
Rotating Black Holes May Serve as Gentle Portals for Hyperspace Travel - Pharmakon
https://theconversation.com/rotating-black-holes-may-serve-as-gentle-portals-for-hyperspace-travel-107062
======
cletus
Put me firmly in the camp that believes the speed of light is a hard limit on
the universe and I'll use Isaac Arthur dismissal of FTL travel as to why.

He contends that there likely isn't a sentient civilization within about a
billion light years of us because the signature of Dyson spheres would be
unmistabkable and unmissable. Now this isn't to say there isn't one that's
say, 600 million light years away that built their first Dyson sphere 500
million years ago although, in practice, this doesn't really change the
probabilities that much.

If there's FTL then that billion light year practical limit really goes out
the window as you can effectively get anywhere in the universe, making the
volume of absence be many, many times the size of the observable universe.

I'm not sure why the author is talking about gravity ripping you apart in a
black hole. It Is Known [tm] that larger black holes have pretty gentle event
horizons.

I'm not sure why it matters that a black hole would be spinning. You can
pretty much assume every significant mass in the universe is spinning to some
degree (a state of zero spin being highly unlikely over even small amounts of
time).

The author talks about the inner event horizon and I guess that's the point.
But all of that is highly theoretical. Nothing is known about the inner
workings of a black hole. It's all highly theoretical and beyond the ability
of general relativity to describe. No other theory has been able to adequately
explain or describe gravity let alone extreme gravity so your view on what's
within the event horizon probably depends on which unproven theory (eg string
theory) you subscribe to.

So this is speculation based on speculation.

~~~
imglorp
I'm in a more conservative camp than speed limits: the practicality one.

Even if we ignore the ponies and rainbows of wormhole travel, if you want to
travel to a plain black hole to use the magic teleporter, the nearest two are
V616 Mon at 11 solar masses and 3000 LY away, and Cyg X1 at 15 SM and 6000 LY.
If you buy into the article's assertion that you won't get burned or
spaghettified on your way to becoming a nucleon paste, and you want a heavier
BH, the nearest is Sag A* at 4.1e6 SM and 25000 LY away.

Anyway, to travel between the teleporter and Earth, we're talking most of the
resources of a planet to accelerate a mass to substantial fractions of c. Then
you've got thousands of years of collisions, radiation, and maybe
(assumption?) cultural and biological challenges of living in space for aeons,
plus needing another planet's worth of resources to slow down at the
destination. All this makes it hard enough even to get a dozen LY to our
nearest start system.

My opinion is we're in something of a Well World universe, where everyone is
pretty well travel-isolated from their neighbors.

~~~
tachyonbeam
I hear you, but I think colonizing the galaxy might still be feasible. If we
can get to the point where we have the technology to colonize Mars, which will
hopefully happen this century, then I would imagine it probably won't be long
after that until we manage to have permanent space habitats that harvest
materials from asteroids.

If we have fusion power, durable permanent space habitats, and the technology
to harvest materials from asteroids, then traveling to the next star system
doesn't seem so far-fetched anymore. If we could just reach 0.1c, we could
make it to Alpha Centauri in less than 50 years. Once we make it there, if
we're already comfortable living in space, we don't even need to worry about
terraforming or anything lengthy and complicated like that, we can just
harvest asteroids and build more space stations and ships.

Not a physicist, but I see Project Orion could have reached 0.33% of the speed
of light. Would it be realistic to extend that design to accelerate to 0.1c?

~~~
krapp
>If we can get to the point where we have the technology to colonize Mars,
which will hopefully happen this century, then I would imagine it probably
won't be long after that until we manage to have permanent space habitats that
harvest materials from asteroids.

Bear in mind that we were certain colonizing Mars was just around the corner
after landing on the Moon... about 60 years ago. In the interim, we lost the
capability to land anything but probes beyond low earth orbit and are
basically starting from scratch with private enterprise.

Not only is technological progress not always consistent, but it takes more
time and effort to recover from regressions the further along the curve of
advancement you happen to be. By which time, goals and priorities may have
changed significantly to alter the trajectory of that progress.

So I would be wary of extrapolations that make it seem as if progress into
space is like climbing a ladder. It seems more like building a Jenga tower as
you climb it.

