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'[OT] What is the most correct value of the gravita'
2011\02\16@175112 by Isaac Marino Bavaresco

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I was trying to do some gravitational calculations but I found several
different values for G.
Does anybody know what is the most accurate and current value?

Isaac

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2011\02\16@180210 by Joe Koberg

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On 2011-02-16 16:51, Isaac Marino Bavaresco wrote:
> I was trying to do some gravitational calculations but I found several
> different values for G.
> Does anybody know what is the most accurate and current value?
>

Depends on the amount of earth between you and the planetary centroid.

>From https://secure.wikimedia.org/wikipedia/en/wiki/Earth%27s_gravity :

> The precise strength of the Earth's gravity varies depending on
> location. The nominal "average" value at the Earth's surface, known a
> standard gravity is, by definition, 9.80665 m/s^2 (32.1740 ft/s^2 ).

Check out the measured gravity map at that page!

Joe

2011\02\16@181229 by Olin Lathrop

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Joe Koberg wrote:
> On 2011-02-16 16:51, Isaac Marino Bavaresco wrote:
>> I was trying to do some gravitational calculations but I found
>> several different values for G.
>> Does anybody know what is the most accurate and current value?
>
> Depends on the amount of earth between you and the planetary centroid.

No, it doesn't at all.  The gravitational constant is just that, a constant..
It is one of the fundamental parameters our universe was built with, like
the speed of light, the impedence of free space, and a few others.


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2011\02\16@182111 by Isaac Marino Bavaresco

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Em 16/2/2011 21:02, Joe Koberg escreveu:
> On 2011-02-16 16:51, Isaac Marino Bavaresco wrote:
>> I was trying to do some gravitational calculations but I found several
>> different values for G.
>> Does anybody know what is the most accurate and current value?
>>
> Depends on the amount of earth between you and the planetary centroid.
>
> >From https://secure.wikimedia.org/wikipedia/en/wiki/Earth%27s_gravity :
>
>> The precise strength of the Earth's gravity varies depending on
>> location. The nominal "average" value at the Earth's surface, known a
>> standard gravity is, by definition, 9.80665 m/s^2 (32.1740 ft/s^2 ).
>
> Check out the measured gravity map at that page!
>
> Joe


I want to know the value of the "Big G", the Universal Gravitational
Constant, not the acceleration due to the gravity.

I've seen values from 6:6656e-11 m^3.kg^-1.s^-2 to 6.6873e-11, and also
6:67259e-11 and 6.67428e-11 (Wikipedia).

2011\02\16@184527 by Olin Lathrop

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Isaac Marino Bavaresco wrote:
> I've seen values from 6:6656e-11 m^3.kg^-1.s^-2 to 6.6873e-11, and
> also 6:67259e-11 and 6.67428e-11 (Wikipedia).

Looks like they all agree it's 6.7e-11.


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2011\02\16@184634 by Carl Denk

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There are 2 issues as I understand.
1: The gravitational constant is an assumed standard average value for use at earth's surface for standard results of calculations.
2: The gravitation at earth's surface does vary from location to location for many reasons.

If one is doing hypothetical calculations, and for most practical applications, the constant is fine. For a very few specific applications possibly including the path of a spacecraft and academic problems, the actual value at a specific location may be required

2011\02\16@185849 by Joe Koberg

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On 2011-02-16 17:12, Olin Lathrop wrote:
> Joe Koberg wrote:
>> On 2011-02-16 16:51, Isaac Marino Bavaresco wrote:
>>> I was trying to do some gravitational calculations but I found
>>> several different values for G.
>>> Does anybody know what is the most accurate and current value?
>> Depends on the amount of earth between you and the planetary centroid.
> No, it doesn't at all.  The gravitational constant is just that, a constant.
> It is one of the fundamental parameters our universe was built with, like
> the speed of light, the impedence of free space, and a few others.
>

Whoops I was thinking "little g" rather than "big g"

Joe

2011\02\16@185930 by Veronica Merryfield

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61 variations here http://www.blazelabs.com/f-u-massvariation.asp along with some of the history, explanation etc


On 2011-02-16, at 3:21 PM, Isaac Marino Bavaresco wrote:

{Quote hidden}

> -

2011\02\16@190436 by Dave Tweed

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Isaac Marino Bavaresco wrote:
> I want to know the value of the "Big G", the Universal Gravitational
> Constant, not the acceleration due to the gravity.
>
> I've seen values from 6:6656e-11 m^3.kg^-1.s^-2 to 6.6873e-11, and also
> 6:67259e-11 and 6.67428e-11 (Wikipedia).

