#my cosmology paper is coming along nicely

[cassioxro]

real academia is putting the word “ineffable” into your paper on dark matter to see if anyone gets the reference

[runpogorun]

Gravity

To fill my Marvel Fluff Bingo square, Astronomer AU. No warnings apply, rated G, Matt Murdock/Foggy Nelson, 2759 words. Read it here or over on AO3.

Matt makes his way slowly into the room. The first thing he finds is the couch in the middle, presumably facing the TV, so Matt circles it slowly, his cane tapping lightly between the heavy thud of upholstery on his left and the hollow chink of wooden skirting board. The cane makes a higher tink as it collides with a metal structure and Matt reaches out with his hand, searching, and confirms a metal cabinet. He continues sweeping his cane across the hardwood floor, wary of any rugs, as his hands skate the surface of the cabinet finding photo frames, three clustered plant pots. He sends some loose sheets of paper skating off the surface and freezes, trying to track their direction of flight. 

“Don’t worry about it!” Foggy calls from the kitchen. “I’ll get them.” 

Matt turns his head over his shoulder, towards Foggy, and grins sheepishly. “Sorry. Comes with the territory.”

Foggy tsks quietly. “It’s not a problem. They’re just bills. You said whisky, right?”

Matt nods, “Yes, thanks,” and resumes his exploration. There’s an open doorway just past the cabinet, and Matt pauses, head tilted. “This the bathroom?”

“Yup.”

Matt moves his cane again, and it twangs in his hand with another metal vibration. But this doesn’t feel as heavy as the cabinet. He frowns, and reaches forward as he hears Foggy come up behind him.

“Oh, that’s a little more fragile, but feel free to… feel away.”

Intriguing. Matt stretches through space and finds smooth, painted metal with his fingertips. The metal is curved into a tube, and as his fingers move along it they find an encircling ridge. The object gives under his touch, and he finds the pivot point, the tripod suspending it. He tucks his cane under his arm and takes a step forward, using both hands to get a better idea of its dimensions.

Matt turns his head back in Foggy’s direction. “Is a telescope actually useful in New York City?”

Foggy makes a considering noise. “It’s alright. Not as good as, say, the Socorro Desert. But I can still see things.”

“Does your apartment have roof access?”

“Not the apartment itself, but the super lets me use the service stairs. 

“Nice.”

“Yeah.”

Matt files that away, drops his hands and turns towards Foggy. “Shall we sit?”

“Sure.” Foggy moves towards the couch. “Did you find the couch? It’s over here.” He pats the cushion with an open palm, a firm thump of orienting sound.

Matt smiles at him. “Yes, thanks.” There’s a coffee table as well that Foggy forgot to mention, but he expected that. He folds up his cane and drops it on the coffee table and sits down next to Foggy before accepting his drink. “So, what sort of things do you like to look at? You’re not a creeper, are you?” He takes a sip, revelling as always in the first burn.

Foggy laughs loudly at that. “No. I’m an astronomer.”

Matt tilts his head. “You said you were a teacher.”

“I am. I teach Observational Astronomy and Cosmology at NYU.”

Matt laughs. “And here I was, thinking you were a dance teacher.” Foggy had held the class in his palm, everyone drawn to him, like he had the strongest gravitational pull in the room. It had only taken three classes for Matt to succumb, and accept an invitation for a drink.

“That’s just a hobby. I like to boogie. And it’s a good way to meet people,” Foggy says, nudging Matt with his elbow.  

Matt raises his glass, and Foggy clinks them together. “Slainte. So, do you do this often?” He takes a sip.

“Meet people?”

“Bring strange men back to your apartment.”

Foggy laughs at that. “Strangers are friends we haven’t yet met. But, honestly? No. I don’t.”

Matt considers that. He, in contrast, does do this often, but usually only once or twice with the same person. Matt’s a comet, shooting in and out, plenty of noise and fuss but little substance.

“How about you,” Foggy asks.

“Me?” Matt mentally scans through all the men and women he’s dated in recent history. This may not be the moment to share that information.

