about the twin Paradox;;;can anyone explain the relative symmetricity of events in space-time?

Question

I mean, when one brother(A) travells at near light speeds wrt the other(B);since there is no absolute frame of reference,from A's pt of veiw, B is movin at near light speeds..n vice verca... unless an absolute frame of reference is established, both of em shd experience the same effect. and the speed of light can't be considered as the absolute frame of reference as both would have similar time cones as the speed of light would be a constant wrt either of them.How can relativty itself break down at this pt?I dont mean to dis the concept, I just wanna kno the explanation...

when u speak abt acceleration, isn't tat wrt A again,so A n B both 'd feel the other is accelertin to near light speeds..so how can u say one experiences -ive accelaration wrt the other..Again there is only relative acceleration,so eiter can be accelerating unless a universal frame of reference is established..

Answer 1

Time slows down when you are moving that fast. It sounds stupid, but it does reconcile your issue here. I'd say more but I have to be up in 6 hrs. Peace out.

*edit* I might come back and elaborate unless someone beats me to it tomorrow.

Answer 2

Only one twin will feel the effects of acceleration (being pushed back into the seat, etc). This type of thing is best done with a spacetime diagram. The paths of both twins will be lines in spacetime, but one twin's path will not be straight. It is this twin that will age less. The paths are independent of how fast the twins move. The time each twin experiences is related to the length of the path (but a longer path gives a shorter time).

Another way to look at this is that the stay-at-home twin is always in a inertial reference frame. The one that has to turn around has to change reference frames at the turn-around point. That breaks the symmetry of the twins.

Answer 3

It all has to do with relative motion against the frame of reference of spacetime. Yes, both space and time individually are flexible, but spacetime is absolute. The one that goes away at near light speed then slows down to meet up with the one who stayed behind will be the one who had the relativistic effects--i.e. his rate of time will have passed slower than rate of the other. B underwent extreme changes in velocity due to his acceleration, A did not. A stayed relatively constant.
It is not just the concept of relative perspective. Yes, two observers moving away from each other with only each other as a frame of reference would say they are each stationary and the other is moving. But, in the case of the twins paradox, they both do not maintain constant rates of motion or velocity. The traveler undergoes more extreme velocity and acceleration changes compared to the waiting one. It takes chapters of books to fully explain it. A couple books I strongly suggest for your reading is in the source below.

Answer 4

The Principle of Relativity states that the mathematical forms of the laws of physics are identical in all frames of reference independent of their relative motion; i.e., all frames are equivalent in this restricted but important sense that the laws of physics are invariant from one frame to another, whether the frames are accelerating or not. In the twin problem, although the respective frames are equivalent in this sense, they are not dynamically symmetric since only the traveling twin experiences acceleration. However, if one assumes that the frames of the traveling and stay-at-home twin are dynamically symmetric and confuses dynamic symmetry with equivalence (and perhaps, additionally, falsely infers equivalence to mean identical calculations in all frames), one erroneously concludes the same result for each twin's time dilation as calculated by the other twin; i.e., one expects the traveler upon return, to have aged more and less than his twin – which is clearly impossible. In this connection, it is important to understand that relativity does not claim that all observers make identical measurements when observing the same phenomena; generally they do not. Nor does relativity claim that a time dilation calculation that each observer performs for his twin is a "law of physics" that must remain invariant from one observer or frame to another. However, these calculations would be expected to be identical for dynamically symmetric frames!It is to be noted, however, that time dilation has no relationship whatsoever to the amount, direction, or duration of acceleration.In the usual resolution of the twin paradox, it is only the bare fact of acceleration which is invoked, and not any measured quantity.

Answer 5

a nicely-time-honored question - the textual content textile-e book decrease than devotes 5 pages to discussing solutions! The considered necessary element however is that earth and the spacecraft did no longer circulate interior an identical way - the gap craft would desire to have experienced an acceleration with a view to instruct around and are available decrease back to earth; the earth did no longer advance up! Relativity asserts that there isn't any absolute degree of velocity - however an identical isn't genuine of acceleration.

Answer 6

You have in effect stated the twin paradox; special relativity treats each twin's viewpoint as equally valid. The paradox was used to discredit the theory. The reason the paradox exists is that the theory is limited in scope; it only applies to uniform relative motion (no acceleration). In the real world, one twin has to undergo acceleration in order to travel, the other does not. Therefore the situation is not truly symmetrical. General relativity, which includes the effect of acceleration, resolves the paradox.

