I heard the word "Gravity" for the first time while watching an episode of "Garfield and friends" called the Grabbity. (Yes I used to watch the old cartoons TVM recycled over and over again for years almost every evening).
Later in primary school I learned that gravity is some sort of force of attraction between objects that has mass. And today, I am wondering what causes Gravity?
gravitons? its still a mystery kanneyge.. i think they're working on it. let's see..
ReplyDeleteIf there is indeed such a particle as the Graviton, what causes the emission of it?
ReplyDeleteLike you said Anon (9:47) lets wait and see :D
i just know that its the pull by the earth..or pull by any other planet..the cause dho..
ReplyDeletethat's a question ur not supposed to ask :P
why not shweeetu? :P
ReplyDeletemaybe bcoz Imitally once said 'ibrahim maa gina suvaalu nukurey. rasgefaanaai kalaangethah hedhdhevvy emeehun amilla ah'
ReplyDeletebut as armande from chocolat said 'don't worry so much about not supposed to'
gravitons are quantum theory's answer to the gravity question like general relativity has spacetime curvature. all this because mass as a cause for gravity is plain unsatisfactory. (too bad for shweet and Newton)
ofcourse there's the easy answer: Allahu 'aulam. which is the least satisfactory. so.. i repeat.. we just have to wait for the brainier ones to figure it out.
I totally do agree with you anon, am keeping hush hush till than.
ReplyDeleteMaybe I can add a bit on, heard of the string theory? It suggests that the Gravitons are the only open ended particles, making it extremely hard to capture in experiments.
ReplyDeleteThan again the we still don't know why this cause gravity
Anon (9:47): Is there any phenomena cleared of all mystery? Would appreciate even one example.
ReplyDeleteAnon (2:05): Are you suggesting that with enough brains that you could clear all natural phenomena of all mystery? In case this question is unclear let me clarify. Suppose mystery A1 causes A0; A brainier person comes along says A2 and A3 causes A1. But now A2 and A3 are mysteries. Are you suggesting that this cycle could in principle be broken without at some point allowing a non-axiomatic "explanation"? If so could you say how exactly this would come about, even in principle?
Could you clarify on your statement "gravitons are quantum theory's answer to the gravity question like general relativity has spacetime curvature." Could we talk in more concrete terms.
"all this because mass as a cause for gravity is plain unsatisfactory." I do agree with this to a good extent. But shall we elaborate on exactly how it is unsatisfactory? I am sure many readers would appreciate it. It may not be so obvious to many readers.
Btw, why is that you guys bounce at every opportunity to mock at people of faith? Are you suggesting you are a people of inductive reasoning alone?
Vanilla, personally its saddening for me to see people using science to mock people of faith
ReplyDeletedid i ever mock religion? i'll have you know that i'm very devout.
ReplyDelete^anony (11:32) I was talking in general
ReplyDeletesorry fish. i was talking to vanilla.
ReplyDeleteas for his/her Qs:
Q. do we know everything?
A. no
Q. can we know everything?
A. no
Q. clarify/elaborate this/that
A. read a book.
Q. why do u mock religion?
A. i was mocking dogmatism.
anon (1:08): I have read many books, attended formal lectures and passed courses in both quantum theory and relativity.
ReplyDeleteother readers of this blog: since a clarification seem not to be forthcoming, I will make an attempt, dogmatism aside. In pre-relativity and pre-quantum times, fundamental forces such as electromagnetic and gravitational force were understood in an "action at a distance" paradigm. In this paradigm, if several charges such as electrons and protons were separated in space, one was simply supposed to exert a push on another without any mediator. So if we were to wiggle one of the charges, others would wiggle correspondingly and instantly no matter how far apart they are. Now this is philosophically unsatisfactory, for how does one charge know about the existence of the other? This is also scientifically unsatisfactory, for now we do know that its take a finite time for far away charges to start wiggling. In fact the delay is exactly that which would occur if information about the wiggling were transmitted with the speed of light (which is a constant). This delay was successfully explained for charges in the special theory of relativity as the time taken for photon go from one to another; and for gravitation as a speed of propagation of perturbations in space-time curvature. When the quantum theory and special theory were finally wed, it popped out as a direct consequence that "anti-matter" should exist. This set the stage for understanding all known forces as an exchange of particles. To get a feel for this, imagine you throw a ball to a friend. When you throw the ball out you would feel a recoil force, and when your friend catches the ball, he/she too would feel a force. Thus the ball is the mediator of a force between the two of you. In like manner electromagnetism is now known to be mediated by photons. In fact, relativity dictates that forces with infinite range must be mediated by mass-less particles. Now, at present we do not have a quantum theory of gravity, yet most scientists have faith that relativity and gravity would be eventually wed and it is hypothesized that a mass-less particle, dubbed the "graviton" acts as the force mediator for gravity. Thus far no one has detected a graviton and it remains a theoretical entity. There have been several attempts to unify gravity and quantum theory. One of the most promising paradigms is popularly know as string theory. But it should be warned that this is far from a scientific theory at the moment, even if its a very promising one.
