Beyond Spacetime: Gravitational Waves Might Reveal Extra-Dimensions

gw-ripples
NASA (edit by Ian O’Neill)

We are well and truly on our way to a new kind of astronomy that will use gravitational waves — and not electromagnetic waves (i.e. light) — to “see” a side of the universe that would otherwise be invisible.

From crashing black holes to wobbling neutron stars, these cosmic phenomena generate ripples in spacetime and not necessarily emissions in the electromagnetic spectrum. So when the Laser Interferometer Gravitational-wave Observatory (LIGO) made its first gravitational wave detection in September 2015, the science world became very excited about the reality of “gravitational wave astronomy” and the prospect of detecting some of the most massive collisions that happen in the dark, billions of light-years away.

Like waves rippling over the surface of the ocean, gravitational waves travel through spacetime, a prediction that was made by Albert Einstein over a century ago. And like those ocean waves, gravitational waves might reveal something about the nature of spacetime.

We’re talking extra-dimensions and a new study suggests that gravitational waves may carry an awful lot more information with them beyond the characteristics of what generated them in the first place.

Our 4-D Playing Field

First things first, remember that we interact only with four-dimensional spacetime: three dimensions of space and one dimension of time. This is our playing field; we couldn’t care less whether there are more dimensions out there.

Unless you’re a physicist, that is.

And physicists are having a hard job describing gravity, to put it mildly. This might seem weird considering how essential gravity is for, well, everything. Without gravity, no stars would form, planets wouldn’t coalesce and the cosmos would be an exceedingly boring place. But gravity doesn’t seem to “fit” with the Standard Model of physics. The “recipe” for the universe is perfect, except it’s missing one vital ingredient: Gravity. (It’s as if a perfect cake recipe is missing one crucial ingredient, like flour.)

There’s another weird thing about gravity: Although it’s very important in our universe (yes, there might be more than one universe, but I’ll get to that later), it is actually the weakest of all forces.

But why so weak? This is where string theory comes in.

String theory (and, by extension, superstring theory) predicts that the universe is composed of strings that vibrate at different frequencies. These strings form something like a vast, superfine noodle soup and these strings thread through many dimensions (many more than our four-dimensions) creating all the particles and forces that we know and love.

Now, the possible reason why gravity is so weak when compared with the other fundamental forces could be that gravity is interacting with many more dimensions that are invisible to us 4-D beings. Although string theory is a wonderful mathematical tool to describe this possibility, there is little physical evidence to back up this superfine noodly mess, however.

But as already mentioned, if string theory holds true, it would mean that our universe contains many more dimensions than we regularly experience. (The unifying superstring theory, called “M-theory”, predicts a total of 11 dimensions and may provide the framework that unifies the fundamental forces and could be the diving board that launches us into the vast ocean that is the multiversebut I’ll stop there, I’ve said too much.)

Groovy. But what the heck has this got to do with gravitational waves? As gravitational waves travel through spacetime, they might be imprinted with information about these extra dimensions. Like our wave analogy, as the sea washes over a beach, the frequency of the waves increase as the water becomes shallower — the ocean waves are imprinted with information about how deep the water is. Could gravitational waves washing over (or, more accurately, through) spacetime also create some kind of signature that would reveal the presence of very, very tiny extra-dimensions as predicted by superstring theory?

Possibly, say researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam, Germany.

“Physicists have been looking for extra dimensions at the Large Hadron Collider at CERN but up to now this search has yielded no results,” says Gustavo Lucena Gómez, second author of a new study published in the Journal of Cosmology and Astroparticle Physics. “But gravitational wave detectors might be able to provide experimental evidence.”

Beyond Spacetime?

The researchers suggest that these extra-dimensions might modify the signal of gravitational waves received by detectors like LIGO and leave a very high-frequency “fingerprint.” But as this frequency would be exceedingly high — of the order of 1000 Hz — it’s not conceivable that the current (and near-future) ground-based gravitational wave detectors will be sensitive enough to even hope to detect these frequencies.

However, extra-dimensions might modify the gravitational waves in a different way. As gravitational waves propagate, they stretch and shrink the spacetime they travel through, like this:

gw-waves-wave

The amount of spacetime warping might therefore be detected as more gravitational wave detectors are added to the global network. Currently, LIGO has two operating observing stations (one in Washington and one in Louisiana) and next year, the European Virgo detector will start taking data.

More detectors are planned elsewhere, so it’s possible that we may, one day, use gravitational waves to not only “see” black holes go bump in the night, we might also “see” the extra-dimensions that form the minuscule tapestry of the fabric beyond spacetime. And if we can do this, perhaps we’ll finally understand why gravity is so weak and how it really fits in with the Standard Model of physics.

Want to know more about gravitational waves? Well, here’s an Astroengine YouTube video on the topic:

We’re Really Confused Why Supermassive Black Holes Exist at the Dawn of the Cosmos

eso1229a
ESO

Supermassive black holes can be millions to billions of times the mass of our sun. To grow this big, you’d think these gravitational behemoths would need a lot of time to grow. But you’d be wrong.

