Why do old books become yellow?
Walk into a big library, and you’ll see many old books that have become yellow and brittle. Why did that happen? How can we make them stay fresh forever?
Make your own ancient treasure map!
Draw a treasure map on a sheet of paper. Meanwhile, ask mom or dad to make you a cup of black tea (without milk or sugar). Pour the tea onto a plate, place your map in it and let it soak overnight. In the morning, take out the map carefully and let it dry in the sun. Does it now have an ancient, yellow effect? Show it to your friends and tell them that an ancient pirate gave it to you!Lignin and paper
As we know, paper is made from wood. Wood is in turn made of carbohydrates like cellulose and lignin. Lignin is a very complicated molecule that adds hardness to wood. More the lignin, hardier is the wood. However, in paper it is a problem. Over time, lignin breaks down to form many phenolic acids, which are yellow in colour. These acids then react with cellulose. This causes the paper to become very brittle.That’s what happened when you put the map in tea. There was tannic acid in the tea, which reacted with the acid in the paper.
How to make books last
William Barrow was a librarian in the 1930s, who was very interested in knowing how to preserve old books (perhaps some of them had old treasure maps!) He was the one who discovered that it was the acid from lignin that caused it.Since then, paper manufacturers remove lignin from the wood pulp before it is made into paper. These require additional chemical reactions. In addition, the paper is made alkaline by adding calcium bicarbonate. If any lignin is left in the paper, when it forms acid, the calcium bicarbonate will immediately react with it and ‘neutralise’ it. This kind of paper is called acid-free paper.
All this makes the paper expensive. Things like newspapers, tickets, notebooks etc are therefore not printed on it. But all books nowadays are printed on acid-free paper.
Why is salt used to thaw ice?
Have you seen people sprinkling salt over snow in the winter? (You might have seen it on TV) It’s used to keep the roads free of snow. It’s also the way to make ice-cream!
Freezing water
In cold countries when there is snow in winter, roads get blocked. This snow can be dangerous to vehicles, since they can skid on it. Hence the snow must be cleared off from time to time. Therefore sea-salt is sprinkled on the snow. It melts and flows away, leaving the road clear. But to understand why, we must know how water freezes into snow.When you cool water below 0°C, it freezes. During this process, the water molecules lose energy, till they stop moving about. They then become arranged in an orderly pattern, losing more heat. At this stage, crystals of ice start to appear.
When ice melts, it needs heat to first break the pattern. Then as you heat it more, the molecules start moving about, becoming a liquid.
Salt lowers the freezing point
If there are things mixed in the water, they get in the way of crystal formation. Therefore, the water does not freeze at 0°C. That’s what happens when salt is added to water. But at a lower temperature, -5°C, the sodium and chlorine ions in the salt joins the pattern. The salt solution freezes.When salt is added to snow, the above happens. If the temperature in the air is below -5°C, nothing will happen. But if it is more than that, the salt will cause the snow to melt and flow away. If you want to melt snow, but the temperature is much below -5°C, you have to use something else.
How ice-cream is made
The effect salt has on water isn’t just used for melting snow. You can use it at home to make delicious ice-cream.Try it at home. Put ice-cream mixture in a bowl, and put that in a bigger bowl. Now put ice cubes around the small bowl in the big one. Add a few spoons of salt to the ice cubes (use rock salt which is cheaper). Now keep churning the ice-cream mixture. It will take time, but you’ll see ice-cream beginning to form slowly. But remember to keep lots more ice-cubes handy.
What happens? To start with, the ice-cream mix is warmer than the ice. So the ice pulls heat away from it. Since you added salt, it makes the ice melt faster. That pulls even more heat from the ice-cream mix. That makes some more salt dissolve, making the ice melt faster. It goes on and on till the ice-cream is cooled to the temperature of the ice. But by then all the ice will have melted. So you have to put fresh ice-cubes and salt.
How do light sticks work?
If you go on a camping vacation, do pack some light sticks in your kit. They are useful for getting some light without electricity or matches. And they come in lots of colours.
Uses of light sticks
Apart from camping, light sticks are used in many other places. Scuba divers use them to look at corals reefs. They are waterproof, need no electricity or fuel, and do not produce heat. After a hurricane, earthquake or fire, it’s dangerous to switch on a light as there may be short circuits. It’s better to use a light stick then.They are also very popular as decorations in pubs and discos. Smaller versions of them are used to make crazy jewellery like light earrings, light bracelets, light necklaces, as dancing props, and for making Star Wars type lighted swords.
Glowsticking is a form of dance in which the dancer uses one or more coloured glowsticks. They trace out interesting patterns in the air, like the one in the picture.
So how do they work?
Light sticks are based on a simple chemical reaction. The most common reaction is hydrogen peroxide and phenol oxalate ester. The hydrogen peroxide is kept in a thin walled glass tube within the light stick, while the ester is outside it. When you tap or bend the light stick, the glass vial breaks. The peroxide is released into the ester.First, the peroxide reacts with it to form a peroxyacid ester. This isn’t very stable, so it decomposes further, releasing a lot of energy in the process. This energy is absorbed by a fluorescent dye that is coated on the inner wall of the stick. The dye then releases light. The colour of the light depends on the colour of the dye. Rhodamine B gives a red light, while rubrene gives a yellow light.
A CFL lamp also works on the principle of fluorescence, but the energy comes from electricity, not a chemical reaction.
Fireflies and glow-worms
Wondered how a firefly gives light as it flies through the evening air? A similar reaction happens in its body. An enzyme called luciferase oxidizes a chemical called luciferin. Light is released during this process. Fireflies use light to tell each other where they are. Female fireflies look like worms, so they are called glowworms. They cannot fly.Many creatures that live deep in the sea, like squids and anglerfish also produce light. The anglerfish produces light at the tip of a long spine that grows from its head. This light attracts prey which the fish quickly gobbles up!
