My Science School

For a planet to be habitable for humans, 1) It should be at a safe distance from the Sun – should be neither too hot, nor too cold; 2) It should contain liquid water, and 3) it should have a protective atmosphere that keeps the sun’s radiation out. There is only one planet in the solar system that satisfies all these conditions and that planet is earth. The next best option is mars.

Mars has many advantages. It is very close to earth-humans can reach the Red planet in less than six months from earth. A martian day is just over 24 hours long, roughly equivalent to a day on earth. 4) Mars has an atmosphere (though a thin one) that offers protection from cosmic and the sun’s radiation. Gravity on Mars is 38% that of our Earth, which is believed by many to be sufficient for the human body to adapt to. Evidence suggests that water may exist in the sub surface all over mars. With help from technology, humans can survive on Mars, whereas the survival chances are slim on other planets and their moons.

 

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The Quadrantids

The Quadrantids give off their own New Year’s fireworks show. Compared with most other meteor showers, they are unusual because they are thought to have originated from an asteroid. They tend to be fainter with fewer streaks in the sky than others on this list.

Visibility: Between the end of December and the second week of January

The Lyrids

There are records from ancient Chinese astronomers spotting these bursts of light more than 2,700 years ago. They blaze through the sky at about 107,000 mph and explode about 55 miles up in the planet’s atmosphere. This shower comes from Comet Thatcher, which journeys around the sun about every 415 years. Its last trip was in 1861 and its next rendezvous near the sun will be in 2276.

Visibility: Between April 16 and 26

The Eta Aquariids

The Eta Aquariids are one of two meteor showers from Halley’s comet. Its sister shower, the Orionids, will peak in October. Specks from the Eta Aquariids streak through the sky at about 148,000 mph, making it one of the fastest meteor showers. Its display is better seen from the Southern Hemisphere where people normally enjoy between 20 and 30 meteors per hour during its peak. The Northern Hemisphere tends to see about half as many.

Visibility: Between April 19 and May 28

The Southern Delta Aquariids

They come from Comet 96P Machholz which passes by the sun every five years. Its meteors, which number between 10 and 20 per hour, are most visible predawn, between 2 a.m. and 3 a.m. It tends to be more visible from the Southern Hemisphere.

Visibility: From July 12 to August 23

The Perseids

The Perseids light up the night sky when Earth runs into pieces of cosmic debris left behind by Comet Swift-Tuttle. The dirty snowball is 17 miles wide and takes about 133 years to orbit the sun. Its last go-round was in 1992.

Usually between 160 and 200 meteors dazzle in Earth’s atmosphere every hour during the display’s peak. They zoom through the atmosphere at around 133,000mph and burst about 60 miles overhead.

Visibility: From mid-July to mid-August,

The Orionids

The Orionids are an encore to the Eta Aquariid meteor shower, which peaks in May. Both come from cosmic material spewed from cosmic material spewed from Halley’s comet. Since the celestial celebrity orbits past Earth once every 76 years, the showers this weekend are your chance to view the comet’s leftovers until the real deal next passes by in 2061.

Visibility: From October 2 to November 7

The Leonids

The Leonids are one of the most dazzling meteor showers and every few decades it produces a meteor storm where more than 1,000 meteor can be seen an hour. Cross your fingers for some good luck – the last time the Leonids were that strong was in 2002. Its parent comet is called Comet-Temple/Tuttle and it orbits the sun every 33 years.

Visibility: During mid-November

The Geminids

The Geminids, along with the Quadrantids that peaked in January, are thought to originate not from comets, but from asteroid-like space rocks. The Geminids are thought to have been produced by an object called 3200 Phaethon. If you manage to see them, this meteor shower can brighten the night sky with between 120 and 160 meteors per hour.

Visibility: First two weeks of December

The Ursids

The Ursids tend to illuminate the night sky around the winter solstice in the Northern Hemisphere. They only shoot around 10 to 20 meteors per hour. They appear to radiate from Ursa Minor, and come from Comet 8P/ Tuttle.

