My Science School

My friend put a little salt (the coarse variety) on the table, and then mixed some pepper in it. He asked me if I could separate the two.

I said it was impossible. He rubbed a plastic spoon with a piece of woollen cloth, and held it an inch or so above the mixture. The pepper jumped up to the spoon and stuck to it. In this way, he separated the pepper from the mixture.

Why did this happen?

 The spoon had got negatively charged when he rubbed it with the wool. When my friend held it above the mixture, both the pepper and the salt were attracted to it, as they were uncharged bodies. The pepper being lighter flew up and got stuck to the spoon. If he had further lowered the spoon the salt too would have been pulled up to it.

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A small horseshoe magnet can pick up a pin from the ground. Does this mean that the electromagnetic force is greater than the force of gravity?The electromagnetic force is millions of times stronger than the force of gravity. Gravity, in fact, is the weakest of the four fundamental forces in the Universe. But whereas the other three forces - electromagnetism and 'strong' and weak nuclear forces - act only on the minute particles that make up atoms, gravity acts on a cosmic scale, holding whole galaxies together.

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If two solutions of different concentrations are separated by a semi-permeable membrane (that is, a membrane that allows some substances but not others to pass through), the water from the weaker solution will start moving into the stronger solution. This is the process of osmosis.

 The flow will continue till the solutions on both sides have the same concentration. When grapes are put in the thick sugar syrup, the skin of the grapes act as a semi-permeable membrane and water from the grapes moves into the sugar syrup. The grapes shrivel up as a result.

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Try it with a rubber band. Stretch a rubber band and quickly hold it against your cheek. It feels warmer. Usually when things expand, a gas or liquid, for example, they become cooler.

When a liquid (or gas) expands, it takes the energy required for expansion from the liquid itself. So the liquid becomes cooler.

When a rubber band is stretched, it is not using up its internal energy. Energy is being supplied to it from the outside (by the one who is stretching it). So its internal energy increases and its temperature rises, making it slightly warmer to the touch.

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Space junk, or space debris, is any piece of machinery or debris left by humans in space.

It can refer to big objects such as dead satellites that have failed or been left in orbit at the end of their mission. It can also refer to smaller things, like bits of debris or paint flecks that have fallen off a rocket.

Some human-made junk has been left on the Moon, too.

How much space junk is there?

While there are about 2,000 active satellites orbiting Earth at the moment, there are also 3,000 dead ones littering space. What's more, there are around 34,000 pieces of space junk bigger than 10 centimetres in size and millions of smaller pieces that could nonetheless prove disastrous if they hit something else.

How does space junk get into space?

All space junk is the result of us launching objects from Earth, and it remains in orbit until it re-enters the atmosphere.

Some objects in lower orbits of a few hundred kilometres can return quickly. They often re-enter the atmosphere after a few years and, for the most part, they'll burn up - so they don't reach the ground. But debris or satellites left at higher altitudes of 36,000 kilometres - where communications and weather satellites are often placed in geostationary orbits - can continue to circle Earth for hundreds or even thousands of years.

What risks does space junk pose to space exploration?

Fortunately, at the moment, space junk doesn't pose a huge risk to our exploration efforts. The biggest danger it poses is to other satellites in orbit.

These satellites have to move out of the way of all this incoming space junk to make sure they don't get hit and potentially damaged or destroyed.

In total, across all satellites, hundreds of collision avoidance manoeuvres are performed every year, including by the International Space Station (ISS), where astronauts live.

Space junk in numbers

2,000 active satellites in Earth's orbit

3,000 dead satellites in Earth's orbit

34,000 pieces of space junk larger than 10 centimetres

128 million pieces of space junk larger than 1 millimetre

One in 10,000: risk of collision that will require debris avoidance manoeuvres

25 debris avoidance manoeuvres by the ISS since 1999

How can we clean up space junk?

The United Nations ask that all companies remove their satellites from orbit within 25 years after the end of their mission. This is tricky to enforce, though, because satellites can (and often do) fail. To tackle this problem, several companies around the world have come up with novel solutions.

