Mga Archive ng Kategorya: Pisika

Physics ay ang aking unang pag-ibig. Naglalaman ang kategoryang ito ang mga post na pinakamalapit sa aking puso. Dalawampung taon mula ngayon, kung ang blog na ito survives, kategoryang ito ay marahil pindutin nang matagal ang aking pinaka-enduring mga pananaw. At dalawang daang taon mula ngayon, kung ako ay remembered sa lahat, ito ay para sa mga pananaw na ito; hindi para sa uri ng tao Ako, ang pera gumawa ako, o anumang bagay. Para sa aking una at huling pag-ibig lamang…

Pagdama, Pisika at ang Tungkulin ng Banayad sa Pilosopiya

Katotohanan, bilang pakiramdam namin ito, ay hindi masyadong real. Ang mga bituin namin nakikita sa kalangitan sa gabi, halimbawa, ay hindi talaga doon. Maaaring ang mga ito ay inilipat o kahit na namatay sa oras na makuha namin upang makita ang mga ito. Unreality Ito ay dahil sa ang oras na aabutin para sa ilaw mula sa malayong mga bituin at galaxy upang maabot sa amin. Alam namin na ito ng pagkaantala.

Kahit na ang araw na alam namin nang mahusay ay nasa walong minuto lumang sa oras na makita namin ito. Katunayan na ito ay tila hindi ipakita lalo na libingan epistemological mga problema – kung gusto naming malaman kung ano ang nangyayari sa sa sun ngayon, lahat ng mayroon kaming gawin ay maghintay para sa walong minuto. Kami lamang magkaroon ng 'tama’ para sa distortions sa aming pagdama dahil sa bilis may hangganan ng liwanag bago maaari naming pinagkakatiwalaan kung ano ang nakikita namin. Ang parehong phenomenon sa nakakakita ay may isang mas mababang-kilalang paghahayag sa paraan ng paglilipat ng perceive namin bagay. Ang ilang mga lumitaw makalangit na mga katawan na waring sila ay gumagalaw nang maraming beses sa bilis ng liwanag, samantalang ang kanilang mga 'real’ bilis ay dapat na isang pulutong mas mababa kaysa sa na.

Ano ang kamangha-mangha (at bihira na naka-highlight) ay na pagdating sa sensing paggalaw, Hindi namin maaaring i-back-Kalkulahin sa parehong uri ng paraan na magagawa namin upang itama para sa pagkaantala ng pagmamasid na bahagi ng araw. Kung makakita kami ng isang celestial body gumagalaw sa isang improbably mataas na bilis, hindi namin maaaring kalkulahin kung gaano kabilis o kahit na sa kung ano ang direksyon ito ay 'talaga’ paglipat nang hindi muna pagkakaroon upang gumawa ng ilang higit pang mga palagay.

Pinili ng Einstein upang malutas ang problema sa pamamagitan ng pagpapagamot ng pagdama bilang magulong at inventing bagong pangunahing katangian ng sa arena ng pisika – sa paglalarawan ng espasyo at oras. Isa pangunahing ideya ng mga Espesyal na Teorya ng Relativity ay ang paniwala ng isang maayos na pagkakasunud-sunod ng mga kaganapan sa panahon ng tao ay kailangang mai-inabandunang. Sa katunayan, dahil nangangailangan ng panahon para sa ilaw mula sa isang kaganapan sa isang malayong lugar upang maabot sa amin, at para sa amin upang malaman ito, ang konsepto ng 'ngayon’ hindi na gumagawa ng anumang mga kahulugan, halimbawa, kapag nagsasalita kami ng isang sunspot lumilitaw sa ibabaw na bahagi ng araw lamang sa sandaling ito na ang mga astronomo ay sinusubukang i-Kuhanan ng larawan ito. Simultaneity ay may kaugnayan.

Einstein sa halip redefined simultaneity pamamagitan ng paggamit ng instants sa oras na nakita naming ang kaganapan. Pagkakita, gaya ng nilinaw niya ito, nagsasangkot ng isang round-trip sa paglalakbay ng liwanag katulad ng radar detection. Ipadala namin ang isang signal na naglalakbay sa bilis ng liwanag, at maghintay para sa pagmuni-muni. Kung ang masasalamin pulse mula sa dalawang mga kaganapan umabot sa amin sa parehong mga instant, pagkatapos ay ang mga ito ay sabay-sabay na. Ngunit ang isa pang paraan sa pagtingin sa ito ay simpleng upang tawagan ang dalawang mga kaganapan 'sabay-sabay na’ kung ang ilaw mula sa mga ito umabot sa amin sa parehong mga instant. Sa ibang salita, maaari naming gamitin ang liwanag na nabuo sa pamamagitan ng mga bagay sa ilalim ng pagmamasid sa halip ng pagpapadala ng mga signal sa kanila at pagtingin sa pagmuni-muni.

Ang pagkakaibang ito ay maaaring tunog tulad ng isang hair-paghahati ng pang technicality, ngunit ginagawa nito gumawa ng isang malaking pagkakaiba sa mga hula maaari naming gumawa. Mga resulta ng pagpili Einstein sa isang mathematical larawan na may maraming mga kanais-nais na mga katangian, kabilang na ng paggawa ng higit pang theoretical pagbuo ng higit pang mga eleganteng. Ngunit pagkatapos ay, Naniwala Einstein, bilang isang bagay ng pananampalataya ay mukhang ito, na ang mga patakaran na namamahala sa uniberso ay dapat na 'eleganteng.’ Gayunpaman, ang iba pang mga diskarte ay may bentahe pagdating sa naglalarawan ng mga bagay sa paggalaw. Dahil, oo naman, hindi namin ginagamit radar upang makita ang mga bituin sa paggalaw; pakiramdam lamang namin ang mga ilaw (o iba pang mga radiation) darating mula sa kanila. Ngunit ang paggamit ng ganitong uri ng pandama Huwaran, sa halip na 'radar-tulad ng pagkakita,’ upang ilarawan ang mga resulta ng uniberso sa isang hindi maganda mathematical larawan. Einstein ay hindi aprubahan!

