How small do black holes get? Could you carry one around in your pocket? Does that even like a sane thing to do?
I’m pleased to announce that the Large Hadron Collider, the enormous particle accelerator in Europe has begun operations again with twice the colliding power. Smashing atoms with 15 Tera-electron volts.
The LHC double-down has a laundry list of science to get done, like determining the nature of dark matter, searching for particles to confirm the theory of supersymmetry, and probing the Universe for extra dimensions. One of its tasks will be to search for Hawking Radiation, the stream of particles that come out of black holes as they evaporate.
So, in order to watch them evaporate, the LHC is going to try and create little tiny black holes. We only know one natural process for creating black holes: the death of massive stars as supernova. Oh, and whatever it took to make supermassive black holes – that’s still pretty much a mystery.
As a side note, we are going to be supermassively embarrassed if it turns out they’re created by species messing with forces far beyond their comprehension by doubling the power at their biggest particle accelerator, and turning their region of the Universe into a giant mess. Clean up, aisle Milky Way.
Apparently, you could get a black hole of any size, even microscopic. If you took the mass of the Earth, compressed it down to the size of a marble, it would become a black hole. A black hole with the mass of the Earth.
The only place this might have been possible was at the very beginning of the Universe, shortly after the Big Bang. When the Universe was unimaginably hot and dense, there were tiny fluctuations of density, nooks in spacetime where tiny black holes might have formed. Maybe they don’t exist at all, the conditions of the early Universe didn’t bring them about. It’s just a theory. A theory that the Large Hadron Collider will try to confirm or deny.
Artist illustration of a black hole. Image credit: NASA
The important question is, will it kill us all? Could a black hole fall out of the experiment, and roll down into the sewer drain. Chewing its way down into the center of the Earth, gobbling away the core of the planet, eventually creating an Earth-massed black hole?
Here’s the good news. The less massive, the hotter it is, and the faster it evaporates. Microscopic black holes would evaporate in a faction of a second. Any that the LHC could create, would disintegrate in a faction of a second. In fact, they should be gone in 10^-27 seconds.
So it turns out, you could put a black hole in your pocket. An Earth-mass black hole would fit nicely in your pocket. An Earth’s worth of gravity, however, could prove problematic.
Fortunately, there’s no natural process that can create these objects, and any black holes that we could create would be gone before you could get them anywhere near a pocket. So, you should probably stop thinking of it in terms of one of Lord Nibbler’s doodies.
What would you do with a pocket-sized black hole? Tell us in the comments below.
It seems like the good times will go on forever, so feel free to keep on wasting energy. But entropy is patient, and eventually, it’ll make sure there’s no usable energy left in the Universe.
Thanks to the donations of generations of dinosaurs and their plant buddies, we’ve got fossils to burn. If we ever get off our dependence on those kinds of fuels, we’ll take advantage of renewable resources, like solar, wind, tidal, smug and geothermal. And if the physicists really deliver the goods, we’ll harness the power of the Sun and generate a nigh unlimited amount of fusion energy using the abundant hydrogen in all the oceans of the world. Fire up that replicator, the raktajino is on the house. Also, everything is now made of diamonds.
We’ll never run out of H+. Heck that stuff is already cluttering up our daily experience. 75% of the baryonic mass of the Universe is our little one-protoned friend. Closely followed up by helium and lithium, which we’ll gladly burn in our futuristic fusion reactors. Make no mistake, it’s all goin’ in.
It looks like the good times will never end. If we’ve energy to burn, we’ll never be able to contain our urges. Escalating off into more bizarre uses. Kilimajaro-sized ocean cruise liners catering to our most indulgent fantasies, colossal megastructure orbital laser casinos where life is cheap in the arena of sport. We’ll build bigger boards and bigger nails.or something absolutely ridiculous and decadent like artificial ski-hills in Dubai. Sadly, it’s naive to think it’s forever. Someday, quietly, those good times will end. Not soon, but in the distant distant future, all energy in the Universe will have been spent, and there won’t a spare electron to power a single LED.