Visibility: Between December 17 and 26

 

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If you spot a meteor shower, what you’re really seeing is the leftovers of the icy comets crashing into Earth’s atmosphere. Comets are sort of like dirty snowballs: As they travel through the solar system, they leave behind a dusty trail of rocks and ice that lingers in space long after they leave. When Earth passes through these cascades of comet waste, the bits of debris – which can be as small as grains of sand – pierce the sky at such speeds that they burst, creating a celestial fireworks display.

A general rule of thumb with meteor showers: You are never watching the Earth cross into remnants from a comet’s most recent orbit. Instead, the burning bits come from the previous passes. For example, during the Perseid meteor shower you are seeing meteors ejected from when its parent comet, Comet Swift-Tuttle, visited in 1862 or earlier, not from its most recent pass in 1992.

That’s because it takes time for debris from a comet’s orbit to drift into a position where it intersects with Earth’s orbit, according to Bill Cooke, an astronomer with NASA’s Meteoroid Environment Office.

The name attached to a meteor shower is usually tied to the constellation in the sky from which they seem to originate, known as their radiant. For instance, the Orionid meteor shower can be found in the sky when stargazers have a good view of the Orion constellation.

How to watch?

The best way to see a meteor shower is to get to a location that has a clear view of the entire night sky. Ideally, that would be somewhere with dark skies, away from city lights and traffic. To maximize your chances of catching the show, look for a spot that offers a wide, unobstructed view.

Bits and pieces of meteor showers are visible for a certain period of time, but they really peak visibly from dusk to dawn on a given few days. Those days are when Earth’s orbit crosses through the thickest part of the cosmic stream. Meteor showers can vary in their peak times, with some reaching their maximums for only a few hours and others for several nights. The showers tend to be most visible after midnight and before dawn.

It is best to use your naked eye to spot a meteor shower. Binoculars or telescopes tend to limit your field of view. You might need to spend about half an hour in the dark to let your eyes get used to the reduced light. Stargazers should be warned that moonlight and the weather can obscure the shows. But if that happens, there are usually meteor livestream like the ones hosted by NASA and by Slooh.

 

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Astronauts aboard Apollo 16 installed a linear telescope called the Far Ultraviolet Camera/ Spectrograph on the moon in April 1972. The gold-plated 22-kg device mounted on a tripod was the first telescope used to make astronomical observations and take photographs of Earth in ultraviolet light from the surface of another planetary body. The astronauts brought back the film, leaving behind the telescope on the moon.

The Chinese were the next to install a robotic UV telescope on the moon in 2013, which is still functional. Operated remotely from Earth, it has observed stars, galaxies, quasars, novae, etc. Now NASA has plans of planting radio telescopes on the far side of the moon. Scientists believe that the far side of the moon being shielded from the radio signals of Earth is perfect for radio astronomy.

On Earth, there are many obstacles to observing the skies – our atmosphere, light pollution, weather, etc. In contrast, space telescopes like the Hubble and Chandra have given us brilliant images of the universe. So a telescope on the moon seems the most logical step.

An observatory on the moon has the advantage of 14 days of continuous darkness with no atmosphere or light pollution. This ensures uninterrupted and clear observation of astronomical objects.

On the other hand, the lack of atmosphere means that the linear surface experiences extreme temperature differences – the temperature can be as high as 100ºC  during the daytime and -173ºC  at night. The telescope has to be specially engineered to withstand such temperature extremes. The moon also experiences many moonquakes. Lastly, building an observatory on the moon is prohibitively expensive – it can cost more than $1 billion.

 

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My friend says semi-conductors are used in transistor radios. What is a semi-conductor?

Conductors are substances that allow heat or electricity to flow easily through them; insulators on the other hand, stop the flow of heat or electricity. In addition, there are some substances that stop the flow of electricity but become less resistant to it in some conditions and then allow electricity to pass. These are the semiconductors.

Semiconducting materials have made possible modern computers and many other important electronic devices like solar cells and transistor radios.

Two well-known semiconductors are germanium and silicon.

