Scientists Have Recorded the Sound of Two Black Holes Colliding, and You Can Hear It Too
This was the first direct measurement of gravitational waves ever, as predicted by Einstein.
Something happened 3 billion years ago that changed the makeup of our prodigious universe forever. Two enormous black holes collided, resulting in an intense explosion and forming a solitary object 49 times as massive as our sun.
The explosion formed and released energy two times our sun’s mass within a fraction of a second. This sent out gravitation waves so powerful that they altered the fabric of space-time itself. A super-massive black hole arose in the aftermath. Scientists were recently able to detect this cataclysmic collision, and are learning more about black holes and the cosmos as a result.
The National Science Foundation’s cutting-edge gravitational wave observatory made these detections. The facility is called the twin Laser Interferometer Gravitational-Wave Observatory (LIGO). It’s run by an international group of scientists including some from NASA, MIT, and Caltech.
LIGO has two different locations, one in Hanford, Washington State and the other near Livingston, Louisiana. They’re purposely 1,800 miles (approx. 2,896 km) apart. The gravity waves were incredibly subtle. They altered space on and around Earth at just a fraction of the width of a proton. Yet, the instrumentation is so sensitive it can pick up such delicate occurrences.
An interferometer is basically a laser-based measuring instrument that can detect gravitational waves and locate their origin. By carefully observing light and space with two gigantic interferometers, researchers can learn much more about gravity, one of the four main forces of the universe. LIGO scientists say, these dual observatories are on the same level of complexity as the large hadron collider (LHC) at CERN. LIGO is liable to make discoveries that’ll impact quantum mechanics, relativity, astronomy, and even nuclear physics.
This is the third time gravity waves have been detected using instruments on Earth and the first direct measurement. We now know more about stellar mass black holes, how they’re formed, the areas which they inhabit, and how two of them can end up in a spinning dance of death and merge. In this particular case, one was about 30 times as massive as the sun and the other 19 times as massive. The larger one drew the smaller in.
As they pulled closer they began swirling around one another, in a waltz lasting eons, sending out gravitational waves as they went, getting closer and closer until they united, which caused an explosion of astronomical proportions. Sounds darkly romantic. The findings were published in the journal Physical Review Letters. Researchers were even able to capture sounds associated with their final embrace.
Want to hear it? Click here:
So what is a black hole, exactly? A stellar mass black hole is the remains of a once mighty star. Astronomers believe that when a massive star runs out of nuclear fuel, it implodes. A smaller star, say the size of our sun, will eventually expand into a red giant and then collapse into a white dwarf.
With much larger stars, something different occurs. The outward pressure once pushing energy out into space is gone. As a result, the pulling pressure of gravity is no longer offset and so begins pulling everything inward with tremendous force. The gravitational waves resulting in the union of these two black holes was detected in September and December of 2015. Researchers have been studying them since then.
LIGO team member Laura Cadonati of Georgia Tech told National Geographic, “Before our discoveries, we didn’t even know for sure that these black holes existed.” Also previous to this, astronomers thought they couldn’t get any bigger than 10 solar masses. These newly discovered ones are far more massive.
One theory is that such black holes came from stars mostly made up of helium and hydrogen. These gases are stable and lose little mass over time. When the star expires, more mass is involved in the implosion, making the event much more powerful.
LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet).
The LIGO team carefully studied the detected gravitational waves. From them, they could determine what direction each black hole was spinning in before the collision and the axis of each. From there, scientists theorized that these may have been sibling stars. Their remains dancing orbs of the blackest darkness, circling one another like predators, until the larger swallowed the smaller.
However, some data suggests they these stars were actually far apart, initially, and ultimately found themselves in each other’s orbit, with the larger drawing the smaller one in. Scientists hope these findings will give them a better understanding of stars, how they develop over time, and more about star clusters. They also hope to gain insights if they can, on the existence of dark matter.
Einstein predicted such gravitational waves a century ago while formulating relativity. But he thought the effect so minuscule, we would never be able to measure it. Now, not only can we, we’re be able to use the data collected to understand the universe in an entirely new way.
Most of our observations of the universe have been electro-magnetic to date. But with precise gravitational measurements and observations, we’ll be able to learn more about the universe through an entirely different lens.
Want to learn more about LIGO and black hole collisions? Click here:
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Experts argue the jaws of an ancient European ape reveal a key human ancestor.
- The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
- Researchers speculate it could be a previously unknown species and one of humanity's earliest evolutionary ancestors.
- These fossils may change how we view the evolution of our species.
Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.
A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.
Rethinking humanity's origin story
The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)
As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.
David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.
The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.
Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"
He recently outlined this idea at a conference of the American Association of Physical Anthropologists.
It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.
"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."
Migrating out of Africa
In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.
Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.
The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.
The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.
Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.
Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.
Did we head east or south of Eden?
Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.
Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.
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