Could the universe be collapsing?

[caveman1917]

That rotation does no good in pushing you across the ice
or through space. It just makes you fall over or spin. So on
the ice, you need to either be sitting down and throw the
object backward over your head with both hands (your legs
prevent you from rotating forward), or lie down on your back
and throw the object forward over your body with both hands
(your entire body prevents you from rotating backward).
Either way is pretty clumsy and inefficient. You do get to
rotate your arms, but only through a limited range, so you
can't transfer as much momentum to the object as you
could if you could swing them all the way around.

If you want to get that specific, then why don't you just push the object over the ice rather than "throw" it per se, it is frictionless ice after all.

However as i'm sure you realize, the point i was making that people that have not been exposed specifically to newtonian mechanics would not come up with this way even when they use their common sense as much as they want. Both "swimming through the air" and "making yourself sneeze" are vastly more inefficient than even using some of the clothes you're wearing for throwing/pushing away. (yes i know the sneezing wasn't your idea, but it being brought up kind of makes my point).

You also did not answer my question, i wasn't asking whether you would find a way (knowing that you know at least some physics i was sure you'd come up with something), the question i asked was "if you give this problem to the public at large, how many do you think would come up with it"?

So the question really is, is common sense by itself enough without having been exposed at least once to an analytical (mathematical) "toolbox" relevant to the problem at hand? My question was intended to show that the answer is no. So if you rely on your common sense to make a statement as to the big-bang as related to an infinite universe without having gone through the math at least once, why would you expect your common sense on that matter to provide you with more than the common sense of people never having been exposed to conservation of momentum would get them in getting of the ice?

[Jeff Root]

That rotation does no good in pushing you across the ice
or through space. It just makes you fall over or spin. So on
the ice, you need to either be sitting down and throw the
object backward over your head with both hands (your legs
prevent you from rotating forward), or lie down on your back
and throw the object forward over your body with both hands
(your entire body prevents you from rotating backward).
Either way is pretty clumsy and inefficient. You do get to
rotate your arms, but only through a limited range, so you
can't transfer as much momentum to the object as you
could if you could swing them all the way around.

If you want to get that specific, then why don't you just
push the object over the ice rather than "throw" it per se,
it is frictionless ice after all.

Partly because I was using your word "throw", and partly
because pushing an object across the ice wouldn't allow
any revolution of the object around my body at all. Just
a straight-line push. However, it does suggest using one's
legs instead of arms, and that could be a net gain, especially
if the object has a large mass. Legs are capable of providing
greater force, and could be the easiest way to push off. Lie
on your back with your legs folded over your chest and the
object at your butt, and shove off. You can even push on
your knees with your hands for additional force and speed.

However as i'm sure you realize, the point i was making that
people that have not been exposed specifically to newtonian
mechanics would not come up with this way even when they
use their common sense as much as they want.

I realized that, but I don't believe it for a second. As I said,
the idea of *completely* frictionless ice is a strange one,
and would take a bit of time for most people to comprehend.
Once they have done so, most people would see immediately
that throwing or shoving a massive object would solve their
problem, if such an object is at hand.

Both "swimming through the air" and "making yourself sneeze"
are vastly more inefficient than even using some of the clothes
you're wearing for throwing/pushing away. (yes i know the
sneezing wasn't your idea, but it being brought up kind of
makes my point).

My mass is 58 kg. Let's say I use my shoes, throwing both at
once. They have a combined mass of 0.84 kg. It's hard to
estimate how fast I could throw them, but let's say 10 m/s,
horizontally. I think that is generous. I would lie on my back
and throw them with both hands toward my feet, propelling
me backward at a speed of 0.2 m/s. If I need to move ten
meters, it would take 50 seconds to reach the edge of the ice.

It's also hard to estimate how fast paddling the air would
accelerate me, but let's say 0.01 m/s per stroke. I think that
is conservative. I would lie on my back and scoop the air to
my sides and above me, again propelling me backward. After
30 strokes I would be moving at 0.3 m/s. Each stroke takes
about 1 second, so 30 strokes would take 30 seconds, during
which time I would have moved 4.5 meters. It would take
another 18.33 seconds, coasting, to reach the edge of the ice.
Total time of 48.33 seconds, just slightly less than the time it
would take if I threw my shoes away.

You also did not answer my question, i wasn't asking whether
you would find a way (knowing that you know at least some
physics i was sure you'd come up with something), the question
i asked was "if you give this problem to the public at large, how
many do you think would come up with it"?

You didn't ask that question, which is why I didn't try to
answer it. I will, now that you ask. I'll say more than
90% of the people asked would come up with a solution of
throwing something (including air) to propel them off the
ice, given enough time to comprehend the strange condition
of completely frictionless ice, and given that they respond
seriously, not jokingly.

I'll bet you a US $100 bill against any object uniquely Belgian
other than a waffle that it will be more than 90% in a fair test.

So the question really is, is common sense by itself enough
without having been exposed at least once to an analytical
(mathematical) "toolbox" relevant to the problem at hand?
My question was intended to show that the answer is no.

It certainly didn't show that. I think common sense will
do well in this test.

So if you rely on your common sense to make a statement
as to the big-bang as related to an infinite universe without
having gone through the math at least once, why would you
expect your common sense on that matter to provide you
with more than the common sense of people never having
been exposed to conservation of momentum would get them
in getting off the ice?

Mu.

Everyone has the required experience with conservation of
momentum to know how to get off the ice. Not everyone
will think of it right away when asked, though. Given enough
time, and especially if actually on completely frictionless ice,
they would figure it out eventually, and that would usually be
pretty quick. Some things would slow them down: Thinking
about the situation they are in rather than thinking about how
to get out of it, expecting help to come along and rescue
them, or thinking about other possible methods.

Although this discussion of the measurement of common
sense will move to another thread, I will hold off on saying
anything more about my commonsense reasoning about
infinity and the Big Bang for its own thread, sometime.

-- Jeff, in Minneapolis

[Tobin Dax]

It's also hard to estimate how fast paddling the air would
accelerate me, but let's say 0.01 m/s per stroke. I think that
is conservative. I would lie on my back and scoop the air to
my sides and above me, again propelling me backward. After
30 strokes I would be moving at 0.3 m/s. Each stroke takes
about 1 second, so 30 strokes would take 30 seconds, during
which time I would have moved 4.5 meters. It would take
another 18.33 seconds, coasting, to reach the edge of the ice.
Total time of 48.33 seconds, just slightly less than the time it
would take if I threw my shoes away.

Your math is incorrect in this paragraph. Accelerating at 0.01 m/s², as you claim, will only move you 0.45 meters in 30 seconds. d = 0.5at² = 0.5*0.01*90 = 0.45 m. It would then take another 32 seconds to reach the edge of the ice.

