Planets can exist for billions and billions of years but they cannot last forever.
There are different ways that a planet like Earth could die. For example, Earth could be destroyed by a bombardment of asteroids.
Another catastrophic event that could occur is when the sun turns 10 billion years old. Scientists expect that it could run out of hydrogen and expand more than 100 times its current size. When this occurs, Venus and Mercury would definitely be swallowed up by the sun.
Earth which is further out may also become swallowed by the sun or be pushed much further out by the sun's gravity.
All of this could happen 7.6 billion years from now. As the sun expands and reaches its maximum size as a red giant, it will shine 3000 times brighter.
Scientists agree that the sun is expanding but they still remain uncertain about Earth's fate. Will Earth really become engulfed by the sun or will Earth just drift apart away from the gravitational pull of the solar system?
Most scientists are convinced of the former that the Earth will be pulled towards the sun. Once that happens, the planet will disintegrate.
While these events may not take place for another 5-7 billion years, scientists estimate that the human race has only one billion years left. In one billion years, the oceans will become boiling hot. The sun's brightness has been increasing by 10% every billion years. With this increase, the Earth will finally become inhabitable for humans.