Ang mathematical pagkakaiba spawns iba't ibang mga philosophical stances, na siya namang percolate sa pag-unawa ng ating mga pisikal na larawan ng katotohanan. Bilang isang paglalarawan, ipagpalagay na-oobserbahan, sa pamamagitan ng isang teleskopyo radyo, dalawang bagay sa kalangitan, may humigit-kumulang sa parehong hugis, laki at mga katangian. Ang tanging bagay na alam namin para bang ay na ang mga radio waves mula sa mga dalawang iba't ibang mga punto sa kalangitan maabot sa amin sa parehong mga instant sa oras. Maaari lamang kami hulaan kapag nagsimula ang mga wave kanilang journeys.

Kung ipinapalagay namin (bilang regular naming gawin) Nagsimula na ang mga wave sa paglalakbay humigit-kumulang sa parehong mga instant sa oras, magtapos ka namin gamit ang isang larawan ng dalawang 'real’ simetriko lobe higit pa o mas mababa sa paraang nakikita ang mga ito. Ngunit mayroong isa pang, iba't ibang mga posibilidad at iyon ay na ang mga wave nagmula mula sa parehong bagay (na kung saan ay sa paggalaw) sa dalawang magkaibang mga instants sa oras, pag-abot ng teleskopyo sa parehong mga instant. Posibilidad na ito ay Bukod pa rito ipapaliwanag Spectral at temporal mga katangian ng naturang mga simetriko na pinagkukunan ng radyo. Kaya kung alin sa mga dalawang mga larawan ay dapat na lubos naming bilang tunay? Dalawang simetriko mga bagay tulad ng nakikita namin ang mga ito o isa sa bagay na gumagalaw sa ganoong paraan tulad ng sa bigyan kami ng impresyon na ang? Ba talagang mahalaga kung aling isa ay 'real'? Nagbibigay ba ang 'real’ ibig sabihin kahit ano sa kontekstong ito?

Espesyal na Relativity ay nagbibigay sa isang unambiguous sagot sa tanong na ito. Ang matematika tuntunin out ang posibilidad ng isang solong bagay na gumagalaw sa naturang fashion bilang upang gayahin ng dalawang bagay. Mahalaga, kung ano ang nakikita namin ay kung ano ang out doon. Pa, kung tinutukoy namin ang mga kaganapan sa pamamagitan ng kung ano perceive namin, ang tanging philosophical tindig na saysay ay ang isa na disconnects ang sensed katotohanan mula sa mga sanhi na namamalagi sa likod kung ano ang sensed.

Alisin sa pagkakakonekta ito ay hindi bihira sa philosophical mga paaralan ng pag-iisip. Phenomenalism, halimbawa, pagpipigil sa view na espasyo at oras ay hindi layunin katotohanan. Sila lamang ang medium ng aming pagdama. Ang lahat ng mga phenomena na mangyari sa espasyo at oras ay lamang bundle ng aming pagdama. Sa ibang salita, espasyo at oras ay nagbibigay-malay constructs na nagmumula sa pagdama. Kaya, ang lahat ng mga pisikal na mga katangian na ascribe naming espasyo at oras ay maaari lamang ilapat sa phenomenal katotohanan (ang katotohanan ng 'mga bagay-in-the-mundo’ bilang pakiramdam namin ito. Ang napapailalim na katotohanan (na hold ang pisikal na sanhi ng aming pagdama), sa pamamagitan ng kaibahan, nananatiling lampas sa aming mga nagbibigay-malay na pag-abot.

Ngunit mayroong isang bangin sa pagitan ng mga tanawin ng pilosopiya at modernong pisika. Hindi para sa walang ginawa ng Nobel Prize winning na physicist, Steven Weinberg, magtaka, sa kanyang Dreams aklat ng isang Final Teorya, bakit ang kontribusyon mula sa pilosopiya sa physics ay hindi naging kaya nakakagulat na maliit. Marahil ito ay dahil sa pisika ay may pa na dumating sa mga tuntunin sa ang katunayan na pagdating sa nakikita sa uniberso, walang ganoong bagay bilang isang optical ilusyon – na kung saan ay marahil kung ano ang nilalayong Goethe kapag sinabi niya, 'Optical ilusyon ay optical katotohanan.’

Ang pagkakaiba (o kulang nito) sa pagitan ng optical ilusyon at katotohanan ay isa sa pinakamatagal debate sa pilosopiya. Pagkatapos ng lahat, ito ay tungkol sa pagkakaiba sa pagitan ng kaalaman at katotohanan. Kaalaman ay isinasaalang-alang ang aming mga tanawin tungkol sa isang bagay na, sa katotohanan, ay 'aktwal na ang kaso.’ Sa ibang salita, kaalaman ay isang pagsasalamin, o isang sakit sa imahe ng isang bagay na panlabas, tulad ng ipinapakita sa figure sa ibaba.

ExternalToBrain

Sa larawan na ito, ang itim na arrow ay kumakatawan sa mga proseso ng paglikha ng kaalaman, na kabilang ang pagdama, nagbibigay-malay na gawain, at ang exercise ng purong dahilan. Ito ang larawan na pisika ay dumating upang tanggapin. Habang kumikilala na ang aming pagdama ay maaaring imperfect, Ipinagpapalagay ng pisika na maaari naming makakuha ng mas malapit at mas malapit sa mga panlabas na katotohanan sa pamamagitan ng lalong mas pinong pag-eksperimento, at, mas mahalaga, sa pamamagitan ng mas mahusay na theorization. Ang Espesyal at Pangkalahatang teoryang ng Relativity ang mga halimbawa ng makikinang na mga application ng pananaw na ito ng mga katotohanan kung saan simpleng pisikal na mga prinsipyo ay relentlessly pursued gamit ang mabigat machine ng purong dahilan upang ang kanilang mga lohikal na kongklusyon hindi maiwasan.

