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P La N K C

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www.planck-magazine.it

I’m going to be a little scientist!

TIME

nce, Between scie ain history and br

THE HOAX Maya Calendar

NO MYSTERY AT ALL! p8

CURIOUS FACTS TIME-TRAVELLING Is it possible? p 30

The adventures of Marie and Max

The inventors of time

p 15

ISBN 9788867873326

TOWARDS THE PERFECT CALENDAR To solve the problem, the Babylonians used a trick. After the first 12 lunar years, the next seven years lasted 13 months instead of 12. After 19 years, the error was compensated. This adjustment of the calendar may seem strange, but we do the same today! In fact, every four years we add one day – February 29th. But this is a long story…

Ancient populations

The final adjustment

Many ancient calendars were based on moon phases, like the Babylonian one. To compensate for errors they added extra days, months or years when necessary.

The year calculated by Sosigene was a bit too long. Over time, the error became bigger and bigger. In the 16th century, the mathematician Luigi Lilio suggested a simple trick to solve the problem: from then on, century years are leap years only if they can be divided by 400. For example, year 2000 is a leap year, while year 1900 is not. This calendar is called “Gregorian”, because it was invented when Gregory the Great was the pope.

Caesar’s revolution When Julius Caesar got the power, the calendar was completely out of phase with the seasons. So he asked a famous astronomer, Sosigenes of Alexandria, to calculate the duration of the year. Sosigenes calculated a duration of 365 days and 6 hours. Caesar decided that one year should last 365 days.

To compensate for the 6 hours, he decided to add an extra day every four years: so Caesar invented the leap year!

rmation , we took info le ic rt a is th To write k: from the boo Calonico D ”, by avide o ic m to a è o li ed.

“Il temp Oldani, Hoep and Riccardo

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THE HOAX

: R A D N E MAYA CAL !

L L A T A Y R E T S Y M NO Some years ago, some people announced the end of the world. “It will be on December 21, 2012”, they said, “ and the date has been calculated by the Maya”.

On December 21, 2012 the world did not end. It was a hoax! Like many hoaxes, it was created by mixing scientific content with imaginary tales.

These mysterious stories can impress people.

But we can easily unravel the mystery: let us see how!

were o h W aya?

M e th

The Maya were a civilization of Central America, who flourished between 1500 b.C. and 900 a.D.. Their calendars, based on the cycles of the planet Venus and of the Sun, were very accurate. Today, the descendants of the Maya live in Mexico, Honduras, Guatemala, El Salvador and Belize.

rmation , we took info le ic rt a is th To write k: from the boo nico y Davide Calo b ”, o ic m to a ed.

“Il tempo è ldani, Hoepli O o rd a c ic R d an

D N A R EASTE N O O M E TH e t a d r e t s a E e Determin !

0 2 0 2 o t 5 1 0 2 from

Think about the following questions. When is Christmas Day? The answer is easy: it is on December 25th. And… when is Easter Day? … the answer is not so easy because Easter Day changes every year!

How can we calculate the date for Easter?

THE MAIN RULE To know when the next Easter Sunday will be, we must follow this main rule: Easter is on the first Sunday after the first full moon of Spring, that is, after the Spring equinox on March 21st.

Therefore, Easter Day depends on the moon!

NOT ONLY THE MOON BUT ALSO... MATH!

One of the methods for Easter date calculation is the “Epact rule”. The epact is the number of days from the last new moon of a year to the 1st of January of the next year.

Do you think it is too complicated? Don’t worry: follow the rules and the example and you will be able to calculate Easter date by yourself!

date of the Christian er st Ea e th e at ul lc Here we ca .

Italian public holiday Catholic religion, an

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SEARCH TODAY’S RE

THE TIME of the BRAIN “Ready... steady… GO!”. When a sprinter hears the words “Ready” and “Steady”, his brain is working. Why? To predict the moment when the starter says “GO!”.

Did you know? The sprinter does not wait until he hears the word GO! The sound takes some time to reach his ear, and he can’t wait so long to start. His brain has the ability to guess when the word GO arrives.

This function of the brain is called “predictive activity” and it is very important. It has been studied in adults, but not on children. Does their brain also have this ability?

We have asked Giovanni Mento, a researcher at the Department of General Psychology by the University of Padova.

