physics - definition of a metre (1 Viewer)

[jnney]

Discuss the concept that length standards are defined in terms of time in contrast to the original metre standard.

SO CONFUSED!

 

[OmmU]

Originally, a metre was defined as 1/10,000,000th of the circumference of the Earth, and then later as the distance between two lines on a platinum-iridium bar, which provided the standard measure of a metre. However, today the metre is defined as the distance light travels in 1/299792458 seconds. This means that distance is calculated based on time- a unit of distance is measured in terms of how much distance light travels in a period of time. A light-year is another distance measured by time,and it is the distance light travels in one year.

Reference: HSC Students guide to physics

 

[Sanical]

Lol, isn't it obvious?..
According to special relativity, speed of light is constant by all observers. So no matter where you are, even on another planet, the unit metre can always be measured. It is also much more accurate.
The old one where it was 1/10000000th of the circumference of the earth is not accounted for everywhere. It's even subjected to change - as the earth wears and such. This is obviously not as accurate as the recent definition.

As it is a discuss it’s also good to have a disadvantage. The disadvantage is that time dilation occurs at high velocities, thus time can differ, meaning the definition does not account for high speed travel.