Ngunit mayroong isa pang, alternatibong tanawin ng kaalaman at katotohanan na naging sa paligid para sa isang mahabang panahon. Ito ang view na iyon Bumabati pinaghihinalaang katotohanan bilang isang panloob na nagbibigay-malay na representasyon ng aming madaling makaramdam input, bilang isinalarawan sa ibaba.

AbsolutelToBrain

Sa view na ito, kaalaman at napansing katotohanan ay parehong panloob na nagbibigay-malay constructs, bagaman na dumating kami sa tingin ng mga ito bilang mga hiwalay na. Ano ang mga panlabas na ito ay hindi ang katotohanan bilang perceive namin ito, ngunit isang unknowable entity na nagbibigay sa pagtaas sa pisikal na sanhi sa likod ng pandama input. Sa paglalarawan, ang unang arrow ay kumakatawan sa proseso ng sensing, at ang pangalawang arrow ay kumakatawan sa mga nagbibigay-malay at lohikal na hakbang na pagdadahilan. Upang ilapat ang pananaw na ito ng mga katotohanan at kaalaman, mayroon kaming hulaan ang likas na katangian ng ganap na katotohanan, unknowable dahil ito ay. Ang isang posibleng kandidato para sa ganap na katotohanan ay Newtonian Mechanics, kung saan ay nagbibigay ng makatwirang hula para sa aming mga pinaghihinalaang katotohanan.

Upang ibuod, kapag sinusubukan naming panghahawakan ang distortions dahil sa pagdama, mayroon kaming dalawang mga pagpipilian, o dalawang posibleng philosophical stances. Ang isa ay upang tanggapin ang mga distortions bilang bahagi ng aming espasyo at oras, bilang Special Relativity gumagana. Ang iba pang pagpipilian ay ang ipinapalagay na mayroong isang 'mas mataas’ katotohanan na naiiba mula sa aming sensed katotohanan, na kung saan ang mga katangian ng aming makakaya lamang haka-haka. Sa ibang salita, isang opsyon ay upang mabuhay kasama ang pagbaluktot, habang ang iba pa ay upang ipanukala ang edukado guesses para sa mas mataas na katotohanan. Wala sa alinman sa mga pagpipiliang ito ay partikular na kaakit-akit. Subalit ang paghula landas ay katulad ng sa view tinatanggap sa phenomenalism. Mayroon din humahantong sa natural paano katotohanan tiningnan sa nagbibigay-malay Neuroscience, Pag-aaral na ang biological mekanismo sa likod ng cognition.

Ang timpla sa kuwentong ito ng liwanag at katotohanang ay mukhang naming na-kilala ang lahat ng ito para sa isang mahabang panahon. Ang papel na ginagampanan ng ilaw sa paglikha ng aming mga katotohanan o uniberso ay nasa puso ng Western pag-iisip sa relihiyon. Ang isang uniberso malaya ng liwanag ay hindi lamang ang isang mundo kung saan ng iyong paglipat ng off ang mga ilaw. Ito ay sa katunayan isang uniberso malaya ng sarili nito, isang uniberso na hindi umiiral. Ito ay nasa kontekstong ito na mayroon kami upang maunawaan ang karunungan sa likod ng mga pahayag na 'ang lupa ay walang anyo, at walang silbi’ hanggang sanhi ng Diyos liwanag upang maging, sa pamamagitan ng sinasabi 'Magkaroon liwanag.’

Ang Koran din sabi, 'Allah ay ang liwanag ng langit at lupa,’ na kung saan ay mirrored sa isa sa mga sinaunang kasulatan Hindu: 'Lead sa akin mula sa kadiliman sa liwanag, humantong sa akin mula sa unreal sa real.’ Ang papel na ginagampanan ng ilaw sa pagkuha sa amin mula sa unreal walang silbi (ang nothingness) sa isang katotohanan ay sa katunayan naunawaan sa loob ng mahabang, mahabang panahon. Posible ba na ang sinaunang mga banal at mga propeta alam ang mga bagay na kami ay ngayon lamang simula upang buksan sa lahat ng aming mga dapat paglago sa kaalaman?

May mga parallel sa pagitan ng mga noumenal-phenomenal pagkakaiba ng Kant at ang phenomenalists sa ibang pagkakataon, at ang Brahman-Maya pagkakaiba sa Advaita. Karunungan sa likas na katangian ng katotohanan mula sa repertoire ng kabanalan ay reinvented sa modernong Neuroscience, na itinuturing ng katotohanan bilang isang nagbibigay-malay na pagkatawan na ginawa ng utak. Ang utak ay gumagamit ng madaling makaramdam input, memory, malay, at kahit na wika pati na sangkap sa concocting aming kahulugan ng katotohanan. Pananaw na ito ng katotohanan, gayunman, ay physics ng isang bagay ay hindi pa rin dumalo sa mga tuntunin sa. Ngunit sa lawak na arena nito (espasyo at oras) ay isang bahagi ng katotohanan, pisika nito ay hindi immune sa pilosopiya ng.

Sa katunayan, bilang itulak namin ang mga hangganan ng ating kaalaman sa karagdagang at karagdagang, pagtuklas ng mga kami ay hitherto unsuspected at madalas nakakagulat interconnections sa pagitan ng iba't ibang sangay ng pantao pagsisikap. Pa, Maaari kung paano ang iba't ibang mga domain ng aming kaalaman maging independent ng bawat isa kung ang lahat ng kaalaman ay may kinikilingang? Kung kaalaman ay tanging ang nagbibigay-malay na representasyon ng aming mga karanasan? Ngunit pagkatapos ay, ito ay ang modernong fallacy sa tingin kaalaman na ang aming panloob na representasyon ng isang panlabas na katotohanan, at samakatuwid ay naiiba mula sa ito. Sa halip, pagkilala at paggawa ng paggamit ng interconnections kabilang sa mga iba't ibang mga domain ng gawaing pantao ay maaaring maging mahalaga para sa paunang kinakailangan ang sumunod na baitang sa pagbuo ng aming mga sama-karunungan.

