Seven Brief Lessons in Physics Flashcards
What is the 1st lesson?
Gravity acts through a field. That gravitational field is space itself. It is, in effect, space-time, and it can be curved due to mass.
What is the special theory of relativity?
Einstein’s first theory of relativity, that shows that time doesn’t pass equally for everyone
What is the general theory of relativity?
Gravitational field is space itself.
The laws of physics are always constant. The speed of light is always observed to be the same. The floor accelerating upwards feels the same as gravity pulling you down to the floor.
Who theorised that space must be expanding?
Einstein
When was space observed to be expanding?
1930
What is the 2nd lesson?
Quantum Mechanics
How does light exist?
In discrete patterns; photons
What is quantum mechanics?
Fundamental particles have a probability to exist in certain situations, when observed or interact
Why was Einstein bothered by this?
He thought there was no place in reality for randomness - that it should be lawlike
What is the 3rd lesson?
The model of the solar system; heliocentric
Who believed in the geocentric model?
Aristotle and Ptolemy
What was Ptolemy’s model?
Geocentric, with each planets also having epicycles
Who presented the heliocentric model?
Copernicus
What is the 4th lesson?
The Standard Model of Elementary Particles
What is the exchange particle holding together quarks inside nucleons?
Gluon (strong interaction)
What are the fundamental particles?
Electrons, quarks, photons, gluons, neutrinos
What are the problems of the Standard Model of Elementary Particles?
Criticised for being ambiguous, convoluted and unsystematic; there is no single unifying equation; deals with very large outputs that need to be ‘renormalised’; unsatisfyingly complex; did not predict dark matter
What is the 5th lesson?
How general relativity and quantum mechanics interact
What is the problem with general relativity and quantum mechanics?
They contradict each-other
On what scale does general relativity operate?
Universal
On what scale does quantum mechanics operate?
Subatomic particles
What is the endeavour to unify general relativity and quantum mechanics?
Loop quantum gravity
What does quantum mechanics claim about physical space?
It has a granular structure; it is made of quanta much like a field
How does loop quantum gravity describe the world?
As a series of interactions, rather than objects
What does loop quantum gravity say about time?
There is no time ‘in which’ events occur in. There may not be temporal order
Why are black holes an issue for loop quantum gravity?
There can be no infinitesimal points, only discrete units
How does loop quantum gravity explain black holes?
A sun in the last stages of its life collapses into an unstable Planck star, then rebounds
What question is raised by loop quantum gravity?
It is a ‘big bounce’, formed from a preceding universe that contracted under its own weight
What is the 6th lesson?
Thermodynamics; probability
What was the original theory explaining heat?
It was transferred in a fluid called caloric
Who first realised that heat relates to the movement of particles?
Maxwell and Boltzmann
What is the distinction between past and future?
The transfer of heat
Why does heat transfer from hot to cold?
Energy is conserved in each collision
What is the science of the probability of different motions?
Statistical physics
What is statistical physics?
The science of the probability of different motions
What is statistical physics called when referring to heat?
Thermodynamics
Why is thermodynamics probabilistic?
The qualities and quantities about an object that we observe do not give us enough information to exactly predict its thermodynamic future
What have thermodynamics and statistical physics been applied to?
Electromagnetic fields and quantum phenomena
What have we theorised about the application of thermodynamics to gravity?
Gravity is space-time. When it is heated, time/space should vibrate, but we cannot yet describe this. What is a vibrating time?
What does modern physics describe the world as a function of?
Time; because it ‘flows’ in a way space does not
What has been (somewhat counterintuitively) suggested about the past and future?
They exist, in the same way that things that are not ‘here’ exist
How is time similar to the geocentric model?
It is natural intuition
What is the 7th lesson?
Ourselves; what role do humans play?
What are the three obstacles to our perception of the world?
Our ignorance, our senses, our intelligence
What is information?
The connection that physics makes between the state of two things
What questions does Rovelli posit about human minds?
Is there free will? Does human consciousness transcend the regularity of nature; Einstein’s law-like world?
What conclusion does Rovelli come to about the mind?
‘Me’ and the physical interactions in my brain are one and the same
