[Muslim]

Why was this year chosen to be the beginning of the early modern era?

[Thompson_NCL]

August 3 – Christopher Columbus "sails the ocean blue" on his first journey across the Atlantic Ocean to the Americas.

It's the the year that the New World was discovered.

[Potemkin]

Personally, I would date the beginning of the early modern era from the Treaty of Westphalia of 1648. Henry VIII was clearly a late medieval monarch rather than an early modern one, so 1492 seems a bit too early to me. But yeah, it's the year Columbus discovered America. Of course, he didn't know at the time that he'd discovered a new continent, and it had already been discovered anyway about 500 years earlier by Vikings and, of course, about 20,000 years ago by the Native Americans....

[Goldberk]

I would date the beginning of the early modern era from the Treaty of Westphalia of 1648.

I absoloutely agree, the formation of modern nation states and principles of international relations are the bedrock of the modern era.

[MB.]

1648 is ridiculously late to establish the beginning of the Early Modern period. You two are mistakenly looking only at political modernity. I think if you also factor in economic, cultural and technological history you would agree that 1492 is the most convenient date. Although, Early Modernists really consider the conclusion of the entire 15th century itself the important transitional period, and the date 1492 is only used for convenience by the inexpert.