Why black hole is black?

Why black hole is black?

PROF WAQAR HUSSAIN

           

                              

                              A black hole is a regions of space having extremely high density (around 10¹⁸ kg/m³; one can imagine its density by supposing that if earth is squeezed to a volume of a peanut, it will become a black hole) of a matter that result in enormous gravitational attraction, so no matter, radiation and even light cannot escape from its grasp if it comes to its range. That is why it appears black. Such regions are believed to form when a massive star collapses. So, for understanding of a common man, you can say: “It is a dead body of a star”.

           Black hole usually lies at the centre of a galaxy. A supermassive black hole Sagittarius A is lying at the centre of our Milky Way galaxy. It has a mass equal to about 4 million suns and has a size equal to the sun.

Why taxis are yellow in colour ?... SEVEN REASONS !

Why taxis are yellow in colour ?... SEVEN REASONS !

PROF WAQAR HUSSAIN

          

     There are many reasons behind yellow colours of taxis. First, the most popular reason is that John Hertz, car salesman, decided in 1907 to start a taxi business on having surplus investment. Since taxis were to stand out in swarm of other cars. It was difficult for a passenger to identify taxi. So, Hertz went for scientific solution and chosen yellow colour. His decision was based on the survey conducted by University of Chicago which concluded that “yellow was the easiest colour to spot”. Research further suggested: “the colour yellow with a bit of red mixed in was the colour most visible from distance”. He started the taxi business in Chicago, creating the Yellow Cab Company in 1915.

           Secondly, some people object the above often told story and advocate that yellow taxi had already appeared in various cities of America before 1915. A businessman Albert Rockwell was operating a fleet of yellow cabs as early as 1909. Legend behind Rockwell selection of yellow colour was to appease her wife Nettie, who preferred and liked yellow colour.

           Third, yellow colour is easy to be identified thereby avoids embarrassment of passengers and averts annoyance of private vehicle owners.

           Fourth, yellow is an uncommon colour for personal vehicles which are often in other colours like white, black, grey, brown, etc. Yellow was very infrequent so it was easier to pick a dissimilar coloured taxi.

           Fifth, some explain yellow colour in Rayleigh’s Scattering Law which says: Colours with longer wavelength experience less scattering and thus are visible even from longer distance. So, yellow colour, which is among colours of longer wavelength, was selected for taxis to be seen from a distance.

         Sixth, some say yellow is the symbol for “ready”. When you see yellow light in traffic signal, you become ready. So, taxis are painted yellow as they are “ready” to go anywhere.

        Seventh, some give reason that yellow colour doesn’t fade easily, even some other colours fades to become yellow and taxis are to stand or run in the sunlight all the time. That is why yellow colour is picked for taxis.

         What is the net outcome of above reasons; it is the unusual colour which also has properties of gleaming and visibility from a distance. Thus it became popular all over the world. However, now taxis have other colours too especially in small cities where just plate of taxi is sufficient otherwise the predominant colour of taxis is still yellow.

Why bride wears yellow clothes on Mehndi in India?

Why bride wears yellow clothes on Mehndi in India?

PROF WAQAR HUSSAIN

       

There are three occasions in everybody’s life when one becomes the cynosure of all eyes and becomes the centre of attention and pivot of all the activities. These three days are; day of Birth, day of Marriage and the day of Demise. Out of these three significant days, two days are such when one is totally unaware of the activities happening around  but one day i.e. marriage day, one is fully conscious and aware of the occasion and thus takes dynamic part according to one’s will, wish and whim. On this day, everyone wishes to look attractive, eye-catching and unique. Females are more cognizant of their beauty than males thus it becomes very tough task for the bride to select her mehndi dress. Mehndi is a very vital event in Asian countries especially in India. That is why bride wears yellow dress. Bride looks beautiful, eye-catching and prominent in yellow attire. This reason is supported by the research of the Chicago University that concluded yellow colour is startling, stunning and striking and easiest to be spotted.

            

            My personal view is different! Bride wears yellow colour on mehndi to take the benefit of “comparative beauty”. Mehndi night is actually a preparatory night for the wedding day. Bride attends mehndi without having makeup. If yellow is meant to enhance beauty, she would have decorated herself with makeup but she doesn’t. In fact, yellow dress imparts a pale shade on the face of bride and her beauty fades away. In our culture, you have often noticed comment of elders: “you are looking pale! Are you healthy?” Looking pale is a sign of illness not a beauty. The next day, when bride wears red dress (usually), she looks pinkish, healthy and beautiful. And bride’s day before condition further enhances her charm as comparative beauty. The bride groom often doesn’t shave for a week or so and looks ugly on mehndi night. On marriage, he undergoes shave and looks fresh and beautiful. So, both become unattractive on mehndi to enhance their charm on the next day. So, bride wears yellow dress on mehndi as preparatory step to look shabby that night.

