A fundamental limit on observation

I got hooked on amateur astronomy at the age of 16 when I bought my first pair of binoculars. Thankfully I still have them and they are in very good nick. I gave them to my nine-year-old son last night and pointed him in the direction of Jupiter which can be seen low in the north-west sky soon after sunset. Anyway, one of the books I am currently reading is Seeing Further: The Story of Science and the Royal Society. It contains a paper by Paul Davies in which he writes:

“…each new advance in astronomy has unveiled a universe even larger and more majestic then previously realised, but with instruments like the Hubble Space Telescope we are approaching a fundamental limit due to the speed of light. When we see a galaxy 12 billion light years away, we see it as it was 12 billion years ago. Light can have travelled at most 13.7 billion light years since the big bang, so if that explosive event represented the true origin of the universe, then there is an ultimate horizon beyond which we cannot see. That does not mean the universe comes to an end there, any more than a horizon at sea signals the edge of the world. But it does mean we cannot directly observe what lies beyond.”

Limit or no, I just love scientists and how they have helped unveil so much of the universe. Remember that a hundred years ago, human beings thought that our Milky Way was the universe, until scientists pointed out that our galaxy was just one of perhaps a hundred billion galaxies in the universe. Just awesome.

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