Box: Einstein ni TrainAng isa sa mga sikat na pag-iisip ng mga eksperimento Einstein ay naglalarawan ng mga pangangailangan sa pag-isipang muli kung ano ang ibig sabihin namin sa pamamagitan ng sabay-sabay na mga kaganapan. Inilalarawan nito ang isang high-speed na tren rushing sa kahabaan ng isang tuwid na track nakalipas na isang maliit na istasyon bilang isang tao ay nakatayo sa platform ng istasyon nanonood ito mapabilis sa pamamagitan ng. Upang kanyang pagkamangha, bilang ng tren pumasa sa kanya, strike dalawang lightening bolts ang track tabi ng alinman sa dulo ng tren! (Maginhawang, para sa ibang pagkakataon investigators, umalis sila magsunog ng mga marka pareho sa tren at sa lupa.)

Upang ang tao, Mukhang ito na strike ang dalawang lightening bolts sa eksaktong kapareho sandali. Ibang Pagkakataon, ang mga marka sa ground ng tren track magbunyag na ang mga spot kung saan struck ang lightening ay eksaktong may parehong distansiyang mula sa kanya. Simula noon ang lightening bolts naglakbay sa parehong distansya patungo sa kanya, at dahil sila ay nagpakita sa mga tao na mangyayari sa eksaktong kapareho sandali, siya ay walang dahilan hindi upang tapusin na ang lightening bolts struck sa eksaktong kapareho sandali. Sila ay sabay-sabay na.

Gayunpaman, ipagpalagay ng kaunti sa ibang pagkakataon, ang tao ay nakakatugon na pangbabae pasahero na nangyari na nakaupo sa buffet kotse, eksakto sa gitna ng tren, at naghahanap out ng window sa panahon na ang lightening bolts struck. Pasahero na ito ay nagsasabi sa kanya na siya nakita pindutin ang unang lightening tornilyo sa lupa malapit sa engine sa harap ng tren bahagyang mas maaga kapag pindutin ang pangalawang isa sa lupa sa tabi ng luggage kotse sa hulihan ng tren.

Ang epekto ay walang kinalaman sa ang distansya sa liwanag ay nagkaroon upang maglakbay, bilang parehong mga babae at ang mga tao ay may parehong distansiyang sa pagitan ng dalawang mga punto na ang lightening hit. Pa nila na-obserbahan ang pagkakasunod-sunod ng mga kaganapan nang bahagyang naiiba.

Ang hindi pagkakasundo ng tiyempo ng mga kaganapan ay hindi maiwasan, Einstein sabi, bilang mga babae ay may bisa sa paglipat patungo sa punto kung saan ang flash ng lightening pindutin malapit sa engine -and ang layo mula sa punto kung saan ang flash ng lightening hit sa tabi ng luggage kotse. Sa maliit na halaga ng oras na aabutin para sa liwanag ray upang maabot ang ginang ng bansa, dahil ang galaw ng tren, ang distansya ang unang flash ay dapat maglakbay sa kanyang Pinaliliit, at ang distansya ay dapat maglakbay ang pangalawang flash lumalaki.

Katunayan na ito ay hindi maaaring napansin sa kaso ng tren at mga eroplano, ngunit pagdating sa mga distansya cosmological, simultaneity talaga ay hindi magsagawa ng anumang mga kahulugan. Halimbawa, ang pagsabog ng dalawang malayong supernovae, Nakita bilang sabay-sabay mula sa aming vantage point sa earth, ay lalabas sa mga nagaganap sa mga iba't ibang mga kumbinasyon oras mula sa ibang anggolo.

Sa Relativity: Ang Espesyal at Pangkalahatang Teorya (1920), Einstein ilagay ito sa ganitong paraan:

'Araw-reference-katawan (co-ordinate sistema) ay may sarili nitong partikular na oras; maliban kung kami ay sinabi ang reference-katawan na kung saan ang pahayag ng oras ay tumutukoy, walang kahulugan sa isang pahayag ng mga oras ng isang kaganapan.’

Tsunami

The Asian Tsunami two and a half years ago unleashed tremendous amount energy on the coastal regions around the Indian ocean. What do you think would’ve have happened to this energy if there had been no water to carry it away from the earthquake? I mean, if the earthquake (of the same kind and magnitude) had taken place on land instead of the sea-bed as it did, presumably this energy would’ve been present. How would it have manifested? As a more violent earthquake? Or a longer one?

I picture the earthquake (in cross-section) as a cantilever spring being held down and then released. The spring then transfers the energy to the tsunami in the form of potential energy, as an increase in the water level. As the tsunami radiates out, it is only the potential energy that is transferred; the water doesn’t move laterally, only vertically. As it hits the coast, the potential energy is transferred into the kinetic energy of the waves hitting the coast (water moving laterally then).

Given the magnitude of the energy transferred from the epicenter, I am speculating what would’ve happened if there was no mechanism for the transfer. Any thoughts?

Universe – Size and Age

I posted this question that was bothering me when I read that they found a galaxy at about 13 billion light years away. My understanding of that statement is: At distance of 13 billion light years, there was a galaxy 13 billion years ago, so that we can see the light from it now. Wouldn’t that mean that the universe is at least 26 billion years old? It must have taken the galaxy about 13 billion years to reach where it appears to be, and the light from it must take another 13 billion years to reach us.

In answering my question, Martin and Swansont (who I assume are academic phycisists) point out my misconceptions and essentially ask me to learn more. All shall be answered when I’m assimilated, it would appear! 🙂

This debate is published as a prelude to my post on the Big Bang theory, coming up in a day or two.

