Relativity Lite

ATrip to Alpha Centauri | 39 running RelLab, open the file “Alpha Centauri Trip g acc 7c10” and set “Frame: Saucer 1” in the upper left-hand corner. You can also play the linked movie “Alpha Centauri Trip g acc 7c10.mp4.” In either case, you will see that I have imposed a grid on it whose small squares are 1/4 of a light-year apart. The effects of acceleration will come into play only while the saucer is within that distance of the Earth or Alpha Centauri. Since we are taking a while to get up to speed, the round trip will take a bit longer than before, t = 15.8426 Earth yr , as will be the time between pulses so that 10 are emitted by the Earth. The ratio of the round trip Earth time to saucer time is 1.21539 rather than 1.25 , but all else is pretty much the same. We will start by having 2 pulses of light be emitted by Earth before the saucer leaves so that we can see the acceleration (rapid frame shift) more easily on the first part of the trip. But it is the period when the saucer decelerates into Alpha Centauri and immediately starts the boost back up to speed toward the Earth that the saucer’s perspective shift from frame to frame becomes clear. Please note that the language of this paragraph is chosen to match the reality: it is the saucer that accelerates and decelerates. However, in subsequent paragraphs and in the figures, we will talk about and show the saucer frame, in which the saucer is at rest and it is Earth and Alpha Centauri that move. Stop the movie at 56 seconds, when the clock shows 5.1 years , just before deceleration. This is also shown in figure 18. There are 12.2 grid lines between the Earth pulse that is just touching the right-hand frame and the one catching up to the saucer. Watch what happens to the distance between pulses seen from the saucer frame when we start to slow down. Clearly, we are rapidly changing frames of reference. Figure 18. At 5.1 years into the trip, just before the moving saucer starts its deceleration. Figure 19. At 6.5 years into the trip, as Alpha Centauri reaches the saucer.