BS: Gravity, meters and physics made easy

Subject: BS: Gravity, meters and physics made easy
From: Mrrzy
Date: 07 Apr 09 - 12:43 PM

Thoghts from the middle of the night...

OK, so, what IS a meter, anyway? Is there some real-life reference, like for the kilo, which is what the thing that somebody decided was a kilo? That is, there is a real-life mass of something, metal I think, that is the referent for the kilo. It is what a kilo is, that exact mass.

But is there a meter somewhere that is the meter? The reason I ask is that it occurred to me that if we lengthened the meter slightly, I think it's lengthen and not shorten, then you wouldn't have to depend on the kindness of your physics professor for g (the gravitational constant) to equal 10 meters per second squared. (The nice ones always did, the jerks never did.) Right now it's kind of 9.98, if I recall aright. (Which is why it was so jerky of the mean ones not to allow g=10m/s/s). Why not redefine the meter, if there is no actual definition, to be the distance over which matter accelerates by 1 second?

Subject: RE: BS: Gravity, meters and physics made easy
From: Leadfingers
Date: 07 Apr 09 - 12:55 PM

Why cant I find that "Revocation of Independance2 when I need it ?
In ENGLISH a Meter is a measuring device while a METRE is a unit of length !


LOL Couldnt resist that ! LOL

Subject: RE: BS: Gravity, meters and physics made easy
From: Amos
Date: 07 Apr 09 - 12:55 PM

bECAUSE THE GRAVITATIONAL CONSTANT ONLY APPLIES (damn capslock) to this region of space under theimmediate mass of this planet. And even onthis planet it varieswith altitude, and some local anomalies here and there.

There is a standard meter.

"1960
        

On October 14, the Eleventh General Conference on Weights and Measures redefined the International Standard of Length as 1,650,763.73 vacuum wavelengths of light resulting from unperturbed atomic energy level transition 2p10 ­ 5d5 of the krypton isotope having an atomic weight of 86. The wavelength is

λ = 1 m / 1,650,763.73 = 0.605,780,211 µm

At different times some national laboratories used light sources other than krypton 86 as length standards. Mercury 198 and cadmium 114 were among these and they were accepted by the General Conference as secondary length standards.

1964
        

Helium-Neon stabilized laser wavelengths were coming into use as length standards. Although the laser wavelength was generally accepted as a secondary standard, its widening use was mainly based on its remarkable coherence. Long distances could be measured by laser interferometry that would be impossible with atomic light sources. Line scales of length are measured by dynamic (fringe counting) laser interferometry at NIST.

1980
        

The iodine stabilized Helium-Neon laser wavelength was accepted as a length standard. It had a wavelength uncertainty of 1 part in 1010 at the time.

1983
        

On October 20, the meter was redefined again. The definition states that the meter is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second. The speed of light is

c = 299,792,458 m/s

The second is determined to an uncertainty, U = 1 part in 1014 by the Cesium clock. The General Conference made the iodine stabilized Helium-Neon laser a recommended radiation for realizing the meter at this time. The wavelength of this laser is

λHeNe = 632.99139822 nm

with an estimated relative standard uncertainty (U) of ± 2.5 x 10−11.

In all of these changes in definition, the goal was not only to improve the precision of the definition, but also to change its actual length as little as possible." (From Here).

Subject: RE: BS: Gravity, meters and physics made easy
From: beardedbruce
Date: 07 Apr 09 - 12:58 PM

The metre or meter (from the Greek ìÝôñïí /´metron/) [1] is a unit of length. It is the basic unit of length in the metric system and in the International System of Units (SI), used around the world for general and scientific purposes. Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent 1⁄10,000,000 of the distance from the equator to the north pole through Paris. In 1983, it was redefined by the International Bureau of Weights and Measures (BIPM) as the distance travelled by light in free space in 1⁄299,792,458 of a second.[2]The BIPM does not distinguish between quantum vacuum and free space.[3]

Subject: RE: BS: Gravity, meters and physics made easy
From: beardedbruce
Date: 07 Apr 09 - 01:00 PM

Or, from the NIST:

Unit of length (meter)   Abbreviations: CGPM, CIPM, BIPM


       The origins of the meter go back to at least the 18th century. At that time, there were two competing approaches to the definition of a standard unit of length. Some suggested defining the meter as the length of a pendulum having a half-period of one second; others suggested defining the meter as one ten-millionth of the length of the earth's meridian along a quadrant (one fourth the circumference of the earth). In 1791, soon after the French Revolution, the French Academy of Sciences chose the meridian definition over the pendulum definition because the force of gravity varies slightly over the surface of the earth, affecting the period of the pendulum.

