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Mystery of the gigantic Oort cloud from deep space explained
Astronomers possibly solve the mystery of how the enormous Oort cloud, with over 100 billion comet-like objects, was formed.
- The Oort cloud is a gigantic "cloud" at the edge of the solar system, about 3,000 times the distance between the Earth and the Sun.
- Astronomers used computer simulations to reconstruct the first 100 million years of the Oort cloud's existence.
- The Oort cloud may consist of the "leftovers" from the solar system's formation
Astronomers have calculated the first 100 million years of the history of the gigantic Oort cloud – a theoretical entity that contains 100 billion or so comet-like objects and forms a giant spherical shell around the sun and the rest of the solar system. NASA describes it as "a big, thick-walled bubble made of icy pieces of space debris the sizes of mountains and sometimes larger."
The Oort cloud was named after Dutch astronomer Jan Hendrik Oort, who discovered it in the 1950s. He was looking to understand why some comets in the solar system have elongated orbits. Scientists now believe the Oort Cloud is the source of most such comets.
The cloud is believed to be extremely far from the sun, many times more distant than the outer reaches of the Kuiper belt, the area of the solar system past the orbit of Neptune that contains comets, asteroids, and small icy space bodies as well as the dwarf planet Pluto.
According to NASA, the inner edge of the Oort cloud is likely between 2,000 and 5,000 AU (astronomical units or Earth-Sun distances) from the sun. The outer edge is probably 10,000 to 100,000 AU from the sun. By comparison, the Kuiper belt is about 30 to 50 AU away from the sun.
Oort cloud: the leftovers of the solar system
In a preprint article (accepted for publication in Astronomy & Astrophysics), a team of astronomers from Leiden University in the Netherlands describe how they used sophisticated computer simulations to determine how the Oort cloud formed.
They took a new approach by starting from separate events that might have happened in the early days of the universe and connecting them together. This allowed them to map out the full history of the origins of the gargantuan cloud.
As explained in their press release, the scientists used the ending calculations from one event as the starting calculation for the next event.
Protoplanetary disk.Credit: Pat Rawlings / NASA
Their simulations confirmed that the Oort cloud is what remained of the protoplanetary disk of gas and debris from which it is believed our solar system formed about 4.6 billion years ago.
The cloud has comet-like objects made of debris from two places in the universe. Some of them are from nearby parts of the solar system, such as asteroids expelled by giant planets like Jupiter. Another group of objects in the Oort cloud comes from a thousand or so stars that were around when our sun was born, eventually drifting apart from each other.
"With our new calculations, we show that the Oort cloud arose from a kind of cosmic conspiracy," said astronomer and simulation expert Simon Portegies Zwart from Leiden University, adding, "in which nearby stars, planets, and the Milky Way all play their part. Each of the individual processes alone would not be able to explain the Oort cloud. You really need the interplay and the right choreography of all the processes together."
He added that the Oort cloud was ultimately produced by "the interplay and the right choreography of all the processes together."
As it is so far away, humanity hasn't yet built a telescope powerful enough to see the small, faint objects of the Oort cloud directly. By some estimates, it would take telescopes that are 100 billion times better than what we currently have to see into the cloud. Even the new James Webb Telescope that's launching later in 2021 is unlikely to be able to see that far, confirmed Nobel laureate (and James Webb Telescope scientist) Dr. John Mather.
It would also take humanity a long time to reach the Oort cloud. As NASA estimated, even if you consider that the Voyager 1 probe can cover about a million miles every day, it would take it about 300 years to reach the inner edge of the Oort Cloud. And to get all the way through, it would likely require another 30,000 years.
- The sun may have had a long-lost companion star - Big Think ›
- The view from Voyager 1, humanity's furthest spacecraft - Big Think ›
"You dream about these kinds of moments when you're a kid," said lead paleontologist David Schmidt.
- The triceratops skull was first discovered in 2019, but was excavated over the summer of 2020.
- It was discovered in the South Dakota Badlands, an area where the Triceratops roamed some 66 million years ago.
- Studying dinosaurs helps scientists better understand the evolution of all life on Earth.
David Schmidt, a geology professor at Westminster College, had just arrived in the South Dakota Badlands in summer 2019 with a group of students for a fossil dig when he received a call from the National Forest Service. A nearby rancher had discovered a strange object poking out of the ground. They wanted Schmidt to take a look.
"One of the very first bones that we saw in the rock was this long cylindrical bone," Schmidt told St. Louis Public Radio. "The first thing that came out of our mouths was, 'That kind of looks like the horn of a triceratops.'"
After authorities gave the go-ahead, Schmidt and a small group of students returned this summer and spent nearly every day of June and July excavating the skull.
Credit: David Schmidt / Westminster College
"We had to be really careful," Schmidt told St. Louis Public Radio. "We couldn't disturb anything at all, because at that point, it was under law enforcement investigation. They were telling us, 'Don't even make footprints,' and I was thinking, 'How are we supposed to do that?'"