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Researchers Crack the Mystery of the Spotless Sun
In 2008-2009, sunspots almost completely disappeared for two years. Solar activity dropped to hundred-year lows; Earth's upper atmosphere cooled and collapsed; the sun’s magnetic field weakened, allowing cosmic rays to penetrate the Solar System in record numbers. It was a big event, and solar physicists openly wondered, where have all the sunspots gone?
Now they know. An answer is being published in the March 3rd edition of Nature.
"Plasma currents deep inside the sun interfered with the formation of sunspots and prolonged solar minimum," says lead author Dibyendu Nandi of the Indian Institute of Science Education and Research in Kolkata. "Our conclusions are based on a new computer model of the sun's interior."
For the first time, Nandi’s team believes they have developed a computer model that gets the physics right for all three aspects of this process--the magnetic dynamo, the conveyor belt, and the buoyant evolution of sunspot magnetic fields.
"According to our model, the trouble with sunspots actually began in back in the late 1990s during the upswing of Solar Cycle 23," says co-author Andrés Muñoz-Jaramillo of the Harvard-Smithsonian Center for Astrophysics. "At that time, the conveyor belt sped up."
The fast-moving belt rapidly dragged sunspot corpses down to sun's inner dynamo for amplification. At first glance, this might seem to boost sunspot production, but no. When the remains of old sunspots reached the dynamo, they rode the belt through the amplification zone too hastily for full re-animation. Sunspot production was stunted.
Later, in the 2000s, according to the model, the Conveyor Belt slowed down again, allowing magnetic fields to spend more time in the amplification zone, but the damage was already done. New sunspots were in short supply. Adding insult to injury, the slow moving belt did little to assist re-animated sunspots on their journey back to the surface, delaying the onset of Solar Cycle 24.
"The stage was set for the deepest solar minimum in a century," says co-author Petrus Martens of the Montana State University Department of Physics.
Colleagues and supporters of the team are calling the new model a significant advance.
"Understanding and predicting solar minimum is something we’ve never been able to do before---and it turns out to be very important," says Lika Guhathakurta of NASA’s Heliophysics Division in Washington, DC.
While Solar Max is relatively brief, lasting a few years punctuated by episodes of violent flaring, over and done in days, Solar Minimum can grind on for many years. The famous Maunder Minimum of the 17th century lasted 70 years and coincided with the deepest part of Europe's Little Ice Age. Researchers are still struggling to understand the connection.
One thing is clear: During long minima, strange things happen. In 2008-2009, the sun’s global magnetic field weakened and the solar wind subsided. Cosmic rays normally held at bay by the sun’s windy magnetism surged into the inner solar system. During the deepest solar minimum in a century, ironically, space became a more dangerous place to travel. At the same time, the heating action of UV rays normally provided by sunspots was absent, so Earth’s upper atmosphere began to cool and collapse. Space junk stopped decaying as rapidly as usual and started accumulating in Earth orbit. And so on….
Nandi notes that their new computer model explained not only the absence of sunspots but also the sun’s weakened magnetic field in 08-09. "It's confirmation that we’re on the right track."
Next step: NASA’s Solar Dynamics Observatory (SDO) can measure the motions of the sun’s conveyor belt—not just on the surface but deep inside, too. The technique is called helioseismology; it reveals the sun’s interior in much the same way that an ultrasound works on a pregnant woman. By plugging SDO’s high-quality data into the computer model, the researchers might be able to predict how future solar minima will unfold. SDO is just getting started, however, so forecasts will have to wait.
Indeed, much work remains to be done, but, says Guhathakurta, "finally, we may be cracking the mystery of the spotless sun."
Credits: This research was funded by NASA’s Living With a Star Program and the Department of Science and Technology of the Government of India.
A First Look at Flight in 2025
In late 2010, NASA awarded contracts to three teams — Lockheed Martin, Northrop Grumman, The Boeing Company — to study advanced concept designs for aircraft that could take to the skies in the year 2025.
At the time of the award, the team gave NASA a sneak peek of the particular design they plan to pursue.
Each design looks very different, but all final designs have to meet NASA's goals for less noise, cleaner exhaust and lower fuel consumption. Each aircraft has to be able to do all of those things at the same time, which requires a complex dance of tradeoffs between all of the new advanced technologies that will be on these vehicles.
The proposed aircraft will also have to operate safely in a more modernized air traffic management system.
And each design has to fly up to 85 percent of the speed of sound; cover a range of approximately 7,000 miles; and carry between 50,000 and 100,000 pounds of payload, either passengers or cargo.
For the rest of this year, each team will be exploring, testing, simulating, keeping and discarding innovations and technologies to make their design a winner.
How different will the final designs look from these initial glimpses?
Each design looks very different, but all final designs have to meet NASA's goals for less noise, cleaner exhaust and lower fuel consumption. Each aircraft has to be able to do all of those things at the same time, which requires a complex dance of tradeoffs between all of the new advanced technologies that will be on these vehicles.
The proposed aircraft will also have to operate safely in a more modernized air traffic management system.
And each design has to fly up to 85 percent of the speed of sound; cover a range of approximately 7,000 miles; and carry between 50,000 and 100,000 pounds of payload, either passengers or cargo.
For the rest of this year, each team will be exploring, testing, simulating, keeping and discarding innovations and technologies to make their design a winner.
How different will the final designs look from these initial glimpses?
Credits:NASA
