# Space-time theory may reconcile black hole conundrum

We've come a long way in 13.8 billion years; but despite our impressively extensive understanding of the Universe, there are still a few strings left untied. For one, there is the oft-cited disconnect between general relativity, the physics of the very large, and quantum mechanics, the physics of the very small. Then there is problematic fate of a particle's intrinsic information after it falls into a black hole. Now, a new interpretation of fundamental physics attempts to solve both of these conundrums by making a daring claim: at certain scales, space and time simply do not exist.

Let's start with something that is not in question. Thanks to Einstein's theory of special relativity, we can all agree that the speed of light is constant for all observers. We can also agree that, if you're not a photon, approaching light speed comes with some pretty funky rules – namely, anyone watching you will see your length compress and your watch slow down.

But the slowing of time also occurs near gravitationally potent objects, which are described by general relativity. So if you happen to be sight-seeing in the center of the Milky Way and you make the regrettable decision to get too close to our supermassive black hole's event horizon (more sinisterly known as its point-of-no-return), anyone observing you will also see your watch slow down. In fact, he or she will witness your motion toward the event horizon slow dramatically over an infinite amount of time; that is, from your now-traumatized friend's perspective, you never actually cross the event horizon. You, however, will feel no difference in the progression of time as you fall past this invisible barrier, soon to be spaghettified by the black hole's immense gravity.

So, who is "correct"? Relativity dictates that each observer's point of view is equally valid; but in this situation, you can't both be right. Do you face your demise in the heart of a black hole, or don't you? (Note: This isn't strictly a paradox, but intuitively, it feels a little sticky.)

And there is an additional, bigger problem. A black hole's event horizon is thought to give rise to Hawking radiation, a kind of escaping energy that will eventually lead to both the evaporation of the black hole and the destruction of all of the matter and energy that was once held inside of it. This concept has black hole physicists scratching their heads. Because according to the laws of physics, all of the intrinsic information about a particle or system (namely, the quantum wavefunction) must be conserved. It cannot just disappear.

Why all of these bizarre paradoxes? Because black holes exist in the nebulous space where a singularity meets general relativity – fertile, yet untapped ground for the elusive theory of everything.

Enter two interesting, yet controversial concepts: doubly special relativity and gravity's rainbow.

Just as the speed of light is a universally agreed-upon constant in special relativity, so is the Planck energy in doubly special relativity (DSR). In DSR, this value (1.22 x 10^{19} GeV) is the maximum energy (and thus, the maximum mass) that a particle can have in our Universe.

Two important consequences of DSR's maximum energy value are minimum units of time and space. That is, regardless of whether you are moving or stationary, in empty space or near a black hole, you will agree that classical space breaks down at distances shorter than the Planck length (1.6 x 10^{-35} m) and classical time breaks down at moments briefer than the Planck time (5.4 x 10^{-44} sec).

In other words, spacetime is discrete. It exists in indivisible (albeit vanishingly small) units. Quantum below, classical above. Add general relativity into the picture, and you get the theory of gravity's rainbow.

Physicists Ahmed Farag Ali, Mir Faizal, and Barun Majumder believe that these theories can be used to explain away the aforementioned black hole conundrums – both your controversial spaghettification and the information paradox. How? According to DSR and gravity's rainbow, in regions smaller than 1.6 x 10^{-35} m and at times shorter than 5.4 x 10^{-44} sec… the Universe as we know it simply does not exist.

"In gravity's rainbow, space does not exist below a certain minimum length, and time does not exist below a certain minimum time interval," explained Ali, who, along with Faizal and Majumder, authored a paper on this topic that was published last month. "So, all objects existing in space and occurring at a time do not exist below that length and time interval [which are associated with the Planck scale]."

Luckily for us, every particle we know of, and thus every particle we are made of, is much larger than the Planck length and endures for much longer than the Planck time. So – phew! – you and I and everything we see and know can go on existing. (Just don't probe too deeply.)

The event horizon of a black hole, however, is a different story. After all, the event horizon isn't made of particles. It is pure spacetime. And according to Ali and his colleagues, if you could observe it on extremely short time or distance scales, it would cease to have meaning. It wouldn't be a point-of-no-return at all. In their view, the paradox only arises when you treat spacetime as continuous – without minimum units of length and time.

"As the information paradox depends on the existence of the event horizon, and an event horizon like all objects does not exist below a certain length and time interval, then there is no absolute information paradox in gravity's rainbow. The absence of an effective horizon means that there is nothing absolutely stopping information from going out of the black hole," concluded Ali.

No absolute event horizon, no information paradox.

