A screenshot from the film 'The Cloverfield Paradox' (2018). Source: Netflix

All the science in ‘The Cloverfield Paradox’

I watched The Cloverfield Paradox last night, the horror film that Paramount pictures had dumped with Netflix and which was then released by Netflix on February 4. It’s a dumb production: unlike H.R. Giger’s existential, visceral horrors that I so admire, The Cloverfield Paradox is all about things going bump in the dark. But what sets these things off in the film is quite interesting: a particle accelerator. However, given how bad the film was, the screenwriter seems to have used this device simply as a plot device, nothing else.

The particle accelerator is called Shepard. We don’t know what particles it’s accelerating or up to what centre-of-mass collision energy. However, the film’s premise rests on the possibility that a particle accelerator can open up windows into other dimensions. The Cloverfield Paradox needs this because, according to its story, Earth has run out of energy sources in 2028 and countries are threatening ground invasions for the last of the oil, so scientists assemble a giant particle accelerator in space to tap into energy sources in other dimensions.

Considering 2028 is only a decade from now – when the Sun will still be shining bright as ever in the sky – and renewable sources of energy aren’t even being discussed, the movie segues from sci-fi into fantasy right there.

Anyway, the idea that a particle accelerator can open up ‘portals’ into other dimensions isn’t new nor entirely silly. Broadly, an accelerator’s purpose is founded on three concepts: the special theory of relativity (SR), particle decay and the wavefunction of quantum mechanics.

According to SR, mass and energy can transform into each other as well as that objects moving closer to the speed of light will become more massive, thus more energetic. Particle decay is what happens when a heavier subatomic particle decomposes into groups of lighter particles because it’s unstable. Put these two ideas together and you have a part of the answer: accelerators accelerate particles to extremely high velocities, the particles become more massive, ergo more energetic, and the excess energy condenses out at some point as other particles.

Next, in quantum mechanics, the wavefunction is a mathematical function: when you solve it based on what information you have available, the answer spit out by one kind of the function gives the probability that a particular particle exists at some point in the spacetime continuum. It’s called a wavefunction because the function describes a wave, and like all waves, this one also has a wavelength and an amplitude. However, the wavelength here describes the distance across which the particle will manifest. Because energy is directly proportional to frequency (E = × ν; h is Planck’s constant) and frequency is inversely proportional to the wavelength, energy is inversely proportional to wavelength. So the more the energy a particle accelerator achieves, the smaller the part of spacetime the particles will have a chance of probing.

Spoilers ahead

SR, particle decay and the properties of the wavefunction together imply that if the Shepard is able to achieve a suitably high energy of acceleration, it will be able to touch upon an exceedingly small part of spacetime. But why, as it happens in The Cloverfield Paradox, would this open a window into another universe?

Spoilers end

Instead of directly offering a peek into alternate universes, a very-high-energy particle accelerator could offer a peek into higher dimensions. According to some theories of physics, there are many higher dimensions even though humankind may have access only to four (three of space and one of time). The reason they should even exist is to be able to solve some conundrums that have evaded explanation. For example, according to Kaluza-Klein theory (one of the precursors of string theory), the force of gravity is so much weaker than the other three fundamental forces (strong nuclear, weak nuclear and electromagnetic) because it exists in five dimensions. So when you experience it in just four dimensions, its effects are subdued.

Where are these dimensions? Per string theory, for example, they are extremely compactified, i.e. accessible only over incredibly short distances, because they are thought to be curled up on themselves. According to Oskar Klein (one half of ‘Kaluza-Klein’, the other half being Theodore Kaluza), this region of space could be a circle of radius 10-32 m. That’s 0.00000000000000000000000000000001 m – over five quadrillion times smaller than a proton. According to CERN, which hosts the Large Hadron Collider (LHC), a particle accelerated to 10 TeV can probe a distance of 10-19 m. That’s still one trillion times larger than where the Kaluza-Klein fifth dimension is supposed to be curled up. The LHC has been able to accelerate particles to 8 TeV.

