117 posts
Latest Posts by t-sci-eng - Page 4
Alloys: Wood’s Metal
Also known as Lipowtiz’s alloy as well as the commercial names of Cerrobend, Bendalloy, Pewtalloy, and MCP 158 among others, Wood’s metal is a bismuth alloy consisting of 50% bismuth, 26.67% lead, 13.33% tin, and 10% cadmium by weight. Named for the man who invented it, a Barnabas Wood, Wood’s metal was discovered/created by him in 1860.
Wood’s metal is both a eutectic and a fusible alloy, with a low melting temperature of approximately 70 °C (158 °F). While none of its individual components have a melting temperature of less than 200 °C, a eutectic alloy can be considered as a pure (homogeneous) substance and always has a sharp melting point. If the elements in a eutectic compound or alloy are not as tightly bound as they would be in the pure elements, this leads to a lower melting point. (Eutectic substances can have higher melting points, if its components bind tightly to themselves.)
Useful as a low-temperature solder or casting metal, Wood’s metal is also used as valves in fire sprinkler systems. Thanks to its low melting temperature, Wood’s metal melts in the case of a fire and thanks to the bismuth it is made from, the alloy also shrinks when it melts (bismuth, like water ice, is one of the few substances to do so) which is the key to setting off the sprinkler system. Wood’s metal is also often used as a filler when bending thin walled metal tubes: the filler prevents the tube from collapsing, then can be easily removed by heating and melting the Wood’s metal. Other applications include treating antiques, as a heat transfer medium in hot baths, and in making custom shaped apertures and blocks for medical radiation treatment.
With the addition of both lead and cadmium, however, Wood’s metal is considered to be a toxic alloy. Contact with bare skin is thought to be harmful, especially once the alloy has melted, and vapors from cadmium containing alloys are also quite dangerous and can result in cadmium poisoning. A non-toxic alternative to Wood’s metal is Field’s metal, composed of bismuth, tin, and indium.
Sources: ( 1 - image 4 ) ( 2 - image 2 ) ( 3 ) ( 4 )
Image sources: ( 1 ) ( 3 )
Solar System: Things to Know This Week
10 Tools for the Armchair Astronaut, or How to Explore the Solar System from Home
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.
1. It’s Like Facebook, but for Planets
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
2. Keep Your Eyes on This One
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
3. Dateline: Deep Space
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
4. Space? There’s an App for That
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
5. A (Very) Long Distance Call
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
6. Collect ‘Em All
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
7. Ever Wanted to Drive a Mars Rover?
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
8. More E-Ticket Attractions
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
9. The Universe Is Our Classroom
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
10. Bring It on Home
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
Discover more lists of 10 things to know about our solar system HERE.
Follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
This room starts charging your phone as soon as you walk in. Inspired by Tesla’s vision of global wireless power, scientists at Disney Research company explored how wireless charging works in large spaces. The copper pole at the room’s center sends currents through the walls and floor that charge phones and laptops without harming humans. Source Source 2
Devices can be charged regardless of their orientation in the room thanks to a new receiver design
The setup outside the room
The setup inside the room
A sponge can’t soak up mercury. (Video) Facebook | Instagram | Scary Story Website
More Than You Ever Wanted to Know About Mechanical Engineering, Part 33: Stress Concentrations With Fluctuating Stresses
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.
We started looking at fluctuating loads last time - that is, loads that feature some combination of non-zero mean and alternating stresses - and how to account for them using a Goodman diagram. Let’s re-examine the bracket design problem we did earlier. This time, instead of a fully-reversed load, we’ll assume a fluctuating load with a mean force of 200 lbs, a minimum force of 50 lbs, and a maximum force of 350 lbs. We’ll say the dimensions of the bracket are those we calculated earlier that could handle the fully reversed load. (Problem adapted from Machine Design: An Integrated Approach, 4th Ed., by Robert L. Norton.)
Most of the calculations we did earlier will still hold. We won’t need to recalculate the endurance limit or stress concentration factors. The only new things we need to do are calculate the mean and alternating stresses and the new safety factors.
First step is to calculate the mean and alternating force.
From here, we get the mean and alternating moment.
We’re dealing with a situation of simple bending, so we can calculate mean and alternating stress using the basic bending stress equation.
The geometry of the part hasn’t changed, so we’ll apply the same stress concentration factors that we used before.