And what of your spaghettification within the black hole? Again, it depends on the scale at which you choose to analyze your situation. In gravity's rainbow, spacetime is discrete; therefore, the mathematics reveal that both you (the doomed in-faller) and your observer will witness your demise within a finite length of time. But in the current formulation of general relativity, where spacetime is described as continuous, the paradox arises. The in-faller, well, falls in; meanwhile, the observer never sees the in-faller pass the event horizon.

"The most important lesson from this paper is that space and time exist only beyond a certain scale," said Ali. "There is no space and time below that scale. Hence, it is meaningless to define particles, matter, or any object, including black holes, that exist in space and time below that scale. Thus, as long as we keep ourselves confined to the scales at which both space and time exist, we get sensible physical answers. However, when we try to ask questions at length and time intervals that are below the scales at which space and time exist, we end up getting paradoxes and problems."

To recap: if spacetime continues on arbitrarily small scales, the paradoxes remain. If, however, gravity's rainbow is correct and the Planck length and the Planck time are the smallest unit of space and time that fundamentally exist, we're in the clear… at least, mathematically speaking. Unfortunately, the Planck scales are far too tiny for our measly modern particle colliders to probe. So, at least for now, this work provides yet another purely theoretical result.

The paper was published in the January 23 issue of *Europhysics Letters*.

**More information:**"Absence of an Effective Horizon for Black Holes in Gravity's Rainbow."

*Europhys.Lett*. 109 (2015) 20001. DOI: 10.1209/0295-5075/109/20001

**Citation**: Space-time theory may reconcile black hole conundrum (2015, February 9) retrieved 22 April 2019 from https://phys.org/news/2015-02-space-time-theory-black-hole-conundrum.html

## User comments

cantdrive85Neros FiddleGigelBHs as limit cases for a collapsed object can exist. I think that from our perspective ideal BHs do not exist (unless we all fell into one). But BHs that are just forming may well exist and I see no problem in working with the mathematical concept of a black hole.

It is just as saying that current disappears when you unplug a device and short its terminals; in reality current just decreases exponentially forever. After a while it doesn't matter that you still have some electricity there, it is practically zero.

movementiseternalGigelalextheaboveaverageI don't understand why the observer couldn't just no longer be able to observe the in-faller. The concept, and please correct me if I am wrong, of a black hole is that its gravity is so strong, not even light can escape? And that this would occur within a certain distance of the singularity, thus where the term "event horizon" originates.

If the "in-faller" crosses this threshold, discrete or not, would they not just seem to "disappear" to the observer? I may just be too lay to understand the paradox. Could someone help me with that?

MoebiusIf objects slow down near an event horizon, nothing would ever fall in. Is there any observational evidence that nothing is falling into black holes? I thought there was all kinds of evidence stuff is falling in them all the time.

seannelson1969kamcoautomotivetreddieWell like...DUHH! I thought the whole point with the Planck length was that below its value, space and time make no sense and simply do not exist at "smaller" scales. ("smaller" in quotes because there IS no "smaller" below the Planck length). Correct me if I am wrong, but that is news from over 60 years ago?!

LosikmovementiseternalmovementiseternalLosikjerry_bushman_7Now for black holes. First they are not holes. Second physics does not break down near or in them. Black holes are only super dense and massive objects with gravity so great that light cannot escape. Also there is no point of no return. A black hole the mass of 100 suns approaches the SMBH at the center of our galaxy. This smaller black hole would be going very fast, even approaching light speed as it seems to enter into a tight orbit around the SMBH. When the SMBH begins to rip apart the smaller one, matter then leaves the weaker.

RobertKarlStonjekConsider a rod with accelerometers front, centre & rear. The rod is accelerating. Will the front and rear accelerometers read the same? The answer is no, the front will read lower and the rear will read higher than the centre accelerometers.

A light beam coming from the front to the centre will be blue shifted & from the rear will be red shifted.

Same rod, stationary above a massive body, front at the lower altitude. The centre notices that the front accelerometer reads higher and the rear lower, light from the front is red shifted and from the rear is blue shifted.

Now the rod free falls. Acceleration causes front accelerometer to be lower, gravity causes it to be higher, acceleration causes light from the front to be blue shifted, gravity causes it to be red shifted.