The likelihood of a particle accelerator tossing us into an alternate universe entirely is a different kind of problem. For one, we have no clue where the connections between alternate universes are nor how they can be accessed. In Nolan’s Interstellar (2014), a wormhole is discovered by the protagonist to exist inside a blackhole – a hypothesis we currently don’t have any way of verifying. Moreover, though the LHC is supposed to be able to create microscopic blackholes, they have a 0% chance of growing to possess the size or potential of Interstellar‘s Gargantua.

In all, The Cloverfield Paradox is a waste of time. In the 2016 film Spectral – also released by Netflix – the science is overwrought, stretched beyond its possibilities, but still stays close to the basic principles. For example, the antagonists in Spectral are creatures made entirely as Bose-Einstein condensates. How this was even achieved boggles the mind, but the creatures have the same physical properties that the condensates do. In The Cloverfield Paradox, however, the accelerator is a convenient insertion into a bland story, an abuse of the opportunities that physics of this complexity offers. The writers might as well have said all the characters blinked and found themselves in a different universe.

The journey of a crow and the story of a black hole

The Washington Post has a review, and introduction therewith, of a curious new book called Ka, authored by John Crowley (acclaimed author of Great Work of Time). It is narrated from the POV of a crow named Dar Oakley, who journeys repeatedly into the realm of the dead with a human companion. A para from the WaPo piece caught my attention for its allusion to an unsolved problem in physics:

In many cultures, crows have long been regarded as “death-birds.” Eaters of carrion and corpses, they are sometimes even said to convey the soul into the afterlife. Crowley’s title itself alludes to this notion: Dar Oakley croaks out “ka,” which isn’t just a variant spelling of “caw,” but also the ancient Egyptian word for the spiritual self that survives the decay of the body. Yet what actually remains of us after our bones have been picked clean? Might our spirits then dwell in some Happy Valley or will we suffer in eternal torment? Could death itself be simply an adventure-rich dream from which we never awake? Who knows? The narrator, who might be a writer, says of his dead and much-missed wife Debra that “the ultimate continuation of her is me.” What, however, becomes of Debra when he too is dead?

What indeed. The question is left unanswered so the reader can confront the unanswerability supposedly implicit in this riddle. But while this scheme may be acceptable in a book-length “exploration of the bond between the living and the dead”, physicists don’t have much of a choice. They really want to know, would love to know, how a very similar situation plays out in the quantum realm.

It’s called the black hole information paradox. A black hole is a single point in space around which spacetime is folded into a sphere. This means that if you get trapped in this region of spacetime, you’re locked in. You can’t leave the sphere. The surface of this sphere is called the event horizon: it’s the shortest distance from the black hole from which you can pull away.

Now, there’s no way to tell two black holes apart if their mass, angular momentum and electric charge are the same. This is called the no-hair conjecture. This means that whatever a black hole swallows – whether it be physical matter or information as a sequence of 0s and 1s encoded as an electromagnetic signal – doesn’t retain its original shape or patterns. They become lost, observable only in changes to the black hole’s mass, angular momentum and/or electric charge.

In 1974, Stephen Hawking, Alexei Starobinsky and Yakov Zel’dovich found that, thanks to quantum mechanical effects near an event horizon, the black hole within could be emitting radiation out into space. So assuming a black hole contains a finite amount of energy and has stopped eating material/info from the outside, it will evaporate slowly over time and vanish. This is where the information paradox kicks in.

You’re obviously thinking the info the black hole once swallowed was all converted into energy and emitted as Hawking radiation. This is actually where the problem begins. Quantum mechanics may be whimsically counterintuitive about what it allows nature to do at its smallest scale. But it does have some rules of its own that it always follows. One of them is that information is always conserved, that when information passes into a black hole, it can’t be converted into the same energy mulch that everything else is converted to.

We don’t know what happens to the ‘spirit’ of Debra when Dar Oakley passes away. And we don’t know what happens to the information inside a black hole when the latter evaporates.

