From Quarks to the Cosmos

Lecture II – From Galileo to Newton

The Renaissance“What if the Sun be Center to the World, and

other StarsBy his attractive vertue and thir ownIncited, dance about him various rounds?In six thou seest, and what if sev’nth to theseThe Planet Earth, so stedfast though she seem,Insensibly three different Motions move?”

John Milton – Paradise Lost, VIII, 122-130

The Renaissance A literal rebirth of knowledge in all areas – art,

literature, AND science! Led by the “virtuosi”, a segment of society

that were patrons of the arts (and sciences) Educated and influential Paid for printing of manuscripts Highly interested in scientific and medical matters Departure from the traditional support of science

by kings/queens/monarchies.

Galileo Galilei Born in Pisa in 1564 (same year as

Shakespeare) Moved to Florence in the 1570’s Went to University of Pisa to study

medicine – ended up studying the pendulum … later developed a pendulum clock

Questioned the Aristotlean view that heavier objects fell faster than lighter objects … hail storms and inclined planes!

Eventually, he was appointed professor at the University of Padua

Galileo Galilei Developed one of the earliest

telescopes, based on earlier European designs (20x magnification)

Studied: The Moon* Satellites of Jupiter** Supernova*** Phases of Venus*** Sunspots***

Helped to verify the Copernican heliocentric model – the way things WERE, not just the mathematical model!!!

Galileo’s Writings He had to be creative (esp. when writing about

things that went against the RC church doctrine) “Dialogues Concerning the Two Chief World

Systems” (1624) Three characters – Salviati, Sagredo, and

Simplicio Arguments were presented by Salviati and

Simplicio, with Sagredo as the arbiter Pope Urban VIII had told Galileo that he could

write about Copernican theory, so long as it was presented as a mathematical model

Salviati = Galileo, Pope = Simplicio

Dialogues

Galileo’s Trial In 1633, he was called to

Rome to face the Inquisition Convicted of heresy, and

sentenced to house arrest for the remainder of his life

This was a pretty good outcome – see Giordano Bruno!

Died in 1642 in Florence (at the age of 78!)

Giordano Bruno Italian Dominican Friar, philosopher,

mathematician, astronomer Extended Copernican theory to

include that: The sun really WAS the center of the

solar system The sun was actually a star! The universe contained an infinite

number of worlds that were populated by other intelligent beings

Found guilty of heresy in 1600 by the Inquisition, and was burned alive at the stake … not a good way to go

Galileo’s Trial In 1633, he was called to

Rome to face the Inquisition Convicted of heresy, and

sentenced to house arrest for the remainder of his life

This was a pretty good outcome – see Giordano Bruno!

Died in 1642 in Florence (at the age of 78!)

Rene Descartes (1596 – 1650) Mathematician, philosopher, physicist “Cogito ergo sum”

He is incredibly important, because he put for the notions that: There is a universal mathematics … algebra There is a universal method … the differential

equation

Mathematics is, quite literally, the language of physics, and thus our models of the appearance of reality are mathematical models

Isaac Newton (1642-1727) Born in the country, on a farm – his

father died three months before his birth His mother remarried when he was three,

and he lived with his grandmother until he was twelve

She pulled him out of school to work on the farm … fortunately, he was horrible at it!

Went to Cambridge in 1661 … work-study program!

This was at the height of the debate between Aristotlean vs. more modern theories of science

In 1665 … Cambridge closes down.

Isaac Newton (1642-1727) He returned to the country, and

continued private study Invented calculus (or at least the

idea) Developed a theory of light and color Developed a theory that would form

the basis for the laws of planetary motion

He returned to Cambridge in 1667, earned his Master’s degree, and then eventually “inherited” a professorship at Cambridge

Isaac Newton (1642-1727) Over his career, Newton engaged

in many nasty correspondences with Robert Hooke … most notably on the laws that would describe planetary motion

He used his position as head of the Royal Society to discredit Hooke

In the end, though, he used some of Hooke’s ideas in formulating his own laws

Isaac Newton (1642-1727) In 1678, he suffered a nervous

breakdown Went into seclusion, and began

work (under the advice of Edmund Halley) on his greatest treatise …

Finally, in 1687, he published Philosophiae Naturalis Principia Mathematica (The Mathematical Principles of Natural Philosophy)

This contained, among many other things, Newton’s Laws of Motion

Newton’s Laws of Motion (I) Without an external force acting upon it, an object will

remain at rest, or will continue to move with constant speed (II) The speed of an object will change in proportion to the

amount of external force acting upon it (III) For every action, there is an equal and opposite reaction

In addition, he formulated a law of gravity (inverse square law), and together with the above three laws, he could explain the motion of the moon, the planets, as well as objects on earth

“The force of gravity keeps the universe balanced, makes it work, and brings heaven and earth together in one great equation.”

