We know that the Universe is expanding, but theories regarding its future are controversial. Will it continue to exist or will it vanish? Its fate depends on the amount and properties of the matter it contains. In other words, in order to determine the future of the Universe, we must first... weigh it! An extremely daunting prospect.

Nevertheless, efforts have already revealed a great surprise: there is much more 'out there' than telescopes can detect. An invisible 'substance' dramatically alters the weight of the Universe and affects its behavior. Could this be the 'Quintessence' of Aristotle? Where is this 'dark matter' hiding?

Physicist Lawrence Krauss presents the most astonishing discovery of our century: fluctuations in quantum vacuum produce energy. Throughout the vastness of intergalactic abyss, energy multiplies, shapes gravity accordingly, and determines the fate of the Universe. Empty space is the creator of an otherworldly energy, managing mass and steering Cosmic evolution.

Aristotle describes the celestial material that adds to earth, air, fire, and water (the four known elements of the World) as 'fifth essence'. Aristotle's 'quintessence' was the ether, the substance believed - until the nineteenth century - to permeate empty space. A decade ago, dark matter seemed to be a kind of modern 'quintessence'.

Today, following the spirit of Aristotle concerning celestial ether, we would say that the 'quintessence' of the Universe is the energy produced by quantum vacuum - it is the incredible process where particles are born from nothing and - on the scale of the macrocosm - determine the future that awaits our Universe.

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