Today, in our environmental science lecture, we're discussing renewable energy sources. Solar power is widely used, but it has limitations, such as inefficiency on cloudy days. Wind energy, on the other hand, is more consistent in coastal areas. However, the professor points out that geothermal energy, which harnesses heat from beneath the Earth's surface, is the most reliable option because it operates 24/7 regardless of weather conditions. Despite its high initial installation cost, many countries are investing in it for long-term sustainability.