These include removing dead satellites from orbit and dragging them back into the atmosphere, where they will burn up. Ways we could do this include using a harpoon to grab a satellite, catching it in a huge net, using magnets to grab it, or even firing lasers to heat up the satellite, increasing its atmospheric drag so that it falls out of orbit.

Credit :  Natural History Museam

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The Surface Web contains less than 10% of the info that is on the Internet.

The Deep Web consists of websites and content that are not searchable by standard search engines such as Google If Google can find the content you are searching for, then its on the Surface Web! The Surface Web contains less than 10 per cent of the information that is on the Internet.

Most people are unaware that the Deep Webs contains benign sites. Examples are your password-protected email and bank account certain sections of paid subscription services like Netflix and sites that can be accessed only through an online form. The Deep Web is estimated to be many many times larger than the Surface Web.

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Io or Jupiter I, is the innermost and third-largest of the four Galilean moons of the planet Jupiter. Slightly larger than Earth’s moon, Io is the fourth-largest moon in the Solar System, has the highest density of any moon, the strongest surface gravity of any moon, and the lowest amount of water (by atomic ratio) of any known astronomical object in the Solar System. It was discovered in 1610 by Galileo Galilei and was named after the mythological character Io, a priestess of Hera who became one of Zeus's lovers.

With over 400 active volcanoes, Io is the most geologically active object in the Solar System.

 This extreme geologic activity is the result of tidal heating from friction generated within Io's interior as it is pulled between Jupiter and the other Galilean moons—Europa, Ganymede and Callisto. Several volcanoes produce plumes of sulfur and sulfur dioxide that climb as high as 500 km (300 mi) above the surface. Io's surface is also dotted with more than 100 mountains that have been uplifted by extensive compression at the base of Io's silicate crust. Some of these peaks are taller than Mount Everest, the highest point on Earth's surface.  Unlike most moons in the outer Solar System, which are mostly composed of water ice, Io is primarily composed of silicate rock surrounding a molten iron or iron sulfide core. Most of Io's surface is composed of extensive plains with a frosty coating of sulfur and sulfur dioxide.

Io's volcanism is responsible for many of its unique features. Its volcanic plumes and lava flows produce large surface changes and paint the surface in various subtle shades of yellow, red, white, black, and green, largely due to allotropes and compounds of sulfur. Numerous extensive lava flows, several more than 500 km (300 mi) in length, also mark the surface. The materials produced by this volcanism make up Io's thin, patchy atmosphere and Jupiter's extensive magnetosphere. Io's volcanic ejecta also produce a large plasma torus around Jupiter.

Io played a significant role in the development of astronomy in the 17th and 18th centuries; discovered in January 1610 by Galileo Galilei, along with the other Galilean satellites, this discovery furthered the adoption of the Copernican model of the Solar System, the development of Kepler's laws of motion, and the first measurement of the speed of light. Viewed from Earth, Io remained just a point of light until the late 19th and early 20th centuries, when it became possible to resolve its large-scale surface features, such as the dark red polar and bright equatorial regions. In 1979, the two Voyager spacecraft revealed Io to be a geologically active world, with numerous volcanic features, large mountains, and a young surface with no obvious impact craters. The Galileo spacecraft performed several close flybys in the 1990s and early 2000s, obtaining data about Io's interior structure and surface composition. These spacecraft also revealed the relationship between Io and Jupiter's magnetosphere and the existence of a belt of high-energy radiation centered on Io's orbit. Io receives about 3,600 rem (36 Sv) of ionizing radiation per day.

Further observations have been made by Cassini–Huygens in 2000, New Horizons in 2007, and Juno since 2017, as well as from Earth-based telescopes and the Hubble Space Telescope.

Credit : Wikipedia 

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Nasa has discovered a rare and highly valuable asteroid called '16 psyche’. It was found by nasa’s hubble space telescope. The asteroid is located in our solar system’s asteroid belt between the planets of mars and jupiter.

