Relativity Lite

30 | Relativity Lite from the same page where you downloaded this book, https://doi.org/10.15760/pdxopen -2 9 . Open the file “Alpha Centauri Trip 3c 10Eflash” and set “Frame: Earth” in the upper left-hand corner if you wish to step through it as you read, though hopefully the screenshots below will give you a sufficient experience without needing RelLab. You agreed to also send out pulses at the same frequency of 1.456 years , but did you? Your twin indeed sent out a pulse at 1.456 years that can be seen (from our omniscient view) well spread out in space in figure 2, 1.90 years after you left, but yours is a tiny ring (just visible in figure 2) to the saucer’s left, about a month after emission at 1.82 years . Why did you delay it after promising to be faithful? Figure 1. RelLab setup. Alpha Centauri is 4.37 light-years fromEarth’s Sun. The grid lines are 1 c year apart. Figure 2. At 1.90 years into the trip, a month after the saucer has emitted its first pulse of light and about five months after the Earth twin emitted her first pulse. Oh, that’s right, this is simply the time-dilation factor working, with our γ = 1.25 for v = 0.6 c: 1.25 × 1.456 yr = 1.82 yr . This light pulse reaches Earth at 2.912 years , shown two months afterward in figure 3. It will be easiest to do the time comparisons if we simply count such pulses returning to Earth. Let us label this red one “count 1” of the outbound trip. That the red ring of light from the saucer and the small orange one just emitted by the Earth continue to share a wave-front means that the light emitted by the moving saucer and from the still Earth indeed move at the same speed, c . In figure 3 and following, I have overlain colored halos around the black rings of light shown in the RelLab screenshots. Their order in time is indicated by their place in the spec- trum from red to lavender to help track the rings in subsequent figures.