Who travel to the US and Europe returned japan with new ideas?

The Japanese who traveled to the US and Europe and returned to Japan with new ideas were known as the Rangakusha (蘭学者). The Rangakusha were a group of scholars, translators, and intellectuals in Japan who studied Western learning, particularly Dutch studies, during the Edo period (1603–1868). They were instrumental in introducing new ideas and knowledge from the West to Japan, which influenced Japanese society and culture in various ways.

The Rangakusha primarily studied Dutch because the Netherlands was the only Western country with which Japan had direct trade relations during the period of national isolation known as sakoku. They learned Dutch language, science, medicine, astronomy, mathematics, geography, and other fields through the study of Dutch books and by interacting with Dutch merchants and scholars in Nagasaki, the only port open to foreign trade.

Here are some notable Rangakusha who returned to Japan with new ideas:

Hiraga Gennai (1728-1780) was a polymath who studied Western medicine, astronomy, geography, and engineering. He introduced the concept of smallpox vaccination and developed various inventions, including a thermometer, a barometer, and a clock.

Sugita Genpaku (1733-1817) was a physician who translated the Dutch book "Ontleedkundige Tafelen" (Anatomical Tables) into Japanese. This work introduced Western medical knowledge and anatomical illustrations to Japan and had a significant impact on Japanese medical education.

Maeno Ryotaku (1723-1797) was a scholar and translator who introduced Western knowledge in various fields, including medicine, astronomy, and natural history. He translated Dutch works on botany and zoology, contributing to the development of natural sciences in Japan.

Otsuki Gentaku (1757-1827) was a physician and scholar who translated Dutch medical texts and introduced Western surgical techniques to Japan. He also established a school of Western medicine in Osaka.

Takahashi Sakuzaemon (1764-1804) was an astronomer who studied Western astronomy and introduced telescopes and other astronomical instruments to Japan. He made important observations and calculations, contributing to the development of astronomy in Japan.

These Rangakusha and many others played a significant role in bringing new ideas, knowledge, and technologies from the West to Japan. Their efforts contributed to the modernization and development of Japan in various fields, ultimately leading to the end of the sakoku policy and the Meiji Restoration in 1868.