 

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A generator is a machine that produces electrical current by moving a wire in a magnetic field. Energy is needed to move the wire. This may come from steam, wind, moving water, or, in the case of the small generator called a dynamo that may be found on some bicycles, from the movement of human legs! Dynamos produce just enough electrical energy to power the lights of a bicycle, but this energy is not stored. If the cyclist stops pedaling, the lights dim and go out.

The windmills of a wind farm can power generators to produce electricity for hundreds of homes.

Electric Generator also called dynamo, any machine that converts mechanical energy to electricity for transmission and distribution over power lines to domestic, commercial, and industrial customers. Generators also produce the electrical power required for automobiles, aircraft, ships, and trains.

The mechanical power for an electric generator is usually obtained from a rotating shaft and is equal to the shaft torque multiplied by the rotational, or angular, velocity. The mechanical power may come from a number of sources: hydraulic turbines at dams or waterfalls; wind turbines; steam turbines using steam produced with heat from the combustion of fossil fuels or from nuclear fission; gas turbines burning gas directly in the turbine; or gasoline and diesel engines. The construction and the speed of the generator may vary considerably depending on the characteristics of the mechanical prime mover.

Nearly all generators used to supply electric power networks generate alternating current, which reverses polarity at a fixed frequency (usually 50 or 60 cycles, or double reversals, per second). Since a number of generators are connected into a power network, they must operate at the same frequency for simultaneous generation. They are therefore known as synchronous generators or, in some contexts, alternators.

Electrically powered vehicles have been in use for many years! Powering motor cars with electricity does present certain problems, as batteries are heavy and a car’s energy requirement is high. This means that the distance an electric car can travel before it is recharged may be too low for many uses. In hot countries, engineers have experimented quite successfully with supplementing a car’s battery power with solar power, using solar panels on the roof of the car.

Where vehicles can obtain electrical energy from a fixed wire or track, there is no problem about electrical supply. Electrically powered trains, such s the French train are the fastest in the world.

A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that exclusively uses chemical energy stored in rechargeable battery packs, with no secondary source of propulsion (e.g. hydrogen fuel cell, internal combustion engine, etc.). BEVs use electric motors and motor controllers instead of internal combustion engines for propulsion. They derive all power from battery packs and thus have no internal combustion engine, fuel cell, or fuel tank. BEVs include – but are not limited to – motorcycles, bicycles, scooters, skateboards, railcars, watercraft, forklifts, buses, trucks, and cars.

In 2016 there were 210 million electric bikes worldwide used daily. Cumulative global sales of highway-capable light-duty pure electric car vehicles passed the one million unit milestone in September 2016. As of the end of 2019, the world’s top selling highway legal all-electric car in history is the Nissan Leaf with global sales of 450,000 units, followed very closely by the Tesla Model 3 with 448,634 sales.

Inside many electric light bulbs is a wire called a filament, made of tungsten. When current is passed through the wire, it glows white hot, giving off light and some heat. As the oxygen has been removed from the bulb, combustion cannot take place, so the wire does not bum out immediately.

Electricity flows through a thin tungsten wire in the light bulb called the filament. The filament used in a bulb has a property called "resistance." Resistance is the amount of friction that an object will put against electricity flowing through it. A filament has a lot of resistance to electricity. As a result of this resistance, the filament heat up and start glowing, converting electrical energy to light energy. This is because of the Joule-effect, which means that resistances heat up when an electrical current runs through them. This produces light and heat illuminating its surroundings.

The brightness of the filament can be varied by changing the amount of current flowing through it (the amperage), or the voltage between ends, as the amperage is related to the voltage by Ohm's law. Also, as the filament ages, its brightness will diminish somewhat and its light will get redder and redder. Eventually, all filaments will slowly vaporize and fail due to the high temperature caused by the electricity flowing through it.

By design, a light bulb has no oxygen in it. The manufacturer fills it with an inert gas like argon or nitrogen. However, this does not prevent atoms from popping off the surface of the filament due to the intense heat. This makes the filament thinner and thinner. Eventually, it becomes so thin that it breaks. For a short period of time, the two broken ends are very close to each other, and electricity can jump across in a bright blue spark. However, the two broken ends soon fall away from each other, breaking the spark, and the bulb will light no more.