Astronomers have thought long and hard about the distant future of the Universe. Once the main sequence stars have used up their hydrogen and become cold white dwarfs and even the dimmest red dwarfs have burned off their hydrogen. When the galaxies themselves can no longer make stars. After all the matter in the Universe is absorbed by black holes, or has cooled to the background temperature of the Universe.
Artist’s impression of a Star feeding a black hole. Credit: ESO/L. Calçada
Black holes themselves will evaporate, disappearing slowly over the eons until they all become pure energy. Even the last proton of matter will decay into energy and dissipate. Well, maybe. Actually, physicists aren’t really sure about that yet. Free Nobel prize if you can prove it. Just saying.
And all this time, the Universe has been expanding, spreading matter and energy apart. The mysterious dark energy has been causing the expansion of the Universe to accelerate, pushing material apart until single photons will stretch across light years of distance. This is entropy, the tendency for energy to be evenly distributed. Once everything, and I do mean all things, are the same temperature you’ve hit maximum entropy, where no further work can be done.
This is known as the heat death of the Universe. The temperature of the entire Universe will be an infinitesimal fraction of a degree above Absolute Zero. Right above the place where no further energy can be extracted from an atom and no work can be done. Terrifyingly, our Universe will be out of usable energy.
The white dwarf G29-38 (NASA)
Interestingly, there’ll still be the same amount it started with, but it’ll be evenly distributed across all places, everywhere. This won’t happen any time soon. It’ll take trillions of years before the last stars die, and an incomprehensible amount of time before black holes evaporate. We also don’t even know if protons will actually decay at all. But heat death is our inevitable future.
There’s a glimmer of good news. The entire Universe might drop down to a new energy state. If we wait long enough, the Universe might spontaneously generate a new version of itself through quantum fluctuations. So with an infinite amount of time, who knows what might happen?
Burn up those dirty dinosaurs while you can! Enjoy the light from the Sun, and the sweet whirring power from your counter-top Mr. Fusion reactor. Your distant descendants will be jealous of your wasteful use of energy, non-smothering climate and access to coffee and chocolate, as they huddle around the fading heat from the last black holes, hoping for a new universe to appear.
What’s the most extreme use of energy you can imagine? Tell us in the comments below.
Special Guest: Astronaut Ron Garan (orbitalpersepctive.com / @Astro_Ron)
Ron will talk about his new book The Orbital Perspective: Lessons in Seeing the Big Picture from a Journey of 71 Million Miles.
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
You can join in the discussion between episodes over at our Weekly Space Hangout Crew group in G+, and suggest your ideas for stories we can discuss each week!
This artist’s impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783 in the southern constellation of Centaurus (The Centaur). Credit: ESO/M. Kornmesser
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.
Dr. Stephen Hawking of Cambridge University alongside illustrations of a black hole and an event horizon with Hawking Radiation. He continues to engage his grey matter to uncover the secrets of the Universe while others attempt to confirm his existing theories. (Photo: BBC, Illus.: T.Reyes)
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 1019 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.
“Say what??” -Albert Einstein
“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. A pre-print of the paper is available here.
When a star encounters a black hole, tidal forces stretch the star into an elongated blob before tearing it apart, as seen in these images from a computer simulation by James Guillochon of Harvard University.
A telescope peers into the blackness of deep space. Suddenly – a brilliant flash of light appears that wasn’t there before. What could it be? A supernova? Two massively dense stars fusing together? Perhaps a gamma ray burst?
Five years ago, researchers using the ROTSE IIIb telescope at McDonald Observatory noticed just such an event. But far from being your run-of-the-mill stellar explosion or neutron star merger, the astronomers believe that this tiny flare was, in fact, evidence of a supermassive black hole at the center of a distant galaxy, tearing a star to shreds.
