Most people think of dinosaurs as big, ferocious and extinct reptiles. That’s largely true, but there are some misconceptions. Dinosaurs came in all shapes and sizes. Dinosaurs were the largest land animals of all time, but a great number of dinosaurs were smaller than a turkey.
Dinosaurs first appeared between 247 and 240 million years ago. They ruled the Earth for about 175 million years until an extinction event 65.5 million years ago wiped out all of them, except for the avian dinosaurs. Scientists don’t agree entirely on what happened, but the extinction likely was a double or triple whammy involving an asteroid impact, choking chemicals from erupting volcanoes, climate change and possibly other factors.
Only the big, classic dinosaurs are extinct. Birds are living dinosaurs, most experts believe. Think of that next time a pigeon strafes you.
Fossils show that some of the more advanced dinosaurs had feathers or feather-like body covering, but many of them didn’t fly and probably didn’t even glide. Archaeopteryx, which was for a long time considered to be the first bird (although this status is not certain), could likely launch itself from the ground, but probably couldn’t fly far, according to unpublished research presented at the 2016 Society of Vertebrate Paleontology meeting in Salt Lake City, Utah. Instead, feathers, likely helped these bird-like dinosaurs stay warm as juveniles or send signals to other individuals.
Many people think extinct flying reptiles called pterosaurs were dinosaurs. They were dinosaurs’ closest relatives, but technically not dinosaurs. Pterosaurs had hollow bones, relatively large brains and eyes, and, of course, the flaps of skin extending along their arms, which were attached to the digits on their front hands. The family includes Pterodactyls, with elaborate, bony head crests and lack of teeth. Pterosaurs survived up until the mass die-off 65 million years ago, when they were going the way of the dodo along with marine reptiles and other nonavian dinosaurs.
Dinosaur fossils were first recognized in the 19th century. In 1842, paleontologist Richard Owen coined the term dinosaur, derived from the Greek deinos, meaning “terrible” or “fearfully great,” and sauros, meaning “lizard” or reptile.” Scientists classify dinosaurs into two orders — Saurischians and Ornithischians— based on the structure of the bones in their hips. (This saurischian and ornithischian grouping is now disputed. See the “Family tree update” section below to learn more.)
Most of the well-known dinosaurs — including Tyrannosaurus rex, Deinonychus and Velociraptor — fall into the order known as Saurischian dinosaurs (pronounced sor-ISK-ee-en). These “reptile-hipped” dinosaurs have a pelvis that points forward, similar to more primitive animals. They are often long-necked, have large and sharp teeth, long second fingers, and a first finger that points strongly away from the rest of the fingers.
Saurischians are divided into two groups – four legged herbivores called sauropods and two-legged carnivores called theropods (living birds are in the theropod lineage).
Theropods walked on two legs and were carnivorous. “Theropod” means “beast-footed” and they are some of the fearsome and most recognizable dinosaurs — including Allosaurus and T. rex.
Scientists have wondered whether large theropods — such as Giganotosaurus and Spinosaurus — actively hunted their prey, or simply scavenged carcasses. The evidence points to the animals working together as opportunistic hunters: they would bring down prey, but also eat animals that were lying around. When fossil-hunters found bones with bite marks on them, they wondered if theropods engaged in cannibalism. It appears now that the animals may have scavenged their own kind, but they didn’t hunt down their own.
Sauropods were herbivores with long heads, long necks, and long tails. They were among the largest land animals ever, but they likely had small brains. The gentle giants like leaf-eating Apatosaurus, Brachiosaurus and Diplodocus are part of this family.
Ornithischian (pronounced or-neh-THISK-ee-en) dinosaurs, a group that includes horned and frilled Triceratops, spiked Stegosaurus and armored Ankylosaurus, are more mild-mannered, plant eaters.
These dinosaurs were beaked herbivores. Smaller than the sauropods, the Ornithischia (meaning “bird-hipped”) often lived in herds and were prey to the larger species of dinosaurs. Interestingly, the Ornithischia shifted from a two-legged to a four-legged posture at least three times in their evolutionary history and scientists think they could adopt both postures early in their evolutionary history.
The Story of Electricity – BBC Documentary FullHD 1080p
Electricity is the physical flow of electrons, referred to as an electrical current. Electricity is an energy carrier that efficiently delivers the energy found in primary sources to end users, who in turn convert it into energy services.
