The Eye of God - Science and Mysteries (Part 2)
Continuation of Part 1 - - - Could these be evidence of intelligence, as some of these amateurs believe, or is nature just teasing us? Well, there's millions of rocks on the surface of Mars in various configurations. In a chaotic system with so many different variations, nearly any conceivable shape will be visible somewhere at some point in time. And those shapes can change. In 1976, a Mars orbiter saw the infamous face on Mars, but in 2001, a more advanced orbiter saw the same feature. With different lighting and higher resolution, the face virtually disappears. Nevertheless, we have an innate human tendency to see familiar forms in all kinds of objects, even here on Earth. At the top of this crest right here, I see what looks like a toad or a frog. And if we turn behind us and tilt our heads slightly, we can see the facial features of something that looks almost like a troll or a goblin, so it really demonstrates how you can take very unfamiliar-looking terrain and find features in it that look very familiar to us. The shapes on Mars teach us about the environment that formed them.
Today, Mars is a very dry, windy place, and so the only forces that are really acting upon rocks today on Mars are the wind and impacts. Earlier in Mars' history, if Mars was a much wetter place than it is today, water would have also contributed to the shape and appearance of the rocks on the surface. Wind and weather may explain how the rocks of Mars take on so many different shapes, but what explains the even more bizarre shapes hurtling towards us through the far reaches of space?
Among the glistening stars fixed permanently in ancient skies, an occasional misbehaving intruder would strike fear into the hearts of the earliest astronomers. Today we call them comets, from the Greek word for "long hair," an allusion to their glowing tails. To our ancestors, they were invariably bad news. Comets were terrifying to our ancestors. They didn't know what they were. They didn't know where they came from. They just appeared, and they were unlike anything they had ever seen before. Records of comet sightings go back at least as far as 1600 B.C. in China, where they were known as "vile stars."
Other cultures blamed them for various calamities: the murder of Julius Caesar in Rome, the Black Death in England, the arrival of the conquistadors in South America. Modern science tells us comets are dirty snowballs, collections of ice and dust, left over from the solar system's formation. The sun heats them up, and jets of matter stream out to form their spectacular tails. But the closer you look, the stranger comets become. Even through a telescope, we didn't really know what the true shape of a comet was, until we were able to send spacecraft out to visit them and look up-close.
The spacecraft made the first flyby in 1985, revealing a close-up of Halley's Comet. It proved that comets are lumpy objects in the strangest of shapes. And now that we've gotten up-close views, we see that they don't look anything like we thought. There are a handful of them that are sort of roundish, but the majority of those we've seen have a double-lobed shape.
In 2004, the spacehip was launched on a ten-year journey to orbit and place a lander on a comet more than 300 million miles from Earth. Prior to the launch, the Hubble space telescopes snapped 61 grainy photos of the comet. By analyzing tiny fluctuations in its brightness, astronomers calculated its approximate form-- an irregular lump, tumbling through space at two revolutions per day.
But in late 2014, the probe finally approached the comet, and scientists were shocked at the bizarre shape they saw. The very recent took exquisite photographs of Comet 67P, showing that it actually resembles a rubber ducky. It would have been awesome if it was a real rubber ducky, but it's just a bunch of rocks that look like a rubber ducky. The thing is, we don't really know how you make a comet that is this shape. It's extremely complicated, and we didn't really expect to see something that was that shape to begin with.
There are a couple of different ways in which comets could get that double-lobed shape. One is, indeed, two objects that sort of stick together that, when they collide, they don't collide with enough force to bounce off each other or shatter each other but just to sort of stick to one another. But could Comet 67P have formed as a single object, getting its curious shape later on? Now, you could also imagine that the cometary physics is at work in sculpting this particular odd shape.
As the comet comes into our inner solar system, gases start to stream off from it as it gets heated up by the light from our sun. You can think of these a little bit as though they were like geysers on our planet, geologic activity where warmer material star to stream out of the comet, possibly causing cracking and reshaping of the surface. Could tell us which of the scenarios is the right one? Recent observations show that the composition of the two lobes of 67P are very similar. That suggests they came from the same body. We also see that most of the outgassing comes right at the neck of the rubber ducky, right at the thinnest part, so it wears it away and leaves two big lobes on either end.
Comets are the lightweights in nearby space. The asteroids and dwarf planets are their big cousins, heavier, denser, and in many respects, stranger. What forces mold these planetary mavericks, and why, in their midst, is there a place in space where X marks the spot? Planet Earth has always been a target for impacts from space. A giant impact may killed off the dinosaurs about 65 million years ago. And ancient mythology is filled with legends of rocks from the sky. The Greek deity Kronos is said to have cast a meteor to Earth landing at Delphi, where it was worshipped as sacred. This brings the search for strange shapes in the universe to the space between Mars and Jupiter, where the oddly formed asteroids are found. Most meteorites come from the asteroid belt. They're little chunks of asteroid that, through collisions, got knocked off their orbits and fell to Earth.
Austria, 1492. The 250-pound Thunder-stone of Ensisheim falls in a fiery streak. A thunderclap is heard for hundreds of miles around. Like comets, meteorites were bad news. Emperor Maximilian was so worried about the meteorite, he had it chained to the church floor because only by securing it to holy ground could he neutralize the evil influence. Mysteries among these space rocks persist today. An eerily ominous shape appeared in the asteroid belt in 2010. Why did an X suddenly appear there, with a trail of debris lagging behind it? Here we have a very unusual asteroid that has a tail and looks like a comet, but further observation showed that it has no gas in the tail like a comet would. Instead, the tail is made of dust. Scientists believe the mysterious debris tail resulted from a small asteroid striking a much larger one, but why the cloud of dust in the shape of an X?
