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Chris Hadfield
Retired Canadian Astronaut & Author
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Why humanity owes a lot to Jupiter

Our friendly neighborhood gas giant serves as a cosmic catcher's mitt.

NASA
  • In 1994, a comet struck Jupiter, exploding on the gas giant's surface in an incredibly violent fireball.
  • Such collisions are not uncommon for Jupiter. What is uncommon, however, are solar systems with planets like Jupiter.
  • Without Jupiter, life on Earth might have been obliterated by comets and asteroids before it even got a chance to begin. The fact that Jupiter-like planets are so rare might be one of the reasons why we haven't found intelligent life yet.

In the two years leading up to 1994, astronomers had eagerly watched the progress of a comet called Shoemaker-Levy 9 as it journeyed through our solar system. It was the first comet to be observed orbiting a planet — Jupiter, in this case — and over the years, the gas giant's gravity had ripped the comet apart into several fragments up to 1.2 miles in diameter, swirling around at 134,000 miles per hour.

The comet itself wasn't what had attracted astronomers — instead, it was the chance to observe the predicted impact of Shoemaker-Levy 9 with Jupiter. And when Shoemaker-Levy 9 finally did strike Jupiter in July of 1994, there was one hell of an explosion. When the first fragment tore into the planet, a nearly 2,000-mile-high fireball exploded with temperatures in excess of 42,000 Fahrenheit.

It's not the only time Jupiter's been hit, too. Some studies estimate that the gas giant gets hit 8,000 times more than Earth. But that number might even be higher — we can't directly observe the far side of Jupiter, after all, and the Shoemaker-Levy 9 collision was one of the first times we thought to even look for celestial bodies impacting Jupiter. It makes sense: Not only is Jupiter a huge target, its mass attracts celestial bodies as they pass through our solar system.

So, this begs the question: What if we didn't have Jupiter in our solar system to suck up these rogue asteroids and comets?

This GIF shows the fireball created by Shoemaker-Levy 9's first impact with Jupiter.

NASA

How Jupiter protects us

Jupiter is big. Really big. Like a celestial clown car, Jupiter is so large that about 1,300 Earths could comfortably fit inside it. It's incredible girth is also an incredible boon for Earthlings. Jupiter attracts many asteroids and comets like Shoemaker-Levy 9 that, if not for Jupiter, might have struck the Earth.

Famously, one such asteroid snuck by and hit Earth about 65 million years ago, setting off a chain reaction that would ultimately lead to the extinction of the dinosaurs and provide mammals like us a shot at global domination. Now that humans are on top, we would very much like to stay there. Indeed, chances are a second major impact wouldn't be so fortuitous for us as the first was. Not only that, but if Jupiter were not there to suck up all of these other asteroids and comets, life may not even have had a chance to begin on Earth at all.

Jupiter's complicated, cloudy surface. Image source: NASA

The rare Earth hypothesis

As it turns out, solar systems with planets like Jupiter are fairly uncommon in the galaxy. This fact, coupled with Jupiter's protective role in our own solar system, lends credence to what scientists call "the rare Earth hypothesis."

One of the big mysteries in astronomy and astrobiology is how devoid of life the universe apparently is. Noting the many billions of stars similar to the sun, the probability of Earth-like planets orbiting those stars, and the probability of intelligent life to develop on those planets, physicist Enrico Fermi first asked the question "Where is everybody?" This would later become known as the Fermi paradox.

This paradox was put more formally by Frank Drake in the Drake equation, which lays out a statistical basis for estimating the number of intelligent civilizations in the Milky Way. His original estimates stated that there were between 1,000 and 100,000,000 civilizations in the galaxy. As we learned more about the universe, scientists have managed to narrow this number down. Current estimates put humanity's chance of being totally alone in the galaxy at 39 percent.

Part of why this is the case is because of Jupiter. Only about 1 in 1,000 stars are both similar to the sun and have a Jupiter-like planet with a relatively stable orbit in the outer rings of the solar system. When a Jupiter-like planet's orbit is a bit more eccentric than ours is, gradually the gas giant's orbit starts to bend towards its star. On its way, the planet rips apart any material that would have otherwise eventually formed into a planet like Earth. When they get close to their star, they become "hot" Jupiters.

In solar systems with hot Jupiters, Earth-like planets are exceedingly rare. And for those solar systems where a potentially habitable, Earth-like planet does exist don't have the benefit we have from our Jupiter. In effect, we're protected by a giant, gaseous catcher's mitt; when asteroids and comets go hurtling through our solar system, Jupiter catches them before they wipe us out.



Hulu's original movie "Palm Springs" is the comedy we needed this summer

Andy Samberg and Cristin Milioti get stuck in an infinite wedding time loop.

