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Re[4]: Sila iz pustoty: effekt Kazimira
5.01.2007 14:34 | Dmitrii Docenko
Ya srazu skazhu, chto ne specialist v etoi oblasti (stat'yu tozhe ne chital poka). No nablyudeniya yakoby sovpadayut s teoreticheskoi model'yu na urovne 1%! A dlya togo, chtoby raznost' davlenii smogla vyglyadet' kak effekt Kazimira, ona ne tol'ko dolzhna imet' takuyu zhe funkcional'nuyu zavisimost' ot rasstoyaniya mezhdu poverhnostei, no i imet' tochno neobhodimuyu amplitudu (kotoraya k tomu zhe zavisit ot davleniya).
Prikinuv chisla, poluchaetsya vot chto. Pri davlenii 0.05 mm.rt.st. imeem koncentraciyu atomov okolo 2*10^15 v sm^3, to est' odin atom vozduha nahoditsya v kube storonoi poryadka 0.1 mkm. Takim obrazom, mezhdu sharikom i stenkoi nahoditsya sravnitel'no nebol'shoe kolichestvo atomov, kotoroe lineino umen'shaetsya s umen'sheniem rasstoyaniya mezhdu sharikom i stenkoi. Davlenie vozduha so storony stenki togda dolzhno takzhe lineino umen'shatsya; a raznost' davlenii (i izmeryaemaya sila) - lineino uvelichivat'sya (poka razmer sharika mnogo bol'she rasstoyaniya do stenki). Vrode by tak.
A nablyudaetsya kubicheskaya zavisimost' (sovsem nelineinaya, po krainei mere). Po idee, odno eto isklyuchaet vozmozhnost' togo, chto nablyudaemaya sila voznikaet iz-za raznicy davlenii.
Naschet poryadka velichiny - kak Vy ego ocenili? Sobstvenno davlenie est' 0.05*133 Pa = 7 Pa. Sootvetstvenno, sila, kotoraya davit na odnu storonu sharika, est' primerno 10 mN. Kak u Vas poluchilis' pN?
S uvazheniem,
Dima
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- Sila iz pustoty: effekt Kazimira (Astronomicheskaya kartinka dnya, 17.12.2006, 2.1 KBait, otvetov: 8) Etot kroshechnyi sharik demonstriruet beskonechnoe rasshirenie Vselennoi vo vremeni. Nemnogim bolee odnoi desyatoi millimetra v diametre, on dvizhetsya v storonu gladkoi plastinki blagodarya fluktuaciyam energii vakuuma. Sila prityazheniya mezhdu sharikom i plastinkoi obuslovlena effektom Kazimira. Effekt nazvan imenem otkryvshego ego uchenogo, kotoryi 50 let nazad, pytalsya ob'yasnit', pochemu tak medlenno dvizhutsya zhidkosti, podobnye maionezu. V nastoyashee vremya uchenye vse bolee sklonyayutsya k tomu, chto osnovnaya sostavlyayushaya plotnosti energii vo Vselennoi nahoditsya v forme tak nazyvaemoi temnoi energii. Priroda i proishozhdenie temnoi energii ostayutsya neponyatnymi. Po odnoi iz gipotez, ee poyavlenie svyazano s fluktuaciyami vakuuma, analogichno effektu Kazimira, no v sluchae temnoi energii eti fluktuacii generiruyutsya samim prostranstvom. Po-vidimomu, eta obshirnaya i tainstvennaya temnaya energiya gravitacionno ottalkivaet lyuboe veshestvo, i poetomu Vselennaya budet rasshiryat'sya vsegda. Raboty po ob'yasneniyu fluktuacii vakuuma nahodyatsya na perednem krae nauki. Ih ponimanie pozvolit ne tol'ko luchshe ponyat' nashu Vselennuyu, no takzhe predotvrashat' slipanie drug s drugom mikromehanicheskih chastei mashin.