[Jeff Root]

I calculated it differently, considering my speed to increase
by 0.01 m/s per stroke, rather than per second, but it should
amount to the same thing. I think you erred in squaring the
time. I see a figure of "90" in there which, if it is supposed
to be the square of the time (30 seconds), should be 900.

The way I figured it, in keeping with the discussion, used
common sense rather than a textbook formula. Each stroke
increases my speed by 0.01 m/s. Thirty strokes gives me
a final speed of 0.3 m/s. That took 30 seconds. Since I
accelerate uniformly my average speed must be half my
final speed, so my average speed is 0.15 m/s. Multiplying
0.15 m/s by the total time of 30 seconds gives 4.5 m.

-- Jeff, in Minneapolis

[natattack]

Just wanted to point out:

...Each stroke takes about 1 second, so 30 strokes would take 30 seconds...

So they're equivalent. And 30²=900 so you do get the same answer.

[Tobin Dax]

Oops, that was my error. I apologize, Jeff.

As natattack said, you used 0.01 m/s/stroke and 1 stroke/s, which is equivalent to 0.01 m/s/s.

[NEOWatcher]

Each successive stroke will be less efficient than the last.
As you move faster relative to the air around you, the only way to get the same thrust is if your stroke speed is increasing the same amount. In other words, you are pushing something that already has relative velocity.
I'm not sure how much that would affect the calculations though.

[Jeff Root]

It's the same as swimming through water, with different
constants. You'll coast for a while in water, and quite a
long while in air. But you will slow down, so you keep on
swimming. Unless you have an unusually large number
of feet, you can't keep on throwing shoes.

-- Jeff, in Minneapolis

[caveman1917]

I realized that, but I don't believe it for a second. As I said,
the idea of *completely* frictionless ice is a strange one,
and would take a bit of time for most people to comprehend.
Once they have done so, most people would see immediately
that throwing or shoving a massive object would solve their
problem, if such an object is at hand.

As did I, the reason i brought this one up is because i have asked it to a couple of friends (with no education in physics) some time ago to see what their answers would be. Surprisingly none of them could figure something out. Like you that was not what i expected, but it was what i got. They did however almost immediately grasp the concept of completely frictionless ice.

Don't just think that what is common sense to you is in fact "common" sense rather than intuition heavily influenced by education.

It's also hard to estimate how fast paddling the air would
accelerate me, but let's say 0.01 m/s per stroke. I think that
is conservative. I would lie on my back and scoop the air to
my sides and above me, again propelling me backward. After
30 strokes I would be moving at 0.3 m/s. Each stroke takes
about 1 second, so 30 strokes would take 30 seconds, during
which time I would have moved 4.5 meters. It would take
another 18.33 seconds, coasting, to reach the edge of the ice.
Total time of 48.33 seconds, just slightly less than the time it
would take if I threw my shoes away.

Considering your hands to be flat plates 100 square cm i'm getting a figure within the same order of magnitude as yours. So i'll agree that the air swimming does seem to be reasonable as well.

You didn't ask that question, which is why I didn't try to
answer it.

If you read back you'll see i did, but it doesn't really matter.

I will, now that you ask. I'll say more than
90% of the people asked would come up with a solution of
throwing something (including air) to propel them off the
ice, given enough time to comprehend the strange condition
of completely frictionless ice, and given that they respond
seriously, not jokingly.

That's what i thought, until i actually asked some people. The sample is of course very small, but still.

It certainly didn't show that. I think common sense will
do well in this test.

Just give it a try. You're basically relying on your common sense to conceive how well common sense would do, that's a bit circular in a test for how well common sense works.

But in any case we're circumventing the point still, i neither asked whether you think common sense would do well, that would be a bit pointless. But given that you wouldn't agree until you actually tested it, let's try another example. This is one in which i'm asking your common sense to answer, that's probably easier.

Suppose i build a huge lasso and grab onto a far-away galaxy that's moving away from us with the hubble flow. So at this moment i'm holding the galaxy still with respect to us (whereas before it was receding by the well-known hubble law). Now suppose i sever the lasso and the galaxy is again free. What will happen and why?

(we've had a couple of discussion on this forum on that specific point, so if you've already read those discussions please state so and i'll come up with a different example)

[Strange]

Don't just think that what is common sense to you is in fact "common" sense rather than intuition heavily influenced by education.

Exactly. This sidetrack started because two people tried to use their common sense (on something they have not developed a good intuition for by understanding the relevant math) and came up with very different answers. That is why common sense can't be relied on; because it isn't common.

Now, the discussion has moved way beyond common sense to basic physics to solve the problem.

[Jeff Root]

Don't just think that what is common sense to you is
in fact "common" sense rather than intuition heavily
influenced by education.

You're saying, "Don't think that A is B rather than C."
I think that C is B. Intuition is largely common sense.
Intuition which is heavily influenced by education is
largely common sense heavily influenced by education.

Common sense doesn't exist on its own. It is a result
of everything a person has learned, whether through
education or experience.

the question i asked was "if you give this problem to the
public at large, how many do you think would come up with it"?

You didn't ask that question, which is why I didn't try to
answer it.

If you read back you'll see i did, but it doesn't really matter.

The question you asked was "How many people got that right?"
I answered "I don't know."

Just give it a try. You're basically relying on your common sense
to conceive how well common sense would do, that's a bit circular
in a test for how well common sense works.

I agree, but that's my story and I'm sticking to it.

I see that when I offered the $100 bill as an incentive to show
my 90% figure to be wrong, I forgot to offer the alternative of
donating US $100 to a nonprofit charity of your choice.

But in any case we're circumventing the point still, i neither
asked whether you think common sense would do well,
that would be a bit pointless. But given that you wouldn't
agree until you actually tested it, let's try another example.
This is one in which i'm asking your common sense to
answer, that's probably easier.

Suppose i build a huge lasso and grab onto a far-away galaxy
that's moving away from us with the hubble flow. So at this
moment i'm holding the galaxy still with respect to us
(whereas before it was receding by the well-known hubble law).
Now suppose i sever the lasso and the galaxy is again free.
What will happen and why?

(we've had a couple of discussions on this forum on that
specific point, so if you've already read those discussions
please state so and i'll come up with a different example)

I was involved in at least one, and curiously, my very
last post, a few hours ago, was on the same subject.
However, I don't remember if there was an apparent
consensuus in those other discussions, or if there was,
what the consensus was, or whether I agreed with it.
I'm much too lazy to try to search for those discussions,
so I'm going to stick my neck out and depend on my
current common-sense response... if I can come up with
one. Lessee... Lasso...