Light bulbs themselves, if used properly, are not dangerous. Although their primary function is to produce light energy, as a side effect they also produce heat.

Light bulbs are sold according to the number of watts they use - the higher the number, the brighter the bulb is, and the more energy it uses. Despite getting hot, light bulbs don't explode. However, the outer glass of a light bulb which has been on for some time is quite hot, and can cause minor burns, or the broken edges might cut the skin.

Fleming’s right-hand rule enables you to tell in which direction a current flow in a wire that is moved in a magnetic field. Hold your hand as shown and point your thumb, in the direction of motion and your first finger in the direction of the magnetic field. Your second finger will then point in the direction in which current flows in the wire.

Physicists use a hand mnemonic known as the right-hand rule to help remember the direction of magnetic forces. To form the mnemonic, first make an L-shape with the thumb and first two fingers of your right hand. Then, point your middle finger perpendicular to your thumb and index finger.

The right-hand rule is based on the underlying physics that relates magnetic fields and the forces that they exert on moving charges—it just represents an easy way for physicists to remember the directions that things are supposed to point. Occasionally a physicist will accidentally use their left hand, causing them to predict that the magnetic force will point in a direction opposite the true direction!

Moving charges

When charges are sitting still, they are unaffected by magnetic fields, but as soon as they start to move, the magnetic field pushes on them. But, the direction in which the field pushes on charges is not the same as the direction of the magnetic field lines.

We can remember this diagram using the right-hand rule. If you point your pointer finger in the direction the positive charge is moving, and then your middle finger in the direction of the magnetic field, your thumb points in the direction of the magnetic force pushing on the moving charge. When you’re dealing with negative charges—like moving electrons—the force points in the opposite direction as your thumb.

Fleming’s left-hand rule enables you to use your hand to work out the direction of motion of a current-carrying wire in a magnetic field. Hold your hand as in the picture, with the first finger pointing in the direction of the magnetic field and your second finger in the direction of the electric current. Your thumb will now point in the direction of motion of the wire.

Fleming's left-hand rule for electric motors is one of a pair of visual mnemonics, the other being Fleming’s right-hand rule (for generators). They were originated by John Ambrose Fleming, in the late 19th century, as a simple way of working out the direction of motion in an electric motor, or the direction of electric current in an electric generator.

Whenever a current carrying conductor comes under a magnetic field, there will be force acting on the conductor. The direction of this force can be found using Fleming’s Left Hand Rule (also known as ‘Fleming’s left-hand rule for motors’).

Similarly if a conductor is forcefully brought under a magnetic field, there will be an induced current in that conductor. The direction of this force can be found using Fleming’s Right Hand Rule.

In both Fleming’s left and right hand rules, there is a relation between the magnetic field, the current and force. This relation is directionally determined by Fleming’s Left Hand rule and Fleming’s Right Hand rule respectively.

These rules do not determine the magnitude but instead show the direction of any of the three parameters (magnetic field, current, force) when the direction of the other two parameters is known. Fleming’s Left-Hand rule is mainly applicable to electric motors and Fleming’s Right-Hand rule is mainly applicable to electric generators.

An electric motor uses a current and a magnetic field to create motion. A specially shaped coil of wire, called an armature, is positioned between the poles of a permanent magnet. When an electric current is fed into the wire, the coil becomes a magnet too and forces of attraction and repulsion between it and the permanent magnet cause the armature to move around its axis. A device called a commentator then reverses the current, so that the armature’s magnetic poles are reversed and it turns through 180 degrees. If the current is continually reversed, the armature is always turning on its axis. It is this motion that can be used to drive a huge number of machines, such as washing machines, hairdryers and food processors.

An electric motor creates rotational, or circular, motion. The central part of the motor is a cylinder called the armature or rotor. The armature holds the rest of the components and is also the part of the motor that spins. Around the armature is the stator, which holds insulated coils of wire, usually copper. When a current is applied to the motor, the stator generates the magnetic field that drives the armature. Depending on the design of the motor, you might also find brushes, or fine metal fibers that keep current running to the opposite side of the motor as it spins.

