                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                                 2024 July 1
    An illustrated spiral is shown depicting many significant events that
   have occurred since the big bang. The big bang is at the center, and a
   city built by humans is at the spiral's end. Please see the explanation
                       for more detailed information.

                                 Time Spiral
           Illustration Credit: Pablo Carlos Budassi via Wikipedia

   Explanation: What's happened since the universe started? The time
   spiral shown here features a few notable highlights. At the spiral's
   center is the Big Bang, the place where time, as we know it, began
   about 13.8 billion years ago. Within a few billion years atoms formed,
   then stars formed from atoms, galaxies formed from stars and gas, our
   Sun formed, soon followed by our Earth, about 4.6 billion years ago.
   Life on Earth begins about 3.8 billion years ago, followed by cells,
   then photosynthesis within a billion years. About 1.7 billion years
   ago, multicellular life on Earth began to flourish. Fish began to swim
   about 500 million years ago, and mammals because walking on land about
   200 million years ago. Humans first appeared only about 6 million years
   ago, and made the first cities only about 10,000 years ago. The time
   spiral illustrated stops there, but human spaceflight might be added,
   which started only 75 years ago, and useful artificial intelligence
   began to take hold within only the past few years.

                Explore Your Universe: Random APOD Generator
                      Tomorrow's picture: oyster stars
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       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Amber Straughn Specific rights apply.
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                           NASA Science Activation
                             & Michigan Tech. U.

