Mrs Black lived in a city of England. Her husband died two years ago and one of her children worked in the capital and the other three lived in another town. Her husband didn't leave her much money and she had to live a simple life. Sometimes her children went to see her during their holidays，but they stayed with her for only two or three days. Luckily she had a cat with her. She liked it very much and took it everywhere she went.    One winter morning the old woman got up early. She was going to buy some food in a shop. And when she came out, she found there was much snow in the street. She had to sweep it away. And suddenly she found the cat at the corner of the house. And then she laughed .Her cat caught a big mouse.

处理微观、高速物体的动力学问题，牛顿经典力学不再适用．20世纪初，著名物理学家____（人名）建立了狭义相对论，阐述物体做以接近光的速度运动时所遵从的规律．