Why not a Python compiler?

[Grant Edwards]

So, showing of my physics ignorance: I presume then that this
means that light, say from the sun, is actually sending
particles to the earth, since the space between is mostly
vacuum? Or is there enough material in the near-vacuum of
space for propogation to occur?

They act like both waves and as particles depending on what
experiment you do. Though even if you consider them as waves
they don't depend on "jiggling" of a medium. That medium was
called the "luminiferous aether" (aka ether), and in the 19th
century experiments showed conclusively that it doesn't exist:

http://en.wikipedia.org/wiki/Luminiferous_aether

 

[castironpi]

... and Cython, when iterating over lists, for example. That's one of the
reasons why looping is so much faster in Cython than in Pyrex.

Stefan- Hide quoted text -

- Show quoted text -

There's always the Visitor pattern.

in xrange(10000).for x:
loop_of_x_at_forlike_speed()

Do identifiers get hashed once at compile/ definition-execution time,
or every time they're encountered? This could be fast...

 

[greg]

Before the famous Michelson-Morley experiment (end of s. XIX), some
physicists would have said "light propagates over ether, some kind of
matter that fills the whole space but has no measurable mass", but the
experiment failed to show any evidence of it existence.

Not just that, but it showed there was something seriously weird
about space and time -- how can light travel at the same speed
relative to *everyone*? Einstein eventually figured it out.

In hindsight, Maxwell's equations had been shouting "Relativity!"
at them all along, but nobody had seen it.

previous experiments showed
that light was not made of particles either.

Except that the photoelectric effect showed that it *is* made
of particles. Isn't the universe fun?

Until DeBroglie formulated
its hypothesis of dual nature of matter (and light): wave and particle
at the same time.

Really it's neither waves nor particles, but something else for
which there isn't a good word in everyday English. Physicists
seem to have got around that by redefining the word "particle"
to mean that new thing.

So to get back to the original topic, it doesn't really matter
whether you talk about light travelling or propagating. Take
your pick.

 

[greg]

No, even simpler: In the Star Wars galaxy, parsec is a time unit.

Yep, it's the Paradoxical Second, defined as the average length of
time it takes a person to figure out that the pilot they've
hired is feeding them a load of bull for the purpose of finding
out how long it takes them to notice they're being fed a load
of bull.

 

[Steven D'Aprano]

Really it's neither waves nor particles, but something else for which
there isn't a good word in everyday English. Physicists seem to have got
around that by redefining the word "particle" to mean that new thing.

I like the term "wavical" to describe that. We're all made of wavicals,
it's just that the wave-like fuzziness is usually too small to notice.

Unless you drink too much tequila.

 

[Steve Holden]

Not just that, but it showed there was something seriously weird
about space and time -- how can light travel at the same speed
relative to *everyone*? Einstein eventually figured it out.

In hindsight, Maxwell's equations had been shouting "Relativity!"
at them all along, but nobody had seen it.


Except that the photoelectric effect showed that it *is* made
of particles. Isn't the universe fun?


Really it's neither waves nor particles, but something else for
which there isn't a good word in everyday English. Physicists
seem to have got around that by redefining the word "particle"
to mean that new thing.

So to get back to the original topic, it doesn't really matter
whether you talk about light travelling or propagating. Take
your pick.

Well the history of physics for at least two hundred years has been a
migration away from the intuitive. In strict linguistic terms the word
"subatomic" is a fine oxymoron. I suspect it's really "turtles all the
way down".

regards
Steve

 

[Grant Edwards]

Well the history of physics for at least two hundred years has
been a migration away from the intuitive.

Starting at least as far back as Newtonian mechanics. I once
read a very interesting article about some experiments that
showed that even simple newtonian physics is counter-intuitive.
Two of the experiments I remember vividly. One of them showed
that the human brain expects objects constrained to travel in a
curved path will continue to travel in a curved path when
released. The other showed that the human brain expects that
when an object is dropped it will land on a spot immediately
below the drop point -- regardless of whether or not the ojbect
was in motion horizontally when released.

