Walking and third law of motion

I realised one fine day that apart from trampoline and rockets there is an example of Newton's third law of motion that I missed all my life!

When we want to move forward, we push our foot backward, and earth as a reaction pushes our foot forward!

Same happens when we want to move backward, we push our foot forward!

Now I understand why children take so much time to learn to walk! :)

If atom is mostly empty space, why don't we pass through things ?

 We know the atom is mostly empty space, with nucleus accounting for a very small portion of atom. Nucleus can be compared to like a grain of sand with atom as a large room. Then why don't we pass through things, how can we sit on a chair ... why do we bump onto things ?

• Things are held up even with the vast amount of emptiness in an atom only due to fact that electron cloud in outer space of atoms in me are negatively charged- > So do the electrons in the atoms of chair, they are also negatively charged

• We know negative charges repel each other -> And we also know electrical forces are very STRONG-> So we are able to Sit, Walk, Do things that we do, See things as we see

• Without Electrical forces-> Everything will crumble into fine dust -> There will be no matter or no things as we see in Universe -> Only Clouds of Protons, Neutrons, Electrons !

What is meaning of Ampere as unit of current , and what exactly is a 'unit' of electric current ?

 Some history behind why Ampere is unit of current :

• While it was known that force is imposed -> and subsequent motion between two bodies each having an electric charge,

• Known through columb's law- > Electric force between two static bodies is directly proportional to product of charges and divided by square of distance,

• Which was somehow just like the gravitational law !,

• Marie Ampere observed that -> when electricity is passed between two adjacent wires- > it imposes a force on each other

• If currents are in same direction-> Wires attract each other,

• Unit of current was made in honour of his research,

• Definition of current - A hypothetical case of 2 thin and infinite wires , 1 m apart , 1 Amp is 'current' that generates 2x 10^-7 N of 'force' per 'every m' of wire

• Very small force and strange definition indeed, but this is what is behind the definition !

Is there anything like fixed time ? Is there a fixed tick tock throughout universe ?

In our everyday experience we see time as fixed . Aa it has been ingrained in our day to day lives. Like we have fixed meeting times, flight time , train time, birth time.. What would it even mean for time to be not fixed through our experience ?

But it was still something not something that could be measured or proved as fixed. Newton in his Princpica observed God as he is everywhere he would be keeping time same through space. And no one I guess even thought about it since it something contrary was not in our everyday experience. 

And here came Einstein and in his special theory of relativity told that time is no longer fixed and only thing fixed is speed of light !

He devised a simple thought experiment , simplicity of which has amazed me too.

Suppose we are in a train platform and we observe two strikes of lightning happening at same time in front. Now imagine there is a person on a train , and train is speedimg towards lightning which is to come on right. As train is speedimg towards lightning which is to come on right, he will observe lightning on right happening first than that on left.

So to observer on train two lightning strikes are not simultaneous events, his perception of time will be different than person on platform.

In short there is no absolute time or absolute tick tock happening throughout universe.. Time is a relative function of movement of refernce system.

In Hinduism we hear stories of time travel including one story of a king going to God Brhama (in a diffrrent universe), and after a while God Brahma tells him that in this short time , millions of years have already occurred on Earth. Are these ancient texts trying to tell us high technology from our past in form of a story (easier to pass on to next generations )?

Is it possible that during all these million years of Homosapiens, serious technology was only developed in last 1000 years ? Is it practically possible ?

Isn't it like mathematical improbablity of there being no aliens , will all billions of stars and galaxies in universe ?

The more we know I guess we will come to the realisation that we don't know.

Why capacity of air conditioner is in Tonnes ?

 This question as to why air conditioner capacity is in Tons had fascinated me for quite sometime... Tons is a unit of weight and what would it mean to have air conditioner capacity in tonne!! ? 

Its basic purpose being to take out heat from the room , it made no sense.. shouldn't the capacity be something like in terms of heat extracted from the room per hour or per unit volume ... like thermal energy extracted in Btu / sec or kJ/sec... why would someone sell a cooling equipment with capacity in terms of "weight" ? 

When I digged into it, I realised it has more to do with "History" rather than science or the equipment being sold itself.

It seems before AC conditioning as such what we see today was invented, people used to cool their homes by using the ice saved during wintertime. 

We know from thermodynamics that amount of heat (thermal energy) required to melt ice into water is much more than amount of heat required to further heat water. In normal technical language this thermal heat required to melt ice would be called "latent heat of fusion".. Well enough of the boring technical terms... 

