- 3416 - RAINBOWS - messages from the gods? Physics has figured out rainbows and some other strange phenomenon the universe, from the radius of blackholes to the behavior of subatomic particles neither of which we can even see. Some of the most mysterious things of all may be those that, on the face of it, seem mundane. Take a bowl of nuts for example:
--------------------- 3416 - RAINBOWS - messages from the gods
- You'll never reach a rainbow's end. The visibility of rainbows requires distance between the object and the observer. Here’s how it works.
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- Rainbows consist of water droplets being struck by sunlight in a certain way. Round, transparent drops of water refract and internally reflect some sunlight towards the observer. Different wavelengths of light refract, or change angles, at different angles, so the white light of the sun is parsed into an orderly band of colors.
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- A high density of waves emerges traveling in the direction of least deviation from the entry angle, and it is these light waves that create the rainbow. The optical phenomenon depends upon you being situated a distance from the droplets, with the sun at your back.
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- In bowls of mixed nuts, the Brazil nuts always seem to be sitting on top. This seemingly mundane phenomenon is actually one of the biggest unsolved mysteries in many-body physics the science that describes large quantities of interacting objects.
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- Among an assortment of things, whether they be nuts, sedimentary deposits, or other objects of varying sizes, larger pieces rise to the top over time in spite of their greater gravitas, while smaller objects tend to sink lower in the pile over time.
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- Perhaps the small stuff is trickling through cracks. Convection currents may also play a role, as might condensation of smaller particles. All of these possibilities and a few more probably contribute to the Brazil nut effect, but no one knows which ones, or to what extent, so no successful computer simulations of the phenomenon have been made.
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- Shaving cream is but one example of a mysterious substance called foam. You have probably shaved, washed dishes, had a latte or beer, or, eaten a piece of pie topped with a puff of whipped cream. We encounter foam so often that few of us step back and fully appreciate how weird the stuff really is. Is whipped cream a solid, a liquid, or a gas?
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- Foams are typically 95 percent gas and 5 percent liquid. Somehow these add up to give them certain traits of solids, too. The gas in the foam separates the liquid to form a matrix of tiny bubbles, and if the bubbles' liquid walls are rigid enough, the foam can sometimes keep its shape.
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- However, no formula exists for predicting exactly how stiff or oozy a foam will be based on the size of its bubbles or the amount of liquid it contains. The physics of foam is poorly understood.
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- A century and a half of scientific inquiry has yet to determine why ice can make you fall down. Scientists agree that a thin layer of liquid water on top of solid ice causes its slipperiness, and that a fluid's mobility makes it difficult to walk on, even if the layer is thin. But there's no consensus as to why ice, unlike most other solids, has such a layer.
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- Theorists have speculated that it may be the very act of slipping making contact with the ice that melts its surface. Others think the fluid layer is there before the slipper ever arrived, and is somehow generated by the inherent motion of surface molecules. The surprisingly strange physics of water.
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- You may or may not have pondered why your breakfast cereal tends to clump together or cling to the sides of a bowl of milk. This “Cheerios Effect” is a clumping phenomenon that applies to anything that floats, including fizzy soda bubbles and hair particles in water after a morning shave.
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- Mathematicians were the first to explain the effect in terms of simple physics, which they did in a 2005 paper. The Cheerios Effect, they proved, results from the geometry of a liquid's surface. Surface tension makes the milk's surface cave in slightly in the middle of the bowl.
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- Because water molecules in the milk are attracted to glass, the milk's surface curves upward around the bowl's edge. For this reason, pieces of the cereal near the edge float upward along this curve, appearing as if they're clinging to the edge.
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- Because of surface tension, cereal floating in the middle of your bowl dents the milk's surface, creating a dip in it. When two pieces of cereal touch, their two dents become one, and, resting in it, they stick together.
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- But that effect does not explain how magnetic fields naturally radiate outward from the electrically charged particles that make up atoms especially electrons. In matter, the magnetic fields of electrons point in different directions, canceling each other out.
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- But when the magnetic fields all the electrons in an object align in the same direction, as occurs in many metals , a net magnetic field is generated. This exerts a force on other magnetic objects, either attracting or repelling them depending on the direction of their own magnetic fields.
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- Trying to understand magnetism on a deeper level than refrigerator decorations is essentially impossible. Physicists have come up with a theory called "quantum mechanics" that very accurately explains the behavior of particles including their magnetism there's no way to intuitively understand what the theory really means.
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- Why do particles radiate magnetic fields, what are magnetic fields, and why do they always align between two directions, giving magnets their north and south poles?
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- We just observe that when you make a charged particle move, it creates a magnetic field and two poles. We don't really know why. It's just a feature of the universe, and the mathematical explanations are just attempts of getting through the 'homework assignment' of nature and getting the answers.
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- Static buildup makes hair stand on end, as positively charged hairs repel each other. Static shocks are as mysterious as they are unpleasant. This occurs when an excess of either positive or negative charge builds up on the surface of your body, discharging when you touch something and leaving you neutralized.
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- This can occur when static electricity builds up on something else a doorknob, say which you then touch. In that case, you are the excess charge's exit route. But why all the buildup? It's unclear.
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- The common explanation says that when two objects rub together, friction knocks the electrons off the atoms in one of the objects, and these then move onto the second, leaving the first object with an excess of positively charged atoms and giving the second an excess of negative electrons. Both objects (your hair and a wool hat, ) will then be statically charged. But why do electrons flow from one object to the other, instead of moving in both directions?
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- This has never been satisfactorily explained, and a recent study found that patches of both excess positive and excess negative charge exist on statically charged objects. The entire molecules seemed to migrate between objects as they are rubbed together.
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- Rainbows form as sunlight shines on droplets of moisture in the Earth's atmosphere. The droplets act like prisms, "refracting" or separating light into its component colors and sending them shooting off at a range of angles between 40 and 42 degrees from the direction opposite the sun.
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- Rainbows are no longer scientifically mysterious. They result from the way light passes through spherical drops: it is first refracted entering each drop's surface, reflected off the back of the drops, and again refracted as it leaves the drops, with all these rebounds giving it its final angular direction. This explanation has been known since the days of the 17th century physicist Isaac Newton.
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- But imagine how mystical rainbows would have seemed before then! Because they are so beautiful and were so inexplicable they were featured in many early religions. In ancient Greece rainbows were thought to be the paths made by the messengers of the gods as they traveled between Earth and heaven.
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January 15, 2022 RAINBOWS - messages from the gods? 3416
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