by describing any
material particle as a mathematical wave, the so-called wavefunction.
When you shoot an electron towards the center of a wall and compute its

wavefunction, it turns out that the highest amplitude of the wave is at

the very center quickly tapering off to all sides. This describes the
fact that the electron most probably will hit the center of the wall
just as classical physics predicts, but allows for a small chance of
the electron hitting the wall off-center, as is actually observed even
though it contradicts classical physics. Actually, using this
mathematical description of the electron, physicists can calculate with

what probability an electron would even (at the absence of any force)
turn 90 degrees and hit the side walls, or even turn tail and come
right back!

Also, and this is an important point in our discussion, the amplitude
of the wavefunction is nowhere in the physical universe exactly zero.
Even outside of the room the wavefunction has some positive value, so
there is a (slight but non-zero) probability that the electron will
suddenly appear outside the room (as if it had "tunneled" through
the walls). In fact the wavefunction of the electron has a nonzero
value close to an electron detector inside a room in a university
laboratory in China. Therefore there is a small but non-zero
probability of this electron to instantaneously "tunnel" through
the entire earth and set off that electron detector in China.

Now, all particles of matter are described by their wavefunction, and
therefore any agglomeration of matter, for example an atom - or a
bullet - are also described by the wavefunctions of all their
constituent particles. So, even though it would be exceedingly
unlikely, quantum physics predicts that it is possible to shoot
somebody in a street in New York and kill a hapless Chinese scientist
in his laboratory in Peking. The probability of this event happening is

so small as to be irrelevant for all practical purposes of course, but
it is nonetheless possible according to the predictions of quantum
mechanics.

What does this all mean for the broken glass tumbler? Each material
particle inside the shards of the broken glass are described by a
wavefunction which has a non-zero amplitude in all points in space,
even though by far the highest amplitude is where the particle is most
probably observed - i.e. inside the shard on the floor. Still there
is at all times a small probability that any particle will appear in
the original place it held when it was in the glass on the table before

it fell off and broke. So, by the same measure, there is a non-zero
probability that all particles of the broken glass will at the same
time tunnel back to their original position thus spontaneously
recreating the glass the way it was before.

That's what quantum physics says and what it says is completely
compatible with our actual observations of nature. Of course, nobody
has ever observed a broken glass spontaneously reassemble itself
because, as quantum mechanics predicts, this is an exceedingly rare
event - much much much rarer than one person winning all lotteries
during 10 years, which is also an event that nobody has ever observed,
even though we all agree it's not an impossible event.

So far so good. There is really no problem with quantum mechanics
itself. Quantum mechanics simply and splendidly does what it is
supposed to do: mathematically model our observations. The weirdness of

quantum mechanics consists in the fact that it predicts surprising
phenomena. But many of these phenomena are objectively observed, so
that's that. Where things really become hairy is when scientific
realists claim that science not only describes physical observations
but actually describes physical reality. It turns out that it's very
difficult to create a conceptual model of what is really happening in
physical reality that is compatible with quantum mechanics. One thing
that many scientific realists found particularly galling is that our
observations turned out to be probabilistic. In other words performing
the same experiment of shooting an electron towards the center of a
wall many times can and does produce different results. You see, people

were used to visualize physical reality as deterministic, which implies

that the same experiment should produce the same result. For example
people were used to thinking that if you let an apple free in the air
it will *always* fall, whereas now quantum mechanics predicted that
this would not necessarily be the case.

Before continuing, I would like to make clear that most physicists (and

people in general) don't really care about what is "really"
happening, or how physical reality "really" is. If science can help
us design efficient light bulbs to light our homes most people find it
not relevant at all to know what is really happening within them.
Actually a scientist can design a better light bulb taking into account