Astronomers at McDonald had been using the telescope to scan the skies for such nascent flashes for years, as part of the ROTSE Supernova Verification Project (SNVP). And at first blush, the event seen in early 2009, which the researches nicknamed “Dougie,” looked just like many of the other supernovae they had discovered over the course of the project. With a blazing – 22.5-magnitude absolute brightness, the event fit squarely within the class of superluminous supernovae that the researchers were already familiar with.
But as time went on and more data on Dougie rolled in, the astronomers began to change their minds. X-ray observations made by the orbiting Swift satellite and optical spectra taken by McDonald’s Hobby-Eberly Telescope revealed an evolving light curve and chemical makeup that didn’t fit with computer simulations of superluminous supernovae. Likewise, Dougie didn’t appear to be a neutron star merger, which would have reached peak luminosity far more quickly than was observed, or a gamma ray burst, which, even at an angle, would have appeared far brighter in x-ray light.
That left only one option: a so-called “tidal disruption event,” or the carnage and spaghettification that occurs when a star wanders too close to a black hole’s horizon. J. Craig Wheeler, head of the supernova group at The University of Texas at Austin and a member of the team that discovered Dougie, explained that at short distances, a black hole’s gravity exerts a much stronger pull on the side of the star nearest to it than it does on the star’s opposite side. He explained, “These especially large tides can be strong enough that you pull the star out into a noodle.”
The team refined their models of the event and came to a surprising conclusion: having drawn in Dougie’s stellar material a bit faster than it could handle, the black hole was now “choking” on its latest meal. This is due to an astrophysical principle called the Eddington Limit, which states that a black hole of a given size can only handle so much infalling material. After this limit has been reached, any additional intake of matter exerts more outward pressure than the black hole’s gravity can compensate for. This pressure increase has a kind of rebound effect, throwing off material from the black hole’s accretion disk along with heat and light. Such a burst of energy accounts for at least part of Dougie’s brightness, but also indicates that the original dying star – a star not unlike our own Sun – wasn’t going down without a fight.
Combining these observations with the mathematics of the Eddington Limit, the researchers estimated the black hole’s size to be about 1 million solar masses – a rather small black hole, at the center of a rather small galaxy, three billion light years away. Discoveries like these not only allow astronomers to better understand the physics of black holes, but also properties of their often unassuming home galaxies. After all, mused Wheeler, “Who knew this little guy had a black hole?”
To get a simulated glimpse of Dougie for yourself, check out the amazing animation below, courtesy of team member James Guillochon:
The research is published in this month’s issue of The Astrophysical Journal. A pre-print of the paper is available here.
An artists illustration of the central engine of a Quasar. These "Quasi-stellar Objects" QSOs are now recognized as the super massive black holes at the center of emerging galaxies in the early Universe. (Photo Credit: NASA)
Imagine matter packed so densely that nothing can escape. Not a moon, not a planet and not even light. That’s what black holes are — a spot where gravity’s pull is huge, ending up being dangerous for anything that accidentally strays by. But how did black holes come to be, and why are they important? Below we have 10 facts about black holes — just a few tidbits about these fascinating objects.
Fact 1: You can’t directly see a black hole.
Because a black hole is indeed “black” — no light can escape from it — it’s impossible for us to sense the hole directly through our instruments, no matter what kind of electromagnetic radiation you use (light, X-rays, whatever.) The key is to look at the hole’s effects on the nearby environment, points out NASA. Say a star happens to get too close to the black hole, for example. The black hole naturally pulls on the star and rips it to shreds. When the matter from the star begins to bleed toward the black hole, it gets faster, gets hotter and glows brightly in X-rays.
Fact 2: Look out! Our Milky Way likely has a black hole.
A natural next question is given how dangerous a black hole is, is Earth in any imminent danger of getting swallowed? The answer is no, astronomers say, although there is probably a huge supermassive black hole lurking in the middle of our galaxy. Luckily, we’re nowhere near this monster — we are about two-thirds of the way out from the center, relative to the rest of our galaxy — but we can certainly observe its effects from afar. For example: the European Space Agency says it’s four million times more massive than our Sun, and that it’s surrounded by surprisingly hot gas.
Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI
Fact 3: Dying stars create stellar black holes.
Say you have a star that’s about 20 times more massive than the Sun. Our Sun is going to end its life quietly; when its nuclear fuel burns out, it’ll slowly fade into a white dwarf. That’s not the case for far more massive stars. When those monsters run out of fuel, gravity will overwhelm the natural pressure the star maintains to keep its shape stable. When the pressure from nuclear reactions collapses, according to the Space Telescope Science Institute, gravity violently overwhelms and collapses the core and other layers are flung into space. This is called a supernova. The remaining core collapses into a singularity — a spot of infinite density and almost no volume. That’s another name for a black hole.
Fact 4: Black holes come in a range of sizes.
There are at least three types of black holes, NASA says, ranging from relative squeakers to those that dominate a galaxy’s center. Primordial black holes are the smallest kinds, and range in size from one atom’s size to a mountain’s mass. Stellar black holes, the most common type, are up to 20 times more massive than our own Sun and are likely sprinkled in the dozens within the Milky Way. And then there are the gargantuan ones in the centers of galaxies, called “supermassive black holes.” They’re each more than one million times more massive than the Sun. How these beasts formed is still being examined.
A binary black hole system, viewed from above. Credit: Bohn et al. (see http://arxiv.org/abs/1410.7775)
Fact 5: Weird time stuff happens around black holes.
This is best illustrated by one person (call them Unlucky) falling into a black hole while another person (call them Lucky) watches. From Lucky’s perspective, Unlucky’s time clock appears to be ticking slower and slower. This is in accordance with Einstein’s theory of general relativity, which (simply put) says that time is affected by how fast you go, when you’re at extreme speeds close to light. The black hole warps time and space so much that Unlucky’s time appears to be running slower. From Unlucky’s perspective, however, their clock is running normally and Lucky’s is running fast.
Fact 6: The first black hole wasn’t discovered until X-ray astronomy was used.
Cygnus X-1 was first found during balloon flights in the 1960s, but wasn’t identified as a black hole for about another decade. According to NASA, the black hole is 10 times more massive to the Sun. Nearby is a blue supergiant star that is about 20 times more massive than the Sun, which is bleeding due to the black hole and creating X-ray emissions.
Illustration of Cygnus X-1, another stellar-mass black hole located 6070 ly away. Credit: NASA/CXC/M.Weiss
Fact 7: The nearest black hole is likely not 1,600 light-years away.
An erroneous measurement of V4641 Sagitarii led to a slew of news reports a few years back saying that the nearest black hole to Earth is astoundingly close, just 1,600 light-years away. Not close enough to be considered dangerous, but way closer than thought. Further research, however, shows that the black hole is likely further away than that. Looking at the rotation of its companion star, among other factors, yielded a 2014 result of more than 20,000 light years.
Fact 8: We aren’t sure if wormholes exist.
A popular science-fiction topic concerns what happens if somebody falls into a black hole. Some people believe these objects are a sort of wormhole to other parts of the Universe, making faster-than-light travel possible. But as this Smithsonian Magazine article points out, anything is possible since we still have a lot to figure out about physics. “Since we do not yet have a theory that reliably unifies general relativity with quantum mechanics, we do not know of the entire zoo of possible spacetime structures that could accommodate wormholes,” said Abi Loeb, who is with the Harvard-Smithsonian Center for Astrophysics.
Diagram of a wormhole, or theoretical shortcut path between two locations in the universe. Credit: Wikipedia
Fact 9: Black holes are only dangerous if you get too close.
Like creatures behind a cage, it’s okay to observe a black hole if you stay away from its event horizon — think of it like the gravitational field of a planet. This zone is the point of no return, when you’re too close for any hope of rescue. But you can safely observe the black hole from outside of this arena. By extension, this means it’s likely impossible for a black hole to swallow up everything in the Universe (barring some sort of major revision to physics or understanding of our Cosmos, of course.)
