# Antigravity? Do rocks float? **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [October 24, 2017, 1:31am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675 "2017-10-24T01:31:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![ASGuy](https://avatars.discourse-cdn.com/v4/letter/a/838e76/32.png) [@ASGuy](https://boards.straightdope.com/u/ASGuy)\ **Post date:** [October 24, 2017, 1:31am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/1 "2017-10-24T01:31:16Z")
Last year I dug out a 10’ x 10’ area on my property to a depth of 4 inches. My goal was to screen out all gravel larger than about 3/4 inch. Completing the project left a flat square area with _no_ visible gravel. It is now 15 months later and there is an abundance of “illegal” stones visible. We had a heavy rainfall winter, but no earthquakes of note. Moles are commmon here but I have not seen any signs of mole activity in this area, and such signs are usually obvious. I do live near a State highway. Heavy trucks are common. But the highway is about 240 feet away so I tend to discount vibrational forces. This is not the first time I have noticed this effect. But in this case I _know_ the earth was screened and the surface devoid of gravel. Yet a year later rocks appeared. I am now convinced that rocks float to the surface of surrounding earth. What do you think? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [October 24, 2017, 2:31am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/2 "2017-10-24T02:31:23Z")
It’s a well-known phenomenon in areas with freeze/thaw cycles. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [October 24, 2017, 3:41am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/3 "2017-10-24T03:41:58Z")
It’s not that rocks float. It’s that dirt sinks. Gravity is pulling everything in your field down. But tiny particles of dirt are able to travel down more easily than big rock because they can pass through smaller spaces. So the dirt ends up below the rocks. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [October 24, 2017, 4:29am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/4 "2017-10-24T04:29:30Z")
You’ve discovered an upsidaisium mine on your property! Beware of furtive [del]Яussians[/del] Pottsylvanians trying to con you out of your land! ---
**Author:** ![Snowboarder\_Bo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/snowboarder_bo/32/229_2.png) [@Snowboarder\_Bo](https://boards.straightdope.com/u/Snowboarder_Bo)\ **Post date:** [October 24, 2017, 5:00am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/5 "2017-10-24T05:00:45Z")
> [@Little\_Nemo](#): > > It’s not that rocks float. It’s that dirt sinks. > > Gravity is pulling everything in your field down. But tiny particles of dirt are able to travel down more easily than big rock because they can pass through smaller spaces. So the dirt ends up below the rocks. Aye; that’s basic sorting. ---
**Author:** ![ASGuy](https://avatars.discourse-cdn.com/v4/letter/a/838e76/32.png) [@ASGuy](https://boards.straightdope.com/u/ASGuy)\ **Post date:** [October 24, 2017, 11:55am UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/6 "2017-10-24T11:55:41Z")
Thank you **Little Nemo** for a reasonable explanation. But doesn’t that mean the earth is shrinking and we will all get crushed into a neutron star? I suppose if we do at least we can take comfort in the knowledge that we’ll be turned into gold. But just in case **Senegoid** is correct I’ll keep my eye out for Boris and Natasha. ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [October 24, 2017, 12:30pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/7 "2017-10-24T12:30:44Z")
You’ve all got it wrong. An understandable mistake, as your explanations all make good sense and seem to be well thought out, but they all omit one lesser-known tidbit of information. Rocks grow. When you till the earth, you are adding rock nutrients (believed to be mostly oxygen, but some researchers believe nitrogen, and to a lesser extent, CO2 also play a role). **ASGuy** , did you also add fertilizer? And, if you added topsoil or other “alien” soil to the area, well, your are really just encouraging a bumper-crop of rocks. Farmers, particularly in regions where rocks grow well, have known of these phenomenon for a long time. Because rock growth is very specific to the type and size of rocks in your area, you may want to consult with your local Extension Agent for advice for your particular problem. Unfortunately, due to the inorganic nature of rocks, organic methods for control have not been found to be effective. ---
