You need to check that your friend Bob has your correct phone number, but you cannot ask him directly. You must write the question on a card and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, besides the question, to ensure that Bob can encode the message so that Eve cannot read your phone number?
Quickly now so you can get a feeling of false greatness before being beat on the head with what follows. Like in, what letter should replace the question mark in the sequence: 1A, 3D, 5G, 7J, 9?
Feeling good? Good. Now weep uncontrollably for a while because a digital clock shows both date and time in the format hh:mm:ss month/day. It is a 24-hour clock (times range from 00:00:00 to 23:59:59) and leading zeros are allowed. If all 10 digits 0 to 9 appear on the display, what is (a) the earliest, and (b) the latest date and time in the year this could happen?
THROUGHPUT
(The late lamented layover was: “A greenhouse which is usually made of glass is designed to keep plants in a warm environment. How? No, not just through the global “greenhouse effect.”)
Unlike the global “greenhouse effect” we talk about on Earth, real greenhouses are not hot because of any radiation being trapped by the glass or transparent sheets of semi-plastic or other similar materials, but because the cooling by air circulation is greatly diminished or completely eliminated. -- Renuka Palta, Hyderabad, India
An actual greenhouse is warmer not because of the “greenhouse effect”, but by preventing convective cooling, not allowing warmed air to escape. -- U N Murthy, u_n_murthy@rediffmail.com
(The second one was: “Why do veins appear bluish or purple when actually they have blood running in them which is red to dark red in colour?”)
Veins appear blue only when seen through the skin. Inside the body, they aren’t. It’s so due to the light absorption by the skin. – Dr Vishnu Nambiar, vishnunambiar@hotmail.com
At least four different things affect the colour seen. (1) Veins carry deoxygenated blood which is darker, and absorbs more red light and reflects blue. (2) The depth at which the vein is will determine the colour perceived; too deep and it can’t be seen. (3) Very superficial small veins will appear red. (4) The skin and subcutaneous tissues absorb certain wavelengths of light differentially and so the reflected blue light is perceived in the eyes. -- Dr Shyam L, orthoshyam@gmail.com
When light falls on our skin only the blue part of light is able to pass through and reach the veins. The rest of the colours are absorbed by the skin. Hence only blue light is reflected back and so the veins appear blue. -- Venkateswaran R, venkateswaranjanaki@gmail.com
(The third problem was: “What do Twinkle Twinkle Little Star, Baa, Baa, Black Sheep and The Alphabet Song have in common?”).
Twinkle, Twinkle, Little Star, Baa, Baa, Black Sheep and the Alphabet Song have a common feature in that all these three songs are based on a tune by Wolfgang Amadeus Mozart who used this tune in 1780’s for his Twelve Variations of the classic French nursery rhyme Ah, vous dirai-je, maman. -- Shashi Shekher Thakur, shashishekher@yahoo.com
(And a word now from a sponsor who has a better solution.) Here’s a wiser guy answer to that earlier probability puzzle. On seeing the boy you could say “Oh, the last time I saw him he was so small. Now, where is your other kid?” And naturally he will say “He/she is sleeping”. And viola! -- the probability becomes 100% no matter whether the boy you saw is the elder one or not. -- Balagopalan Nair K, balagopalannair@gmail.com
BUT GOOGLE THIS NOW
1. Why does the light in a kerosene lantern become erratic when the glass globe is removed?
2. A triangle whose sides are consecutive integral lengths has all its angles acute (no angle 90 degrees or more). What could be the minimum integral area of such a triangle?
Mukul Sharma
Sharma is a scriptwriter and former editor of Science Today magazine.(mukul.mindsport@gmail.com)