How is speed of light constant and time is not same everywhere?
Answers
the paritcles of light are called photons.
these photons do not carry any type of charge and negligible mass. but some theories say there is no mass. due to which light's speed is not being affected by the electric and magnetic fields. but in the cases of light entering a medium it's direction and speed gets changed. this also happens when light just glides over an object or near a super massive heavenly bodies.etc . these are all properties of light. and except these it's speed is always the same 299,792,458m/s you n vacuum.
from Einstein's theory of relativity, time is not same everywhere. it changes according to the position in the space. the theory says that the objects in the space bend the space time fabric, making time to pass differently. this effect is significantly seen in a black hole. the twins paradox also is based on time dilation.
hope this helps you out. for more information, please visit crash course, veritausium , kurzgesagt and more in YouTube.
thank you!