Time Travel
Scientists at the National Science Foundation released this first photo of a black hole on April 10, 2019. Some believe that time travel is possible through black holes.
Read the following article. Pay special attention to the words in bold.
If you could travel to the past or the future, would you do it? If you could travel to the past, would you want to visit anyone? If you could travel to the future, would you come back to the present and warn people about possible disasters? Time travel, first presented in a novel called The Time Machine, written by H.G. Wells over 100 years ago, is the subject not only of fantasy but of serious scientific exploration. About 100 years ago, Albert Einstein proved that the universe doesn’t have three dimensions but it has four—three of space and one of time. He proved that time changes with motion. Einstein believed that, theoretically 1, time travel is possible. The time on a clock in motion moves more slowly than the time on a stationary clock. If you wanted to visit the Earth in the future, you would have to get on a rocket ship going at almost the speed of light 2, travel many light-years3 away, turn around, and come back at that speed. While traveling, you would age more slowly. Einstein came up with an example he called the “twin paradox.” Suppose there is a set of 25-year-old twins, Nick and Rick. If Nick decided to travel fast and far on a rocket ship and Rick decided to stay at home, Nick would be younger than Rick when he returned. 316
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Specifically, if Nick traveled 25 light-years away and back, the trip would take 50 “Earth years.” Rick would be 75 years old, but Nick would be 25 and a half years old. If Nick had a five-year-old daughter when he left, his daughter would be 55 years old. So Nick would be visiting the future. Using today’s technologies, time travel is still impossible. If you wanted to travel to the nearest star, which is 4.3 light-years away, it would take 80 thousand years to get there. (This assumes the speed of today’s rockets, which is 37 thousand miles per hour.) According to Einstein, you can’t travel faster than the speed of light. While most physicists believe that travel to the future is possible, it is believed that travel to the past will never happen. Although the idea of time travel seems the subject of science fiction, not science, many discoveries and explorations, such as traveling to the Moon, had their roots in science fiction novels and movies. 1 2
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t heoretically: possible in theory but not proven speed of light: 299,792,458 meters per second (or 186,000 miles per second) light-year: the distance that light travels in a year through a vacuum (6 trillion miles or 9.46 trillion kilometers)
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