Q:  Which animal eats food equal to its weight? (Saumya, World)

The small, furry, gray shrew races through the twig tunnel, long snout to the ground, sniffing.  He smells a fat worm, pounces on it and wrestles the worm, twice his own length, into his mouth.  He gobbles it down.  Always hungry, he runs again, sniffing...   

A: You're probably asking about a tiny animal, about the size of a mouse — the common shrew.  According to zoologist Peter Crowcroft, these mammals don't actually eat their own weight in food every day, but come close:  about three-quarters of their own weight. 

Because of their small size (and, consequently, large surface area relative to their bulk) they work hard to stay warm.  They radiate heat through their large surface area and must restore that heat by burning food, which means eating food, which means finding food.  And that runs up another energy debt:  hunting costs.  The end result is the poor creatures live on a tough schedule:  feed for three hours, rest for three hours, repeat, as long as they live.    If they can't eat for two or three hours, they die.  Moreover, the lower the temperature, the shorter the time they can go without food. 

By the way, shrews, though the smallest mammal, may be the most belligerent.  Their ancestors were probably the first true mammals on Earth.

Further Reading:

The Shrew(-ists) site by Werner Haberl, Vienna, Austria

Masked shrew, eNature.com

The Peter Crowcroft memorial archive by Simon Crowcroft

Q:  If I'm 11 years old on Earth, how old am I on Neptune? (Tommy, Providence, Rhode Island)

A:  You're not even one Neptune-year old — only an insignificant 7 % of a Neptune year — because Neptune takes almost 165 Earth-years to go around the Sun. 

In fact, "Neptune was discovered in 1846", only 160 years ago, so it hasn't yet "completed one orbit," says astronomer Robert Massey of the Royal Observatory Greenwich in London.

The Hubble Space Telescope took these pictures of Neptune over a 6-year period.  They show the southern hemisphere brightening as spring occurs.  (It's autumn on the Northern Hemisphere.)  Spring there lasts 40 years; then it's summer, but still cold (-350 degrees F,  -213 degrees C).

By the way, Neptune changed the ways of the Royal Observatory Greenwich (ROG):  "Here in Greenwich we were famous for not discovering the outermost gas giant," emails Massey.

"John Couch Adams, the English mathematician who calculated its position based on irregularities in the orbit of Uranus, couldn't persuade George Airy, the then astronomer royal to conduct a search, and in any case we didn't have suitable telescopes on site." Adams' French counterpart, Urbain le Verrier, went to the Berlin Observatory, and found the planet. "This 'Neptune Scandal' helped turn the ROG into a modern research observatory."

Further Reading:

Neptune, Royal Observatory Greenwich

Brighter Neptune suggests a planetary change of seasons by Ray Villard and Terry Devitt, Hubble Space Telescope

Q:  What is the colour of a red flower when it is exposed to blue light? (Saijune, Manama, Bahrain)

Galego, a red flower of Galicia, Spain. Photo by Luis Miguel Bugallo Sánchez. Used with permission.

A:  The red petals appear black in blue light, because they reflect red light.  If I illuminate the red petals in blue light only, then there is no red light to reflect to my eyes and, therefore, the red petals appear black — the absence of light.

Now, for a couple of qualifiers:  the petals will contain some blue color; also blue lights emit a tiny amount of red light.  Thus, the red (with a trace of blue color) petals will reflect some blue light and, therefore, not appear exactly black — more grayish.  Also, the petals will reflect the small amount of red light emitted by the 'blue' light.  So, the color will actually be dark gray with a tinge of red.

Further Reading:

Color perception by Rod Nave

Color and vision by Tom Henderson, Glenbrook South High School, Glenview, Illinois

(Answered Oct. 9, 2006)