- #1

TRB8985

- 74

- 15

- TL;DR Summary
- Is the meter defined only by the speed of light, or is it tied to deeper and more fundamental constants like the permittivity and permeability of free space?

Good evening all,

I had a question on how the standard for the meter is defined. A simple Google search tells us that since 1983, the meter has been internationally defined as the length of the path traveled by light in vacuum during a time interval of 1 / 299, 792, 458 of a second. Many other sources agree with this, directly tying the definition of the meter to only the speed of light.

From my electrodynamics course, I remember that the speed of light is equal to the following:

## c = \frac{1}{\sqrt {\epsilon_0 * \mu_0}} ##

If the meter is defined in terms of c, and the above equation is true, wouldn't that really mean that the meter is more fundamentally defined in terms of the permittivity and permeability of free space? Hopefully that question makes some sense.

Thanks for your time!

I had a question on how the standard for the meter is defined. A simple Google search tells us that since 1983, the meter has been internationally defined as the length of the path traveled by light in vacuum during a time interval of 1 / 299, 792, 458 of a second. Many other sources agree with this, directly tying the definition of the meter to only the speed of light.

From my electrodynamics course, I remember that the speed of light is equal to the following:

## c = \frac{1}{\sqrt {\epsilon_0 * \mu_0}} ##

If the meter is defined in terms of c, and the above equation is true, wouldn't that really mean that the meter is more fundamentally defined in terms of the permittivity and permeability of free space? Hopefully that question makes some sense.

Thanks for your time!