Evolution of Time Perceptions
In recorded history, the concept of time has been grossly misunderstood as our ever evolving sciences have demonstrated. Early philosophers sensed that it was related to change and motion. Newton believed time was a constant unchanging field across all of creation marked by cycles and seasons. Eastern Religions preached a cyclical nature to time, early Christianity preached that is was preordained. The Book of Ecclesiastes tells us There is a time for everything, and a season for every activity under the heavens: a time to be born and a time to die... a time for war and a time for peace.
In 1904 the theory of relativity was published and our understanding of the true nature of time has been growing ever since. Relativities author Albert Einstein once stated "The distinction between the past, present and future is only a stubbornly persistent illusion".
Einstein, either by coincidence or inspiration formulated his theory of relativity in the ‘Watch Valley’ of Switzerland. The region is famous world wide for creating the greatest timepieces of the Western World. Einstein concluded that a watch measures motion rather than an abstract quantity, ‘time’. Motion is the coupling of time and distance. Motion, is what all watches use to measure time, just as the ancients used the motions of celestial bodies to measure the seasons or the motions of sand through an hour glass.
To bring light-speed into the equation you must factor in that it is a constant in every point of space, time then becomes coupled with space or distance in this case. One of the notions that led early researchers to conclude the world was round was watching ships sail over the horizon and disappear bottom first. This same analogy can be used to understand time dilation.
We know as we watch the ship sail off, that from our perspective it will grow increasingly small, even though our intellect tells us that the ships mass has not changed, only its apparent size, it's actual size is an absolute value, roughly unchanging. It's smallness as it approaches and disappears over the horizon is an illusion.
Einstein concluded that time is no different than distance and it depends largely on the observer. To the sailor aboard ship, its size hasn't changed - but to guy on shore watching it sail over the horizon it has. The time on a finely tuned Swiss watch depends on who’s looking at it also, if you’re moving at a great enough speed, approaching light speed that is, the watch will appear to work in slow motion, he called this time dilation.
Now comes the illusion factor, while our intellect will tell us the ships mass hasn't changed even though our brain and perception has failed to adapt to it. Our brain also doesn't adjust for time-space. Twinkle Twinkle little star is really really very far despite that its only a speck in our night sky - it's also very huge.
All objects / matter has its energy distributed between mass and kinetic/potential energy, Einstein’s famous E = mc^2.
E = energy (measured in joules, J)
m = mass (measured in kilograms, kg)
c = the speed of light (measured in metres per second, ms-1), but this needs to be "squared"
So basically energy is equal to mass + speed of light [squared]
A photon is a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency but has no mass, which is why it is able to move at light speed - because it is light.
With zero mass all of its energy must be in perpetual motion. Which is what we easily observe, photons never cease moving and they move at a constant velocity. If an entity was or could be composed of Photons, they wouldn't have to worry about time as technically they can't see time. By moving at the speed of light time would cease to exist for them. As of yet we haven’t figured out how to reach their velocity to see what they see - if anything at all.
Gravitational Time Dilation
Relativity also states that massive objects can cause a distortion in space-time, which we experience as gravity. While Newton believed that the flow of time was like a perpetual arrow that moved unflinchingly forward. Einstein hypothesized that time flow varied. Einstein claimed that space time was a flexible 4-dimensional fabric. He dubbed it the fabric of space-time.
Matter stretches and contracts the fabric of space-time, the same as a bowling ball or marble on tightly stretched fabric sheet would stretch or contract the sheets fabric. Objects are basically affixed to the Earths surface, rather then pushed down to its core by the warped space above them. The curvature of space-time accelerates objects moving towards them, from our perspective - downward. The force of gravity is stronger towards the surface of Earth, where the curvature is more intense than it would be below the surface.
Gravitational Time Dilation has been proven by noting that atomic clocks at different altitudes (and therefore different gravitational potential) will 'over time' show different times. The effects in these Earth-bound experiments are incredibly minute, with differences being measured in nanoseconds.