After the distant galaxy was lassoed, it had a very high
speed relative to the surrounding galaxies. If the cosmic
expansion were still slowing due to gravity, the speed
relative to the galaxies *then* surrounding it would
decrease over time. With the acceleration, I guess that
speed would increase over time.

After the lasso is cut, without acceleration, the galaxy
would remain approximately motionless relative to us.
With the acceleration, I think it would begin to accelerate
away from us at the same rate as the galaxies around it,
although it would still be moving at very high speed
relative to them.

Either way, with or without acceleration, after a very long
time and travelling a very great distance, its speed would
asymptotically approach that of the galaxies around it.

-- Jeff, in Minneapolis

.

[caveman1917]

Either way, with or without acceleration, after a very long
time and travelling a very great distance, its speed would
asymptotically approach that of the galaxies around it.

You'll need to be more precise. Since we're of course considering eternally expanding universes, this means that without acceleration the expansion continuously slows down. So that statement is trivially true, because every speed of every galaxy in the universe approaches zero asymptotically. So while our lasso-galaxy does indeed approach the speed of the galaxies around it, it also approaches the speed of every other galaxy in the universe, and this is true for every galaxy (lassoed or not).

I presume that is not what you meant, so can you be more precise?

[Jeff Root]

I don't see what you think is missing.

But I don't agree that "every speed of every galaxy in the
universe approaches zero asymptotically. That is only true
if the density parameter = 1. The "speed" could approach
5 km/s/Mpc or 50 km/s/Mpc. With no acceleration.

A lassoed galaxy will asymptotically approach the speed
of the galaxies it nears, but will generally diverge more and
more from the speed of more distant galaxies. With the
acceleration, it will gradually diverge from the speed given
to it to match our galaxy, moving away from us. Without
the acceleration, it might stay pretty much motionless
relative to us practically forever, while all other galaxies
continue to move away, albeit slower and slower. Our
Local group and nearby clusters would end up being its
nearest neighbors, even if billions of light-years apart.
I suppose that then it would start falling toward us.

-- Jeff, in Minneapolis

[WayneFrancis]

So humans are incapable of coming up with correct
descriptions of things on "macro and micro scales"?

No, I never said that and it is obviously false but it is pretty obvious that the way things work at the quantum level isn't in line with our common sense view of the world.
It is also obvious that we have come up with accurate descriptions of the macro and micro scale but history has shown these descriptions are far from "common sense" because even after looking at the data various results aren't just accepted because they make sense. they are often scrutinised very heavily because they don't make sense. That is why there is the old story where a reporter asked Einstein "Is it true only 3 people understand general relativity?" and Einstein replied "Who are the other 2?" or something like that.

My point is common sense is "sound and prudent judgment based on a simple perception of the situation or facts" and often our simple perception is very misleading. Just because we can over come that simple perception is a testament to our reasoning skills. Well that is what it is like for most of us, you might see everything and think it makes perfect sense without advanced training but the rest of us are not savants in even one area forget all.

Or are you saying that we need to use intuition as well as
common sense?

Often "intuition" is the result of being exposed to something so much that it pretty much becomes hard wired. Take a goal keeper in hockey or a fire person in a fire. They'll often react before an actual event happens because they've been in situations so much that they pick up on precursors subconsciously. Take the professional goal keeper in hockey and a untrained person in the same position. They both have the same reaction speed. They both might have intuition about where the puck will be hit. But the professional is more likely to be correct.

Or are you merely saying that we need knowledge in
addition to common sense? That's where "observations
and measurements" come in. Already covered.

I'm saying knowledge can over come common sense. I can tell you even with knowledge "common sense" can override that knowledge and lead you to a wrong decision very easily.
Common sense tells many people that very small increases in carbon dioxide levels shouldn't have a dramatic effect on the climate. Even when shown data their "common sense" keeps them from believing the truth.
Also "common sense" isn't applicable across the board. What makes sense to one person may not make sense to another.

quantum locking isn't common sense. We can learn the reasoning behind it but for the average person that has never seen it the effect won't make sense.

General relativity is described by math which I suspect
nobody understands. Most of the physics, however, is
not particularly hard to understand. If it seems hard to
understand, it likely is because you don't understand it.
Once you understand it, it is pretty common-sense.


You stop using your intelligence and substitute rote
recital. Everyone does that. It's an animal thing.

-- Jeff, in Minneapolis

and that is where I say you aren't using common-sense any more.

From the Wikipedia entry on "common sense"

Humans lack any common-sense intuition of, for example, the behavior of the universe at subatomic distances [see Quantum mechanics], or of speeds approaching that of light [see Special relativity]. Often ideas that may be considered to be true by common sense are in fact false.

You can learn to work out the right answer and you can even learn to get these answers as second nature and there is the possibility that someone may even be a savant with regard to the topic and in that case it is "common sense" to them because as a savant they never needed to learn it...it is just how their brain is naturally wired.

What I'm saying is you are using the term "Common sense" differently then most of us seem to use it ... if you believe most people think like you then you have to ask why things like the Wiki doesn't reflect your description.

[WayneFrancis]

If you want to get that specific, then why don't you just push the object over the ice rather than "throw" it per se, it is frictionless ice after all.

However as i'm sure you realize, the point i was making that people that have not been exposed specifically to newtonian mechanics would not come up with this way even when they use their common sense as much as they want. Both "swimming through the air" and "making yourself sneeze" are vastly more inefficient than even using some of the clothes you're wearing for throwing/pushing away. (yes i know the sneezing wasn't your idea, but it being brought up kind of makes my point).

You also did not answer my question, i wasn't asking whether you would find a way (knowing that you know at least some physics i was sure you'd come up with something), the question i asked was "if you give this problem to the public at large, how many do you think would come up with it"?

So the question really is, is common sense by itself enough without having been exposed at least once to an analytical (mathematical) "toolbox" relevant to the problem at hand? My question was intended to show that the answer is no. So if you rely on your common sense to make a statement as to the big-bang as related to an infinite universe without having gone through the math at least once, why would you expect your common sense on that matter to provide you with more than the common sense of people never having been exposed to conservation of momentum would get them in getting of the ice?

This reminds me of a experiment that was run on a group of students graduating university. One of the questions they where asked was "Where does most of the mass of a tree come from". Most students used common sense and said the ground thinking the roots gathered it up. The students that got the answer right where exposed to the correct answer of "the CO₂ from the air. Again we are using a different definition of "common sense" then Jeff. At best he can argue that we are just arguing semantics but that is the whole point and more often then not where most people disagree with him. That said he's been right before. I agree with his definition of "causally connected" where my definition was not completely accurate.

[Jeff Root]

I think "common sense" is apt.

And I'd say ... our 5 senses and practical judgement and
intelligence is not enough to get correct results on the
macro and micro scales.

So humans are incapable of coming up with correct
descriptions of things on "macro and micro scales"?

