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The model of vision as we now know it first appeared in the 16th century, when Felix Platter proposed that the eye functions as an optic and the retina as a receptor. Light from an external source enters through the cornea and is refracted by the lens, forming an image on the retina—the light-sensitive membrane located in the back of the eye. The retina detects photons of light and responds by firing neural impulses along the optic nerve to the brain.
There’s an unlikely sounding quirk to this set-up, which is that mechanically speaking, our eyes see everything upside down. That’s because the process of refraction through a convex lens causes the image to be flipped, so when the image hits your retina, it’s completely inverted. Réné Descartes proved this in the 17th century by setting a screen in place of the retina in a bull’s excised eyeball. The image that appeared on the screen was a smaller, inverted copy of the scene in front of the bull’s eye.
So why doesn’t the world look upside down to us? The answer lies in the power of the brain to adapt the sensory information it receives and make it fit with what it already knows. Essentially, your brain takes the raw, inverted data and turns it into a coherent, right-side-up image. If you’re in any doubt as to the truth of this, try gently pressing the bottom right side of your eyeball through your bottom eyelid—you should see a black spot appear at the top left side of your vision, proving the image has been flipped.
In the 1890s, psychologist George Stratton carried out a series of experiments [PDF] to test the mind’s ability to normalize sensory data. In one experiment he wore a set of reversing glasses that flipped his vision upside down for eight days. For the first four days of the experiment, his vision remained inverted, but by day five, it had spontaneously turned right side up, as his perception had adapted to the new information.
That’s not the only clever trick your brain has up its sleeve. The image that hits each of your retinas is a flat, 2D projection. Your brain has to overlay these two images to form one seamless 3D image in your mind—giving you depth perception that’s accurate enough to catch a ball, shoot baskets, or hit a distant target.
Your brain is also tasked with filling in the blanks where visual data is missing. The optic disc, or blind spot, is an area on the retina where the blood vessels and optic nerve are attached, so it has no visual receptor cells. But unless you use tricks to locate this blank hole in your vision, you’d never even notice it was there, simply because your brain is so good at joining the dots.
Another example is color perception; most of the 6 to 7 million cone photoreceptor cells in the eye that detect color are crowded within the fovea centralis at the center of the retina. At the periphery of your vision, you pretty much only see in black and white. Yet we perceive a continuous, full-color image from edge to edge because the brain is able to extrapolate from the information it already has.
This power of the mind to piece together incomplete data using assumptions based on previous experience has been labeled "unconscious inference" by scientists. As it draws on our past experiences, it’s not a skill we are born with; we have to learn it. It’s believed that for the first few days of life babies see the world upside down, as their brains just haven’t learned to flip the raw visual data yet. So don’t be alarmed if a newborn looks confused when you smile—they’re probably just trying to work out which way up your head is. [Reply]
What if we built a huge radio telescope on the far side of the moon?
The FARSIDE telescope
Burns and his colleagues recently completed a NASA-funded study for a rover-deployed radio telescope that would spread out 128 antennas in a flowerlike shape about 6 miles (10 kilometers) wide. They call their project the Farside Array for Radio Science Investigations of the Dark ages and Exoplanets. Or, more succinctly, FARSIDE.
FARSIDE would study the magnetic fields of planets around distant stars, helping astronomers better understand which exoplanets might be truly habitable. The telescope would also give astronomers their first real chance to study a pivotal period of early cosmological history called the “Dark Ages.” During this epoch, both stars and galaxies hadn’t yet formed, so researchers can't see any of the matter that existed at the time.
NASA also funded another study on a proposal aimed at building an Arecibo-style radio telescope inside of a lunar crater, a project led by Jet Propulsion Laboratory robotics technologist Saptarshi Bandyopadhyay. After spending three years going through various designs of the telescope, he recently received funding from the NASA Institute for Advanced Concepts to continue pursuing the project.
And while multiple lunar telescope proposals are now closer to reality than any others in recent decades, "We still have a long road ahead," Bandyopadhyay says.
