When most people think of glass, their mind probably jumps straight to windows. And perhaps they’ve heard that old myth - that glass is actually a liquid, not a solid.
So what is glass?
Well, you’ve probably seen something like this before:
The three common phases of matter - gas, liquid, and solid. But you’ll notice that the solid picture is labeled crystalline state. Most people consider glass to be a solid, but it doesn’t quite look like that.
Crystals have a well defined structure, exhibiting long-range order. Glass is what’s called an amorphous material, exhibiting only short-range order.
Basically, glass is a different kind of solid:
The quartz shown above is an example of a crystalline material. The molecules of glass on the other hand are disordered - yet still solid.
To create glass, the liquid melt has to be cooled fast enough to prevent the substance from crystallizing. This fast cooling locks the atoms or molecules in the disordered state that looks like the liquid phase.
Characterizing a substance as a glass also means that this glass transition is reversible.
While most glass is optically transparent, the properties depend on the composition of the glass. Most of what you see every day is soda-lime-silicate glass, but there are many different kinds of glasses, including sodium borosilicate glass (Pyrex), lead-oxide glass, and aluminosilicate glass.
Sources: x x
The ocean is where the aliens live.
Transcript under the cut.
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Two years ago today (July 14), our New Horizons spacecraft made its closest flyby of Pluto…collecting images and science that revealed a geologically complex world. Data from this mission are helping us understand worlds at the edge of our solar system.
The spacecraft is now venturing deeper into the distant, mysterious Kuiper Belt…a relic of solar system formation…to reach its next target. On New Year’s Day 2019, New Horizons will zoom past a Kuiper Belt object known as 2014 MU69.
The Kuiper Belt is a disc-shaped region of icy bodies – including dwarf planets such as Pluto – and comets beyond the orbit of Neptune. It extends from about 30 to 55 Astronomical Units (an AU is the distance from the sun to Earth) and is probably populated with hundreds of thousands of icy bodies larger than 62 miles across, and an estimated trillion or more comets.
Nearly a billion miles beyond Pluto, you may be asking how the spacecraft will function for the 2014 MU69 flyby. Well, New Horizons was originally designed to fly far beyond the Pluto system and explore deeper into the Kuiper Belt.
The spacecraft carries extra hydrazine fuel for the flyby; its communications system is designed to work from beyond Pluto; its power system is designed to operate for many more years; and its scientific instruments were designed to operate in light levels much lower than it will experience during the 2014 MU69 flyby.
During its encounter, the New Horizons spacecraft collected more than 1,200 images of Pluto and tens of gigabits of data. The intensive downlinking of information took about a year to return to Earth! Here are a few things we’ve discovered:
Pluto Has a Heart
This image captured by New Horizons around 16 hours before its closest approach shows Pluto’s “heart.” This stunning image of one of its most dominant features shows us that the heart’s diameter is about the same distance as from Denver to Chicago. This image also showed us that Pluto is a complex world with incredible geological diversity.
Icy Plains
Pluto’s vast icy plain, informally called Sputnik Planitia, resembles frozen mud cracks on Earth. It has a broken surface of irregularly-shaped segments, bordered by what appear to be shallow troughs.
Majestic Mountains
Images from the spacecraft display chaotically jumbled mountains that only add to the complexity of Pluto’s geography. The rugged, icy mountains are as tall as 11,000 feet high.
Color Variations
This high-resolution enhanced color view of Pluto combines blue, red and infrared images taken by the New Horizons spacecraft. The surface of tPluto has a remarkable range of subtle color variations. Many landforms have their own distinct colors, telling a complex geological and climatological story.
Foggy Haze and Blue Atmosphere
Images returned from the New Horizons spacecraft have also revealed that Pluto’s global atmospheric haze has many more layers than scientists realized. The haze even creates a twilight effect that softly illuminates nightside terrain near sunset, which makes them visible to the cameras aboard the spacecraft.
Water Ice
New Horizons detected numerous small, exposed regions of water ice on Pluto. Scientists are eager to understand why water appears exactly where it does, and not in other places.
Stay updated on New Horizons findings by visiting the New Horizons page. You can also keep track of Pluto News on Twitter via @NASANewHorizons.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
2016 has been a great year for FYP!
And we would like to conclude it with some of the best posts that we have been able to produce
Part - I , II, III
Thank you so much following us ! Have a great weekend :D
- Fuck Yeah Physics!
First synthesized in the late 1800s, aluminum nitride’s potential wasn’t realized until a hundred years later in the late 1900s. AlN is a ceramic with high thermal conductivity but is an electrical insulator. It is classified as a covalent compound, the only stable compound in the binary Al-N system.