I thought that's what you meant.

It's actually somewhat of a scientific embarrassment that of all the
fundamental physical constants, we only know G to within one part in 10^4 or
so. There was an article not too long ago in Scientific American about this..
IIRC, recent work with supercold atomic fountains may provide a way to
determine it more precisely.

-- Dave Twee

2011\02\16@190822 by Spehro Pefhany

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At 06:21 PM 2/16/2011, you wrote:
>I want to know the value of the "Big G", the Universal Gravitational
>Constant, not the acceleration due to the gravity.
>
>I've seen values from 6:6656e-11 m^3.kg^-1.s^-2 to 6.6873e-11, and also
>6:67259e-11 and 6.67428e-11 (Wikipedia).

Wikipedia references the following document:
physics.nist.gov/cuu/Constants/codata.pdf
...which probably has more information than you want on what scientists
believe the Newtonian constant of gravity to be. Figure 2 summarizes
recent experiments, and there is a lot more information in the text and
table XXVII (the latter also has their "bottom line" recommended value and relative
standard uncertainty). I think if you have to ask, this is probably more
than good enough...

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
spam_OUTspeffTakeThisOuTspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

2011\02\16@213620 by RussellMc

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> I want to know the value of the "Big G", the Universal Gravitational constant,

Ignoring for the purposes of the exercise that there is a significant
body of opinion that it may not be one :-).

Nor may (almost?) any other "constant" that we think we know. The Fine
Structure constant may vary with time (and time would vary with the
fine structure constant :-) ) and the universe MAY be anisotropic wrt
the FSC. ie "Look out" in one direction and you may see results which
vary slightly from those in another direction. All very annoying.
Results to date look very very very like systemic error if you can't
believe they can be true, but systemic error had been sought with
thimbles and care (not to  mention forks and hope) but to then, to no
avail. Things may have changed since then (within last year).

A good thing about G being known with such imprecision is that the
underlying "reality" can wander around a bit before we notice too much
:-).



      Russel

2011\02\17@065706 by Isaac Marino Bavaresco

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Em 17/2/2011 00:35, RussellMc escreveu:
{Quote hidden}

You are scaring me!

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2011\02\17@065848 by Isaac Marino Bavaresco

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Em 16/2/2011 22:08, Spehro Pefhany escreveu:
{Quote hidden}

Thank you, this document is very useful. At last a trustful source.

Best regards,

Isaac

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2011\02\17@073136 by Isaac Marino Bavaresco

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Em 16/2/2011 21:59, Veronica Merryfield escreveu:
> 61 variations here http://www.blazelabs.com/f-u-massvariation.asp along with some of the history, explanation etc


Interesting, but seems a little sci-fi-ish.

There is a link to <http://www.expanding-earth.org/page_9.htm>, which
resembles pseudo-science, although a nice subject for a sci-fi book.

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2011\02\17@073739 by RussellMc

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>>> I want to know the value of the "Big G", the Universal Gravitational constant,

>> The Fine
>> Structure constant may vary with time (and time would vary with the
>> fine structure constant :-) ) and the universe MAY be anisotropic wrt
>> the FSC. ie "Look out" in one direction and you may see results which
>> vary slightly from those in another direction. All very annoying.

> You are scaring me!

That's my job.

Never assume that tghe certainties of today will be contained in the
knowledge of tomorrow :-).


