SCIENCE CAPSULES

    We are going to see one of the earliest method used in cryptography to send secret messages.  It was used by Julies Caesar and hence named Caesar cipher.        Here, each letter of the message is shifted forward by 3 places in the alphabet .  That is, A will become D, B will become E and so on. For quick reference;  Plain text:    A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Cipher text: D E F G H I J K L M N O P Q R S T U V W X Y Z A B C  So the message 'Welcome to my blog' encrypted as  'ZHOFRPH WR PB EORJ'   This is technically called mono alphabetic substitution cipher.  Here a shift of +3 is used.  But we could use a shift of +1 to +25.  A person who knows the algorithm (method) can only decipher the code and retrieve the message.  Suppose someone wants to break the code and get the message,  Is there a way? Yes, there is.       ...

    If there are 60  people in a gathering, will any two persons have the same birth day?  We are doubtful. we think if there are more than 365 persons, there may be a possibility of two persons sharing same birthday.  But the statistics' answer is stunning.  Here we go.      In a coin toss, chance of getting head or tail is 50 % or 1/2.  Chance of head is 1/2 and the tail is 1/2.  Hence the total probability is 1.        In a dice throw, chance of getting '1' is 1/6 and the chance of 'not' getting '1' is 5/6 = 1-1/6 .       In a gathering, the chance for a person to have any date in a year as a birthday is 365/365=1=100%.  For another person, the chance of not having a birthday same as first person is 364/365.  For a third person, the chance of not having a birthday same as previous two persons is 363/365.  Hence the probability for not having a match (two persons ha...

Is earth a lonely planet?  Is there any other civilization in our milky way galaxy ?  These questions are answered by Drake equation .  First let us see the variables in the equation. 1. N# - There are roughly 100 billion stars in milky way  galaxy. 2. FP - 20%  to 50% have planetary system. 3. NE- 1 to 5 planets of each star have the capability to sustain life. 4. FL - 0% to 100% of the planets have the capacity to support and evolve life. 5. FI -  In 0 % to 100 % of planets, the intelligent life evolves. 6. FC - 10% to 20% of intelligent life try to communicate. 7. FL - How long the intelligent life survive and communicate? It is tough to guess.  We are communicating using radio waves for last 100 years only.  N - If we multiply all the above factors ,  we may get the probable number of intelligent and communicating civilization in our galaxy. N = N#*FP*NE*FL*FI*FC*FL Let us guess the minimum values, substitute in the equa...

Land line :      Here, microphone converts voice into electrical signals, amplified and is sent through wire.  At the other end, electrical variations are converted into sound by the speaker.  Today electrical signals are converted into laser signals and sent through glass fibers.  We know land line is the two way communication (send and receive).    Radio :  Here, electrical signals are superimposed on high frequency radio waves.  Then the radio waves are radiated from tower.  High frequency waves has high energy and they can travel to long distance.  When you put a powerful light on the top of a tower, it will spread to long distance.  Similarly, high wattage radio waves (invisible light) spread to wide area. Wireless communication had begun .  Voice only is sent over the radio.  It is a one way communication, receiving only.  At the receiving end signals are extracted from radio waves and fed to...

        The calendar mainly based on the motions of celestial bodies.    We know the time taken by the earth to go round the sun once is taken as one year.  We also know the time for the earth to spin is taken as a day.  It happens to be 365+ days in a year.  That is why, a circle is divided into 360 degrees.       Moon takes roughly 29+ days to go round the earth.  Hence 30 days average is taken as the month.  The moon revolves around the earth 12 times a year.        Seven days makes a week.  Because only seven heavenly objects were known then.  Hence the week days were named after them. Sun - Sunday, moon - Monday, mars - Tuesday, mercury - Wednesday, Jupiter - Thursday, Venus - Friday, Saturn - Saturday.      In the past, sundials (measuring time using shadow) were used to measure daytime.  It had 12 equal marks.  So we have "12 hours  day a...

    Light takes 3+  seconds to travel from the moon.  It takes 8 minutes and 17 seconds to travel from the sun. The nearest star alpha centauri is 4.37 light years away. So light propagation is not instantaneous as we experience every day.  It has finite speed 300000000 met/sec in vacuum.        When light travels in denser medium like water or glass,  it slows down.  In glass, it travels at 2*10 ^8 met/sec speed.  The ratio of speed in vacuum to the speed in glass is 1.5 and it is the refractive index of the glass.      Discovery of speed :  Ole roamer observed Jupiter through telescope.  He was able to see the shadow of its moon 'Io" on the face of Jupiter as a blackspot.  When the Jupiter was close to earth, the spot appeared at one place; when the Jupiter was far away  from the earth, the shadow appeared at another place.  From these observations, he was able to calcula...

    Cut the trunk of a age old tree.  We can see number of rings in the cross section.  Each ring is formed during a year.  The count of rings gives the age of tree.      Earth rock and meteorites that has fallen on the earth has a composition of potassium-40 and organ-40.  Potassium is the radioactive element.  It emits radiation and decays into organ.   Radioactivity never stops .  The original potassium atoms are slowly converted into organ.  By counting the number of radioactive potassium atoms and stable organ atoms, one can estimate the age of rock using this formula. N = n*e^(-R*T) N - number of radioactive atoms at present (potassium) n- Number of radioactive atoms during the formation of        rock(potassium + organ) R - Radioactive constant of potassium T - Age , time elapsed since the formation of rock. e - Maths constant      This is called radiometric...