The Earth is Round, huh?

How was the cartoon characters' invasion of Facebook profile pictures, this December? Every profile you land onto, would have shown you Dexters, Popeye, Scoobies, Tin Tins and several other stalwarts from the Cartoon World, letting us know how people loved (and would love) to revert to their childhood. You do, I bet. Perhaps, for this reason, these kind of high school queries pop up in my mind, then and there. :) Apparently matured science-freaks, stay away. ;)

Flat Earth Model

Is the Earth round? Why shouldn't it be flat as it was assumed to be, centuries ago? What bothers the Flat Earth Model? Let me put forth, a few.

The Flat Earth:

Early astronomers, (most of them are actually travelers) who spent most of their time on sea, assumed that the Earth was flat, though their assumption wasn't blind enough to be criticized. 

1. Out of hundreds of ships that start their journey from the same spot, a few were found missing, as they lose their way, get stranded on the sea and die off. This made the other travelers assure, "The horizon is always seen as a straight line bordering the sea and the sky; The ships cross the horizon and fall off the earth into the space", which proved the possibility that the Earth is flat.

Since the earth is flat, ships that cross the horizon(border) fall off the earth into the space and get lost.

2. "According to the Aether Wave Theory, aether- a massless substance pervades all matter and even space(vacuum). If so, it would eventually resist the high pace of revolution of the spherical Earth round the sun; Being a sphere, aether resists its motion", the flat-earth nuts say.

The Spherical Earth:

On the contrary to the Flat Earth model, evolutionary philosophers like Eratosthenes posed a strong contradiction to the pre-existed model. Some of the solid and substantial proofs are as follows.

Lunar Eclipse

1) We all agree that Lunar eclipse occurs only because the shadow of the Earth darkens the Moon, as the earth comes in between the Sun and the Moon. If not the Earth were spherical, the shadow observed would not be a "curve". This affirms that the Earth must be round, i.e, spherical.

2) Mast of Ships coming from a far distance is always seen before the hull. This proves that the Earth is round.

3) A stick casts shadows of different lengths at different places, at a time only because the Earth is round, spherical. If the Earth were flat, the stick would cast shadows of same length everywhere.

4) The geometric shape with minimum surface area is sphere. Every matter, especially liquids tend to get spherical to minimize their surface area. In analogy to this fact, spherical Earth must favor it formation.

5) Pole star(Polaris) is seen straight above the sky when observed from the North Pole, where as it is seen lower in the sky when observed from the Equator. This proves that the earth must be round.

Modern Approach:

Though, these points validate the spherical shape of the Earth, one need a fool-proof experiment to confirm its shape. 

Every satellite image of the Earth, taken from the space or from the moon, show that the Earth is round. Also, the invention of three-dimensional imaging system and geosynchronous satellites add yet another proof to the Spherical shape of the Earth.

Satellite image of the Earth

Also, the weight of an object as measured at the Poles appeared to the greater than that of the Equator. Since, the weight (gravitational force) varies inversely as the distance, heavier weight implies lesser distance. Therefore, the Poles must be relatively nearer to the center of the Earth, than the Equator. Therefore the shape of the Earth must be a sphere compressed at its poles. This shape, known as "Oblate spheroid" is widely accepted as the shape of the Earth. :D

gotcha??

Why is the night sky dark?

Sitting beside a sea, comforting on the beach sand with legs stretched, relishing the cool sea breeze, peeping at the dark clear night sky pondering something is really exciting, yeah?? 

Ever got such a kinda situation to bask the beauty??

Yeah? But halt here....! Why is night sky always "dark"??? Ever wondered? 

Why, at first look, you might say, "This is too fundamental. Too simple and obvious". But it isn't so simple as it seems to be! This is a famous and not so easy paradox called as "Olbers' paradox" which has just been solved to some agreeable extent.

"Why night sky appears dark, huh?"

When you put forth this question, you are likely to get the most probable explanation, "During night, the sun is on the other side of us. So, we feel the sky dark."

But it is not quite convincing, for we aren't high school kids anymore. Smarter children, who have a good sense of intelligence would pose a contradiction to this explanation, which goes, "Science says that there are over 200 billion stars in our galaxy - the Milky Way. So, what about the light emanating from those stars? Wouldn't they light up the sky??"

If light from almost every star reaches the earth,
 the sky would look like this.

This question has a salutary logical point. There are almost uncountable number of stars on the sky(in the Universe). These stars, being self-luminous, would definitely give off light which should reach the earth. If this is true, the sky would look at least like this:-(see the image on the right)

But in reality this doesn't seem to be holding good. What has happened to the light rays which have been emanating from these stars? What is preventing them from reaching the earth?

The most expected answer is "Stars(other than the sun) are excessively far from the earth and therefore, the rays exhaling from them suffers an appreciable loss in intensity. So, the night sky is dark". This explanation would render us a little better view on the topic. But what is that which is exactly responsible for such a loss in intensity??

Picture describing Oblers' paradox.

One might say that every galaxy contains more number of planets and other dust particles, than the number of stars. So, these plants, asteroids, comets and dust would simple block "some" of the light rays from the distant stars from reaching the earth. But remember, they block only "some".

Also, the distribution of stars is not uniform, but they hide behind one another so that it solves the paradox to a little extent.

But the main and more accurate answers are as follows:

1)The Universe is expanding. So, light from the distant stars are "red-shifted" to obscurity.

2)The Universe is young. Light from distant stars hasn't even reached us yet!(may sound funny for beginners)

Speaking about the first explanation, the Universe is said to be expanding frantically. The Big Bang Theory supports this view. So, distant stars which are moving at a considerably high speed will be "red-shifted". To elaborate, as these stars are moving at a high speed relative to the earth, the wave-length of the visible light emitted by them would be shifted towards red.(red-shift) 

But some physicists put-forth a counter-argument that light of lower wavelength like gamma rays, x-rays and UV-rays would also be red-shifted to "visible region" and this would compensate the former.

Whatever be it! But the second point has a good significance. The Universe is young and degenerate. So, we only see the part of Universe less than 15 billion light years away. Objects which are more than 15 billion years old are too far away for their light to reach us. 

Thus, Oblers' paradox is somewhat resolved. Contradictory thoughts are welcomed. Cheers......!

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(pictures are taken from the web. and link courtesy - wikipedia)