1 00:00:00,669 --> 00:00:05,520 I would like to tell you what we know about this event and give you an idea of what to 2 00:00:05,520 --> 00:00:07,680 expect in the future perhaps. 3 00:00:07,680 --> 00:00:10,950 So, let's get started. 4 00:00:10,950 --> 00:00:12,530 First of all, some terms. 5 00:00:12,530 --> 00:00:17,720 You can't have a talk without defining things, at least not in my field. 6 00:00:17,720 --> 00:00:20,130 Meteoroid, meteor, meteorite what's the difference? 7 00:00:20,130 --> 00:00:23,570 Well there is a difference though people use them interchangeably a lot. 8 00:00:23,570 --> 00:00:27,690 A meteoroid is a chunk of rock or ice out in space. 9 00:00:27,690 --> 00:00:31,400 It's about the size of a boulder or smaller. 10 00:00:31,400 --> 00:00:36,019 Now some people ask, "What's the difference between a meteoroid and an asteroid?" 11 00:00:36,019 --> 00:00:38,979 It's all a question of size. 12 00:00:38,979 --> 00:00:41,239 There is no dividing line. 13 00:00:41,239 --> 00:00:48,699 So, some people would say a rock, a meter across, a yard and a half across is an asteroid. 14 00:00:48,699 --> 00:00:55,229 Others would say it's got to be about 10 meters or 10 yards across before it's an asteroid. 15 00:00:55,229 --> 00:01:01,300 I prefer thinking something bigger than a garage which is 10 yards, is an asteroid. 16 00:01:01,300 --> 00:01:05,640 Something the size of a beach ball, that doesn't strike me as an asteroid, I would call that 17 00:01:05,640 --> 00:01:06,979 a meteoroid. 18 00:01:06,979 --> 00:01:08,670 So that's the difference. 19 00:01:08,670 --> 00:01:10,299 It's a question of size. 20 00:01:10,299 --> 00:01:14,960 But you will get a different answer depending on which scientist you talk to. 21 00:01:14,960 --> 00:01:17,240 So, I'm giving you my opinion. 22 00:01:17,240 --> 00:01:18,940 There is no formal definition. 23 00:01:18,940 --> 00:01:25,990 Now, when that chunk of rock and ice out in space hits our atmosphere it burns up, it 24 00:01:25,990 --> 00:01:29,009 ablates because they hit the atmosphere pretty fast. 25 00:01:29,009 --> 00:01:36,579 Most meteors move anywhere from 40 to 170,000 miles per hour, many times faster than the 26 00:01:36,579 --> 00:01:39,079 space shuttle hitting the atmosphere. 27 00:01:39,079 --> 00:01:45,119 So when they hit, they burn up, they leave that streak of light that you see as a shooting 28 00:01:45,119 --> 00:01:46,829 star, or a falling star. 29 00:01:46,829 --> 00:01:51,710 That streak of light is what we call a meteor. 30 00:01:51,710 --> 00:01:57,289 So the meteor is not the rock or the ice itself, it's the streak of light it produces when 31 00:01:57,289 --> 00:01:59,609 it burns up in the atmosphere. 32 00:01:59,609 --> 00:02:10,099 And finally, any piece of that meteoroid that makes it to the ground, we call it a meteorite. 33 00:02:10,099 --> 00:02:14,340 So a meteorite is something that has actually made it to the ground. 34 00:02:14,340 --> 00:02:19,730 And yes, the moon and Mars have meteorites on them too so it's not specific to the Earth. 35 00:02:19,730 --> 00:02:27,069 So any piece of a meteoroid that survives atmospheric ablation and makes it to the ground 36 00:02:27,069 --> 00:02:29,739 is called a meteorite. 37 00:02:29,739 --> 00:02:33,129 Any questions on that? 38 00:02:33,129 --> 00:02:40,099 So, Luther now knows the difference here. 39 00:02:40,099 --> 00:02:43,460 He got whacked by a meteorite. 40 00:02:43,460 --> 00:02:49,280 Now when it comes to meteors there's a thing called a fireball, which is a bright meteor. 41 00:02:49,280 --> 00:02:54,410 Technically, a fireball is a meteor brighter than the planet Venus. 42 00:02:54,410 --> 00:02:56,470 That's a fireball. 43 00:02:56,470 --> 00:03:01,210 And a superbolide is something that's really bright. 44 00:03:01,210 --> 00:03:03,600 It will cast shadows on the ground. 45 00:03:03,600 --> 00:03:07,349 It's generally brighter than the full moon. 46 00:03:07,349 --> 00:03:09,049 These are rather rare. 47 00:03:09,049 --> 00:03:14,400 Superbolides don't happen very often, but when they do they get a lot of attention if 48 00:03:14,400 --> 00:03:15,860 it's over land. 49 00:03:15,860 --> 00:03:20,799 So a fireball's a meteor brighter than Venus, and a superbolide is a meteor brighter than 50 00:03:20,799 --> 00:03:23,439 the full moon. 51 00:03:23,439 --> 00:03:27,989 What happened over Russia was most definitely a superbolide. 52 00:03:27,989 --> 00:03:31,819 So, how does this work? 53 00:03:31,819 --> 00:03:34,730 In space, you've got a hunk of rock, a meteoroid. 54 00:03:34,730 --> 00:03:40,080 It hits the atmosphere, it burns up, or if it's bigger it breaks apart into little pieces 55 00:03:40,080 --> 00:03:47,830 which burn up, and when it gets down to about 10 to 30 miles above the surface of the Earth, 56 00:03:47,830 --> 00:03:52,760 the atmosphere slows those things down so low they're no longer burning up and they 57 00:03:52,760 --> 00:03:55,810 stop emitting light. 58 00:03:55,810 --> 00:04:00,349 So you've got something blazing through the atmosphere and if it gets deep enough down 59 00:04:00,349 --> 00:04:05,980 the atmospheric drag slows it down to the point where they get below 3 miles a second 60 00:04:05,980 --> 00:04:07,519 and stop emitting light. 61 00:04:07,519 --> 00:04:14,010 At that point they no longer are ablating and we call from that on dark flight because 62 00:04:14,010 --> 00:04:16,940 we don't see them anymore.