We have all taken advantage of a warm summer night, far away from the lights of the city, to stretch out on our backs and contemplate the wonder of the star-filled sky; this immense universe where our sun is but a tiny pinhead among billions and billions of other such objects. We consider the miracle of ourselves: a miniscule collection of matter that is able to think and dream, with a role to play in this concerto of the stars. And we know that all that matter, even the infinitely small part that each of us represents, probably has the same origin. The Universe is one!
We have succeeded in giving it an age. The universe is 14 billion years old, three times as old as the Earth! It was born out of an extraordinary event, almost beyond the scope of our human brains to imagine: the Big Bang. The entire universe, as it exists now, gathered into a single microscopic point that suddenly expanded at fantastic speeds, hurling unimaginable quantities of matter and energy in every direction. And, after that colossal expansion, which is still going on, finishing up with what we observe in the sky today: some 100 billion galaxies, each containing several tens of billions of stars; and all those galaxies are inexorably moving away from one another. |