         Russell

Physorg
September 2010

http://www.physorg.com/news202921592.html

PhysOrg.com) -- One of the most controversial questions in cosmology
is why the fundamental constants of nature seem fine-tuned for life.
One of these fundamental constants is the fine-structure constant, or
alpha, which is the coupling constant for the electromagnetic force
and equal to about 1/137.0359. If alpha were just 4% bigger or smaller
than it is, stars wouldn't be able to make carbon and oxygen, which
would have made it impossible for life as we know it to exist. Now,
results from a new study show that alpha seems to have varied a tiny
bit in different directions of the universe billions of years ago,
being slightly smaller in the northern hemisphere and slightly larger
in the southern hemisphere. One intriguing possible implication is
that the fine-structure constant is continuously varying in space, and
seems fine-tuned for life in our neighborhood of the universe.

_____________

NIST, 2007

Improved Limits on Variation of the Fine Structure
Constant and Violation of Local Position Invariance

http://tf.nist.gov/general/pdf/2238.pdf

14 names ...
Time and Frequency Division MS 847
National Institute of Standards and Technology
Boulder, CO USA

F. Levi and L. Lorini
Istituto Nazionale di Ricerca Metrologica
Strada delle Cacce 91 I-10135
Torino, Italy


I like this:

"   ... , assuming invariance of other fundamental constants.
Comparison of our results with those
previously reported for the absolute optical frequency measurements of ..."

:-)

______________

PRECISION SPECTROSCOPY IN ASTROPHYSICS
ESO Astrophysics Symposia, 2008, 2008, 101-104, DOI:
10.1007/978-3-540-75485-5_22
On the Variation of the Fine-structure Constant, and Precision Spectroscopy

http://www.springerlink.com/content/60n6h065911734m2/

__________

Why Sean thinks you can rest easy

http://blogs.discovermagazine.com/cosmicvariance/2010/10/18/the-fine-structure-constant-is-probably-constant/

_______________

1 month older

http://www.space.com/9122-physics-fundamental-cosmic-constant-shifty.htm

2011\02\17@075209 by Olin Lathrop

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Carl Denk wrote:
> 1: The gravitational constant is an assumed standard average value for
> use at earth's surface for standard results of calculations.

No.  You are confusing the universal gravitational constant (what the OP
asked about) with the accelleration due to gravity at earth's surface.  The
first is usually referred to as "G", the latter as "g".

The first (G) is the proportionality constant of the equation that describes
how two masses attract each other.  It has nothing specifically to do with
the earth other than the earth is a mass described by the equation.

The second (g) is the effect of gravity felt at the surface of the earth.
This varies because the earth varies.  Although it does vary due to
altitude, the composition of the earth nearby underneath, these are
relatively small variations if you stick to the earth's surface.  9.8m/s**2
is correct at its implied accuracy.


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2011\02\17@075935 by Olin Lathrop

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RussellMc wrote:
> PhysOrg.com) -- One of the most controversial questions in cosmology
> is why the fundamental constants of nature seem fine-tuned for life.

If they weren't we wouldn't be here to ask the question.  Or put another
way, you can't draw any conclusions from a self-selected set of samples,
even more so when that is only one sample.

2011\02\17@084445 by Isaac Marino Bavaresco

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Em 17/2/2011 10:59, Olin Lathrop escreveu:
> RussellMc wrote:
>> PhysOrg.com) -- One of the most controversial questions in cosmology
>> is why the fundamental constants of nature seem fine-tuned for life.
> If they weren't we wouldn't be here to ask the question.  Or put another
> way, you can't draw any conclusions from a self-selected set of samples,
> even more so when that is only one sample.


I would say that life was fine-tuned for the fundamental constants values :)

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2011\02\17@104824 by N. T.

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RussellMc wrote:
>>>> I want to know the value of the "Big G", the Universal Gravitational constant,
>
>>> The Fine
>>> Structure constant may vary with time (and time would vary with the
>>> fine structure constant :-) ) and the universe MAY be anisotropic wrt
>>> the FSC. ie "Look out" in one direction and you may see results which
>>> vary slightly from those in another direction. All very annoying.
>
>> You are scaring me!
>
> That's my job.
>
> Never assume that tghe certainties of today will be contained in the
> knowledge of tomorrow :-).
>
>
>          Russell
>
> Physorg

Why not another tag -  [Phys], as a number of list members are quite
good at physics?

