Distance light travels in a given time

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Defining the meter based on the distance light travels in a given time offers significant advantages over using a physical metal bar. The speed of light in a vacuum is a constant, ensuring uniformity and accuracy across measurements, while a metal bar can change dimensions due to factors like thermal expansion. Additionally, light-based measurements can be utilized in various applications, such as interferometry, enhancing precision. This method eliminates the limitations associated with physical standards, leading to more reliable and reproducible results. Overall, using light for measurement provides a more stable and versatile approach.
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Please Help!

Explain the advantages in having the meter offically defined in terms of the distance light travels in a given time rather than as the length of a specific metal bar

Is it becasue in terms of light is more accurate?
 
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Well, I can think of many reasons:
First, the speed of light in a vacuum is everywhere the same. The dimensions of a metal bar can change through thermal extension for example and it it impossible to machine something that is exactly 1.000000000000" or even more acurate.
Second, you can use light to actually meassure a lot of different things like in a interferometer
 
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Thank you!
 
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