      Now a day, the trend is changing and brides are wearing yellow, green or red combinations on mehndi. But many brides still want to wear yellow dress.

Is henna pasting totally safe hygienically?

Is henna pasting totally safe hygienically?

PROF WAQAR HUSSAIN

     Now, mehndi is gaining popularity in Europe and America. Mehndi is a suitable alternative of tattoos which are painful in making, permanent, costly and harmful in many ways.

 Hollywood actors have played a pivotal role to make it popular. It is believed that actress Demi Moore and crooner Gwen Stefani are the pioneers in using, sporting and favoring the art of mehndi. Many other stars like Madonna have, Drew Barrymore, Naomi Campbell, Liv Tyler, Nell McAndrew, Mira Sorvino, Daryl Hannah, Angela Bassett, Laura Dern, Laurence Fishburne, and Kathleen Robertson have all used henna tattoos and made it popular. Some glosses like Vanity Fair, Harper’s Bazaar, and Wedding Bells, etc, have further enhanced the hinna tattoo trend.

                 

 Its entrance in the West and America brought it under scientific scrutiny. It is learnt to be dangerous for people with glucose-6-phoshate dehydrogenase (G6PD) deficiency. It is a cytosolic enzyme which is involved in glucose reaction chain and ultimately helps to protect the red blood cells against oxidative damage..  Its deficiency is more common in males than females. Perhaps this is the reason that this harmful effect remained hidden for years as 

most of its user are female rather than males; who generally don’t have the deficiency of G6PD.Then, It causes allergy in rare cases. Some quoted other negative effect i.e. in henna paste some chemicals are added to darken stain so the health risk of such pre-mixed paste can be significant. Food and Drug Administration (FDA) of USA does consider these risks to be adulterants and therefore illegal for use on skin. Some paste have been analyzed and found to contain silver nitrate, carmine, pyrogallol, chromium, 

etc. These compounds have been found to cause allergy, chronic inflammatory reactions, etc. Thus FDA has not approved henna for direct appliance on skin. It is unconditionally approved as a hair dye, and can be imported for that purpose. Henna imported into US that appear to be used as body art is subject to seizure, though prosecution is rare. (Source Wikipedia).From the above discussion, it can be concluded that its use on skin is not totally harmless as one time it was supposed. However, its use as hair dye is safe as it clear by the evidence that FDA has allowed its import.

How mehndi/henna dyes hands, hair, etc.?

How mehndi/henna dyes hands, hair, etc.?

PROF WAQAR HUSSAIN

      

             The henna plant contains lawsone (2,4 Hydroxy-1,4-naphthaquinone) which is a reddish-orange dye that binds to the keratin (a protein) in our skin. The lawsone gradually percolates from the henna paste into the outer dermis of the skin or hair and fasten to the proteins, developing a fast stain. The tinge of colour ranges from pale orange to nearly black depending on the quality of henna, duration of paste remains on the palm before wiping it off and nature of  ones skin.   Good quality henna, brand new, freshly prepared and acquired from plants of hot and dry climates; will stain the darkest.

What are uses of Henna(Mehndi) colouration?

What are uses of Henna(Mehndi) colouration?

PROF WAQAR HUSSAIN

        1) It has been originally used by women only, later men also started using it. Haldi (staining with turmeric paste) and mehndi are Vedic customs, intended to be a symbolic representation of the outer and inner sun. Vedic customs are based on idea of awakening the inner light. In a traditional Hindu design, sun is pictured on the palm. Mehndi is used in India in routine day and also on special occasion. Mehndi is also used on religious festival. For example mehndi is applied during various fasts (Vratas) like Karwa Chauk, a fast observed by wife to ensure long life of her husband.

      
    

Even gods and goddess are adorned with mehndi designs. A large dot in the centre of the hand with four smaller dots at the side is an oft seen design on the palms of Ganesha and Lakshmi.