2011\02\17@111849 by RussellMc

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Note: My mailer added a CC to Olin, which it has not previously done,
and I have changed no settings. I note that Olin was bolloc... er
advising someone recently re direct CCs to him. I don't know if the
list server has decided Olin needs more friends, or if Gmail has, or
if Olin's interesting email client has.

>> PhysOrg.com wrote:

>>  -- One of the most controversial questions in cosmology
>> is why the fundamental constants of nature seem fine-tuned for life.>

> If they weren't we wouldn't be here to ask the question.

Otherwise known as the weak anthropic  principle.

But

While not disagreeing violently with the general point you are trying
to make, I note:

> Or put another
> way, you can't draw any conclusions from a self-selected set of samples,
> even more so when that is only one sample.

is not so safe an assumption here as it may be in some cases, and it's
at least arguable whether the sample is "self selected" and even one
sample can and here does convey information.

One sample tells us that life can and does exist.
A zero life sample would leave us wondering, except that if we are
wondering we may be life and probably exist :-).

And, if the probability of the universe supporting life of any sort is
as small as it appears to be, but we are here because of the weak
anthropic principle, then are there an infinitude of universes that we
are a probabilisitic part of, or is the "array of universes" sparse
and we are part of a few that are tailored, however such tailoring may
happen, or ... . AND is an infinitiude of unioverses more probable
than life (or other) diorected tailoring, or ...?,

All of which rather supports the assertion (Physorg's, not mine.)

"-- One of the most controversial questions in cosmology"

Along the way you get spinoff's such as Fermi's* paradox.

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

Which just adds weight to the assertion.
And interest.

The first discovered QUASAR wasn't named LGM1 for nothing.

         http://en.wikipedia.org/wiki/LGM-1

Or, maybe, it was :-)

        Russel

2011\02\18@080655 by Olin Lathrop

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RussellMc wrote:
> Note: My mailer added a CC to Olin, which it has not previously done,
> and I have changed no settings. I note that Olin was bolloc... er
> advising someone recently re direct CCs to him.

I was telling him to stop sending me CCs.  At best I get two copies of the
message.  At worst I accidentally reply to the CC copy and it therefore
doesn't go to the list, which makes the reply useless for me.


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2011\02\18@114257 by RussellMc

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>> Note: My mailer added a CC to Olin, which it has not previously done,
>> and I have changed no settings. I note that Olin was bolloc... er
>> advising someone recently re direct CCs to him.

> I was telling him to stop sending me CCs.  At best I get two copies of the
> message.  At worst I accidentally reply to the CC copy and it therefore
> doesn't go to the list, which makes the reply useless for me.

Yes indeedy - that's what I recall.
One man's advice is another man's freedom fighter :-).

It seems that the list or something interacting with it is doing it
generally for some ranks of General.

This message has been automatically CC'd to you (I've just removed the
CC) and my hind brain noted another with CC as I answered this. I'll
check to see if the pattern is obvious. Possibly Google not being evil
again and/or trying to be helpful.



            Russell

2011\02\18@130709 by Joe Koberg

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On 2011-02-18 10:42, RussellMc wrote:
>
>> I was telling him to stop sending me CCs.  At best I get two copies of the
>> message.  At worst I accidentally reply to the CC copy and it therefore
>> doesn't go to the list, which makes the reply useless for me.
> Yes indeedy - that's what I recall.
> One man's advice is another man's freedom fighter :-).
>
> It seems that the list or something interacting with it is doing it
> generally for some ranks of General.
>
With many mail clients,  "Reply All" replies to the list and CC's the sender.  This is the default behavior with this list's current settings and Thunderbird's default options.  It takes extra effort to remove the CC to the sender.  Since "Reply-To" is indeed set to this list, the "Reply" button will not CC the sender here.  (But on many lists, and with non-list CCs, it only replies directly to the sender, and "Reply All" is the normal action if you wish to Reply to All).