Fact 10: Black holes are used all the time in science fiction.
There are so many films and movies using black holes, for example, that it’s impossible to list them all. Interstellar‘s journeys through the universe includes a close-up look at a black hole. Event Horizon explores the phenomenon of artificial black holes — something that is also discussed in the Star Trek universe. Black holes are also talked about in Battlestar: Galactica, Stargate: SG1 and many, many other space shows.
An artist's conception of a black hole binary in a heart of a quasar, with the data showing the periodic variability superposed.
Credit: Santiago Lombeyda/Caltech Center for Data-Driven Discovery
Most large galaxies harbor central supermassive black holes with masses equivalent to millions, or even billions, of Suns. Some, like the one in the center of the Milky Way Galaxy, lie quiet. Others, known as quasars, chow down on so much gas they outshine their host galaxies and are even visible across the Universe.
Although their brilliant light varies across all wavelengths, it does so randomly — there’s no regularity in the peaks and dips of brightness. Now Matthew Graham from Caltech and his colleagues have found an exception to the rule.
Quasar PG 1302-102 shows an unusual repeating light signature that looks like a sinusoidal curve. Astronomers think hidden behind the light are two supermassive black holes in the final phases of a merger — something theoretically predicted but never before seen. If the theory holds, astronomers might be able to witness two black holes en route to a collision of incredible scale.
The light curve combines data from two CRTS telescopes (CSS and MLS) with historical data from the LINEAR and ASAS surveys. Image Credit: Graham et al.
Graham and his colleagues discovered the unusual quasar on a whim. They were aiming to study quasar variability using the Catalina Real-Time Transient Survey (CRTS), which uses three ground-based telescopes to monitor some 500 million objects strewn across 80 percent of the sky, when 20 or so periodic sources popped up.
Of those 20 periodic quasars, PG 1302-102 was the most promising. It had a strong signal that appeared to repeat every five years or so. But what causes the repeating signal?
The black holes that power quasars do not emit light. Instead the light originates from the hot accretion disk that feeds the black hole. Orbiting clouds of gas, which are heated and ionized by the disk, also contribute in the form of visible emission lines.
“When you look at the emission lines in a spectrum from an object, what you’re really seeing is information about speed — whether something is moving toward you or away from you and how fast. It’s the Doppler effect,” said study coauthor Eilat Glikman from Middlebury College in Vermont, in a news release. “With quasars, you typically have one emission line, and that line is a symmetric curve. But with this quasar, it was necessary to add a second emission line with a slightly different speed than the first one in order to fit the data. That suggests something else, such as a second black hole, is perturbing this system.”
So a tight supermassive black hole binary is the most likely explanation for this oddly periodic quasar.
“Until now, the only known examples of supermassive black holes on their way to a merger have been separated by tens or hundreds of thousands of light years,” said study coauthor Daniel Stern from NASA’s Jet Propulsion Laboratory. “At such vast distances, it would take many millions, or even billions, of years for a collision and merger to occur. In contrast, the black holes in PG 1302-102 are, at most, a few hundredths of a light year apart and could merge in about a million years or less.”
But astronomers remain unsure about what physical mechanism is responsible for the quasar’s repeating light signal. It’s possible that one quasar is funneling material from its accretion disk into jets, which are rotating like beams from a lighthouse. Or perhaps a portion of the accretion disk itself is thicker than the rest, causing light to be blocked at certain spots in its orbit. Or maybe the accretion disk is dumping material onto the black hole in a regular fashion, causing periodic bursts of energy.
“Even though there are a number of viable physical mechanisms behind the periodicity we’re seeing — either the precessing jet, warped accretion disk or periodic dumping — these are all still fundamentally caused by a close binary system,” said Graham.
Astronomers still don’t have a good handle on what happens in the final few light-years of a black hole merger. And of course these two black holes still won’t collide for thousands to millions of years. Even watching for the period to shorten as they spiral inward would dwarf human timescales. But the discovery of a system so late in the game proves promising for future work.
