# Space questions from my son **URL:** \ **Category:** Factual Questions\ **Created:** [October 26, 2009, 3:47pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187 "2009-10-26T15:47:00Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Stealth\_Potato](https://avatars.discourse-cdn.com/v4/letter/s/d78d45/32.png) [@Stealth\_Potato](https://boards.straightdope.com/u/Stealth_Potato)\ **Post date:** [October 26, 2009, 7:43pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/21 "2009-10-26T19:43:29Z")
> [@Munch](#): > > Wouldn’t it just fall back to Earth, just like everything else you shoot into space? Depends on where you are, how fast you’re going, and the velocity you impart to the gas molecules. If you’re in Earth orbit, the molecules would just spread out into similar orbits, unless you gave them enough speed to either escape Earth’s gravity entirely, or to counteract their orbital velocity and fall into some orbit that intersects the atmosphere. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [October 26, 2009, 7:49pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/22 "2009-10-26T19:49:25Z")
> [@Munch](#): > > Wouldn’t it just fall back to Earth, just like everything else you shoot into space? Everything we shoot into space doesn’t fall back to Earth. If the object is traveling at or above its Escape Velocity it will never return to earth. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [October 26, 2009, 7:58pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/23 "2009-10-26T19:58:25Z")
And if it’s orbiting the Earth it will stay orbiting the Earth forever, unless it bumps into something else. ---
**Author:** ![Svejk\_1](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@Svejk\_1](https://boards.straightdope.com/u/Svejk_1)\ **Post date:** [October 26, 2009, 8:26pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/24 "2009-10-26T20:26:12Z")
> [@frazeb](#): > > In fact, every molecule in your body was, at one time, in the center of a giant star! wow. that’s my mindblowing quote for the day! thanks for that 😃 ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [October 26, 2009, 8:43pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/25 "2009-10-26T20:43:45Z")
> [@Whack-a-Mole](#): > > I once asked here how big a bomb an adult human would be if they had their mass converted to energy. [The answer was around 6,750 megatons](http://boards.straightdope.com/sdmb/showthread.php?t=122487) (for comparison the largest nuclear bomb ever built was 100 megatons). Incidentally, this is nowhere near the energy you’d need to blow up the Earth. You’d need a chunk of antimatter about the size of a city to do that. Mr. Neville gave a midterm in his astronomy class last week, and this was one of the problems on it. He said I inspired him to come up with it. Awwww. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [October 26, 2009, 8:54pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/26 "2009-10-26T20:54:01Z")
> [@Svejk\_1](#): > > wow. that’s my mindblowing quote for the day! thanks for that 😃 Way back in _Babylon 5_, when Delenn said, “We are star stuff,” she wasn’t kiddin’ Virtually everything heavier than hydrogen was forged in the heart of a long dead star. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [October 26, 2009, 8:55pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/27 "2009-10-26T20:55:20Z")
> [@DesertDog](#): > > Way back in _Babylon 5_, when Delenn said, “We are star stuff,” she wasn’t kiddin’ Virtually everything heavier than hydrogen was forged in the heart of a long dead star. If you’re an optimist, you can say we’re made of star stuff. If you’re a pessimist, you can say we’re made of nuclear waste. ---
**Author:** ![pan1](https://avatars.discourse-cdn.com/v4/letter/p/e495f1/32.png) [@pan1](https://boards.straightdope.com/u/pan1)\ **Post date:** [October 26, 2009, 8:59pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/28 "2009-10-26T20:59:15Z")
> [@DesertDog](#): > > Way back in _Babylon 5_, when Delenn said, “We are star stuff,” she wasn’t kiddin’ Virtually everything heavier than hydrogen was forged in the heart of a long dead star. …Or during the supernova marking the moment of death. ---
**Author:** ![pan1](https://avatars.discourse-cdn.com/v4/letter/p/e495f1/32.png) [@pan1](https://boards.straightdope.com/u/pan1)\ **Post date:** [October 26, 2009, 9:04pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/29 "2009-10-26T21:04:36Z")
> [@Munch](#): > > Wouldn’t it just fall back to Earth, just like everything else you shoot into space? Depends on how close Earth is when you shoot the air out. If Earth is the closest gravity well, then yes. And last I checked everything we shoot into space doesn’t make it back, Neither Voyager Probe is due to fall back to Earth in the coming weeks, or ever. Viking, ditto, Beagle, Casini… We shoot a lot of stuff out there that will never come back. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [October 26, 2009, 9:26pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/30 "2009-10-26T21:26:01Z")
> [@pan1](#): > > Depends on how close Earth is when you shoot the air out. If Earth is the closest gravity well, then yes. > > And last I checked everything we shoot into space doesn’t make it back, Neither Voyager Probe is due to fall back to Earth in the coming weeks, or ever. Both Voyager probes are long gone, never to return\*. Voyager-1 left the solar system about five years ago. Voyager-2 left the solar system about [two years ago](http://www.newscientist.com/article/dn13029?feedId=online-news_rss20). They will continue on into interstellar space forever. [sub]\*- Well, if it comes back it will probably be as the [planet collecting V’ger](http://en.wikipedia.org/wiki/V%27ger). 😉 [/sub] ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [October 26, 2009, 9:34pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/31 "2009-10-26T21:34:36Z")
> [@frazeb](#): > > Here’s another fun fact for your son. As the sun exhausts its usable hydrogen it will start to push the helium molecules together to form carbon. If the star is large enough it will keep pressing heavier and heavier molecules together creating all of the heavier elements that we see around us. When those stars finally run out of fuel they explode in giant supernova explosions which scatter those molecules into space. Our solar system condensed out of one of those clouds, and thanks to the heavier elements that were in there, our planets formed. In fact, every molecule in your body was, at one time, in the center of a giant star! On a religious board I participate in, after this point was made in a Creation vs. Evolution debate (which of course regarded Big Bang cosmology and nucleosynthesis as part of ‘Darwinian theory’ :rolleyes: ), someone commented “We are made up of stardust.” I knew my cue. I quoted that, and responded, “We are golden … and we’ve got to get ourselves back to the Garden.” 😃 ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [October 26, 2009, 10:16pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/32 "2009-10-26T22:16:58Z")