Another difficulty was the mammoth size of the skull: about 7 feet long and more than 3,000 pounds. (For context, the largest triceratops skull ever unearthed was about 8.2 feet long.) The skull of Schmidt's dinosaur was likely a Triceratops prorsus, one of two species of triceratops that roamed what's now North America about 66 million years ago.
Credit: David Schmidt / Westminster College
The triceratops was an herbivore, but it was also a favorite meal of the Tyrannosaurus rex. That probably explains why the Dakotas contain many scattered triceratops bone fragments, and, less commonly, complete bones and skulls. In summer 2019, for example, a separate team on a dig in North Dakota made headlines after unearthing a complete triceratops skull that measured five feet in length.
Michael Kjelland, a biology professor who participated in that excavation, said digging up the dinosaur was like completing a "multi-piece, 3-D jigsaw puzzle" that required "engineering that rivaled SpaceX," he jokingly told the New York Times.
Morrison Formation in Colorado
James St. John via Flickr
The Badlands aren't the only spot in North America where paleontologists have found dinosaurs. In the 1870s, Colorado and Wyoming became the first sites of dinosaur discoveries in the U.S., ushering in an era of public fascination with the prehistoric creatures — and a competitive rush to unearth them.
Since, dinosaur bones have been found in 35 states. One of the most fruitful locations for paleontologists has been the Morrison formation, a sequence of Upper Jurassic sedimentary rock that stretches under the Western part of the country. Discovered here were species like Camarasaurus, Diplodocus, Apatosaurus, Stegosaurus, and Allosaurus, to name a few.
|Credit: Nobu Tamura/Wikimedia Commons|
As for "Shady" (the nickname of the South Dakota triceratops), Schmidt and his team have safely transported it to the Westminster campus. They hope to raise funds for restoration, and to return to South Dakota in search of more bones that once belonged to the triceratops.
Studying dinosaurs helps scientists gain a more complete understanding of our evolution, illuminating a through-line that extends from "deep time" to present day. For scientists like Schmidt, there's also the simple joy of coming to face-to-face with a lost world.
"You dream about these kinds of moments when you're a kid," Schmidt told St. Louis Public Radio. "You don't ever think that these things will ever happen."
A new brain imaging study explored how different levels of the brain's excitatory and inhibitory neurotransmitters are linked to math abilities.
- Glutamate and GABA are neurotransmitters that help regulate brain activity.
- Scientists have long known that both are important to learning and neuroplasticity, but their relationship to acquiring complex cognitive skills like math has remained unclear.
- The new study shows that having certain levels of these neurotransmitters predict math performance, but that these levels switch with age.
Why do roughly one in five people find math especially difficult?
You might blame teaching methods, which some argue explains why the U.S. lags behind other countries in standardized math test scores. You could point to math anxiety, which affects about 20 percent of students and 25 percent of teachers, according to surveys. And there are also medical conditions that make math difficult, such as dyscalculia, a learning disability that disrupts the normal development of arithmetic skills.
But another explanation centers on neurotransmitters. In a new study published in PLOS Biology, researchers explored how the brain's levels of GABA and glutamate relate to math abilities over time in students of varying ages. The results showed that levels of these neurotransmitters can predict students' performance on math tests. However, this relationship seems to flip as people get older.
GABA and glutamate are responsible for regulating brain activity. In the mature brain, GABA is the brain's main inhibitory neurotransmitter, helping to block impulses between nerve cells in the brain, which can calm feelings of stress, anxiety, or fear. GABA is made from glutamate, the brain's major excitatory neurotransmitter that helps send signals throughout the central nervous system.
Researchers have long known that these neurotransmitters play crucial roles in learning, development, and neuroplasticity. That is partly because they are thought to help trigger developmental windows (or "sensitive periods") during which neural systems become more plastic and better able to acquire certain cognitive skills.
"Importantly, sensitive periods vary for different functions, with relatively simple abilities (e.g., sensorimotor integration) occurring earlier in development, while the sensitive period for acquiring more complex cognitive functions extends into the third decade of life," the researchers wrote.
GABA, glutamate, and math
Still, the exact relationship between GABA, glutamate, and complex cognitive functions has remained unclear. The new study explored that relationship by focusing on associations between the neurotransmitters and math abilities, which "provides a unique cognitive model to examine these questions due to its protracted skill acquisition period that starts already from early childhood and can continue for nearly two decades," the researchers wrote.
For the study, the researchers measured levels of GABA and glutamate in the left intraparietal sulcus (IPS) of 255 students, ranging from primary school to college. The participants completed a math test as their brains were imaged. About a year and a half later, the participants repeated the same process.
"The longitudinal design allowed us to further examine whether neurotransmitter concentration is linked to MA [mathematical abilities] as well as predict MA in the future," the researchers wrote. "Crucially, adopting this design allowed us to discern the selective effect of glutamate and GABA in response to natural (i.e., learning in school) rather than artificial environmental stimulation, thus allowing us to test the knowledge gained from lab-based experiments in high ecological settings."
