cuba daus bacer...daus tentu faham kot i tatau
mbhcsf Post at 16-11-2010 21:04
‘Space-time cloak’ to conceal events revealed in new study
Scientists have developed a recipe for manipulating the speed of light as it passes over an object, making it theoretically possible to ‘cloak‘ the object’s movement so that an observer doesn’t notice, according to a paper in the Journal of Optics.
The study, by researchers from Imperial College London, involves a new class of materials called metamaterials, which can be artificially engineered to distort light or sound waves. With conventional materials, light typically travels along a straight line, but with metamaterials, scientists can exploit a wealth of additional flexibility to create undetectable blind spots. By deflecting certain parts of the electromagnetic spectrum, an image can be altered or made to look like it has disappeared.
Previously, a team led by Professor Sir John Pendry at Imperial College London showed that metamaterials could be used to make an optical invisibility cloak. Now, a team led by Professor Martin McCall has mathematically extended the idea of a cloak that conceals objects to one that conceals events.
“Light normally slows down as it enters a material, but it is theoretically possible to manipulate the light rays so that some parts speed up and others slow down,” says McCall, from the Department of Physics at Imperial College London. When light is ‘opened up’ in this way, rather than being curved in space, the leading half of the light speeds up and arrives before an event, whilst the trailing half is made to lag behind and arrives too late. The result is that for a brief period the event is not illuminated, and escapes detection. Once the concealed passage has been used, the cloak can then be ‘closed’ seamlessly.
Such a space-time cloak would open up a temporary corridor through which energy, information and matter could be manipulated or transported undetected. “If you had someone moving along the corridor, it would appear to a distant observer as if they had relocated instantaneously, creating the illusion of a Star-Trek transporter,” says McCall. “So, theoretically, this person might be able to do something and you wouldn’t notice!”
The research could have applications in computing and signal processing
While using the spacetime cloak to make people move undetected is still science fiction, there are many serious applications for the new research, which was funded by the Engineering and Physical Sciences Research Council (EPSRC) and the Leverhulme Trust. Co-author Dr Paul Kinsler developed a proof of concept design using customised optical fibres, which would enable researchers to use the event cloak in signal processing and computing. A given data channel could for example be interrupted to perform a priority calculation on a parallel channel during the cloak operation. Afterwards, it would appear to external parts of the circuit as though the original channel had processed information continuously, so as to achieve ‘interrupt-without-interrupt’.
Alberto Favaro, who also worked on the project, explains: “Imagine computer data moving down a channel to be like a highway full of cars. You want to have a pedestrian crossing without interrupting the traffic, so you slow down the cars that haven’t reached the crossing, while the cars that are at or beyond the crossing get sped up, which creates a gap in the middle for the pedestrian to cross. Meanwhile an observer down the road would only see a steady stream of traffic.” One issue that cropped up during their calculations was to speed up the transmitted data without violating the laws of relativity. Favaro solved this by devising a clever material whose properties varied in both space and time, allowing the cloak to be formed.
“We’re sure that there are many other possibilities opened up by our introduction of the concept of the spacetime cloak,’ says McCall, “but as it’s still theoretical at this stage we still need to work out the concrete details for our proposed applications.”
Metamaterials is an expanding field of science, with a vast array of potential uses, spanning defence, security, medicine, data transfer and computing. Many ordinary household devices that work using electromagnetic fields could be made more cheaply or to work at higher speeds. Metamaterials could also be used to control other types of waves as well as light, such as sound or water waves, opening up potential applications for protecting coastal or offshore installations, or even engineering buildings to withstand earthquake waves.
saya dh baca....
analoginya spt device yg digunakan tuk transport objek tanpa dikesan ngan mata ke satu tmpt lain...
dlm star-trek ada guna kaedah ni...haha
kat dlm artikel ada tulis spesifik eksperimen
tuk detect bhgn spektrum elektromagnetik yg boleh hasilkn imej yg tdk dpt dilihat dengan mata...
pada masa ni, objek yg dipindahkan tidak dpt dilihat ngan mata..& sekelip mata dh smpi ke destinasinya
sainstis pggl event ni sbg "clock"
again...