In his laboratory there are computers, toys, and a strange cap which was made in the United States. The cap contains 100 electrodes: they collect the electrical signals from the brain and transmit them to a computer. The signals are processed in real time and converted into an electroencephalogram.

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Nicolò, Giovanni’s son, was the first to try the cap on!

M

THE INVENTORS OF TIME ONE AFTERNOON AT THE STADIUM, MAX AND GRANDMA ROSA ARE SUPPORTING MARIE IN A RUNNING RACE.

GO MARIE… GO!!!

RUN!!! GO!!!

MARIE, OVERTAKE THE OTHERS!!!

LET’S SEE THE RESULT OF THE RACE!

LOOK! MARIE IS COMING… WHAT A DISAPPOINTMENT!

OH NOOOO! FOR A VERY SHORT TIME MARIE HAS THE SECOND POSITION!

DON’T BE SAD MARIE… YOUR RUNNING RACE WAS VERY BEAUTIFUL! IT’S NOT FAIR! WE ARRIVED AT THE SAME TIME!

GRANDMA IS TRUE! BETWEEN YOU AND THE WINNER THERE ARE ONLY TWO TENTHS OF A SECOND! LOOK HERE: MY TIMER IS VERY PRECISE!

WEAR YOUR SPECIAL GLASSES AND… GO!!!

THIS IS A GOOD QUESTION, MAX! I SUGGEST TO GO FOR A TRIP TO DISCOVER THE SECRETS OF TIME MEASUREMENT IN THE PAST!

GRANDMA… NOW WE HAVE PRECISE TIMERS, BUT HOW DID THEY MEASURE TIME IN THE PAST?

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. . .

A N O P U E C N O TIME d te p o d a s d o th e m e th f o ry to is The h for the measurement of time SUNDIAL

HOURGLASS

The sundial was a clock based on the sun. It had the disadvantage of being able to work only during the day.

The first hourglasses used water, while the more recent ones use sand.

WATER CLOCKS

Ctesibio’s clock

0 300 BC

PENDULUM The first pendulum was built by Christiaan Huygens in 1656, after the death of Galileo Galilei who had the idea first.

Christiaan Huygens’s pendulum

1656 20

400 1 0 150 (Egypt) BC 300 BC and reece) (G

MECHANICAL CLOCK

dle Mid es Ag

JOHN HARRISON’S CLOCKS

WRIST WATCH

Harrison fabricated 5 models of clocks: H1, H2, H3, H4 e H5.

1910

Harrison’s model H5

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S E M I T C I ATOM

e atomic clock th : d rl o w e th in ck o precise cl Discovering the most di Ricerca Nazionale cher of the Istituto ar se re a vi, Le po lip was built. interviewed Fi PLaNCK!’s reporters fountain atomic clock m iu es ca e th e er wh in Turin, Metrologica (INRiM)

A NEW “TIME” ock, With the atomic cl th e th e de fi ni tio n of the second depends on the atomic transitions of caesium atom.

Here is the clock located at INRiM!

HISTORY

ATOMIC TRANSITIONS???

All objects and living things are made of atom s.

Each atom is made by a nucleus and arou nd it there are the electrons. When an elec tron changes its level, an atomic transition occu rs.

Atomic transitions are very fast and they allowed to measure the second in a mor e precise way. The atomic clock of INRiM uses the atomic transitions of the caesium atom .

Before...

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1879 Lord Kelvin had an idea: the atomic transitions were useful to measure time.

1949 the first atomic clock was built at the National Bureau of Standards in the United States.

1955 Louis Essen built the first accurate model of the atomic clock at the National Physical Laboratory of London, England.

1967 A new “second” was born… the atomic second!

Today... Do you know that we use the atomic clock time everyday? The WIFI and the GPS are based on the atomic time!

The caesium fountain atomic clock has a delay of 1 second in 300 million years!

...after

WHAT TIME IS IT?

!

N U S E H T IN IS R E W THE ANS Our ancestors measured the time using the sun and first clocks were fabricated in the Ancient Egypt.

These “sun clocks” have a gnomon, commonly a thin rod or a wire, that projects its shadow onto a surface.

During the day, the shadow changes its length and its position.

A clock in which the time is measured considering changes in the gnomon shadow is called sundial. The fabrication of a sundial depends also on the longitude, so it is quite complicated.

undial

tal s A horizon in) (Spa

AT THE MUSEUM...