Black holes are unique objects of study for classical and non-classical physicists alike because they combine the consequences of both general relativity and quantum mechanics. Those pursuing a unified theory, broadly called quantum gravity, hope that data about black holes will help them find a way to reconcile the laws of nature at the biggest and smallest scales. Resolving the black hole information paradox is one such path.

For example, string theory, which is a technical framework that gives physicists and mathematicians the tools to solve problems in quantum gravity, proposes a way out in the name of the holographic principle. It states (in highly simplified terms) that the information trapped by a black hole is actually trapped along the event horizon and doesn’t fall inside it. Over time, fluctuations on the horizon release the information out. However, neither the complete shape and consequences of this theory nor some contradictory predictions are fully understood.

Even whether humans will be able to resolve this paradox in their lifetime at all remains to be seen – but it’s important to hope that such a thing is possible and that the story of a black hole’s life can be told from start to finish someday. Crowley also tries to answer Dar Oakley’s question about Debra’s fate thus (according to the WaPo review):

“Maybe not, said the Skeleton. But look at it this way. When you return home, you’ll tell the story of how you sought it and failed, and that story will be told and told again. And when you’re dead yourself, the story will go on being told, and in that telling you’ll speak and act and be alive again.”

Caw!

Featured image credit: Free-Photos/pixabay.

Neutron stars

When the hype for the announcement of the previous GW detection was ramping up, I had a feeling LIGO was about to announce the detection of a neutron-star collision. It wasn’t to be – but in my excitement, I’d written a small part of the article. I’m sharing it below. I’d also recommend reading this post: The Secrets of How Planets Form.

Stars die. Sometimes, when that happens, their outer layers explode into space in a supernova. Their inner layers collapse inwards under the gravity of their own weight in a violent rush. If the starstuff can be packed dense enough, the collapse produces a blackhole – a volume of space where the laws of quantum mechanics and relativity break down and the particles of matter are plunged into a monumental identity crisis. However, if the dying star wasn’t heavy enough when it blew up, then the inward rush will create a very, very, very dense object – but not a blackhole: a neutron star.

Neutron stars are the densest objects in the universe that astronomers can observe. The only things we know are denser than them are blackholes.

You’d think observed means ‘saw’, but what is ‘seeing’ but the light – a form of electromagnetic energy – from an event reaching our eyes? We can’t directly ‘see’ blackholes collide because the collision doesn’t release any electromagnetic energy. So astronomers have built a special kind of eyes – called gravitational wave detectors – that can observe ripples of gravitational energy that the collision lets loose.

The Laser Interferometer Gravitational-wave Detector (LIGO) we already know about. Its twin eyes, located in Washington and Louisiana, US, have detected three blackhole-blackhole collisions thus far. Two of the scientists who helped build it are hot favourites to win the Nobel Prize for physics next week. The other set of eyes involved in the last find is Virgo, a detector in Italy.

You’ve been told that blackholes are freaks of nature. Heavy objects bend spacetime around themselves. Blackholes are freaks because they step it up: they fold it. They’re so heavy that when spacetime bends around them, it goes all the way around and becomes a three-dimensional loop. Thus, a blackhole traps one patch of the cosmos around a vanishingly small heart of darkness. Even light, if it comes close enough, becomes trapped in this loop and can never escape. This is why astronomers can’t observe blackholes directly, and use gravitational-wave detectors instead.

But neutron stars they can observe. They’re exactly what their names suggest: a ball of neutrons. And neutrons experience a force of nature called the strong nuclear force, and it can be 100,000 billion billion billion times stronger than gravity. This makes neutron stars extremely dense and altogether incredibly heavy as well. On their surface, a classic can of Coke will weigh 355,000 billion tonnes, a thousand-times heavier than all the humans on Earth combined.

