A wormhole, as science fiction fans well know, is a gateway between different locations in the universe, a tunnel that “skips” all the space in between, a shortcut a little like the hole a worm bores trough an apple instead of travelling around its surface. The thing about space that may be a bit hard to grasp (I don't quite get it myself) is Einstein's theory of General Relativity defines time as a fourth dimension—that our universe does not just exist in width, length, and height, but also in time. Sooo, a wormhole could exist that crosses not simply between different places in space, but also between different regions in time.
One of these time wormholes could have a date of 2012 AD on one end and 2012 BC on the other. You would go in from our now and exit in a time where Abraham the patriarch hasn't been born yet—or instantaneously go the other way. Stephen Hawking, by the way, believes radiation would enter a wormhole through time and create a feedback loop like the amplifier noise from a speaker behind a microphone, a feedback that would ultimately destroy the wormhole. Not to mention the problems with creating such a wormhole in the first place and keeping it open…
But let’s imagine we have these problems solved—after all, this blog is about story ideas, not physics. For the sake of the story, let’s say we deal with the feedback loop by putting the ends of the wormhole a vast distance apart from one another, say on the scale of a galaxy vast. And we place both ends of the wormhole in a region of space with low radiation, in intergalactic space.
Then let’s imagine something else—say we were to create a wormhole in which both ends start out in the same time, but then we rotated the far end up to the speed of 99.99999999% the speed of light (the near end resting in place), tracing a massive arc around the stationary end of the wormhole at a sort of pivot point. As explained by Einstein’s Special Relativity, the near-lightspeed end of the wormhole would be in a condition in which time would pass more slowly on that end. At 100% the speed of light, a speed nothing made of matter can fully attain, time would not flow at all.
Soon, the massive spinning wormhole would become a time machine. Our end at the center would have time flowing normally for us, while at the far end time would hover near the moment our massive time-travel device was constructed.
Imagine a story where such a device is discovered by a future human civilization already in existence somewhere outside our galaxy, created at some time in the past by mysterious aliens, this massive spinning “wheel” of time. And I would give it multiple spokes, multiple long spinning wormholes, each a galaxy arm in length, each with different near-lightspeed percentages (one being 99.9 percent the speed of light, let’s say), so the end of one would be very near the creation of the device but for others, even though time had slowed, a great deal of time would still have passed on the far end. Multiple arms could create multiple places in time the machine would allow you to go between when the device had first been created and now.
Even if you imagine the aliens created this device, say, 5000 years ago, entering the wormhole on one end could put you at 2012 BC or earlier and at several times between then and now, depending on the spokes of this “Wheel at the Heart of the Universe.” Problems would arise in that you would come out on the far end in deep space, going very very fast, and to interact with anything in the regular universe, you’d have to do quite a lot of slowing down…but imagine some high-tech futuristic heroes, who are able to figure that out—imagine where they would go and what they would do...