This is a repository for all cool scientific discussion and fascination. Scientific facts, theories, and overall cool scientific stuff that you'd like to share with others. Stuff that makes you smile and wonder at the amazing shit going on around us, that most people don't notice.
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A magnetic filament of solar material erupted on the sun in late September, breaking the quiet conditions in a spectacular fashion. The 200,000 mile long filament ripped through the sun's atmosphere, the corona, leaving behind what looks like a canyon of fire. The glowing canyon traces the channel where magnetic fields held the filament aloft before the explosion. Visualizers at NASA's Goddard Space Flight Center in Greenbelt, Md. combined two days of satellite data to create a short movie of this gigantic event on the sun.
In reality, the sun is not made of fire, but of something called plasma: particles so hot that their electrons have boiled off, creating a charged gas that is interwoven with magnetic fields.
These images were captured on Sept. 29-30, 2013, by NASA's Solar Dynamics Observatory, or SDO, which constantly observes the sun in a variety of wavelengths.
Different wavelengths help capture different aspect of events in the corona. The red images shown in the movie help highlight plasma at temperatures of 90,000° F and are good for observing filaments as they form and erupt. The yellow images, showing temperatures at 1,000,000° F, are useful for observing material coursing along the sun's magnetic field lines, seen in the movie as an arcade of loops across the area of the eruption. The browner images at the beginning of the movie show material at temperatures of 1,800,000° F, and it is here where the canyon of fire imagery is most obvious. By comparing this with the other colors, one sees that the two swirling ribbons moving farther away from each other are, in fact, the footprints of the giant magnetic field loops, which are growing and expanding as the filament pulls them upward.
Astronomers using NASA data have calculated for the first time that in our galaxy alone, there are at least 8.8 billion stars with Earth-size planets in the habitable temperature zone.
There are about 200 billion stars in our galaxy, with 40 billion of them like our sun, Marcy said. One of his co-authors put the number of sun-like stars closer to 50 billion, meaning there would be at least 11 billion planets like ours.
Based on the 1-in-5 estimate, the closest Earth-size planet that is in the habitable temperature zone and circles a sun-like star is probably within 70 trillion miles of Earth, Marcy said. [Reply]
Originally Posted by sd4chiefs:
Based on the 1-in-5 estimate, the closest Earth-size planet that is in the habitable temperature zone and circles a sun-like star is probably within 70 trillion miles of Earth, Marcy said.
If we leave now we might get there by 1,000,000 A.D. [Reply]
Call it the other Golden Rule: Scientists have found that all mammals weighing more than 2.2 pounds (a kilogram) empty their full bladders in about 20 seconds.
Like many new parents, David Hu, a mechanical engineer at the Georgia Institute of Technology, has changed a lot of diapers. Unlike many new parents, however, these soggy diapers caused Hu to think about the physics of urination.
“While I was changing these diapers, I was wondering how it would be different for different animals. How much fluid would they create and how long would it take to leave the body?” Hu said. (Also see “Growing Teeth and Four More Odd Uses for Urine.”)
“The physics of urination—what the forces are and how they affect how quickly urine comes out, is not totally understood, even though it’s a really old problem.”
Although it might sound silly on the surface, urination is actually serious business in the medical and veterinary worlds, especially during the aging process. Many men get enlarged prostates as they get older, which can narrow the urethra and impede urine flow. Veterinarians have been looking for a quick and easy way to identify problems with animals’ urinary tract.
Pee Cam
First, Hu wanted to know how urination varied from species to species. The bladder of a large domestic dog can hold 1.4 liters (about 0.4 of a gallon) of fluid, or roughly the amount of a large bottle of soda. An elephant’s bladder, however, can hold 160 liters of fluid, or enough to fill three large garbage cans. Hu wanted to know how this size difference affects the urinary tract and urine flow.
Enter the pee cam. Three of Hu’s graduate students at Georgia Tech used high-speed cameras to record peeing animals at Zoo Atlanta and elsewhere.
They also measured how much pee was produced by each of these animals, which ranged from rats to jaguars to elephants. The scientists supplemented their research with YouTube videos from zoo visitors. Last, the researchers obtained measurements of the animals’ bladder and urethra widths and lengths from other researchers.