“How do you make your crust?”

“Oh.” Matt leans back against the couch cushions and stretches an arm along the seat back, towards Foggy. “I’m a lawyer,” he says, mouth quirking in a slight smile, and waits for the inevitable praise. People are always impressed.

“Oh cool. I nearly did Law,” Foggy says. People often say this - it’s one of those throwaway lines. But then he adds, “I was aiming for Columbia but then… I took an intro to Astronomy class over the summer after high school and I sort of… fell into the stars.”

Matt tilts his head. “Tell me about it.”

Foggy hums, consideringly. “I’d always been interested, you know?” he says. “But I hadn’t really thought that it could be my job. I thought it would be fun to take the class, that it would be interesting. So I did.”

“Always a solid choice, choosing the interesting.”

“It was residential, close to an observatory. One morning we got up in the middle of the night, and towards dawn I saw the Orion Nebula. It’s near Orion’s Belt.  And it was so beautiful, and unknown. I wanted more. I couldn’t stop thinking of what else must be out there. 

“I mean, we do know a lot now, especially when a probe like Juno fires back information, but also a lot of it we can’t exactly know. No one knows what it’s like to stand on the surface of Eros, not really. Or what the Helix Nebula looks like from the inside. We can model it, sure, but we can’t know. I was hungry to find out what I could. I was hooked.” Foggy stops, abruptly, and Matt can hear him sip his drink.

Matt is struck by the emotion in Foggy’s voice, growing with every word. “That’s a great story,” he says. “Not everyone finds their passion, or follows it.

Foggy takes a deep breath, and lets it out slowly. “Yeah. You know, I don’t usually tell people all that, right out of the blocks.”

“I guess I should feel honoured,” Matt says.

“You should, my friend,” Foggy says, the humour back in his voice.

Matt angles his head towards the telescope in the corner. “And that. Do you use it often?”

“Uh yeah, I do, actually.” Matt can hear Foggy shifting against the cushions, like he’s embarrassed again, caught out. “I mean, it’s no match for the Keck telescopes, but it still lets me look. I like looking.”

“Why don’t you show me?” Matt suggests. “I mean, if it’s a good night for it.”

Foggy holds his breath for a moment, then lets out a puff of laughter. “Sure. Why not.” 

It takes a minute to get sorted. Matt snaps out his cane, stashes the whisky bottle under his free arm and holds the glasses in that hand. Foggy is gentle, almost reverent, with the telescope as he folds up the tripod. They head out the apartment door, Foggy and telescope leading, Matt and whisky following, and up the stairwell to the roof. 

The summer air is still warm, but cooler than the oppressive heat of the day. “Over here,” Foggy says. There’s a table and a couple of chairs set up to one side, and Matt settles down to listen as Foggy fusses over the equipment.

“You do do this often.”

“Mmm. It’s nice up here. Quiet.”

Matt listens to the sound of cars rushing in the street below. It’s muffled, sure, and you can’t ever escape cars in New York City. But Foggy’s right. It is peaceful.

“What do you see?”

“There’s still some light in the sky from the sun, but Mars is close and bright. And Venus. Not that I need the telescope for them.”

“You don’t?”

“Not to find them. They’re just like bright stars. But it’s not really dark enough yet. I’ll wait a bit.” The other chair creaks as Foggy sinks into it. “Tell me about your law practice, Matt. Are you a corporate hotshot?”

“Not so much.” Matt shrugs. “It’s just me and my partner Kirsten, and our paralegal Karen. I mostly do what Kirsten says.”

“Partner?”

“Business partner,” Matt says, smiling at Foggy. “Best friend from law school.” 

“What kind of work do you do?”

“Small stuff, mostly. Tenancy disputes, work visas, that kind of thing. Most of our clients come from here in the Kitchen.”

“Sticking up for the little guy!” Foggy cries. “Show me some skin.” Matt holds up his palm and Foggy high fives him. “That’s what I wanted to do.”

“Why didn’t you?”

