Why do we need a quantum theory of gravity? What would it do?

Why do we need a quantum theory of gravity? What would it do?
 

mathman

Science Advisor
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Where both quantum theory and general relativity must apply at the same time, they can't. Example - what goes on inside a black hole?
 

DaveC426913

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Where both quantum theory and general relativity must apply at the same time, they can't. Example - what goes on inside a black hole?
Well, "where [they] must apply at the same time" is understating the problem. To claim we understand our universe, they must be applicable at the same time EVERYWHERE and EVERYWHEN. Otherwise, our understanding is fundamentally incomplete.

Two of the greatest scientific theories in the history of civilsation - turn out to be incompatible. They can't both be right. Yet, they are each one of the best-confirmed theories in history.
 
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Wow. What makes them incompatible?
 
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Well, "where [they] must apply at the same time" is understating the problem. To claim we understand our universe, they must be applicable at the same time EVERYWHERE and EVERYWHEN. Otherwise, our understanding is fundamentally incomplete.
I don't think we will ever really understand our universe.
 
I think we'll get it. It may take a while, but I definately think we'll get it... if we dont destroy ourselves in the process...
 
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Quantum mechanics describes the actions and interactions of the extremely small, the particle level. Relativity describes massives amounts of matter, planets, stars, and such. They both are highly accurate as was mentioned, but when they are both applied to the same body/particle, they seem to fall apart. Why exactly?

I'm not 100% but it's the mathematics of them that does not lend itself to be compatible. As was mentioned with black holes, it's a huge amount of mass, but a terribly small, point-like structure.

Think of black holes almost as, what happens when both theories collide, and do we know exactly what goes on at the singularity? Nope.

The modern quest of physics is what is called a TOE (theory of everything) in which everything can be described in one ecompassing theory. Quantum Mechanics describes 3 forces (Nuclear Strong and Weak, and Electromagnetism) while relativity describes Gravity. When we are able to combine all of these into one theory, we will hopefully accomplish that.

One of these proposed theories is String Theory.

A very good question you asked, and i hope i am right and have clarified a little.

Good luck! =)
 
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I think we'll get it. It may take a while, but I definately think we'll get it... if we dont destroy ourselves in the process...
No i don't think we'll never know/learn every knook and crany in our universe. To learn everything would take forever.
 

disregardthat

Science Advisor
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Well, who can predict the future? It's useless to debate about this.
 
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no one can but i don't think we can learn everything the universe has to offer
 
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Thanks doug. very helpful post
 
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your welcome, i try =) ha
 

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