A Platonic Philosopher living during the Golden Age of Athens would have argued that one cannot deduce the true nature of the universe by trusting the senses. The senses lie, he would have said. Only the use of reason and the insight of the human mind can lead us to true understanding.

Those methods, valid in their own context, are not the methods of science, nor do they produce the kinds of advanced technologies and the knowledge we associate with modern societies. We need to differentiate between observation, in which we observe nature without manipulating it, and experiments, in which we manipulate some aspects of nature and observe the outcome. An astronomer, for example, observes distant stars without changing them, while a chemist experiments by mixing materials together and sees what happens.

Try your first Measurement:

Measure the frequency of your heart beat