Time Travel

Could A Kerr Black Hole Be Used To Travel Through Time?


Common knowledge tells us that a journey into a black hole ends, well, badly.

That’s because its center — the singularity — is an infinitely dense region of space-time, from which nothing can escape.

But, as our twisted universe would have it, there’s actually a certain type of theoretical black hole that may lack a singularity — one that you could safely enter, and one which could, theoretically, allow travel though time.

The Kerr Black Hole

In 1963, mathemetician Roy Kerr proposed the idea of a rotating black hole through which something could travel without being crushed into oblivion. It’s called a Kerr black hole, or a Kerr ring.

It would form after the collapse of a neutron star; instead of collapsing into the common, infinitely-dense singularity, it would create a ring of rotating neutrons, their centrifugal force preventing the singularity from forming at all.

This would, theoretically, allow safe passage through a wormhole within the black hole, avoiding the aforementioned spaghettification and opening the way for a very interesting possibility:

On the other side, somewhere out there, would be a “white hole,” ostensibly the opposite of a black hole, spewing out the contents that had been sucked in. It would act as a bridge that would allow travel through both time and space or, perhaps, into another universe.

There is, of course, no evidence of the existence of either rotating Kerr black holes or white holes, but let’s assume for a moment that they do exist.

Using Kerr Black Holes For Time Travel

A Ring Of Black Holes
Image: X-ray: NASA/CXC/MIT/S.Rappaport et al, Optical: NASA/STScI via CC by 2.0

Could a rotating black hole be used to travel through time?

The problem with using a Kerr black hole as a means of travel, through time or otherwise, is that you never know where you’re going to end up. Unless you developed some way to calibrate or position the “white hole” on the other side, there’s no telling where, when, or in what universe you’d find yourself.

If you could control the other end of the wormhole, however, you could potentially create a closed time-like curve.

You’d have to somehow keep the rotating black hole stationary, while sending its other end, the “white hole,” on a near-lightspeed voyage into the future. You could then pass through the black hole and end up on the other side, and vice versa, knowing (more or less) where and when you’d be going.

That wouldn’t allow you to travel to the past from your point-of-view, but it would allow those in the future to visit your present, or their past. Time travel for everybody, then, one way or the other.

But it all boils down to the ability to control a theoretical type of black hole. In other words, it’s nothing but extraordinary speculation. Perhaps, then, we should just throw caution to the wind and ask a certain alleged time traveler his thoughts about this madness.

John Titor & The Kerr Black Hole

According to John Titor, his time machine used two microsingularities to distort the gravitational field around the machine enough to “replicate the affects (sic) of a Kerr black hole.” This ostensibly achieved the fantastical time-travelling abilities of a Tipler cylinder, proposed by Frank Tipler in 1974.

The microsingularities, said Titor, were “manipulated by ‘injecting’ electrons onto [their] surface.”

Now, while I’m fuzzy on the science involved in manipulating black holes (haha), it was theorized by Kip Thorne in the 1980s that you could control (i.e., “hold open”) a black hole’s wormhole by using some kind of “negative energy.”

So, in the grand scheme of theoretical gobbledygook, it sounds okay.

In the end, John Titor’s microsingularities not only took him through time, they took him into another universe entirely, what he called a “worldline.” As the story goes, because it was another universe altogether, any and all temporal paradoxes were cleanly avoided. That’s one of the possibilities of venturing through a Kerr black hole.

So, if the universe did allow for time travel, I actually do think it would end up much like Titor described it: using black holes, and avoiding paradox through the existence of many worlds.

A Kerr black hole (or something similar), then, seems a likely candidate for the world’s first time machine.


Rob Schwarz

Rob Schwarz is a writer, blogger, and part-time peddler of mysterious tales. Editor-in-chief of Stranger Dimensions.


  1. I loooove thinking about this stuff… especially thinking about riding around the event horizon of the black hole at lightspeed, time going slow within your ship, and then you’re traveling into the FUTURE.

    So awesome.


    1. Hey David,

      The future’s cool, but I always thought circling a black hole sounded like an awful lot of trouble to get there. I guess the upside is that we know (more or less) it’d be possible.

      But the past! I want to ride an iguanodon, visit the 1904 World’s Fair, or pick up a copy of Earthbound on SNES for $25. Probably never going to happen, but hey.

      Thanks for your comment!

  2. The problem with a Tipler cylinder ( http://en.wikipedia.org/wiki/Tipler_cylinder) is that it needs to be infinite in length. A way to build an infinite rotating cylinder is to build it in orbit around a system of neutron stars. Each neutron star will bend space, in the same way a star bends light (http://astro.berkeley.edu/~jcohn/lens.html).

    Each neutron star would bend the tiplers cylinder a fraction of a degree. Set up enough neutron stars and the cylinder wil bend around itself like a hula hoop (actually space will bend where, the cylinder follows the curve of space). In turn the neutron stars will need to be in orbit with its companions so that they don’t collapse into a black hole.

    To build the large number of neutron stars will require a fleet of bussard ramjet bull dozers (http://www.amazon.com/The-Iron-Sun-Crossing-Universe/dp/0446897965) scooping up intsteller gas and dust. To build the fleet of Bussard ramjet bulldozers requires self replicating factories (http://www.molecularassembler.com/KSRM.htm).

    All of this can be done with out a blackholes and our current understanding of physics. So lets build a time machine

    1. Nevermind that we cannot even get close to clusters of neutron stars as it is technologically infeasible right now — neither is our understanding of physics that complete

  3. Hey, who wants to build the phonewave… Its 2017 already and we need to move fast.

    El. Psy. Kongroo..

    1. We can only wait for our WW3. They may cover it as a Trump-Putin thing, but it is a time machine race.
      But worry not, our lord and savior Hououin Kyouma will descend from the heavens (I mean trauma from losing Mayuri and Kurisu) and move forward so that all of us may reach Steins;Gate.
      El. Psy. Kongroo…