rmi argue halaju objek tidak boleh melebihi speed of light
sbb tiada teori "provable yet concise" untuk membuktikan objek boleh travel lebih dari speed of light
kita masih dihadkan ngan teori relativiti
Alberto Favaro, who also worked on the project, explains: “Imagine computer data moving down a channel to be like a highway full of cars. You want to have a pedestrian crossing without interrupting the traffic, so you slow down the cars that haven’t reached the crossing, while the cars that are at or beyond the crossing get sped up, which creates a gap in the middle for the pedestrian to cross. Meanwhile an observer down the road would only see a steady stream of traffic.” One issue that cropped up during their calculations was to speed up the transmitted data without violating the laws of relativity. Favaro solved this by devising a clever material whose properties varied in both space and time, allowing the cloak to be formed.
soalan saya sebab saya obviously mg tak faham
a) kalau ia tidak mematuhi or violating the law of relativity - apa kan jadi
b) kenapa ia menjadi satu masalah pulak bagi this team of researchers?
c) metamaterials ni apa
d) ni kire maca stealth f-15 bomber tu ke? yang boleh disguise undetectable by radar tapi in this context dia cloak/ dia jubahkan/ samarkan disguise kan diri ....dengan manipulate temph masa ? speed
a) rmi argue halaju objek tidak boleh melebihi speed of light
sbb tiada teori "provable yet concise" untuk membuktikan objek boleh travel lebih dari speed of light
kita masih dihadkan ngan teori relativiti...kita tiada TEORI ASAS YG KUAT untuk buktikan objek boleh travel fast than speed of light, sbb tu saintis dimaksudkn buat eksperimen tanpa violate speed of light
b) rujuk (a)
c) ni saya tak tau..sbb saya tak amik fizik bahan, mgkn pnnt klu smbg phd, boleh kot jwbb persoalan mbhscf
d) again...konsep penyamaran diri tanpa dikesan oleh orang dalam tempoh masa yang sgt sekejap tidak pernah lagik dibuat org...
cth: bayangkan anda dalm bilik gelap, slps sahaja anda buka lampu, anda boleh pandang sesuatu objek dengan cepat sbb cahaya bergerak ngan c (3.0 x 10^8 ms^-1) , tetapi adakah possible seseorg yg duduk di sebelah pada masa itu boleh lagik cepat ke kedudukan objek dr masa yg diambil tuk anda pandang objek tu sejurus sahaja lampu dibuka? analoginya begini..
thus it is not possible to violate speed of light unless there is provable theoritical experiment can prove someone can travel more than speed of light...kita tak de maklumat yg cukup tuk "ketahui" objek travel more than speed of light (even tiada lagik partikel yg bergerak lebih dr halaju cahaya di dunia secara semulajadi)..so macammana nak formulate konsep "space-time clock" klu tiada maklumat berikut?
oleh itu, kisah f-15 bomber hanyalah berdasarkan sebab lain, bukan kerana space-time clock
Dia tidak dpt dikesan radar mungkin kerana dia pakai baju pelindung gelombang (it can be sbb klu potential dlm baju tersebut melebihi energy dibawa gelombang tersebut, the wave is exponentially decay, wave eqn tak boleh jadi - rujuk QM explaination dlm thread MEKANIK KUANTUM & tanya kt situ ) , maka tiada gelombang yang akan dipantulkan kembali (kena make sure, it can absorb the wave rather than reflect)
but to travel from one distance to another distance in such short time with speed greater than c, it is IMPOSSIBLE right now...
Percanggahan mengenai usia kembar dari pandangan berbeza ( different frame/view)
Azri dan Amri ialah kembar berusia 15 tahun dan mereka ditugaskan untuk dijadikan bahan eksperimen mengkaji relativiti.
Azri ditugaskan untuk duduk di bumi manakala Amri dikehendaki menaiki pesawat roket untuk ke planet Serica yang berada pada jarak 18 tahun cahaya ( 1.14 x 10^14 km ) dari bumi dan pulang semula ke bumi (= 5.68 x 10^14 km ) selepas itu.
Amri menaiki pesawat yang mempunyai kelajuan sebanyak 0.97c ( =7.76x 10^7 m/s). Anggap pesawat Amri tidak memecut.
Selepas mendapat perkhabaran bahawa Amri bakal pulang semula ke bumi, Azri begitu gembira kerana dia menyangka dapat menyambut majlis hari jadi bersama-sama dengan Amri setelah sekian lama berpisah.
Umur Azri sewaktu ketibaan Amri ke bumi ialah
= usia Azri sebelum Amri berlepas dari bumi + masa diambil oleh Amri untuk membuat pusingan semula ke bumi
= 15 + 2 x Jarak antara bumi dan planet Serica / Masa diambil semasa perjalanan bumi ke Serica
= 15 + 2 x 18 / 0. 97
= 15 + 28.24 = 52.11 tahun
Azri telah berusia 52.11 tahun...
