Suppose, you live on a planet in orbit around Alpha Centaury which is approximately 4 light years away from our own Sun. You board a spaceship bound for Earth, and fire up the engines at the exact moment you observe the Earth to be located at the position of the Vernal Equinox. Your observation of the equinox does of course trail its occurrence by 4 years due to your distance from the actual event. Your spaceship accelerates almost instantly from zero to about 0.999 c. For the most part of the journey you travel at constant speed.(adsbygoogle = window.adsbygoogle || []).push({});

Now, here is the question: How many Vernal Equinoxes are you going to observe during your transit to Earth?

According to Special Relativity, you, the passenger of the spaceship, are at rest since the reference system of the ship is a valid inertial system as long as the ship moves at a steady rate. You see surrounding space, Sun and Alpha Centaury with it, move past your position at a constant speed of 0.999 c.

The solar system is in steady linear motion in respect to the ship's frame of reference hence you observe terrestrial clocks running slower then your own. One Earth-hour is dilated to 22 of your Ship-hours. Simultaneously, the distance between Sun and Alpha Centaury appears contracted to 1/22 of the initial distance measuring now a bit less then 0.2 light-years in the ship's reference frame.

If special relativity were correct, then according to the ship's clock the trip would last less then 0.2 years. Since for the ship-bound observer 22 ship-years correspond to one Earth-year, the passenger won't see the Earth move much past the position of the Vernal Equinox during the journey.

But what happened to the 4 Vernal Equinoxes which did already occur by the time the start signal, the information of the first equinox, reached the ship at Alpha Centaury? How can the ship miss the visual information of those events?

If, on the other hand, the passenger does indeed observe those four Vernal Equinoxes, then he does so within 0.2 ship-years. That would mean that he witnessed the passage of at least 4 Earth-years within 0.2 ship-years. This observation contradicts the time-dilation effect predicted by special relativity. Remember! In the reference frame of the ship the Earth is in motion and must therefore "Age" slower, not faster, then the ship.

An Earth-bound observer sees things slightly different. In his frame of reference, 4 Vernal Equinoxes occur while the ship is in transit, a total of 8 occurred since the one (Vernal Equinox) that served as the start signal. The ship arrives 0.004 years after the information of its departure from Alpha Centaury. The Earth-bound observer expects the passenger to count 8 Vernal Equinoxes during his 4 Earth-years in transit.

There is a difference between counting 0, 4 or 8 occurrences of the Vernal Equinox. The observation of the passenger, assuming he can count and remains focused on the Earth during the journey, can impossibly confirm all those predictions.

What am I doing wrong?

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# Time Dilation. I don't get it!

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