GNU Mailman can notice the CC line on the incoming mail, and avoid sending the list subscriber the corresponding list posting, **IF** the user has selected the "Avoid duplicates" option in their Mailman settings ( http://mailman.mit.edu/mailman/options/piclist ).  The description for the option says:
>
> When you are listed explicitly in the To: or Cc: headers of a list
> message, you can opt to not receive another copy from the mailing
> list. Select /Yes/ to avoid receiving copies from the mailing list;
> select /No/ to receive copies.
>

Of course, a reply to that direct mail doesn't seem like it would make it to the list. But I am not sure how Thunderbird sets the headers to the direct recipient.

To me it seems a good policy to make sure the person you're replying to has their own copy of your reply.  It gets to them immediately and eliminates the possibility of the list mangling it.  I personally have list postings going into their own threaded folder based on a rule, so there is no difficulty distinguishing the source or replying to the list posting.  Obviously, different people have different opinions.

Joe Koberg

2011\02\18@134450 by Olin Lathrop

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Joe Koberg wrote:
> To me it seems a good policy to make sure the person you're
> replying to has their own copy of your reply.  It gets to
> them immediately and eliminates the possibility of the list
> mangling it.

That is really bad policy.  So you're so much more important that the
recipient that you get to send one message thru the list like everyone else
and one additional spam message to get extra attention?  If someone doesn't
want to reply to your message, that's their choice.  You have no right to
send them a second spam message to insist on more free help or to try to cut
in line somehow.

Nobody is owed a reply here.  You only get replies because others decided to
volunteer their time to your issue.  You want to make as things easy and
un-annoying to the volunteers who donate their free time to respond here as
possible.  Your method basically penalizes people for responding, and so is
a really bad idea.


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2011\02\18@155429 by Joe Koberg

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On 2011-02-18 12:45, Olin Lathrop wrote:
{Quote hidden}

<< long reply reconsidered and omitted >>

This could quickly escalate.  I will just say you've assumed a lot of things about my intent that are wrong.  I would personally welcome direct followups. Your revulsion at my mail client's default Reply-All action prompted me to apologize and change my own behavior.

I am interested in posting technically relevant questions, and volunteering any help I can myself provide.   I don't know what else this list is supposed to be for.


Cheers,

Joe Koberg

2011\02\18@212917 by RussellMc

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> That is really bad policy.  So you're so much more important that the
> recipient that ..

Olin - the glass is half FULL !!!
At least.

_____________

I see that this message, too, had M. Lathrop nominated in the CC field.
Summat has changed.

Perhaps GMail has helpfully changed the default reply button from
"Reply" to "Reply All" , with the alternative being accessible via a
menu as before.

A look at some old screen dumps may allow this theory to be checked,
if anyone cared. As with many such things one tends to use the default
when it suits but when it is changed it is hard to recall whether it
really has or what it was, if there were several options. As some
senders who now have CC duplication are not GMailites a better option
may be that the list has changed iots to and CC field contents.


       Russell

2011\02\18@224646 by Justin Richards

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>
> PhysOrg.com) -- One of the most controversial questions in cosmology
> is why the fundamental constants of nature seem fine-tuned for life.

Interesting, I have often thought that there are too many things that
seem "convenient".

I find it "convenient" that a portable radio can be just that and the
transmitting end which doesn't really need to be portable is big and
bulky.

I find it "convenient" that water happens to be liquid at room
temperature and room temperature is just that.

Very "convenient" that PN junctions behave the way they do.

And so on.

A friend of mine has mentioned that we just captalise on certain
behaviors and make things work for us, which we do, but I just wonder.

All just too convenient.

Justi

2011\02\19@041603 by RussellMc

face picon face
> Interesting, I have often thought that there are too many things that
> seem "convenient".

For extreme "special pleading" I like the trail of accessible water
which increasingly appears to be available stretching out into the
solar system. It's like a computer game , or a TV junkyard challenge,
where a series of necessary or useful objects are left conveniently
lying around to be found. In the airless, waterless, inhospitable
reaches of the solar system it's as if, apparently, water has been
removed from the list in special cases.

