Here are some one liners...
Arsenic as a Medical Cure? -- Arsenic is used for the first time as a medical treatment.
The Battle for China and the Rise of the Sweet Potato -- The Ming forces attempt to break a dam and flood out the Manchu but the Mings flood themselves out instead. I talk about the sweet potato that sustains the populous in the midst of war.
The King Declares War Against His Own Government -- King Charles tries to arrest the Parliament leaders who have defied him, but the King must escape instead and declares war against the Parliament.
Arsenic as a Medical Cure?To be clear, arsenic is a deadly poison. It is the poison of choice for kings... meaning that it is the poison most used ON KINGS and other noblemen. Arsenic is rarely found in its elemental form, but by 1649, Johann Schröder will publish two methods for extracting elemental arsenic from other compounds. This year arsenic is used for the first time as a medical treatment. Exactly what they are treating is unclear, but before antibiotics are discovered in the 20th century, arsenic will be one of the few cures for syphilis... the other cure being malaria. Apparently if you make yourself so sick that you are about to die, the syphilis expires shortly before you do. Then, hopefully, you can recover. Don't bet on it, though.     
The Battle for China and the Rise of the Sweet PotatoIt has been a few years since the Manchu dynasty declared its dominance over the Ming dynasty but the rebellion continues. The Manchu forces have surrounded the city of Kaifeng which are supporters of the Ming Emperor. Kaifeng has undermined the dam holding back the Yellow River. The idea is to break the siege and drown the rebellious Manchu. Instead, the waters get out of control and flood the city instead. The city stands at the crossroads of major merchant traffic, but this man-made flood will diminish the city forever. This flood also ends the Golden Age of Jewish settlement in China. The Kaifeng Jews will scatter, and many will be lost. The lone synagogue that has stood since 1163 has been swept away by the waters. This rebellion will go on for two more years. When the Manchu forces finally enter Beijing, the Emperor will take his own life and the transition to Manchu control will be complete.  
The King Declares War Against His Own GovernmentAt the end of last year the British Parliament (called the Round Heads) laid a document of complaints before King Charles the 1st. He has considered them carefully and tries to have the opposition leadership arrested. Apparently the strength of the opposition is greater than the King anticipated so he escapes London and raises his standard over the castle in Nottingham. It is the beginning of the first British civil war between the Round Heads that support the Parliament and the Cavaliers who are the royalists. Oliver Cromwell is rising quickly within the military. They call him "Old Ironsides" and he will eventually defeat the royalists.   
This Year on Wikipedia
Year 1642, Wikipedia.