# Scientists find a new way to see inside black holes

Scientists at Towson University and the Johns Hopkins University are reporting a new way to peer through the event horizons around black holes and visualize what lies beneath. Their results could rewrite conventional ideas about the internal structure of spinning black holes. Current approaches use special coordinate systems in which this structure appears quite simple, but quantities that depend on an observer's choice of coordinates can give a distorted view of reality, as anyone knows who has compared the size of Greenland and the USA on a map.

The new approach focuses exclusively on mathematical quantities known as invariants, which have the same value for any choice of coordinates. Expressed in terms of these quantities, black hole interiors reveal a much more intricate and complicated structure than usually thought, with wild variations in curvature from place to place.

These new findings are timely for two reasons, according to Towson University's Kielan Wilcomb, who presented the team's results yesterday at the 228th meeting of the American Astronomical Society in San Diego. First, 2016 is the centennial year of the publication of the theory that first predicted the existence of black holes: Einstein's general theory of relativity. Second, the existence of these objects is no longer a matter of theory, but observational fact. Last September astronomers at the LIGO gravitational-wave observatory detected the first ripples in spacetime from a collision between giant black holes in a distant galaxy.

But while we now know they exist, we will never be able to look inside them, notes team member James Overduin, also of Towson University, since no information can emerge from beyond a black hole's event horizon. Their interiors are, by definition, places that can only be explored mathematically. The new results are thus important in a unique sense. Scientists usually observe first, and then attempt to classify and understand their observations using theory. With black holes this usual course of discovery is reversed: we have a satisfactory theory, but are still groping for the best way to visualize it.

The physical significance of the curvature invariants calculated by Wilcomb, Overduin and Richard C. Henry of the Johns Hopkins University is not yet clear. For the most general black holes (those with mass, spin and electric charge) there are seventeen of these quantities altogether, but they can be related to each other mathematically so that only five are truly independent. Explicit mathematical expressions for some are presented here for the first time. The simplest, known as the Ricci scalar, lies at the heart of general relativity theory. Another, the Weyl invariant, plays an analogous role in one of the few serious alternatives to Einstein's theory, known as conformal gravity. For black holes with no electric charge (as expected for the vast majority of real, astrophysical black holes, since they will tend to neutralize themselves with time) this invariant is equivalent to another quantity known as the Kretschmann scalar.

The team's results confirm that the wild fluctuations in the value of this quantity near the singularity inside a spinning black hole include regions of negative curvature, which are associated physically with a phenomenon known as gravitomagnetism (the gravitational analog of ordinary magnetism). Gravitomagnetic fields, fed by rotational energy, are believed to be responsible for generating the tremendous jets which emanate from the poles of supermassive black holes at the centers of some galaxies. A clearer map of curvature inside the horizon, Henry emphasizes, could enable astronomers to understand why such jets exist in some galaxies and not others (including our own).

Explore further

**More information:**"A New Way to See Inside Black Holes," R. C. Henry, J. M. Overduin & K. Wilcomb, 2015, Bridges Baltimore 2015: Mathematics, Music, Art, Architecture, Culture (Phoenix, AZ: Tessellations Publishing, 2015) and presented at the 228th meeting of the American Astronomical Society in San Diego, Calif. aas.org/meetings/aas228,

*Arxiv*: arxiv.org/abs/1512.02762

**Citation**: Scientists find a new way to see inside black holes (2016, June 15) retrieved 21 May 2019 from https://phys.org/news/2016-06-scientists-black-holes.html

## User comments

HeloMeneloantialias_physorgDa Schneib[contd]

Da SchneibSimilarly, gravitoelectromagnetism is being slowly integrated into gravity physics, which was inevitable from the POV of anyone who is aware that magnetism is the relativistic correction for the action of the electric field; gravity must inevitably have such a correction as well since it propagates at finite speed, and therefore there must be gravitomagnetic effects analogous to the magnetic effects in Maxwell field theory. Gravity Probe B actually measured two of these effects, geodetic and frame-dragging precession. http://apod.nasa....510.html

Gravitomagnetism is, BTW, an important part of the explanation for the "jets" seen around supermassive black holes driving quasars. This is often misunderstood in popular science articles regarding these jets; they are not purely EM phenomena due to the charges in the plasma, but also due to the effects of geodetic and frame dragging precession on particles in the ergosphere of the black hole.

Da SchneibChris_ReeveBenni.........oh just great, now information (photons) is lost not only at the BH surface but also at the so-called Event Horizon. It used to be that only particles lost escape velocity upon entering the Event Horizon, but now they are claiming so also do photons lose Escape Velocity in that area. Or.......does this Author think the EH & BH Surface are the same thing? No wonder Einstein was astute in debunking the BH process.

BenniYou come here wanting the gullible to believe you are some kind of New Age Pop-Sci genius, but you can't even point to the section of Einstein's General Relativity that supposedly predicts the existence of Black Holes. So what's the Title of the section of GR prediction for the existence of BHs?

Copy & Paste for us the first few lead-in sentences in General Relativity so we can know exactly where to start reading all about BHs within GR. Maybe you think it's the Photon Deflection section? I've studied it, nothing about infinite BH gravity wells there. So where is it?

Da SchneibWe can figure out the math, apparently it's you who can't. Stop projecting.

Da SchneibDa SchneibGRT isn't solutions; it's equations. Not to mention for someone who claims to know what DEs are it's kinda revealing to fail to understand the difference.

You just showed you don't even know what GRT is in the first place, so this is just playgrounding.

Da Schneib[contd]

Da SchneibAnother more interesting dodge is to enter the ergosphere outside the technical event horizon. Since most astronomical BHs (particularly stellar ones) must have spin, this is a definite possibility; all spinning BHs have an ergosphere.

I agree. Fun speculation; thanks!

Benni......the author disagrees with you, he states GR predicts the existence of BHs. Are you smarter than the Author?

OK Schneibo, then Copy & Paste the equations that the Author claims predicts BHs.

.......well then, let's just see if you can recognize enough of those DEs to point us to those "equations" in the Photon Deflection section of GR by which you & the author claims Einstein did the "equations" to predict the existence of BHs.

Da SchneibI already told you that it's a solution to GRT that predicts BHs. You brought up a semantic quibble about terminology in a pop science article and I've dealt with that as well. To top it all off you know perfectly well that Schwarzchild found the solution, so there's nowhere in the EFE to find it. You're just playgrounding. It's a sorry thing to see a grown human do.

There isn't any "Photon Deflection section of GR." Now you're just making stuff up.

antialias_physorgSorta. If we look at gravity as warping of space then two sources opposite a 'probe' will nullify. But a source and an anti-source on the same side of the probe would also nullify. As you point out if one of the sources (or the anti-source) is much closer than the other source then it can be weaker and still lead to local zero gravity for the 'probe'.

An anti-source requires negative energy* (though currently we can't create that without having more of the regular kind close by...so not yet usable for the effect on a macroscopic scale..and alos nowhere near the required amount. But if one could separate the two components spatially there may be a way to have a local antigravity field at the expense of another, local positive gravity field nearby)

*

https://bruceleee...-to-lab/

(see section "Generating Negative Energy in Lab"...particularly squeezed states)

Da SchneibPlease sign in to add a comment. Registration is free, and takes less than a minute. Read more