Johannes Kepler confirms his previously rejected discovery of the third law of planetary motion (he first discovered it on March 8 but soon rejected the idea after some initial calculations were made).

• 1618年的今天，约翰尼斯·开普勒肯定了先前被否决的发现的行星运行第三大定律（他于3月8日首次发现这一理论但是在随后的最初的计算后否认了这一说法）。