“Well, like I said, it was the stars. I couldn’t stop thinking about what I’d learned in that in astronomy class. And I’m good at Math, so that helps. I ended up switching from Philosophy to Physics before the year started. And then I went on to get my doctorate at UC Davis. My parents were devastated when they realised I wasn’t going to drive a Bentley” he says, laughing.

Matt laughs with him. “Academia isn’t really a way to make money, is it?”

“It’s really, really not. Not like law. Mom wanted me to be a butcher but that was never going to happen, so at least I could have done something which would have made me rich. Such a disappointment.”

Matt laughs at that. “You sound like me. I’ll never be rich.”

“Your family counting on you for the bucks, too?”

Matt sobers. “Uh, not exactly.” He needs to get off this topic, now. “How far into the galaxy do you usually look?”

“The radiotelescope guys look right back in time, as far as we can look. But I kind of like our neighbourhood - our solar system. Each planet in our solar system is a whole world. Well, obviously they literally are worlds. They’re suspended, hanging in the enormous void of space. They look so serene, from Earth, as they hurtle through the endless blackness, but they’re dynamic and complex. Did you know that the Great Red Spot on Jupiter is so large that two Earths could fit side by side inside it? It’s an enormous storm that’s been raging for at least 150 years, probably much longer.”

Matt shakes his head. “I don’t know much about any of it.”

“We’re all so far from each other, and together at the same time. Once you leave our solar system it’s 25 trillion miles to the next one.”

“The next galaxy?”

“The next solar system. Our galaxy is fifty-two thousand light years across.”

Matt shakes his head. It’s too big a number to make sense.

“We’re bound by gravity to the rest of our solar system. There are so many stars and planets out beyond the Kuiper Belt,” Foggy continues, “And we’ll never be able to reach them. We can’t even see most of what we know is out there, we just have to make an educated guess at it, work it out from the clues.”

Matt half-smiles to himself, and takes a sip of his drink. “Seeing and knowing are two different things.”

“Uh, yeah, of course, I didn’t mean to--” 

Matt cuts him off with the wave of his hand. “So you took the class, and fell in love with astronomy?”

“Oh no, that happened much earlier. Growing up in the city I never saw that many stars, you know? When I was eleven I went away on summer camp to this place upstate. We stayed in these little cabins in the woods by a lake, just outside a small town. It was weird - so quiet, but sometimes you’d hear a wild animal. And at night, the stars! I didn’t know the sky could be like that. Like grains of sand scattered across a velvet blanket. I’d sneak out in the middle of the night when the sky was truly dark, and the entire sky was covered with stars. The trees were only visible as the places where the stars weren’t. 

“I discovered later that Aboriginal people in Australia, who live in the desert where obviously it’s really dark and the sky is very clear, have constellations that are the darker areas between the stars. The reverse of us who live with more light pollution. All people look up at the stars. We all wonder.”

Foggy suddenly sounds like he’s come back to himself, remembered where he was. “I’m sorry, I’m doing all the talking and this is probably really boring.”

“No,” Matt says quietly. “It’s not. I’ve never heard a description like this before. I-” He cuts himself off, unsure how to carry on without making himself sound wistful, and smiles. “I like it. I like listening to your voice.”

Foggy makes a quiet, pleased sound. “That’s a great line. I feel like I should be saying things with gravitas, or beautiful things. She says nothing at all, but simply stares upward into the dark sky and watches, with sad eyes, the slow dance of the infinite stars,” he quotes.

“Now that’s pretty,” Matt says.

“It’s Neil Gaiman. And he’s right, about the stars and planets dancing, caught in each other’s gravity.”

Matt smiles. “So then, tell me,” he prompts, gesturing upwards. “What’s there to see tonight? You said Venus?”

“Let’s see.” Foggy stands and goes again to the telescope. Matt hears the quiet scrape of metal as Foggy adjusts the focus. “There’s Jupiter. It’s high and bright right now. And Venus and Mars.” 