Great. We’ve got our new stresses. Now we need to figure out safety factors. As we mentioned earlier, this is now a slightly more complicated proposition. Which safety factor is appropriate will depend on how the alternating and mean stress behave in relation to each other. The possible failure states are shown as points A, B, C, and D on the Goodman diagram for this situation.
We’ll step through all the possible situations one by one using the new stresses we calculated and the endurance limit we got earlier.
Case 1: Constant alternating stress, variable mean stress.
Case 2: Variable alternating stress, constant mean stress.
Case 3: Alternating and mean stress are proportional to each other.
Case 4: Alternating and mean stress vary independently.
We take the worse case, with the failure state F being as close as possible to the current stress situation.
Our design will survive all four cases. Note that Case 4 is always the most conservative case - if you don’t know what your stresses are going to do, this is the one to go with.
Hi I made this app called PhysicsPedia. It contains all the theory and formulas of high school and college physics. Please have a look. https://play.google.com/store/apps/details?id=com.pp.nikit.phyprac2
Editor’s Note:
Thank you for your submission android-nikit and we did check the app out and it is really interesting and useful. If you are in high school, we recommend you give this one a try!
Hackaday Useful Tools Links
So I am an avid reader of Hackaday for a long time now and they have been putting out a lot of great introductions to tools and processes to get makers up to speed on the resources that are available. This is just a splattering of links that I have found lately that you guys might be interested in.
DC Motors
Lessons in Small Scale Manufacturing
Grinding Gears: Figuring out gear ratios
Tools of the trade: Injection Molding
Are todays engineers worse?
How to nail a technical presentation
Tools of the trade: Vacuum Forming
The Art and Science of Bending Sheetmetal
A how-to of designing, fab, and assembly with structural framing systems (t slot)
Machine learning foundations
A machine shop in a box
How to: Cold resin casting
Join the GUI generation: Qtcreator
Do you guys have any other great resources that you’d like to share and/or are you enjoying this type of content?
Optical Properties: Negative Refraction and Metamaterials
Negative refraction isn’t something that occurs naturally in nature, it’s something scientists have created using specifically designed materials. So how do they do it?
The index of refraction, n, can be equated to the square root of the material’s relative permittivity times its relative permeability. For most materials, both these values are positive, resulting in the sort of refraction that we’re all familiar with. But, as show in the diagram below, if both the values were negative then the resulting material would have negative refraction
Metamaterials are defined as artificial materials engineered to have properties that have not yet been found in nature, and since negative refraction does not occur naturally, only metamaterials can have negative refraction.
So far, however, metamaterials have only been created that refract microwave and radio frequencies - scientists believe it is unlikely that a material will be created with negative refraction in the visible part of the spectrum.
Sources: 1 2 3 4
Image sources: 1 2 3
(Note: Images 1 and 2 are not actual photographs of negative refraction, but rather depictions of what the effect would look like, given that negative refraction has never been achieved in the visible part of the electromagnetic spectrum.)
Dude, bullets are literally made to shatter on impact. It's to prevent over-penetration. Bullets frequently shatter if they hit human bone inside a body, for example. So congrats, a katana is as good at stopping bullets as a human bone. Or a regular butter knife. Or even a regular piece of old steel. Like the ones used in a target range. Ever wonder why the steel plates at target ranges don't have holes in them even tho rifle caliber bullets hit them? It's cause the bullet shatters on impact.
To be very clear, the intention of the post was never to say that Katana is the ultimate sword. It was merely to enlighten the possibility of the bullet getting shattered by a sword/Knife.
Yes, bullets do shatter on impact.
But I am not so sure about what you say about the human bone though.
I believe it really depends on that kinetic energy of the bullet, the bullet size and the place of impact of the bullet on the body.
And even with the tissues surrounding the bone, there have been many instances where the Femur ( thigh bone ) fractured on impact.
If anyone reading this has a background in the field, would highly appreciate to hear your stance on this.
Thanks for asking anon ! :D
Why most metals are silver (but copper and gold aren’t)
If we want to understand what gives a metal its color we first need to understand a little bit about the definition of a metal. Metals are materials that experience metallic bonding - wherein the atoms are so close that there is a veritable “sea of electrons” in the substance. (This is also what makes metals conductors, but that’s another story). Basically each atom donates an electron or two that is free to flow throughout the material, unattached to any particular nucleus.
