What is twins paradox

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, Wondrium. According to this theory, Gabby experiences acceleration to catch up the speed, decelerates to turn around, and then again decelerates to land on Earth. So, if acceleration is the answer, it means that while the spaceship is freewheeling between the stars, both twins age equally and when the acceleration turns on, there is instant aging.

However, there is only one problem, this theory is incorrect. So, to resolve this, we shall presume that there are three observers: Abby, Gabby, and Tabby. As previously assumed, Abby is stationary on earth and Gabby is heading at a speed of Tabby, heading toward Earth at the same speed as Gabby, is 24 light years away and along the line of sight between the two stars.

It is further assumed that the information on acceleration is not available and insignificant. This is because the total travel time is 24 years, so half the time to reach the star would be 12 years. Gamma is Now the third person, Tabby heading toward Earth, arrives at Tau Ceti exactly the same time Gabby arrives.

As Tabby heads toward Earth, she clears her clock and calculates the time duration to reach Earth from Tau Ceti. Spacetime diagrams One of the most illuminating ways of understanding the resolution of the so-called "twin paradox" is by analyzing carefully drawn, detailed spacetime diagrams for specific choices of trip distance and velocity.

The approximation of negligible turnaround time may very well lead to anatomically unrealistic "g forces"! In this case the Earth-bound twin EBT finds that it takes the traveling twin TT five years to reach the destination and five years to return for a total of ten years. The view from the reference frame of the Earth The left panel of the figure below which you can click on to open a larger version in a new window , shows the worldlines of the EBT and the TT in the reference frame of Earth.

Note that the TT reaches the destination at a distance of three lightyears after an elapsed time of five years in this frame and that the TT has aged only four years at that point. Note also that the scale of the x and t axes are such that light travels along lines at a 45 degree angle, i. Because the figure is drawn from the frame of reference of Earth, horizontal lines represent collections of events that occur at the same time, i.

The figure also, however, includes a few lines of simultaneity in the reference frame of the TT as shown in gray. Because of the relativity of simultaneity, these lines are tilted and run from lower left to upper right during the outbound leg and from lower right to upper left during the inbound leg.

For instance, note that one of these lines indicates that at the moment the TT sends the third yearly signal, the TT would say that the EBT's clock reads 2. Note finally that there are two lines of simultaneity linking the turnaround point, one for the outbound leg and one for the inbound leg. In order to return, it is crucial that the travelling twin either come to a stop and accelerate towards Earth or, alternatively, fire her engine to force her spaceship onto a tight curve to point it back towards Earth.

In both cases, the travelling twin feels the acceleration — decelerating, her body feels a pull in the direction of flight, re-accelerating, she is pressed into her seat, in flying a turn, she is pulled sideways. And in contrast with the twin on Earth, there is no slight redefinition that will do away with these acceleration phases.

Thus the apparent paradox is resolved. The twins are not on an equal footing. The accelerated twin cannot just apply the simple time dilation formula, while her sibling on Earth can. So what role does the acceleration play in this? Find out more in the spotlight topic Twins on the road.

The basics of special relativity — the proper theory to answer all questions about these twins — can be found in Elementary Einstein in the section Special Relativity. He initiated Einstein Online. Einstein Online is a web portal with comprehensible information on Einstein's theories of relativity and their most exciting applications from the smallest particles to cosmology. Includes information on our authors and contributing Institutions , and a brief history of the website.

More than entries from "absolute zero" to "XMM Newton" - whenever you see this type of link on an Einstein Online page, it'll take you to an entry in our relativistic dictionary. Langevin's explanation was expanded upon by Max von Laue. Laue went on to show that the world lines of inertially moving bodies increase the proper time elapsed between two cases, using Hermann Minkowski's space-time formalism. He also said that the asymmetric ageing is fully explained by the fact that the astronaut twin flies in two different frames while the Earth twin stays in one, and that the period of acceleration can be rendered arbitrarily small in comparison to the time of inertial motion.

By introducing the three-brother technique, Lord Halsbury and others were able to eliminate any acceleration. The travelling twin moves his clock reading to a third, which is moving in the opposite direction. The use of the relativistic Doppler effect is another way to avoid acceleration effects. Such findings were not found troublesome by Einstein or Langevin.

Langevin viewed it as a product of absolute acceleration, while Einstein just called it peculiar. Both men said that no self-contradiction could be derived from the time difference depicted in the tale of the twins.

In other words, neither Einstein nor Langevin saw the tale of the twins as posing a threat to relativistic physic self-consistency. Here to analyse the twin paradox solution consider the example of identical twins Jane and Joe explained earlier. To better understand this problem, consider making clear the observations of each other's clocks.

For example, the ticks of a clock may be transmitted from one twin to the other through electromagnetic radiation EMR. In theory, both of them could look at the other's clock through a telescope.

To make the diagram easier to understand, the clocks only tick once a year, and each twin sends the other a greeting message on their separation anniversary. Let's make graphs of position vs. Space-time diagrams are what they're called. There are three space-time diagrams in this problem, one for each of the three separate inertial reference frames involved.

Joe's diagram has one plot whereas Jane's diagrams have two plots, with the return journey diagram drawn above the outward journey diagram. In Joe's frame, the gap is 2. As a result, Joe estimates that the journey will take 2.