       Thus, the meter was intended to equal 10-7 or one ten-millionth of the length of the meridian through Paris from pole to the equator. However, the first prototype was short by 0.2 millimeters because researchers miscalculated the flattening of the earth due to its rotation. Still this length became the standard. (The engraving at the right shows the casting of the platinum-iridium alloy called the "1874 Alloy.") In 1889, a new international prototype was made of an alloy of platinum with 10 percent iridium, to within 0.0001, that was to be measured at the melting point of ice. In 1927, the meter was more precisely defined as the distance, at 0°, between the axes of the two central lines marked on the bar of platinum-iridium kept at the BIPM, and declared Prototype of the meter by the 1st CGPM, this bar being subject to standard atmospheric pressure and supported on two cylinders of at least one centimeter diameter, symmetrically placed in the same horizontal plane at a distance of 571 mm from each other.

       The 1889 definition of the meter, based upon the artifact international prototype of platinum-iridium, was replaced by the CGPM in 1960 using a definition based upon a wavelength of krypton-86 radiation. This definition was adopted in order to reduce the uncertainty with which the meter may be realized. In turn, to further reduce the uncertainty, in 1983 the CGPM replaced this latter definition by the following definition:

The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

       Note that the effect of this definition is to fix the speed of light in vacuum at exactly 299 792 458 m·s-1. The original international prototype of the meter, which was sanctioned by the 1st CGPM in 1889, is still kept at the BIPM under the conditions specified in 1889.

Subject: RE: BS: Gravity, meters and physics made easy
From: Amos
Date: 07 Apr 09 - 01:06 PM

Before the advent of the standard speed-of-light method, the meter was defined by a metal bar everyone agreed to use as the standard. Obviously that had a much rougher level of precision, given all those molecules moving around at the edges!


A

Subject: RE: BS: Gravity, meters and physics made easy
From: Don Firth
Date: 07 Apr 09 - 01:48 PM

Isn't there some way we can work Zeno's Paradox into this?

Don Firth

Subject: RE: BS: Gravity, meters and physics made easy
From: SINSULL
Date: 07 Apr 09 - 01:54 PM

Here you go! Obviously, the rods are not equal.
A: "Things that are equal to the same are equal to each other" (transitive property)
B: "The two sides of this triangle are things that are equal to the same"
Therefore Z: "The two sides of this triangle are equal to each other"
The Tortoise asks Achilles whether the conclusion logically follows from the premises, and Achilles grants that it obviously does. The Tortoise then asks Achilles whether there might be a reader of Euclid who grants that the argument is logically valid, as a sequence, while denying that A and B are true. Achilles accepts that such a reader might exist, and that he would hold that if A and B are true, then Z must be true, while not yet accepting that A and B are true.

The Tortoise then asks Achilles whether a second kind of reader might exist, who accepts that A and B are true, but who does not yet accept the principle that if A and B are both true, then Z must be true. Achilles grants the Tortoise that this second kind of reader might also exist. The Tortoise, then, asks Achilles to treat him as a reader of this second kind, and then to logically compel him to accept that Z must be true.

After writing down A, B and Z in his notebook, Achilles asks the Tortoise to accept the hypothetical:

C: "If A and B are true, Z must be true"
The Tortoise agrees to accept C, if Achilles will write down what he has to accept in his note-book, making the new argument:

A: "Things that are equal to the same are equal to each other"
B: "The two sides of this triangle are things that are equal to the same"
C: "If A and B are true, Z must be true"
Therefore Z: "The two sides of this triangle are equal to each other"
But now that the Tortoise accepts premise C, he still refuses to accept the expanded argument. When Achilles demands that "If you accept A and B and C, you must accept Z," the Tortoise remarks that that's another hypothetical proposition, and suggests even if he accepts C, he could still fail to conclude Z if he did not see the truth of:

D: "If A and B and C are true, Z must be true"
The Tortoise continues to accept each hypothetical premise once Achilles writes it down, but denies that the conclusion necessarily follows, since each time he denies the hypothetical that if all the premises written down so far are true, Z must be true:

"And at last we've got to the end of this ideal race-course! Now that you accept A and B and C and D, of course you accept Z."
"Do I?" said the Tortoise innocently. "Let's make that quite clear. I accept A and B and C and D. Suppose I still refused to accept Z?"
"Then Logic would take you by the throat, and force you to do it!" Achilles triumphantly replied. "Logic would tell you, 'You can't help yourself. Now that you've accepted A and B and C and D, you must accept Z!' So you've no choice, you see."
"Whatever Logic is good enough to tell me is worth writing down," said the Tortoise. "So enter it in your note-book, please. We will call it
(E) If A and B and C and D are true, Z must be true.
Until I've granted that, of course I needn't grant Z. So it's quite a necessary step, you see?"
"I see," said Achilles; and there was a touch of sadness in his tone.
Thus, the list of premises continues to grow without end, leaving the argument always in the form:

