Time is really a fascinating concept, which is tricky to understand. I was attracted by reality and excitement involved in learning physics in my high school. I use to spend more time in reading physics textbook than others, which gave me good understanding of time. Here I just want to share the concept of time and possibility of a machine that can take us over to different instant of time
As all we learned in our higher school that Second is defined as
"The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom"
So the standard time taken by cesium 133 atom to move from one energy level to another energy level after radiating energy has been considered as a second. Please do remember this point; we will come back to this point again.
Concept of Radioactivity
Nucleus of an electron has protons and neutrons. The protons which are positively charged particle will be repelling each other inside the nucleus. The repelling force will be directly propositional to the number of protons in nucleus. Nuclear reaction is nothing but separating a proton or adding protons to the nucleus and thus generating huge energy. Metals heavier than Iron will have more protons, so more repulsive force inside the nucleus. Repulsive nature makes these elements highly unstable. Uranium with 92 protons is an example for reactive elements. It will emit energy in the form of radioactive signals until it come to ground state. We call these elements as Radioactive.
Relation between Mass and Speed
In quantum physics explained by Einstein, mass can be converted to energy and vice versa. This has been governed by the equation E=mC2.That is,when a mass of m Kilogram travels at a speed of light it will be converted to energy equal to the product of mass of the object and square of the speed of light. It is quite oblivious that tremendous energy will be released (because of C2 ).
All the properties of any object traveling in the speed of light will change with respect to the object which is stable. According to Einstein’s equation as the object approaches speed of light the mass of the object become infinite. Likewise the time taken by the cesium 133 atom to change from one energy level to another level will change. This shows that the standard one second is no more same as you started travelling at light's speed.
So in the condition of a mass travelling at the speed of light, the time taken for cesium 133 atom to move from one level to another will be different.So time differs between that object and us. I guess this is the concept people are trying to use in Time machine.May be in future we can bombard a mass with light speed so the entire property of the object changes. If it carries some human being (which is also composed of electrons) will also undergo the same changes, which will be some thing next to fatal.