Mowgli 03-26-2007 10:14 PM

Universe – Size and Age
I was reading a post in http://www.space.com/ stating that they found a galaxy at about 13 billion light years away. I am trying to figure out what that statement means. To me, it means that 13 billion years ago, this galaxy was where we see it now. Isn’t that what 13b LY away means? If so, wouldn’t that mean that the universe has to be at least 26 billion years old? I mean, the whole universe started from one singular point; how could this galaxy be where it was 13 billion years ago unless it had at least 13 billion years to get there? (Ignoring the inflationary phase for the moment…) I have heard people explain that the space itself is expanding. What the heck does that mean? Isn’t it just a fancier way of saying that the speed of light was smaller some time ago?
swansont 03-27-2007 09:10 AM

Quote:

Originally Posted by Mowgli
(Post 329204)
I mean, the whole universe started from one singular point; how could this galaxy be where it was 13 billion years ago unless it had at least 13 billion years to get there? (Ignoring the inflationary phase for the moment…)

Ignoring all the rest, how would this mean the universe is 26 billion years old?

Quote:

Originally Posted by Mowgli
(Post 329204)
I have heard people explain that the space itself is expanding. What the heck does that mean? Isn’t it just a fancier way of saying that the speed of light was smaller some time ago?

The speed of light is an inherent part of atomic structure, in the fine structure constant (alpha). If c was changing, then the patterns of atomic spectra would have to change. There hasn’t been any confirmed data that shows that alpha has changed (there has been the occasional paper claiming it, but you need someone to repeat the measurements), and the rest is all consistent with no change.

Martin 03-27-2007 11:25 AM

To confirm or reinforce what swansont said, there are speculation and some fringe or nonstandard cosmologies that involve c changing over time (or alpha changing over time), but the changing constants thing just gets more and more ruled out.I’ve been watching for over 5 years and the more people look and study evidence the LESS likely it seems that there is any change. They rule it out more and more accurately with their data.So it is probably best to ignore the “varying speed of light” cosmologies until one is thoroughly familiar with standard mainstream cosmology.You have misconceptions Mowgli

  • General Relativity (the 1915 theory) trumps Special Rel (1905)
  • They don’t actually contradict if you understand them correctly, because SR has only a very limited local applicability, like to the spaceship passing by:-)
  • Wherever GR and SR SEEM to contradict, believe GR. It is the more comprehensive theory.
  • GR does not have a speed limit on the rate that very great distances can increase. the only speed limit is on LOCAL stuff (you can’t catch up with and pass a photon)
  • So we can and DO observe stuff that is receding from us faster than c. (It’s far away, SR does not apply.)
  • This was explained in a Sci Am article I think last year
  • Google the author’s name Charles Lineweaver and Tamara Davis.
  • We know about plenty of stuff that is presently more than 14 billion LY away.
  • You need to learn some cosmology so you wont be confused by these things.
  • Also a “singularity” does not mean a single point. that is a popular mistake because the words SOUND the same.
  • A singularity can occur over an entire region, even an infinite region.

Also the “big bang” model doesn’t look like an explosion of matter whizzing away from some point. It shouldn’t be imagined like that. The best article explaining common mistakes people have is this Lineweaver and Davis thing in Sci Am. I think it was Jan or Feb 2005 but I could be a year off. Google it. Get it from your local library or find it online. Best advice I can give.

Mowgli 03-28-2007 01:30 AM

To swansont on why I thought 13 b LY implied an age of 26 b years:When you say that there is a galaxy at 13 b LY away, I understand it to mean that 13 billion years ago my time, the galaxy was at the point where I see it now (which is 13 b LY away from me). Knowing that everything started from the same point, it must have taken the galaxy at least 13 b years to get where it was 13 b years ago. So 13+13. I’m sure I must be wrong.To Martin: You are right, I need to learn quite a bit more about cosmology. But a couple of things you mentioned surprise me — how do we observe stuff that is receding from as FTL? I mean, wouldn’t the relativistic Doppler shift formula give imaginary 1+z? And the stuff beyond 14 b LY away – are they “outside” the universe?I will certainly look up and read the authors you mentioned. Thanks.
swansont 03-28-2007 03:13 AM

Quote:

Originally Posted by Mowgli
(Post 329393)
To swansont on why I thought 13 b LY implied an age of 26 b years:When you say that there is a galaxy at 13 b LY away, I understand it to mean that 13 billion years ago my time, the galaxy was at the point where I see it now (which is 13 b LY away from me). Knowing that everything started from the same point, it must have taken the galaxy at least 13 b years to get where it was 13 b years ago. So 13+13. I’m sure I must be wrong.

That would depend on how you do your calibration. Looking only at a Doppler shift and ignoring all the other factors, if you know that speed correlates with distance, you get a certain redshift and you would probably calibrate that to mean 13b LY if that was the actual distance. That light would be 13b years old.

But as Martin has pointed out, space is expanding; the cosmological redshift is different from the Doppler shift. Because the intervening space has expanded, AFAIK the light that gets to us from a galaxy 13b LY away is not as old, because it was closer when the light was emitted. I would think that all of this is taken into account in the measurements, so that when a distance is given to the galaxy, it’s the actual distance.

Martin 03-28-2007 08:54 AM

Quote:

Originally Posted by Mowgli
(Post 329393)
I will certainly look up and read the authors you mentioned.

This post has 5 or 6 links to that Sci Am article by Lineweaver and Davis

http://scienceforums.net/forum/showt…965#post142965

It is post #65 on the Astronomy links sticky thread

It turns out the article was in the March 2005 issue.

I think it’s comparatively easy to read—well written. So it should help.

When you’ve read the Sci Am article, ask more questions—your questions might be fun to try and answer:-)

Twin Paradox – Take 2

The Twin Paradox is usually explained away by arguing that the traveling twin feels the motion because of his acceleration/deceleration, and therefore ages slower.

But what will happen if the twins both accelerate symmetrically? That is, they start from rest from one space point with synchronized clocks, and get back to the same space point at rest by accelerating away from each other for some time and decelerating on the way back. By the symmetry of the problem, it seems that when the two clocks are together at the end of the journey, at the same point, and at rest with respect to each other, they have to agree.

Then again, during the whole journey, each clock is in motion (accelerated or not) with respect to the other one. In SR, every clock that is in motion with respect to an observer’s clock is supposed run slower. Or, the observer’s clock is always the fastest. So, for each twin, the other clock must be running slower. However, when they come back together at the end of the journey, they have to agree. This can happen only if each twin sees the other’s clock running faster at some point during the journey. What does SR say will happen in this imaginary journey?