But Burns is optimistic. He’s now working with Jeff Bezos’ space company, Blue Origin, which has built a Moon lander capable of landing 5 tons’ worth of cargo on the lunar surface. That’s more than enough to carry FARSIDE. All they need now is the roughly $1 billion in funding to make it happen.
Originally Posted by Fish:
This is what it looks like when an astronaut spends ~200 days in zero G on the ISS, and has to come back to Earth and deal with gravity again....
Yeah we’ve evolved to have the effects of gravity. Interesting to see how it will play out when we go interstellar [Reply]
Imagine seeing this beast, and you're holding a wooden spear....
The Giant Short-Faced Bear
Arctodus simus
The Fastest Running Bear That Ever Lived
Also called the bulldog bear, the giant short-faced bear (Arctodus simus) was undoubtedly the fastest running bear that ever lived. Rangier and longer legged than any bear today, it was about five feet at the shoulders when walking and stood as tall as 12 feet on its hind legs. Unlike pigeon-toed modern bears, its toes pointed straight forward, enabling it to walk with a fast, purposeful gait. It probably could run over 40 miles per hour despite weighing over 1500 pounds.
On 4 feet, he was 5½ to 6 feet at the shoulders.
With the front legs straight, the skeleton is 66 inches to the top of the shoulder blades (the big shield-shaped shoulder bones). If short-faced bears had a hump of muscle on the shoulders, he could have been as much as 6 feet at the shoulders.
On 2 legs, he stood 11 to 12 feet tall.
From the crown to the hip joint and down to the heel is 134 inches. That’s 11 feet, 2 inches standing up looking at you or peering down through a basketball hoop. He could look up and bite a branch 12 feet high.
He could reach up 14½ to 15 feet.
He could reach 2 ½ to 3 feet higher with a paw than he could reach with his mouth. This skeleton measures 72 inches from the center of the shoulder blade to the tips of the toes (adding 2 inches for the missing claws). Subtracting 42 inches from the center of the shoulder blade to the tip of the nose, this bear could reach 30 inches above his up-stretched nose—to at least 14½ feet. If he rotated his shoulder upward a few inches, he could reach even higher. Ice Age campers had to hang their food higher than campers do today. [Reply]
Originally Posted by Fish:
Imagine seeing this beast, and you're holding a wooden spear....
The Giant Short-Faced Bear
Arctodus simus
The Fastest Running Bear That Ever Lived
Also called the bulldog bear, the giant short-faced bear (Arctodus simus) was undoubtedly the fastest running bear that ever lived. Rangier and longer legged than any bear today, it was about five feet at the shoulders when walking and stood as tall as 12 feet on its hind legs. Unlike pigeon-toed modern bears, its toes pointed straight forward, enabling it to walk with a fast, purposeful gait. It probably could run over 40 miles per hour despite weighing over 1500 pounds.
On 4 feet, he was 5½ to 6 feet at the shoulders.
With the front legs straight, the skeleton is 66 inches to the top of the shoulder blades (the big shield-shaped shoulder bones). If short-faced bears had a hump of muscle on the shoulders, he could have been as much as 6 feet at the shoulders.
On 2 legs, he stood 11 to 12 feet tall.
From the crown to the hip joint and down to the heel is 134 inches. That’s 11 feet, 2 inches standing up looking at you or peering down through a basketball hoop. He could look up and bite a branch 12 feet high.
He could reach up 14½ to 15 feet.
He could reach 2 ½ to 3 feet higher with a paw than he could reach with his mouth. This skeleton measures 72 inches from the center of the shoulder blade to the tips of the toes (adding 2 inches for the missing claws). Subtracting 42 inches from the center of the shoulder blade to the tip of the nose, this bear could reach 30 inches above his up-stretched nose—to at least 14½ feet. If he rotated his shoulder upward a few inches, he could reach even higher. Ice Age campers had to hang their food higher than campers do today.
Shit goes in the Nope thread. Fucking bears are terrifying to start with. [Reply]
