请将下面这段话翻译成英文：

印刷术发明之前，想出版新书的学者必须一字一字地抄写。北宋时期，经过多年的实验，毕昇发明了活字印刷术(movable-type printing)。他把汉字刻在一小块泥胚(pieces of clay)上，加热汉字直到其变成硬的活字。印书时,人们按顺序将活字摆在一起，印出印迹。印刷完后，他们把字分开，以后重复使用。这种方法既经济又省时。中国的活字印刷术首先向东传至朝鲜和日本，之后向西传至波斯(Persia)和埃及，最后传遍全球。活字印刷术的发明大大促进了世界各国的文化交流。

参考翻译

Before printing was invented，a scholar had to copy characters one by one if he wanted to publish a new book.During the Northern Song Dynasty, Bi Sheng invented the movable-type printing after many years of experimentation.He engraved the characters on small pieces of clay,and heated them until they became hard movable characters.When printing a book，people placed the moveable characters in order into a whole block and then ran off a print.After printing, they took the block apart and reused the characters later.This method was both economical and time-saving.China’s movable-type printing first spread eastward into Korea and Japan,then westward into Persia and Egypt,and at last,around the world.The invention of movable-type printing greatly promoted the cultural exchanges among countries all over the world.