(Note that the acceleration of each twin can be made constant. Have the twins cross each other at a high speed at a constant linear deceleration. They will cross again each other at the same speed after sometime. During the crossings, their clocks can be compared.)

Unreal Time

Farsight wrote:Time is a velocity-dependent subjective measure of event succession rather than something fundamental – the events mark the time, the time doesn’t mark the events. This means the stuff out there is space rather than space-time, and is an “aether” veiled by subjective time.

I like your definition of time. It is close to my own view that time is “unreal.” It is possible to treat space as real and space-time as something different, as you do. This calls for some careful thought. I will outline my thinking in this post and illustrate it with an example, if my friends don’t pull me out for lunch before I can finish. :)

The first question we need to ask ourselves is why space and time seem coupled? The answer is actually too simple to spot, and it is in your definition of time. Space and time mix through our concept of velocity and our brain’s ability to sense motion. There is an even deeper connection, which is that space is a cognitive representation of the photons inputs to our eyes, but we will get to it later.

Let’s assume for a second that we had a sixth sense that operated at an infinite speed. That is, if star explodes at a million light years from us, we can sense it immediately. We will see it only after a million years, but we sense it instantly. I know, it is a violation of SR, cannot happen and all that, but stay with me for a second. Now, a little bit of thinking will convince you that the space that we sense using this hypothetical sixth sense is Newtonian. Here, space and time can be completely decoupled, absolute time can be defined etc. Starting from this space, we can actually work out how we will see it using light and our eyes, knowing that the speed of light is what it is. It will turn out, clearly, that we seen events with a delay. That is a first order (or static) effect. The second order effect is the way we perceive objects in motion. It turns out that we will see a time dilation and a length contraction (for objects receding from us.)

Let me illustrate it a little further using echolocation. Assume that you are a blind bat. You sense your space using sonar pings. Can you sense a supersonic object? If it is coming towards you, by the time the reflected ping reaches you, it has gone past you. If it is going away from you, your pings can never catch up. In other words, faster than sound travel is “forbidden.” If you make one more assumption – the speed of the pings is the same for all bats regardless of their state of motion – you derive a special relativity for bats where the speed of sound is the fundamental property of space and time!

We have to dig a little deeper and appreciate that space is no more real than time. Space is a cognitive construct created out of our sensory inputs. If the sense modality (light for us, sound for bats) has a finite speed, that speed will become a fundamental property of the resultant space. And space and time will be coupled through the speed of the sense modality.

This, of course, is only my own humble interpretation of SR. I wanted to post this on a new thread, but I get the feeling that people are a little too attached to their own views in this forum to be able to listen.

Leo wrote:Minkowski spacetime is one interpretation of the Lorentz transforms, but other interpretations, the original Lorentz-Poincaré Relativity or modernized versions of it with a wave model of matter (LaFreniere or Close or many others), work in a perfectly euclidean 3D space.

So we end up with process slowdown and matter contraction, but NO time dilation or space contraction. The transforms are the same though. So why does one interpretation lead to tensor metric while the others don’t? Or do they all? I lack the theoretical background to answer the question.

Hi Leo,

If you define LT as a velocity dependent deformation of an object in motion, then you can make the transformation a function of time. There won’t be any warping and complications of metric tensors and stuff. Actually what I did in my book is something along those lines (though not quite), as you know.

The trouble arises when the transformation matrix is a function of the vector is transforming. So, if you define LT as a matrix operation in a 4-D space-time, you can no longer make it a function of time through acceleration any more than you can make it a function of position (as in a velocity field, for instance.) The space-time warping is a mathematical necessity. Because of it, you lose coordinates, and the tools that we learn in our undergraduate years are no longer powerful enough to handle the problem.

Of Rotation, LT and Acceleration

In the “Philosophical Implications” forum, there was an attempt to incorporate acceleration into Lorentz transformation using some clever calculus or numerical techniques. Such an attempt will not work because of a rather interesting geometric reason. I thought I would post the geometric interpretation of Lorentz transformation (or how to go from SR to GR) here.

Let me start with a couple of disclaimers. First of, what follows is my understanding of LT/SR/GR. I post it here with the honest belief that it is right. Although I have enough academic credentials to convince myself of my infallibility, who knows? People much smarter than me get proven wrong every day. And, if we had our way, we would prove even Einstein himself wrong right here in this forum, wouldn’t we? :D Secondly, what I write may be too elementary for some of the readers, perhaps even insultingly so. I request them to bear with it, considering that some other readers may find it illuminating. Thirdly, this post is not a commentary on the rightness or wrongness of the theories; it is merely a description of what the theories say. Or rather, my version of what they say. With those disclaimers out of the way, let’s get started…

LT is a rotation in the 4-D space-time. Since it not easy to visualize 4-D space-time rotation, let’s start with a 2-D, pure space rotation. One fundamental property of a geometry (such as 2-D Euclidean space) is its metric tensor. The metric tensor defines the inner product between two vectors in the space. In normal (Euclidean or flat) spaces, it also defines the distance between two points (or the length of a vector).

Though the metric tensor has the dreaded “tensor” word in its name, once you define a coordinate system, it is only a matrix. For Euclidean 2-D space with x and y coordinates, it is the identity matrix (two 1’s along the diagonal). Let’s call it G. The inner product between vectors A and B is A.B = Trans(A) G B, which works out to be a_1b_1+a_2b_2. Distance (or length of A) can be defined as \sqrt{A.A}.

So far in the post, the metric tensor looks fairly useless, only because it is the identity matrix for Euclidean space. SR (or LT), on the other hand, uses Minkowski space, which has a metric that can be written with [-1, 1, 1, 1] along the diagonal with all other elements zero – assuming time t is the first component of the coordinate system. Let’s consider a 2-D Minkowski space for simplicity, with time (t) and distance (x) axes. (This is a bit of over-simplification because this space cannot handle circular motion, which is popular in some threads.) In units that make c = 1, you can easily see that the invariant distance using this metric tensor is \sqrt{x^2 - t^2}.

