Space HELP! - Metre? Oo (1 Viewer)

[Juggernaut K96]

Hi BoSer's,

I'm having a dilemma with understanding this concept of 'metre'. Does it mean a measurement unit or something to do with time?. I have the notes in front of me but I still don't understand.

Can someone break it down for me? Its pg: 44 on the syllabus. I'm unclear with what it has to do with the 'metre standard' or 'length standards'.

Confused,

The Juggernaut

 

[jazzzod]

Metre Definition | Definition of Metre at Dictionary.com

 

[kaz1]

Becuase of the discovery of length dilation, the length of an object could no longer be regarded as constant. So the old definition of the metre needed to be scrapped (something to do with Paris) and the new definition is the distance light travels in a very small amount of time (can't remember the exact time) since we can always rely on the speed of light to be constant.

 

[jet]

The metre is a measurement unit.

The reference to time is due to the fact that the metre is now defined as the distance light travels in 1/299792458 of a second.

As you would know, in relativity the speed of light is constant, so it provides the best definition of a unit of length.

The previous length standards were based on the platinum-iridium pole and the wavelength of krypton-83, both of which were no longer constant within the confines of Relativity (due to length contraction as kaz1 said).

 

[Juggernaut K96]

Hmm... perfect response's guys. Thanks heaps! (Y)

 

[Spark_Coaching]

The metre was first defined in 1793 as one ten-millionth of the length of the Earth's quadrant passing through Paris. When SI of units was set up (1875), metre was defined as the distance between two lines inscribed on a single bar of platinum-iridium alloy.

Current definition is much more precise: metre is the length of path travelled by light in 1/299792458th of a second (this definition takes advantage of the constancy of c).