Here Is Another Fact of Physics From Me

[bharatiyedu]

Definition Of A Metre

 

The metre wa a unit of length was first determined in 1973 when the french government decreed it to be 1times10^-7 times the length of the warts quadrant passing through paris. The arc was surveyed and then three platinum standards and several iron copies were made. When it was discovered that the quadrant survey was incorrect, the metre was redefined as the diatance between two marks on a bar. In 1875 the systeme Internationale (SI) of units was set up so that the definition became more formal: a metre was the distance between the two lines scribed on a single bar of platinum-iridium alloy. Copies or 'artefacts'. were made for dissemination of this standard. There is always a need for accuracy of a unit of measure to keep pace with improvements in technology and science, so the metre ha sice redifined twice.

 

The current definition of metre uses the constacy of the speed of light in a vaccum (299 792 458 ms^-1) and the accuracy of the definition of one second (9 129 631 770 oscillations of the 133^Cs atom), to achieve a definition that is both highly accurate and consistent with the idea of sapce time. One metre is now defined as length of the path travelled by light in a vaccum during the time interval of 1/299 792 458 of a second.

 

The term 'light year' is a similar distance unit, being the length of the path travelled by light in a time travel of one year. One light year is approximately equal to 9.46728times10^12 Km

[swansont]

Definition Of A Metre

 

The metre wa a unit of length was first determined in 1973 when the french government decreed it to be 1times10^-7 times the length of the warts quadrant passing through paris. The arc was surveyed and then three platinum standards and several iron copies were made. When it was discovered that the quadrant survey was incorrect' date=' the metre was redefined as the diatance between two marks on a bar. In 1875 the systeme Internationale (SI) of units was set up so that the definition became more formal: a metre was the distance between the two lines scribed on a single bar of platinum-iridium alloy. Copies or 'artefacts'. were made for dissemination of this standard. There is always a need for accuracy of a unit of measure to keep pace with improvements in technology and science, so the metre ha sice redifined twice.

 

The current definition of metre uses the constacy of the speed of light in a vaccum (299 792 458 ms^-1) and the accuracy of the definition of one second ([b']9 129 631 770[/b] oscillations of the 133^Cs atom), to achieve a definition that is both highly accurate and consistent with the idea of sapce time. One metre is now defined as length of the path travelled by light in a vaccum during the time interval of 1/299 792 458 of a second.

 

The term 'light year' is a similar distance unit, being the length of the path travelled by light in a time travel of one year. One light year is approximately equal to 9.46728times10^12 Km

 

Some (transposition?) errors: 1793, perhaps, but certainly not 1973. The survey did not account for the oblateness of the earth, due to its rotation, so the distance from the equator to the pole is not quite 10 000 km. The second is 9 192 631 770 oscillations.

[Phi for All]

I'm not sure I like this "Facts (?) of Physics Form (sic) Me" series. They don't invite much discussion, the OP doesn't respond when asked pertinent questions, and they seem to be riddled with errors and misspellings. A little more attention to detail and perhaps some dialogue-inducing comments would be appropriate in the future.

[ecoli]

I'm almost positive SI units were created after the French Revolution. After they killed the king, they couldn't use his foot as the standard anymore, so they decided to switch to something more universal.

[bharatiyedu]

i am trying this because of one of the users.

 

here is the time line of the metre

 

* May 8, 1790 — The French National Assembly decides that the length of the new metre would be equal to the length of a pendulum with a half-period of one second.

 

* March 30, 1791 — The French National Assembly accepts the proposal by the French Academy of Sciences that the new definition for the metre be equal to one ten-millionth of the length of the earth's meridian along a quadrant (one-fourth the polar circumference of the earth).

 

* 1795 — Provisional metre bar constructed of brass.

 

* December 10, 1799 — The French National Assembly specifies that the platinum metre bar, constructed on 23 June 1799 and deposited in the National Archives, as the final standard.

 

* September 28, 1889 — The first CGPM defines the length as the distance between two lines on a standard bar of an alloy of platinum with ten percent iridium, measured at the melting point of ice.

 

* October 6, 1927 — The seventh CGPM adjusts the definition of the length to be the distance, at 0 °C, between the axes of the two central lines marked on the prototype bar of platinum-iridium, this bar being subject to one standard atmosphere of pressure and supported on two cylinders of at least one centimetre diameter, symmetrically placed in the same horizontal plane at a distance of 571 millimetres from each other.

 

* October 20, 1960 — The eleventh CGPM defines the length to be equal to 1,650,763.73 wavelengths in vacuum of the radiation corresponding to the transition between the 2p10 and 5d5 quantum levels of the krypton-86 atom.

 

* October 21, 1983 — The seventeenth CGPM defines the length to be distance travelled by light in vacuum during a time interval of 1/299 792 458 of a second.

[bharatiyedu]

 

International Prototype Metre standard bar made of platinum-iridium. This was the standard until 1960, when the new SI system used a krypton-spectrum measurement as the base. In 1983 the current metre was defined by a relationship to the speed of light in a vacuum.

[Phi for All]

Now you're just copy/pasting from other websites, and not even giving them the credit. This is not your work and is a violation of the copyright laws and forum policy.

 

What I'm looking for is a discussion of the information you present, started by you as the original thread starter. Posting up facts you glean from other sources as some sort of academic course is NOT what this forum is all about.

 

If you're going to post the work of others, please give them credit and a link, and if you're going to post facts as threads then we want some comments from you that give direction to a discussion. If we wanted to learn the above facts we could just go to OnlineConversions.com.

[bharatiyedu]

there is no discussion going on so make that i posted stuff from other site to make it intresting

 

this image and time line were form wikipidea

[insane_alien]

there is no discussion because you have not provided a direction for any discussion. you have just gave a fact and said discuss. discuss what?

we could discuss the pros and cons of removing physical standards from our definition of units or we could discuss the pros and cons of have a universal standard set of units. if you want to spark a discussion you need to give us a direction otherwise its like trying to light a fire without any fuel.

[YT2095]

bharatiyedu,

 

although your intentions of pointing these facts out and sharing them with us for those that may NOT know of them is admirable, we are however a Discussion Forum, and so to start a Thread/Subject off as new withOUT inviting any sort of discourse is perceived as somewhat Odd and lacking Purpose

 

anyway, thank you non the less, I`m sure in time it will come in usefull for anyone that uses our search engine

[Ragib]

I think it is quite good what bharatiyedu is doing. Maybe the topic of a metre is when comment inducing, but other facts may be. Good work, but maybe make your posts on more surprising facts bharatiyedu.

[Forensicmad]

According to wikipedia:

"The metre is defined as equal to the length of the path travelled by light in absolute vacuum during a time interval of 1/299,792,458 of a second."

 

I think that's the most recent decision as to the proper length of the metre.

 

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

 

And also apparently, "Historically, the metre was intended to be, and is very nearly, the ten-millionth part of the distance from the equator to the north pole." - Interesting

[Ragib]

These meanings are ambiguous... The length of a metre is the length light travels in 1/299,792,458 seconds. Light travels 299,792,458 metres a second. A second is 9 192 631 770 periods of a cs 133 atom at ground state. But a period is the amount of pulses passed per SECOND. The definition of a second, involves a second!!

[swansont]

These meanings are ambiguous... The length of a metre is the length light travels in 1/299,792,458 seconds. Light travels 299,792,458 metres a second. A second is 9 192 631 770 periods of a cs 133 atom at ground state. But a period is the amount of pulses passed per SECOND. The definition of a second, involves a second!!

 

A second is 9192631770 oscillations. Period also means interval.

[Ragib]

o ok thanks for clearing that up.