Foggy’s quiet, and Matt considers how far away his focus is. It’s hard for Matt to have a clear impression of anything beyond the reach of his hands - when he’s not touching something it could be anywhere, just out of reach or miles away. But Foggy looks at planets thousands of miles away, places he can never touch but he knows.

“Sometimes it’s better not to use the telescope at all,” Foggy says. “The Leonids meteor shower is going to arrive in a couple of months, and that’s better observed with the naked eye.”

“What are meteor showers like?”

“Fireworks. Bright, white hot stripes painting the sky. Streaking across the heavens.”

“But no boom.” Matt places his empty glass on the small table next to the bottle, and his glasses alongside.

“Good point! And several nights in a row. I’m looking forward to it.” Foggy sounds like he’s turned back to the telescope. 

Matt stands, the whisky now making him loose-limbed and easy, and walks slowly towards Foggy. His hand is slightly extended, reaching for the tune Foggy’s humming under his breath - it’s Drops of Jupiter. He clears his throat. “And what do you see, closer to home?” His voice is low and husky.

Foggy jumps and turns and his arm bumps Matt’s hand. “Oh! Um. Well.” Matt hears him take a quick breath, as Matt brings his hand to rest on Foggy’s shoulder. “I can see at least one beautiful thing.”

“That’s very cheesy,” Matt says, sliding his hand up to Foggy’s neck, then further to cup his cheek. He fans his thumb across to Foggy’s mouth, finding a goatee, and feels Foggy lean in to match him. “But I like it,” he breathes.

Foggy makes a small noise of pleasure for the brief moment that his warm, soft lips are pressed against Matt’s own. Matt brings his other hand to Foggy’s face, sliding both hands back and finding that Foggy’s hair is pulled back into a low pony.

“I didn’t think long hair would be allowed, Professor?” Matt asks.

Foggy huffs a laugh. “It’s Doctor to you, and anything goes these days.” He rests his forehead against Matt’s. “I like you,” he says, breathless.

“Really,” Matt says, one eyebrow lifted.

“I promise I’m usually better at… Words. And things.”

“What sort of things.”

“Oh, I can totally show you. But I feel obligated at this point to tell you that my super has a CCTV camera on this rooftop, and he is probably watching us right now because that’s the kind of guy he is. So, maybe we could take this back downstairs? If I’ve wooed you enough with the stars.”

“I could stand to hear more,” Matt says. “But yes, let’s go inside, and continue the story there.” And Matt follows Foggy again, drawn along by his gravity. He wonders what happens to a comet that gets caught in a gravitational field it can’t escape, wonders if he’s going to find out.

[sybilius]

Stupid (maybe?) question: why astrophysics?

Not a stupid question at all! Though maybe not the answer you want to hear; and certainly one that a year ago would have been a fraught one for me to answer. 

Long post under the cut!

So I mean, all things considered I really did have a nice time in undergraduate. There are a number of factors that plug into that, my NT brain, a fairly privileged upbringing, living in a country where it’s not signing up for years of debt to go pursue higher education. In my third year I decided “all right, it’s time to Decide what I will study in graduate school.” I narrowed it down to fluid dynamics (esp those with good environmental applications) and quantum computing, both of which seemed to have pretty solid career prospects. I took on a summer research term in fluid dynamics, and did my undergraduate thesis in quantum computation.

While both of these had their pros and cons, quantum computation seemed more sexy and exciting, so I lined up to start angling for that. I had my graduate work all planned out -- I was going to go to a school that specialized in that -- which was a small school mind you, not the biggest name ever but had a good program for QC specifically. And I’d attended a summer school there which gave me an in with the folks there. I thought it was a sure thing, I have an excellent resume and research track record, top grades etc etc.

But the problems started to creep up when I realized there wasn’t...anyone specifically I wanted to work with there. Either their work wasn’t the kind of stuff I did for my undergrad thesis, or I’d heard things from other graduate students that made me think “oh, I wouldn’t at all do well under that person”. This caused me to hem and haw a bit -- and that was sort of my mistake there. The school takes people on a supervisory level, so to speak, so if you want to go there, you have to convince a person that they want you working for them. And because I wasn’t really interested in working for anyone specifically...I didn’t do that. And to my surprise, they didn’t accept me. 

