The future of the Earth will depend on many things, including increases in the brightness of the Sun, loss of heat energy from the Earth's core and change of the planet's orbit by the other things in the Solar System. The Milankovitch theory says the planet will continue to go into glaciation cycles because of the planet's difference in orbit from a perfect circle, the axis of the planet tilting, and pushing of the Earth's orbit. As part of the supercontinent cycle, plate tectonics may create a supercontinent within 250 million–350 million years. Some time in the next 1.5 billion–4.5 billion years, the axis's tilt may begin to change into bad versions, with changes in the axis's tilt of up to 90°.