Continued…

The Unreal Universe — Discussion with Gibran

Hi again,You raise a lot of interesting questions. Let me try to answer them one by one.

You’re saying that our observations of an object moving away from us would look identical in either an SR or Galilean context, and therefore this is not a good test for SR.

What I’m saying is slightly different. The coordinate transformation in SR is derived considering only receding objects and sensing it using radar-like round trip light travel time. It is then assumed that the transformation laws thus derived apply to all objects. Because the round trip light travel is used, the transformation works for approaching objects as well, but not for things moving in other directions. But SR assumes that the transformation is a property of space and time and asserts that it applies to all moving (inertial) frames of reference regardless of direction.

We have to go a little deeper and ask ourselves what that statement means, what it means to talk about the properties of space. We cannot think of a space independent of our perception. Physicists are typically not happy with this starting point of mine. They think of space as something that exists independent of our sensing it. And they insist that SR applies to this independently existing space. I beg to differ. I consider space as a cognitive construct based on our perceptual inputs. There is an underlying reality that is the cause of our perception of space. It may be nothing like space, but let’s assume, for the sake of argument, that the underlying reality is like Galilean space-time. How would be perceive it, given that we perceive it using light (one-way travel of light, not two-way as SR assumes)? It turns out that our perceptual space would have time dilation and length contraction and all other effect predicted by SR. So my thesis is that the underlying reality obeys Galilean space-time and our perceptual space obeys something like SR. (It is possible that if I assume that our perception uses two-way light travel, I may get SR-like transformation. I haven’t done it because it seems obvious to me that we perceive a star, for instance, by sensing the light from it rather than flashing a light at it.)

This thesis doesn’t sit well with physicists, and indeed with most people. They mistake “perceptual effects” to be something like optical illusions. My point is more like space itself is an illusion. If you look at the night sky, you know that the stars you see are not “real” in the sense that they are not there when you are looking at them. This is simply because the information carrier, namely light, has a finite speed. If the star under observation is in motion, our perception of its motion is distorted for the same reason. SR is an attempt to formalize our perception of motion. Since motion and speed are concepts that mix space and time, SR has to operate on “space-time continuum.” Since SR is based on perceptual effects, it requires an observer and describes motion as he perceives it.

But are you actually saying that not a single experiment has been done with objects moving in any other direction than farther away? And what about experiments on time dilation where astronauts go into space and return with clocks showing less elapsed time than ones that stayed on the ground? Doesn’t this support the ideas inherent in SR?

Experiments are always interpreted in the light of a theory. It is always a model based interpretation. I know that this is not a convincing argument for you, so let me give you an example. Scientists have observed superluminal motion in certain celestial objects. They measure the angular speed of the celestial object, and they have some estimate of its distance from us, so they can estimate the speed. If we didn’t have SR, there would be nothing remarkable about this observation of superluminality. Since we do have SR, one has to find an “explanation” for this. The explanation is this: when an object approaches us at a shallow angle, it can appear to come in quite a bit faster than its real speed. Thus the “real” speed is subluminal while the “apparent” speed may be superluminal. This interpretation of the observation, in my view, breaks the philosophical grounding of SR that it is a description of the motion as it appears to the observer.

Now, there are other observations of where almost symmetric ejecta are seen on opposing jets in symmetric celestial objects. The angular speeds may indicate superluminality in both the jets if the distance of the object is sufficiently large. Since the jets are assumed to be back-to-back, if one jet is approaching us (thereby giving us the illusion of superluminality), the other jet has bet receding and can never appear superluminal, unless, of course, the underlying motion is superluminal. The interpretation of this observation is that the distance of the object is limited by the “fact” that real motion cannot be superluminal. This is what I mean by experiments being open to theory or model based interpretations.

In the case of moving clocks being slower, it is never a pure SR experiment because you cannot find space without gravity. Besides, one clock has to be accelerated or decelerated and GR applies. Otherwise, the age-old twin paradox would apply.

I know there have been some experiments done to support Einstein’s theories, like the bending of light due to gravity, but are you saying that all of them can be consistently re-interpreted according to your theory? If this is so, it’s dam surprising! I mean, no offense to you – you’re obviously a very bright individual, and you know much more about this stuff than I do, but I’d have to question how something like this slipped right through physicists’ fingers for 100 years.

These are gravity related questions and fall under GR. My “theory” doesn’t try to reinterpret GR or gravity at all. I put theory in inverted quotes because, to me, it is a rather obvious observation that there is a distinction between what we see and the underlying causes of our perception. The algebra involved is fairly simple by physics standards.

Supposing you’re right in that space and time are actually Galilean, and that the effects of SR are artifacts of our perception. How then are the results of the Michelson-Morley experiments explained? I’m sorry if you did explain it in your book, but it must have flown right over my head. Or are we leaving this as a mystery, an anomaly for future theorists to figure out?

I haven’t completely explained MMX, more or less leaving it as a mystery. I think the explanation hinges on how light is reflected off a moving mirror, which I pointed out in the book. Suppose the mirror is moving away from the light source at a speed of v in our frame of reference. Light strikes it at a speed of c-v. What is the speed of the reflected light? If the laws of reflection should hold (it’s not immediately obvious that they should), then the reflected light has to have a speed of c-v as well. This may explain why MMX gives null result. I haven’t worked out the whole thing though. I will, once I quit my day job and dedicate my life to full-time thinking. :-)

My idea is not a replacement theory for all of Einstein’s theories. It’s merely a reinterpretation of one part of SR. Since the rest of Einstein’s edifice is built on this coordinate transformation part, I’m sure there will be some reinterpretation of the rest of SR and GR also based on my idea. Again, this is a project for later. My reinterpretation is not an attempt to prove Einstein’s theories wrong; I merely want to point out that they apply to reality as we perceive it.