A vertical sund ial (Germany)

You can find a lot of sundials on the walls of buildin gs in a lot of cities!

Here you can see some “sun clocks” belonging to the collection of the Museum of the History of Physics (University of Padova).

THE SHEPHERD’S CLOCK This is one of the most ancient portable clocks: it was used before 1100 AD!

EQUINOCTIAL (OR EQUATORIAL) CLOCK It is a brass clock also called “astronomical ring”.

DIPTYCH SOLAR CLOCK This clock is formed by two little ivory boards, so that it is similar to a little book. There is also a compass for the correct clock orientation.

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W NICE TO KNO

G N I L L E V A R T IS TIMEPOSSIBLE? Wouldn’t it be nice to travel in time? Exploring the past and the future and meeting incredible people? Time-travels are a really fascinating theme, and many films and books have them as a subject.

But which time-travels are possible according to the laws of physics?

In the past: NO!

In the future: YES!

Unluckily, it is not possible to travel in the past. To do this we should go faster than light, and that is not possible according to the laws of physics.

Try to imagine: you start for a one year time-travel on a spaceship at a speed that is 98% of the speed of light (it means 1 billion km/hour!). While you are away, time on Earth flows quicker: 5 years will have passed by the time you return! Therefore, you will travel 4 years in the future!

But the debate on this theme is always open. Some scientists hypothesize new options, considering some theories of general relativity (another important Einstein’s theory). But not all physicists agree on this, and there is no proof of this possibility.

But there is also another way to travel in the future: go to the border of a black hole. Here time passes slower than what happens on Earth, and it is not necessary to reach the speed of light!

Black

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hole it is an object w hich attracts everythin t o i t s e l f g and can , even light, e space an ven modify d time!

TIME S R O T A G I T INVES

How is it possible for scientists to determine when dinosaurs and other strange animals and plants lived? Here you will find all the ingredients to become a time investigator!

WHO ARE THOSE INVESTIGATORS? The particular science studying the living beings of the past is the paleontology and scientists are called paleontologists.

This strange word comes from a very old language, the Greek, and means “study of the ancient�.

SIGNS OF THE PAST Paleontologists start their studies looking at FOSSILS. They are signs, parts of animals or plants remained stamped in rocks or even transformed into rocks: leaves, shells, insects... and also sharks, dinosaurs and mammoths!

HOW OLD IS A FOSSIL? To know the age of animals and plants in the form of fossils, scientists use the dating of fossils, in other words, they try to understand the time when the organism died and was fossilized. There are two methods to do that: the relative dating and the absolute dating.

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D L R O W E H T D N U CLOCKS ARO world! the The best 10 clocks in

BIG BEN: THE SIGNATURE OF LONDON WHERE: London (England – United Kingdom)

FABRICATION: 1834-1858 The Big Ben is the bell of the Elizabeth Tower. The clock has four dials with a diameter of 8 meters, the hour hand is 2,7 meters long and minute hand is 4,3 meters long. This clock has a delay of one second every year.

SHEPHERD GATE CLOCK

WHERE: Greenwich (England – United Kingdom) FABRICATION: 1852 It is located outside the Royal Observatory of Greenwich and it is one of the first examples of electric clock. It was also one of the first clocks reporting the Greenwich mean time, according to the time system based on 24 hours.

ABRAJ AL-BAIT TOWERS (MECCA ROYAL CLOCK TOWER)

WHERE: La Mecca (Saudi Arabia) FABRICATION: 2004-2012 It is the tallest clock tower in the world: it is 610 meters tall! Also the clock is the biggest one in the world: it has 4 dials, each of them having a diameter of 43 meters.

URANIA WELTZEITUHR: THE UNIVERSAL CLOCK!

WHERE: Berlin (Germany) FABRICATION: 1969 This clock is 10 meters high. It is known as the Universal Clock, because it shows the hours of different cities of the world. At the top there is a representation of the solar system.

FLORAL CLOCKS!

DOVE: Edinburgh (Scotland – United Kingdom) FABRICATION: 1903 It was the first floral clock in the world, then fabricated in other cities and countries. The world’s largest floral clock is in Tehran, Iran. In these clocks, the flowers are changed depending on the seasons!

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MAY 2015

FEEDING THE PLANET, ENERGY FOR LIFE Let’s get ready for Expo 2015!

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