Saddam Hussain

Developing skills in today time is essential, and its fun and above all its natural. You can do this just by merely, start the thing whatever you want to learn. Just start. Like you can read, self-motivated books one example is cal Newport- how to become a straight-A student. One more book is the compound effect. If you can read this book and finish in 15 days, you can learn any skills you want. 

Yeah, sure. It will help. You know in this lockdown you have not met your classmate, either your regular teacher. Your whole study habit got disrupted. You need someone to discuss your subject, obviously an expert, who can guide you and also after healthy discussion, you will feel fresh and new. Online tuition is an excellent thing for all time. It's kind of supplement to your study diet. 

To answer this question, one needs to answer, what do mean by why? What's the intention to ask. One can ask why solid is solid, or liquid is liquid. For light, it is made up of photons, which has zero rest mass. At the time of origin of the universe, photons were there.

Somehow, the world has a cosmic speed limit, and any particle which can have that limit is massless. So, any object which has mass zero or says particle moves with the speed of light.

Another example is a graviton or gravitational waves. So, light happens to be one of the particles which mass is zero. And in every inertial frame, this cosmic limit must be the same. It can't be different. Note, I have said any inertial frame. I am not talking about the non-inertial frame.