Vanilla what does it mean when they say "Open ended particle"?
ReplyDeleteFish, it is extremely difficult to talk about string theory without getting all abstract and mathematical. I am not sure how successful I will be in describing this, but here goes.
ReplyDeleteStrings are mathematical objects. A coordinate in the familiar 3-dimensional space may be written as: (x,y,z). You could write this as X^i with i = 1,2,3. (I actually wanted to write X superscript i, and not a power, and the index i counts the dimensions). In such a space, we could describe a one dimensional object by fixing 2 of the indices and varying the other. More generally, you may recall from A level that a vector equation of a line has a single parameter that varies.
In relativity theory we have whats called space-time, which has four components (x, y, z, ct). In the last component c = speed of light in free space and t = time (think of c as converting seconds to meters), and thus we have 4-dimensional space-time. The first 3 coordinates are space coordinates and the last, the time coordinate. A particle's (in the normal conventional way you are used to think of a particle – a zero dimensional object) history may be represented in a graph. That is you plot its successive space-time coordinates. To imagine this just assume one space coordinate, so you are drawing space along one Cartesian axis and ct on the the other Cartesian axis. The successive coordinates of the particle (i.e its history) will appear on such a space-time graph as a line. It may not be a straight line, but never the less a line. We call such a line a world-line.
Now imagine generalising this idea to include more dimensions. Its hopeless to visualise so many dimensions. But you could write it in mathematical symbols, just like we did before, X^i with i = 1, 2, ... , N. Thats a coordinate in an N-dimensional space. A string, is a one dimensional object in this N dimensional space (in m-theory, N = 11, but lets not put in numbers to confuse things). Just like one parameter was needed to describe the line (a one dimensional object) in ordinary 3-dimensional space, we could parametrise this one dimensional object in N dimensional by a single parameter. Lets call this parameter s. Now we could write the trajectory of this string as X^i (s,t), where t is time. Now, if you plot the history of such a string in a space-time diagram we would get a word-surface instead of the world-line (which we got for the 0-dimensional particle).
If the string was in the shape of, say a rubber band, with no end, then we called this a closed string, and its world-surface would be sort of a tube. On the other had if the string was like a rubber band that has been cut, its world-surface would be a sheet, say like the ocean surface, or a drum-skin surface. Such a string is said to be open (which I believe is what you are referring to as open-ended). Now, in this kind of set up, a particle is thought of as an 'excitation mode' on strings. The popular analogy to get a feel for such excitation modes is the vibrations on a guitar strings. Perhaps we could also think of excitation modes on a drum-skin. I am a novice to string theory, but I believe that what you mean by an open-ended “particle”, are excitation modes on open strings.
There are other interesting things to consider. For example, how would you determine the dynamics of a string. It will turn out that a “least action” type of formulation is suitable; and then there is the question of boundary conditions (i.e. end point conditions) for such open strings. It will also come about that under special kind of boundary conditions (called Dirichilet boundary conditions) the ends points are fixed on a hypersurface (i.e. surfaces in multi-dimensional space) for all times. Such surfaces are called p-branes. The list of interesting things goes on. But one needs to be mathematically sophisticated to fully grasp these ideas. I have been told by people in the know that many of the popular analogies used to popularise string theory are flawed. So please be wary of analogies.