How dolphins sleep

Like any other mammal the dolphins too need to rest but they cannot shut off their brain completely when they go to sleep. They can never go into a deep sleep like we humans do because they have to be conscious all the time to breathe.We too need to breathe even when we go to sleep so why can't the dolphins sleep the way we do, you may wonder. Well, the reason is that unlike us, dolphins live in the water and they breathe through a blow hole. As they cannot stay under water for long and be without opening the blow hole to take a breath they cannot enjoy a deep sleep .

Dolphins have "solved" this problem by letting one half of their brain sleep at a time.

This has been determined by doing EEG studies on dolphins. Dolphins sleep frequently, throughout the day for about eight hours day .

A dolphin's behaviour when sleeping/resting depends on the circumstances and possibly on individual preferences. There are three ways in which they could rest or sleep .

They can either swim slowly and surface every now and then for a breath, rest at the surface with their blow hole exposed or rest on the bottom (in shallow water) and rise to the surface every now and then to breathe.

Why birds chirp at night

Generally birds are very noisy when they are flying and searching for food during the day. The sound of their chirps lets us know they are active. Sometimes birds chirp at night too and they do so for a variety of reasons.

While many birds are daytime birds that need sunlight to see the food they are hunting and gathering, other birds are nocturnal, or active only at night. Owls are one such species. They hunt critters that scurry about in the night time , such as rodents. That is why you hear an owl's hoot after dark. Other birds such as the whippoor will are famous for their night time activity. In fact, the whippoorwill can repeat its loud chirp 400 times without stopping!

Many scientists are of the view that as birds do not need much sleep they would continue to hunt even in the night if the darkness didn't limit their ability to see their food. So ,in areas where it is lighter for more hours a day, or in places where outdoor lighting helps visibility, the birds may go in for some extra feeding time and we will hear them chirping.

Some experts think that birds may be chirping more at night because of the high level of noise during the day time.The loud noises made by traffic and other daytime activities may have forced them to change their singing time especially since a bird's mating call may be drowned for the noise during the day.

How deep the oceans are

An ocean is a body of saline water that composes a large part of a planet's hydrosphere. The world's oceans in descending order of area are the Pacific , Atlantic , Indian , Southern (Antarctic), and the Arctic Oceans. When we look at these five major bodies of water as a whole, it is referred to as the world ocean.

This gigantic body of water has an average depth of 3800 metres. Don't get fooled though. This number is just the average depth. The depth of the deepest seas can exceed 11,000 metres. The Pacific Ocean's average depth is 4,188metres (14,000 ft).The average depth of the Atlantic, with its adjacent seas, is 3,339 metres (10,955 ft); without them it is 3,926 metres (12,881 ft). The average depth of the Indian Ocean is measured at 3,890 m (12,762 ft).The Southern Ocean has typical depths of between 4,000 and 5,000 meters (13,000 to 16,000 ft) with only limited areas of shallow water.

The Arctic Ocean is the smallest, and shallowest of the world's five major oceans. It occupies a roughly circular basin and covers an area of about 14,056,000 km2 (5,427,000 sq mi), almost the size of Russia. The coastline is estimated to be 45,390 km (28,200 mi). These depth measurements can be conducted through several different methods. Two of the most common ones are satellite altimeters and echo sounders. Satellite measurements use frequent short microwave radiation to measure sea level with great accuracy. Echo sounders, or sonar, use sound waves of frequencies from 10 kHz to 30 kHz to travel from the surface of the ocean to the ocean floor. These sound waves are transmitted slowly. The velocity of the sound wave and the time it takes for the wave to echo from the bottom or reach the receiver are the two factors necessary to determine the depth.

The total volume of the world ocean is approximately 1.3 billion cubic kilometres (310 million cu mi) with an average depth of 3,682 metres (12,080 ft)[.

It is the habitat of 230,000 known species, however much of the ocean's depths remain unexplored and it is estimated that over two million marine species may exist.Do you know what the deepest part of the entire ocean is? The Challenger Deep which is located beneath the western Pacific Ocean in the southern end of the Mariana Trench.

It runs several hundred kilometres south west of the U.S. territorial island of Guam. Challenger Deep is approximately 11,030 metres (36,200 feet) deep. It is named after the HMS Challenger, whose crew first sounded the depths of the trench in 1875.

Why cats purr

Many suggest a cat purrs from contentment and pleasure.

But a cat also purrs when it is injured and in pain. Some experts in the field have suggested that the purr, with its low frequency vibrations, is a "natural healing mechanism." and that purring may be linked to the strengthening and repairing of bones, relief of pain, and wound healing. They may also purr when startled or upset.Kittens learn how to purr when they are a couple of days old and they continue this to adulthood. Purring is a unique vocal feature in the domestic cat. However, other species in the Felidae family also purr: Bobcat, Cheetah, Eurasian Lynx, Puma, and Wild Cat (Complete list in Peters, 2002). Although some big cats like lions exhibit a purr-like sound, studies show that the Patherinae subfamily: Lion, Leopard, Jaguar, Tiger, Snow Leopard, and Clouded Leopard do not exhibit true purring.What makes the purr distinctive from other cat vocalizations is that it is produced during the entire respiratory cycle (inhaling and exhaling).

Other vocalizations such as the "meow" are limited to the expiration of the breath.

Why we blink

How often do you blink? Well, most people blink around 15 times a minute. Blinking is an involuntary action that protects the eye. The eye, the most delicate and sensitive part of the body, has to withstand the dust present in the air and blinking naturally acts as a safeguard mechanism. Blinking helps in two ways. It lubricates the eyes and keeps the front portion clear for good vision.

When we blink, a film of tears covers the eyes and washes all the minute dust particles that may be present. That is the physiological reason behind blinking but we blink for psychological reasons as well. For instance, nervousness, loud noises, stress and tension affect the number of times we blink. You can even try it out yourself. Count the number of times you blink when you do something wrong. The tension would probably make you blink more.

But when a person is using all his concentration powers,like while driving or reading for instance, he will probably blink less. The effort to concentrate on the task ahead will make him blink a fewer number of times. Observe people around to see who blinks how many times in what surroundings.