Azri: "Kembar aku akan pulang tak lama lagi, bolehlah kitaorg sama2 menyambut hari jadi". Azri tersenyum sipu.
Namun, sangkaan Azri meleset sebaik melihat Amri keluar dari pesawat...
Azri: "Amri, sudah lame kita tak berjumpa..rindu sangat" Azri: " Eh, kenapa kau nampk muda?..Gigi aku dh nak tercabut weii...dah kertu, kau pulak nampak hensem masa aku muda dulu" Amri: "Bukan kita sama umur kah? Patutnya usia kau sama ngan aku....Umur aku akan masuk 22 tahun dua bulan lagi"
Amri: "haha..padan muka kau dah tua" Azri: "Wth? macammana nak sambut hari jadi malam ni kalau umur dah tak sama? " Amri: "Tetapi aku pelik, padahal aku meneruskan perjalanan sebanyak 7 tahun sahaja... kenapa bila aku sampai ke bumi, kau pulak lagi tua dari aku??" Azri: "Sebab itulah aku hairan..sepatutnya umur kau dah masuk 52 tahun, anak sulung aku pun lagi tua setahun dari kau"
Oh gosh! Pendapat mereka mengenai umur masing-masing bercanggah.
Mengapakah perkara ini berlaku?
Anda boleh tumpukan 2 frame - pandangan Azri di bumi terhadap Amri & pandangan Amri di dalam pesawat terhadap Amri
1. Pandangan Azri di bumi
Sekarang kita fokus kepada pandangan Azri terhadap gerakan Amri.
Maknanya di sini, bayangkan anda melihat orang bergerak meninggalkan anda dan kembali semula menemui anda..
Rujuk di sini untuk penerangan -->
"Two spaceships are traveling together through the galaxy at close to the speed of light. Mounted on one ship is a laser that can fire pulses of light, and on the other, a mirror. The pilot of the first ship fires a pulse at the mirror, and watches as it is reflected back. A clock on board measures how long the round trip takes.
But now suppose that he does this as the ships are passing an observer on a nearby asteroid. According to relativity theory, this observer sees the pulse moving through space at exactly the same speed that the pilot does -- namely, the speed of light. But he also sees the pulse traveling a longer distance, because from his perspective, he must add the forward motion of the ships to the motion of the pulse between them. So he measures a longer time interval for the round trip than the pilot does, because he is watching the pulse go farther without going any faster. This effect is called time dilation: if one observer is moving with respect to another, each perceives that the other's time is flowing more slowly."
Konkusi utube: Kapal bergerak dengan halaju menghampiri halaju cahaya. Anda di asteriod melihat gerakan tersebut dan mendapati masa diambil oleh kapal bergerak dari A --> B adalah lebih lambat berbanding masa yang dikira oleh orang yang berada dalam kapal. Ini kerana masanya telah dipanjangkan oleh cahaya yang dilihat anda di A yang bergerak ke arah anda dan terus bergerak ke B.
Masa dikira oleh orang berada di asteroid
= Masa dikira oleh orang yg berada di dlm kapal x atau secara ringkasnya
Oleh itu, merujuk kepada masalah umur Amri dan Azri,
Usia Amri adalah
= usia Amri sebelum Amri berlepas dari bumi + Berapa banyak tahun ditempuhi Azri selepas Amri tiba di bumi x Sqrt ( 1- v^2/c^2)
= 15 + 28.24 x Sqrt (1- 0.97^2)
= 21.86 tahun!
-KESIMPULAN-
"Twin Paradox" menunjukkan bagaimana masa berubah kerana jisim dan halaju. Makin laju seseorag tu bergerak, atau makin besar jisimnya, maka masa diambil untuk merentasi ruang adalah lebih lama (lambat). Kembar A duduk di bumi. Kembar B menaiki pesawat keluar dari bumi dengan halaju menghampiri halaju cahaya, maka bila dia kembali, dia mendapati dia lebih muda beberapa tahun dari kembar A.
Percanggahan mengenai usia kembar dari pandangan berbeza ( different f ...
dauswq Post at 21-5-2011 05:22 PM
daus, just nak tanya. How do we know what we know ? sebab ianya belum terbukti secara praktikal lagi., hanya teori. thehehe. betul betul boleh percaya ke ?