Overall, it was worth the $5 I payed. Thanks for the good read. Don’t take my questions as an assault on your proposal – I’m honestly in the dark about these things and I absolutely crave light (he he). If you could kindly answer them in your spare time, I’d love to share more ideas with you. It’s good to find a fellow thinker to bounce cool ideas like this off of. I’ll PM you again once I’m fully done the book. Again, it was a very satisfying read.

Thanks! I’m glad that you like my ideas and my writing. I don’t mind criticism at all. Hope I have answered most of your questions. If not, or if you want to disagree with my answers, feel free to write back. Always a pleasure to chat about these things even if we don’t agree with each other.

– Best regards,
– Manoj

Anti-relativity and Superluminality

Leo wrote:I have some problems with the introductory part though, when you confront light travel effects and relativistic transforms. You correctly state that all perceptual illusions have been cleared away in the conception of Special Relativity, but you also say that these perceptual illusions remained as a subconscious basis for the cognitive model of Special Relativity. Do I understand what you mean or do I get it wrong?

The perceptual effects are known in physics; they are called Light Travel Time effects (LTT, to cook up an acronym). These effects are considered an optical illusion on the motion of the object under observation. Once you take out the LTT effects, you get the “real” motion of the object . This real motion is supposed to obey SR. This is the current interpretation of SR.

My argument is that the LTT effects are so similar to SR that we should think of SR as just a formalization of LTT. (In fact, a slightly erroneous formalization.) Many reasons for this argument:
1. We cannot disentagle the “optical illusion” because many underlying configurations give rise to the same perception. In other words, going from what we see to what is causing our perception is a one to many problem.
2. SR coordinate transformation is partially based on LTT effects.
3. LTT effects are stronger than relativistic effects.

Probably for these reasons, what SR does is to say that what we see is what it is really like. It then tries to mathematically describe what we see. (This is what I meant by a formaliztion. ) Later on, when we figured out that LTT effects didn’t quite match with SR (as in the observation of “apparent” superluminal motion), we thought we had to “take out” the LTT effects and then say that the underlying motion (or space and time) obeyed SR. What I’m suggesting in my book and articles is that we should just guess what the underlying space and time are like and work out what our perception of it will be (because going the other way is an ill-posed one-to-many problem). My first guess, naturally, was Galilean space-time. This guess results in a rather neat and simple explantions of GRBs and DRAGNs as luminal booms and their aftermath.

Discussion on the Daily Mail (UK)

On the Daily Mail forum, one participant (called “whats-in-a-name”) started talking about The Unreal Universe on July 15, 2006. It was attacked fairly viciously on the forum. I happened to see it during a Web search and decided to step in and defend it.

15 July, 2006

Posted by: whats-in-a-name on 15/07/06 at 09:28 AM

Ah, Kek, you’ve given me a further reason to be distracted from what I should be doing- and I can tell you that this is more interesting at the moment.I’ve been trying to formulate some ideas and there’s one coming- but I’ll have to give it to you in bits.I don’t want to delve into pseudoscience or take the woo-ish road that says that you can explain everything with quantum theory, but try starting here: http://theunrealuniverse.com/phys.shtml

The “Journal Article” link at the bottom touches on some of the points that we discussed elsewhere. It goes slightly off-topic, but you might also find the “Philosophy” link at the top left interesting.

Posted by: patopreto on 15/07/06 at 06:17 PM

Regarding that web site wian.One does not need to ead past this sentence –

The theories of physics are a description of reality. Reality is created out of the readings from our senses. Knowing that our senses all work using light as an intermediary, is it a surprise that the speed of light is of fundamental importance in our reality?

to realise that tis web site is complete ignorant hokum. I stopped at that point.

16 July, 2006

Posted by: whats-in-a-name on 16/07/06 at 09:04 AM

I’ve just been back to read that bit more carefully. I don’t know why the writer phrased it like that but surely what he meant was:(i) “Our perception of what is real is created out of the readings from our senses.” I think that most physicists wouldn’t argue with that would they? At the quantum level reality as we understand it doesn’t exist; you can only say that particles have more of a tendency to exist in one place or state than another.(ii) The information that we pick up from optical or radio telescopes, gamma-ray detectors and the like, shows the state of distant objects as they were in the past, owing to the transit time of the radiation. Delving deeper into space therefore enables us to look further back into the history of the universe.It’s an unusual way to express the point, I agree, but it doesn’t devalue the other information on there. In particular there are links to other papers that go into rather more detail, but I wanted to start with something that offered a more general view.

I get the impression that your study of physics is rather more advanced than mine- as I’ve said previously I’m only an amateur, though I’ve probably taken my interest a bit further than most. I’m happy to be corrected if any of my reasoning is flawed, though what I’ve said so far s quite basic stuff.

The ideas that I’m trying to express in response to Keka’s challenge are my own and again, I’m quite prepared to have you or anyone else knock them down. I’m still formulating my thoughts and I wanted to start by considering the model that physicists use of the nature of matter, going down to the grainy structure of spacetime at the Plank distance and quantum uncertainty.

I’ll have to come back to this in a day or two, but meanwhile if you or anyone else wants to offer an opposing view, please do.

Posted by: patopreto on 16/07/06 at 10:52 AM

I don’t know why the writer phrased it like that but surely what he meant was:

I think the write is quit clear! WIAN – you have re-written what he says to mean something different.

The writer is quite clear – “Once we accept that space and time are a part of the cognitive model created by the brain, and that special relativity applies to the cognitive model, we can ponder over the physical causes behind the model, the absolute reality itself.”

Blah Blah Blah!

The writer, Manoj Thulasidas, is an employee of OCBC bank in Singapore and self-described “amateur philosopher”. What is he writes appears to be nothing more than a religiously influenced solipsistic philosophy. Solipsism is interesting as a philosophical standpoint but quickly falls apart. If Manoj can start his arguments from such shaky grounds without explanation, then I really have no other course to take than to accept his descriptions of himself as “amateur”.

Maybe back to MEQUACK!