The basic motor runs on DC, or direct current, but other motors can run on AC, or alternating current. Batteries produce direct current, while the outlets in your home supply alternating. In order for a motor to run on AC, it requires two winding magnets that don’t touch. They move the motor through a phenomenon known as induction. These induction motors are brushless, since they don’t require the physical contact that the brush provides. Some DC motors are also brushless and instead use a switch that changes the polarity of the magnetic field to keep the motor running. Universal motors are induction motors that can use either source of power.

Now that you have the basic parts and principles, you can play with the concept at home. Make a coil from lower gauge copper wire and poke each end through an aluminum can to suspend it. Place a small, strong magnet on either side of the suspended coil to create a magnetic field. If you attach a battery to both cans using alligator clips, your coil will become an electromagnet and the copper wire rotor you created should start to spin.

Plastic materials can be shaped very efficiently by machines, so plastic objects are cheaply made in great numbers. Some people think that this has contributed to the “disposable society”, where we are inclined to throw something away when it is worn or broken, instead of trying to mend it, as would have happened in the past. They warn, too, that most plastics do not easily decay, so our thrown-away food cartons and shopping bags will remain to pollute the planet for years to come. However, plastics have also brought great benefits, playing a part in so many aspects of our lives that it is difficult now to imagine the world without them.

There has been no material more revolutionary than modern plastic. Used in almost every single industry in a vast range of ways thanks to its versatility, high durability and ability to be molded into whatever shape necessary, no material has changed (and in many ways, shaped) the world like plastic has.

Since then, plastic took over the world. Thanks to its ability to remain sterile while acting as a container, plastic was used in the formation of bottles for items such as milk, which no longer had to be delivered in glass bottles. In the food industry, plastic has had an amazing, incalculable effect. Raw meat can be kept in plastic packaging to prevent potential diseases, while the use of plastic trays to keep food fresh has helped to diminish waste in stores.

Plastic has had a profound impact on almost every industry it has touched. Medicine benefited greatly from the development of the disposable plastic syringe in 1955, for instance. In fact, if we were to swap plastic for any other material to be used in the same way, it would exponentially increase greenhouse gases being emitted. The effect plastic has had on the nascent industrial world cannot be denied.

Basically, plastics are lightweight, inexpensive and high in quality. Before, buckles are made of metal and are heavier compared to the quick release buckles we use today. Weight really matters a lot in any industry because of storage and shipping issues. It is far easier and lighter to ship plastic buckles than metal buckles, making it more ideal for manufacturers, suppliers, and dealers alike.

Although plastics are considered cheaper, we cannot deny the quality it can offer. Aside from the fact that it is easier to store and ship, manufacturing plastics allow for more flexibility and creativity of the part of plastic manufacturers. Since it is highly malleable, plastics are very easy to customize so practically, any design brought to mind can be manufactured in no time at all!

Take for example plastic spoons and forks. If you will account the cost of damaged or lost utensils, values are probably going to stack up but if you will be using the plastic type, it would the most economical option. Aside from that, you don’t have to wash it with soap and water again and again because it is disposable. Same economics may be applied to quick release buckles too.

Another reason why plastics are preferred over metal is due to is hygienic qualities. It helps prevent the spread of diseases due to improperly cleaned metal cutlery. Now that you know the advantages of using plastics, can you imagine a day in your life without using it more than once? Is it even possible to run your day without it?

Starch, rubber, wool, silk and hair are all natural polymers. Their molecular structure, under the right conditions, makes them strong and flexible.

A polymer is basically synthesized by joining small molecules or substances into a single giant molecule by a chemical process. The small molecules which are used in synthesizing a polymer are called as monomer. Natural Polymers are those substances which are obtained naturally. These polymers are formed either by the process of addition polymerization or condensation polymerization.

Polymers are extensively found in nature. Our body too is made up of many natural polymers like nucleic acids, proteins, etc. The Cellulose is another natural polymer which is a main structural component of the plants. Most of the natural polymers are formed from the condensation polymers and this formation from the monomers, water is obtained as a by-product.

