Gravity in Einstein's Way

All of us have been familiar with ‘Gravity’ ever since we were born. We can feel it, as our weight, falling towards the Earth, during rain, while skiing and when we lift something (how heavy it is..😓?) and whatsoever.

Gravity can be defined as a sense of feeling that “how heavy something is?” or “how much mass it has?”

We know that we can feel gravity and see its resultant phenomena but ‘what gravity actually is’?, ‘What about its physical existence’?

Let’s understand the gravitational force with same perspective, in which Einstein pictured it. You can see the image and imagine the whole space as a time and space fabric that goes through everything in this universe. Any mass that is accumulated through gravity distorts this space time fabric, and moves through it.

Don’t just think that there is a single layer and the Earth is sitting and rolling over it. Imagine this as a 3 dimensional or think of it like a 4 dimensional fabric that goes through the things, but its material effect feels like having a 2 dimensional fabric. It’s like something is happening in higher dimension and the effect is seen in the lower dimension and we observe it here.

Einstein said that it is due to this trough in the Space-Time fabric, the other objects tends to fall into it or on the massive body like planets, stars, pulsars and even small asteroids. When an object tends to fall in the space-time trough made by another massive body it goes to surround that massive body due to the conical phase of space-time or curved space-time around that massive body and will continue to revolve around that massive body.

Let me explain this by taking the example of our Sun and Earth…

Space Curvature Around Sun

The Sun is the center and Earth revolves around it from about 4.5 billion years, ever since it was born. The Sun is very massive and thus it curves the space-time or Fabric of the Universe to a very huge extent. Earth is in the curve made by the Sun, so either Earth will directly fall into the Sun or it will overcome the slope (curve) revolving around the Sun (centripetal force handles the inward push). Since there is no friction in the Fabric of the Universe thus Earth doesn’t have to pay a bit of its energy to overcome the curve’s and therefore it will continue to revolve around the Sun forever.

Sun is not the only one in this system who has its own space-time curve, Earth too has its own space-time space-time curve, the revolution that we observe that Earth revolves around Sun is the net affect i.e Sun also revolves around Earth but since Sun is so large thus its effect overshadow the effect of Earth on it.

In fact, everything in the universe that has mass makes its own space-time curve and is connected with every object of the Universe (though the force may be very very faint at infinite distances) & that is the reason why we call Gravity, a long range force (till infinity).

You might have heard that if an astronaut takes a spoon in space, it will start to revolve around that astronaut. This is obvious because the astronaut has much more mass than the spoon and thus makes enough trough or curve in the space-time or fabric that can revolve a spoon around the astronaut. Just as the example of Sun & Earth, here Sun=Astronaut & Earth=Spoon.

Gravitational Waves

Gravitational Waves are the disturbances in the fabric of space-time caused by the moving of massive objects far away in space. The intense speed of moving along with their massive mass disturbs or shakes the space-time fabric intensely and results in high energy gravitational waves. These types of waves are only created by massive objects like black holes, neutron stars, pulsars or by massive events like supernovae (explosion of a star at the end of its lifetime).

You can also illustrate it by taking the example of water’s uppermost layer as the 2 Dimensional layer of space-time fabric and then try to float an object on it, then you will observe waves forming on the water surface. Also you may know that no water gets transported, its only the flow of energy in the form of waves.

This energy can be transformed into matter as $m= \frac{E}{c^2}$. Do you think that this energy can be transformed into matter somewhere? Does this kind of phenomena happen anywhere? Could it be that we can transfer matter in the form of energy and reconstruct the matter there?

You can see in the above GIF that two neutron stars are revolving around each other at super high speed around their center of mass. And this system releases intense energy in the form of Gravitational Waves.

Gravitational waves are super powerful and can squeeze & stretch the space-time and whatever comes in its path like waves. So it is proved to be very dangerous if it is generated closer. Though in spite of the danger, they bring very precious data about their origin and from which type of object and event it originated in the past. Therefore Gravitational Waves are worth a lot for scientists, since they can help us to reveal the mysteries of the Universe. Gravitational waves are hard to detect and thus scientists use special devices on a huge scale to catch even the faintest Gravitational wave coming from deep space.

There are many observatories in the world in different countries that are dedicated for the research on “Gravitational Waves’ ’. One such well known observatory is “Laser Interferometer Gravitational wave Observatory” or (LIGO). LIGO is a large-scale research program that is dedicated to study and gather data on ‘Gravitational Waves’. It is situated at Hanford Site, Washington and Livingston, Louisiana, US.

Einstein’s “Greatest Blunder” and Dark Energy

When Einstein first developed General Relativity, his equations implied that the universe must be either expanding or contracting. To force the universe to be static — as was believed at the time — he introduced a “cosmological constant” into his equations, a mathematical fix he later famously called his “greatest blunder.” However, modern astronomy has discovered that the expansion of the universe is actually accelerating. Today, Einstein’s cosmological constant is the leading mathematical explanation for dark energy, the mysterious force driving this cosmic acceleration.

Wormholes

Wormholes are said to be a type of Gravitational tunnel. We are aware of the fact that a wormhole can connect two really very far points or places in space like a shortcut tunnel. Wormholes are actually the super curved space time fabric that connects with the other part of space time fabric like an underway tunnel. For better understanding see the figure given below.

Wormholes are really very cool but it may not be safe traveling through them without proper study and research and effects on the human body and mind. Wormholes are a really great way of traveling throughout our galaxy as we watch in many science fiction movies.

Can we ever make a travelling technique faster than light? According to Einstein, it is not possible to travel faster than light in our universe.

The Quantum Conflict

While Einstein’s General Relativity beautifully describes gravity on a cosmic scale, it fundamentally clashes with the subatomic world. At the microscopic level, forces are governed by discrete particles and probabilities, an arena where gravity simply refuses to fit in. This profound incompatibility between classical gravity and the quantum realm is one of the greatest unsolved mysteries in physics. To bridge this gap, modern physicists look to theoretical frameworks like string theory, aiming to unite all fundamental forces.