Unification of gravitation with other forces

[cryptist]

Why physicists are trying to unify gravitation with other 3 forces (weak, strong, e&m)?

What if gravitation is actually not a force but a consequence of the mass's disturbance in space-time geometry? (like Einstein proposed)

I don't understand their persistence on this unification. Maybe gravitation has different nature than other forces, and we can still seek for a theory of everything.

Is it only the struggle of adaptation to proposed models (like standard model)? Is that the only reason?

 

[Drakkith]

Scientists are trying to develop a new theory on gravity because our current one is most likely wrong. One reason we think this is because we run into an issue of having infinities start to pop out of our equations when we get to very high gravity scales. This almost guarantees that our theory is wrong and we don't understand how things work at this scale.

It isn't just to unify it. Unlike string theory, quantum loop gravity actually doesn't try to unify it, but mostly to figure out if gravity is quantized or not. (Like everything else seems to be)

 

[Naty1]

A basic reason for unification is that it is believed that is the way things were at the moment of big bang...the beginning of our universe... unified in a single entity. So we'd like to understand such singularities better. In addition the Standard Model of particle physics does not include gravity...because we can't combine Standard Model Quantum mechanics with gravity: http://en.wikipedia.org/wiki/Loop_quantum_gravity

LQG is an attempt to merge and adapt standard quantum mechanics and standard general relativity. The main output of the theory is a physical picture of space where space is granular. The granularity is a direct consequence of the quantization. It has the same nature of the granularity of the photons in the quantum theory of electromagnetism or the discrete levels of the energy of the atoms. But here it is space itself which is discrete.

http://en.wikipedia.org/wiki/Grand_Unification

A Grand Unified Theory, (GUT), is a model in particle physics in which at high energy, the three gauge interactions of the Standard Model which define the electromagnetic, weak, and strong interactions, are merged into one single interaction characterized by one larger gauge symmetry and thus one unified coupling constant. In contrast, the experimentally verified Standard Model of particle physics is based on three independent interactions, symmetries and coupling constants.
Models that do not unify all interactions using one simple Lie group as the gauge symmetry, but do so using semisimple groups, can exhibit similar properties and are sometimes referred to as Grand Unified Theories as well.
Unifying gravity with the other three interactions would provide a theory of everything (TOE), rather than a GUT. Nevertheless, GUTs are often seen as an intermediate step towards a TOE.

Such a unified understanding may also lead to insights about what happens at the end of our universe...and the exact fate of black holes...

 

[mfb]

Current physics cannot describe:
- how the very first moments of the universe looked like
- how the exact boundary of black holes looks like
- what happens when two extremely high-energetic particles collide (something like 10^18 times the energy achieved in the LHC)
- the origin of dark matter
- plus some theoretical issues
Basically everything where gravity and quantum theory are relevant at the same time

It is expected that a theory which allows to describe all interactions at the same time can (at least in principle) solve those issues.