*only* the phenomena predicted by the theory, because after all
that's what a light bulb is good for: to efficiently produce for us
the phenomenon of light. So neither the creators nor the consumers of
light bulbs need know what is really happening in them. But those
physicists who are philosophically inclined and believe in realism do
feel that it's very important to describe what is really happening,
beyond and above the practical issue of describing and controlling
phenomena. And what quantum mechanics appears to be saying about what
is really happening (for example that an electron can be pushed
off-course without any force affecting it - which is an actual, real
and common observational fact) flies against all we thought we knew
about physical reality. (Actually it's much worse than just the
absence of force: the electron behaves as if it *instantly* knows all
details about the geometry of the experimental configuration.) People
felt all nice and cozy and intellectually satisfied imagining the
physical universe as some gigantic clockwork. Non-determinism was found

to be particularly galling because it implies that nature can in
principle do whatever it wants, for example an apple left free in the
air could actually refuse to fall.

So, scientific realists (or materialists, or physicalists - all these
names describe the same philosophical metaphysical position) felt it
was imperative to find a way to describe reality in a deterministic way

which of course should be also compatible with our actual observations
as captured by the mathematical model of quantum mechanics. As it turns

out, the currently most popular deterministic interpretation of quantum

mechanics is Everett's many worlds interpretation (in short the
"multiverse"). Here is how this interpretation manages to produce a
deterministic view of physical reality which is compatible to our
non-deterministic observations of actual experimental results:

It says that every time any observation of a quantum event can have two

possible results the entire physical universe (including the observer)
is split in two exact copies except that in one copy the first result
is observed and in the second the other. In one of these created
universes the observer will observe the first possible result and in
the other the observer will observe the second possible result. When an

observer observes the first possible result it only means that he
happens to be the one who inhabits the first universe created by the
experiment - but there is a copy of the observer in the second
universe observing the other result. If the same experiment is
repeated exactly the same thing will happen (i.e. the universe will
again split in two copies), which then means that the physical reality,

according to this description, is indeed deterministic (not to mention
quite prolific).

So Everett's interpretation claims that if you shoot a photon towards
a wall, an experiment that can have a huge (but not infinite) number of

possible results, you cause yourself and the universe to split into an
equally huge number of copies, and in each one you will observe each of

the possible experimental results. Now, every time you enter a room and

switch on the lights you are actually shooting many trillions of
photons towards the walls every second, which means that you are
causing yourself as well as the entire universe to split into an even
much larger number of copies.

I feel sure that if you do not accept quantum mechanics' claim that a
broken glass can spontaneously reassemble itself (even though it is a
natural consequence of actual experimental observations), then, with
much more reason, you will not accept any description of reality that
implies that each time you switch on a light you cause a truly
gargantuan number of copies of your own body to be created. But
that's what the multiverse interpretation says. Now, Everett, as well
as all people who believe that this interpretation describes reality do

not like it any more than you or I. But they value the fact that this
description of physical reality is deterministic and is also compatible

with the predictions of quantum mechanics. What I personally find
strange it that they find it easier to believe in such a really
fantastic view of reality rather than to believe that reality is simply

non-deterministic as quantum mechanics appears to imply.

A true believer of Everett's many worlds interpretation is David
Deutsch, a physics professor at the University of Oxford, as well as a
first class researcher in the field of quantum computers. You may want
to read his book written for the general public: "The Fabric of
Reality : The Science of Parallel Universes and Its Implications" to
find out for yourself how fantastic the multiverse really is and decide

if you are willing to accept that reality could really be like that.

Any physicist will tell

you that the event of a broken glass spontaneously putting itself
together *is* possible; even Michael Gray told you so.

Look! More dogmatic statements. By the way, Michael agreed with me by
the end of that conversation, the glass tumbler wasn't going to
reassemble itself.

Actually he didn't. Here are his last words "And, for what it's
worth, I agree with you, that the chances of the proposed event
*actually* happening, within recorded history are, for all intent and
purpose, close enough to zero to be called exactly that: nil." So he
didn't really agree with you because "close enough to zero" does
not equal "zero". And that's the whole issue: a broken glass
spontaneously reassembling itself is not an impossible event according
to our current understanding of physics.

