posted by Lorry .
Hi,I need help with question 1) There were twins on our planet earth. They were physicst. One of them were sent to space at his 20 year. When he comes back after 20 years of stay in the space he was 40 years but his brother who stayed on earth was 60 years old. How can it be? 10 Q!
i suggest you read "Twin Paradox"