During World War I, the United States military used Cherokee and Choctaw service men, among others, to relay secret tactical messages based on words from their traditional tribal languages. These became known as 'Code Talkers'. Although Native American languages were used during WWI, it wasn’t until WWII that an organized code
Outer space is the expanse that exists beyond Earth's atmosphere but a clear boundary between the two is impossible to define because the density of atmosphere gradually decreases as altitude increases. However, the Kármán line at 100 km above sea level is generally used to mark the beginning of outer space
It is commonly believed that, on 12th October 1492, Italian explorer Christopher Columbus 'discovered' the Americas, but this merely marks the beginning of European colonialism. Although there are legends of Irish monks and Chinese fleets reaching shore long before, the first documented settlers are Vikings. Leif Erikson (c. 970 – c.
Following the terrorist attack on the World Trade Centre in September 2001, commercial flights were grounded across the United States for three days and three nights. This absence of aircraft contrails provided an unprecedented opportunity to study their contribution to global warming. It has been argued that contrails reflect heat back
Until its reclassification as a dwarf planet in 2006, Pluto was considered to be the ninth planet. However, it is now believed that there really is a ninth planet beyond the Kuiper belt - the cold scattered disc region towards the outer edge of the Solar System. First proposed in 2015,