This proximity leads to an overlap in the allowed energy levels of electrons (shown in the lower left hand image above); basically the higher empty electronic levels are so close to the uppermost filled levels (also called the Fermi level) that they form an essentially continuous band of allowed energies.
Now, backtracking a little bit, color in a substance is caused when a material doesn’t absorb a particular wavelength of light. Because of the empty energy levels mentioned above, metals generally can absorb all wavelengths of light in the visible spectrum. This implies that a metal should look black, except that the excited electron can immediately fall back to the state that it came from, emitting exactly the same energy, causing a flat piece of metal to appear reflective. Thus, the reason why most metals are silver. (Also, the flatter a metal, the more reflective, thanks to diffuse vs. specular reflection).
For a few select metals, like copper and gold, the absorption and emission of photons are noticeably dependent on wavelength across the visible part of the spectrum. The graph in the lower right image above shows the reflectance of aluminum, silver, and gold, including wavelengths in the infrared and ultraviolet. Aluminum is pretty reflective overall, and silver is highly reflective in the visible region (about 400 to 700 nm), but gold clearly absorbs wavelengths about 500 nm or below. Thus, it most strongly reflects yellow, giving it its characteristic appearance.
Sources: (first image), 2 (second image), 3 (third image), 4
Composites: Papercrete
Composites are materials composed of other materials in combination, often with a matrix that binds together fibers of some kind. Papercrete gets its name from its components, paper and concrete, though it is technically composed of cement, not concrete. In papercrete, a composite of paper and cement, the cement makes up the binding matrix that holds the paper fibers together.
Paper is composed of a natural polymer, cellulose, the structure of which can be seen in the bottom image above and fibers of which can be seen in the top left and middle right images. The fibers get coated with cement, often Portland cement, and lend strength to the new material that could not be found in the cement alone. (Paper is not only made of cellulose, but it is a key component which makes papercrete possible. Aside from paper and cement, papercrete is also made with water and some form of sand or earth - other materials can be used as well, just like in concrete).
The material resulting from this mixture, papercrete, has excellent sound absorption, is flame and fungus retardant as well as bug and rodent repellent, and is relatively light. More flexible then rock or regular concrete, papercrete is useful in earthquake prone areas. Though not the best load-bearing material, papercrete is a great insulator. Like any composite however, the exact formula used to produce the material can alter the properties significantly. Adding sand or glass strengthens papercrete and makes it more flame retardant, but also increases its weight.
One of the beneficial things about papercrete is that almost any paper can be used to create it - cardboard, magazine paper, junk mail, newspaper, and other forms. Some work better than others but almost all can be used. Using waste papers such as these prevents them from entering landfills and allows paper to be recycled in a different way.
Downsides of papercrete include its lower strength and durability, as well as the fact that - as of now - there is no code or standardization to its manufacture or use, limiting the projects it can be used in. A fair amount of papercrete is made by individuals working on ‘do it yourself’ projects.
Sources: ( 1 - images 1, 2, 4, and 5 ) ( 2 ) ( 3 )
Image sources: (Middle left)
Vantablack absorbs 99% of light and is the darkest material ever made.
Solar System: Things to Know This Week
Reaching out into space yields benefits on Earth. Many of these have practical applications — but there’s something more than that. Call it inspiration, perhaps, what photographer Ansel Adams referred to as nature’s “endless prospect of magic and wonder.“
Our ongoing exploration of the solar system has yielded more than a few magical images. Why not keep some of them close by to inspire your own explorations? This week, we offer 10 planetary photos suitable for wallpapers on your desktop or phone. Find many more in our galleries. These images were the result of audacious expeditions into deep space; as author Edward Abbey said, "May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.”
1. Martian Selfie
This self-portrait of NASA’s Curiosity Mars rover shows the robotic geologist in the “Murray Buttes” area on lower Mount Sharp. Key features on the skyline of this panorama are the dark mesa called “M12” to the left of the rover’s mast and pale, upper Mount Sharp to the right of the mast. The top of M12 stands about 23 feet (7 meters) above the base of the sloping piles of rocks just behind Curiosity. The scene combines approximately 60 images taken by the Mars Hand Lens Imager, or MAHLI, camera at the end of the rover’s robotic arm. Most of the component images were taken on September 17, 2016.