**Author:** ![digs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/digs/32/14889_2.png) [@digs](https://boards.straightdope.com/u/digs)\ **Post date:** [October 24, 2017, 2:07pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/8 "2017-10-24T14:07:23Z")
Me wife she got a bit uvva garden back by the compost heap an’ she took it to her head to plant a row o’ rocks tween the courgettes an’ th’ aubergines. Course they’s all pebbles when they’s planted – mostly igneous. Some pyroxenite, some carbonatite, oh an’ some adakite - them what’s got a bit o’ yttrium and ytterbium in 'em. Waal, she been out wat’rin’ ‘em an’ talkin ‘em… an’ durned effin we don’t got us a pret’ good harvest this autumn. Tryin’ ah givem tuh th’ neighbors, but reckon they’s got plenty. Widder next door takes a few though. But ya, yeh mighta gots some stray rocks from a neighbor’s garden. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [October 24, 2017, 2:17pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/9 "2017-10-24T14:17:56Z")
Rocks appear every year when we till the soil for the garden. We remove the bigger ones. Next year the same thing. Thirty years later you’re still removing rocks. It does get easier. The first few years it’s hard work tilling new ground. ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [October 24, 2017, 4:11pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/10 "2017-10-24T16:11:16Z")
> [@ASGuy](#): > > Thank you **Little Nemo** for a reasonable explanation. But doesn’t that mean the earth is shrinking and we will all get crushed into a neutron star? I suppose if we do at least we can take comfort in the knowledge that we’ll be turned into gold. Well, did you happen to notice whether the dirt took up more space after all the digging and screening (after accounting for the removed rocks)? The earth isn’t shrinking much overall, no, but the entire point of plowing and tilling is to fluff up the dirt so it’s less compacted. Naturally, that process will slowly reverse itself. (Even where there’s no plowing, growing roots and freezing water will also aerate the soil somewhat, which lets it shrink back down later, leaving bigger rocks on top). ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [October 24, 2017, 4:20pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/11 "2017-10-24T16:20:34Z")
Granular convection / Brazil Nut effect / Muesli effect > **[Nuts and Seeds Guides](https://www.seriouseats.com/nuts-seed-guides-5117997)** > > Browse through our nut and seed guides to learn about their varieties and the textures they bring to fritters, noodles, smoothies, breads, and some of our favorite desserts. > **[Granular convection](https://en.wikipedia.org/wiki/Granular_convection)** > > Granular convection is a phenomenon where granular material subjected to shaking or vibration will exhibit circulation patterns similar to types of fluid convection. It is sometimes called the Brazil nut effect, when the largest of irregularly shaped particles end up on the surface of a granular material containing a mixture of variously sized objects. This name derives from the example of a typical container of mixed nuts, in which the largest will be Brazil nuts. The phenomenon is als Under ex... ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [October 24, 2017, 4:29pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/12 "2017-10-24T16:29:58Z")
And Steven Fry says that nobody knows why it happens. http://qi.com/infocloud/brazil-nuts ---
**Author:** ![Intergalactic\_Gladiator](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/intergalactic_gladiator/32/112_2.png) [@Intergalactic\_Gladiator](https://boards.straightdope.com/u/Intergalactic_Gladiator)\ **Post date:** [October 24, 2017, 4:30pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/13 "2017-10-24T16:30:29Z")
Rocks move, man: [![](https://img.youtube.com/vi/2oS4mlCtqmQ/maxresdefault.jpg "Mystery of Death Valley’s ‘Sailing Stones’ May Have Been Solved") ](https://www.youtube.com/watch?v=2oS4mlCtqmQ) ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [October 24, 2017, 4:48pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/14 "2017-10-24T16:48:10Z")
Rocks also sink, thanks to earthworms. [A short explanation](https://www.nationaltrust.org.uk/leith-hill-place/features/darwins-worm-stone-at-leith-hill). [A long, rambling one](http://www.georgialifetraces.com/2012/05/29/of-darwin-earthworms-and-backyard-science/). ---
