Which is precisely how it would work with wormholes. Wormholes can be turned into time machine in the following way. Remember that time travel to the future is

Which is precisely how it would work with wormholes. Wormholes can be turned into time machine in the following way. Remember that time travel to the future is pretty trivial: Just accelerate a lot and enjoy the effects of time dilation. So in order to travel into the past, you create a wormhole pair and put one of the wormholes on a speedy two-way trip. If you now traverse the wormhole that was on the trip (and which has traveled into the future), you travel backwards in time. But not further than when the pair was created.