Electricity is all around us–powering technology like our cell phones, computers, lights, soldering irons, and air conditioners. It’s tough to escape it in our modern world. Even when you try to escape electricity, it’s still at work throughout nature, from the lightning in a thunderstorm to the synapses inside our body. But what exactly is electricity? This is a very complicated question, and as you dig deeper and ask more questions, there really is not a definitive answer, only abstract representations of how electricity interacts with our surroundings.
Electricity is a natural phenomenon that occurs throughout nature and takes many different forms. In this tutorial we’ll focus on current electricity: the stuff that powers our electronic gadgets. Our goal is to understand how electricity flows from a power source through wires, lighting up LEDs, spinning motors, and powering our communication devices.
Electricity is briefly defined as the flow of electric charge, but there’s so much behind that simple statement. Where do the charges come from? How do we move them? Where do they move to? How does an electric charge cause mechanical motion or make things light up? So many questions! To begin to explain what electricity is we need to zoom way in, beyond the matter and molecules, to the atoms that make up everything we interact with in life.
This tutorial builds on some basic understanding of physics, force, energy, atoms, and fields in particular. We’ll gloss over the basics of each of those physics concepts, but it may help to consult other sources as well.
Channel: ADVEXON TV
Published: 2018-12-16 06:22:52
Ancient Anomalies Of Giza Academia Can’t Explain
A Collection of most of the unexplained anomalies I have previously shared on the channel which litter the Giza Plateau.
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Channel: Mystery History Back-Up Channel
Published: 2019-02-13 16:47:46
Pluto and its Moons – Space Documentary 2019 [HD]
In 2006, the International Astronomical Union, a global group of astronomy experts, established a definition of a planet that required it to “clear” its orbit, or in other words, be the largest gravitational force in its orbit.
Since Neptune’s gravity influences its neighboring planet Pluto, and Pluto shares its orbit with frozen gases and objects in the Kuiper belt, that meant Pluto was out of planet status. However, in a new study published online Wednesday in the journal Icarus, UCF planetary scientist Philip Metzger, who is with the university’s Florida Space Institute, reported that this standard for classifying planets is not supported in the research literature.
Metzger, who is lead author on the study, reviewed scientific literature from the past 200 years and found only one publication — from 1802 — that used the clearing-orbit requirement to classify planets, and it was based on since-disproven reasoning.
He said moons such as Saturn’s Titan and Jupiter’s Europa have been routinely called planets by planetary scientists since the time of Galileo.
“The IAU definition would say that the fundamental object of planetary science, the planet, is supposed to be a defined on the basis of a concept that nobody uses in their research,” Metzger said. “And it would leave out the second-most complex, interesting planet in our solar system.” “We now have a list of well over 100 recent examples of planetary scientists using the word planet in a way that violates the IAU definition, but they are doing it because it’s functionally useful,” he said. “It’s a sloppy definition,” Metzger said of the IAU’s definition. “They didn’t say what they meant by clearing their orbit. If you take that literally, then there are no planets, because no planet clears its orbit.”
The planetary scientist said that the literature review showed that the real division between planets and other celestial bodies, such as asteroids, occurred in the early 1950s when Gerard Kuiper published a paper that made the distinction based on how they were formed.
However, even this reason is no longer considered a factor that determines if a celestial body is a planet, Metzger said.
Study co-author Kirby Runyon, with Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said the IAU’s definition was erroneous since the literature review showed that clearing orbit is not a standard that is used for distinguishing asteroids from planets, as the IAU claimed when crafting the 2006 definition of planets.
“We showed that this is a false historical claim,” Runyon said. “It is therefore fallacious to apply the same reasoning to Pluto,” he said. Metzger said that the definition of a planet should be based on its intrinsic properties, rather than ones that can change, such as the dynamics of a planet’s orbit. “Dynamics are not constant, they are constantly changing,” Metzger said. “So, they are not the fundamental description of a body, they are just the occupation of a body at a current era.”
Instead, Metzger recommends classifying a planet based on if it is large enough that its gravity allows it to become spherical in shape.
“And that’s not just an arbitrary definition, Metzger said. “It turns out this is an important milestone in the evolution of a planetary body, because apparently when it happens, it initiates active geology in the body.”
Pluto, for instance, has an underground ocean, a multilayer atmosphere, organic compounds, evidence of ancient lakes and multiple moons, he said.
“It’s more dynamic and alive than Mars,” Metzger said. “The only planet that has more complex geology is the Earth.”
Channel: ADVEXON TV
Published: 2019-01-08 16:34:47
National Geographic Wild Worlds Weirdest Freaks Of Nature CONVERT HDTV XviD AFG
Channel: mido miro
Published: 2012-10-19 04:39:58