Gear
  • Two wedding guests discover they're trapped in an infinite time loop, waking up in Palm Springs over and over and over.
  • As the reality of their situation sets in, Nyles and Sarah decide to enjoy the repetitive awakenings.
  • The film is perfectly timed for a world sheltering at home during a pandemic.
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Two MIT students just solved Richard Feynman’s famed physics puzzle

Richard Feynman once asked a silly question. Two MIT students just answered it.

Surprising Science

Here's a fun experiment to try. Go to your pantry and see if you have a box of spaghetti. If you do, take out a noodle. Grab both ends of it and bend it until it breaks in half. How many pieces did it break into? If you got two large pieces and at least one small piece you're not alone.

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Our ‘little brain’ turns out to be pretty big

The multifaceted cerebellum is large — it's just tightly folded.

Image source: Sereno, et al
Mind & Brain
  • A powerful MRI combined with modeling software results in a totally new view of the human cerebellum.
  • The so-called 'little brain' is nearly 80% the size of the cerebral cortex when it's unfolded.
  • This part of the brain is associated with a lot of things, and a new virtual map is suitably chaotic and complex.

Just under our brain's cortex and close to our brain stem sits the cerebellum, also known as the "little brain." It's an organ many animals have, and we're still learning what it does in humans. It's long been thought to be involved in sensory input and motor control, but recent studies suggests it also plays a role in a lot of other things, including emotion, thought, and pain. After all, about half of the brain's neurons reside there. But it's so small. Except it's not, according to a new study from San Diego State University (SDSU) published in PNAS (Proceedings of the National Academy of Sciences).

A neural crêpe

A new imaging study led by psychology professor and cognitive neuroscientist Martin Sereno of the SDSU MRI Imaging Center reveals that the cerebellum is actually an intricately folded organ that has a surface area equal in size to 78 percent of the cerebral cortex. Sereno, a pioneer in MRI brain imaging, collaborated with other experts from the U.K., Canada, and the Netherlands.

So what does it look like? Unfolded, the cerebellum is reminiscent of a crêpe, according to Sereno, about four inches wide and three feet long.

The team didn't physically unfold a cerebellum in their research. Instead, they worked with brain scans from a 9.4 Tesla MRI machine, and virtually unfolded and mapped the organ. Custom software was developed for the project, based on the open-source FreeSurfer app developed by Sereno and others. Their model allowed the scientists to unpack the virtual cerebellum down to each individual fold, or "folia."

Study's cross-sections of a folded cerebellum

Image source: Sereno, et al.

A complicated map

Sereno tells SDSU NewsCenter that "Until now we only had crude models of what it looked like. We now have a complete map or surface representation of the cerebellum, much like cities, counties, and states."

That map is a bit surprising, too, in that regions associated with different functions are scattered across the organ in peculiar ways, unlike the cortex where it's all pretty orderly. "You get a little chunk of the lip, next to a chunk of the shoulder or face, like jumbled puzzle pieces," says Sereno. This may have to do with the fact that when the cerebellum is folded, its elements line up differently than they do when the organ is unfolded.

It seems the folded structure of the cerebellum is a configuration that facilitates access to information coming from places all over the body. Sereno says, "Now that we have the first high resolution base map of the human cerebellum, there are many possibilities for researchers to start filling in what is certain to be a complex quilt of inputs, from many different parts of the cerebral cortex in more detail than ever before."

This makes sense if the cerebellum is involved in highly complex, advanced cognitive functions, such as handling language or performing abstract reasoning as scientists suspect. "When you think of the cognition required to write a scientific paper or explain a concept," says Sereno, "you have to pull in information from many different sources. And that's just how the cerebellum is set up."

Bigger and bigger

The study also suggests that the large size of their virtual human cerebellum is likely to be related to the sheer number of tasks with which the organ is involved in the complex human brain. The macaque cerebellum that the team analyzed, for example, amounts to just 30 percent the size of the animal's cortex.

"The fact that [the cerebellum] has such a large surface area speaks to the evolution of distinctively human behaviors and cognition," says Sereno. "It has expanded so much that the folding patterns are very complex."

As the study says, "Rather than coordinating sensory signals to execute expert physical movements, parts of the cerebellum may have been extended in humans to help coordinate fictive 'conceptual movements,' such as rapidly mentally rearranging a movement plan — or, in the fullness of time, perhaps even a mathematical equation."

Sereno concludes, "The 'little brain' is quite the jack of all trades. Mapping the cerebellum will be an interesting new frontier for the next decade."

Economists show how welfare programs can turn a "profit"

What happens if we consider welfare programs as investments?

A homeless man faces Wall Street

Spencer Platt/Getty Images
Politics & Current Affairs
  • A recently published study suggests that some welfare programs more than pay for themselves.
  • It is one of the first major reviews of welfare programs to measure so many by a single metric.
  • The findings will likely inform future welfare reform and encourage debate on how to grade success.
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