(1): "Things that are equal to the same are equal to each other"
(2): "The two sides of this triangle are things that are equal to the same"
(3): (1) and (2) ⇒ (Z)
(4): (1) and (2) and (3) ⇒ (Z)
…
(n): (1) and (2) and (3) and (4) and ... and (n − 1) ⇒ (Z)
Therefore (Z): "The two sides of this triangle are equal to each other"
At each step, the Tortoise argues that even though he accepts all the premises that have been written down, there is some further premise (that if all of (1)–(n) are true, then (Z) must be true) that he still needs to accept before he is compelled to accept that (Z) is true.

Subject: RE: BS: Gravity, meters and physics made easy
From: GUEST,TIA
Date: 07 Apr 09 - 02:05 PM

Careful! The gravitational constant is in fact constant. The strength of the Earth's field does vary from place to place and certainly with altitude.

The constant (big G) = 6.67428 +/- 0.00067 x 10^-11 m^3/kg s^2
The Earth's field strength (little g) can vary a lot (well, okay, by about 0.008 percent), but quite measurable.

JPL's GRACE map of Earth's gravity variations is here:

http://www.jpl.nasa.gov/news/news.cfm?release=2003-103

Subject: RE: BS: Gravity, meters and physics made easy
From: Mrrzy
Date: 07 Apr 09 - 02:58 PM

SOMEbody's been reading Godel Escher Bach!

I still think that redefining the meter to make physics easier is a good idea, especially now that we see how they came UP with the meter that we use as a meter.

Leave miles alone, though. We like being kinky here in the USA...

Subject: RE: BS: Gravity, meters and physics made easy
From: Donuel
Date: 07 Apr 09 - 03:14 PM

The above explanations do not sound EASY?!

A fixed distance? an inalterable constant? They are ideal models that are more of an idea than a fact.


A meter is whatever we consentually agree upon at a particular time and place on Earth.

Given that:
Gravity probably has distinctly different strengths depending upon what dimension you are in.
Light will move through certain forms of matter at different speeds yet the maximum speed through sapce time will always be the same.

!!!!!!!!!!!!!!!!!
Space can do what ever it damn well pleases whether it is to expand, condense or bend.!!!!!!!!!!!!!!!!

Whatever measurement you make on our scale of the universe, it will always be relative.

Some parts of the universe are already moving at faster than the speed of light relative to our planet.

Things are pretty fixed in the same locality but the rules get flexsible depending upon distance speed and space time dimensions.

Its not that we are bending the rules but rather that the rules bend depending upon what is acting upon them at a particular relative speed, scale, mass, form of energy and dimension it resides... as well as all the changes that are happening in the cosmos be they known or unknown to us.

I suppose it is easy to say a meter is always the same unless you are comparing it to another meter in motion elsewhere where it is always different.

Subject: RE: BS: Gravity, meters and physics made easy
From: Sorcha
Date: 07 Apr 09 - 04:27 PM

Thank you all so very much. You have set my mind at ease.

Subject: RE: BS: Gravity, meters and physics made easy
From: MaineDog
Date: 07 Apr 09 - 05:05 PM

a meter is rougly approximate to two cubits. this would allow us to measure longer distance, counting on fingers and toes.
MD

Subject: RE: BS: Gravity, meters and physics made easy
From: VirginiaTam
Date: 07 Apr 09 - 05:18 PM

Physics made musical.

Meter or metre is number of beats to the bar as in rhythm?

Grave is when a movement or entire composition is played very slow and serious.

Subject: RE: BS: Gravity, meters and physics made easy
From: VirginiaTam
Date: 07 Apr 09 - 05:27 PM

What? Too heavy?

Subject: RE: BS: Gravity, meters and physics made easy
From: Micca
Date: 07 Apr 09 - 05:59 PM

VT, Graves is a dry white wine from the Bordeaux region which should be consumed and savoured slowly aith suitable food.

Subject: RE: BS: Gravity, meters and physics made easy
From: frogprince
Date: 07 Apr 09 - 09:24 PM

Graves is holes which you don't get out of.

Subject: RE: BS: Gravity, meters and physics made easy
From: Bill D
Date: 07 Apr 09 - 10:37 PM

"SOMEbody's been reading Godel Escher Bach!"

ummm... yeah...me... that don't mean I can take it all in yet. I even bought his NEXT book ("Metamagical Themas"to whet my appetite, but it is harder yet. MY mind gasps and wonders at a mind which can conceive & construct such concepts.

