So other significant contributors to the science of all of human civilization are people like al-Marwazi. Al-Marwazi, once again, in Baghdad, and he would have been a contemporary of al-Khwarizmi, and he, if you've ever taken trigonometry, or if you're about to take trigonometry, he is accredited with coming up with the core trigonometric functions. We're talking about sine, cosine. Tangent and cotangent, it might have been Marwazi, or it might have been another mathematician named al-Buzjani, who came a little bit after, or a lot, depending on a human scale, but was also based in Baghdad. And together, they came up with the six, the six trigonometric functions. They weren't contemporaries of each other, but they both made significant contributions to what we now call trigonometry, including many of the trigonometric identities that we now learn in high school. Now, you also have physicists, mathematicians, astronomers like al-Hazen, and he is credited as getting one of the more sophisticated views of how light and vision works.