Sometimes, a neutron star is ravaged by a powerful magnetic field. This field focuses charged particles on the neutron star’s surface into a tight beam of radiation shooting off into space. If the orb is also spinning, then this beam of radiation sweeps through space like the light from a lighthouse sweeps over the sea near it. Such neutron stars are called pulsars.

Ironing out an X-ray wrinkle

A version of this post, as written by me, originally appeared in The Copernican science blog on March 1, 2013.

One of the techniques to look for and measure the properties of a black hole is to spot X-rays of specific energies coming from a seemingly localized source. The radiation emanates from heated objects like gas molecules and dust particles in the accretion disc around the black hole that have been compressed and heated to very high temperatures as the black hole prepares to gorge on them.

However, the X-rays are often obscured by gas clouds surrounding the black hole, even at farther distances, and then other objects on the path of its long journey to Earth. And this is a planet whose closest black hole is 246 quadrillion km away. This is why the better telescopes that study X-rays are often in orbit around Earth instead of on the ground to minimize further distortions due to our atmosphere.

NASA’s NuSTAR

One of the most powerful such X-ray telescopes is NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array), and on February 28, the government body released data from the orbiting eye almost a year after it was launched in June 2012. NuSTAR studies higher-energy the sources and properties of higher-energy X-rays in space. In this task, it is also complemented by the ESA’s XMM-Newton space-telescope, which studies lower-energy X-rays.

The latest data concerns the black hole at the centre of the galaxy NGC 1365, which is two million times the mass of our Sun, earning it the title of Supermassive Black Hole (SMBH). Around this black hole is an accretion disc, a swirling vortex of gases, metals, molecules, basically anything unfortunate enough to have come close and subsequently been ripped apart. Out of this, NuSTAR and XMM-Newton zeroed in on the X-ray emissions characteristic of iron.

What the data revealed, as has been the wont of technology these days, is a surprise.

What are signatures for?

Emission signatures are used because we know everything about them and we know what makes each one unique. For instance, knowing the rise and dip of X-ray brightness coming from an object at different temperatures allows us to tell whether the source is iron or something else.

By extension, knowing that the source is iron lets us attribute the signature’s distortions to different causes.

And the NuSTAR data has provided the first experimental proof that iron’s signature’s distortion is not due to gas-obscuration, but due to another model called prograde rotation which attributes the distortion to the black hole’s gravitational pull.

A clearer picture

As scientists undertake a detailed analysis of the NASA data, they will also resolve iron’s signature. This means the plot of its emissions at different temperatures and times will be split up into different “colours” (i.e., frequencies) to see how much each colour has been distorted.

With NuSTAR in the picture, this analysis will assume its most precise avatar yet because the telescope’s ability to track higher-energy X-rays lets it penetrate well enough into the gas clouds around black holes, something that optical telescopes like the one at the Keck Observatory can’t. What’s more, the data will also be complete at the higher-energy levels, earlier left blank because XMM-Newton or NASA’s Chandra couldn’t see in that part of the spectrum.

If the prograde rotation model is conclusively proven after continued analysis and more measurements, then for the first time, scientists will have a precision-measurement tool on their hands to calculated black hole spin.

How? If the X-ray distortions are due to the black hole’s gravitational pull and nothing else, then the rate of its spin should be showing itself as the amount of distortion in the emission signature. The finer details for this can be picked out from the resolved data, and a black hole’s exact spin for the first time be pinned down.

The singularity

NGC 1365 is a spiral galaxy about 60 million light-years in the direction of the constellation Fornax and a prominent member of the much-studied Fornax galaxy cluster. Apart from the black hole, the galaxy hosts other interesting features such as a central bar of gas and dust adjacent to prominent star-forming regions and a type-1a supernova discovered as recently as October 27, 2012.

As we sit here, I can’t help but imagine us peering into our tiny telescopes, picking up on feebly small bits of information, and adding an extra line in our textbooks, but in reality being thrust into an entirely new realm of knowledge, understanding, and awareness.

Now, we know there’s a black hole out there – a veritable freak of nature – spinning as fast as the general theory of relativity will allow!