When looking back into the dawn of our universe, astronomers can see these monsters pumping out huge quantities of radiation as they consume stellar material. Known as quasars, these objects are the centers of primordial galaxies with supermassive black holes at their hearts.

Now, using the twin W. M. Keck Observatory telescopes on Hawaii, researchers have found three quasars all with billion solar mass supermassive black holes in their cores. This is a puzzle; all three quasars have apparently been active for short periods and exist in an epoch when the universe was less than a billion years old.

Currently, astrophysical models of black hole accretion (basically models of how fast black holes consume matter — likes gas, dust, stars and anything else that might stray too close) woefully overestimate how long it takes for black holes to grow to supermassive proportions. What’s more, by studying the region surrounding these quasars, researchers at the Max Planck Institute for Astronomy (MPIA) in Germany have found that these quasars have been active for less than 100,000 years.

To put it mildly, this makes no sense.

“We don’t understand how these young quasars could have grown the supermassive black holes that power them in such a short time,” said lead author Christina Eilers, a post-doctorate student at MPIA.

Using Keck, the team could take some surprisingly precise measurements of the quasar light, thereby revealing the conditions of the environment surrounding these bright baby galaxies.

discoveryint
MPIA

Models predict that after forming, quasars began funneling huge quantities of matter into the central black holes. In the early universe, there was a lot of matter in these baby galaxies, so the matter was rapidly consumed. This created superheated accretion disks that throbbed with powerful radiation. The radiation blew away a comparatively empty region surrounding the quasar called a “proximity zone.” The larger the proximity zone, the longer the quasar had been active and therefore the size of this zone can be used to gauge the age (and therefore mass) of the black hole.

But the proximity zones measured around these quasars revealed activity spanning less than 100,000 years. This is a heartbeat in cosmic time and nowhere near enough time for a black hole pack on the supermassive pounds.

“No current theoretical models can explain the existence of these objects,” said Joseph Hennawi, who led the MPIA team. “The discovery of these young objects challenges the existing theories of black hole formation and will require new models to better understand how black holes and galaxies formed.”

The researchers now hope to track down more of these ancient quasars and measure their proximity zones in case these three objects are a fluke. But this latest twist in the nature of supermassive black holes has only added to the mystery of how they grow to be so big and how they relate to their host galaxies.

Supermassive black hole with torn-apart star (artist’s impress
A supermassive black hole consumes a star in this artist’s impression (ESO)

These questions will undoubtedly reach fever-pitch later this year when the Event Horizon Telescope (EHT) releases the first radio images of the 4 million solar mass black hole lurking at the center of our galaxy. Although it’s a relative light-weight among supermassives, direct observations of Sagittarius A* may uncover some surprises as well as confirm astrophysical models.

But as for how supermassive black holes can possibly exist at the dawn of our universe, we’re obviously missing something — a fact that is as exciting as it is confounding.

We Are The 4.9%

The AMS attached to the space station's exterior (NASA)
The AMS attached to the space station’s exterior (NASA)

This month is Global Astronomy Month (GAM2013) organized by my friends Astronomers Without Borders (AWB). There is a whole host of events going on right this moment to boost astronomy throughout the international community, and as a part of GAM2013, AWB are hosting daily blogs from guest astronomers, writers, physicists and others with a background in space. Today (April 11) was my turn, so I wrote a blog about the fascinating first results to be announced on the International Space Station instrument the Alpha Magnetic Spectrometer — or AMS for short.

Although the AMS’ most recent findings suggest positrons with a signature energy indicative of the annihilation of dark matter — particularly hypothetical weakly interaction massive particles (WIMPS) — it isn’t final proof of dark matter (despite what the tabloid press might’ve told you). But still, it’s exciting and another component of our enduring search for 95.1% of the mass-energy of the universe that is locked in the mysterious and perplexing dark matter and dark energy.

You can read my blog on the AWB website: “Dark Matter: We Are The 4.9%

After Historic Discovery, Higgs Flies Economy

Real superstars: Peter Higgs congratulates ATLAS experiment spokesperson Fabiola Gianotti after she announced her collaboration's discovery of a Higgs-like particle (CERN/ATLAS/Getty)
Real superstars: Peter Higgs congratulates ATLAS experiment spokesperson Fabiola Gianotti after she announced her collaboration’s discovery of a Higgs-like particle. Credit: CERN/ATLAS/Getty

I am endlessly baffled by modern society.

We have reality TV stars whose only talent is to shock and annoy, and yet inexplicably have millions of adoring fans. We also have sports superstars who get paid tens of millions of dollars to play a game they love, and yet they still get elevated to God-like status.

And then there’s Professor Peter Higgs, arguably the biggest science superstar of recent years.

