Summary: Old English was the language spoken during 5th to mid-12th century; Middle English was spoken during mid-11th to late 15th century. Old English developed and originated from North Sea Germanic; Middle English developed from Wessex.
Similarly, you may ask, why Old English changed to Middle English?
Old English also reflected the varied origins of the Anglo-Saxon kingdoms established in different parts of Britain. The Anglian dialects had a greater influence on Middle English. After the Norman conquest in 1066, Old English was replaced, for a time, by Anglo-Norman as the language of the upper classes.
Also Know, how did Middle English change to modern English?
A major factor separating Middle English from Modern English is known as the Great Vowel Shift, a radical change in pronunciation during the 15th, 16th and 17th Century, as a result of which long vowel sounds began to be made higher and further forward in the mouth (short vowel sounds were largely unchanged).
Is Spanish older than English?
Old English is, IMO, most definitely a separate language. For Spanish, we have Old Spanish, 10th to 15th century, when a consonant readjustment (Reajuste de las sibilantes del idioma español - Wikipedia, la enciclopedia libre, for Spanish speakers) marked the birth of Modern Spanish.
When did English become modern?
Modern English (sometimes New English or NE (ME) as opposed to Middle English and Old English) is the form of the English language spoken since the Great Vowel Shift in England, which began in the late 14th century and was completed in roughly 1550.