No, I never said that and it is obviously false but ...

Of course you never said it, but it is a reasonable
interpretation of what you said, given that the person
trying to interpret what you said knows nothing about
your views except for that statement.

(I deleted a word from the quote that appears to not
belong there. I left it in previously.)

it is pretty obvious that the way things work at the
quantum level isn't in line with our common sense
view of the world.

I disagree. What I mainly disagree with is the word
"our" in that assertion. As you say later, one person's
common sense is not necessarily the same as another's!

The things that I understand about the way things
work at the quantum level are part and parcel of my
commonsense view of the world. Of course, there
are plenty of things about it that I don't understand.

The most basic fact about the way things work at the
quantum level is that they are quantized. That was a
sufficiently commonsense idea that Leucippus of Miletus
and his student, Democritus, of Abdera in Thrace,
proposed a basic version of it over 2,450 years ago.

It is also obvious that we have come up with accurate
descriptions of the macro and micro scale but history
has shown these descriptions are far from "common
sense" because even after looking at the data various
results aren't just accepted because they make sense.
They are often scrutinised very heavily because they
don't make sense. That is why there is the old story
where a reporter asked Einstein "Is it true only 3
people understand general relativity?" and Einstein
replied "Who are the other 2?" or something like that.

The story was about Arthur Eddington. The story is
that a reporter mentioned to Eddington the notion that
there were only three people who understood relativity.
Eddington was silent for a long time, and the reporter
asked if something was wrong. Eddington replied that
he was trying to think who the third person could be.

Your assertion here is that relativity is complicated and
non-obvious, so it is not commonsense. Some aspects
of relativity are more readily understood than others.
Once understood, any part of relativity -- or anything
else -- may become part of a person's common sense.

My point is common sense is "sound and prudent
judgment based on a simple perception of the situation
or facts" and often our simple perception is very
misleading. Just because we can over come that simple
perception is a testament to our reasoning skills.

It is commonsense that perceptions can be misleading.
Perceptions are useful because they so frequently are
not misleading.

Responding to your comments becomes more difficult at
this point. I'll try to continue later.

-- Jeff, in Minneapolis

[caveman1917]

A lassoed galaxy will asymptotically approach the speed
of the galaxies it nears

That is incorrect in general. Also there's ambiguity as to what "the galaxies it nears" means. Do you mean that there are some galaxies that it asymptotically approaches? If so, that is also incorrect in general.

Without the acceleration, it might stay pretty much motionless
relative to us practically forever, while all other galaxies
continue to move away, albeit slower and slower.

That is also incorrect (not just in general, in all cases). What will happen is that the galaxy starts to approach us, flies past us and then recedes from us the other side.

Whilst this is of course not a "what does Jeff know" quiz, on what basis do you expect your common sense to hold good on the question of a big bang with an infinite universe without having been exposed to that specific math, when that same common sense already fails you on the relatively simpler question of what an expanding universe actually is (ie how it behaves), even when you have been exposed to those specific discussions?

[caveman1917]

I agree with his definition of "causally connected" where my definition was not completely accurate.

The definition is that two events are causally connected iff they are seperated by a null or timelike interval, which for general curved spacetimes gets extended to "iff there exists a smooth regular timelike or null curve between the events".

[Strange]

Your assertion here is that relativity is complicated and
non-obvious, so it is not commonsense. Some aspects
of relativity are more readily understood than others.
Once understood, any part of relativity -- or anything
else -- may become part of a person's common sense.

I think what you are describing might be better termed intuition than common sense. After all, having an accurate "common sense" view of general relativity would require an intimate understanding of the Einstein field equations and a facility with tensor math. Not too "common", I suspect.

I also doubt that even someone with that level of expertise could have an intuition about all (or, even, many) situations. As there are no general analytical solutions, for many cases the only way to understand what will happen is to run complex numerical simulations. It seems unlikely that anyone could get to the same result by common sense.

[Jeff Root]

Skipping to Wayne's last post:

This reminds me of an experiment that was run on a group of
students graduating university. One of the questions they were
asked was "Where does most of the mass of a tree come from".
Most students used common sense and said the ground thinking
the roots gathered it up. The students that got the answer right
were exposed to the correct answer of "the CO2 from the air."

That really isn't the correct answer, though.

The percentage of water in a tree depends on the species, age
and size of the tree, the time of year, the time of day, weather
conditions, and the available water in the ground, but as near
as I can tell, trees are usually between 50% and 75% water by
mass during the growing season. All or nearly all of that water
comes from the ground.

Including oxygen in water, oxygen comprises the largest mass
of any element in trees. It comes from both the air and ground.
Carbon is second. It comes from the air. Hydrogen is third.
It comes from water taken from the ground.

Nitrogen is the fourth element. A few species of tree have
symbiotic bacteria in their roots which fix nitrogen that the
tree absorbs from the air. Most trees get all their nitrogen
from the ground.

All other elements come from the ground.

Now, the kicker is that trees pull huge quantities of water out
of the ground during the growing season, and release almost
all of it into the air. Trees pull 200 to 1000 kilograms of water
out of the ground for each kilogram of wood they produce.

So a far larger mass comes out of the ground than the air.

Again we are using a different definition of "common sense"
than Jeff. At best he can argue that we are just arguing
semantics but that is the whole point and more often than
not where most people disagree with him.

That may be. I get the impression that for many posters on
BAUT, the term "common sense" has a pejorative connotation.
It is denegrated as inadequate, faulty, more often wrong than
right. I do not put any of that baggage on the term. Instead,
I understand it to mean what the dictionary says: practical
judgement or intelligence; ordinary good sense. It comes
from experience and learning. An inexperienced, unlearned
brain has no common sense, nomatter how intelligent it is.

-- Jeff, in Minneapolis

[Jeff Root]

A lassoed galaxy will asymptotically approach the speed
of the galaxies it nears

That is incorrect in general. Also there's ambiguity as to
what "the galaxies it nears" means. Do you mean that there
are some galaxies that it asymptotically approaches? If so,
that is also incorrect in general.

I agree that it was ambiguous.

What I meant was that, as the galaxy goes whizzing past
all sorts of other galaxies, its speed relative to the galaxies
it is passing gradually decreases. Far off in the distance
is a bunch of galaxies that it has zero speed relative to.
Namely us. The Local Group and whatever other galaxies
we are gravitationally bound to. As time goes by, the
galaxies passing the lassoed galaxy are galaxies that were
closer and closer to us now. The speeds of these successive
galaxies relative to us, and to the lassoed galaxy, are less
and less. Nothing has to change speed for this to happen.
Every galaxy could continue moving at exactly the speed it
has right now.

Without the acceleration, it might stay pretty much motionless
relative to us practically forever, while all other galaxies
continue to move away, albeit slower and slower.

