How GPS works?

Global Positioning System

       The cost for launching some 12 to 24 satellites into the space from our atmosphere with those big satellite launching vehicles needs a huge amount of money, hundreds of scientists for tremendous amount of calculations, good engineering in the sense mechanical, electrical, computational, etc. and finally some hard work.   

      Thinking about all these things, we may think for a while that the GPS system in our mobile does really needs a huge amount of technology. But it is really amazing is that the physics behind this small GPS thing in our smartphones is not more than the level of 10th standard physics. 

       The principle is just,  Velocity [1] =  distance / time . It is all needed to determine the position of an object (ofcourse for the most accurate results we will need some of general and special relativity).

The concept is simple as we determine the distance between two stations in a highway. For example, if you go from station-1 to station-2 with some constant Velocity , the distance between them can be calculated as, $$ Distance(d)_{1-2}= velocity(v) \times time(t)$$
where t - time taken for you to reach from station 1 - 2.

If you don't want to go, you can send a messenger(msg) to station-2 at constant velocity and make him to travel back at the same velocity. Now, you can calculate the time taken for him to travel twice the distance ($d_{1-2}$) with velocity "v". Hence, $$ d_{1-2-1} = 2* d_{1-2} = v_{msg}* t_{msg} $$ or simply $$ d_{1-2} = \frac {v_{msg}*t_{msg}} {2}$$ That is all we need to determine the position of station-2. 

In an exact similar way, satellite determines your position by sending a messenger to your smartphone and receiving it.
And the messenger, in god's grace always travel with same speed in vacuum, Electromagnetic waves. All these things happened just because of EM waves and its constant fundamental speed.

We get all the information so fast because of the tremendous speed of light which is about $3\times 10^8 m/s$
[Think: If it is about some 1 km/s, then before knowing your GPS coordinates, you would have gone to hell.] 

Ok.. Now I can determine the position with light signals. 
But why do you need some 12 to 24 satellites in the space to determine your position?
It is because unfortunately our satellites don't have any eyes. They can just only receive the signals but can never determine accurately "from which direction the signals are coming".

Your position on earth is with respect to the satellite is not a fixed straight line as we did it in the highway problem. 

From the measurements, satellites will determine the position of your cellphone but on the surface of giant hollow sphere centered about the satellite. Since, it knows the signal is coming from earth, it just focuses on the circle that is on earth which is the common intersection hollow sphere about satellite on earth. 




















Thus it reduces the problem of determining the position from infinite space to a small circle on earth. 

We know from geometry that, minimum three circles are needed to intersect to create a point. And so, to determine a position on earth, at least we need three satellites which is visible to that place. You cannot receive and determine the position from the satellite that is on the other side of the earth. 

One or three satellites are not enough to cover the entire globe of sphere. That is why, we are sending so many satellites such that at any point on earth at any time should be covered by at least three satellites in visible range so that all the single points and positions on earth can be located most accurately. 

That is all for the basic lever. 
         But it may not so simple as it sounds, if you are going to need too much accurate and perfect solutions such as determining the distance between your couch and your T.V. from the far distance orbiting satellites. 

        For those things, you will need to finish your degree in Physics, since it handles with synchronization of clocks with the help of special and general relativity.  

[To understand how Relativity plays the crucial role in GPS tracking, we will need some calculations].

Power Switch in computers

When you look out for computer problems, one of the simple problems could be your power switch.

Problem: 

Computer doesn't start when you press the power switch. Computer does give no response when you switch it for multiple times. 

Reason: 

It should be either due to any fault in your SMPS (Switched Mode Power Supply)) or due to the connection problem in the power switch. 

Some of the computer does have an indicator in the motherboard. If that light blinks, when you turn on the power supply (not the power switch in CPU), it indicates that power is coming to CPU and your SMPS is just working fine. But if the computer doesn't start after switching the power switch, then there is a problem.

Solution:

The problem with power switch can be solved, just be reconnecting it again. Still if doesn't work, carefully take down that connection from the mother board and change it with the new one bought from your nearby Electrical store. 

To reconnect the switch you can take it out by slowly removing the front panel of CPU as follows,

   

You can trace the wire connection to motherboard and reconnect it with itself or new one. But you will learn one thing about, How the power switch works in a Computer. 

Free of cost solution for basic problems in your computer

Dealing with computers has become a routine for me, since I myself own 6 computers in my home. Only one of them is good which is a laptop and all others are old PCs. 
   But a very really good thing than can happen to you with your old items is that, you will learn something about it when you mess with it. 
As the same, in my house with a standard pattern [Not the same computer, but one by one in a different order], they will at least make problems once in a day. 
From those pattern, I did realized some most common problems that may occur in our computers. And they are,

Problem-1:
One of the first common basic problem you may experience is, 
'When you work with multiple tabs, suddenly your computer freezes and not a single switch works [including mouse, keyboard,etc.], where you need to restart your computer manually. 

Reason:  
It is due to your RAM and its low capacity.

Solution: 
Of course if Restart solves your problem, no need to worry. But if the problem persists, you can try this, 

Open your CPU case 

Look out for RAM attached in Motherboard like given below

Flip the lids and take out the RAM and rub with rubber or any clothes

And fix it again and restart. Most of the initial times of your computer, this may be the first problem you may face it.

 Still if the problem persists, and computer doesn't work at all, then the problem would be different.  

Problem-2:
Computer doesn't start after working for a long time, but starts when you leave the computer for one day rest. 
(or) it would show BSOD (Blue Screen of Death  -where nothing will work in your computer) but with a warning  message
(or) when you start your computer, it shows the message
"CMOS checksum error" or "CMOS failure occured". 

Reason: 
All these problems are due to old CMOS which needs to be replaced soon. 

Solution: 
If it shows for the first time, you can just take your CMOS and reinstall after cleaning it. If problem persists, you should change your CMOS battery. 
Note: Reinstalling CMOS battery clears all registry settings. 
     Most of the BSOD problems could be solved by clearing and restarting registry settings and so reinstalling CMOS is the best way. 

To take out CMOS battery, as same as previous, open the CPU, and you can find the CMOS in the motherboard looks like below,

Just flip the pin and take out the battery 

Buy a new battery or just place it again [most of the CMOS would be CM2032]
Thus You can replace your CMOS. 

When you do this, eventually reinstalling all the hard wares with itself but with just some "cleaning" would solve many problems that is going to happen in your computer.