# No cause for alarm **URL:** \ **Category:** Factual Questions\ **Created:** [June 12, 2007, 2:59am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658 "2007-06-12T02:59:05Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![CJOK](https://avatars.discourse-cdn.com/v4/letter/c/e36b37/32.png) [@CJOK](https://boards.straightdope.com/u/CJOK)\ **Post date:** [June 12, 2007, 2:59am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/1 "2007-06-12T02:59:05Z")
I was wondering what your readers thoughts might be on this subject. How come the earth has not smashed into a larger object, like all these dumb comets and meteors keep doing? Have we just been very lucky, or are we well overdue? Sorry to bring such a grim subject up. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [June 12, 2007, 3:13am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/2 "2007-06-12T03:13:23Z")
The earth was hit by comets and asteroids gazillions of times. Most of these, however, took place in the early days of the solar system. One really big one, maybe the size of Mars, hit the earth so hard that a chunk broke off and became the moon. Strikes were a major effect for hundreds of millions of years. Over billions of years the smaller debris were captured by the gravitational fields of the larger bodies and the number of objects flying randomly around the solar system decreased by an astounding percentage. A few are still out there, and we are still hit by micro-meteors all the time, pebble-sized objects occasionally, and so on up the scale until a major mile-wide body hits maybe once every half a billion years. There is a band of snowballs called the Oort cloud that are perturbed by gravitational forces and become long-period comets. One of these will hit us eventually. (And maybe short-period comets out of another, closer, region called the Kuiper belt.) But that’s eventually in geologic time. It’s unlikely to happen in human scale time. We have asteroids come as close as the moon on a regular basis, though. Nothing out there right now is known to have an orbit that will hit earth. It wouldn’t be very surprising for one to hit in the next thousand years or even the next hundred. But we’re not overdue. This is a completely random process. It might not happen for 100,000 years. It’s not something that anybody is worried about. We have more immediate crises here on earth. But it’s a real risk, even if very long-term and low-probability. Such events are thought to have precipitated many of the major extinctions on the planet. Of course, the last one of those was 65,000,000 years ago. I’m not losing any sleep over it. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [June 12, 2007, 3:18am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/3 "2007-06-12T03:18:18Z")
[QUOTE=CJOK] How come the earth has not smashed into a larger object . . . [/QUOTE] Is this what you’re actually asking? Why the earth hasn’t smashed into, say, the sun or one of the larger planets? ---
**Author:** ![CJOK](https://avatars.discourse-cdn.com/v4/letter/c/e36b37/32.png) [@CJOK](https://boards.straightdope.com/u/CJOK)\ **Post date:** [June 12, 2007, 3:21am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/4 "2007-06-12T03:21:00Z")
[QUOTE=Exapno Mapcase] The earth was hit by comets and asteroids gazillions of times. Most of these, however, took place in the early days of the solar system. One really big one, maybe the size of Mars, hit the earth so hard that a chunk broke off and became the moon. Strikes were a major effect for hundreds of millions of years. Over billions of years the smaller debris were captured by the gravitational fields of the larger bodies and the number of objects flying randomly around the solar system decreased by an astounding percentage. A few are still out there, and we are still hit by micro-meteors all the time, pebble-sized objects occasionally, and so on up the scale until a major mile-wide body hits maybe once every half a billion years. There is a band of snowballs called the Oort cloud that are perturbed by gravitational forces and become long-period comets. One of these will hit us eventually. (And maybe short-period comets out of another, closer, region called the Kuiper belt.) But that’s eventually in geologic time. It’s unlikely to happen in human scale time. We have asteroids come as close as the moon on a regular basis, though. Nothing out there right now is known to have an orbit that will hit earth. It wouldn’t be very surprising for one to hit in the next thousand years or even the next hundred. But we’re not overdue. This is a completely random process. It might not happen for 100,000 years. It’s not something that anybody is worried about. We have more immediate crises here on earth. But it’s a real risk, even if very long-term and low-probability. Such events are thought to have precipitated many of the major extinctions on the planet. Of course, the last one of those was 65,000,000 years ago. I’m not losing any sleep over it. [/QUOTE] I accept that they are hitting us , BUT why are n`t we hitting anything else .Don`t forget we are travelling in an orbit too. And don`t worry I am not losing any sleep over the matter, I`m an insomniac anyway! 🙂 ---
**Author:** ![CJOK](https://avatars.discourse-cdn.com/v4/letter/c/e36b37/32.png) [@CJOK](https://boards.straightdope.com/u/CJOK)\ **Post date:** [June 12, 2007, 3:22am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/5 "2007-06-12T03:22:40Z")
[QUOTE=panache45] Is this what you’re actually asking? Why the earth hasn’t smashed into, say, the sun or one of the larger planets? [/QUOTE] YES! 😉 ---