Imagine, a few decades ago, how ludicrous the suggestion would have
been that there was free water essentially on the surface of the Moon.
Scratch that one off the list. When yuou can impact a spacecraft onto
the lunar surface and measure the water signature from earth I think
that that qualifies close enough.

Free water ON the surface of Mars. What a bizarre suggestion. And,
watch the video of
the water ice subliming away as you watch after being exposed by the
spacecrafty's trenching tool from under centimertres of loose gravel.

LOTS of water on the surface of Mars?
Apparently.
Look at the cliffside outwelling channels where the local water table
met a "valley". Then note the scale. Stand in the way of that lot and
yuou'd be very dead. Millions of litres. ...

But as you get out of the inner system it must get sparser. Right?
Io, perhaps, with water oceans under a relatively thin cap. And
perhaps not. But after a while it stops being surprising and just gets
astounding instead.

Not that I think that Occam and Murphy see a force majeur at work
here. But, they may be wrong :-).


           Russel

2011\02\19@092905 by Olin Lathrop

face picon face
Justin Richards wrote:
> I find it "convenient" that a portable radio can be just that and the
> transmitting end which doesn't really need to be portable is big and
> bulky.
>
> I find it "convenient" that water happens to be liquid at room
> temperature and room temperature is just that.
>
> Very "convenient" that PN junctions behave the way they do.

This is non-logic.  Of course we find the things convenient that are
convenient.  Where are your control cases?  Did you make a unbiased list of
many randomly chosen physical properties, then conduct a double blind test
with independent subjects that rate each by its convenience?  I didn't think
so.  Did you even try to come up with inconvenient properties as
counter-examples?

A even bigger failing of this logic than the total lack of control is the
impossibility of impartially rating the convenience of the properties since
we are largely here in our present form because of those properties.

Let's take the particularly silly statement about water and room
temperature.  We are water-based life forms, so of course our preferred
temperature is going to match up with naturally occurring liquid water.
That means nothing therefore.  However, here is a case where we do have
other examples we can check for naturally occurring liquid water.  We have a
pretty good idea of the chemical makeup and conditions on many of the
various planets and moons in our star system.  Of these, how many have
naturally occurring liquid water?  Only two that I'm aware of, and the
second is mostly a guess because it is expected to have oceans under ice.  A
third almost certainly had liquid water in the past, but didn't have the
gravity to hold on to it over time.  Now that would be rather inconvenient
to have the water you evolved to depend on evaporate into space.

What about the speed of light?  It's really really inconveniently slow for
humans on a cosmic scale.  If it does represent the cosmic speed limit as we
think it does, then that's pretty darn inconvenient for us getting off this
rock before the sun does something very inconvenient.  The earth is already
half way to its expiration date, and we've only just gotten to sliced bread,
flush toilets, and the ability to make silly statements.


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2011\02\19@093746 by Olin Lathrop

face picon face
RussellMc wrote:
> For extreme "special pleading" I like the trail of accessible water
> which increasingly appears to be available stretching out into the
> solar system.

I don't see why that should be surprising.  Since you're talking about a
star system, you obviously are already looking at a very special and unusual
occurrance in the universe where heavy elements collect.  Those heavy
elements are going to organize themselves into molecules.  Water is a simple
molecule, made of two shovel fulls of the most abundant element in the
universe and one shovel full of a reasonably abundant one once you're
already in the vicinity of one of the heavy element collection anomalies.
These two molecules are at a much lower energy state when combined as water
than they are individually, so the combination is heavily favored when it is
possible.

The real question is why would you NOT expect to find water in various
places as you started poking around?


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2011\02\19@100350 by RussellMc

face picon face
> Of these, how many have
> naturally occurring liquid water?  Only two that I'm aware of, and the
> second is mostly a guess because it is expected to have oceans under ice.

If "naturally occurring" includes having it carried in naturally by
comets, then probably N.

The lunar southern polar ice appears to lie in shaded areas at shallow
depths or effectively on the surface from cometary deposition.