**Author:** ![Doctor\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/doctor_jackson/32/32_2.png) [@Doctor\_Jackson](https://boards.straightdope.com/u/Doctor_Jackson)\ **Post date:** [October 24, 2017, 8:18pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/15 "2017-10-24T20:18:17Z")
Actually, you’ve been visited by Johnny Appleseed’s lesser known but no less prolific cousin - Ricky Rockseed. He travels the globe lovingly sprinkling rock seeds onto any patch of ground that looks like it may support their growth. From a “take root, grow and self propagate” perspective he hasn’t seen nearly the success of his cousin Johnny, but he is one determined fellow, as you have learned. There can be a downside to living up to one’s name… ---
**Author:** ![ASGuy](https://avatars.discourse-cdn.com/v4/letter/a/838e76/32.png) [@ASGuy](https://boards.straightdope.com/u/ASGuy)\ **Post date:** [October 25, 2017, 4:00pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/16 "2017-10-25T16:00:43Z")
> [@Quercus](#): > > Well, did you happen to notice whether the dirt took up more space after all the digging and screening (after accounting for the removed rocks)? The earth isn’t shrinking much overall, no, but the entire point of plowing and tilling is to fluff up the dirt so it’s less compacted. Naturally, that process will slowly reverse itself. (Even where there’s no plowing, growing roots and freezing water will also aerate the soil somewhat, which lets it shrink back down later, leaving bigger rocks on top). Sure, screening fluffs up the dirt and indeed it was somewhat higher at first. In a year it compacted as you described. But the fluffed-up earth did not have any gravel in it so the gravel that showed up came from below my screened area. As for granular convection I don’t think there’s enough vibrational forces to cause it. Earthworms? The soil is brutally hard and unfertile. Earthworms, if they are present at all, are at least a foot down. I’m going to stick with sinking earth. (Or Boris and Natasha.) ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [October 25, 2017, 5:43pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/17 "2017-10-25T17:43:12Z")
> [@ASGuy](#): > > … As for granular convection I don’t think there’s enough vibrational forces to cause it. … Probably more than you appreciate but even if not the contraction/expansion cycles associated with freezes and thaws and movement associated merely with water flowing through the material would be enough. Surface was devoid of gravel but no question there was still much in the volume of fluffed up dirt to 4 inches deep. Note that “sinking earth” _is_ the basis of granular convection. As the smaller bits get around the bigger bits and sink into the spaces under the bigger bits they inexorably prop up the bigger bits into the spaces the smaller bits left behind. ---
**Author:** ![WildBlueYonder](https://avatars.discourse-cdn.com/v4/letter/w/ce7236/32.png) [@WildBlueYonder](https://boards.straightdope.com/u/WildBlueYonder)\ **Post date:** [October 25, 2017, 5:43pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/18 "2017-10-25T17:43:46Z")
Try the Earth crust moves? Even if youre not in an earthquake zone. Farmers pick up rocks year after year after year. Unless its erosion. Your big hole in the ground is likely not eroding so the Earth crust moves, pushing whatever it wants up to the surface…thanks my take :D:D:dubious: ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [October 25, 2017, 8:05pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/19 "2017-10-25T20:05:08Z")
[off-topic] Substantially off-topic, but… as long as we’re tangentially discussing Boris and Natasha, here’s a cute parody column in which our evil villains attempt to infiltrate the Trump Administration using goof gas and a dumb Moose as their dupe . . . [Boris and Natasha come to life in the Adventures of Trump](https://chicago.suntimes.com/opinion/turning-america-into-a-cartoon-show/) [/off-topic] ---
**Author:** ![Terminus\_Est](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/terminus_est/32/3087_2.png) [@Terminus\_Est](https://boards.straightdope.com/u/Terminus_Est)\ **Post date:** [October 26, 2017, 1:19pm UTC](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675/20 "2017-10-26T13:19:15Z")
Since the OP asked, rocks do float: [pumice stones](https://www.youtube.com/watch?v=Rr6nFhfiZ-k) [Next page](https://boards.straightdope.com/t/antigravity-do-rocks-float/799675.md?page=2)