~~~
adrianN
A few hundred years is nothing compared to the time the universe had habitable
planets.

~~~
krapp
Civilizations don't operate on the scale of the universe, but on the scale of
whatever constitutes the productive fraction of a single lifetime, and the
influential span of a generation. Politics is more important to the rate of
progress in this regard than physics.

~~~
castis
If one civilization has existed over millions or billions of years it does.

~~~
krapp
A civilization can exist over millions or billions of years and still not
maintain the same culture, or goals from one generation to the next. It's no
different.

~~~
castis
Yes, but it is impossible to prove that civilizations that remain the same
over millennia dont exist.

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Roark66
I'm not quite sure how do we start with a "probability to survive trip to the
event horizon" and end up with a possibility to travel faster than light? What
is that hyperspace the article talks about? How falling down the black hole
would transport the object anywhere spatially?

The only thing such a trip could be used for is to see the end of the
universe. As every object getting near the event horizon experiences the time
slowing down compared with the outside a person on board a ship could probably
see stars going out etc as billions of years passed. The time slows down so
much one could never "pass through" a black hole as reaching the singularity
would require the time to stop. So as the ship approaches the singularity the
black hole would get smaller and smaller as it evaporated during those
billions of years until it eventually disappeared. However, a ship wouldn't
survive the disappearance as when the black hole is getting smaller the tidal
forces increase eventually ripping the ship to shreds.

~~~
mirimir
Yes, TFA says _nothing_ about what happens after surviving the fall. But from
Burko and Khanna (2019) I get this:

> The fate of an astronaut who falls into a black hole depends not just on the
> latter’s properties (such as the intrinsic parameters, i.e., the mass and
> spin angular momentum, and the external perturbation fields) but also on the
> former’s worldline. ... However, astronauts with positive energy and low
> angular momentum (including counterrotating ones) arrive at the outgoing leg
> of the black hole’s inner horizon ("outgoing inner horizon", henceforth,
> OIH).

> The properties of spacetime at the OIH have been proposed to be those of an
> effective shock wave singularity. Specifically, it was proposed in [2] that
> daughters of a family of free-falling astronauts whose geodesics intersect
> with the OIH, and who are separated only by time translations (and labeled
> by the advanced time values at which they cross the event horizon (EH)
> [symbols]) experience a change of order unity in typical metric
> perturbations, and that these changes occur over a lapse of proper time that
> drops like [symbols] with increasing [symbols], where [symbols] is the
> surface gravity of the OIH. Sufficiently late-falling daughters therefore
> experience an effective shock wave singularity, the Marolf-Ori singularity
> ("outflying singularity").

I have no clue what that means. Anyone?

0) Burko and Khanna (2019) The Marolf-Ori singularity inside fast spinning
black holes,
[https://arxiv.org/pdf/1901.03413.pdf](https://arxiv.org/pdf/1901.03413.pdf)

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virgakwolfw
Yes, they might. And then again they might not. Probably not. In fact, there’s
not a snowflakes chance in hell they will. This is the scientific equivalent
of wondering how many angels can dance on the head of a pin. Oh, except now
they have a computer model. Plus ça change, plus c'est la même chose

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vertline3
I'm just confused, I thought a black hole was where gravity was so strong
light could not escape it just starts looping back on itself like a coin in a
large funnel, then how could we escape? We would just spiral down the drain?
Why would there be a portal?

~~~
YayamiOmate
If your drain analogy holds beyond the point of you losing the sightof probe,
the matter that goes into drain does not cease to exists, even if for all your
practical purposes it does. On the contrary, you can be sure it does reappear
somewhere.

Also, it's pretty much certain that wherever there appears infinity in
physical model you can be sure it's a limitation of the model, not actual
physics of the object. We do not observe infiities, even though pretty much
every of our models has some.