Newton - Epilogue His fights with Hooke continued, and escalated He suffered another nervous breakdown in 1693 He continued to use his positions in government

and in the Royal Society to attack others, including Leibniz (over calculus)

He never married He spent his later years writing about religious

issues (occult) … in fact, he wrote more pages on this topic than any other

“If I have seen farther than others, it is because I have stood upon the shoulders of giants.”

How to create a Universe (abridged) (i) create a space

for it

(ii) put stuff in it

(iii) let it heat up

(iv) let it evolve

LENGTH – metres, feet, miles, furlongs

MASS – kilograms, pounds, stones

TEMPERATURE – Fahrenheit, Celsius, Kelvin

TIME – seconds, minutes, hours, eons

Measuring things … We want to collect data about the universe …

what kind of data can we collect? Masses of things (kg) How far things move (m) How hot things are (K) How fast things move (m/s) How dense things are (kg/m3) How much energy something has … whoa …

wait a minute … what’s energy?

Energy A very ephemeral concept … not easy to define … we

need a definition: Imagine an object moving with some speed. Now, imagine that object smashing into a stationary object. The faster the first object is moving, and the heavier it is,

the more ability is has to “move” the second object. Energy, to a physicist is the measure of the ability to

make an object move through some distance … we call this WORK.

We do work by applying a FORCE to an object and making it move through a DISTANCE.

In the example above, we call this type of energy KINETIC ENERGY … energy of motion.

Forms of Energy Kinetic Energy … motion

Gravitational Energy … how much work gravity can do

Thermal Energy … how much work we could do by using the heat contained in an object … associated with vibrational motion of electrons around the atom, and in molecules.

Atomic Energy … the energy associated with electrons moving around the nucleus of the atom

Nuclear Energy … the energy associated with the binding of protons and neutrons together in the nucleus

Almost everything that goes on in the universe has to do with converting one form of energy to another!!!

Big Bang Theory No, not the show.

The version of creating a universe that we described before was really not too far off from what we think happened!

In the beginning … there was mass, and it had a LOT of kinetic energy

The mass was in the form of electrons, protons, neutrons, and not much else … how did we get from then to now?

And God said, “Let there be light.” … hey, what’s light?

Light There has been a LOT of debate about this

over the centuries!!!! The answer, currently, is that we don’t really

know. We do know that it is PURE energy. We also know that visible light is just one

“flavor” of this type of energy, which we call electromagnetic energy

Radio, television, x-rays, UV rays, infrared, microwaves are all flavors of EM energy

How did all these get created, when we only started out with matter and kinetic energy?

Mass energy So, there was this guy named Albert Einstein

…

He said that it was possible to convert mass into pure (EM) energy, and vice versa … pretty cool idea!

He also wrote down this equation that tells us how much energy we can get out of a particular amount of mass

So, is that where all the light came from? Uhmmm … no.

Binding Energy When things are assembled together nicely, they have LESS

energy than when they are separated. This energy difference is called binding energy

In other words, to tear apart a hydrogen atom (a proton and an electron), you have to put energy in to do it … that makes sense.

Conversely, when you let an electron and a proton come together and FORM a hydrogen atom, you get some energy out … how much, I wonder?

Well, it is a really tiny amount … imagine a Big Mac. Now, imagine a sesame seed on the bun of a Big Mac. Now, imagine diving the sesame seed a trillion times. Then, take one of those pieces, and divide that a trillion times. Think about the number of calories in one of those pieces … that’s what we’re talking about.

The Big Cool Down Eventually, after the Big Bang, the universe cooled

down, and electrons and protons started to “combine” into hydrogen atoms. When this happened, they released these little bursts of EM energy … where did it go?

Well, it’s still there!

After 14 Billion years, that EM energy is now in the form of microwaves that we can see EVERYWHERE in the universe!!! It’s called the Cosmic Microwave Background, and is our best evidence that the Big Bang really happened!

Images from Satellites