Posted by Febdian Rusydi in According to Relativistic Theory, space and time adjust themself to make speed of light (c) constant. Space can contract and time can dilate, these make c invariant in any circumstance. I have written a brief story about this.
Now, there is one interesting question: how does it happen? (I’m not asking why, but how :-)). Well, there is a particular answer that I got from book of The Elegant Universe”. I think Brian really get into Einstein’s mind how Einstein thought about it first time.
Feynman used the same method in his famous *The Feynman Lectures on Physics* (Chapter I-15-6).
Here is the answer.
This is a mind-experiment. Imagine we have a photon-clock that is shown in Fig. 1. Our photon-clock works this way: One single photon is trapped between two mirrors (these mirrors do have 100% reflaction index). The photon moves back and foward, and our special counter can tick everytime the photon hits the mirror. We define one periodic journey as a motion of photon to go and be back to its origin position after hitting both mirrors.
Figure 1. Our imaginary photon-clock. Don’t think it is in reality, it would be a super huge-impratic clock. We calculate that if d = 30 meters, then we will read 107 on our counter to have 1 second. (click the figure to zoom in)
To be precisely, let’s calculate how far the distance of these two mirrors we must make. The speed of light is 3×108 m/sec, which means: light travels 3×108 meters within one second - and it is invariant in any circumstance. If we make d = 30 meters (don’t imagine in reality, it would be a super huge-impratical clock), it means in one second we will hear ticks 107 times. Confuse? See the simple calculation in Fig. 1.
Fig. 1 tells us: if we get 5×107 ticks on our counter, we just have 5 second passed. This is how we calibrate our photon-clock.
Now, we make another photon-clock, exactly like what we have one before. One photon-clock stands still on the Earth, and the other moves with certain speed in x-direction. What is going to happen?
Figure 2. One photon-clock is moving in certain speed, and the other standing still on the Earth. (click the figure to zoom in)
Photon in the rest photon-clock travels d = 30 meters to make one click, and 60 meters to complete one periodic journey. But, photon in the moving photon-clock not travel d = 30 meters anymore to make 1 tick, but must travel d’, which is obviously longer than d.
If you wonder why photon can move like that, you can easily prove: when you are in the moving train, drop your bag and you will see the bag will fall exactly in the straight line toward the floor. But people on the ground (outside the train), if they can see you dropping your bag, will see the path is diagonal. You in the train are said in the comoving frame (or inside the moving photon-clock in our case), and people on the ground is said in the rest frame (or inside the rest photon-clock.)
What is the consequence?
When photon in the rest photon-clock have made 107 ticks, the moving one is still strugling to reach its 107 ticks. When the moving one reaches 107 ticks, the rest one is already start its second 107 ticks.
You can cross-check this statement by using simple phytagoras theorm. The faster you make v, the longer d’, which means the photon needs more time to reach 107 ticks.
In simple words: Our rest photon-clock see its moving brother is always late to count 1 second. Time dilates when we are in the co-moving frame!. Yes, moving clock goes more slowly than the one at rest.
It is interesting to find out how long the moving photon-clock late, which it turns out we will meet the famous constant relativistic 
. This thing I will postpond to discuss, I have to begin my own program… for completing my thesis, hee hee hee 
Saya mau bertanya nih, apakah waktu itu bersifat materialkistik yang emnyebabkanb eksisnya ruang atau bersifat psikologis? Teori lama selalu merujuk kepada konsepsi alam semsta sebagai kkontinuum raung-waktu. Pada keanytaaannya waktu juga bersifat sangat psikologis, bahkan muncgkin snagta psikologis sehingga konsep semesta sebagai kontinuuum-ruang waktu sebenarnya tidak lengkap yang bernar adalah kontinuum kesadaran-ruang-waktu.
Pak Atmonadi,
Saya kurang paham dengan “sifat materialistik” dan “sifat psikologis”nya tersebut. Mohon pencerahan, biar saya tidak salah menjawab
Ruang-waktu yang dianggap kontiniu (berkelanjutan) dalam alam semesta? Kalau kita memakai teori Dentuman Besar (Big Bang), maka jawabannya adalah tidak: karena pada teori BigBang ada titik singular, yaitu saat Big Bang itu terjadi.