       

 So, we can safely say that designing with mehndi, for Hindus, has a religious relevance also. Hindu wedding ceremony has become synonymous with this beautiful reddish dye. It is reported that henna painting is century’s old practice in India, Africa and the Middle East where it is believed that henna plant brings love, good fortune happy results, good feelings and protect against evil. Traditionally mehndi is practiced during marriages, joyous occasions apart from normal days.

       It is convenient in use; henna leaves are grounded and water is added to make a paste. Then this paste is applied on skin of hand etc. It is totally painless practice and has no side effect on skin and suitable for making intricate pattern on various parts of body. When the paste is dried after several hours, leave behind rusty red print which fades naturally over 1 to 3 weeks. Ease of its application, painless practice, beautiful glaring red print, completely harmless, cooling effect, healing power and temporary nature; have made a popular dye and cosmetic tool. It can be considered as precursor of tattoo. But it is more beneficial than tattoo as no life time commitment is required; no artistic skill in application is required; it has least side effects; it totally painless in application; and it colour is close the ideal complexion of men and women. These advantages have made henna a popular practice in different region of the globe. Even now it is gaining popularity in the West and America. Henna is a marvellous way to dye skin.

       

 2)  Ancient Egyptian used henna on their nails and hair round about in 1200 BC. Apart from human application it was also used to dye manes and hooves of horses; to colour animal skin; to dye wool and silk and to dye men’s beard.

       3) When people came to know the cooling properties of henna, desert people of India started coating their skin with it. So it became a common practice for desert people to reduce their body temperature. Even the people of plains used to paste in the sole of feet in summer as a coolant.  

What is the history of mehndi( henna) colouration?

What is the history of mehndi( henna) colouration?

PROF WAQAR HUSSAIN

 No clear answer is available. However, there are certain historical clues: First; Mehndi got birth in ancient India as a ceremonial art. Second, Mehndi was introduced in India by Mughal in 12^{th; some} says 15^th century. Third, Mehndi originated by ancient Egyptians who used to stain the fingers and toes.

        Fourth, The tradition of Mehndi started off in North Africa and the Middle East. It is believed to have been in use as a cosmetic hair dye for 6000 years.

        

 Fifth, the area in which it was used, give some idea about its origin. Henna was used for decorative purposes in the Roman Empire, Convivencia-period Iberia and Ancient Egypt, as well as other parts of North Africa, the Horn of Africa, the Arabian Peninsula, the Near East and South Asia. One can say that it has been in use in Afro-Asian region. 

        Sixth, its etymology will also give some idea about its beginning. The word mehndi is derived from Sanskrit word mendhika. It is called henna (حِنَّاء) ‎   in Arabic. The world henna is also used in Urdu and in English or you can call it alkanet (a dyeing matter extracted from the root of Alkanna tinctoria which gives a fine deep colour.)Sanskrit word mehndi shows that it might have been originated in Indian peninsula and Arabic word Henna hints about its starting place to be Arabian Peninsula or horn of Africa. However absence of proper English word shows that it had not launched from Europe. It is also known as mignonette tree, Egyptian privet, etc.         

 Seventh, its taxonomy, morphology, physiology, abundance and growth pattern will also depict it origin. Henna is a tropical plant, member of family Lythraceae; genus Lawsonia and specie Lawsonia inermis.) It is a flowering plant that grows 12-15 feet high and comes from the sole species of the Lawsonia genus. It is believed to be originally come from Egypt which is still one of the main suppliers of the henna plant (along with India, Morocco, and the Sudan). The plant grows best in hot climate of 120^oF (48.8^oC) and contains more dye at this scorching temperature.  It withers in cold when mercury dips below 50^oF (10^oC).   It also grows superior in dry soil than damp soil.  The 

leaves are in opposite decussate pairs and vary in sizes from 2-4 cm. long.  The flowers are aromatic, produced in conical panicles 1040 cm long, each flower 5 mm diameter, with four white petals. The fruit is a dry capsule 68 mm diameter, containing numerous 12.5 mm seeds.

         The henna plant contains lawsone which is a reddish-orange dye that binds to the keratin (a protein) in our skin. The lawsone gradually percolates from the henna paste into the outer dermis of the skin and fasten to the proteins, developing a fast stain. The tinge of colour ranges from pale orange to nearly black depending on 

the quality of henna, duration of paste remains on the palm before wiping it off and nature of  ones skin.   Good quality henna, brand new, freshly prepared and acquired from plants of hot and dry climates; will stain the darkest.