After repeated attempts at the tasks set for them in the
experiments, the subjects would learn strategies that would
work in a Newtonian world, but the initial intuitive reactions
were very non-Newtonian (regardless of how educated they were
in physics).

 

[Robert Bossy]

Starting at least as far back as Newtonian mechanics. I once
read a very interesting article about some experiments that
showed that even simple newtonian physics is counter-intuitive.
Two of the experiments I remember vividly. One of them showed
that the human brain expects objects constrained to travel in a
curved path will continue to travel in a curved path when
released. The other showed that the human brain expects that
when an object is dropped it will land on a spot immediately
below the drop point -- regardless of whether or not the ojbect
was in motion horizontally when released.

After repeated attempts at the tasks set for them in the
experiments, the subjects would learn strategies that would
work in a Newtonian world, but the initial intuitive reactions
were very non-Newtonian (regardless of how educated they were
in physics).

I'm pretty sure we can still hear educated people say that free fall
speed depends on the weight of the object without realizing it's a
double mistake.

Cheers,
RB

 

[Gabriel Genellina]

Starting at least as far back as Newtonian mechanics. I once
read a very interesting article about some experiments that
showed that even simple newtonian physics is counter-intuitive.

The inertia principle is counter-intuitive too, in a real world with
friction. Things don't just "keep going" when impulse cease to exist;
everyone knows that a running car eventually stops if the engine stops.
That it "would" keep moving at the same speed in a straight line is an
abstraction that people hardly can build from experience.

 

[Erik Max Francis]

I'm pretty sure we can still hear educated people say that free fall
speed depends on the weight of the object without realizing it's a
double mistake.

Well, you have to qualify it better than this, because what you've
stated in actually correct ... in a viscous fluid. Terminal speed is
reached when the force due to gravity is equal and opposite to the drag
force, and the drag force is dependent on the properties of the fluid,
as well as the size and mass of the object that is falling through it.

It's only when you're dealing with objects falling through vacuum that
all objects fall at the same rate, and that's because the gravitational
and inertial masses are identical.

 

[Erik Max Francis]

Well the history of physics for at least two hundred years has been a
migration away from the intuitive. In strict linguistic terms the word
"subatomic" is a fine oxymoron. I suspect it's really "turtles all the
way down".

Well, hard to say that's been a monotonic pattern. For instance,
Aristotelian physics had an awful lot of components that were fairly
bizarre, counter-intuitive, or even contrary to easily gained
experience. The notion of impetus -- where an object throw moves in a
straight line until it runs out of impetus, then falls straight down --
is clearly contrary to everyday experience of watching two people throw
a ball back and forth from a distance, since the path of the ball is
clearly curved.

 

[Jeff Schwab]

Well, you have to qualify it better than this, because what you've
stated in actually correct ... in a viscous fluid.

By definition, that's not free fall.

 

[Erik Max Francis]

By definition, that's not free fall.

In a technical physics context. But he's talking about posing the
question to generally educated people, not physicists (since physicists
wouldn't make that error). In popular parlance, "free fall" just means
falling freely without restraint (hence "free fall rides," "free
falling," etc.). And in that context, in the Earth's atmosphere, you
_will_ reach a terminal speed that is dependent on your mass (among
other things).

So you made precisely my point: The average person would not follow
that the question was being asked was about an abstract (for people
stuck on the surface of the Earth) physics principle, but rather would
understand the question to be in a context where the supposedly-wrong
statement is _actually true_.

 

[Erik Max Francis]

I've never understood that claim. You can philosophize about
anything: biology, math, weather, the stars, the moon, and so
on. I don't see how QM is any more related to philosophy than
any other field in science.

It probably comes from reading popularizations that make the really
silly attempt to join physics to Eastern philosophy and metaphysics, for
instance, garbage like _The Tao of Physics_. Modern physics can get
weird and spooky and counterintuitive, but any real connection made with
Eastern philosophy is only in the eye of the beholder.