Latex is known to be a kind of rubber, and rubber is a natural polymer. This latex occurs in both the forms either synthetic or natural. The natural form of latex is mainly collected from the rubber trees and it is also found in variety of plants which includes the milkweed. It can also be prepared artificially by the process of building up long chains of molecules of styrene.

Natural rubber, also called by other names of India rubber, latex, Amazonian rubber, caucho, as initially produced, consists of polymers of the organic isoprene, with minor impurities of other organic compounds, plus water. Thailand and Indonesia are two of the leading rubber producers. Types of polyisoprene that are used as natural rubbers are classified as elastomers.

Currently, rubber is harvested mainly in the form of the latex from the rubber tree or others. The latex is a sticky, milky colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called “tapping”. The latex then is refined into rubber that is ready for commercial processing. In major areas, latex is allowed to coagulate in the collection cup. The coagulated lumps are collected and processed into dry forms for marketing.

Some plastics, such as polythene, can be melted and reshaped over and over again. These plastics are recyclable and are called thermoplastics. Other plastics are more resistant to heat and cannot be melted and reshaped. They are known as thermoset. Plastic kitchen work-surfaces and the hard plastic casings around some electrical goods are made from thermoset.

Though thermoset plastics and thermoplastics sound similar, they have very different properties and applications. Understanding the performance differences can help you make better sourcing decisions and improve your product designs.

The primary physical difference is that thermoplastics can be remelted back into a liquid, whereas thermoset plastics always remain in a permanent solid state. Think of thermoplastics as butter – butter can be melted and cooled multiple times to form various shapes. Thermoset is similar to bread in that once the final state is achieved, any additional heat would lead to charring.

Thermoset

Thermoset plastics contain polymers that cross-link together during the curing process to form an irreversible chemical bond. The cross-linking process eliminates the risk of the product remelting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances.

Thermoset plastics significantly improve the material’s mechanical properties, providing enhances chemical resistance, heat resistance and structural integrity. Thermoset plastics are often used for sealed products due to their resistance to deformation.

Thermoplastics

Thermoplastics pellets soften when heated and become more fluid as additional heat is applied. The curing process is completely reversible as no chemical bonding takes place. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties.

There are multiple thermoplastic resins that offer various performance benefits, but most materials commonly offer high strength, shrink-resistance and easy bendability. Depending on the resin, thermoplastics can serve low-stress applications such as plastic bags or high-stress mechanical parts.

Plastic may be shaped in various ways. It can be extruded (pushed through a nozzle when liquid) to form sheets, tubes and fibers. Molten plastic can be poured into moulds. Vacuum forming is a way of making complicated plastic shapes. A sheet of warm plastic is placed over a mould, and then the air is sucked from under it so that the sheet is pulled firmly against the sides of the mould. When the plastic is cooled, it retains the mould’s shape. Disposable cups are often made in this way.

Metalworking using machines and machine tools includes cutting using a lathe, plastic forming, and welding. When grouped with other such metalworking techniques, plastic forming is also called stamping and makes the designed shapes by pressing the material into a die. This processing method utilizes the plasticity—the characteristic that a material remains in the shape it is changed to by the application of a certain force—of metals and other solids. Plastic forming is primarily used in the metalworking of steel materials such as those for automobile parts. Unlike cutting with a lathe, this method does not produce chips and also allows mass production of the same parts through mold pressing.

There are two types of plastic forming: Cold-plastic forming, which is performed at ambient temperatures, and hot-plastic forming, which uses heat. When heated, metal undergoes thermal expansion and changes shape. As such, cold-plastic forming is used whenever possible and hot-plastic forming is used only when the material of the target being produced is hard.

Some examples of other types of plastic forming include forging for manufacturing nuts and bolts; extrusion, wire drawing, and pultrusion for forming wire materials and pipes; deep drawing for creating spherical surfaces in metal sheets; bending for producing leaf springs; riveting for securing assemblies in place; and shearing for cutting metal sheets.