In other words, they cancel out completely. All three accelerometers read the same, no blue/red shift, no forces, no spaghettification. Einstein: free fall=floating in space

bbbbwindowsCurrent radio telescope data ( Planck) is validating the concept that electromagnetism, not gravity, may be the driving force in cosmology today. Massive electric currents have been identified coursing through the galaxy as well as their galactic sized magnetic fields. This is what the electric universe models have been predicting for 30 years. Maybe some attention should be paid to this new data instead of all the hand wringing about failed concepts such as black holes. In all likelihood they are dense plasma bodies, from which the galaxy has formed.

movementiseternalmovementiseternalalextheaboveaverageThanks for the explanation. I've spent some time trekking down the "Light Cone" rabbit-hole, and have to admit that I am still confused a bit. The concept itself makes sense; however, now I am a bit confused about the "speed of light is locally constant" concept, but that's another conversation, perhaps.

jerry_bushman_7alextheaboveaverageThe thing I think you are missing is that space is not "just space," as you argue earlier. In relativity, the three spatial dimensions we experience are counted with a fourth, which is time. Space and time are often coupled, and referred to as space-time. Gravity (according to the theories I've spent my morning becoming more familiar with) creates warps in space-time, not just space.

In your arguments, you reject relativity without providing any evidence or data to support your case. Is there any science to support what you are saying?

royrporterjrjerry_bushman_7antialias_physorgDo you have a GPS (car navigation system or on your phone)? Do you know that it would be WILDLY inaccurate if relativistic spacetime effects weren't accounted for? (GPS is accurate to within 5-10 meters. Without accounting for relativistic spacetime effects the positioning would be off by 10km for EVERY DAY of its operation.)

Another thing that you may have observed is the color of gold. Gold SHOULD look like silver, but due to relativistic effects it does not.

You are using the theory of relativity and spacetime distortion every day. I don't know how you can still ask for proof. This isn't even some "in the lab observed" stuff. This is stuff you have at home staring you in the face.

jerry_bushman_7Antialias.....Yes GPS would be off if we didn't account for the bending of light. Everything you say about warping space and or time is explained by gravity effecting light and the time piece.

For the past 4 years I have been putting it out there that there was no big bang and now some physicists are backing me up. Water did not make the lake, it merely filled it

alextheaboveaverageDoesn't mean water could not have created the lake.

http://en.wikiped...bow_lake

Your arguments sound a lot like the conservapedia article on relativity...:

http://www.conser...lativity

...which is, by the way, hilarious. No evidence, no citations, just refuting established science because "it's wrong."

jerry_bushman_7bluehighThe Doctor: People assume that time is a strict progression of cause to effect. But actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly-wobbly timey-wimey... stuff.

alextheaboveaverageInteresting argument. Again, no citations. It really wouldn't be too hard to find science to support your argument if it had any such basis.

You seem to be arguing for a Newtonian definition of gravity, where F = G*(m_1*m_2)/(r^2). Photons are the particles that make up light. If space itself is not warped by the mass of an object, whereby do you suppose gravity can bend light? Gravitational force, as you seem to be claiming is acting on the light and altering it's course, can not act on the mass of photons because they have no mass.

jerry_bushman_7alextheaboveaverageAsking me a question that I just asked you is not an answer. Tell me, how does gravity cause light to "bend."

jerry_bushman_7Calibanjerry,

I think what you are missing here is that the BH isn't gravitationally drawing the light in, it is

--as I understand it-- bending/warping SpaceTime(the medium through which light propagates) into itself.

This is really difficult to conceptualise, but if you take the time to read up on the subject, things start to make sense. Especially important is not to confuse the event horizon with the accretion disk.

Even more stunning to contemplate is that the event horizon itself is a discrete record of everything that has ever fallen into the gravity well of a BH. A giant cd.

Or, more properly, a giant uncertainty/probability-distribution disc, since the Uncertainty Principle dictates that no particle's speed, position, and momentum can be known simultaneously.

jerry_bushman_7CalibanOK, jerry-

That's what I get for trying, then.

If you won't try to see that your understanding of gravitational lensing is flawed,and how this misunderstanding creates further misunderstanding of BHs -and much else besides- then there is little help for you in any case.

This is a science news site, so I'll not bother with further attempts in that regard. If you wish to expose yourself to the inevitable ridicule of your I-know-better postings, then knock yourself out.

jerry_bushman_7Nik_2213{cough} They may not have a *rest* mass, but they have a mass-energy equivalent due motion.

nswanbergLeseaSHREEKANT2ND OPINION: Please refer my comment [dated 24th,Jan'2015] on "space – time"

"it is imaginary thing for mathematical approach & application. The basic thing is DE & its derivatives from which the universe is made. They form an structure called …… from which whole universe is made up of."

for 2ND OPINION: please visit

http://swarajgrou...ely.html

http://swarajgrou...sis.html

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