Somewhat tangental to the overall topic of the thread, but let me note that oxygen isn’t necessary to combustion. An “oxidizer” needn’t actually be oxygen. > **[Combustion](https://en.wikipedia.org/wiki/Combustion)** > > Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion does not always result in fire, because a flame is only visible when substances undergoing combustion vaporize, but when it does, a flame is a characteristic indicator of the reaction. While activation energy must be supplied to initiate combustion (e.g Co... > **[Oxidizing agent](https://en.wikipedia.org/wiki/Oxidant)** > > An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "accepts"/"receives" an electron from a reducing agent (called the reductant, reducer, or electron donor). In other words, an oxidizer is any substance that oxidizes another substance. The oxidation state, which describes the degree of loss of electrons, of the oxidizer decreases while that of the reductant increases; this is expressed by s... Oxygen just happens to be a prevalent and geared towards producing oxydizers (or something). ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [October 26, 2009, 10:27pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/33 "2009-10-26T22:27:21Z")
> [@Svejk\_1](#): > > wow. that’s my mindblowing quote for the day! thanks for that 😃 Want another one? Since the atoms that make up our biosphere are more or less indestructible, and are very well recycled, and you’re made up of SO MANY of them, you right now almost certainly have atoms that used to belong to Julius Caesar. ---
**Author:** ![Svejk\_1](https://avatars.discourse-cdn.com/v4/letter/s/ea666f/32.png) [@Svejk\_1](https://boards.straightdope.com/u/Svejk_1)\ **Post date:** [October 26, 2009, 10:42pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/34 "2009-10-26T22:42:12Z")
Well, I already had my mindblowing quote for today so this is getting a bit too much, but thanks all the same. 🙂 ETA: can we say with the same certainty that I now have atoms that used to belong to Adolf Hitler? :eek: ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [October 26, 2009, 10:48pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/35 "2009-10-26T22:48:55Z")
> [@Svejk\_1](#): > > ETA: can we say with the same certainty that I now have atoms that used to belong to Adolf Hitler? :eek: Yes. With every breath you take, on average you inhale four molecules that Hitler exhaled in his last breath. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [October 26, 2009, 11:33pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/36 "2009-10-26T23:33:04Z")
> [@pan1](#): > > Depends on how close Earth is when you shoot the air out. If Earth is the closest gravity well, then yes. . . . Yeah, unless you specify, there’s much more space beyond the gravity well of Earth than within it. Much, much more. Oh, so much, much more. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [October 26, 2009, 11:51pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/37 "2009-10-26T23:51:14Z")
> [@DesertDog](#): > > Way back in _Babylon 5_, when Delenn said, “We are star stuff,” she wasn’t kiddin’ Virtually everything heavier than hydrogen was forged in the heart of a long dead star. I think Carl Sagan said that a bit before B5. I don’t know if he invented it. Cosmos would be a cool thing for a kid to watch. BTW, if the OP is going to talk about supernovas, it might be wise to mention that the Sun isn’t nearly big enough to explode in this way. And it is probably better not to mention what will happen to it. It might happen billions of years in the future, but little kids don’t have great concepts of time. BTW Phil Plait, our very own Bad Astronomer, has an excellent book called [Death From the Skies](http://en.wikipedia.org/wiki/Death_from_the_Skies). ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [October 26, 2009, 11:59pm UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/38 "2009-10-26T23:59:45Z")
> [@Voyager](#): > > I think Carl Sagan said that a bit before B5. I don’t know if he invented it. Cosmos would be a cool thing for a kid to watch. [Star Stuff](http://www.youtube.com/watch?v=iE9dEAx5Sgw) _Cosmos_ segment. ---
**Author:** ![Ponderoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponderoid/32/19221_2.png) [@Ponderoid](https://boards.straightdope.com/u/Ponderoid)\ **Post date:** [October 27, 2009, 12:06am UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/39 "2009-10-27T00:06:48Z")
> [@friedo](#): > > The convenient thing is that the heat produced by the reaction is enough to start nearby hydrogen atoms smashing into each other, and you end up with a lovely big ball o’chain-reacting hydrogen. No. The primary fusion reaction in a star is driven by the gravitational pressure from its huge mass. It’s not a chain reaction like in a fission reactor or bomb. The energy produced by each fusion reaction actually serves to push apart the atoms, making the core less dense, slowing down the reaction. Until they run out of fuel, stars are in a dynamic balance between gravitational pressure compressing in, and fusion energy holding the mass apart. ---
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [October 29, 2009, 6:20am UTC](https://boards.straightdope.com/t/space-questions-from-my-son/515187/40 "2009-10-29T06:20:38Z")
> [@Polycarp](#): > > On a religious board I participate in, after this point was made in a Creation vs. Evolution debate (which of course regarded Big Bang cosmology and nucleosynthesis as part of ‘Darwinian theory’ :rolleyes: ), someone commented “We are made up of stardust.” > > I knew my cue. I quoted that, and responded, “We are golden … and we’ve got to get ourselves back to the Garden.” 😃 Thank you. \*Babylon Five \*and \*Cosmos \*indeed. Joni sang about being billion year old carbon in 1969. [Previous page](https://boards.straightdope.com/t/space-questions-from-my-son/515187.md?page=1) [Next page](https://boards.straightdope.com/t/space-questions-from-my-son/515187.md?page=3)