BTW that was an excellent discussion you had with Michael back then. He

knows his stuff and you speak your mind. Teresita's post that started
that thread was misunderstood though, even though she stated the
obvious: That our current knowledge that miraculous events such as the
ones described in the Bible are not strictly impossible to happen (as
they are allowed by quantum mechanics) they must still be considered
miracles - not because they break physical laws (they don't) but
because the probability of them all happening is literally miraculous.

Come to think of it, no event is truly impossible whatever our state of

scientific knowledge may say. Here is why: All the knowledge that
allows us to make predictions about what may or may not happen in the
future is based on our past experiences (simply because we don't
enjoy some miraculous access to truth and must always depend on
empirical evidence). Therefore all claims we can make about the future
are based on inductive logic. Therefore they cannot be absolutely
certain. Therefore no proposition of the form "event X is impossible
to happen" can be accepted as true with absolute confidence.

When you at that discussion compared the probability of God existing
with the probability of a broken glass spontaneously reassembling (and
saying that you think the former is much less probable than the latter)

you were exactly right in the sense that it's always a question of
probabilities. Which does not mean that therefore you must worry about
God existing, in the same way that you needn't worry about your money
in the bank spontaneously tunneling from the vault and disappearing
into outer space.

It turns out
that quantum mechanics contradicts classical laws.

Classical physics adequately describes the macroscopic world we live
in. Quantum mechanics describes the subatomic world the macroscopic
world consists of. Classical physics is inadequate to describe the
subatomic world, but it still works on another level, or we would have
missed the moon entirely when we tried to land astronauts on it.

Both Newton's mechanics and special relativity are part of the
classical laws of physics and quantum mechanics contradicts them: The
wave nature of matter, which is real because it has been observed a
zillion times, contradicts Newton's mechanics because it allows for a
particle to accelerate at the absence of forces. (Incidentally, general

relativity too contradicts Newton's mechanics in this point because
it too allows for the acceleration of matter at the absence of forces).

The tunneling effect, which is also real because it has been observed a

zillion times, contradicts special relativity's dictum that no
physical body can move faster than light. Physical laws are simply not
all nicely ordered and compatible with each as you seem to believe.

It also turns out
that quantum mechanics is strange and that it's hard to describe a
physical reality consistent with its predictions.

That's not a very clear sentence. The first part I'm okay with, quantum
mechanics IS strange. I've tried but failed to figure out the second
part.

As I explained above, people who tried to describe how a physical
reality that is compatible with quantum mechanics would look like found

it is extremely hard to do so. First because there are several equally
valid interpretations as far as observations go (i.e. are identical to
quantum mechanics' mathematical model), and second because each of
the interpretations is unacceptably fantastic for many people. Actually

when we say that quantum mechanics is "weird" we often mean
precisely that: that it is exceedingly hard to imagine what is
"really" happening that would produce the objective observations of
quantum events.

I am trying to convey to you the depth of the problem: Quantum
mechanical observations are real - we really objectively observe
them. We can even mathematically model them and discover that all the
predictions of that model fit with experimental tests up to the last
decimal place measured. The problem is that nobody after 80 years has
come up with a good description of a physical reality that would
actually produce the observations we in reality experience. It's a
mind-boggling failure of scientific realism. It's a problem for the
underlying philosophical standpoint, but each scientific realist easily

shoves the problem under the rug claiming that their own favorite
description is the correct one, and if it seems fantastic to somebody
it's only because of their weakness of imagination or lack of mental
acuity. Read Deutsch's book to see how self-assured a scientific
realist is while claiming the most fantastic things.

You don't have to
be a physicist to know this.

Another dogmatic sentence, and I'm not even sure a collie would know
this, let alone a physicist, since it's not clear what you mean. Maybe
I'm missing something.

I meant this positively. You don't really need to formally study
physics. You can learn by yourself. There is plenty of material out
there.

You can search the web and find sites that
discuss quantum mechanics. Or you can read one of the many introductory
books about quantum mechanics.

Nice try.

No - really, you should try more and deepen your grasp on physics.
Physics is really exciting stuff, and scientific knowledge is very
convincing. I am only saying you don't need to believe me or my
explanations. You can find out for yourself.

.

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