According to a study published by the planetary science journal on monday, asteroid '16 psyche’ is located roughly 370 million kilometres (230 million miles) from the earth and measures 226 kilometres across (140 miles).

The most interesting thing about the asteroid is what it's made of. Unlike other asteroids made up of either rocks or ice, psyche is made up of metals.

One of the study's authors tracy becker said that they usually come across meteorites that have metal deposits but since psyche is made up entirely of metals, it is quite unique. 

Psyche's size and presence of metal deposits means that it could be worth $10,000 quadrillion ($10,000,000,000,000,000,000), which is equivalent to ten thousand times the global economy in 2019.

Researchers used the ultraviolet spectrum data collected by the space telescope imaging spectrograph on the hubble telescope during two observations made in 2017.

The data showed them that psyche's surface could be made of pure iron but they also found that the presence of iron composition as small as 10 percent could dominate ultraviolet reports. Psyche is believed to be the dead core of a planet that might have failed during its formative stages or it could also be the result of many violent space collisions.

Nasa has already targeted the exploration of asteroid psyche with the launch of nasa discovery mission psyche, which is expected to be launched in 2022. The psyche space probe will be sent atop a spacex falcon heavy rocket and will reach the asteroid by 2026, and hopefully uncover its exact metal content and other facets.

Credit :  India times 

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Find out from this experiment

If water is poured on a glass slab, the glass becomes wet; but if mercury is poured on the same glass surface it does not become wet. Why?

Whether a surface gets wet or not depends on

 1. The force of attraction between the molecules of the liquid and the molecules of the surface with which it is in contact, and

2. The cohesive force between the molecules of the liquid.

In the case of mercury, its molecules hold on tightly to each other. The molecules of the glass surface cannot pull them away. So the surface does not get wet.

In the case of water, the adhesive force is greater than the cohesive force between the water molecules. So the water clings to the glass surface, wetting it.

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Although we usually see only the brightly lit part of the moon during its crescent phase, we sometimes see the other part too, though dimly lit.

What's the reason?

Earth reflects the sun's light falling on it just like the  moon does. The earth, in fact, is a better reflector than the moon. The oceans which cover three-fourths of the earth's surface, reflect a lot of solar radiation back into space. So just as we have moonlight here, there is earthlight on the dark side of the moon. It is this earthlight which makes the moon beyond the crescent dimly visible to us.

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Do you enjoy an aerated soft drink? Have you noticed that the content fizzes and gushes out when you open the cap?

If I take a soft drink bottle from the fridge and open it after shaking it vigorously, the liquid spurts out. Why does it come out so forcefully after shaking?

If the liquid rushes out when a softdrink bottle is opened, it is because carbon dioxide is escaping from the water in the drink.

Carbon dioxide is introduced into the water at high pressure and cold temperatures. Besides causing the liquid to bubble when opened, a little of the carbon dioxide reacts with water to form carbonic acid which gives the drink its refreshing tangy taste.

If you shake a bottle vigorously before opening it, some of the gas in the head of the bottle above the liquid will get dissolved in the liquid. This gas is more than the water in the drink can normally dissolve and so when the bottle is opened the sudden release of pressure will cause the gas to rush out. This will bring the liquid out in a gush.

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We know that scattering of light depends on its wavelength. The shorter the wavelength, the greater the scattering. The sky appears blue because blue light is extensively scattered. Why doesn't the sky appear violet? After all, violet has the shortest wavelength in the visible spectrum and therefore it should be scattered the most

When white sunlight enters our atmosphere it is reflected in all directions by millions of tiny particles of dust or by water droplets. This is called scattering.

White light is made up of seven colours each of which has its own wavelength. The colours with the shortest wavelengths are at the blue end of the spectrum. They are scattered the most. The most scattered is violet which has the shortest wavelength in the visible spectrum.

However, we don't see the sky as violet or indigo. This is because our eyes can see blue colour better than the other two colours.

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