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  1. 1. DINOSAURZ this talk is about dinosaurs
  2. 2. this was a favorite movie when i was little. i was hugely into dinosaurs.
  3. 3. my little sister was too, although a different kind
  4. 4. but i think we’re all quite fascinated with dinosaurs, especially as kids. perhaps its the mystery behind them. at some point they disappeared leaving only fossils. the extinction itself was quite intriguing and mysterious
  5. 5. its worth noting mass extinctions are somewhat common in the history of the planet
  6. 6. there have been 5 major mass extinctions in the past 500 million years
  7. 7. dinosaurs were just the most recent
  8. 8. we’re talking millions of years -- the earth is some 4.5 billion years old
  9. 9. even dinosaurs are still recent developments in our planet’s story. but they died -- how?
  10. 10. common theory is a meteor hit the earth and they died as a result
  11. 11. some say it was just an unstable earth and volcanic activity slowly drove them to extinction
  12. 12. some say it was smoking
  13. 13. but what if it were something else? scientific knowledge can be surprisingly based on popular opinion. during the early 90s, the comet theory was very popular, and it just become the de facto theory. in the early 90s there was another theory, a more complex theory, but a better theory -- unfortunately it was dismissed in the hype of the comet theory.
  14. 14. all theories about this extinction are based on this white strip that shows up 65 million years ago all around the world
  15. 15. its called the kt boundary. it represents “the event” -- basically, before this you find dinosaur fossils. after it, you don’t. so what happened! our theory starts with ...
  16. 16. plant life. you see, before the kt boundary, there was no deciduous plantlife. it was all evergreens... the fossil record shows this. yet it hasn’t come up in any common theory about what happened.
  17. 17. after the kt boundary there were seasonal plants. out of nowhere! were there no seasons before the kt event? well what are seasons...
  18. 18. seasons are the result of the earth rotating around the sun and its axial tilt. without tilt, our climate would remain fairly consistent around the sun -- so was there no tilt? that’s a pretty major change... perhaps more significant than a bunch of animals dying... so that’s interesting, what could have caused a tilt?
  19. 19. the answer is in our oceans. 3/4 of our planet is covered in water. only 1/4 is land... but its all land without water -- why is only 1/4 sticking out? in the 1900’s one scientist noted “its as if we’re missing 3/4 of our continental crust.”
  20. 20. what’s even more interesting is that during the 1980’s oilers surveyed the ocean floors and they were able to date how old they were: 65 million years old. are we actually *missing* a huge chunk of our planet’s surface? where would it have gone?
  21. 21. now i’m going to talk about the moon.
  22. 22. based on material found on the moon, we’ve dated it back to about as far as the earth itself -- certainly well before dinosaurs. although its worth noting that if it was made out of material from earth, it would of course date back as far as earth. so wait, where did the moon come from?
  23. 23. it’s about as uncertain as the dinosaur extinction. this shows a popular theory. i’m not sure why it dances there, but something hit the earth and fell into orbit. simple, right? simple, like the comet theory -- in fact, you might be putting those two together...
  24. 24. but you’d be wrong. i’m trying to say the moon came from the earth, not from a comet. in fact, it *is* that missing 3/4 of continental crust. sound crazy? let’s just run some numbers...
  25. 25. Volume: ~22 billion km3 wikipedia
  26. 26. Water area: ~361 million km2
  27. 27. 60 km we include the bottom of the lithosphere as well, which is a significant point. it’s much heavier and less interesting than the crust.
  28. 28. Water area: Water area: 361 million km2 2 Lithosphere: Lithosphere: 60 km
  29. 29. Water area: Water area: 361 million km2 2 Lithosphere: Lithosphere: 60 km ~22 billion km3 22
  30. 30. Water area: 361 million km2 Lithosphere: 60 km ~22 billion km3 22 Moon: ~22 billion km 3 when you run the actual numbers they fall within 1% of each other. and this wasn’t even brought up in the original paper, i just thought it would be interesting to look up. sure enough, the numbers fit.
  31. 31. Orbital inclination: ~23 degrees perhaps another thing worth mentioning, while looking up numbers, the moon rotates
  32. 32. Axial tilt: ~23 degrees at the same inclination as our axial tilt. OK, so *how* did all this happen?
  33. 33. that matter formed into a sphere, as it does, and fell into orbit, trapped by our gravity (btw, its slowly getting farther away). as it turns out the sphere formed with the heavier material at the bottom, facing us. this is why it always faces us, it’s heavier on one side. it’s that lower part of the lithosphere.
  34. 34. the remaining 1/4 crust remained, and to balance the earth’s rotation it slowly spread out
  35. 35. to the geography we know today. it’s balanced. look at it, it’s all quite evenly distributed.
  36. 36. so that’s the moon story.
  37. 37. which is really just the earth story. it’s how the earth matured and stabilized. perhaps its something all planets go through.
  38. 38. anyway, i said this was about dinosaurs. so yes, *obviously* this crazy event *must* have been drastic enough to cause all sorts of dangerous changes to the planet to kill lots of animals... but why the dinosaurs?
  39. 39. well theres something curious about dinosaurs. they were big. we’ve never seen a land animal that comes close to the largest dinosaurs.
  40. 40. our biggest land animals as far as mass are maybe elephants.
  41. 41. whats more is we have records of 6 foot long dragonflies. 6 feet! we’ve made models of these and even when we try we can’t get them to fly. it’s as if something was different then. how were these huge things moving? from their size we imagine big slow lumbering animals, but we know many were fairly birdlike, light and agile. how??
  42. 42. Gravity less gravity. during that cool-down phase (over billions of years?) as the crust moved outward, the same centrifugal force was countering gravity. t-rex was actually as light for its size as say, a chicken. that’s how they could evolve so large.
  43. 43. Gravity that’s also how they died. if they weren’t killed from whatever went on as we *lost* crust, they were crushed as the planet slowed and stabilized.
  44. 44. 3/4 of the earth’s surface though... up there. there *were* dinosaurs on it, and if this is all true, there may be dinosaur fossils on the dark side of the moon.
  45. 45. perhaps the most validating part of this theory is how complex it is. there’s a well respected heuristic for judging explanations in the scientific community: the less that can change in it, the more valid it likely is. greek explanations of seasons based on drama with the gods, the story can be told so many different ways to have the same result of some god leaving and returning every year. whereas, if you changed any part of this theory, it all falls apart.
  46. 46. The end
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