A History Of Medicine

A HISTORY OF MEDICINE

2000 BC - Here, eat this root.

1000 AD - That root is heathen. Here, say this prayer.

1850 AD - That prayer is superstition. Here, drink this potion.

1920 AD - That potion is snake oil. Here, swallow this pill.

1945 AD - That pill is ineffective. Here, take this penicillin.

1955 AD - Oops ... bugs mutated. Here, take this tetracycline.

1960 -1999 AD - Thirty-nine more "oops" ... Here, take this more powerful antibiotic.

2000 AD - The bugs have won! Here, eat this root.

Anonymous - Quouted in "Overcomming Antimicrobial Restistance" - World Health Report on Infectious Disease 2000.

"WHY IS THE SKY BLUE ?"

The sky is blue due to an effect of the earth's atmosphere on the light reaching us from the sun.

Although sunlight looks 'white' it is actually made up of a whole spectrum of colours which you can see in a rainbow, or with a prism. The different coloured lights have different wavelengths ranging from blue light (which has the shortest wavelength) to red light which has the longest.

The Blue light is strongly scattered by the oxygen and nitrogen in the atmosphere, whilst the other colours, with longer wavelengths, are not affected.

This means that when light waves arrive from the sun, some of the blue light is bounced about and scattered in all directions by the air so that it no longer seems to be coming just from one place - the sun - and instead the whole sky seems blue. But the rest of the light (with longer wavelengths) passes unaffected straight through the atmosphere to your eye and hence the sun looks a yellowy red colour (white minus some of the blue).

So why does the sun go red at sunset ?

This is because as the sun 'sinks' the light has to travel further through the atmosphere to reach your eye meaning that more of the blue (and shorter wavelength light) is scattered (removed) than when the sun is high in the sky, making the sun look even more red.

courtesy of thenakedscientists.com