Rock Age Paradox

If a rock on Mercury formed at the same time as a rock on Earth, the rock on Earth will be older than the rock on Mercury. 

Why? 

Because Mercury is moving faster than Earth and it is closer to the sun, the sun's gravity slows down time and so does speed. The faster you move, the more your time slows down. The more gravity is near you, the slower time passes. 

It's a paradox because in the example, both rocks formed at the same time, but the one on earth is older. 

Too Fast

One of the reasons why NASA don't send probes to land on the surface of Mercury is because the planet is moving too fast. Mercury is traveling at 48 kilometres per second. It is the fastest moving planet in the solar system. The closer you are to the sun the faster you have to move to stop yourself cascading into the star. It is very hard to get probes to travel at close to 48 kilometres per second

image generated by artificial intelligence (chatGPT) 

Earth is traveling slower than mercury but it is still moving fast, 30 kilometres per second. It is possible to meet the planet in it's path but the sun's gravity would interfere in the rendezvous. Mercury is 3 times closer to the sun than Earth although it has a highly elliptical orbit and can be as far as 70 million kilometres from the sun. 

Sources : 

Book: The Planets by Professor Brian Cox

Website: https://science.nasa.gov/mercury/

Website: Wikipedia