My cachet of graduate school acceptances looks fantastic on paper -- I applied to the Big(TM) UK schools (Cambridge, Oxford) and they both accepted me. But ofc there’s a catch there -- those were for course masters programs that transition into research work, ie. they wouldn’t pay me; and I’d be signing up for yet MORE coursework. Added to that, even at a research PhD level, grants for non-UK/EU folks are hard to come by. So I’d basically be signing myself up for an expensive hellscape in a very scary shark tank. Not to mention forcing my local partner to relocate, and offloading a brutal time change on my long distance partner. So though the ego boost was great, those were always off the table. 

Interestingly enough, my rejection from my first choice school came after I’d already accepted the school I’m at now. I accepted this school for a number of reasons; but the strongest of which was there is a professor here who I got along with very well and had met at a conference. Their work was only tangentially related to mine (string theory), but their past graduate student had done a lot of work with string theory and quantum information, so I figured after talking to them that I could give a shot at making my home there.

However, once I GOT to the school and spoke with their graduate student in person, he painted a very depressing picture of what it’s like to work in string theory right now (seriously, talk to any working young string theorist, they’re all disillusioned sad sacks). He spoke highly of my current supervisor; saying that was the person he’d considered most before deciding on string theory (which he thought was a mistake). So I did a 180, looked into a few more people, and then was like “all right, here we go, cosmology now”. 

But of course, as I was learning in first year, though you can kind of sneak quantum computation into string theory research, the leap to cosmology research just...isn’t there. Adding to that, my quantum computations were becoming stressful interpersonally and really adding to my overall imposter syndrome) 

At this same time last summer I applied for a graduate scholarship on an application that included quantum computation as applied to N-body simulations as its pitch (I actually did get the scholarship, incidentally -- I was a runner up and the first place folks, whoever they were, had to turn it down, probably cause they got a better one :) ). 

But that aside, my supervisor took me aside on retreat to that telescope he works with and said “this is a good proposal but I don’t think this is what you should be doing with your thesis and here’s why”. He was kind but clear on why he thought that -- and I thought about it for a week and was like “you know, he’s right. I need to let this quantum computation stuff go”. So I did.

It’s easy to say you could treat this as a “cautionary tale” -- and of course, when applying for graduate school the number one problem is going to be finding a supervisor you like and whose work you like doing. But hindsight being 20/20, I actually wouldn’t change any of those muddles. Quantum computation was a shark-tank hellscape, and I didn’t really realize how much that bothered me until I started hanging out in astronomy spaces. Here the prevailing conversation is “how can we show the public how COOL this shit is” and not “how can I get venture capitalists to invest in my QC startup”. Though I don’t think I’d have ever chosen cosmology, I’m quite happy now that I’ve tripped ass-backwards into it. 

I think the real takeaway from all of this is to be open to many things in graduate school. Most people in science graduate school are very analytic -- we want to make the decisions that lead to the ‘best’ outcome. The truth of the matter is there are a lot of academic study paths for my thesis that would make me happy; and I think going through all that uncertainty that led to where I am now was a more valuable life experience than rolling straight into a supervision situation that was exactly what I planned and expected. 

Also, first year me would be happy! I went into undergraduate thinking I’d be an astrophysicist, and now, here I am!

[shirlleycoyle]

The Universe Is Made of Tiny Bubbles Containing Mini-Universes, Scientists Say

A persistent cosmological puzzle has been troubling physicists since 1917: what is the universe made of?

Complicating this already-mind-boggling question is the fact that our best theories conflict with our observations of the universe. Albert Einstein, according to scientific folklore, felt a unique responsibility for introducing this entire problem, reportedly referring to it as his "biggest blunder."