One possible explanation for the X shape is that it's caused by a collision. The two asteroids were not symmetrical, and so the crash is not symmetrical. Imagine a pool of water. If you drop a single drop into it, you get perfectly round, smooth ripples, but if you drop something else, like ice cubes with square edges, you'll get a ragged splash, kind of like the ragged X in the asteroid crash. Collisions help make the asteroid belt an astronomical sideshow made up of a fantastic variety of misshapen freaks. Asteroid Eros may look like a ballet slipper to some, but other asteroids are grotesque figures that defy description. The lumpy, irregular shapes of asteroids are basically pretty random. There's no favored shape. In fact, irregular shapes are found throughout the solar system.
But why are some moons or asteroids round while others are such bizarre lumps? The largest objects in our solar system, and even some very large asteroids, can have their shape be dominated mostly by gravitational forces pulling things into a spherical shape. In the solar system, everything above about 400 miles in diameter is spherical, because at that size, gravity is strong enough to crush rock. It presses from all sides toward the center. It's something like someone's hands pressing on a lump of snow to make a spherical snowball.
Gravity has done its work on Ceres, the most massive object in the asteroid belt. The began orbiting the asteroid in March 2015, revealing it to be fully spherical in shape. Because its shape is dominated by gravity, it conforms to the definition of a dwarf planet. Pluto and other dwarf planets in the outer solar system follow the same rule and are also spherical in shape. The one exception to this in our solar system is the dwarf planet Haumea, which has a very elongated shape. Haumea lies out beyond the orbit of Pluto and is actually spinning so rapidly that the centrifugal forces that it experiences are enough to stretch Haumea to a much more elongated shape. But beyond Haumea, beyond the solar system, beyond the galaxy, the search for strange shapes extends into the depths of space. There, the ancients viewed a fuzzy patch among the stars of the constellation Andromeda. They were perplexed by what it was, scarcely knowing it would one day help solve a fundamental mystery to reveal the ultimate true size of the universe.
More an a thousand years ago, stargazers identified something strange among the stars of the constellation Andromeda. Neither a star, a planet, nor a comet, it was an indistinct smudge and a mystery unsolved for centuries. My favorite strange shape in the sky is the Andromeda Nebula. That's what people used to call it, 'cause they just saw this smudge, and they used the word for "cloud," "nebula." Stranger still, the first telescopic photo in 1888 showed its oval form with spiral arms. No one realized that the intriguing Andromeda Nebula would upend humanity's view of the universe. Initially, the entire universe was thought to consist of our galaxy. All the stars in our galaxy, all the stars we see in the sky, everybody thought, Well, that's just it. One of the puzzles about what were called nebulae at the time was, exactly what they were and where were they? How far away were they? Was the Andromeda Nebula relatively near or impossibly far?
The key clue came in 1908, from Henrietta Leavitt, one in a team of women paid 25 an hour at Harvard Observatory to analyze telescope photographs on glass plates. Henrietta Leavitt had spent a lot of time studying particular types of variable stars, how those stars changed their brightness. These so-called variable stars expand and contract in a regular cycle, almost as if they are breathing, getting brighter and dimmer, brighter and dimmer. Leavitt discovered that you can tell how bright certain types of variable stars are by how fast they're pulsing. The slower the pulse, the greater their overall brightness. If two variable stars are pulsing with the same cycle, we know that they have the same overall brightness. Now take one of them and move it far away. It looks dimmer to our eye, but by counting the pulses, we know it's as bright as the near star. So we can use that difference in apparent brightness to calculate how far away it is. Legendary astronomer Edwin Hubble then took up the detective work.
On October 5, 1923, he examined the Andromeda Nebula and detected a variable star that has been called "the star that changed the universe." Counting the pulses, he figured its distance, which is now known to be 2.5 million light-years away. The distance seemed impossibly large, so large, in fact, that it led to only one conclusion. It turns out that the Andromeda Nebula is a galaxy full of stars. It's another galaxy that's even bigger than our own galaxy. In fact, the mysterious little cloud of the ancients was not alone. Telescopes revealed others like it, each of which was also a galaxy. The universe had billions of them. When we learned that Andromeda was outside our galaxy, it was a revolution in our understanding in our place in the universe, so this strangely shaped nebula that no one knew what it was really held the key to unlocking a universe of galaxies.
Today, astronomers marvel at the number of galaxies observed in the cosmos. Some of their strangest shapes are caused when two galaxies come close together and are twisted or distorted by gravity. - In some cases, they end up looking very peculiar, like there's the Tadpole Galaxy that has a galaxy with a long tail, looks like a pollywog. There are the Mice, two galaxies with two tails sticking out. There's the Antennae Galaxy, again, two galaxies with two antennae sticking out.
We live in a universe full of strangely shaped galaxies, each populated by strangely shaped asteroids, comets, and nebulas, and full of planets covered the strangely shaped rocks. From our ancient ancestors seeing a face on the moon to modern scientists spotting a giant hexagon on Jupiter, the heavens have concealed mysteries across time and at every scale. - Maybe the most grand structure in the universe is this filamentary web structure that connects all the galaxies together. It's like the scaffolding of the universe, maybe the skeleton of the universe. The latest version of the cosmic skeleton is generated by the Illustris Project, a massive supercomputer simulation. Like the diagrams and models of the celestial sphere created by our ancestors, it essentially encompasses the entire visible universe. Breathtaking in scope, it displays the structure of the cosmos in minute detail. It is a big-picture view of literally everything we can see, and in a universe of strange shapes, it is surely the strangest shape of them all.
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