It now seems that our entire universe is living on borrowed time. How long it can survive depends on whether Stephen Hawking's theory checks out. Special thanks to Ivan Bridgewater for use of footage. Time is flying by on this busy, crowded planet... as life changes and evolves from second to second. And yet the arc of human lifespan is getting longer: 65 years is the global average ... way up from just 20 in the Stone Age. Modern science, however, provides a humbling perspective. Our lives... indeed the life span of the human species... is just a blip compared to the age of the universe, at 13.7 billion years and counting. It now seems that our entire universe is living on borrowed time... And that even it may be just a blip within the grand sweep of deep time. Scholars debate whether time is a property of the universe... or a human invention. What's certain is that we use the ticking of all kinds of clocks... from the decay of radioactive elements to the oscillation of light beams... to chart and measure a changing universe... to understand how it works and what drives it. Our own major reference for the passage of time is the 24-hour day... the time it takes the Earth to rotate once. Well, it's actually 23 hours, 56 minutes and 4.1 seconds... approximately... if you're judging by the stars, not the sun. Earth acquired its spin during its birth, from the bombardment of rocks and dust that formed it. But it's gradually losing that rotation to drag from the moon's gravity ...
