The world

“What is the world?”
My sister asked me this question one day while we were playing Lego. She looked so serious, that I thought she was actually joking.
I replied without thinking: “It's a round, giant, spinning ball.”
“If it's not round, is it still a world?”
“No. The world is round like a ball. It is what it is.”
“If it's not giant, is it still a world?”
“No. The world is giant, so we can all live on it. It is what it is.”
“If it doesn't spin anymore, is it still a world?”
“No. The world spins so the sun rises and falls. It is what it is.”
My sister seemed distracted and confused.
Her eyes on her Lego “steamboat” which she called the “Trinidad.”
She never follows the instructions.
“You are lying.” She said, “You are lying.”
I turned around. My eyes met with hers, which were shining like the north star.
I knew she was right.
So I replied, “Yes.”
“What is the world