who are some to which two theories do lines 1-2 refer

Unfortunately, I can’t tell you which specific theories lines 1-2 refer to without knowing the content of those lines. However, based on the context you provided (“Some say the world will end in fire. Some say in ice.”), it’s highly likely the lines refer to two opposing theories about the end of the world. Here are two possibilities:

1. Destruction by Fire and Destruction by Ice:

• Fire can symbolize war, destruction, passion, or burning out.
• Ice can symbolize a slow, gradual decline, glaciation, or an emotionless ending.

1. Heat Death and Big Freeze:

• These are scientific theories about the ultimate fate of the universe.
• Heat Death suggests the universe will eventually reach a state of maximum entropy, with all energy spread out uniformly, leading to a stagnant and lifeless state.
• Big Freeze suggests the universe will continue to expand and cool forever, eventually reaching a point where stars can no longer form and the universe becomes a cold, dark place.

The poem “Fire and Ice” by Robert Frost most likely uses the first interpretation (fire and ice as symbolic forces of destruction) but without seeing the lines themselves, it’s impossible to say for sure.