My 10 year old son got a planetarium for Christmas and he justy asked me what will happen when the sun gets bigger (turns into a red giant). We decided thatall the planets will be swallowedup by the sun. However, he just said but after it has swallowed mercury and venus wont it just push earth away cause it will have more gravity? I have no idea lol, anybody
Not really thought about this in any great depth mycats, but... even if the planets being swallowed up by the sun was only due to gravitational attraction ( it isn't. by the way), then a body having more gravity would be even more likely to attract other bodies. Of course, the mass of such planets are incredibly small when compared to the mass of the sun so this doesn't really apply either :)
The Sun will have lost a lot of mass in 5 billion years so the Earth may be in a slightly different orbit but it will still have it's atmosphere boiled away and be roasted to a husk.
I don't know if anybody knows for sure whether the Earth will be engulfed or not, certainly when I was 10 it was believed that it would be but ideas have changed a bit.
What's almost certain is that no species will survive the grip of evolution for 5 billion years, it was after all only 4.5 billion years ago that the first primitive life began.
If any eyes gaze on the red giant Sun they won't be human
Considering the explosive advances of technology in our recent past the Earth may well be integrated into a maneuverable spacecraft in its own right in a thousand or million years. Evolution has certainly taken a remarkable twist with the development of conceptual beings. Hopefully the universe will continue to be admired by such creatures for a very long time to come.
In line with jake-the-peg's excellent (as usual) contribution, here are some more details on The Future of our Solar System