You are probably asking yourself why are measurements so important in physics?  Your chemistry and physics teachers or professors seem to really get worked up over these significant digit things. Why is that?

Models in Physics

In physics, almost every concept has a corresponding equation.  This equation is considered to be the model of the behavior.  It is a way of very concisely stating how all of the variables interact with each other.  In some cases, especially when a new theory is introduced, there might be two competing models.  Often these models predict very similar behavior, with just tiny differences between them.

Good measurements can help us tell the difference between the models and help us decide which of the two models is better at predicting things.

Comparing Models:  The Eclipse of 1919

One of the most famous cases of competing models involves Einstein’s theory of general relativity.  Einstein predicted that the path of light passing near a massive object can actually be bent, even though light is massless.  If you have seen movies like Interstellar, the funky patterns of light near the black hole are caused by this gravitational bending of light.  There aren’t any black holes near the Earth, but the Sun is fairly massive.

Einstein predicted that light (from distant stars) passing near the sun would be bent by a few degrees.  Normally, we can’t see these stars because the sun is so bright.  However, during an eclipse, the moon passes in front of the sun.  In much the same way you hold up your hand to block out a bright light to see objects near it, an eclipse gives us a chance to see stars located near the sun.  If we compare a photograph of stars near the sun during an eclipse to a photograph from later in the year when the sun is in a different part of the sky, we can check these predictions.

Astronomers gathered sufficiently detailed photographs and careful measurements.  They used these to show that Einstein’s model’s prediction was correct.  You can read more details in this Forbes article:  How a Solar Eclipse First Proved Einstein Correct.

The big idea is that good measurements were necessary to test the prediction.

Why are measurements so important in physics class?

In your physics class, you most likely won’t be testing a major new hypothesis.  However, you should take measurements as carefully as you can.  If you go on to become a scientist, you will take measurements often.  You want these measurements to help support your theories.

If you are not a scientist, measurements still matter.  Will your clothes fit?  Is your car or house going to fall apart?  Are the recommendations from your doctor trustworthy?

This mini-course will help you take good measurements in your physics and other science classes.  Good luck.