Hu and colleagues suspected that bigger animals would take longer pee breaks than smaller animals, since they had to expel larger volumes of urine. But when they began determining the urination duration of each of these animal species, that wasn’t what they found.
“Even though you have thousands of times more urine, it’s coming out in the same amount of time, which is around 20 seconds,” said Hu, whose study appeared recently on the Cornell University website arXiv. (Also see “Urine Battery Turns Pee Into Power.”)
Urination Law Explained
Urinary tract measurements helped to solve the mystery of how animals of such different sizes all pee for the same amount of time.
Larger animals not only had larger bladders, they also had longer and wider urethras. The length of the urethra increases the force of gravity on the urine, which in turn increases how fast pee flows out of the body.
A wider urethra also increases flow rate by increasing the volume of urine that can leave the body at the same time. These increases correlate with the increase in body mass, such that an elephant can empty its bladder in the same amount of time as a cat. (Also see “Turtles Urinate Via Their Mouths—A First.”)
Saying an elephant pees for the same amount of time as a domestic cat seems impressive enough, but it gets even more impressive when you consider just how much urine the elephant produces: several bathtubs’ worth. It’s like having 60 showerheads all going at full blast, Hu said.
For small mammals—those weighing less than 2.2 pounds (a kilogram)—Hu’s Universal Law of Urination wasn’t as accurate. Their urethras were so narrow and short that the surface tension of the urine slowed flow down to mere droplets. Their bladders were also much smaller, so a few drops could successfully empty the bladder. These animals, like rats and mice, can successfully urinate in less than a second.
Animals benefit from such relatively short pee breaks because such pit stops increase risk of predation, Hu noted. Faster urine flow may also help prevent urinary tract infections by flushing out the system.
Now I just have to fight the urge to bring a stopwatch with me into the bathroom. [Reply]
Hot water seems to freeze faster than cold water, known as the Mpemba effect. The effect was named after the Tanzanian student who in 1963 noticed that hot ice cream mix freezes faster than a cold one. The effect was first observed by Aristotle in the 4th century BC, then later Francis Bacon and René Descartes. Mpemba published a paper on his findings in 1969.
Theories for the Mpemba effect have included: faster evaporation of hot water, therefore reducing the volume left to freeze; formation of a frost layer on cold water, insulating it; and different concentrations of solutes such as carbon dioxide, which is driven off when the water is heated. Unfortunately the effect doesn’t always appear, and cold water often freezes faster than hot water. Until now, no one had ever worked out exactly why hot water freezes more quickly than cold.
Now a team of physicists from the Nanyang Technological University in Singapore, led by Xi Zhang, have found evidence that it is the chemical bonds that hold water together that provide the effect. Each water molecule is composed of one oxygen atom bonded covalently to two hydrogen molecules. These bonds involve atoms sharing electrons and are well understood. The separate water molecules are also bound together by weaker forces generated by hydrogen bonds. These forces occur when a hydrogen atom from one molecule of water sits close to an oxygen atom from another.
The team now suggest it is these bonds that cause the Mpemba effect. They propose that when the water molecules are brought into close contact, a natural repulsion between the molecules causes the covalent bonds to stretch and store energy. When the liquid warms up, the hydrogen bonds stretch as the water gets less dense and the molecules move further apart.
The stretching in the hydrogen bonds allows the covalent bonds to relax and shrink somewhat, which causes them to give up their energy. The process of covalent bonds giving up their energy is essentially the same as cooling, and so warm water should in theory cool faster than cold. The team’s calculations suggest that the magnitude of the covalent bond relaxation accounts for the experimental differences in the time it takes for hot and cold water to freeze. [Reply]
Didn't know whether to put this into a music thread or what, but just had an amazing example of how quirky memory is.
Started listening to Harmontown, and he had a random intro song.
I shit you not, I heard ONE drumbeat, and my brain screamed 'Sweet Pea'
Sure enough it was Tommy Roe [who I saw at World of Wheels as a teen, BTW, double bill of him and Lee Greenwood, who played two saxophones at once, IIRC this was before Proud to be an American came out, Winter 84/85].
Maybe it's a particularly distinctive drumbeat, but it was just one. And I haven't heard that song in at least 15 years.
