Entangling Space

• Gravity affects time
• According to quantum mechanics, two objects, no matter how distant, can be connected
• A particle can “hang in a state of limbo” and only commits to a certain property when it is observed, this can be linked a to a non-local particle
• Light is a wave, electrons also act as waves when single
• Quantum mechanics show that all particles act as waves, having probability waves and this probability is the best we can ever calculate a particles position no matter our ability or observations
• A particle has no definitive position until it is measured; Einstein took issue with this and quantum mechanics as a whole
• The uncertainty principle states, “you can determine with precision certain features in the microscopic realm, but in doing so you eliminate the possibility of determining certain other, complementary features.”
• Einstein, Podolsky and Rosen argued that quantum mechanics is not the last word because when two particles split off moving to the left and right they will have the same speed and direction so you can know the position or speed by measuring the other which violates the uncertainty principle
• Particles spin about an axis either clockwise or counter-clockwise
• If you measure particle spin on identical particles on 3 axes you can determine if a particle has a pre-determined spin, this is found true if more than half the results of numerous tests agree, then Einstein would be correct
• The experiment was performed on photons and showed that the results are not the same over 50% of the time which shows quantum entanglement (measurement of one particle determines the attributes of a distant, correlated particle); Einstein and co. were wrong
• Entanglement does not kill special relativity because the speed of light is not broken, no information is transferred between the entangled particles
• Once a particle is measured, it’s probability wave collapses, for its location is known, it can’t be anywhere else, and this is instantaneous
• Non-locality does not rule out the possibility that particles have definitive (or “hidden”) properties

Relativity and the Absolute

• Electricity and magnetism were once thought to be distinct but are now known to be part of the same field, the electromagnetic, the two affect each other
• This field travels in waves at the speed of light which means light is an electromagnetic wave
• Luminiferous aether was proposed as a substance through which light travels so that the speed of light could be relative to something (that something being the aether)
• But experiments show that the speed of light is the same whether it is traveling towards or away
• Einstein declared there is no aether and “that the speed of light is 670 million miles per hour relative to anything and everything”
• This can only be explained by saying that observers moving relative to each other will not have the same observations for distance and time
• No matter how fast one moves, light will always appear to travel 670 million mph
• Stationary objects travel through time but when they begin to move in space some of that movement in time is diverted to movement in space which means time slows down for that object (my though: wow!)
• The combined speed of an object moving through time and space is equal to the speed of light
• This means time stops at the speed of light!
• Einstein and other claimed you would still feel spinning in an empty universe, even in relativity some things are absolute
• A region of spacetime is all things that occur in a region of space over a period of time
• Relativity of simultaneity – an observer moving relative to another will say that events are not simultaneous although the second observer declares they are
• Depending on the motion and point-of-view things appear to happen at different times and both orders are correct
• The observer in relative motion views events as if on an angled page which angle can be no more than 45 degrees because of the limit set by the speed of light
• If Newton had been correct about absolute space observers would always agree about when an event occurs
• Not everything in relativity is relative, absolute spacetime replaces Newton’s absolute space
• Objects traveling in a straight line through spacetime will be seen as such by all observers though they may disagree on how much time passes or distance is covered in each segment of spacetime
• In special relativity nothing travels faster than light, but gravity appears to be instantaneous so Einstein had to reconcile the two which he did with “general relativity”
• At a constant velocity you would feel no motion; in accelerated motion you feel pressure, as if you are being forced into something
• The force felt from gravity and acceleration are the same, this is the “principle of equivalence”
• Therefor, if you feel gravity’s influence you are accelerating; those in free fall are not accelerating, they don’t feel gravity
• Matter in space (planets, stars) warps gravity which changes the path of objects moving through space like a marble on a warped floor
• Einstein derived that gravity travels at exactly the speed of light, not instantaneously
• Gravity felt by us comes from all matter in the universe no matter how distant (unless it is so distant that the light of it hasn’t yet reached us)
• According to general relativity, even in an empty universe the water in the bucket (ch. 2) spins and moves outward so Mach was incorrect

(I apologize if some of these notes don’t appear to make sense, some are dependent on having read the book and being able to look at Brian Greene’s diagrams)

The Universe and the Bucket

• Galileo and others, meaning the concept predates Einstein, realized that velocity was relative; motion in a straight line is undetectable without some comparison but changes in velocity can be felt
• Newton conducted an experiment in which he spun a bucket of water; the water did not move at first but then started to spin causing the water surface to become concave, however when the bucket slowed and stopped the water still spun and retained the concave shape
• He explained the results using absolute space, the water is in motion compared to absolute space, however absolute space is unobservable
• Newton argued that the behavior of the water in the bucket was scientific proof of absolute space
• Ernst Mach, in the 1800s, wondered if the room which held the bucket, or the earth or the stars might be the other side in the waters relative motion instead of absolute space
• He argued that in completely empty space there is no difference between spinning and not; in other words, without a reference there is no such thing as spinning
• Mach argued that the force felt from spinning is proportional to the amount of matter in the universe (my thought: is this a way of saying it’s related to gravity?)
• My thought:  What about dark matter?  We can’t see it but it is matter so would we feel spin without a visual reference?

Roads to Reality

• Science shows us that our experiences are a misleading guide to reality
• Breakthroughs in physics force us to reevaluate our idea of space
• Developments in physics have shown space and time to be the most important and incomprehensible features of reality, this book investigates space and time
• Newton developed what is known as classical physics; described space and time as unchangeable and a structure (framework) for the universe
• Einstein, with the theory of relativity, proved Newton wrong; he showed space and time are “flexible and dynamic”
• However, classical physics is still useful as relativity is only detectable in the extremes of speed and gravity
• Classical physics and relativity say that if you know the velocity and position of any object you can determine its position and velocity at any other time past or future; quantum mechanics, however, states the best that can be done is to predict a probability of position and velocity
• Quantum mechanics describe a reality in which things are partly one way and partly another
• It also implies that something done here can be instantaneously linked to something there no matter how far away
• We perceive time as a one way arrow but known laws of physics don’t show this, so how can it be?
• The answer may be that the universe’s initial ordered state at its inception imposed this direction on time
• Unfortunately we don’t know the state of the universe at the beginning because relativity and quantum mechanics clash at that scale
• Einstein sought a theory that would explain everything in the universe, this is called unified theory
• This could be superstring theory which indicates that particles like electrons and quarks are actually strings and depending on how a string vibrates it might be a quark or an electron
• To unify theories superstring theory demands 10 or 11 dimensions of spacetime
• These extra dimensions beyond the four (3 directional and 1 time) we know could be either too small or too large to see