Sunday, May 19, 2013

Evolution of the Whale

Evolution of the Whale
The Blue Whale is the largest living creature on the planet.  It is hard to believe it evolved from  a land mammal roughly the size of a dog. While this is accepted as science fact, I have had many a discussion with those unwilling to believe this. But who cares~ no one believed in Max Planck in the first place, not even himself, and everyone was laughing at Charles Darwin when he suggested that we are closely related to macaques.


The cetaceans (whales, dolphins and porpoises) are marine mammal descendants of land mammals. Their terrestrial origins are indicated by:
  • Their need to breathe air from the surface;
  • The bones of their fins, which resemble the limbs of land mammals
  • The vertical movement of their spines, characteristic more of a running mammal than of the horizontal movement of fish.
The question of how a group of land mammals became adapted to aquatic life was a mystery until discoveries starting in the late 1970s in Pakistan revealed several stages in the transition of cetaceans from land to sea.




This animal existed 50 million years ago by the rivers of southern Asia, walking on slender legs tipped with hooves, and takes to the water whenever it senses danger

It is called Indohyus (meaning India's pig)
and it is the earliest known relatives of today's whales and dolphins.

According to molecular evidence, the closest living relatives of whales are, quite surprisingly, the artiodactyls, a group of hoofed mammals that includes deer, cows, sheep, pigs, giraffes, camels and hippos, yet not a single one of them bears even a passing resemblance to whales and dolphins. Among the group, the hippos are evolutionarily closest and while they are at least at home in water, their family originated some 35 million years after the first whales and dolphins did.


Even though Indohyus had the elegant legs of a small deer and walked around on hooves, it also had features found only in modern and fossil whales.

It's jaws and teeth were similar to those of early whales, but the best evidence was the presence of a thickened knob of bone in its middle ear (involucrum). This structure helps modern whales to hear underwater, it’s only found in whales and their ancestors, and acts as a diagnostic feature for the group.

We should, however note that this animal IS NOT the direct ancestor of whales, it is only a sister group to the ancestors of whales. Got it?

So why did they go aquatic? Scientists speculate that whales developed from an Indohyus-like ancestor that fed on plants and possibly small invertebrates on land, but fled to water to escape predators. Over time, they slowly turned into meat-eaters and evolved to swim after nimble aquatic prey.



For a much more in-depth comparison see http://en.wikipedia.org/wiki/Evolution_of_cetaceans

Tuesday, May 7, 2013

How Does Fire Behave in Zero Gravity?


Most of us don't know how fire behaves in zero gravity. 
Well... the movies were wrong.

Let's look at this picture.
Image: ynput.com
Trying to come up with a plausible explanation?
Allow me to enlighten you instead.

Fire needs oxygen, and that's readily available in Earth's atmosphere. Out there in space we have meager(practically none) supply of oxygen, and so astronaut cannot start a fire in outer space. If there's an explosion out there in space, the fire would quickly die away rather than burning the whole thing into ashes.
Image: cinem7.com
In the spacecraft, on the other hand, is a totally different story. We have ample supply of oxygen in a spacecraft, but no gravity, which is why we often see videos of astronauts floating about in spacecraft. Here, fire can start but it doesn't behave the way it does on Earth.
Image: futurecamping.com
On Earth, gravity pulls the air onto the ground, and so we have plenty of air around us. When fire burns, it heats up the air around it, causing circulation of air--hot air rises whilst cool air gets pulled downward. The section of air close to the fire rises and pulls the fire with it. This circulation of air is the reason behind the characteristic shape of fire we see here on Earth.

But in a spacecraft hanging above us in the orbit, there is no gravity. So there is nothing to pull the air downwards--meaning there is no air circulation. It still burns the oxygen around it but there is no gravity to pull cool air downwards to enable any air circulation. The fire starts but it just stay there. It doesn't flicker as it does on Earth and if there is nothing to propel fresh air(in this case, oxygen) towards it, the fire would slowly die away.

Savvy?