Loop quantum gravity explained | COSMOS in a minute #31

Loop quantum gravity is a fascinating attempt to understand the universe at its smallest quantum level while also considering gravity. It attempts to reconcile general relativity and quantum mechanics by quantizing the spacetime continuum. Imagine the fabric of space-time as a knitted sweater. In everyday life, we see the smooth surface of the sweater, just like how we experience space-time as a continuous flow. However, if we look closely, we'll see the sweater is made of individual loops and knots. In loop quantum gravity, space-time is similarly made up of tiny, discrete, or separate loops. An advantage of this theory is that it is free of singularities, which are regions of spacetime where the laws of physics break down. Loop quantum gravity is a promising idea that has the potential to revolutionize our understanding of gravity.

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[danrazART]

Basically, string theory wearing pants! 😂

[stephencindrich]

Bending over backwards has never been so difficult.

[jeffsuriano]

Without singularities, how do you explain the center of a black hole??

[armygirl]

I love this chanel it helps me to increase my language skill and it helps to know about space ❤

[frankcastle]

I still love to believe that if Einstein were accepted for his work earlier that he could have unraveled far more.

[alllove]

This is correct so far.. I don't know about the singularity part though. I felt it was true

[michaelkahn]

The problem of modern physics is they're trying to explain everything with particle physics and the physics is being cornered more and more to the dead end.

The interaction between mass and space must be explained with quantum mechanics.
But that doesn't mean gravity is the QM phenomena.
That's because gravity is not a force.
Gravity is just a joint effect of the expansion of the Universe and the curvature of spacetime.
Details are given below.

Alternative Explanation of Dark Matter and Dark Energy - Newly proposed model of Universe can explain both of Dark Matter and Dark Energy

Einstein’s theory of General Relativity states that spacetime is curved by the presence of mass.
This curvature influences the motion other objects with mass and gives rise to gravitation.
Thus, gravity is a result of geometric features in spacetime.
However, we also observe gravitational effects – curvature of spacetime – in areas without any detectable mass.
This has given rise to the concept of dark matter, which is matter that does not interact in any detectable way with normal matter, except through gravity.
So, there is some large quantity of dark matter scattered throughout the universe, which curves spacetime and causes gravitational effects just like normal matter, but we cannot see or detect it with any known method.

An alternative theory to the identity of dark matter is proposed – it is not matter at all, but rather an intrinsic curvature of spacetime.
In other words, spacetime is not naturally flat. Even in the absence of matter, we observe some inherent curvature of spacetime.

So, the question is now – why is spacetime naturally curved? Why is it not flat in the absence of mass?
The universe is 4-dimensional, with 3 spatial dimensions and one dimension in time.
Rather than consider time as a linear dimension, we can consider it as a radial one.
Therefore, rather than describing the universe with a Cartesian coordinate system, we describe it with a 4-dimensional spherical coordinate system – 3 angular coordinates, φ1, φ2, φ3, and one radial coordinate in time, t.
We live on the 3-dimensional surface of a 4-dimensional bubble which is expanding radially in time.
Thus, the Big Bang represents t=0, the beginning of time.
The crucial point is that the expansion of the universe is not homogeneous in all directions.

The expansion rate at one point on the bubble’s surface may differ slightly from another point near it.
The universe is only roughly spherical in 4 dimensions, the same way that the Earth is only roughly spherical in 3 dimensions.
The same way we observe local mountains and valleys on the surface of Earth, we observe local “mountains” and “valleys” on the surface of the universe bubble.
The inhomogeneity of the expansion of the universe has given rise to natural curvature of spacetime. This natural curvature causes the phenomenon of “dark matter”. “Valleys” in spacetime pull matter in, similarly to the warping of spacetime of massive objects.
So “dark matter” is really “valleys” in spacetime that are expanding slower than the regions surrounding it.
These valleys tend to pull matter in and create planets, stars, and galaxies – regions of space with higher-than-average densities of mass.
Conversely, “mountains” in spacetime will repel matter away, an “anti-gravitational” effect, which gives rise to cosmic voids in space where we observe no matter.
Each point on the surface of the universe bubble traces out a time arrow in 4-dimensional space, perpendicular to the surface.
These time arrows are not parallel to each other since the universe is not flat.
This causes points to have nonzero relative velocity away from each other.
It is generally accepted that the universe is expanding faster than observable energy can explain, and this is expansion is believe to be still accelerating.
The “missing” energy required to explain these observations has given rise to the theory of dark energy.
The time dilation caused by non-parallel time arrows can be proposed as an explanation for dark energy.

