user: What are the differences between an upright piano and a grand piano?

assistant: The main differences between an upright piano and a grand piano are:
- action mechanisms: an upright piano utilizes a string action to allow vertically placed hammers to reset, while gravity returns the hammers in a grand piano, offering better responsiveness and repetition speed
- pedals: a grand piano usually have 3 pedals, and an upright piano has 2 or 3 pedals with different functions.

Though it depends on the specific models and conditions, a grand piano usually offers better dynamic range and richer resonance than an upright piano.

user: What were all the earlier names for the city presently known as Chennai?

assistant: Chennai traces its roots back to a fishing village called Madrasapattinam. The British officially named it Madras when they purchased the land in the 17th century. The name of the city was changed to Chennai in 1996.

user: Why do people blink?

assistant: Each time the eyelids close, salty secretions from the tear glands are swept over the surface of the eye, flushing away small dust particles and lubricating the exposed portion of the eyeball. In essence, people blink because to cleanse and moisten the eye.