Basically with the high thermal energy or heat required to melt ice, it would have been a useful tool to extract heat from the rooms , a large portion of which would be extracted for melting ice, which in turn would keep the room nice and cool.

It turns out the amount of heat required per hour to melt one tonne of ice in 24 hours (one day) was around 12,000 BTU/hr. In other terms, One tonne of ice was required to keep a room cool / pleasant for a day (24 hours). 

(One BTU is approx amount of thermal energy released if you burn a single piece of matchstick)

So basically for today's AC's when we say they are One Tonne AC, we are basically saying they can remove 12,000 BTU/hr of thermal energy from the room, with history as explained above.

Hope this clarity was able to simplify this topic of 1 or 1.5 Tonne AC Jargon used in some simplistic terms. 

Why is silicon doped ?

Silicon in its pure crytalline state is an insulator. This is because Silicon with 4 electrons in its outermost shell (With atomic no. 14) combines with 4 other silicon atoms sharing one electron each with them, hence becoming stable in the process. So pure silicon doesnt have any free electrons. If given some external energy, some electrons will break free, but still it will still be more or less an insulator.
So silicon is doped with an impurity like phosphorous having 5 electrons in its outer shell. 4 electrons will combine with 4 silicon atoms, but still one phosphorous electron will be free. Hence doping phosphorous with Si greatly improves its conductivity. (Despite the fact that quantity of Phosphorous will be very minute, maybe 1 in 1000.). This type of semiconductor is called as n type semiconductor.

Ozone

Ozone represented as O3, is found roughly 0.01 ppm in air. Above 0.01 ppm it can be dangerous. It density is 1.5 times that of oxygen and is diamagnetic, which means it defies formation of magnetic field.
We have sometime or the other heard about ozone depletion because of pollution, emissions and need to control global warming. So lets see a bit about ozone layer.
It is found between 10km to 50 km. It has the property of filtering out UV rays, which can be descibed as photons of wavelenth on the shorter side.
Formation: Ozone in stratosphere is formed with UV rays reacting with oxygen.
O2+ Photon ----> 2O
Also, now,
O + O2 ----> O3
This was about formation. Now you will ask how this O3 is depleted by the much hyped chlorofloro carbons, this is how:
O3 + O --------> 2O2
It is destroyed in reaction with atomic oxyegn under presence of some catalysts.
And you guessed right, these catalysts are also fromed due to chlorofloro carbons.
Story ends !

Science behind Rainbows

When we see rainbow around us we feel enthralled isn't it? let's see the the basic science behind it..
If you will see there is plain and simple optics behind it.. Nothing great really... Basic principle is that when light passes through a different medium, it bends, which means it will change its path or direction. And light consists of 7 different colours from violet to red you all know.
Now all these colours do change directions differently when passing through a different medium as their frequencies are different.
As seen in the image, at one time an observer will be able to see only one colour due to a droplet of water. So, in a combination of droplets in a rainy season an observer will see all the colours together formed after dispersion from different droplets of water.
Hence a rainbow is seen. Hurray!!

Theory of relativity and Time travel

Its quite amusing that i should start with relativity straightaway, but i will give it a try..
In simplistic terms, this theory says that the speed of light remains constant, no matter who is observing it and how he is obseving it.
Let us take an example, if i am riding on a bike with speed of 60 kmph and you come from behind in another bike at a speed of 100 kmph. Now, i will see you going at a speed of 100-60 = 40 kmph. Now this is simplistic newtonian mechanics. Isnt it simple!. Now again if i am going at 60 kmph and you travel in front of me in a bake at 100 kmph, then i will see you speeding at 100+60 = 160 kmph !. Seems wierd but as you know it is true... As we can all experience it too.
Now suppose you come from my behind at speed of light in your bike and i am travelling at speed of 60 knph in my bike then our natural reaction should be that your speed i should see as Speed of light- 60kmph. But thats where einstein had other ideas!
He knew that speed of light is same irrespective of frame of reference from where it is observed. Whether frame of reference is stationary(You are sitting under an apple tree) or it is moving (You are speeding on a bike) it dosent matter. I will see you moving at speed of light only.
And now here einstein encountered a divine touch of genius. He said that as i cant see your speed changing inspite of me too moving at some speed then something should change. And that something that changes is time!. Hence einstein's theory of relativity postulated the idea of time travel.

Beginners guide to Science and Technology

With this webpage i would like to explain the basic principles in scinece in the simplest way possible... As Einstein had said.. "Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction."