Eli5 : Why do we define metre as length of path of light in vaccum during a time interval of 1/299,792,458 of a second ?

Question

Why not 1/300,000,000 or something different constant ( why only light ) ?

In: Physics

Answer 1

i think the length was defined earlier than it’s scientific explanation so to not mess up like all of the world by changing a meter by a small amount, they just used the exact time to travel the OG meter