The results suggest that GABA and glutamate play an important role in math abilities, but that the dynamic switches with age. For the young participants, higher GABA levels in the IPS were associated with higher scores on math tests. The opposite was observed among older students: higher glutamate levels correlated with higher scores. Both results held true on subsequent math tests.
Although the study sheds light on how neurotransmitter levels at different stages of development contribute to learning some cognitive skills, like math, the researchers noted that acquiring other skills may involve different processes.
"Our findings may also highlight a general principle that the developmental dynamics of regional excitation and inhibition levels in regulating the sensitive period and plasticity of a given high-level cognitive function (i.e., MA) may be different compared to another high-level cognitive function (i.e., general intelligence) that draws on similar, albeit not identical, cognitive and neural mechanisms," they wrote.
Do our thoughts have any meaning whatsoever?
- Epiphenomenalism is the idea that our conscious minds serve no role in affecting the physical world.
- On the contrary, our thoughts are a causally irrelevant byproduct of physical processes that are occurring inside of our brains.
- According to epiphenomenalism, we are like children pretending to drive a car — it can be great fun, but we are really not in charge.
What if you don't matter? What if all of your thoughts, precious feelings, great dreams, and terrible fears are completely, utterly, spectacularly irrelevant? Might it be that all of your mental life is just some pointless spectator, looking on as your body does the important stuff of keeping you alive and running about? What actually is the point of a thought?
This is the view of "epiphenomenalism," and it might just be one of the most disturbing ideas in all of philosophy.
The pointless chiming of the clock
On any given day, we will make thousands of decisions and perform countless actions. We will move our legs to walk, open our mouths to eat, smile at our friends, kiss our loved ones, and so on. Today, we know enough about neuroscience and physiology to give a complete and full account of how this happens. We can point to the parts of the brain that activate, the route the nerve signals will take up and down the body, the way the muscles will contract, and how the body will react. We can, in short, give a full physical account of everything we do.
The question, then, is: what is the point of our consciousness? If we can explain all of our behavior quite happily (or "sufficiently" as philosophers like to say) with physical causes, what is there left for our thoughts to do?
Anthropologist Thomas Huxley argued that our thoughts are a bit like a clock's chime at the hour. It makes a sound, but it makes no difference at all to the time. Likewise, our thoughts and subjective feelings might be very nice and appear very special to us, but they are completely uninvolved.
The problem of mind-body dualism
This all stems from a key problem of dualism, which is the philosophical idea that the mind and body are different things. There is something intuitive to the idea. When I imagine a flying dragon with fiery breath and leathery wings, that is entirely different from the physical world of lizards, candles, and bats. Or, put another way, you cannot touch with your finger or cut with a knife the stuff that happens in your head. But we don't like believing that our thoughts don't exist. So, what are they?
The problem in dualism is understanding how something mental, nonphysical, and subjective possibly could affect the physical world and especially my physical body. Yet, it clearly happens. For instance, if I want a cupcake, I make my hand move toward it.
So, how can the immaterial affect the material? This "problem of causal interaction" is not easily resolved, and so some philosophers prefer the epiphenomenalist response, "Perhaps our minds don't do anything." If we want to retain the idea that our minds exist but in a completely different way as the physical world, then it might be more palatable to jettison the idea that they do anything at all.
Integrated information theory
Then, what is the point of consciousness? There are some, such as neuroscientist Daniel De Haan and philosophers Giulio Tononi and Peter Godfrey-Smith, who argue that consciousness can best be explained by "integrated information theory."
In this theory, consciousness is something that emerges from the sum of our cognitive processes — or, more specifically, the "capacity of a system to integrate information," as Tononi writes. In other words, consciousness is a net product of all the other things our mind is doing, such as synchronizing sensory inputs, focusing on specific objects, accessing various types of memory, and so on. The mind is an overseer at the center of a huge web and is the result or byproduct of all the incredibly complex things it needs to do.
But this kind of "emergentist" theory (since the mind "emerges" from its operations) does leave us with some epiphenomenal questions. It seems to suggest that the mind does exist but that it can be fully explained and accounted for by other physical processes. For instance, if we suppose our consciousness is the product of our complex and various sensory inputs, as Godfrey-Smith offers, then what does conscious thought actually add to the equation that our sight, smell, interoception, and so on are not already doing? By analogy, if a "traffic jam" is just the term for a collection of stationary cars and trucks, what does the concept "traffic jam" add that all those vehicles don't already provide? A traffic jam has no causal role to play.
This is not to say that consciousness is a mistake or without value. After all, without it, I would not be me and you would not be you. Pleasure would not exist. There would be no world at all. We cannot even imagine a life without consciousness. And epiphenomenalism does believe that physical events, like our synaptic sparks and neuronal interactions, do cause our mental events.
But if epiphenomenalism is correct, it means that our thoughts don't add anything to the physical world that isn't already ongoing. It means that we are locked in our heads. All the thoughts and feelings are ultimately pointless or nonsense. We are like children pretending to drive a car — it can be great fun, but we are really not in charge.
For the ancients, hospitality was an inviolable law enforced by gods and priests and anyone else with the power to make you pay dearly for mistreating a stranger.