**Author:** ![CJOK](https://avatars.discourse-cdn.com/v4/letter/c/e36b37/32.png) [@CJOK](https://boards.straightdope.com/u/CJOK)\ **Post date:** [June 12, 2007, 3:25am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/6 "2007-06-12T03:25:15Z")
[QUOTE=CJOK] YES! 😉 [/QUOTE] Erm… NO! I think I`m talkin` about s\*&t beyond our solar system! ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [June 12, 2007, 3:27am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/7 "2007-06-12T03:27:11Z")
Because orbits are stable. Unless something huge happens - like another sun coming through the system and perturbing everything - the planets (and even the asteroids) are locked in their orbits essentially forever. ---
**Author:** ![CJOK](https://avatars.discourse-cdn.com/v4/letter/c/e36b37/32.png) [@CJOK](https://boards.straightdope.com/u/CJOK)\ **Post date:** [June 12, 2007, 3:32am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/8 "2007-06-12T03:32:43Z")
[QUOTE=Exapno Mapcase] Because orbits are stable. Unless something huge happens - like another sun coming through the system and perturbing everything - the planets (and even the asteroids) are locked in their orbits essentially forever. [/QUOTE] WOW! That`s comforting. Cheer`s mate, i`m happy with that one! 😉 ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [June 12, 2007, 3:43am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/9 "2007-06-12T03:43:44Z")
[QUOTE=Exapno Mapcase] One really big one, maybe the size of Mars, hit the earth so hard that a chunk broke off and became the moon. [/QUOTE] Cite? ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [June 12, 2007, 3:50am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/10 "2007-06-12T03:50:45Z")
Try [The Origin of the Moon](http://www.psi.edu/projects/moon/moon.html) Or just google moon origin and look at any hit. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [June 12, 2007, 4:54am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/11 "2007-06-12T04:54:19Z")
As an aside, you might also look up the subject of the long-term stability of the Solar System; something that’s interested astronomers and mathematicians for centuries. In general, the current arrangement- each planet’s orbit is about, but never exactly, twice as far from the Sun as the next nearest one- seems to be one that is very highly stable over billions of years. You might not be able to predict exactly where in it’s orbit the Earth will be one billion years and six days from now, but that it will still be in about the same orbit as it is now seems virtually guaranteed. ---
**Author:** ![groman](https://avatars.discourse-cdn.com/v4/letter/g/73ab20/32.png) [@groman](https://boards.straightdope.com/u/groman)\ **Post date:** [June 12, 2007, 7:25am UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/12 "2007-06-12T07:25:57Z")
[QUOTE=CJOK] Erm… NO! I think I`m talkin` about s\*&t beyond our solar system! [/QUOTE] The shit beyond our solar system is so mind-blowingly far and sparse that I doubt anything large will ever hit us before the sun goes bye-bye. Unless the universe goes the way of the big crunch, which wouldn’t happen for billions of years anyway, we’re unlikely to ever encounter much of anything. Our galaxy might collide with another one, but the chances of our solar system actually physically smashing into some other object even when galaxies collide are pretty small. ---
**Author:** ![gonzomax](https://avatars.discourse-cdn.com/v4/letter/g/e8c25b/32.png) [@gonzomax](https://boards.straightdope.com/u/gonzomax)\ **Post date:** [June 12, 2007, 4:43pm UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/13 "2007-06-12T16:43:32Z")
We are specks of dirt in a huge and expanding universe. There is huge amounts of space between everything. Ps Nobody is worried about getting hit? Wrong .we have telescopes all over trying to identify the final rock. It will happen again. We just do not know when. Check out [Center for NEO Studies](http://neo.jpl.nasa.gov/neo/) Identification and odds of getting hit . ---
**Author:** ![Scuba\_Ben](https://avatars.discourse-cdn.com/v4/letter/s/278dde/32.png) [@Scuba\_Ben](https://boards.straightdope.com/u/Scuba_Ben)\ **Post date:** [June 12, 2007, 5:23pm UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/14 "2007-06-12T17:23:55Z")
Meteor Crater, AZ, looks like _something_ smashed into us. So do some sites off the Yucatan Peninsula, in Mexico / Guatemala. And anything on a comparable scale as Earth in a position for Earth to collide with, under generally accepted models the collisions happened in the range of 4 to 5 billion years before present. Since then – there ain’t anything there large enough to be an issue. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [June 12, 2007, 7:33pm UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/15 "2007-06-12T19:33:10Z")
[QUOTE=Scuba\_Ben] Meteor Crater, AZ, looks like _something_ smashed into us. [/QUOTE] [Earth Impact Database](http://www.unb.ca/passc/ImpactDatabase/index.html) ---
**Author:** ![CJOK](https://avatars.discourse-cdn.com/v4/letter/c/e36b37/32.png) [@CJOK](https://boards.straightdope.com/u/CJOK)\ **Post date:** [June 12, 2007, 8:12pm UTC](https://boards.straightdope.com/t/no-cause-for-alarm/407658/16 "2007-06-12T20:12:02Z")
Thanks to all of you for your answers, guys[and any gals].There was some interesting, informative stuff there. Again, Cheers. from col. 😉