How many years can the earth last?

The life span of the earth is about 4.6 billion years. It is generally believed that the earth cannot exist longer than the sun, because the sun will expand into a red giant in old age (this is a process that all stars have to go through, and its volume will expand many times in old age). At that time, the sun will expand to the size of the orbit of Mars, so it will engulf the earth. Of course, before this, the earth may also be destroyed by "space accidents", such as the collision of comets. Of course, these are all accidents. However, with the development of science and technology, interstellar migration and even moving the earth's orbit should be realized in the future, so there is still hope for human survival.