 Gravitational time dilation is also the answer to the twin paradox that we covered in the previous segment on special relativity. The key interval is at the halfway point. As the spaceship approaches Vega, it decelerates to a stop and then re-accelerates back to the Earth. The traveling twin finds that she is in a gravitational field. Let's say her acceleration is 10 G's or 98 meters per second squared. At this rate, it would take her 35 days to decelerate to zero and another 35 days to re-accelerate back to 99% of the speed of light. Gravitational time dilation shows that as her clock ticks 70 days, her twin's clock on Earth will have ticked 18,134 days. That's 48 years. The twin on Earth agrees. So, instead of both twins thinking the others should be younger, they both agree that the twin on the rocket to Vega and back is younger. No contradiction is involved and the paradox is resolved.