A Tale of Two Horizons in Scientific American of September 2022
This document contains comments about the article A Tale of Two Horizons by Edgar Shaghoulian In Scientific American of September 2022.
How competing teams of researchers made the first breakthroughs in one of the deepest mysteries in physics
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https://www.scientificamerican.com/article/blackholediscoveryhelpstoexplainquantumnatureofthecosmos/
Reflection
"Introduction"
page 42

Where did the universe come from? Where is it headed?

The answers on both questions is speculation.

Answering these questions requires that we understand physics on two vastly different scales: the cosmological, referring to the realm of galaxy superclusters and the cosmos as a whole, and the quantum—the counterintuitive world of atoms and nuclei.

And if we don't understand both completely, the cosmos and the quantum, we cannot answer these questions. That is the reality.

For much of what we would like to know about the universe, classical cosmology is enough.

What is classical cosmology? and how do we know that?

This field is governed by gravity as dictated by Einstein's general theory of relativity, which doesn't concern itself with atoms and nuclei.

Eqations are mathematical descriptions, but they don't explain why we observe an expanding universe or why there are stars and blackholes.
Newtons Law describes the movement of objects, but does not explain why there are objects (small and large).



To understand these eras, we need a quantum theory of gravity that can describe both the electron circling an atom and Earth moving around the sun.






The goal of quantum cosmology is to devise and apply a quantum theory of gravity to the entire universe.

In fact what 'we' want is to have one theory which describes the evolution of the univerese from start to finish. We call this a quantum theory because it is based on the behaviour of the elementary particles.





But there is a palpable feeling that this time is different and that recent breakthroughs from black hole physics—which also required understanding a regime where quantum mechanics and gravity are equally important—could help us extract some answers in quantum cosmology.

In a Black the whole object is important i.e. gravity, the force of gravitation. In a gas cloud this are the elementary particles.





I expected this event to be sparsely attended, but instead many of the luminaries in physics were there, bursting with ideas and ready to get to work.

It seems as if they where sleeping....




Event Horizons

The first indication that there is any relation between black holes and our universe as a whole is that both manifest “event horizons”—points of no return beyond which two people seemingly fall out of contact forever.

To use the behaviour of humans to understand the evolution of the universe is strange.
Remember the name blackhole is also strange.

A black hole attracts so strongly that at some point even light—the fastest thing in the universe—cannot escape its pull.

Understanding a black hole (or any object) implies a better understanding of why objects are attracted towards each other. An even more important is why are there different objects in the first place.

The boundary where light becomes trapped is thus a spherical event horizon around the center of the black hole.

This explanation is based on the escape velocity of a rocket from the surface of the earth. And this implies that the description of the escape velocity of a rocket is identical as of a photon. That means both have a mass and the velocity of both is variable.
















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The Holographic Principle

Entropy and the Holographic Principle



The holographic principle states that a theory of quantum gravity that can describe black holes should be formulated not in the ordinary three spatial dimensions that all other physical theories use but instead in two dimensions of space, like a flat piece of paper.

That is a case of speculation, which requires a convincing argument why. All physical space, including all objects, including all Blackholes are 3D.

The primary argument for this approach is quite simple: a black hole has an entropy—a measure of how much stuff you can stick inside it—that is proportional to the twodimensional area of its event horizon.

That is also the case with all objects. A black hole is special because all the stuff, which makes the objects, is very compressed.
Remember this explanation uses the concept event horizon, which makes it different to understand.
















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Outside Observers
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Toward a Truer Theory

















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