If Nia is standing on the South Pole facing towards the northern hemisphere with a helium-filled balloon in her hand, and she releases it, in which direction will the balloon float and why? Respond very briefly.
The balloon will float upward away from the ground, regardless of Nia's position at the South Pole. The reason is that helium is less dense than the surrounding air, and this density difference causes the balloon to experience a buoyant force pushing it upward, counteracting the pull of gravity. The concept of 'upward' is away from the Earth's center, so at the South Pole, 'upward' would mean the balloon moves in the opposite direction from the ground under Nia's feet. The balloon's behavior is the same here as it would be anywhere else on Earth: it ascends because it is buoyed by the denser air surrounding it.