AlN is similar in properties to beryllium oxide (BeO), but is cheaper and has less of a potential to be toxic. In addition to the properties mentioned above, this ceramic also has high chemical resistance and exhibits piezoelectric properties.
Thanks to its thermal and electrical conductivity properties, AlN is useful in microelectronics. It is used in microelectronic packaging, surface acoustic wave sensors, in RF filters, as a crucible for the growth of gallium arsenide crystals, in piezoelectric MEMs applications, and many more. In addition, the wurtzite phase of aluminum nitride, w-AlN, is a wide band gap semiconductor material, with potential applications in deep ultraviolet optoelectronics.
Because AlN is a covalent compound, high pressures or sintering aids are required to assist densification during production. Typical additives include rare-earth or alkaline-earth oxides, such as yttrium compounds. The additives and sintering conditions used can alter the properties of commercially available grades of AlN.
Sources: ( 1 ) ( 2 - images 2 and 3 ) ( 3 - images 1 and 4 ) ( 4 )
This is the type of engine that you find in your quotidian car. Nothing fancy, just all pistons arranged parallel along the vertical direction.
Now, this is the sort of the engine that you find on sports cars like the Ferrari. When you hear sports enthusiasts go ‘ Whoa, that’s a V-12! ‘ - it just means that the engine has a V-type arrangement with 12 cylinders.
Commonly referred to as the VR engine.
The name VR6 comes from a combination of V engine (German: V-Motor), and the German word “Reihenmotor” (meaning “inline engine” or “straight engine”)
Volkswagen’s VR6 engines, and the later VR5 variants, are a family of internal combustion engines, characterized by a narrow-angle (10.5° or 15°) V engine configuration.
a: straight engine, b: V engine, c: VR engine
A W engine is a type of reciprocating engine ( again created by Volkswagen) arranged with its cylinders in a configuration in which the cylinder banks resemble the letter W, in the same way those of a V engine resemble the letter V.
A W16 engine is used on the Bugatti Veyron. That’s 16 cylinders!
Flat engines offer several advantages for motorcycles, namely: a low centre of gravity, smoothness, suitability for shaft drive, and (if air-cooled) excellent cooling of the cylinders. You can find them on aircrafts as well
They were used mostly in small aircraft for the propeller
The big advantage of radials was their large frontal area, which meant they could be air cooled, meaning less maintenance, failures, and of course a lower cost of initial purchase and maintenance.
This engine has only 3 moving parts and can make a lot of power.However, they are pretty inefficient, the last car to use this was a Mazda RX-8.
The axial engine is a very interesting design. But they are not widely used because they are just hard to make and running these things at high RPM’s is a challenge.
Duke engines are equipped with this type.
Commonly jet engines refer to the engines that are found on, well Jets!
Suck,squeeze,bang and blow
Air is sucked in through the front and squeezed. A controlled explosion follows and the exhaust is blown out through the back
But, Jet engines also include the engines that are found on rockets, hybrids and water-jets. And their mode of operation is different than the one mentioned above.
Pretty cool eh?
Have a great day!
PC: Howstuffworks, Duke, MichaelFrey, Azure.km
** There is also the Stirling Engine. It’s amazing and a topic for an another post. But if you are interested do check out more about it here.
EDIT : Had forgotten about the VR and the W-engines. My bad! Thanks for pointing it out.:D.
EDIT2: The suck squeeze bang and blow illustration was incorrect. Ergo, changed that.
This is how scientists think birds see the Earth’s magnetic field.
See how the black patches align over certain areas? That dark patch at the base of their vision shows South, with the reverse indicating North. Researchers think this might be how birds like pigeons can use magnetic fields to navigate.
Here’s how it works: there’s a protein in their eyes called cryptochrome. When blue light hits it, it becomes active, and stays active for a little while. How long it stays active for, though, depends on the Earth’s magnetic field, and since cryptochrome is known to affect the sensitivity of the birds’ retinas to light, we think this is the effect it has on their vision.
We have this very same molecule in our eyes, but the molecule that lets it stay active for long enough to be affected by the magnetic field, superoxide, is toxic, so the antioxidants in our eyes lock it down too quickly. Researchers think we’ve traded longevity for magnetovision.
Want to know more? We made a whole video answering the question, do blind birds can navigate!? Watch it here: https://youtu.be/7yBMUrlpe5s
There’s one last complication to consider with fluctuating stresses. When we looked at the case of fully reversed stresses (that is, σ_m = 0, σ_a ≠ 0) we found a fatigue stress concentration factor based on the stress concentration factor for a static situation.
With a fluctuating stress, the situation is a little different. Since the mean stress is non-zero, the part is always under some kind of load. We can consider the effects of this constant mean stress separately from the effects of the momentary alternating stress and assign them a separate fatigue stress concentration factor, which we’ll call K_fm.
