If you use the ruler to directly measure the distance between subsequent points, the random temperature fluctuations will be as likely to increase as decrease the measured distance (of course for a real steel ruler, this would be dominated by the systematic error in the ruler&#x27;s markings, which will accumulate over summed measurements).<p>If instead you used the ruler to measure (X, Y) co-ordinates of each point, then calculated the displacement between the points from those co-ordinates, the random errors would have a bias towards lengthening the path as in the article.