1. Mid Winter Day is a big holiday in Antarctica.

2. In Antarctica, Mid Winter Day is a big holiday.
[Does 'in Antarctica' modify 'a big holiday'? Can 'in Antarctica' modify the verb 'is'? If 'in Antarctica' modify 'is', then the meaning is similar to that of Sentence 2, right?]

Both sentences mean the same thing. In 1, the prep phrase clearly modifies “holiday,” while in 2, it could be considered adverbial.

No, in both sentences, the phrase "in Antarctica" is not modifying the noun "a big holiday" or the verb "is." Instead, it functions as an adverbial phrase, providing additional information about where the holiday is celebrated.

In sentence 1, "Mid Winter Day is a big holiday in Antarctica," the phrase "in Antarctica" specifies the location where the holiday is significant.

In sentence 2, "In Antarctica, Mid Winter Day is a big holiday," the phrase "in Antarctica" is placed at the beginning of the sentence to emphasize that the holiday is specifically celebrated in Antarctica.

Therefore, while the meaning of both sentences is similar, the difference lies in the placement of the adverbial phrase "in Antarctica."