Most people who've studied a little science know that our universe is expanding. Everything in the universe is moving away from everything else. <br /><br />
Eventually, millions of years from now, the stars in the night sky will have moved so far away, and be receding at such enormous speed, that the light from them will not be able to reach earth.<br /><br />
In fact, the current era is the optimal time in the history of the universe for studying the heavens and figuring out how it all came to be. If humans had appeared on earth significantly sooner than they did the night sky would've been so bright (because all the galaxies would've been much closer together) that it would've been impossible to study the heavens.<br /><br />
If humans had appeared significantly later in the universe's history the universe would've been so dark and thinly populated by galaxies that are knowledge of it would've been considerably less.<br /><br />
Likewise, earth is located at the optimal place in the Milky Way galaxy. It's situated in the galactic plane which means that it's shielded by gas, dust and stars from the lethal radiation emanating from the center of the galaxy.<br /><br />
If it were much closer to the center the radiation would make life impossible. If it were further from the center it would not have access to a rich supply of heavier elements that are necessary for life.<br /><br />
Earth is also positioned between spiral arms of the galaxy which means humans have a relatively unobstructed view of the heavens, allowing for scientific discovery and thus the development of technology.<br /><br />
For instance, because humans could see the stars they could navigate the seas which allowed for exploration and discovery.<br /><br />
But back to the expanding universe. What's causing the expansion appears to be something called dark energy. If dark energy were just a little bit weaker the universe would long ago have collapsed back on itself, and life would've been impossible.<br /><br />
If dark energy were a just a little bit stronger the universe would've long ago gone dark and life would likewise be impossible.<br /><br />
The strength of the dark energy is just right to produce a universe that during part of its existence can support life, but what do we mean by "just right"?<br /><br />
It turns out that the dark energy is fine-tuned to a precision of one part in 10^120 for life to be possible somewhere and at some time in the universe. This is an unimaginably exquisite setting.<br /><br />
If we think of this energy in terms of mass the dark energy could not deviate from its actual value by more than the the mass of a billionth of a trillionth of a trillionth of the mass of an electron.<br /><br />
We are either very, very lucky or we're the product of an intentionally engineered cosmos.<br /><br />
Back in 1979, before scientists had discovered dark energy and just beginning to discover the dozens of other examples of cosmic fine-tuning, physicist Freeman Dyson observed that,<br /><br />
The more I examine the universe and study the details of its architecture, the more evidence I find that the universe in some sense must have known we were coming.