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2. The Colors of Pluto
NASA’s New Horizons spacecraft captured this high-resolution, enhanced color view of Pluto on July 14, 2015. The image combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). Pluto’s surface sports a remarkable range of subtle colors, enhanced in this view to a rainbow of pale blues, yellows, oranges, and deep reds. Many landforms have their own distinct colors, telling a complex geological and climatological story that scientists have only just begun to decode.
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3. The Day the Earth Smiled
On July 19, 2013, in an event celebrated the world over, our Cassini spacecraft slipped into Saturn’s shadow and turned to image the planet, seven of its moons, its inner rings — and, in the background, our home planet, Earth. This mosaic is special as it marks the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn’s orbit, the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.
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4. Looking Back
Before leaving the Pluto system forever, New Horizons turned back to see Pluto backlit by the sun. The small world’s haze layer shows its blue color in this picture. The high-altitude haze is thought to be similar in nature to that seen at Saturn’s moon Titan. The source of both hazes likely involves sunlight-initiated chemical reactions of nitrogen and methane, leading to relatively small, soot-like particles called tholins. This image was generated by combining information from blue, red and near-infrared images to closely replicate the color a human eye would perceive.
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5. Catching Its Own Tail
A huge storm churning through the atmosphere in Saturn’s northern hemisphere overtakes itself as it encircles the planet in this true-color view from Cassini. This picture, captured on February 25, 2011, was taken about 12 weeks after the storm began, and the clouds by this time had formed a tail that wrapped around the planet. The storm is a prodigious source of radio noise, which comes from lightning deep within the planet’s atmosphere.
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6. The Great Red Spot
Another massive storm, this time on Jupiter, as seen in this dramatic close-up by Voyager 1 in 1979. The Great Red Spot is much larger than the entire Earth.
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7. More Stormy Weather
Jupiter is still just as stormy today, as seen in this recent view from NASA’s Juno spacecraft, when it soared directly over Jupiter’s south pole on February 2, 2017, from an altitude of about 62,800 miles (101,000 kilometers) above the cloud tops. From this unique vantage point we see the terminator (where day meets night) cutting across the Jovian south polar region’s restless, marbled atmosphere with the south pole itself approximately in the center of that border. This image was processed by citizen scientist John Landino. This enhanced color version highlights the bright high clouds and numerous meandering oval storms.
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8. X-Ray Vision
X-rays stream off the sun in this image showing observations from by our Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by our Solar Dynamics Observatory (SDO). The NuSTAR data, seen in green and blue, reveal solar high-energy emission. The high-energy X-rays come from gas heated to above 3 million degrees. The red channel represents ultraviolet light captured by SDO, and shows the presence of lower-temperature material in the solar atmosphere at 1 million degrees.
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9. One Space Robot Photographs Another
This image from NASA’s Mars Reconnaissance Orbiter shows Victoria crater, near the equator of Mars. The crater is approximately half a mile (800 meters) in diameter. It has a distinctive scalloped shape to its rim, caused by erosion and downhill movement of crater wall material. Since January 2004, the Mars Exploration Rover Opportunity has been operating in the region where Victoria crater is found. Five days before this image was taken in October 2006, Opportunity arrived at the rim of the crater after a drive of more than over 5 miles (9 kilometers). The rover can be seen in this image, as a dot at roughly the “ten o'clock” position along the rim of the crater. (You can zoom in on the full-resolution version here.)
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10. Night Lights
Last, but far from least, is this remarkable new view of our home planet. Last week, we released new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night from the NASA-NOAA Suomi-NPP satellite. The clouds and sun glint — added here for aesthetic effect — are derived from MODIS instrument land surface and cloud cover products.
Full Earth at night map
Americas at night
Discover more lists of 10 things to know about our solar system HERE.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
Solar System: Things to Know This Week
Reaching out into space yields benefits on Earth. Many of these have practical applications — but there’s something more than that. Call it inspiration, perhaps, what photographer Ansel Adams referred to as nature’s “endless prospect of magic and wonder.“
Our ongoing exploration of the solar system has yielded more than a few magical images. Why not keep some of them close by to inspire your own explorations? This week, we offer 10 planetary photos suitable for wallpapers on your desktop or phone. Find many more in our galleries. These images were the result of audacious expeditions into deep space; as author Edward Abbey said, "May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.”