The 83-year-old retired theoretical physicist was one of six scientists who, in the 1960s, assembled the framework behind the Higgs boson — the almost-unequivocally-discovered gauge particle that is theorized to carry the Higgs field, thereby endowing matter with mass. The theory behind the Higgs boson and all the high-energy physics experiments pursuing its existence culminated in a grand CERN announcement from Geneva, Switzerland, on Wednesday. With obvious emotion and nerves, lead scientist of the Large Hadron Collider’s CMS detector Joe Incandela announced what we’ve all been impatiently waiting for: “We have observed a new boson.

So, we now have evidence for the existence of the Higgs boson — or a Higgs boson — to a high degree of statistical certainty, ultimately providing observational evidence for a critical piece of the Standard Model. This story began half a century ago with Prof. Higgs’ theoretical team, and it culminated on July 4, 2012, when results from a $10 billion particle accelerator were announced.

After the historic events of the last few days, one would think Peter Higgs would have been at least treated to a First Class flight back to his home in Scotland. But true to form, Higgs had other ideas:

Later, Higgs’s friend and colleague Alan Walker recounted the low-key celebration they held after learning of the breakthrough, one of the most important scientific discoveries of recent years.

Walker said he and Higgs were flying home from CERN in Geneva this week on budget airline easyJet when he offered Higgs a glass of Prosecco sparkling wine so they could toast the discovery.

Higgs replied: “‘I’d rather have a beer’ and popped a can of London Pride,” Walker said.

via Discovery News

In a world where “celebrities” are hailed as superhuman, to hear that potential Nobel Prize candidate Peter Higgs took a budget airline home, after history had been made, typifies the humble nature of a great scientist and puts the world of celebrity to shame. Money and fame matters little to the people who are unraveling the fabric of the Universe.

On a different (yet related) note, Motherboard interviewed people on the streets of Brooklyn and asked them if they knew what the Higgs boson is. Most had never heard of it, let alone understood it (which, let’s face it, isn’t a surprise — many science communicators still have problems explaining the Higgs mechanism). But I wonder if the same group of people were asked if they knew what a “Snookie” was; I’m guessing they’d have no problem answering.

People may not read the news, but they sure have an innate knowledge of who’s in the gossip columns.

The UK’s Brain Drain (been there, done that)

Professor-Stephen-Hawking-001

Back in 2006, I remember sitting in my local UK Job Centre finding out how I could claim for unemployment benefits.

I can see it now, the moment I explained to my liaison officer that I had been looking for work but received little interest. She looked at me and said, candidly, “Have you thought about not mentioning you have a PhD? It might help.” She smiled.

What? I now need to hide my qualifications if I want to get a job? Isn’t that a little counter-intuitive? Actually, as it turned out, she was right. Many of the jobs I had applied for didn’t require a postdoc to do them; why would a company hire me when they can hire a younger postgrad with lower salary expectations?

Up until that moment, I was still hopeful that I might be able to land an academic position; possibly back in my coronal physics roots, but funding was tight, and I hadn’t done enough networking during my PhD to find a position (I had been too busy scoping out the parties and free booze at the conference dinners).

So there I was, with all the qualifications in the world with no career prospects and a liaison officer who deemed it necessary to advise me to forget the last four years of my academic career. It was a low point in my life, especially as only a few months earlier I had been enjoying one of the highest points in my life: graduating as a doctor in Solar Physics.

Fortunately for me, I had another option. My girlfriend (now lovely wife) was living in the US, and although searching for a job in the UK was a priority for us (we were planning on living in the UK at the time), I knew I could try my luck in the US as well. So after a few months of searching, I cancelled my Job Centre subscription and moved to the other side of the Atlantic.

I had just become a part of the UK’s “brain drain” statistic. I had qualifications, but I was in a weird grey area where companies thought I was over-qualified and funds were in short supply for me to return to academic research.

A lot has happened since those uncertain postdoc times, and although I tried (and failed) to pick up my academic career in solar physics in the US (it turns out that even the sunny state of California suffers from a lack of solar physics funding), the job climate was different. Suddenly, having a PhD was a good thing and the world was my oyster again.

To cut a long story short, I’m happily married, we own five rabbits (don’t ask), we live just north or Los Angeles and I have a dream job with Discovery Channel, as a space producer for Discovery News.

Although I’d like to think that if I was currently living in the UK, I might have landed an equivalent career, I somehow doubt I would be as happy as I am right now with how my academic qualifications helped me get to where I am today.

Why am I bringing this up now? Having just read about Stephen Hawking stepping down as Lucasian professor of Mathematics at Cambridge University and the Guardian’s report about the risk of losing British thinkers overseas, I wonder if employment opportunities have improved since 2006. What’s most worrying is that there appears to be this emphasis on making money as quickly as possible, rather than pursuing academic subjects. However, in my experience, having a PhD doesn’t mean you can even land a job in industry, you might be over-qualified.

Giving up on that tradition of deep intellectual discovery in favour of immediate economic benefit is a huge mistake. You lose the gem of creative, insightful, long-term thinking. That is what Britain has done so spectacularly in the past, and to give that up is a tragedy.” —Neil Turok

A special thanks to Brian Cox, who tweeted the inspiration to this post.