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8/15 ~ p. 127 
 
General Relativity vs. Quantum Mechanics 
 
- The absence of mass means that space is flat in the large scales of general relativity. 
- At the quantum scale, everything is subject to quantum fluctuations of the uncertainty principle, even gravity. 
- Uncertainty principle - two physical properties of a particle cannot be known simultaneously because observing one disturbs the certainty of the other. Increasing the intensity of light used will increase the precision with which the location of the particle can be determined but the higher frequency photons will disturb the velocity of the particle. So both velocity and location cannot be known simultaneously. 
- General relativity does not work at the quantum level because quantum fluctuations cause empty space to occasionally have more than the zero gravity that classical reasoning suggests. 
- When the attention is focused on smaller regions of space, greater undulations of gravity are observed. 
- At increasingly small levels, space and time is warped dramatically so it no longer resembles the flat, flexible nature of space and time in general relativity. This space is known as quantum foam. 
 
What does this imply for our lives that at some level everything that makes us up is completely different from what we conventionally perceive to be normal? Discoveries like this could show that our lives are completely different from what we perceive them to be. It shows how little we understand that we cannot even understand the connections between the large and the small like general relativity compared with quantum mechanics. 
 
 
8/29 ~ p. 129 
 
- Calculations that merge the equations of general relativity and those of quantum mechanics result in the answer of infinity. 
- The unusual fluctuations of quantum mechanics balance each other out as we reach more ordinary distances that we are used to. So space-time seems smooth and flat at distances that we are used to that involve general relativity. 
- The incompatibility of general relativity and quantum mechanics points to an essential flaw in our understanding of the physical universe. 
 
Although some physicists are willing to ignore the incompatibility between quantum mechanics and general relativity, many are so unsettled by it that they have a main goal of resolving the conflict. I don't understand how any physicists could be aware of this incompatibility but not work to find a solution. Even if their area of work can do perfectly fine with general relativity and quantum mechanics as they are now. It threatens their very core beliefs about the physical world.