A aritmética do tempo

Clearly, any real body must have extension in four directions: it must have Length, Breadth, Thickness, and Duration. But through a natural infirmity of the flesh, which I will explain to you in a moment, we incline to overlook this fact. There are really four dimensions, three which we call the three planes of Space, and a fourth, Time. There is, however, a tendency to draw an unreal distinction between the former three dimensions and the latter, because it happens that our consciousness moves intermittently in one direction along the latter from the beginning to the end of our lives.

The Time Machine, H. G. Wells

Já agora, aproveito para recomendar a minha última descoberta em sites que desponibilizam livros gratuitamente:

Project Gutenberg (www.gutenberg.org)

E não se esqueçam que continua a existir este em português (referido aqui):

Domínio Público (www.dominiopublico.gov.br)