# What is Time Dilation and How Does it Occur

Time dilation explained In simple words is like this – The faster an object moves through space, the slower it moves through time.

The phenomenon of time dilation is brought on by the divergence in observer time.

In relativity, time dilation is a crucial concept.

What it actually says is that if you place a clock on Earth and another clock on a rocket traveling at a high speed.

The time displayed by the clock on the rocket will then be shorter than the time shown by the clock on Earth.

That is, time has been lengthened.

This phenomenon is intricate. However, this idea is very intriguing.

### Time Dilation Explained

Imagine two spacecraft, denoted as Spaceship 1 and Spaceship 2, embarking on a journey from Point A to Point B in the vast expanse of space.

Both of these spacecraft initiate their journey concurrently, synchronized with the timekeeping of an observer, who serves as the frame of reference.

As they commence their voyage, each spaceship activates its onboard clock to record the passage of time during their respective trips.

Upon arriving at their destination, Point B, the time displayed on their clocks exhibits disparities, a phenomenon referred to as time dilation.

To illustrate, suppose Spaceship 1 takes 10 hours to complete the journey from Point A to Point B, while Spaceship 2 accomplishes the same journey in just 5 hours.

Astonishingly, both spacecraft arrive at their destination simultaneously.

This apparent paradox arises because time onboard Spaceship 1 appears to pass more slowly compared to Spaceship 2, where time seemingly moves faster.

It is essential to recognize that the observer’s perception of time may deviate from the actual experiences of the spacecraft occupants.

Consequently, the observer may observe distinct travel durations for the two spaceships.

#### But How is This Possible?

Numerous explanations exist for this.

Traveling at the speed of light or being close to an object with a very, very high mass or high gravity are two scenarios where time may appear to be slowing down.

Because it is believed that gravity theoretically bends space time, this could result in time dilation.

Either gravity or relatively higher velocity is the cause of this time dilation.

For ease of understanding, let me explain each one separately.

#### Gravitational Time Dilation (General Theory of Relativity)

Gravitational time dilation is closely tied to the behavior of light in the vicinity of massive celestial bodies.

Traditionally, we are taught in high school physics that light follows a straight path.

However, this isn’t always the case.

When confronted with the overwhelming gravitational pull of massive objects like Earth and the Sun, the very fabric of space around them becomes distorted.

Consequently, as light traverses through this warped space, it bends in response to the curvature of space-time.

There exists a wealth of empirical evidence substantiating the phenomenon of light bending near massive objects.

Understanding this phenomenon is critical because it leads to an increase in the distance that light must cover.

Light, which is fundamental in determining the perception of the timing of events, moves at a constant speed of approximately 299,792,458 meters per second (or 300,000 kilometers per second).

This speed of light remains consistent in all frames of reference, whether the observer is at rest or in motion.

Time can be calculated using the formula: Time = Distance / Speed. Given that the distance light travels near massive objects is greater while its speed remains constant, the elapsed time for an event will extend.

In other words, time undergoes a deceleration.

This phenomenon explains the phenomenon of astronauts aging more slowly when located on a planet near a black hole, where gravity is significantly stronger than Earth’s, as depicted in the movie ‘Interstellar.’

In the film, it is mentioned that one hour on the planet close to the black hole equates to seven Earth years.

To put it in perspective, light must travel a staggering 7 x 365 x 24 times the distance it would on Earth in such conditions, showcasing the remarkable warping of space-time.

### Velocity Time dilation (Special Theory of Relativity)

Consider this simple thought experiment where you are standing at a distance of 1m from a lamp holding a stopwatch that can even measure 0.1 nanoseconds.

You switch on the lamp and at that very instant you also started your stopwatch.

So the time taken by the light of the lamp to reach you would be

Time = 1 m / 299 792 458 m/s = 3.3 nanoseconds

Here the time dilation is not perceivable.

Suppose if you switch on the lamp when you are traveling close to the speed of light, the time taken would increase as you are traveling away from the lamp.

In other words, time slowed for you. However, for other stationary observers, the time elapsed remain the same (3.3 nanoseconds).

#### Real-Life Examples

1) Astronauts aboard the International Space Station (ISS) experience a time dilation effect due to their high velocity.

If they spend six months on the ISS, traveling at a speed of 27,600 kilometers per hour, they would age 0.07 seconds less than people on Earth.

This phenomenon is known as velocity time dilation.

2) GPS satellites, which also move at significant speeds, require periodic clock adjustments to stay synchronized with Earth’s clocks and function accurately.

This necessity arises from velocity time dilation.

3) Researchers from the RIKEN Center for Advanced Photonics and Cluster for Pioneering Research have conducted precise measurements of time dilation, as predicted by Einstein’s theory of general relativity.

They employed two meticulously calibrated optical lattice clocksâ€”one at the ground level and another situated 450 meters up in the Tokyo Sky-tree observatory.

This phenomenon is associated with gravity time dilation.

When an object approaches the speed of light, time dilation occurs to preserve the consistency of physical laws and the universal speed limit.

This intriguing concept of time dilation enables the possibility of traveling into the future.

In this scenario, one second for an astronaut in space is not equivalent to one second for us, forming the fundamental idea behind the concept of time travel.

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