That is also incorrect (not just in general, in all cases). What
will happen is that the galaxy starts to approach us, flies past
us and then recedes from us the other side.

What did I say next? I said:

I suppose that then it would start falling toward us.

When does the galaxy start to approach us? When we are
the dominant big mass. Since we start out so far apart, the
gravitational attraction between us will be miniscule and
the acceleration vanishingly tiny. It could be long after the
last white dwarfs have grown dark that the galaxy finally
passes or collides with us. That is so very far in the future
that it seemed a bit silly to mention it as "what happens
when you sever the lasso". Basically the galaxy will just
sit there for a long, long time.

If you think the lassoed galaxy starts accelerating toward
us as soon as it is released, I'd be very interested in what
the mechanism is supposed to be, and why it doesn't start
accelerating toward us before it is released.

Whilst this is of course not a "what does Jeff know"
quiz, on what basis do you expect your common sense to
hold good on the question of a big bang with an infinite
universe without having been exposed to that specific math,
when that same common sense already fails you on the
relatively simpler question of what an expanding universe
actually is (ie how it behaves), even when you have
been exposed to those specific discussions?

I believe I have described it exactly correctly.

-- Jeff, in Minneapolis

[WayneFrancis]

Skipping to Wayne's last post:


That really isn't the correct answer, though.

The percentage of water in a tree depends on the species, age
and size of the tree, the time of year, the time of day, weather
conditions, and the available water in the ground, but as near
as I can tell, trees are usually between 50% and 75% water by
mass during the growing season. All or nearly all of that water
comes from the ground.

Including oxygen in water, oxygen comprises the largest mass
of any element in trees. It comes from both the air and ground.
Carbon is second. It comes from the air. Hydrogen is third.
It comes from water taken from the ground.

Nitrogen is the fourth element. A few species of tree have
symbiotic bacteria in their roots which fix nitrogen that the
tree absorbs from the air. Most trees get all their nitrogen
from the ground.


All other elements come from the ground.

Now, the kicker is that trees pull huge quantities of water out
of the ground during the growing season, and release almost
all of it into the air. Trees pull 200 to 1000 kilograms of water
out of the ground for each kilogram of wood they produce.

So a far larger mass comes out of the ground than the air.

Unbelievable. You are so...arg...

Yea so...they pull 20-1000kg of water over how long for each kg? It doesn't matter! You pick wood that is 50-75% water. I point to a tree that is 30-40% water. If I hand you a piece of wood. Where does most of that mass come from?

Here I've found some of what I was talking about

Here is Harvard Graduates being asked about the seasons.
http://www.youtube.com/watch?v=p0wk4qG2mIg

Here is an web page on graduates being asked about the mass of a tree.
http://blogs.msdn.com/b/larryosterma...02/686647.aspx

Here you can see a bit from a documentary
http://www.learner.org/resources/series26.html
From the description of show #2

2. Lessons From Thin Air
Just about everyone will agree that trees are made from sunlight, water, and soil the trees suck up from their roots. But the surprising truth is that trees are made from air! Trees are solar-powered machines that convert air into wood. Why is it that, despite the fact that photosynthesis is one of the most widely taught subjects in science, so few people really understand the central idea underlying this system? Starting with this question, program two explores why something taught in school can go unlearned and shows that we often teach without regard to what children actually need to know.

I'll note that a most of the students they showed did mention water but they also thought the rest came from the ground too and didn't connect photosynthesis with the mass of the tree.

One said "it doesn't seem intuitive that you could add mass taking in a gas"

What it...it shows how not only our common sense is often wrong but how even after being taught something we get answers wrong.

Here is a description of the whole process.
http://www.botany.org/planttalkingpo...o2andtrees.php

That may be. I get the impression that for many posters on
BAUT, the term "common sense" has a pejorative connotation.
It is denegrated as inadequate, faulty, more often wrong than
right. I do not put any of that baggage on the term. Instead,
I understand it to mean what the dictionary says: practical
judgement or intelligence; ordinary good sense. It comes
from experience and learning. An inexperienced, unlearned
brain has no common sense, nomatter how intelligent it is.

-- Jeff, in Minneapolis

Most people here are saying in many science topics "common sense" fails us. If all or even most of science was common sense then it all should have been documented for thousands of years. Many people still think that astronauts orbiting the Earth are weightless because they are "in space" and not because the astronauts are in constant free fall.

What we are pointing out is that most people's common sense which is based of general experience does not serve them well with many basic scientific concepts forget advanced ones. Yes people here often point out that "common sense" isn't a good source to get the right answer in science and there is a good reason for that...because "common sense" often leads to the wrong answer. The number of times I've seen ATM threads claiming that it is "common sense" that GR, SR, QM or some other mainstream science topic is wrong makes me want to cry some times.

So yes. There are trees that at times have moister content > 50% but hand most people a block of wood and most will not say that most of its mass comes from water. Common sense for most people will not have most people say that we are made up of Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, Phosphorus, etc. The fact that you can't recognise that most people will get this baffles me. I'm sure I could wrack up some infringement points by speculating on why you make many of your post like you do.

The fact that when ever someone provides an example you try to twist and distort its meaning to be the exact opposite of what was meant in order to try to make yourself look clever does you no justice. Perhaps you should take up some of these issues with the writers and producers of the documentaries above that they don't have things 100% accurate so that the whole underlying premise must be 100% wrong because you don't agree with it.

So let me do this a bit differently.

What does Google define "Common sense" as?

Good sense and sound judgment in practical matters.

"Practical matters" generally refer to something that is pragmatic

"Pragmatic"

Dealing with things sensibly and realistically in a way that is based on practical rather than theoretical considerations.

"Theoretical"

Concerned with or involving the theory of a subject or area of study rather than its practical application: "a theoretical physicist".
Based on or calculated through theory rather than experience or practice:

Good models come from theoretician and experimentalists. The experimentalists aren't using "common sense" they are running experiments and recording results. That combined with theoretical considerations give us the best answers and those 2 in combination are not the same as "common sense" in many cases.

You're trying to envelope to much under the title of common sense.

[caveman1917]

I agree that it was ambiguous.

Well i did ask you to be precise.

What I meant was that, as the galaxy goes whizzing past
all sorts of other galaxies, its speed relative to the galaxies
it is passing gradually decreases.

So which is it, the speed relative to the galaxies it is passing asymptotically decreases to zero or its speed asymptotically approaches that of the galaxies it is passing? Only one of those is correct. The distinction is mathematically subtle but important, can you using common sense see the distinction between those two?

Far off in the distance
is a bunch of galaxies that it has zero speed relative to.
Namely us. The Local Group and whatever other galaxies
we are gravitationally bound to.