One theory, perhaps not as much in vogue nowadays as once,  holds that
earth's water supply is substantially augmented by the daily
deposition of water into the atmosphere by micro water comets in the
metres diameter size range.

The outer reaches of the solar system are apparently "well supplied"
[tm] with water ice. Once you get proof [tm, again] that water is
deposited from this source at one lactation [lunar south pole] then
you may wonder where else it may preferentially be deposited.  If
there ended up being deposits at some of the various stable Lagrange
points nobody should be too surprised.

> third almost certainly had liquid water in the past, but didn't have the
> gravity to hold on to it over time.  Now that would be rather inconvenient
> to have the water you evolved to depend on evaporate into space.

This "third" is presumably Mars. While much water may well have been
lost there also appears to be much left. In 2008 Phoenix demonstrated
surface water ice under a thin layer of gravel - videos are available.
There are a very large number  of inferred but high quality [tm]
indications that substantial  water exists.

Io's putative oceans are inferred based on stuff we happen to have
been able to learn. If we knew more of other-where's we may know about
other possible water locations.

> What about the speed of light?

It's possibly falling :-)
Possibly from a very much higher initial speed.

And "expansion" - a very strong case of special pleading which much
current cosmology rests on - had the SOL at vastly greater values than
now.
"Expansion" on which a ;large portion of modern cosmology rests, lies
in the "and then, a miracle happened for just long enough to make our
theory work." class of science. Very seriously proposed though. Works
for me :-).

> It's really really inconveniently slow for
> humans on a cosmic scale.  If it does represent the cosmic speed limit as we
> think it does, then that's pretty darn inconvenient for us getting off this
> rock before the sun does something very inconvenient.

Nah, it's just a Darwin award test :-).
Fermi's paradox, which  I referred to earlier in this thread, asks
"where are they".
Even at the SOL it would take a really advanced civilisation far less
time than appears to have been available to spread across the
universe.Just not good wrt human lifetimes.

> The earth is already
> half way to its expiration date,

Not really - we just haven't worked out how to reset the counter yet.


          Russell

2011\02\19@110307 by RussellMc

face picon face
> Even at the SOL it would take a really advanced civilisation far less
> time than appears to have been available to spread across the
> universe.Just not good wrt human lifetimes.

Make that "galaxy".
Spreading across any given universe when the maximum speed of travel,
which happens incidentally to require infinite energy to achieve * is
not fast enough to get you from one "side ** to the other inside the
time that the whole system  is believed [tm] to have existed for. ie
no matter how fast the speed of light was set to, if the universe is
further across than light can travel in the life of the universe then
"you can't get there from here".

This is perhaps the only situation in existence where that old joke is
true - and is the reason that inflation was needed to make the
theories  work. In a system where one side CANNOT "talk to" the other
but they both obey the same complex rul book and share history,
something special must have happened. (Mustn't it ? :-) )
Occam feels decidedlyu shaky when almost any sort of cosmology gets discussed.

* Unless you have zero rest mass. Photons and other light speed
particles (which may or may not include neutrinos)  MUST travel at the
speed of light in current medium and live in a blissful timeless
existence where everything be's here now and the whole of creation is
one big timeless, positionless happy family, where there is no
position or time ordering or even variation. This is all obviously a
pack of rubbish BUT if it is not so, why not. If travelling at the
speed of light, from where comes time to measure velocity or time
priority. How CAN a photon leaving Sol and the same time as one
leaving Alplha Centauri Proxima arrive "first".

That this matters was shown nicely a while ago when a physicist
commented thaty they were not using photons for and experiment related
to "locality" (Einstein's "spooky" action at a distance.) The
experimenter noted that using a "timeless" particle in such cases made
him feel uneasy that something could be overlooked.


 Russell

** the universe has no sides

2011\02\19@130844 by Bob Blick

face
flavicon
face
On Sat, 19 Feb 2011 09:29 -0500, "Olin Lathrop"  wrote:

> What about the speed of light?  It's really really inconveniently slow
> for
> humans on a cosmic scale.  If it does represent the cosmic speed limit as
> we
> think it does, then that's pretty darn inconvenient for us getting off
> this
> rock before the sun does something very inconvenient.  The earth is
> already
> half way to its expiration date, and we've only just gotten to sliced
> bread,
> flush toilets, and the ability to make silly statements.

