Time Slowing Down I'd like to ask a question if I may about the relativity. When travelling at the speed of light(which is impossible for particles with masses) or very close to it, would it be me, myself, seeing my watch run slower, or would it be an observer seeing it? 
Also, according to Twin Paradox, the twin who stays in the earth ages more. I don't know how this is possible. An observer would see my watch tick slower, not me? 
 A: Think about this
In your brain there is a clock too. In other words, everything has a clock in itself. The clock in this meaning is the electron and molecule activity. Both gear and battery is electron and molecule activity. And inside your brain is another kind of electron and molecule activity
Time dilation is about the reality that all electron and molecule activity of everything will decrease speed when that thing move. So when you move with your watch. Your brain activity will slower in the same rate as your watch. And you will not notice that your watch are slower
But if someone stay still and observe your watch. Electron and molecule activity of that person is in constant rate. So they will notice that your watch is slower than normal
The cause is speed of light. Electron and molecule activity take place around atom. Electron move between atom cannot move faster than speed of light. So when you move. The speed of electron that jump between atom need to be slower to keep its raw speed under speed of light
And about twin paradox
Imagine that you cell multiply and dead everyday is the biochemical reaction, and it is another kind of electron and molecule activity. So yes, the aging process is slower by time dilation too
A: Time dilation (and also length contraction) always occurs with respect to an observer in a different frame of reference. You, in your own inertial frame, will not notice any difference. However, when you compare your measurement to that of an external observer, you will see a discrepancy in the results. If you enter a spaceship and go on a journey through the solar system at a very high velocity, and take a watch with you, and then return to your homebase (where you have left another watch), you will see that the watch you took with you has registered less ticks than the one you left back home. The equivalent statement is that less time has passed for you. 
Regarding the twin paradox: naively, one should ask the question as to why there is a different outcome in the measurement of time for both systems, since one could say that if the twin in the spaceship moves relative to earth, earth also moves relative to the spaceship. However, this is not the whole story: the spaceship, in order to make its journey to outer space and back home has to accelerate, and this breaks the symmetry between the systems.  
