Eli5 if time is relative and gets effected by gravity how could we possibly determine the age of our universe?
In: 843
First, time itself isnt relative.
Its the ***passage*** of time, from our frame of reference, that is relative. How we experience that passage of time does not change the abstract “age” of what we measure.
**Example**: My youngest daughter is “20 years old”. That is, she has grown and physically matured from an infant into a young adult woman.
In our normal worldly frame of reference, the process took my daughter 20 years to reach this point of her growth.
If I were to hop into a spaceship travelling close to the speed of light when she was an infant, then came back, and the trip took me 10 minutes, from my frame of reference (on the spaceship), those 20 years passed by in 10 minutes.
Just because I (*the person on the space ship*) happen to experience the passage of time for my daughter to grow up from an infant into a young adult in 10 minutes, doesnt mean she is 10 minutes old. She is still 20 years old, because from her frame of reference, it took 20 years, not 10 minutes.
So her “age” remains constant, but from 2 different frames of reference, how she and I experienced her passage from infant to young adult was different.
Its the same process for measuring the “age” of the universe. The age is constant, but we just experience the universe’s aging at a different (relative) reference frame.
If you were to hop into a spaceship going close to the speed of light, you would witness the universe’s aging process happening, but at a quicker pace. If you, on your spaceship, called me up and asked me to measure the universe’s age alongside with you, we would both end up with the same result, that being the “age” of the universe at that specific point in time.
Latest Answers