 

[Erik Max Francis]

I like the term "wavical" to describe that. We're all made of wavicals,
it's just that the wave-like fuzziness is usually too small to notice.

It's usually spelled _wavicle_, by the way.

 

[Jeff Schwab]

In a technical physics context. But he's talking about posing the
question to generally educated people, not physicists (since physicists
wouldn't make that error). In popular parlance, "free fall" just means
falling freely without restraint (hence "free fall rides," "free
falling," etc.). And in that context, in the Earth's atmosphere, you
_will_ reach a terminal speed that is dependent on your mass (among
other things).

So you made precisely my point: The average person would not follow
that the question was being asked was about an abstract (for people
stuck on the surface of the Earth) physics principle, but rather would
understand the question to be in a context where the supposedly-wrong
statement is _actually true_.

So what's the "double mistake?" My understanding was (1) the misuse
(ok, vernacular use) of the term "free fall," and (2) the association of
weight with free-fall velocity ("If I tie an elephant's tail to a
mouse's, and drop them both into free fall, will the mouse slow the
elephant down?")

 

[Lou Pecora]

How come they spoke English?

Because they taught it to us. It's obvious.

 

[Erik Max Francis]

So what's the "double mistake?" My understanding was (1) the misuse
(ok, vernacular use) of the term "free fall," and (2) the association of
weight with free-fall velocity ("If I tie an elephant's tail to a
mouse's, and drop them both into free fall, will the mouse slow the
elephant down?")

I presume his point was that physicists have a specialized meaning of
"free fall" and, in that context, the answer is wrong.

My point was, and still is, that if this question without further
context is posed to a generally educated laymen, the supposedly wrong
answer that was given is actually _correct_. After all, surely the
technical physics meaning of "free fall" came _after_ a more common term
was in use, just as with other terms like "force" or "energy" that have
technical meanings in physics, but more abstract or general meanings in
the general parlance. "Free fall" means something specialized to
physicists, but it means something more general to non-physicists.

A lot of these kind of "gotcha" questions intended to trick even
reasonable people into demonstrating technical ignorance have precisely
the same problem: The desired technical context is not made clear and
so that the supposedly-wrong answer is not only unsurprising, but often
arguably correct. This kind of stuff is little more than a semantic
terminology game, rather than revealing any deeper concepts.

 

[Jeff Schwab]

I presume his point was that physicists have a specialized meaning of
"free fall" and, in that context, the answer is wrong.

My point was, and still is, that if this question without further
context is posed to a generally educated laymen, the supposedly wrong
answer that was given is actually _correct_. After all, surely the
technical physics meaning of "free fall" came _after_ a more common term
was in use, just as with other terms like "force" or "energy" that have
technical meanings in physics, but more abstract or general meanings in
the general parlance. "Free fall" means something specialized to
physicists, but it means something more general to non-physicists.

A lot of these kind of "gotcha" questions intended to trick even
reasonable people into demonstrating technical ignorance have precisely
the same problem: The desired technical context is not made clear and
so that the supposedly-wrong answer is not only unsurprising, but often
arguably correct. This kind of stuff is little more than a semantic
terminology game, rather than revealing any deeper concepts.

Fair enough!

 

[Grant Edwards]

So what's the "double mistake?" My understanding was (1) the misuse
(ok, vernacular use) of the term "free fall," and (2) the association
of weight with free-fall velocity ("If I tie an elephant's tail to a
mouse's, and drop them both into free fall, will the mouse slow the
elephant down?")

I presume his point was that physicists have a specialized meaning of
"free fall" and, in that context, the answer is wrong.

My point was, and still is, that if this question without further
context is posed to a generally educated laymen, the supposedly wrong
answer that was given is actually _correct_. After all,
[...]

Fair enough!

Dear me, what's Usenet coming to these days...