Video Transcript
Is the meter defined as being the
length of a specific object?
This question is asking us about
the definition of the meter. The meter is the SI base unit of
length. And we know that lengths are often
measured in units of meters. For example, a person might be 1.7
meters tall, or a racetrack might be 100 meters long. But what is a meter? How did scientists decide exactly
how long a meter was? This question suggests that a meter
was perhaps defined as being the length of a particular object. Let’s make sure we understand what
this means.
We know that there are some objects
that are a meter long, for example, meter rulers. However, these objects were
designed to be one meter long, after the unit of meters had already been
defined. The meter itself was not defined by
the length of these objects. This question is suggesting that
scientists came across some specific object, say, a rod of some kind. They then decided to call the
length of this object one meter and designed a whole measurement system around the
length of the object.
However, this is not the case. This would be a very difficult way
to define the meter. Imagine if the object was
accidentally damaged and its length changed. We would then have to recalculate
all the lengths that we’ve already measured. The meter is actually defined using
a natural physical phenomenon, the speed of light. The meter is defined as the
distance that light can travel in a particular amount of time. This distance does not change, as
the speed of light in a vacuum does not change. Its value is constant. That makes this a good method of
defining the meter.
So, the answer to this question is
no; the meter is not defined as being the length of a specific object.