That is not correct, it will not maintain zero speed relative to us.

As time goes by, the
galaxies passing the lassoed galaxy are galaxies that were
closer and closer to us now.

That is also incorrect, it will asymptotically progress in passing galaxies that are further and further from us now.

When does the galaxy start to approach us? When we are
the dominant big mass. Since we start out so far apart, the
gravitational attraction between us will be miniscule and
the acceleration vanishingly tiny. It could be long after the
last white dwarfs have grown dark that the galaxy finally
passes or collides with us. That is so very far in the future
that it seemed a bit silly to mention it as "what happens
when you sever the lasso". Basically the galaxy will just
sit there for a long, long time.

That is also incorrect, it will immediately start to approach us faster and faster, fly past us and recede from us the other side and keep receding forever.

If you think the lassoed galaxy starts accelerating toward
us as soon as it is released, I'd be very interested in what
the mechanism is supposed to be

Because the math says so. If you want a newtonian picture, because of the attraction of the sphere of mass centered on us up to the galaxy. Since the mass density constantly decreases and thus the mass in that sphere constantly decreases, it will have had a higher attraction in its inwards journey towards us than in the outwards leg of the journey, giving it some extra speed with which it will keep receding the other side.

, and why it doesn't start
accelerating toward us before it is released.

It would, unless we're forcing it not to.

I believe I have described it exactly correctly.

You have not described it exactly correctly, you have even qualitatively reached a woefully incorrect conclusion. You can hardly claim that "it will sit there still for a very long time until the universe is almost empty and then join the local cluster" is an exactly correct description of "it will immediately start moving towards us, overshoot us, and forever recede from us the other side".

Just saying "i have described it exactly correctly" does not make that so, your common sense failed you on this one. Which was to be expected since it is a counterintuitive dynamic. So why would you expect your common sense to hold in even more counterintuitive situations, such as a big bang with an infinite universe?

[Jeff Root]

Unbelievable. You are so...arg...

Thank you :-)

Yea so...they pull 20-1000kg of water over how long for
each kg? It doesn't matter!

It would vary from species to species, growing conditions,
and so forth, but I agree it doesn't matter. :-)

You pick wood that is 50-75% water. I point to a tree
that is 30-40% water.

That wood certainly did not come from that particular tree.
Wood generally has a lower water content than the tree as
a whole. A tree containing only 30-40% water is either
dormant, dead, or dying. It would either have lost its leaves
or the leaves would have shriveled up so severely that the
tree probably could not recover.

If I hand you a piece of wood. Where does most of that
mass come from?

If it has been dried, as wood for human use always is,
most of its mass came from the air. If it has not been
dried, then the majority of its mass may have come from
either the air or the ground, depending on whether it is
heartwood or sapwood, whether it was taken from a
growing tree or a dormant one, and so forth.

Here I've found some of what I was talking about

Here is Harvard Graduates being asked about the seasons.
http://www.youtube.com/watch?v=p0wk4qG2mIg

Here is an web page on graduates being asked about the
mass of a tree.
http://blogs.msdn.com/b/larryosterma...02/686647.aspx

Here you can see a bit from a documentary
http://www.learner.org/resources/series26.html
From the description of show #2

2. Lessons From Thin Air
Just about everyone will agree that trees are made from
sunlight, water, and soil the trees suck up from their roots.
But the surprising truth is that trees are made from air!
Trees are solar-powered machines that convert air into
wood. Why is it that, despite the fact that photosynthesis
is one of the most widely taught subjects in science, so
few people really understand the central idea underlying
this system? Starting with this question, program two
explores why something taught in school can go unlearned
and shows that we often teach without regard to what
children actually need to know.

I'll note that a most of the students they showed did
mention water but they also thought the rest came from
the ground too and didn't connect photosynthesis with the
mass of the tree.

One said "it doesn't seem intuitive that you could add
mass taking in a gas"

Is that from the video? At 56 minutes, it probably would
take over a day for me to download.

What it...it shows how not only our common sense is
often wrong but how even after being taught something
we get answers wrong.

The video shows that? Could be. The blog pages don't.
The blogger tried to, and the comments are interesting.
But they don't demonstrate the accuracy or inaccuracy of
common sense.

That may be. I get the impression that for many posters on
BAUT, the term "common sense" has a pejorative connotation.
It is denegrated as inadequate, faulty, more often wrong than
right. I do not put any of that baggage on the term. Instead,
I understand it to mean what the dictionary says: practical
judgement or intelligence; ordinary good sense. It comes
from experience and learning. An inexperienced, unlearned
brain has no common sense, nomatter how intelligent it is.

Most people here are saying in many science topics "common
sense" fails us.

Yes. That is just wrong. Decades ago when quantum
mechancs was a new thing, the people who were trying
to explain it to others told them that the rules of quantum
mechanics defy common sense. The students accepted
that, since for them, at the time, it was true. The rules
of quantum mechanics defied the common sense of those
students at that time. But once they understood the rules,
it was no longer true. Their common sense grew to include
the new rules. But they believed what they had been told:
that common sense was inadequate. So they perpetuated
the myth, and interpreted common sense to be something
which remains fixed and cannot grow. Nothing could be
further from the truth. Common sense is totally dependant
on learning. It starts at zero with the innate ability of an
intelligent mind to learn, and grows from there.

If all or even most of science was common sense then it
all should have been documented for thousands of years.

That's amusing.

A baby has innate ability to grasp things and put them in
its mouth. It has no common sense. It has no ability to
discern what will be a good thing to put in its mouth and
what will be a bad thing. It has to learn common sense.
People have to learn common sense. They have to learn
how things work in order to have common sense about
how things work. Science is a methodcal process for
discovering how things work. It is common sense applied
to observations and measurements, which creates new
knowledge and new common sense which did not exist
before.

Many people still think that astronauts orbiting the Earth
are weightless because they are "in space" and not
because the astronauts are in constant free fall.

What we are pointing out is that most people's common
sense which is based on general experience does not
serve them well with many basic scientific concepts forget
advanced ones.

Yes, I know that is what you are saying, and I think you
are more wrong about it than right. There certainly is a
large measure of truth in it, just as there is a large
measure of carbon in a tree.

I think what is going on here is that you are looking
at the differences rather than the similarities. You see
differences between what common sense would say and
what closer inspection and analysis show, and say that
common sense fails. But most of the time common sense
works just fine. It is when it fails that it gets noticed
and commented on.

So yes. There are trees that at times have moisture
content > 50% but hand most people a block of wood
and most will not say that most of its mass comes
from water.

The question was about trees, not wood. Wood that
people use, whether for building and making things or
for burning, is always dried.

A tree that has a water content of 50% or less is either
dormant, becoming dormant, dead, or dying.

