Rotating black holes may serve as gentle portals for hyperspace travel

January 9, 2019 by Gaurav Khanna, The Conversation
Feel like traveling to another dimension? Better choose your black hole wisely. Credit: Vadim Sadovski/Shutterstock.com

One of the most cherished science fiction scenarios is using a black hole as a portal to another dimension or time or universe. That fantasy may be closer to reality than previously imagined.

Black holes are perhaps the most mysterious objects in the universe. They are the consequence of gravity crushing a dying star without limit, leading to the formation of a true singularity – which happens when an entire star gets compressed down to a single point yielding an object with infinite density. This dense and hot singularity punches a hole in the fabric of spacetime itself, possibly opening up an opportunity for hyperspace travel. That is, a short cut through spacetime allowing for travel over cosmic scale distances in a short period.

Researchers previously thought that any spacecraft attempting to use a black hole as a portal of this type would have to reckon with nature at its worst. The hot and dense singularity would cause the spacecraft to endure a sequence of increasingly uncomfortable tidal stretching and squeezing before being completely vaporized.

Flying through a black hole

My team at the University of Massachusetts Dartmouth and a colleague at Georgia Gwinnett College have shown that all are not created equal. If the black hole like Sagittarius A*, located at the center of our own galaxy, is large and rotating, then the outlook for a spacecraft changes dramatically. That's because the singularity that a spacecraft would have to contend with is very gentle and could allow for a very peaceful passage.

The fictional Miller’s planet orbiting the black hole Gargantua, in the movie ‘Interstellar.’ Credit: interstellarfilm.wikia.com

The reason that this is possible is that the relevant singularity inside a rotating black hole is technically "weak," and thus does not damage objects that interact with it. At first, this fact may seem counter intuitive. But one can think of it as analogous to the common experience of quickly passing one's finger through a candle's near 2,000-degree flame, without getting burned.

My colleague Lior Burko and I have been investigating the physics of black holes for over two decades. In 2016, my Ph.D. student, Caroline Mallary, inspired by Christopher Nolan's blockbuster film "Interstellar," set out to test if Cooper (Matthew McConaughey's character), could survive his fall deep into Gargantua – a fictional, supermassive, rapidly rotating black hole some 100 million times the mass of our sun. "Interstellar" was based on a book written by Nobel Prize-winning astrophysicist Kip Thorne and Gargantua's physical properties are central to the plot of this Hollywood movie.

Building on work done by physicist Amos Ori two decades prior, and armed with her strong computational skills, Mallary built a computer model that would capture most of the essential physical effects on a spacecraft, or any large object, falling into a large, rotating black hole like Sagittarius A*.

Not even a bumpy ride?

What she discovered is that under all conditions an object falling into a rotating black hole would not experience infinitely large effects upon passage through the hole's so-called inner horizon singularity. This is the singularity that an object entering a rotating black hole cannot maneuver around or avoid. Not only that, under the right circumstances, these effects may be negligibly small, allowing for a rather comfortable passage through the singularity. In fact, there may no noticeable effects on the falling object at all. This increases the feasibility of using large, rotating black holes as portals for hyperspace travel.

Rotating black holes may serve as gentle portals for hyperspace travel
This graph depicts the physical strain on the spacecraft’s steel frame as it plummets into a rotating black hole. The inset shows a detailed zoom-in for very late times. The important thing to note is that the strain increases dramatically close to the black hole, but does not grow indefinitely. Therefore, the spacecraft and its inhabitants may survive the journey. Credit: Khanna/UMassD

Mallary also discovered a feature that was not fully appreciated before: the fact that the effects of the in the context of a rotating black hole would result in rapidly increasing cycles of stretching and squeezing on the spacecraft. But for very large black holes like Gargantua, the strength of this effect would be very small. So, the spacecraft and any individuals on board would not detect it.

The crucial point is that these effects do not increase without bound; in fact, they stay finite, even though the stresses on the spacecraft tend to grow indefinitely as it approaches the black hole.

There are a few important simplifying assumptions and resulting caveats in the context of Mallary's model. The main assumption is that the black hole under consideration is completely isolated and thus not subject to constant disturbances by a source such as another star in its vicinity or even any falling radiation. While this assumption allows important simplifications, it is worth noting that most black holes are surrounded by cosmic material – dust, gas, radiation.

Therefore, a natural extension of Mallary's work would be to perform a similar study in the context of a more realistic astrophysical black hole.

Mallary's approach of using a computer simulation to examine the effects of a black hole on an object is very common in the field of black hole physics. Needless to say, we do not have the capability of performing real experiments in or near black holes yet, so scientists resort to theory and simulations to develop an understanding, by making predictions and new discoveries.

Explore further: Can we see a singularity, the most extreme object in the universe?

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MrBojangles
5 / 5 (2) Jan 09, 2019
Uh-oh, the clock is ticking, it's only a matter of time now until Benni starts running his mouth about infinite density.
rrwillsj
1 / 5 (1) Jan 09, 2019
I think it will be most amusing when the anti-BH/GR/SR/QM/BB
woocultists tie themselves into lnots (the knuts for knots?) trying to reconcile their lunatic-fringe dogmatic fabulisms against their comicbook fantasies.
carbon_unit
5 / 5 (3) Jan 09, 2019
I'm kind of at a loss of how a macro object could go through a point (the singularity) and survive. Does space gently contract down a point? How does rotation affect the effects of falling into the black hole? Lot of "we did it" handwaveing here without an attempt at a simplified explanation a casual techie might understand. Or is it just too complicated?
The crucial point is that these effects do not increase without bound; in fact, they stay finite, even though the stresses on the spacecraft tend to grow indefinitely as it approaches the black hole.
The whole hole, the event horizon or the singularity??
Better choose your black hole wisely.
Yes, when falling into a black hole, it is good to have a workable exit strategy.

RobertKarlStonjek
not rated yet Jan 09, 2019
It is noteworthy that Einstein considered singularities as mathematical errors to be avoided, like a division by zero in ordinary algebra (which is the trick behind that high school equation that results in 1=2 !!).

A simple fix is to treat the increasing escape velocity with increasing mass the same way any other velocity in relativity is treated, that is, with a curvature in the equation that prevents the speed of light ever being reached. In special relativity this is called the relativistic addition of velocities. A 'relativistic addition of masses' is does the same for gravity.

An essay expressing a parallel for mass and escape velocity can be found here:

Anomalous Rotation of Galaxies and the Addition of Masses
https://www.faceb...2216884/
Da Schneib
5 / 5 (1) Jan 09, 2019
I seriously doubt this. Though it makes good science fiction.
Mimath224
5 / 5 (2) Jan 09, 2019
'...analogous to the common experience of quickly passing one's finger through a candle's near 2,000-degree flame, without getting burned....'
I would have thought an acetylene torch at full blast would be a more appropriate analogy and I most definitely wouldn't try passing a finger through that, Ha.

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