Answer 7

You are absolutely correct: both twins should (and do!) percieve the other twin as acting slower. Note that as long as the twins keep moving apart, this is not a problem, since they have no direct way to compare their age, and can only observe each other is by looking at the light the other twin emits. Calculations done from either Earth's reference frame or that of the outbound twin show them both recieving the light rays after the same amount of proper time. The "paradox" occurs when you try to bring them back together: naive observers will think that the Earth is still moving in the ship's reference frame and the ship is still moving in the Earth's reference frame, and so they will both still percieve the other to be moving and thus when they are right next to each other, they will still both observe the other to be younger, which is absurd.

Fortunately, it is also fallacious, because the ship is not in the same reference frame throughout the entire journey. Rather, when it turns around, the ship moves from a reference frame moving away from Earth at some speed to a reference frame moving towards the Earth at some speed. These are two different reference frames, and as such calculations made in one (especially about when "now" is - more on that in a moment) don't apply to the other. Now if you stay in the same reference frame throughout the entire journey, you get one of three possibilities:

Earth frame: the ship moves outward, and comes back. The astronaut twin ages slower on both legs of the journey and is younger when he arrives.

Outbound frame: first the ship is stationery, and the Earth moves outward. The twin on earth ages slower, but the motion of Earth does not last as long, nor does the Earth move as far away from the ship (time dilation and lorentz contraction, respectively). The ship then accelerates to a speed higher than Earth's in an attempt to catch up with it. For the remainder of the journey, the astronaut ages even slower than his Earthbound twin. Further, because addition of velocities in SR is sublinear, it takes longer (in this reference frame: proper time for the ship is the same) to catch up to Earth, giving the earthbound twin time to age. Result: when the ship finally catches up to Earth, the astronaut twin is younger.

Inbound frame: The Earth starts out moving, and the ship moving faster. The twin in the ship ages slower than the twin on Earth, and the ship takes a long time to outrun Earth by the perscribed distance (again, sublinear addition of velocities), so by the time the astronaut reaches his destination, the earthbound twin has already celebrated his brother's (calculated) turnaround. Then the ship stops, and the Earth catches up to it. The Earthbound twin ages slower during this phase, giving the the astronaut a chance to "catch up" in age, but the astronaut twin is still younger when the Earth arrives.

You'll notice that while all three of these reference frames agree on how old the twins are when they are finally reunited, they don't agree on how old the twins are at other points in the journey. For instance, suppose that the trip is scheduled to ake 20 years of Earth time, and so the earthbound twin decides to celebrate his brother's turnaround at the 10-year mark. In the Earth's reference frame, this celebration occurs at the same time that his brother turns around. But in the outbound reference frame, when the ship turns around, the celebration hasn't occurred yet. Converesly, in the inbound reference frame, it happened several years prior to the ship's turnaround. Events that are simultaneous in one reference frame are NOT simultaneous in others, which is what physicists mean when they say simultanaeity is relative. This means that if you say two things happen at the same time, you have to clarify about which reference frame you're talking about, otherwise that declaration is meaningless. The twin "paradox" occurs primarily because people try to take the plane of simultanaeity from one reference frame (the outbound one) and then apply it to the inbound frame. In other words, they assume that if the astronaut's brother is x years old "now," just before the astronaut turns around, he will still be x years old "now," just after the astronaut turns around. But this is incorrect, because we have changed reference frames, and thus have changed when "now" is with respect to the ship. If we assume "now" must coincide with the same time from the astronaut's perspective, then "now" on earth is several years after "now" was in the outbound frame. And since the twin on Earth is "now" older, there is no paradox in his still being older when he finally gets to the ship.

Answer 8

The special relativity principle only says that speed is relative. Acceleration is not.

So if one brother rests while the other accelerates from zero to almost speed of light, and later accelerates back to almost minus the speed of light to return, there is a difference between the two brothers.

Answer 9

Good question, In my understanding it would come to the fact that even though to brother A it would appear as if Brother B was traveling at the speed of light it would not be the case thus the time cones would be dissimilar i.e. Brother A would be the one who would barely experience time while brother B would experience time at the normal rate.

Answer 10

Helene_thygese is right. The twins paradox isn't symmetrical. One twin accelerates, slows down, accelerates back home and slows down. The other doesn't. The accelerated twin ends up younger than the other.