Common sense for most people will not have most
people say that we are made up of Oxygen, Carbon,
Hydrogen, Nitrogen, Calcium, Phosphorus, etc.

It won't? If you ask people what elements humans
are made of, most won't come up with a list similar
to yours? Or what question are you asking them?
If you ask a different question, a different answer
will likely be correct.

The fact that you can't recognise that most people
will get this baffles me.

Exactly what is it that you think I fail to recognize?

The fact that when ever someone provides an example
you try to twist and distort its meaning to be the exact
opposite of what was meant ...

I have not done that.

You presented an example of asking people about
where the mass of a tree comes from. I correctly said
that the largest portion of the mass of a healthy, living
tree is water, which came from the ground. You then
tried to change the question to being about wood.

Caveman asked what would happen when a lassoed
galaxy is relased. After I answered that it would stay
about where it is relative to us for a very long time, he
claimed the correct answer is that it moves toward us.
But that wouldn't happen until long after the galaxy is
released.

So let me do this a bit differently.

...

Good models come from theoretician and experimentalists.
The experimentalists aren't using "common sense" they
are running experiments and recording results.

Good experiments are designed using commom sense.
The design is not random, by dictate from a higher
authority, or based on aesthetics. It comes from an
experimenter applying common sense to the information
available to him.

The results are analyzed using common sense. They are
not analyzed with randomly-selected math, proceedures
dictated by a higher authority, or for their aesthetic value.
They are analyzed in a way that makes sense to the
analyst.

You're trying to envelope to much under the title of
common sense.

It is just a very general term. Like "space" referring to
everything not on the Earth.

-- Jeff, in Minneapolis

[caveman1917]

Caveman asked what would happen when a lassoed
galaxy is relased. After I answered that it would stay
about where it is relative to us for a very long time, he
claimed the correct answer is that it moves toward us.

I said that the correct answer is that it recedes from us just like everything else, but that it will first approach and pass us and recede from us the other side.

But that wouldn't happen until long after the galaxy is
released.

No, your answer is completely absolutely wrong. It's not even close.

[Jeff Root]

I agree that it was ambiguous.

Well i did ask you to be precise.

I didn't notice that some of the terms required further
definition to remove ambiguity. I knew what I meant
and didn't see that it could be interpreted otherwise.

I've done something below which should remove any
possible remaining ambiguity.

What I meant was that, as the galaxy goes whizzing past
all sorts of other galaxies, its speed relative to the galaxies
it is passing gradually decreases.

So which is it, the speed relative to the galaxies it is passing
asymptotically decreases to zero or its speed asymptotically
approaches that of the galaxies it is passing? Only one of
those is correct. The distinction is mathematically subtle but
important, can you using common sense see the distinction
between those two?

The second is correct, the first is very nearly correct: The
speed relative to the galaxies it is passing asymptotically
decreases *toward* zero, not *to* zero. With that little
change, the two statements are equivalent.

Far off in the distance is a bunch of galaxies that it has zero
speed relative to. Namely us. The Local Group and whatever
other galaxies we are gravitationally bound to.

That is not correct, it will not maintain zero speed relative to us.

Approximately zero speed, for a long time. Until the galaxies
we're gravitationally bound to become the dominant source
of gravity for it.

I've made an animation to illustrate what I believe happens
to a lassoed galaxy after it is released. Let's look at it, then
I'll come back to responding to your comments:

http://www.freemars.org/jeff2/expand5d.gif

The dots represent galaxy clusters. They move away from
each other at a constant rate of 1 pixel per frame per 40 pixels.
No gravitational slowing or acceleration.

The blue dot represents our Local Group.

The yellow dot represents the lassoed galaxy, from the time
it is lassoed onward. It remains at a constant distance from us.

The black space which can be seen in the first few frames is
where the galaxy was lassoed from.

The red dot is a reference cluster of galaxies, initially 1/3 the
distance from us to the lassoed galaxy. Since it is impossible
to follow individual dots in the early part of the animation, it
helps to show what is happening.

The black space moves away from the yellow dot very rapidly.
The red dot moves toward and past the yellow dot at a slower
pace. The gray dots closer to us (the blue dot) approach the
yellow dot even more slowly. In general, the speed of the dots
passing the yellow dot declines over time, approaching zero
asymptotically.

As time goes by, the galaxies passing the lassoed galaxy
are galaxies that were closer and closer to us now.

That is also incorrect, it will asymptotically progress in
passing galaxies that are further and further from us now.

Wow.

What do you mean by "asymptotically progress" ?

Notice in the animation that as time goes by, the dots passing
the yellow dot started out from locations closer and closer to
the blue dot. First dots that were very distant from the blue
dot pass the yellow dot, then the red dot passes the yellow dot,
then dots which were initially close to the blue dot pass the
yellow dot. Not the other way around. What you said doesn't
make sense.

When does the galaxy start to approach us? When we are
the dominant big mass. Since we start out so far apart, the
gravitational attraction between us will be miniscule and
the acceleration vanishingly tiny. It could be long after the
last white dwarfs have grown dark that the galaxy finally
passes or collides with us. That is so very far in the future
that it seemed a bit silly to mention it as "what happens
when you sever the lasso". Basically the galaxy will just
sit there for a long, long time.

That is also incorrect, it will immediately start to approach
us faster and faster, fly past us and recede from us the other
side and keep receding forever.

There is no reason for it to accelerate toward us until the
group of galaxies we are in becomes the dominant mass
attracting it. That doesn't happen until the other galaxies
have moved away. Even then the attractive force will be
miniscule for a very, very long time.

If you think the lassoed galaxy starts accelerating toward
us as soon as it is released, I'd be very interested in what
the mechanism is supposed to be,

Because the math says so. If you want a newtonian picture,
because of the attraction of the sphere of mass centered on
us up to the galaxy.

Assuming a roughly homogeneous Universe, there is just as
much mass attracting the galaxy in every other direction.

The yellow dot in my animation is always surrounded by dots
about equally in all directions, except those which pass close
to it. If I continued the animation a couple hundred frames
longer, eventually the blue dot and yellow dot would be the
only dots in the frame. Then they would be accelerating
toward each other. Not a whole lot before that.

Just saying "i have described it exactly correctly" does not
make that so,

Of course not. Why do you bother to type such a silly thing?

Yet I'm as sure as before that I have described it exactly
correctly. All I have as evidence to think I might not have
is your assertions that I haven't.

your common sense failed you on this one.

Let's see some evidence beyond your assertions.

-- Jeff, in Minneapolis

[DoggerDan]

The first problem is that there is no indication that there is a "centre" as you describe. I'll go with the balloon analogy here. If the universe is just the surface of the balloon then the "centre" of the balloon doesn't represent any point in 3D space. At best it represents a point in time

Ah, but if expansion were reversed, where would the mass of the universe wind up? Obviously, all at one point, so also obviously, the center of the universe is everywhere. That is, the universe is the center of itself.