Subject: RE: BS: Gravity, meters and physics made easy
From: GUEST,TIA
Date: 07 Apr 09 - 11:36 PM

Tangent:

I am always amused by the statement that "evolution is only a theory." Because, in the same sense, one could also say that "gravity is only a theory" - and the theory of gravity is really poor and incomplete. But, if you drop a spork, it will still fall.

Subject: RE: BS: Gravity, meters and physics made easy
From: VirginiaTam
Date: 08 Apr 09 - 03:05 AM

Yes but if there are no other wood or plastic eating utensils in the vicinity of that falling spork, does it make a sound?

Is that sound musical?

If it bounces can the metre be replicated.

Can you dig a grave with a spork?

Subject: RE: BS: Gravity, meters and physics made easy
From: frogprince
Date: 08 Apr 09 - 10:15 AM

"Can you dig a grave with a spork?" Thgeoretically, yes; as in:

One evening when Ole and Lena were courting, they sat down on the couch. Both being rather timid, they initially sat as far apart as possible. After awhile, though, Lena moved halfway over toward Ole.
Encouraged, Ole moved halfway over toward Lena. They continued in this manner. Theoretically, they never came in contact...

Subject: RE: BS: Gravity, meters and physics made easy
From: Amos
Date: 08 Apr 09 - 10:34 AM

There are two very different definitions of the word "theory"--the common and the scientific. Only in the former does the expression "only a theory" have any meaning.

A

Subject: RE: BS: Gravity, meters and physics made easy
From: Mrrzy
Date: 08 Apr 09 - 11:49 AM

In other words, it has no meaning in English!

Subject: RE: BS: Gravity, meters and physics made easy
From: Amos
Date: 08 Apr 09 - 01:45 PM

WHich--the word? It has two (actually more). The scientific meaning of the word doesn't marry up to the adjective "only" in any sensible way, is all I was remarking.


A

Subject: RE: BS: Gravity, meters and physics made easy
From: robomatic
Date: 14 Apr 09 - 10:21 PM

This thread is just begging for a reference to Professor Walter Vonder Wogelweide's "Short History on the Universe" (aka Severn Darden's "Metaphysics Lecture" one of the funniest things ever performed (1961)

Subject: RE: BS: Gravity, meters and physics made easy
From: mrdux
Date: 15 Apr 09 - 12:28 AM

"Of course fish think. . . but not fast enough."

Subject: RE: BS: Gravity, meters and physics made easy
From: Naemanson
Date: 15 Apr 09 - 08:42 AM

I recently learned about the attasecond. This is the length of time it take a pulse of light to travel the length of three hydrogen atoms. Pretty fast.

Subject: RE: BS: Gravity, meters and physics made easy
From: Amos
Date: 15 Apr 09 - 09:02 AM

Fast as light. But the attosecond is not fast, just short.


A

Subject: RE: BS: Gravity, meters and physics made easy
From: Mrrzy
Date: 15 Apr 09 - 10:50 AM

Attasecond, you go, time!

Subject: RE: BS: Gravity, meters and physics made easy
From: Doug Chadwick
Date: 15 Apr 09 - 01:12 PM

Alternatively, you could leave the metre alone and redefine the second to give the acceleration due to gravity as 10 m/s/s.

Anyway, it would only give a nice round number in the SI system. With different units, 10 metres per second squared could be thought of as 72731853972.7989 furlongs per fortnight per fortnight.

DC

Subject: RE: BS: Gravity, meters and physics made easy
From: Amos
Date: 15 Apr 09 - 02:33 PM

WIkipedia offers:

An attosecond is one quintillionth of a second[1]. To put this in perspective, one attosecond is to one second what one second is to the age of the universe[2][3]. The word attosecond originates from the Danish word for eighteen (atten)[4].


    * 1 attosecond is the time it takes for light to travel the length of three hydrogen atoms.[5]
    * 1 attosecond (1 as) – estimated time it takes for an atomic nucleus to recoil[5]
    * 24 attoseconds – the time taken for an electron to travel from one side of a hydrogen atom to the other[6].
    * 80 attoseconds – the shortest pulses of laser light yet created[7]
    * about 100 attoseconds – record for shortest time interval measured as of February 2004[8]
    * about 200 attoseconds – half-life of beryllium-8, maximum time available for the triple-alpha process for the synthesis of carbon and heavier elements in stars[5].
    * 150 attoseconds is the time it takes for an electron to circle the nucleus of an atom.[2][9]
    * 320 attoseconds – estimated time it takes electrons to hop between atoms[10] ...