Astronomy Picture of the Day [1]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 [2]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: [3]Pablo Carlos Budassi via [4]Wikipedia Explanation: What's happened since the universe started? The time spiral [5]shown here features a few [6]notable highlights. At the spiral's center is the [7]Big Bang, the place where [8]time, as we know it, began about 13.8 billion years ago. Within a few billion years [9]atoms formed, then [10]stars formed from atoms, [11]galaxies formed from stars and gas, [12]our Sun formed, soon followed by [13]our Earth, about 4.6 billion years ago. [14]Life on Earth begins about 3.8 billion years ago, followed by [15]cells, then [16]photosynthesis within a billion years. About 1.7 billion years ago, [17]multicellular life on Earth began to flourish. [18]Fish began to swim about 500 million years ago, and [19]mammals because walking on land about 200 million years ago. [20]Humans first appeared only about 6 million years ago, and made the [21]first cities only about 10,000 years ago. The time spiral illustrated stops there, but human [22]spaceflight might be added, which started only 75 years ago, and useful [23]artificial intelligence began to take hold within only the past few years. Explore Your Universe: [24]Random APOD Generator Tomorrow's picture: oyster stars __________________________________________________________________ [25]< | [26]Archive | [27]Submissions | [28]Index | [29]Search | [30]Calendar | [31]RSS | [32]Education | [33]About APOD | [34]Discuss | [35]> __________________________________________________________________ Authors & editors: [36]Robert Nemiroff ([37]MTU) & [38]Jerry Bonnell ([39]UMCP) NASA Official: Amber Straughn [40]Specific rights apply. [41]NASA Web Privacy, [42]Accessibility, [43]Notices; A service of: [44]ASD at [45]NASA / [46]GSFC, [47]NASA Science Activation & [48]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2407/TimeSpiral_Budassi_2500.jpg 3. https://commons.wikimedia.org/wiki/User:Unmismoobjetivo 4. https://en.wikipedia.org/wiki/Wikipedia 5. https://commons.wikimedia.org/wiki/File:Nature_timespiral_vertical_layout.png 6. https://apod.nasa.gov/apod/ap171126.html 7. https://webb.nasa.gov/content/features/bigBangQandA.html 8. https://en.wikipedia.org/wiki/Time 9. https://youtu.be/cx1z0jwzWjI 10. https://science.nasa.gov/universe/stars/ 11. https://apod.nasa.gov/apod/ap230531.html 12. https://science.nasa.gov/sun/ 13. https://science.nasa.gov/earth/facts/ 14. https://cneos.jpl.nasa.gov/about/life_on_earth.html 15. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7087693/ 16. https://en.wikipedia.org/wiki/Photosynthesis 17. https://astrobiology.nasa.gov/news/how-did-multicellular-life-evolve/ 18. https://youtu.be/t6ORDd4ZpXg 19. https://en.wikipedia.org/wiki/Mammal 20. https://apod.nasa.gov/apod/ap190818.html 21. https://youtu.be/H1jHdnZ2U3o 22. https://apod.nasa.gov/apod/ap181001.html 23. https://media.snopes.com/2009/01/rand.jpg 24. https://apod.nasa.gov/apod/random_apod.html 25. https://apod.nasa.gov/apod/ap240630.html 26. https://apod.nasa.gov/apod/archivepix.html 27. https://apod.nasa.gov/apod/lib/apsubmit2015.html 28. https://apod.nasa.gov/apod/lib/aptree.html 29. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 30. https://apod.nasa.gov/apod/calendar/allyears.html 31. https://apod.com/feed.rss 32. https://apod.nasa.gov/apod/lib/edlinks.html 33. https://apod.nasa.gov/apod/lib/about_apod.html 34. https://asterisk.apod.com/discuss_apod.php?date=240701 35. https://apod.nasa.gov/apod/ap240702.html 36. http://www.phy.mtu.edu/faculty/Nemiroff.html 37. http://www.phy.mtu.edu/ 38. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 39. http://www.astro.umd.edu/ 40. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 41. https://www.nasa.gov/about/highlights/HP_Privacy.html 42. https://www.nasa.gov/general/accessibility/ 43. https://www.nasa.gov/privacy/ 44. https://astrophysics.gsfc.nasa.gov/ 45. https://www.nasa.gov/ 46. https://www.nasa.gov/centers/goddard/ 47. https://science.nasa.gov/learners 48. http://www.mtu.edu/