Physics is the discipline that deals with the study of Nature through observation, experiments and the development of mathematical laws or principles which help understand the observed phenomena. It’s the most basic science because it studies the most basic natural phenomena, from the smallest scale of the structure of matter and the interaction between fundamental particles to the largest scale of galaxies, their origin and behavior and the origin of the universe itself.

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We call laws of Physics or physical laws the mathematical statements or rules that the observed phenomena obey. The key characteristics of these laws are two: first they describe the behavior of the physical system under study (heat transfer, interaction between celestial bodies, etc.). But most importantly, **the allow us to make predictions** about the future behavior of these systems. If we have the equations that describe the motion of a falling object, we will be able to predict where this body will be at any time. The practical application of the laws of Physics (what we call engineering) allows the development of technologies which make life better for human beings.

Every technological advance that we enjoy today is based on the knowledge that human beings have built up over centuries of inquiry, curiosity and the application of the **scientific method**.

Therefore, Physics is a very powerful discipline which allows us to understand our universe and make predictions about its future behavior. But in order to do so, we have to be very careful and precise when defining the different quantities. They cannot be ambiguous and the must serve their purpose which is help us understand the different physical phenomena.

As Galileo said, the universe cannot be read until we have learnt the language and become familiar with the characters in which it is written. It is written in mathematical language. Thus we must start learning Physics by getting familiar with the tools that will allow us to understand the different concepts and laws as well as to solve physics problems.

One of the cornerstones of science is **measurement** and more so in Physics, where precision and reproducibility are essential. Every physical quantity introduced throughout these pages will include its **units**.

We will now introduce the concepts of **scalar quantity**, **vector**, as well as a short introduction to the **International System of Units** and orders of magnitude.