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The Universe is much bigger than it is old

posted by Jason Kottke   Oct 20, 2017

In a Twitter thread, author Oliver Morton compares the physical scale of the Universe with its age (from the perspective of humans).

If a human life is 70 years long, there has been room for 200 million lives since the big bang, but 200 million humans, end to end, would reach just a bit further than the moon. If you had started walking towards the centre of the galaxy on the day of the big bang (had there been days, you, paths & galaxies), you would have got about 20 parsecs by now: just 0.25% of the way.

Maybe walking pace is the wrong metric. A nerve impulse travels around 70 times faster than a person walks. But even at the speed of thought, the age of the universe is too small for something to have reached the centre of the galaxy.

The situation is even worse when you choose another reference object, like UY Scuti, the largest known star. The red hypergiant is nearly 1.5 billion miles across and, because of its size and position near the center of the galaxy, is probably around 13 billion years old, just a few hundred million years younger than the age of the Universe itself.

Even if you use light as a marker, the size of Universe remains unfathomably immense. Over the course of the Universe’s lifetime, a photon could have travelled 13.8 billion light-years, just 15% of the current estimate of the Universe’s diameter of 93 billion light-years. See also what are the physical limits of humanity?