- Re: Sila iz pustoty: effekt Kazimira
(M. Yu. Yakimov,
20.12.2006 11:15, 1.5 KBait, otvetov: 5)
Eto uzhe tret'ya publikaciya na APOD odnoi i toi zhe kartinki (sm. 17.09.2002, 1.08.2004). Pohozhe na to, chto real'nost' eksperimental'nogo obnaruzheniya tak nazyvaemogo effekta Kazimira kto-to pytaetsya dokazat' ispytannym metodom mnogokratnogo povtoreniya. Tem ne menee, provedennye do sih por eksperimenty slishkom primitivny po svoei postanovke, chtoby uverenno obnaruzhit' i izuchit' eksperimental'no etot effekt. O nekotoryh trudnostyah vskol'z' upominaetsya v populyarnoi stat'e, perevod kotoroi est' na saite (sm. http://www.astronet.ru/db/msg/1180311). No v nei zhe zamalchivayutsya bolee principial'nye trudnosti, naprimer, ne privoditsya ni odnoi cifry, chto konkretno predstavlyaet soboi effekt Kazimira na fone teplovyh, zaryadovyh, nakonec, kvantovyh fluktuacii, fluktuacii plotnosti (ideal'nyi vakuum poluchit' nevozmozhno) i dr. Esli provesti korrektno eti ocenki, to okazhetsya, chto obnaruzhenie stol' malogo effekta nastol'ko slozhnaya eksperimental'naya zadacha, chto stanovitsya yasno, chto takimi topornymi metodami, kak eto delalos' do sih por, vryad li mozhno obnaruzhit' stol' tonkii effekt (obnaruzhivalos' vsegda chto-to drugoe, trivial'noe, k rassmatrivaemomu yavleniyu otnosheniya ne imeyushee). Da i po stilyu stat'ya, ssylka na kotoruyu privedena vyshe, pohozha na tipichnuyu lzhenauchnuyu agitku. Budu rad pochitat' chto nibud'o hotya by skol'ko-nibud' ser'eznoi popytke eksperimental'nogo obnaruzheniya effekta Kazimira, no poka nichego ne popadalos'.
- Re[2]: Sila iz pustoty: effekt Kazimira
(Dmitrii Docenko,
4.01.2007 16:36, 1.3 KBait, otvetov: 4)
Posmotrite zdes': Phys.Rev.Lett. 81 (1998) 4549-4552
Eto kak raz i est' stat'ya, otkuda vzyata fotografiya. Esli zhurnal Vam nedostupen, svobodnaya versiya zdes': http://arxiv.org/abs/physics/9805038
Na stat'yu uzhe 190 ssylok, a eto ochen' horoshii pokazatel'. V osnovnom, konechno, teoreticheskie, no est' i takie:
"Experimental test for the conductivity properties from the Casimir force between metal and semiconductor", F.Chen et.al., Phys. Rev. A 74, 022103 (2006)
"Measurement of the Casimir Force between Dissimilar Metals", R. S. Decca et.al., Phys. Rev. Lett. 91, 050402 (2003)
"Precision measurement of the Casimir force using gold surfaces", B. W. Harris, F. Chen, and U. Mohideen, Phys. Rev. A 62, 052109 (2000)
"Improved precision measurement of the Casimir force", Anushree Roy, Chiung-Yuan Lin, and U. Mohideen, Phys. Rev. D 60, 111101 (1999)
Est' i kritika etih izmerenii, na kotoruyu avtory argumentirovanno otvechayut:
Comment on "Precision Measurement of the Casimir Force from 0.1 to 0.9 μm", S. K. Lamoreaux, Phys. Rev. Lett. 83, 3340 - 3340 (1999)
"Mohideen and Roy Reply", U. Mohideen and A. Roy, Phys. Rev. Lett. 83, 3341 - 3341 (1999)
S uvazheniem,
Dima
- Re[3]: Sila iz pustoty: effekt Kazimira (M. Yu. Yakimov, 4.01.2007 23:42, 21 Bait) Bol'shoe spasibo za bi
- Re[3]: Sila iz pustoty: effekt Kazimira
(M. Yu. Yakimov,
4.01.2007 23:53, 493 Bait, otvetov: 2)
Bol'shoe spasibo za bibliografiyu, no v rezul'taty Phys. Rev. Lett., 81, 4549 ya ne veryu. U nih davlenie ostatochnogo gaza slishkom vysokoe - 0,05 mm.rt.st. Pri takom davleniii vblizi stenki na sharik budet deistvovat' neskompensirovannayasila,vyzyvaemaya udarami molekul ostatochnogo gaza, po poryadku velichiny primerno sootvetstvuyushaya tomu, chto nameryali avtory etoi stat'i. Stoit tol'ko udivlyat'sya tomu, kak eto sil'no reklamiruyut, ne davaya sebe truda razobrat'sya, chto zhe vse-taki izmereno.
