Read this. You will be blown away.?

There are twins, Al and Sal. They were born 4 minutes apart of each other. On their 25th birthday, Sal is offered a trip into space while Al has to stay on Earth. So Sal hops into a rocket and goes on her interstellar trip into space. Al stays on Earth. When Sal returns to earth, she has only aged 6 years. So now she is 31 years old. this is where it gets interesting. Since Al stayed on Earth the entire time, he has only aged 20 years. So now he is 45 years old. How is this possible? how can 2 twins be of different ages at the reunion? This is called "The twin paradox." Time move slowly in space than it does on earth. So in the same time period they have aged differently. I heard this in my physics class and I was blown away.