Thanks to our powerful telescopes, there are so many places in the Universe we can see. But there are places hidden from us, and places that we’ll never be able to see.
We’re really lucky to live in our Universe with our particular laws of physics. At least, that’s what we keep telling ourselves. The laws of physics can be cruel and unforgiving, and should you try and cross them, they will crush you like a bug.
Here at Universe Today, we embrace our Physics overlords and prefer to focus on the positive, the fact that light travels at the speed of light is really helpful. This allows us to look backwards in time as we look further out. Billions of light-years away, we can see what the Universe looked like billions of years ago. Physics is good. Physics knows what’s best. Thanks physics. And where the hand of physics gives, it can also take away.
There are some parts of the Universe that we’ll never, ever be able to see. No matter what we do. They’ll always remain just out of reach. No matter how much we plead, in some sort of Kafka-esque nightmare, these rules do not appear to have conscience or room for appeal.
As we look outward in the cosmos, we look backwards in time and at the very edge of our vision is the Cosmic Microwave Background Radiation. The point after the Big Bang where everything had cooled down enough so it was no longer opaque. Light could finally escape and travel through a transparent Universe. This happened about 300,000 years after the Big Bang. What happened before that is a mystery. We can calculate what the Universe was like, but we can’t actually look at it. Possibly, we just don’t have the right clearance levels.
On the other end of the timeline, in the distant distant future. Assuming humans, or our Terry Gilliam inspired robot bodies are still around to observe the Universe, there will be a lot less to see. Distance is also out to rain on our sightseeing safari. The expansion of the Universe is accelerating, and galaxies are speeding away from each other faster and faster. Eventually, they’ll be moving away from us faster than the speed of light.
What would you see at the speed of light/
When that happens, we’ll see the last few photons from those distant galaxies, redshifted into oblivion. And then, we won’t see any galaxies at all. Their light will never reach us and our skies will be eerily empty. Just don’t let physics hear a sad tone in your voice, we don’t want to spend another night in the “joy re-education camps”
Currently, we can see a sphere of the Universe that measures 92 billion light-years across. Outside that sphere is more Universe, a hidden, censored Universe. Universe that we can’t see because the light hasn’t reached us yet. Fortunately, every year that goes by, a little less Universe is redacted from the record, and the sphere we can observe gets bigger by one light-year. We can see a little more in all directions.
Finally, let’s consider what’s inside the event horizon of a black hole. A place that you can’t look at, because the gravity is so strong that light itself can never escape it. So by definition, you can’t see what absorbs all its own light. Astronomers don’t know if black holes crunch down to a physical sphere and stop shrinking, or continue shrinking forever, getting smaller and smaller into infinity. Clearly, we can’t look there because we shouldn’t be looking there. They’re terrible places. The possibility of shrinking forever gives me the heebies.
Artistic view of a radiating black hole. Credit: NASA
And so, good news! The chocolate ration has been increased from 40 grams to 25 grams, and our physics overlords are good, can only do good, and always know what’s best for us. In fact, so good that gravity might actually provide us with a tool to “see” these hidden places, but only because “they” want us to.
When black holes form, or massive objects smash into each other, or there are “Big Bangs”, these generate distortions in spacetime called gravitational waves. Like gravity itself, these propagate across the Universe and could be detected.It’s possible we could use gravitational waves to “see” beyond the event horizon of a black hole, or past the Cosmic Microwave Background Radiation.
The problem is that gravitational waves are so faint, we haven’t even detected a single one yet. But that’s probably just a technology problem. In the end, we need a more sensitive observatory. We’ll get there. Alternately we could apply to the laws of physics board of appeals and fill in one of their 2500 page application forms in triplicate and see if we can be granted a rules exception, and maybe just get a tiny little peek behind that veil.
We live an amazing Universe, most of which we’ll never be able to see. But that’s okay, there’s enough we can see to keep us busy until infinity. What law of physics would you like to be granted a special exception to ignore. Tell us in the comments below.