- >> Re[4]: Sila iz pustoty: effekt Kazimira
(Dmitrii Docenko,
5.01.2007 14:34, 1.4 KBait, otvetov: 1)
Ya srazu skazhu, chto ne specialist v etoi oblasti (stat'yu tozhe ne chital poka). No nablyudeniya yakoby sovpadayut s teoreticheskoi model'yu na urovne 1%! A dlya togo, chtoby raznost'
davlenii smogla vyglyadet' kak effekt Kazimira, ona ne tol'ko dolzhna imet' takuyu zhe funkcional'nuyu zavisimost' ot rasstoyaniya mezhdu poverhnostei, no i imet' tochno neobhodimuyu
amplitudu (kotoraya k tomu zhe zavisit ot davleniya).
Prikinuv chisla, poluchaetsya vot chto. Pri davlenii 0.05 mm.rt.st. imeem koncentraciyu atomov okolo 2*10^15 v sm^3, to est' odin atom vozduha nahoditsya v kube storonoi poryadka 0.1 mkm. Takim obrazom, mezhdu sharikom i stenkoi nahoditsya sravnitel'no nebol'shoe kolichestvo atomov, kotoroe lineino umen'shaetsya s umen'sheniem rasstoyaniya mezhdu sharikom i stenkoi. Davlenie vozduha so storony stenki togda dolzhno takzhe lineino umen'shatsya; a raznost' davlenii (i izmeryaemaya sila) - lineino uvelichivat'sya (poka razmer sharika mnogo bol'she rasstoyaniya do stenki). Vrode by tak.
A nablyudaetsya kubicheskaya zavisimost' (sovsem nelineinaya, po krainei mere). Po idee, odno eto isklyuchaet vozmozhnost' togo, chto nablyudaemaya sila voznikaet iz-za raznicy davlenii.
Naschet poryadka velichiny - kak Vy ego ocenili? Sobstvenno davlenie est' 0.05*133 Pa = 7 Pa. Sootvetstvenno, sila, kotoraya davit na odnu storonu sharika, est' primerno 10 mN. Kak u Vas poluchilis' pN?
S uvazheniem,
Dima - Re[5]: Sila iz pustoty: effekt Kazimira
(M. Yu. Yakimov,
5.01.2007 23:11, 810 Bait)
Pochemu millin'yutony? Ploshad' poperechnogo secheniya sharika - poryadka 10^-8 m^2. Podstavlyaya 7 Pa poluchaem 70 nanon'yutonov. Eto, konechno, slishkom grubaya ocenka, t.e. sil'no sverhu, noya inapisal primerno. Ya ne ponimayu, kak na fone brounovskogo dvizheniya mozhno uvidet' gorazdo men'shuyu silu. Chtoby ee pochuvstvovat', nuzhno, vo-pervyh, otkachat' do 10^-8, i ohladit' do ves'ma nizkoi temperatury. Pri etom nado takzhe garantirovat' otsutstvie molekulyarnyh sloev vody na izuchaemyh poverhnostyah (chto ves'ma trudno sdelat'), chtoby isklyuchit' Van-der-Vaal'sovy sily. Mnogo eshe eksperimental'nyh trudnostei, o kotoryh v stat'e ni slova. Mozhet, konechno, ya oshibayus', ya tozhe ne specialist v etih voprosah, no nemnogo razbirayus' v tehnike fizicheskogo eksperimenta, a s etoi tochki zreniya rabota vyglyadit podozritel'noi.
- Re: Sila iz pustoty: effekt Kazimira
(poojapandit poojapandit,
9.02.2023 11:06, 2.5 KBait, otvetov: 1)
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