Those would be two basic hunches against stuffing matter into infinity without
consequences. Some kind of exit seems natural, the question is how destructive
it would be.

~~~
sliken
If there were an exit to a blackhole, they would stop gaining mass. If that
was true they would all be the same size.

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rhn_mk1
Is it just me, or does the article not attempt to explain what this has to do
with "hyperspace travel"? The only thing new here is that you can plunge into
oblivion without getting torn apart in the process.

~~~
unparagoned
Nope, your not missing anything. The whole hyperspace stuff sounds like
clickbait. You need exotic matter stuff with negative mass/energy stop stop a
wormhole from collapsing, otherwise it would destabilise as soon as a photon
enters it. This article is showing that in theory if you could keep the bridge
open somehow, you could send a ship through. That's a big if

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soneca
My sci-fi plot theory: our universe is what is inside a black hole. The big
bang was the formation of a black hole on another universe pulling matter to
ours.

~~~
colordrops
Isn't that just a mainstream physics theory?

~~~
soneca
Is it? Gotta change my plot now then :)

~~~
db48x
The problem with that plot is that even if it's true, it doesn't change
anything. You can't leave the black hole (because space-time at the edge is
expanding faster than the speed of light), so there's nowhere else to go.

~~~
soneca
There is where the _" -fi"_ part enters (I'm ok with "soft" sci-fi).

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UncleSlacky
This looks a lot like what was proposed back in the 70s by Adrian Berry in his
book "The Iron Sun: Crossing the Universe through black holes":
[https://www.goodreads.com/book/show/1091779.The_Iron_Sun](https://www.goodreads.com/book/show/1091779.The_Iron_Sun)

------
snarfy
I recall reading somewhere the density at the event horizon of the super
massive black hole at the center of our galaxy is about the same as water. The
singularity is supposedly infinite, but the event horizon depends on the size
of the black hole.

~~~
PopePompus
This isn't quite right. If you take the mass of Sgr A* (the black hole in the
center of the galaxy) and divide it by the volume of a sphere (let's ignore
rotation for simplicity) with the radius of the event horizon, you do get a
density value near that of water. But almost all of the mass is concentrated
in or near the singularity. If you ignore the small amount of stuff falling
into Sgr A* at any given moment, the density at the event horizon is 0.

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reagle
A halo drive sends light, instead of people, slingshotting around binary black
holes and harvests the energy (via solar sales) in the blue-shifted life. Much
safer!

------
julius_set
I do wonder though if you travel at the speed of light wouldn't your ship
break apart even if you accidentally hit a tiny rock in space? Maybe even
dust?

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dev_dull
John Titor is that you?

------
beefman
Original source: [https://theconversation.com/rotating-black-holes-may-
serve-a...](https://theconversation.com/rotating-black-holes-may-serve-as-
gentle-portals-for-hyperspace-travel-107062)

~~~
dang
Ok, changed to that from [https://daily.jstor.org/rotating-black-holes-may-
serve-as-ge...](https://daily.jstor.org/rotating-black-holes-may-serve-as-
gentle-portals-for-hyperspace-travel/). Thanks!

------
freedman1611
As much as I love science fiction. In reality, even making it the nearest star
is an impossible feat. Even traveling at the speed of light (which we are not
even sure the human body can handle) it would take 100 years to reach our
nearest star; let alone the nearest black hole. Even whether black holes
exist, and what they really are is hotly debated. I think the idea of
interstellar travel is futile, and we should focus on improving our quality of
life here (free energy i.e. Telsa tech, transporting goods with
electrogravitic vehicles, curing diseases, more scientific agricultural
practices, easing access to education/job skills, etc).

~~~
samplatt
>Even traveling at the speed of light (which we are not even sure the human
body can handle) it would take 100 years to reach our nearest star

Er, no. Travelling at c, it would take 4.5 years to get to our nearest star.
The nearest (known) black hole is V616, 3,000 years of travel away if
travelling @ c.

~~~
OtterCoder
Even better, traveling at c, it would take exactly zero shipboard time. Space
contracts infinitely for the sufficiently fast. Only outside viewers would see
it take 4.5 years.

~~~
sliken
Except that you'd arrive inside a black hole because of relativity's impact on
mass.

