At some point in our life, we’ve all entertained the idea of time travel; the idea of seeing the future or living in the past…but is it actually possible? Well, technically yes – but the effects are minute and unnoticeable. You may be wondering how this is possible – well, this is possible by understanding time dilation.
What is time dilation?
Time dilation is the difference of elapsed time between two events as measured by observers, as related to relativity. It can happen for one of two reasons:
- Reason 1: A difference in velocity relative to each other (not covered in this article)
- Reason 2: A difference in positioning relative to a gravitational field
Gravitational time dilation falls under Einstein’s theory of general relativity, whereas velocity time dilation falls under special relativity.
What is gravitational time dilation?
Gravitational time dilation is one of two forms of time dilation. This is where you measure the difference of elapsed time between two events by two observers with a difference in situation relative to a gravitational field.
In short – gravitational time dilation is the occurrence where time runs slower wherever gravity is strongest, as gravity curves space-time.
The prospect of a four-dimensional fabric was proposed by Herman Minkowski as a way to reformulate Einstein’s theory of special relativity. This challenged previous, widely regarded assumptions that one-dimensional time was dependent of the three-dimensional geometry of the universe. In physics, space-time is any model that fuses the three dimensions of space and the one dimension of time into a singular four-dimensional fabric or continuum.
Space-time: the faster you travel through space, the slower you travel through time.
Through this singular four-dimensional continuum, Einstein could explain how gravity exerts its pull. Einstein suggests that massive objects curved the fabric of space-time around them. Imagine placing a bowling ball on a trampoline, the weight of the ball would curve the trampoline. Now imagine the ball is earth, and the trampoline is a four dimensional fabric.
Earths mass forces the fabric of space-time to bend around us. We are pinned to the ground, as space is so distorted from the earths mass that is pushes down from above. As we move towards the centre, Earths gravity grows increasingly more intense as the curvature draws closer to a maximum.
Now how does this link to time travel?
Imagine someone falling from the atmosphere; they would start to speed up as they grew closer to the centre of the earth (due to gravity dragging them down). We already know that the faster you travel through space, the slower you travel through time. This means that time runs slower on the earths surface than in does above in the atmosphere, granted the difference is minute, but it’s still there.
Therefore, astronauts currently residing in the ISS are currently travelling quicker through time than people (us) on the earth’s surface! Therefore, when they are looking at the earth’s surface, they are actually looking back in time – this difference in time is tiny, but it’s still there!
This theory becomes more interesting when you start thinking about bigger celestial objects such as black holes. Because black holes cause a huge (absolutely massive) distortion of space-time, time runs incredibly slow the closer you get to a black hole – in fact, an observer from a distance will never see something fall into a black hole as time actually stops at the edge of the black hole!
References:
“What Is Gravitational Time Dilation.” Http://Users.Sussex.Ac.Uk/~waa22/Relativity/What_is_gravitational_time_dilation.Html, users.sussex.ac.uk/%7Ewaa22/relativity/What_is_gravitational_time_dilation.html. Accessed 13 Nov. 2020.
Wikipedia contributors. “Gravitational Time Dilation.” Wikipedia, 12 Nov. 2020, en.wikipedia.org/wiki/Gravitational_time_dilation.
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