Alternatively, dark energy is real energy coming from potential energy gradients caused by non-parallel time arrows.
As a sanity check, we can calculate the expansion rate of the universe based on the universe bubble model.
Since the radius of the universe bubble is expanding at the speed of light in the time direction, it increases at 1 light second per second.
Therefore, the “circumference” of the 3-dimensional surface increases by 2π light seconds per second, or about 1.88*10^6 km/s.
This expansion is distributed equally across the 3-dimensional surface, so the actual observed expansion rate is proportional to the distance from the observer.

At present, the age of the universe is estimated to be 13.8 billion years, so the radius of the universe bubble is 13.8 billion light years, or about 4233 megaparsecs (3.26 million light years to 1 Mpc).

Thus, we can calculate the expansion rate of the universe, per megaparsec from the observer, as:

Expansion rate =

The popularly accepted empirical expansion rate is 73.5 + 2.5 km/s/Mpc, so our calculated value is close.
There may be some additional source of expansion (or observed red shift) to make up for the discrepancy. For example, if two adjacent points have some gravitational gradient due to non-parallel time arrows, then light passing through these points will be red-shifted.

[Montycarlo]

My take on gravity as a whole because everything in the inverse is energy just many different branches. Gravity is quite literally entanglements and is the specific frequency in the universe vibrational wave that leads to continuous reality as we see it of course like blackholes something is preventing gravity from falling in on itself, something stops that process from occurring bring it back to a full revolution or continuous constant, well that’s how i’d like to assume you’d visualise gravity in quantum action

[ThanksIfYourReadIt]

LoL, i was preaching this idea FOR FUCKING EVER.
That reality is going of a clock of existing and non existing depending on the amplitude of the energy at any point. And the motion of the frekvency going up and down causes innertia in space that casues a predictable displace which is the kinetic force of "gravity".

[Darkhorse]

Sure, but it all goes to heck with the introduction of a black hole!!

[atulvashisth]

ऐसा लगता है| जैसे कि बुना हुआ स्वेटर हैं|

[amartyasharma]

Everything in science is imagination

~Alakh pandey

[FixingPhysics]

People love the idea of singularity even though there is no experimental evidence (science) that the properties of space are inconsistent because we are innately superstitious and love fantasy. People get very excited by notions of time travel and multiple dimensions which is why these unscientific concepts appear frequently in TV and film.

[Baldevi]

I find this very intriguing, myself. And I get the No Singularities thing; this is not a denial of Black Holes, but simply means that their presence and nature are still unknown and that any theory for Space, the Universe as a whole will break down at the Black Hole Singularity. Since this is already true [for the time being] this is not a real problem for this theory.
Explaining Singularities such as Black Holes and the possible Singularity that was the pre-birth Universe is simply beyond our ability at this time; their existences simply provide the exception to the Rules within which the Universe abides. It's not really that confusing, is it?

[tttangable]

Quantum does not really represent an obsession with particles smaller than the atom. Quantum recognizes the interconnection of the four forces (quad) amongst a more diverse array of particles some larger than the atoms proton some smaller . With effect on forces other than just electromagnatism, unlike the electron in the atom orbital . For example the Higgs mass interaction effect heavily effects gravity. The Higgs field determining mass, thus determining the sink size in space time. Still officially only four forces. When you search the description you will be told that quantum is used as a quantity. . I theorize that quantum physics base represents the quantity of the particles effect on the four forces (quarters) in a particle quantum .

[ambyamby]

I mean we can already use the Planck constant and with hawking's equations we are going to reach this level soon.

[nvrt]

I don't believe in infinite space, but also don't believe in space coming to an end. I just believe that space loops back to itself if you were to go in any single direction long enough. Does this make me a loop quantum gravity believer? Or am I just full blown stupid?

[oldmech]

Very interesting for an alternative theory. So you do not embrace the mod gravity theory? Makes life simple.

[MrZiypah]

Time is a straight line.. not a loop. This theory belongs in the syfy section.

[NothingMaster]

KEEP IN MIND: If it is not falsifiable, it’s neither science nor theory. For now, and not unlike String Theory, LQG, too, remains little more than a mathematically-based philosophical reverie.