"twin paradox" ni mmg teori
tp realitiviti mmg wujud...
sbb jgn lupa
kita kena pertimbangkan partikel yg kecil spt electron, neutrino, muon dan sbgnya yg bergerak dengan halaju menghampiri halaju cahaya...dari sini, relativiti applied..
contohnya,
dalam bidang nuklear physics,
apabila satu atom bertempur ngan atom lain,
ia akn menghasilkan neutrino yg bergerak ngan halaju cahaya...
so nak kira tenaga yg terhasil, E=mc^2
Einstein buat formula ini dari konsep realitiviti dan smpi skerang manusia sejagat menggunakan persamaan ini untuk mendapatkan
tenaga terhasil dari nuklear...
satu lagi aku bagi contoh,
kau naik kereta duduk di seat kiri sebelah pemandu..
bila kereta bergerak, pastu kau baling bola ke atas...
apa yg jadi kepada bola? kenapa kau nampak bola tak terpelanting ke depan mengikut arah halaju kereta..tetapi bola hanya "stay" pada kedudukan mencacangnya sahaja?
Newton bagitahu sbb inertia...
Namun, cuba pemerhati di luar kereta melihat kau berbuat demikian..dia akan nampak bola bergerak ke depan
berdasarkn relativiti pula, ini disebabkan perubahan cahaya yang masuk ke dalam mata dan patah balik ke bola menyebabkan pemerhati nampak bola spt bergerak depan...dan dari situ jugaklah, relativiti itu wujud...
"twin paradox" ni adalah satu konsep terhasil berdasarkan pemerhatian relativiti..of coz tiada lagi experimen dibuat
(kau nak ker anto anak kau pi luar angkasa, pastu kau tunggu die balik 15 tahun kemudian..tgk2 beza umurnya tak banyak)
New theories emerge to disprove OPERA faster-than-light neutrinos claim
(PhysOrg.com) -- It's been just two weeks since the Oscillation Project with Emulsion-tRacking Apparatus (OPERA) team released its announcement claiming that they have been measuring muon neutrinos moving faster than the speed of light, causing an uproar in the physics community. Since that time, many papers (perhaps as many as 30 to the preprint server arXiv alone) have been published seeking ways to discredit the findings. Thus far though, only two seem credible.
The first is by Carlo Contaldi of Imperial College London. He says that it’s likely the OPERA team failed to take gravity into their math equations and its effect on the clocks used to time the experiment.
This because the degree of gravity at the two stations involved in the experiment (Gran Sasso National Laboratory in Italy and the CERN facility in Geneva) were different, thus one of the clocks would have been running slightly faster than the other, resulting in faulty timing. If this turns out to be the case, the OPERA team will most certainly be embarrassed to have overlooked such a basic problem with their study.
The second is by Andrew Cohen and Sheldon Glashow, who together point out that if the neutrinos in the study were in fact traveling as fast as claimed, they should have been radiating particles as they went, leaving behind a measurable trail; this due to the energy transfer that would occur between particles moving at different speeds. And since the OPERA team didn’t observe any such trail (or at least didn’t report it) it follows that the neutrinos weren’t in fact traveling as fast as were claimed and the resultant speed measurements would have to be attributed to something else.
Neither of these papers actually disproves the results found by the OPERA team of course, the first merely suggests there may be a problem with the way the measurements were taken, the second takes more of a “it can’t be true because of…” approach which only highlight the general disbelief in the physics community regarding the very possibility of anything, much less the speed of neutrinos traveling faster than the speed of light, messing with Einstein’s most basic theories. The first can be addressed rather easily by the OPERA team if it so desires, and the second, well, if the neutrinos did in fact travel faster than the speed of light and did so without leaving a trail, a lot of physics theory will have to be rethought. Though that may not necessarily be a bad thing, physics is supposed to be about finding answers to explain the natural world around us after all, even if it means going back to the drawing board now and then. © 2011 PhysOrg.com
aritu bukan kemain sainstis2 ni klem neutrino boleh bergerak lebih laju dari halaju cahaya...hehe
Post time 16-11-2010 02:20 PM
Author
, kau pulak nampak hensem masa aku muda dulu"
Bukan kita sama umur kah? Patutnya usia kau sama ngan aku....Umur aku akan masuk 22 tahun dua bulan lagi" 
macammana nak sambut hari jadi malam ni kalau umur dah tak sama? 
"
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