RE: You just can\'t...
What Jake67 describes is of course the traditional method of time dilation, not real "time travel". But just to clear this up, the dilation is not due to the Doppler effect, which only affects the wavelengths of the light you emit, making the light redder as you speed away and bluer as you come back. The time dilation comes as a natural consequence of general relativity.
And, to answer Jenee, time dilation precludes time travel to the past, because it isn't real time travel - you have to go through the time, you just experience it passing differently.
What Jake67 describes is of course the traditional method of time dilation, not real "time travel". But just to clear this up, the dilation is not due to the Doppler effect, which only affects the wavelengths of the light you emit, making the light redder as you speed away and bluer as you come back. The time dilation comes as a natural consequence of general relativity.
And, to answer Jenee, time dilation precludes time travel to the past, because it isn't real time travel - you have to go through the time, you just experience it passing differently.