1. Martian Selfie
This self-portrait of NASA’s Curiosity Mars rover shows the robotic geologist in the “Murray Buttes” area on lower Mount Sharp. Key features on the skyline of this panorama are the dark mesa called “M12” to the left of the rover’s mast and pale, upper Mount Sharp to the right of the mast. The top of M12 stands about 23 feet (7 meters) above the base of the sloping piles of rocks just behind Curiosity. The scene combines approximately 60 images taken by the Mars Hand Lens Imager, or MAHLI, camera at the end of the rover’s robotic arm. Most of the component images were taken on September 17, 2016.
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1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
2. The Colors of Pluto
NASA’s New Horizons spacecraft captured this high-resolution, enhanced color view of Pluto on July 14, 2015. The image combines blue, red and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC). Pluto’s surface sports a remarkable range of subtle colors, enhanced in this view to a rainbow of pale blues, yellows, oranges, and deep reds. Many landforms have their own distinct colors, telling a complex geological and climatological story that scientists have only just begun to decode.
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
3. The Day the Earth Smiled
On July 19, 2013, in an event celebrated the world over, our Cassini spacecraft slipped into Saturn’s shadow and turned to image the planet, seven of its moons, its inner rings — and, in the background, our home planet, Earth. This mosaic is special as it marks the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn’s orbit, the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.
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1280 x 800
1440 x 900
1920 x 1200
4. Looking Back
Before leaving the Pluto system forever, New Horizons turned back to see Pluto backlit by the sun. The small world’s haze layer shows its blue color in this picture. The high-altitude haze is thought to be similar in nature to that seen at Saturn’s moon Titan. The source of both hazes likely involves sunlight-initiated chemical reactions of nitrogen and methane, leading to relatively small, soot-like particles called tholins. This image was generated by combining information from blue, red and near-infrared images to closely replicate the color a human eye would perceive.
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
5. Catching Its Own Tail
A huge storm churning through the atmosphere in Saturn’s northern hemisphere overtakes itself as it encircles the planet in this true-color view from Cassini. This picture, captured on February 25, 2011, was taken about 12 weeks after the storm began, and the clouds by this time had formed a tail that wrapped around the planet. The storm is a prodigious source of radio noise, which comes from lightning deep within the planet’s atmosphere.
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
6. The Great Red Spot
Another massive storm, this time on Jupiter, as seen in this dramatic close-up by Voyager 1 in 1979. The Great Red Spot is much larger than the entire Earth.
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
7. More Stormy Weather
Jupiter is still just as stormy today, as seen in this recent view from NASA’s Juno spacecraft, when it soared directly over Jupiter’s south pole on February 2, 2017, from an altitude of about 62,800 miles (101,000 kilometers) above the cloud tops. From this unique vantage point we see the terminator (where day meets night) cutting across the Jovian south polar region’s restless, marbled atmosphere with the south pole itself approximately in the center of that border. This image was processed by citizen scientist John Landino. This enhanced color version highlights the bright high clouds and numerous meandering oval storms.
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
8. X-Ray Vision
X-rays stream off the sun in this image showing observations from by our Nuclear Spectroscopic Telescope Array, or NuSTAR, overlaid on a picture taken by our Solar Dynamics Observatory (SDO). The NuSTAR data, seen in green and blue, reveal solar high-energy emission. The high-energy X-rays come from gas heated to above 3 million degrees. The red channel represents ultraviolet light captured by SDO, and shows the presence of lower-temperature material in the solar atmosphere at 1 million degrees.
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
9. One Space Robot Photographs Another
This image from NASA’s Mars Reconnaissance Orbiter shows Victoria crater, near the equator of Mars. The crater is approximately half a mile (800 meters) in diameter. It has a distinctive scalloped shape to its rim, caused by erosion and downhill movement of crater wall material. Since January 2004, the Mars Exploration Rover Opportunity has been operating in the region where Victoria crater is found. Five days before this image was taken in October 2006, Opportunity arrived at the rim of the crater after a drive of more than over 5 miles (9 kilometers). The rover can be seen in this image, as a dot at roughly the “ten o'clock” position along the rim of the crater. (You can zoom in on the full-resolution version here.)
800 x 600
1024 x 768
1280 x 1024
1600 x 1200
1280 x 800
1440 x 900
1920 x 1200
10. Night Lights
Last, but far from least, is this remarkable new view of our home planet. Last week, we released new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night from the NASA-NOAA Suomi-NPP satellite. The clouds and sun glint — added here for aesthetic effect — are derived from MODIS instrument land surface and cloud cover products.