Let’s think about what’s actually physically happening to a part being subjected to a fluctuating stress. Let’s say we’re dealing with a plate with a slot in it subjected to fluctuating tension.
There’s obviously a large stress concentration at the slot that we’ll have to take into account.
There’s three different scenarios which can occur here. The first is that the maximum stress the plate sees (the largest value of combined mean and alternating stress, taking stress concentrations into account) never approaches the yield strength of the material. The plate just stretches and contracts elastically. This isn’t really any different from our previous situation with fatigue stress concentration factors - we can use the K_f factor we got earlier here.
But suppose the yield strength is exceeded. What happens then? If the maximum stress is greater than the yield strength, then the plate must deform plastically at that point of maximum stress - the slot must widen. If the slot is wider, then the stress concentration is relieved - there’s more room for movement before the geometry stops you. If other words, the fatigue stress concentration factor is lessened.
If it’s just your maximum stress that exceeds the yield strength but your minimum stress is still below it, this localized yielding will be one-sided - you’ll get a slot that’s widened on one side, but you’ll still have some overall mean stress. If this is the case, you base your stress concentration factor on the relationship of the mean and alternating stresses to the yield strength.
If both your minimum and maximum stresses exceed the yield strength of the material, you get a situation where you’ve widened the slot as far as you can without actually breaking the part on both sides and you’re experiencing a stress of magnitude equal to the yield strength at either extreme of the fluctuation. Since you now have a fluctuation with equal and opposite extremes, your mean stress is zero - the mean fatigue stress concentration factor is zero. The scenario is now one of fully reversed loading and the mean stress drops right out of it.
At this very moment, spacecraft are surveying the solar system, from Mars, to Saturn, to Pluto and beyond. Now you can ride along to see the latest discoveries from deep space. For this week’s edition of 10 Things, we’ve assembled a toolkit of 10 essential resources for the desktop astronaut.
Or is it more of a Hitchhiker’s Guide to the Solar System? Whatever one calls it, our planets page offers quick rundowns, as well as in-depth guides, for all the major bodies in the solar system. Explore from the sun all the way to the Oort Cloud.
+ Peruse the planets + See how objects in the solar system stack up against each other
If you still haven’t tried Eyes on the Solar System, you’re missing out. This free, downloadable simulation app lets you tour the planets and track the past, current and future positions of spacecraft–all in 3D. Eyes on the Solar System uses real NASA data to help you take a virtual flight across both space and time.
+ Prepare for departure
With so much exploration underway, discoveries and new insights into the solar system come at a pace that borders on bewildering. NASA is rewriting the textbooks, literally, on a regular basis. Relax, though: there are several easy ways to stay up to date with what’s happening in space.
+ See the latest headlines + Stay connected on social media: Twitter, Facebook, Instagram + Find more top NASA social media accounts
NASA offers phone and tablet apps for star gazing, pictures, news, 3D tours, satellite tracking, live NASA TV and many other kinds of info.
+ Start downloading + See other cool apps
We’re in constant communication with spacecraft all over the solar system. The Deep Space Network is a global network of giant antenna dishes that makes it possible. With this online app, you can learn how it works – and even see which spacecraft are phoning home right now.
+ Deep Space Network (DSN) Now
Spacecraft 3D is an augmented reality (AR) application that lets you learn about and interact with a variety of spacecraft that are used to explore our solar system, study Earth and observe the universe. Print out the AR target and your camera will do the rest, making the spacecraft appear in 3D right in front of you. Learn more about these robotic explorers as they pop up on your desk, in your hand, or on your dog’s head.
+ Download Spacecraft 3D + See more cool 3-D resources from NASA
This site will give you a 3D look at the Mars Curiosity rover, along with some of the terrain it has explored. It will even let you take the controls.
+ Experience Curiosity
But wait, there’s more. NASA offers a variety of other fascinating (and free) online experiences, all based on actual data from real missions. Here are a few to explore:
+ Mars Trek + Vesta Trek + Moon Trek
Studying the solar system makes for a compelling route into learning and teaching science, engineering and math. We have some great places to start.
+ Find resources for teachers + Build your own solar system with your classroom
After you’ve toured the far reaches of the solar system, you can always come home again. When you have spent time studying the harsh conditions on our neighboring planets, the charms of a unique paradise come into sharp focus, the place we call Earth.
+ Watch a real-time video feed from Earth orbit + See a daily global view of our planet from a million miles away + Hold the earth in your hands with the Earth Now mobile app
Follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
In this post, I would just like to highlight the fact an image can be represented in a matrix form and matrix transformations such as transpose, shearing, scaling, etc, from an image processing point of view are purely physical !
Check out this article from the klein project if this post interested you.
Have a great day!
* Interactive Felix the cat and matrix