[WayneFrancis]

Thank you :-)

Just re-enforces the view that you argue for the sack of arguing.

It would vary from species to species, growing conditions,
and so forth, but I agree it doesn't matter. :-)


That wood certainly did not come from that particular tree.
Wood generally has a lower water content than the tree as
a whole. A tree containing only 30-40% water is either
dormant, dead, or dying. It would either have lost its leaves
or the leaves would have shriveled up so severely that the
tree probably could not recover.


If it has been dried, as wood for human use always is,
most of its mass came from the air. If it has not been
dried, then the majority of its mass may have come from
either the air or the ground, depending on whether it is
heartwood or sapwood, whether it was taken from a
growing tree or a dormant one, and so forth.


Is that from the video? At 56 minutes, it probably would
take over a day for me to download.


The video shows that? Could be. The blog pages don't.
The blogger tried to, and the comments are interesting.
But they don't demonstrate the accuracy or inaccuracy of
common sense.

The point is most people even taught about photosynthesis don't connect that process with the mass of the tree. Most people think the mass of the tree come entirely from the ground. Regardless of the water content most people think the rest of the bulk of the tree comes from the soil. This is false.

Yes. That is just wrong. Decades ago when quantum
mechancs was a new thing, the people who were trying
to explain it to others told them that the rules of quantum
mechanics defy common sense. The students accepted
that, since for them, at the time, it was true. The rules
of quantum mechanics defied the common sense of those
students at that time. But once they understood the rules,
it was no longer true. Their common sense grew to include
the new rules. But they believed what they had been told:
that common sense was inadequate. So they perpetuated
the myth, and interpreted common sense to be something
which remains fixed and cannot grow. Nothing could be
further from the truth. Common sense is totally dependant
on learning. It starts at zero with the innate ability of an
intelligent mind to learn, and grows from there.

Yet many people can learn something and still not believe it because their "common sense" tells them that it isn't true.

That's amusing.

A baby has innate ability to grasp things and put them in
its mouth. It has no common sense. It has no ability to
discern what will be a good thing to put in its mouth and
what will be a bad thing. It has to learn common sense.
People have to learn common sense. They have to learn
how things work in order to have common sense about
how things work. Science is a methodcal process for
discovering how things work. It is common sense applied
to observations and measurements, which creates new
knowledge and new common sense which did not exist
before.

I've stated multiple times there is a difference from common experience leading to common sense and advance learning and experimentation leading to a calculated decision based on a scientific model. For a scientist it may common sense to use proven models but that doesn't make the model common senese.

Yes, I know that is what you are saying, and I think you
are more wrong about it than right. There certainly is a
large measure of truth in it, just as there is a large
measure of carbon in a tree.

Again you seem to deliberately avoid the point. Fact Most people don't understand photosynthesis even when they have been taught it for years in school.

I think what is going on here is that you are looking
at the differences rather than the similarities. You see
differences between what common sense would say and
what closer inspection and analysis show, and say that
common sense fails. But most of the time common sense
works just fine. It is when it fails that it gets noticed
and commented on.

What is going on here is what often goes on here when everyone suggests that you are using different definitions then everyone else is used to. You can't admit you are wrong and that your definition is correct no and everyone should agree with your definition and pretend that everyone here is some how always wrong.

The question was about trees, not wood. Wood that
people use, whether for building and making things or
for burning, is always dried.

I've explained the issue multiple times. You deliberately distort anything to fit your view. The documentary clearly demonstrates how even after being taught about photosynthesis most people still don't get the basic premise and the big reason is that it goes against their common sense view of the world.

A tree that has a water content of 50% or less is either
dormant, becoming dormant, dead, or dying.

Keep ignoring the point being made and latch on to anything to lead people off topic again

It won't? If you ask people what elements humans
are made of, most won't come up with a list similar
to yours? Or what question are you asking them?
If you ask a different question, a different answer
will likely be correct.

Again your missing the point and probably deliberately distorting the premiss.

Exactly what is it that you think I fail to recognize?

I think you fully recognize what you are doing. No one can cherry pick, hand wave, and constantly set up straw men to the extent you are without knowing what they are doing.

I have not done that.

Yes you have. Not only with me but with caveman1917 just in this thread.

You presented an example of asking people about
where the mass of a tree comes from. I correctly said
that the largest portion of the mass of a healthy, living
tree is water, which came from the ground. You then
tried to change the question to being about wood.

Yes I've provided an example of asking people about where the mass of a tree comes from and I may not have stated it well enough the first time and you latched on to most trees having MC > 50%. I elaborated and pointed out multiple times that most people don't consider photosynthesis at all in contributing to the mass of the tree by sequestering carbon from the atmosphere. You continue to ignore that was the general premiss because it shows how common sense often fails us even when people are taught something. But again you are getting very good lately of ignoring facts like that and moving goal posts.

Caveman asked what would happen when a lassoed
galaxy is relased. After I answered that it would stay
about where it is relative to us for a very long time, he
claimed the correct answer is that it moves toward us.
But that wouldn't happen until long after the galaxy is
released.


Good experiments are designed using commom sense.
The design is not random, by dictate from a higher
authority, or based on aesthetics. It comes from an
experimenter applying common sense to the information
available to him.

The results are analyzed using common sense. They are
not analyzed with randomly-selected math, proceedures
dictated by a higher authority, or for their aesthetic value.
They are analyzed in a way that makes sense to the
analyst.


It is just a very general term. Like "space" referring to
everything not on the Earth.

-- Jeff, in Minneapolis

I'm done with your....posting

[WayneFrancis]

Ah, but if expansion were reversed, where would the mass of the universe wind up? Obviously, all at one point, so also obviously, the center of the universe is everywhere. That is, the universe is the center of itself.

Not if the universe is open and unbounded, infinite. And I'd say once you get to a situation that the entire universe has no dimensions in both space and time then the concept of a point in space has no concept.

But I get your premiss. The universe has no centre and thus every point could be thought of as the centre. Centre then becomes really meaningless and the only centre I'd really say exists is the "centre" with respect with the time dimension and that is less a centre then a start.

[Shaula]

And I'd say once you get to a situation that the entire universe has no dimensions in both space and time then the concept of a point in space has no concept.

And before that our physics models break down. So what is really being said is:

"It you extrapolate back beyond the bounds of applicability of the theory, then make an assumption about the non-observable universe for which we have no evidence, then you get a result that supports the idea that the universe has a centre"

This is pretty much along the same lines as saying "By extrapolating the growth of my kitten back far enough I can prove that cats are born from black holes"