Full Earth at night map
Americas at night
Discover more lists of 10 things to know about our solar system HERE.
Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com
Puritans, Goths, avant-garde artists, hell-raising poets and fashion icon Coco Chanel all saw something special in it. Now black, that most enigmatic of colours, has become even darker and more mysterious.
A British company has produced a “strange, alien” material so black that it absorbs all but 0.035 per cent of visual light, setting a new world record. To stare at the “super black” coating made of carbon nanotubes – each 10,000 times thinner than a human hair – is an odd experience. It is so dark that the human eye cannot understand what it is seeing. Shapes and contours are lost, leaving nothing but an apparent abyss.
But that’s not all it can do. Microsoft and NASA teamed up to “bring” you, yes you, to Mars.
Follow @the-future-now
But that’s not all it can do. Microsoft and NASA teamed up to “bring” you, yes you, to Mars.
Follow @the-future-now
Withstanding a blast of electricity from a huge Tesla coil using a Faraday cage
A Faraday cage shields the interior from external electromagnetic radiation and electrical fields by channelling electricity through the cage, providing constant voltage on all sides of the enclosure. Since the difference in voltage is the measure of electrical potential, no current flows through the interior space of the cage. In our daily lives we are surrounded by this invention. Faraday cages can be found in microwave ovens, elevators and around our computer cables (the shield around cables such as USB’s protects the internal conductor from external electrical noise). Even in your everyday car or plane journey you are surrounded by a Faraday cage protecting you from the adverse effects of electrical fields such as lightning.
Watch the full clip in the 2016 CHRISTMAS LECTURES, ‘Supercharged: Fuelling the future’.
This Week in Chemistry: The world’s first nanocar race, and making a painkiller last longer using a metal-organic framework: https://goo.gl/TaS7HG
On the direction of the cross product of vectors
One of my math professors always told me:
Understand the concept and not the definition
A lot of times I have fallen into this pitfall where I seem to completely understand how to methodically do something without actually comprehending what it means.
And only after several years after I first encountered the notion of cross products did I actually understand what they really meant. When I did, it was purely ecstatic!
Why on earth is the direction of cross product orthogonal ? Like seriously…
I mean this is one of the burning questions regarding the cross product and yet for some reason, textbooks don’t get to the bottom of this. One way to think about this is :
It is modeling a real life scenario!!
The scenario being :
When you try to twist a screw (clockwise screws being the convention) inside a block in the clockwise direction like so, the nail moves down and vice versa.
i.e When you move from the screw from u to v, then the direction of the cross product denotes the direction the screw will move..
That’s why the direction of the cross product is orthogonal. It’s really that simple!
Another perspective
Now that you get a physical feel for the direction of the cross product, there is another way of looking at the direction too:
Displacement is a vector. Velocity is a vector. Acceleration is a vector. As you might expect, angular displacement, angular velocity, and angular acceleration are all vectors, too.
But which way do they point ?
Let’s take a rolling tire. The velocity vector of every point in the tire is pointed in every other direction.
BUT every point on a rolling tire has to have the same angular velocity – Magnitude and Direction.
How can we possibly assign a direction to the angular velocity ?
Well, the only way to ensure that the direction of the angular velocity is the same for every point is to make the direction of the angular velocity perpendicular to the plane of the tire.
Problem solved!
This is the Hollow Mask Illusion.
At first, it looks like the face is popping out towards you, but as it turns far enough, you realise that it is in fact concave, bending inwards from the base, away from you. This illusion plays on the fact that our perception is influenced by past experience; we expect faces to protrude outwards, which helps the illusion trick our brains.
You can make your own version of this mask at home, and it’s an awesome activity to try with your kids to get them thinking about the science of psychology. Click here for all the info!
You might be an engineer if you know how long a zeptosecond is. (It's a trillionth of a billionth of a second!) http://ow.ly/uUUb30caXrH
How does sand from Sahara end up in your windshield ?
TBH cleaning your car is a rather mundane task. But when you fill your head with some interesting physics the task actually gets rather pretty interesting. Here’s some good for thought on such an occasion :
The dust on your windshield might actually be from the Sahara desert
To understand how, lets start with some simple physics.
The stacked ball drop
You basically take couple of balls, align them up and drop them to the ground. The ball at the top reaches the most highest due to the subsequent transfer of energy from the other balls.
