## The Quest for a Theory of Everything

Deep in the human unconscious is a pervasive need

for a logical universe that makes sense.

But the real universe is always

one step beyond logic.

~ Princess Irulan

(Dune, Frank Herbert)

### Quantum Mechanics and General Relativity Work Perfectly,

They Just Don’t Work Together

Einstein dropped papers in 1905 that initiated special relativity and advanced quantum mechanics. In 1915 he presented his theory of gravity: general relativity.

One of the strangest and most brilliant people involved in sorting out the implications of these new theories was Paul Dirac. Among his many contributions, he showed how quantum mechanics and special relativity work harmoniously together. This was in the late 1920s. Einstein called Dirac’s equations “the most logically perfect presentation of quantum mechanics.”

But what about *general* relativity?

When physicists tried to make the equations of general relativity mesh with the equations of quantum mechanics, the equations turned around and slapped the physicists in the face. Today, after a century of attempts to reconcile general relativity with quantum mechanics, it’s still a train wreck.

As a result, many theorists have attempted to formulate a more basic theory that will encompass *both* general relativity *and* quantum mechanics. A theory of everything. Well, everything *physical*, that is. Life, love, and the meaning of existence are not included in the package.

There are many proposals for such a theory, and new ideas crop up regularly. Two of the leading hypotheses are **string theory** and **loop quantum gravity**, which I attempt to describe in the book.

To my knowledge, none of these hypotheses make predictions that are both *unique* and that *can be tested *with current technology. So to my mind, all of these proposals are hypotheses, not theories. I’m looking at *you*, string “theory.”

I just thought that even though these proposals are pretty “out there,” they are worth including in this little book. They represent some of the most recent thinking about why stuff falls down, and a lot more!

### Here are the links from the text in Chapter 11:

92. Deeper Dive “Hypothesis vs. Theory: The Difference Explained | Merriam ….”

https://www.merriam-webster.com/words-at-play/difference-between-hypothesis-and-theory-usage

93. Deeper Dive “String theory – Wikipedia.”

https://en.wikipedia.org/wiki/String_theory

94. Physics-Speak “Supersymmetry | CERN.”

https://home.cern/science/physics/supersymmetry

95. Physics-Speak “Calabi–Yau manifold – Wikipedia.”

https://en.wikipedia.org/wiki/Calabi%E2%80%93Yau_manifold

96. Physics-Speak “Loop quantum gravity – Wikipedia.”

https://en.wikipedia.org/wiki/Loop_quantum_gravity

97. Biography “Carlo Rovelli – Wikipedia.”

https://en.wikipedia.org/wiki/Carlo_Rovelli

98. Physics-Speak “Entropy – Wikipedia.”

https://en.wikipedia.org/wiki/Entropy

99. Physics-Speak “The fabric of space: spin networks « Einstein-Online.”

https://www.einstein-online.info/en/spotlight/spin_networks/