What would happen if earth's properties changed? How could that effect life?

The Earth’s core is cooling down very slowly over time. One day, when the core has completely cooled and become solid, it will have a huge impact on the whole planet. Scientists think that when that happens, Earth might be a bit like Mars, with a very thin atmosphere and no more volcanoes or earthquakes. Then it would be very difficult for life to survive – but that won’t be a problem for several billions of years.

81 is a composite number

The correct answer is kettles.