I am 15 years old, still very young. I like studying modern physics, instead of the classical physics taught by teachers in school-it is boring and inaccurate.

I would like to share some of my initial forays into Einstein`s World by showing you some formulas that I know:

First, you need to know the difference between Galilean Transform and Lorentz Transform.

Galilean Transform

delta x prime= (delta x - v delta t)

delta y prime= delta y

delta z prime= delta z

delta t prime= delta t

Lorentz Transform

delta x prime= (delta x- v delta t)/F

delta y prime= delta y

delta z prime= delta z

delta t prime= (delta t - v delta x/c^{2})/F

F is lorentz factor which is F= square root (1-v^{2}/c^{2})

When the speed of light is 1, then all c will equal to 1, thus being cancelled off. This is true for all the above formulas.

Now, let me show you how to apply them.

suppose 2 events happen in the space-time. One of them happen in the first reference frame, S and when viewed in the second reference frame, S prime, they look the same but relative, thus relativity exists in both space and time, as we shall see later.

According to Einstein, length will be shortened when an object moves through space-time. This is known as length contraction.

Mathematically, when x changes, then t should be kept constant, thus t=0

So the first Lorentz transform become

delta x prime= delta x-v delta t /F

= delta x/F

if an object travels at 87% the speed of light in vacuum, c, then F becomes

F= square root 1-(v/c) square

= o.5

which means the length will be shortened to half the original value

so, delta x/0.5 = delta x prime

delta x= delta x prime times 0.5

if x is 6 cm, then x prime is 12 cm

The same matter repeats with time dilation, the shortening of time when clocks travel through space-time, simply substitute x=0 in to the forth Lorentz Transform and get the correct answer, if t prime is 6 seconds, t is only 3 seconds. Your(stationary) watch is running at a rate of steady 6 seconds, but when something/somebody approach 87% the speed of light, he/she/it/they will only age at half of your aging rate.

For combining speeds,

per Newton, Final velocity = velocity + velocity, but per Einstein, you can`t add up speeds beyond c, so

his formula is final velocity = (velocity 1+ velocity 2) divides by (1+ velocity 1 + velocity 2/c squared)

Enjoy Einstein`s World!