### Post by Radrook Admin on May 29, 2019 21:05:37 GMT -5

Time Dilation Calculations

The first time I encountered the concept of time dilation, was in a Twilight Zone episode where an astronaut returns to Earth still young but finds his fiancée an old woman. The second time was in the film starring Charlton Heston, Planet of the Apes. Just recently, another film was made called Interstellar which revolves around the same phenomenon but introduces the concept that a strong gravitational field can also have a profound time-dilation effect. In that case, it was a black hole that made hours spent on a planet within its gravitational field be the equivalent of decades back on Earth.

But the effects that those concerned about space-exploration are interested in are the effects that time dilation caused by velocity has on a spaceship's crew. Why? Simple, because it can shorten the amount time that they perceive as being onboard and make the trip easier. So let's see how the crew of a hypothetical ship traveling at different percentages of the speed of light would perceive such time.

Let’s start with our nearest star neighbor Alpha Centaury.

The distance from Earth to the Alpha Centaury group, is approx. 4.37 light years, or (25,690,000,000,000 miles).

Distance 4.37 LY Which means that at 186,000 miles a second it takes light 4.37 years to get to Earth.

50% Speed of light = The crew would perceive the trip as taking 7.5 years [ 93,000,999 mph]

At 70% Speed of light = perception would be 4.4 years

At 90 % Speed of light = perception would be 2.11 years

At 95% Speed of light = perception would be 1.43 years

At 98% speed of light = perception would be 0.88 of a year

At 99% Speed of light = perception would be 0.62 of a year

100 % Speed of light = perception would be 0 time

In other words you would need to travel at approx. 95 percent of light speed in order to cut the trip from Earth to Alpha Centauri system to a year and a half ship time. Total travel trip experienced as three years. But from Earth perspective, your trip would have taken 4.37 years to get there and another 4.37 years to get back. A total of 8.74 total years. So you might find your son whom you left behind as a twelve-year-old a full-grown man of twenty. Maybe even married and with a kid of his own. Your wife, whom you left as a thirty-four-year-old woman, is now forty-two. A bit unsettling when for you only three years have elapsed.

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Let’s consider something much farther away.

The star Betelgeuse is 649 light years away.

At 99 % speed of light, ship time is perceived as [ 91.19 years.]

Another trip back would would another 91.19 years ship time..

A total of 182 years ship time round trip.

But back on Earth, you would have been gone for 1,298 years.

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The center of our galaxy is approx. 26 million light years away. Even if travelling at 99,99% speed of light you would still perceive time on the ship as 367,723.10 years. That's Three-hundred and sixty-seven-thousand, seven -hundred and twenty-three years. But back on Earth, twenty-Six million years will have elapsed.

BTW

I have always wondered about that instant trip they talk about at full 100% light speed. How can the crew react to any emergency during the voyage when they don't have time to react? For them it is instantaneous, but the ship will still have to traverse that distance with all the dangers involved regardless of the crew's perception. A a lot of bad things can happen in a journey of 26 million Earth years. IMHO