Recent Changes

9/1 Pg. 166
- Symmetries of nature - Nature treats every moment in time and every location in space identicallly by ensuring that the same fundamental laws are in operation.
- Particles spin.
- Matter and antimatter particles have a speed of "1/2 speed." Non-gravitational force carriers have a spin rate of twice that of matter particles: "spin-1." Gravity's spin rate is "spin-2"

- Quantum-mechanical probability - prevents physical objects from randomly disappearing from the universe without a trace (I just thought it was awesome that they have a word for that, Alex :) )
- Point particle quantum field theory description of a collision between an electron and positron: The two particles slam together, annihilating each other, producing a photon. The photon then produces another electron and positron. Question~ Why does it produce another electron and positron?
9/1
- String theory implies that a particle is 1 dimensional instead of having zero dimensions as with Point particle physics.
- With point particle physics, infinite answers result when the graviton is incorporated in particle reactions.
- Strings spread out force of the gravitational force, lowering it enough to produce finite answers.

- The negative for particle physicists here is that particle acceleration cannot be used on sub-Planck-length distances. Question~ If such an apparent difference exists between strings and point particles, shouldn't we be able to determine whether or not particles are points or strings based on whether the accuracy of particle probing increases on sub-Planck-length scales? Or is this beyond our technological or observational capabilities?
- The implication of this is that strings cannot detect quantum undulations smaller than Planck-scale. This smoothes out the incompatibility between general relativity and quantum mechanics.
- In string theory, there is NO WAY to expose the sub-Planck-scale "imperfections" in the fabric of space. According to this, the conventional notion that we can always observe something on smaller and smaller distances is untrue. So someone who must be able to observe and measure something to believe that it exists would claim that they do not exist at all because they cannot be measured. Question~ What precisely stands in our way of being able to observe the sub-Planck undulations? Is it simply that we cannot see the effects of them on the strings?
"A Sleight of Hand?"
- The problems between quantum mechanics and general relativity were essentially of our own making if string theory is to be believed. Because we so adamantly believed that particles were points and didn't hardly question it previously, we ran into problems as we went down to smaller and smaller scales. It took a very radical theory like string theory to strike at science's very core beliefs in order to find a logical solution.
- According to string theory, there is a limit on how closely we can observe the universe and the reason we encountered such problems on the microscopic scale is because we believed that we could infinitely measure the universe so long as we had the technology.
- Quantum-mechanical probability - prevents physical objects from randomly disappearing from the universe without a trace (I just thought it was awesome that they have a word for that, Alex :) )
- Point particle quantum field theory description of a collision between an electron and positron: The two particles slam together, annihilating each other, producing a photon. The photon then produces another electron and positron. Question~ Why does it produce another electron and positron?

8/30 Pg 152
- On sub-Planck-scale, the quantum undulations are so violent that they destroy the notion of a smoothly curving geometrical space causing general relativity to break down.
- A more detailed description of a particle accelerator can be determined when smaller particles are shot at it in a particle accelerator
- Higher energy particles are able to more accurately observe details of a particle when collided because the margin of error when using a point particle as a probe is directly related to its wavelength. So an increase in the energy of a particle shortens its wavelength, increasing the accuracy of the collision. This is why such enormous distances are used in particle accelerators such as the large hadron collider to accelerate particles to enormous speeds close to the speed of light.
- A string on the other hand that is smaller than Planck-length when given enough energy will actually be caused to GROW from the energy it receives as opposed to a point particle which will continually increase in probing accuracy. A string will behave like a particle until it reaches the Planck-scale. Question~ Why is the Planck-scale such an important point for a string specifically?
- A string could actually be caused to grow to macroscopic scale if it was given enough energy as was available during the big bang.
- The negative for particle physicists here is that particle acceleration cannot be used on sub-Planck-length distances. Question~ If such an apparent difference exists between strings and point particles, shouldn't we be able to determine whether or not particles are points or strings based on whether the accuracy of particle probing increases on sub-Planck-length scales? Or is this beyond our technological or observational capabilities?
- The implication of this is that strings cannot detect quantum undulations smaller than Planck-scale. This smoothes out the incompatibility between general relativity and quantum mechanics.

- Fundamental strings have far greater tension than examples of strings that we are used to. The Planck tension is a thousand billion billion billion billion tons which is the proposed tension of the string of a graviton.
- A string with greater tension will have more energy than a string moving in the same way with less tension because more energy is required to set the first string in motion.
- The natural energy produced a proton.
9/28 Pg. 150
- Natural energy of a string is cancelled out by the negative energy of it, reducing its energy by about Planck energy, resulting in low energy vibrations.
- Mass of the top quark is about 189 times that of the proton – Question: How is this possible if quarks make up protons? Is it cancelled out by quantum uncertainty?
I spent 30 minutes thinking about one page. Yeah.

9/27 Pg 142
- Just as the different vibrational patterns of a violin string give rise to different musical notes, the different vibrational patterns of a fundamental string give rise to different masses and force changes.
- Greater amplitude and shorter wavelength creates strings with greater energy.
- Special relativity tells us that greater energy means greater mass, therefore strings with more energy (more frantic vibrational patterns) have more mass. Heavier particles have strings that vibrate more frantically
- One vibrational string pattern matches perfectly with the properties of the graviton, ensuring gravity's importance in string theory.
- Unlike the standard model, string theory theorizes that everything is made of the same stuff. In the standard model, different particles where "cut from a different fabric." In string theory, different particles are just the same strings of energy vibrating differently
- Using mathematical descriptions we can theoretically "pluck" a string to observe different possible vibration patterns. Many string theorists believe that the math required for doing this was on the verge of being able to explain every detailed property of the universe on its most microscopic level.
- Fundamental strings have far greater tension than examples of strings that we are used to. The Planck tension is a thousand billion billion billion billion tons which is the proposed tension of the string of a graviton.
- A string with greater tension will have more energy than a string moving in the same way with less tension because more energy is required to set the first string in motion.
- The energy produced by elementary particles in string theory are multiples of Planck energy which is the massive amount of some ten billion billion times that of a proton.

8/17 ~ P. 135
- The standard view of particles as point-like objects with no internal structure fails when used with gravity because of the fluctuations that occur at distances smaller than Planck length.
- String theory - particles are not point particles but are one-dimensional strings that vibrate.
- String theory resolves conflicts between quantum mechanics and general relativity.
- Euler's function is over 250 years old and was found to have accurately described the interactions between particles.
- The nuclear functions of particles as strings can be described with Euler's function.
How did a physicist long before quantum mechanics figure out an equation that can describe microscopic interactions accurately via a concept that had not been thought of yet. Was he aware of what his function implied about the nature of particles?
- String theory soon became unpopular due to it failing to describe the strong force.
- String theory was expanded to include all the forces and was shown to work beautifully with major developments in physics and even provide a fuller explanation than the standard model. Led to "first superstring revolution"
- "The moment you encounter string theory and realize that almost all the major developments in physics over the last hundred years emerge– and emerge with such elegance– from such a simple starting point, you realize that this is incredibly compelling theory in a class of its own."
In science, things can often seem to be an obvious failure just because you are looking at it from the wrong perspective as happened with string theory. People become hesitant when a theory muddles in their core belief systems about what makes up the universe when in reality, the best way to reach the truth is to question everything you believe. The simplicity of string theory is what makes it so unexpected as well as threatening to the basic concepts of physics.

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.