13.7 Billion Years – the summary, Exercises of Particle Physics

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13.7 Billion Years – the summary

what have we learned about the natural universe, and why do we trust it

Gordy Kane

Michigan Center for Theoretical Physics

“ Dare to Know” Immanuel Kant, 1789

ONE IMAGE FOR 13.7 BY?

•^

When Shakespeare wrote,

nothing

was

understood about how the natural world works

-^

Many conjectures and ideas – but no way todecide what was right

-^

Then modern science – both a way, a method,to try to understand the natural world, and

the cumulative results

•^

Today we have, or are

addressing scientifically

essentially a complete comprehension of thenatural universe and all that is in it!!

So talk covers

both

¾

A little more about how science works… o^

Science is a human activity -- examine natural world, guess explanationfor how something works, or why, figure out some consequences ifindeed it works that way, test with observations and measurements,repeat until get it right

--observations fine, always relics (don’t have to be at the Big Bangor origin of life or see evolution to test it)

o^

Every development in science has to be consistent with all we havelearned, all established theories

-- e.g. age of universe, sun, earth must be old enough for evolution

to have occurred

o^

What is a “theory”?

-- basically a big idea that explains several or lots of observations

and questions (Big Bang theory, quantum theory, theory ofevolution, …) – never “just a theory” – has passed many tests –may still be undergoing tests, but accepted by mostrelevant scientists

NO BELIEFS, NOTHING EVER PROVED – but science has built up a

great body of knowledge and understanding about the world

“Effective theories”

(name from “effectively you can …”)(based on building blocks known not to be elementary but can

be treated as if they were)

o^

If we had to understand whole physical universe tounderstand any part, would never have made progress o^

Astronomers or geneticists don’t need to know about quarks o^

Suppose properties of an atom depended on its history, or onwhether it were in a person or a rock – wouldn’t understand them yet

(that’s why physics is the easiest science)

o^

Particle physics deduces, explains proton and its properties (fromquarks and their properties) – but proton is input into nuclearphysics, astrophysics, chemistry o^

Once we understand the individual effective theories, we can unify –today unification far along

-- Darwin and his ideas unified living and non-living, human and

non-human, physical and mental -- Probably only one force in nature, not four – only a few

particles

Elementaryconstituentsof matter

universe

consciousness

galaxiessolar systems

hominids

planets

mammals

moleculesatomsnuclei

life

protons

cells

electronsquarks“Standard Model” theory of particle physicsSupersymmetry theory?String theory?

universe

consciousness

galaxiessolar systems

hominids

planets

mammals

moleculesatomsnuclei

life

protons

cells

electronsquarks“Standard Model” theory of particle physicsSupersymmetry theory?String theory?

WHAT HAVE WE LEARNED ABOUT THE

NATURAL UNIVERSE?

…and every educated person should know… (there is very good evidence for the whole list…not metaphors,

quantitative theories…)

The universe is governed by a few (or maybeeven one) irreducible universal natural laws thatdescribe all there is and all that happens in thenatural world – people can discover andunderstand them (it)

All we see in the universe

is

made of just three

fundamental particles (electrons, up quarks,down quarks), interacting via a few forces

(quarks combine to make protons and neutrons, which

combine to make nuclei, nuclei and electrons to make atoms, atomsbind to molecules, which combine to make organisms… nuclei makeplanets and stars…)

The quarks and electrons in us are essentiallyall from the Big Bang, and many have been inevery person who ever lived

The earth’s history – oceans, atmosphere,continents, etc, the transition from chemicals toorganisms -- is being understood

¾

Much is known and being learned about conditions whenlife began – much is known and being learned about theresulting cells – have a few plausible scenarios wherecan see how each step could have occurred – one actualmechanism may become convincing

conditions

Resulting

cells