Essentially, Einstein's novel theory of general relativity didn’t hold up when used to describe the universe as a whole. General relativity described the "geometry" of spacetime as being a trampoline-like surface; planets are heavy bowling balls that distort the surface, creating curves. If a less heavy ball (like a marble) was placed near the bowling ball, it would roll along the surface just like the motion of planets in orbit. Thus, orbits are explained not by a gravitational “force” but by curvature in spacetime.

This proposal worked when considering small regions of spacetime. But when Einstein applied it to the entire universe, its predictions didn't fit. So, Einstein introduced the "cosmological constant," a fixed value that represents a kind of anti-gravity, anti-mass, and anti-energy, counteracting gravity’s effects. But when scientists discovered that the universe was expanding rather than static, as Einstein had believed, the cosmological constant was set to zero and more or less ignored. After we learned that the universe’s expansion is accelerating, however, scientists could no longer conveniently cancel out Einstein’s anti-gravity suggestion.

What was previously assumed to be empty space in the universe now had to be filled with huge amounts of mysterious anti-energy in order to explain observations of the universe’s ever-quickening expansion. Even so, observations of the universe’s expansion suggest that the energy is 60 to 120 orders of magnitude lower than what recent quantum field theory predicts.

What this means is that all of this extra energy is somehow missing when we look at the universe as a whole; either it’s effectively hidden or very different in nature to the energy we do know about.

Today, theoretical physicists are trying to reconcile these mysteries by examining the structure of so-called “spacetime” in the universe at the smallest possible scale, with surprising findings: spacetime might not be the trampoline-like plane scientists once envisioned—it might be a foamy mess of bubbles all containing mini-universes living and dying inside our own.

What is spacetime foam?

To try and solve the mystery of what fills the universe, scientists have been exploring the possibility that it's actually full of bubbles.

In 1955, influential physicist John Wheeler proposed that, at the quantum level, spacetime is not constant but "foamy," made up of ever-changing tiny bubbles. As for what these bubbles are "made" of, recent work suggests that spacetime bubbles are essentially mini-universes briefly forming inside our own.

The spacetime foam proposal fits nicely with the intrinsic uncertainty and indeterminism of the quantum world. Spacetime foam extends quantum uncertainty in particle position and momentum to the very fabric of the universe, so that its geometry is not stable, consistent, or fixed at a tiny scale.

Wheeler illustrated the idea of spacetime foam using an analogy with the surface of the ocean, as retold by theoretical physicist Y. Jack Ng at the University of North Carolina, Chapel Hill, in an email:

Imagine yourself flying a plane over an ocean. At high altitudes the ocean appears smooth. But as you descend, it begins to show roughness. Close enough to the ocean surface, you see bubbles and foam. Analogously, spacetime appears smooth on large scales; but on sufficiently small scales, it will appear rough and foamy.

Professor Steven Carlip at University of California, Davis, published new research in September that builds on Wheeler's quantum foam theory to show that spacetime bubbles could “hide” the cosmological constant at a large scale.

“There are so many different proposals [to solve the cosmological constant problem], and a good sign for my research is that none of them is very widely accepted,” Carlip said in an interview. “I thought it was worth looking for an approach that was less ad hoc, that might come from things we knew or suspected from elsewhere.”

The idea is that in spacetime foam, every point in spacetime has the huge amount of vacuum energy—the lowest energy state equivalent to "empty space"—predicted by quantum theory, but behaves differently to other points. For any particular way in which a point in spacetime is behaving, the exact opposite is equally as likely to occur at another point in spacetime. This is the feature of spacetime foam which “cancels out” the extra energy and expansions at a tiny scale, resulting in the lower energy that we observe at the scale of the whole universe.

For this to work, one has to assume that at the quantum level, time has no intrinsic "direction." In other words, there is no "arrow of time." According to Carlip, in the quantum world, this isn't such a wild suggestion. “Most physicists would agree that we don't know at a fundamental level why there's an arrow of time at all,” he said. “The idea that it's somehow 'emergent' on larger scales has been around for a long time.”