Source Video : Physics Girl
Here is an exaggerated but amazing slow motion of the same energy transfer with a water balloon. Notice how the transfer of energy takes place between the water balloon and the tennis ball.
Source Video : Slow Mo Lab
Sandstorms in the desert
Sandstorms/ Dust storms as you might be aware, are pretty common in the desert. . Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface.
And this can cause something phenomenal to happen:
If the wind speed is sufficient then larger sand particles can propel finer ones high into the atmosphere. ( just like the stacked ball )
Then these fine particles are caught in the global wind pattern and are transported across the globe until they fall down to the earth as rain.
How cool is that ! Have a great day!
* Tracking saharan dust in 3D - NASA video
** All the World’s a Stage … for Dust - NASA article
** Wiki on Saltation
Does one of these LEGO men look bigger than the other? They’re actually the exact same size, but are in an Ames room - a false-perspective illusion room that tricks your brain into thinking things are smaller, or larger, than they really are.
You can make one of these models to try this for yourself. Download our free template from here. And it even works in full size, if you can make one large enough!
Centrifugal force and seat belts
The basic concept of a seatbelt is to protect you in an automobile collision by holding you in your seat. This prevents you from flying forward and colliding with the dashboard or windshield.
How do you do that ?
Many common seat belts design have something known as a centrifugal clutch. This arrangement has a weight attached to the end of a spool
When the spool rotates at a low speed, the weight is held through spring action and is allowed to spin freely.
But you must have noticed that if you try to pull the seat belt faster then it kinda gets stuck.
This is because as you rotate the spool faster, centrifugal force causes the weight to be pushed out and that stops the spool from rotating further.
This adds tension to your seat belt and holds you to your seat at the time of a crash.
Have a great day!
* Other seatbelt mechanisms
** Seatbelt physics
1. Lungs don’t just facilitate respiration - they also make blood. Mammalian lungs produce more than 10 million platelets (tiny blood cells) per hour, which equates to the majority of platelets circulating the body.
2. It is mathematically possible to build an actual time machine - what’s holding us back is finding materials that can physically bend the fabric of space-time.
3. Siberia has a colossal crater called the ‘doorway to the underworld’, and its permafrost is melting so fast, ancient forests are being exposed for the first time in 200,000 years.
4. The world’s first semi-synthetic organisms are living among us - scientists have given rise to new lifeforms using an expanded, six-letter genetic code.
5. Vantablack - the blackest material known to science - now comes in a handy ‘spray-on’ form and it’s the weirdest thing we’ve seen so far this year.
6. It’s official: time crystals are a new state of matter, and we now have an actual blueprint to create these “impossible” objects at will.
7. A brand new human organ has been classified, and it’s been hiding in plain sight this whole time. Everyone, meet your mesentery.
8. Carl Sagan was freakishly good at predicting the future - his disturbingly accurate description of a world where pseudoscience and scientific illiteracy reigns gave us all moment for pause.
9. A single giant neuron that wraps around the entire circumference of a mouse’s brain has been identified, and it appears to be linked to mammalian consciousness.
10. The world’s rarest and most ancient dog isn’t extinct after all - in fact, the outrageously handsome New Guinea highland wild dog appears to be thriving.
11. Your appendix might not be the useless evolutionary byproduct after all. Unlike your wisdom teeth, your appendix might actually be serving an important biological function - and one that our species isn’t ready to give up just yet.
12. After 130 years, we might have to completely redraw the dinosaur family tree, thanks to a previously unimportant cat-sized fossil from Scotland.
13. Polycystic ovary syndrome might actually start in the brain, not the ovaries.
14. Earth appears to have a whole new continent called Zealandia, which would wreak havoc on all those textbooks and atlases we’ve got lying around.
15. Humans have had a bigger impact on Earth’s geology than the infamous Great Oxidation Event 2.3 billion years ago, and now scientists are calling for a new geological epoch - the Anthropocene - to be officially recognised.
16. Turns out, narwhals - the precious unicorns of the sea - use their horns for hunting. But not how you’d think.
17. Human activity has literally changed the space surrounding our planet - decades of Very Low Frequency (VLF) radio communications have accidentally formed a protective, human-made bubble around Earth.
18. Farmers routinely feed red Skittles to their cattle, because it’s a cheap alternative to corn. ¯\_(ツ)_/¯