Hurrah! I give that a +1.

Friendly regards,
Bob


-- http://www.fastmail.fm - A no graphics, no pop-ups email service

2011\02\19@134319 by Olin Lathrop

face picon face
RussellMc wrote:
>> Of these, how many have
>> naturally occurring liquid water? Only two that I'm aware of, and the
>> second is mostly a guess because it is expected to have oceans under
>> ice.
>
> If "naturally occurring" includes having it carried in naturally by
> comets, then probably N.
>
> The lunar southern polar ice appears to lie in shaded areas at shallow
> depths or effectively on the surface from cometary deposition.

Note I was referring to *liquid* water.  This was a response to someone
claiming that the physical constants and such were all rather convenient,
and cited liquid water, room temperature, and the combination thereof as
evidence.

As I said in another message, not so rare existance of water (H2O) in a star
systems shouldn't be surprising.  However liquid water at "convenient" room
temperatures and pressures for human life is a different matter.

> One theory, perhaps not as much in vogue nowadays as once,  holds that
> earth's water supply is substantially augmented by the daily
> deposition of water into the atmosphere by micro water comets in the
> metres diameter size range.

The earth also has sufficient gravity such that it will have retained most
of its water over the last 4 1/4 billion years.  This is not the case for
Mars.

>> third almost certainly had liquid water in the past, but didn't have
>> the gravity to hold on to it over time. Now that would be rather
>> inconvenient to have the water you evolved to depend on evaporate
>> into space.
>
> This "third" is presumably Mars. While much water may well have been
> lost there also appears to be much left.

Yes there is good evidence of significant H2O still on Mars.  However, that
is quite certainly a small fraction of what there once was, and nobody has
found or is likely to find liquid water naturally occurring on the surface
of Mars today, at least not for very long.


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(978) 742-9014.  Gold level PIC consultants since 2000

2011\02\19@152904 by Bob Axtell

face picon face
On 2/19/2011 8:03 AM, RussellMc wrote:
{Quote hidden}

Well written, Russell!

Have a great day!

--Bob

2011\02\20@075702 by Gerhard Fiedler

picon face
Olin Lathrop wrote:

> RussellMc wrote:
>>> Of these, how many have naturally occurring liquid water? Only two
>>> that I'm aware of, and the second is mostly a guess because it is
>>> expected to have oceans under ice.
>>
>> If "naturally occurring" includes having it carried in naturally by
>> comets, then probably N.
>>
>> The lunar southern polar ice appears to lie in shaded areas at
>> shallow depths or effectively on the surface from cometary
>> deposition.
>
> Note I was referring to *liquid* water.  This was a response to
> someone claiming that the physical constants and such were all rather
> convenient, and cited liquid water, room temperature, and the
> combination thereof as evidence.

If you've seen frozen tissue (animal or plant) that was alive before
frozen, you probably stop thinking that the freezing point and freezing
behavior is "convenient" :)

I think this is mostly a moot discussion, as it is all in the eyes of
the beholder. Most of us here are engineers or have an engineer's
attitude towards world, and for an engineer solving problems of the
physical world is his idea of fun. Most of the problems engineers solve
are inconveniences of the physical world. So the mere fact of our
existence is proof enough that the physical world is inconvenient. That
we tend not to see it that way is simply because we see physical
inconveniences as opportunities for having fun. (Well, not always, but
you get the idea.)

The rest is also obvious... we look mainly for what's helpful for us,
and tend to consider other results maybe interesting, but secondary.
Even if a single individual could develop a non-anthropocentric view of
the world, the body of scientific knowledge has been created by millions
of contributors with anthropocentric views and necessarily reflects
that. So that single individual that was successful in shedding the
anthropocentric viewpoint could not use science at all to look at the
world when trying to maintain the non-anthropocentric viewpoint.

Gerhar

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