[...] « Onion and Crying How Space Contracts We undersand now how time dilates due to motion with (closing to) speed of lig [...]
How Space Contracts
We talk about time dilates already. Now let’s see how space contracts in order to make speed of light constant.
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[...] And the same thing happens to ct. Now, we have to be careful here. You probably remember the time dilatation and the space contraction. I always get conflic this idea of p [...]
Dear Febian,
I start to think about building a photon clock to measure true universal time, it a hobby.
The heart of the clock is a very special shaped glass prism made of very special material sup 311 fuse silica IR as well as UV transmitting. My reasoning for this, is different color light or wavelenghts of light travels at different speeds. To make a truly accurate clock you would have to use a minimum of 4 different wavelenghts and average them.
The clock would have to be in an enclosed looping systems with detectors, last it would only work in deep space away from an gravity.
This would give you some type of true universal time, then you could run all your time tests against this clock and have a standard to work with.
Not having a standard anywhere in the universe make it had to compare.
mungkin yang dimaksud pak Atmonadi dengan psikologi begini bang buyung : waktu akan terasa lebih cepat kalo kita sedang dikejar deadline, lagi seneng dan seterusnya, sebaliknya akan menjadi lebih lambat kalo lagi susah, lagi nungguin seseorang.
saya mau nanya nih tentang lubang hitam. kok suatu bintang yang telah mengerut sampai volume yang sangat kecil “tak hingga” -kalo ngga salah- baru bisa jadi lubang hitam?? bukannya kuantitas massa bintang itu sendiri sama -atau bahkan lebih kecil setelah meledak sebegai supernova karena massanya terlempar keluar- ?? teman saya menjawab,”khan jari2nya mengecil?karena gaya berbanding terbalik dg kuadrat jarak sesuai dg hukum gravitasi universal Newton,maka gayanya membesar…” bukankah ketika kita berada pada jarak yang sama dengan pusat lubang hitam dan pusat bintang itu gayanya tetap sama?? dan pertanyaan yang mendasar: sebetulnya lubang hitam itu sendiri apa? oya sama singularitas dan horizon peristiwa itu apa?? mohon dijawab sejelas2nya… pake rumus tingkat tinggi pun tak apa..saya ga fobia rumus kok ^ ^ MAKASIIIIHH BANYAAAK
Febdian bisa gak nemuin sesuatu rumus atau penemuan baru yang kira-kira bisa mengharumkan nama bangsa di dunia internasional?Kalau menurut Febdian orang yang lebih pinter itu orang matematikawan atau fisikawan(di jawabanya jangan ada kalimat”orang fisikawan itu orang matematikawan juga)?
Maksud materialistik itu begiti. Kapankah kita sadar bahwa Waktu itu eksis ? Lantas kita mengatakan o, ini sehari lamanya 24 jam. Jadi, munculnya kesadaran atas waktu sebenarnya berbarengan ketika materi tumpah dari White Hole, dan waktu akan berakhir di Black Hole. Ketika dari white hole tupah, waktu Plack menunjukkan waktu terkecil yang bisa dimungkinkan untuk dijadikan rujukan bahwa begitulah alam semesta dimulai dari anti matri menjadi materi. Jadi, kematerialistikan muncul secara berbarengan. Namun, keterukurannya sebagai suatu unit dengan satuan tertentu misalnya m, km, detik, jam etc itu muncul seiring dengan kesadaran kita sebagai makhluk berpikir. Jadi, semua bentuk yang kita lihat atas bantuan cahaya sejatinya bersifat psikologis yaitu saat kita mulai mengenal sistem ilmu pengetahuan dasar. Kalau Anda telaah gagasan Phytagorean yaitu akar 2 dan akar 3 akan terlihat bahwa sumber ilmu pengetahuan kita sejatinya berasal dari konsep dasar kita ketika mendefiniskan simbol, geometri, bilangan dan huruf-huruf. Lantas kita membuat model matematis-fisika sebagai suatu cara memodelkan cara kita berpikir dan memaknai.