Carlip calls spacetime foam a “complex microscopic structure." It can almost be thought of as an expanding universe formed by tiny expanding and contracting universes at every point in spacetime. Carlip believes it’s possible that over time, the expanding areas of spacetime each replicate the complicated structure, and are themselves filled with tiny universes at every point.

Another paper published in August 2019 explores this scenario more thoroughly. Authors Qingdi Wang and William G. Unruh at the University of British Columbia suggest that every point in spacetime cycles through expansion and contraction, like tiny versions of our universe. Every point in spacetime, they say, is a “microcyclic universe”, endlessly moving from singularity, to a Big Bang, and finally collapse, on repeat.

The tiniest computers in the universe and a theory of everything

Quantum foam is having something of a moment, not just as a solution to the Cosmological Constant Problem, but also to address other enigmas in physics, like black holes, quantum computers, and dark energy.

A forthcoming article by Ng suggests that spacetime foam holds the key to finally unify and explain phenomenon at both a quantum and cosmological scale, moving us towards the elusive Theory of Everything. Such a theory would explain areas of physics which are currently independent, and at times conflicting, under one coherent framework.

Like Carlip, Ng also derives the large value for a positive cosmological constant using a model of spacetime bubbles. But to do so, he treats the "bubbles" in quantum foam as the universe’s tiniest computers, encoding and processing information.

Remember: quantum foam contains bubbles of uncertainty in space and time. To measure how "bubbly" spacetime is, Ng suggests a thought experiment involving clocks clustered in a spherical volume of spacetime which transmit and receive light signals and measure the time it takes for the signals to be received.

“This process of mapping the geometry is a sort of computation, in which distances are gauged by transmitting and processing information," he wrote in his paper.

Using other known relationships between energy and quantum computation, and the limit on mass inside the sphere to avoid forming a black hole, Ng argued that the uncertainty built into the quantum-scale universe that determines how accurately (or inaccurately) we can measure the geometry of spacetime also limits the maximum amount of information these bubble-computers can store and their computing power.

Extending this result for the entire universe rather than an isolated volume of spacetime, Ng shows that spacetime foam is equivalent to dark energy and dark matter, since ordinary matter would not be capable of storing and computing the maximum amount of information he derives from the measurement task.

“The existence of spacetime foam, with the aid of thermodynamic considerations, appears to imply the co-existence of a dark sector (in addition to ordinary matter),” Ng told Motherboard. “This line of research is not common within the physics community, but it makes (physical) sense to me.”

The key takeaway from Ng's work is is: not only can spacetime foam be measured and explored conceptually, but it can also explain the acceleration of the universe by connecting quantum physics, general relativity and dark energy. Ng believes a Theory of Everything is within reach.

“Eventually what I’d like to explore and, more importantly, what I would like to encourage others to explore, is to go beyond the consideration of spacetime foam, and to see whether both quantum mechanics and gravitation are emergent phenomena, and whether thermodynamics (whose protagonist is entropy) holds the key to understand the laws of nature," he said.

The future of foam research

Conceptually, spacetime foam reconciles and explains many of the outstanding problems between quantum physics and cosmology. Still, both Ng and Carlip are calling for more work to be done to truly understand the nature of spacetime.

Carlip is working on a quantitative model of spacetime foam to supplement the theoretical model currently on the table. He’s calling the model “minisuperspace," and is hopeful that physicists researching other approaches in the quantum-cosmology intersection could find examples of the model in their own work, if they know to look for it. To start with, Carlip says he’ll be looking at some numerical simulations to support the foam model.

Going beyond a simple quantitative model will need an all hands on deck approach. “I'd love to have people who are working on various approaches to quantum gravity, string theory, loop quantum gravity, asymptotic safety, etc., look for this kind of phenomenon in their work to see if a connection can be made,” Carlip said.

Ng echoed the desire for more dedicated research which spans boundaries between different areas of theoretical physics. But his hope is even grander: for a unified theory which ties together quantum mechanics, gravity, and thermodynamics to explain the universe's mysteries.

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