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The key to some of the The key to some of the fundamental questions about fundamental questions about

our Universeour UniverseSince the dawn of cilvalisation, many Since the dawn of cilvalisation, many

philosophers have asked questions about the philosophers have asked questions about the fundamental nature and intrinsic properties of fundamental nature and intrinsic properties of our Universe. This talk will explain, in layman our Universe. This talk will explain, in layman

terms, how the work of physicists sine the past terms, how the work of physicists sine the past millennium have unveiled the keys to answers to millennium have unveiled the keys to answers to

some of the these questions.some of the these questions.

By Yoon Tiem Leong, 19 June 2005 at Penang Caring Society Complex

First public talk in the public lecture series jointly organised by School of Physics, USM and PACE, in conjunction with the World Year of Physics

2005

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Plan of the talkPlan of the talk

• General description of the Universe• The general features of Science• The two important branch of physics theory

governing our Universe• Questioning the nature of matter and the

Universe:– What are matter made of?– Is the Universe finite in space? – Does the Universe has a beginning or does it existed

since infinite in time?– If it has a beginning, how and why did it get created? – Is our Universe unique?

• Conclusions

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General description of the General description of the UniverseUniverse

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Hierarchy of sizes of thingsHierarchy of sizes of things• Covering sizes from 10-19 m – 1036 m• Scientific equipment extend the limit beyond our

naked eye far beyond those ancient Greeks

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A plethora of diversified physical A plethora of diversified physical phenomenaphenomena

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Definition of UniverseDefinition of Universe

• Everything is inside the Universe

• Equivalently: nothing can exist outside the Universe

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Two aspects of the UniverseTwo aspects of the Universe• Physical – space, time, matter, energy and

interactions• Non-physical –Consciousness, spirituality

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Hence science is not Hence science is not omniscientomniscient

• Restricted to only the physical aspect of the Universe

• It is not supposed to be able to answer questions outside its scope

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The general features of The general features of PhysicsPhysics

• Physics only treats physical phenomena that are physically accessible in the Physical Universe

• Simply means phenomena that are measurable

• All physical phenomena are assumed to be governed by some fundamental laws which are formulated in terms of physics theory or theorems

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Fundamental Physical laws are Fundamental Physical laws are UNIVERSALUNIVERSAL

• Invariant (unchanged) in time and space

• Valid to all observers• Repeatable

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Features of Physics theoriesFeatures of Physics theories

• Constructed by human mind to describe the fundamental physical laws

• Physics theory must be testable, and be tested by experiments to check for validity

• Logically self-consistent and preserve causality • Use mathematics as a tool• Precise and not ambiguous• Must be FALSIFIABLE (at least in principle)• It is approximate truth • Has a range of validity

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Comparison with philosophy and Comparison with philosophy and ancient scienceancient science

• philosophy is highly contemplative, thinking-intensive, intuitive

• not empirical (bad for ancient science)

• “bath tub science”• Tell us why but not how • Science tell us how but not why

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Two fundamental theories that Two fundamental theories that governs the Physical Universegoverns the Physical Universe

• Quantum mechanics (microscopic world)

• General theory of relativity (cosmological world)– Classical Physics (the ordinary world) are

special cases of QM and GR

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GR and QM are two mutually GR and QM are two mutually exclusive theoriesexclusive theories

• Irony: They can’t be reconciled with each other into a quantum theory of gravity

• All right at most scenarios because quantum effects and GR effects don’t usually arise simultaneously

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Planck scale physicsPlanck scale physics• Planck scale = 10-34 cm or

10-44 s or smaller• Planck scale is the limit of

validity of known physics• Happen during first creation

of Universe and in Black Hole

• Both quantum and GR effect arises in these scenarios

• need quantum gravity which still not found

• All known physics temporarily breakdown

• Relevant to answer how Universe is created

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The Grand Play in the physical The Grand Play in the physical UniverseUniverse

• Our Universe is an existence that is made up of:

• Space• matter and energy

interact according to a set of physical laws

• time is running at the background

• Witnessed by conscious observers

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Simile of the stage performance Simile of the stage performance

• Actors = matters and energies • Music = flow of time• The stage = space• Languages spoken= fundamental

interactions• Plot of story line = universal

physical laws• Audience = conscious observers

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Fundamental questionsFundamental questions• Is matter made of fundamental

building blocks?• Democritus’s atom• Modern days’ atom• We have understood very well what are

matter made using scientific methodology• atoms = nucleus + electrons• nucleus is a composite of nucleons• Two types of nucleons: proton and

neutron(~10-15 m)• neutron is electrically neutral • proton is positively charged

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Constituent of matterConstituent of matter

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QuarksQuarks• protons and neutron are

made of ‘quarks’• 6 types of quarks: ‘up’,

‘down’, ‘charm’, ‘strange’, ‘down’, ‘bottom’

• Two types of “flavour” (+1/2,-1/2)

• Three family• Quarks don’t exist as free

particles• Proton and neutron are

made of uud and ddu• Each flavour comes in three

colours

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Mesons and hadronsMesons and hadrons• ‘hadron’ are particles made

up of three quarks

• Mesons are particles made up by quark + anti quark

• Most hadrons and meson are rapidly decaying into neutron, proton, electrons

• Hadron + meson = baryon

• Neutron and proton are the most common Baryons that forms the nucleus in matter

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Charged leptonsCharged leptons

• Another class of elementary particles distinct from quarks

• Also three family• Electron • Muon (106 times heavier)• Tauon (1784 times heavier)• Heavy cousins to electron• Muon and tauon are rare

and decay rapidly

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• Neutron, proton, electrons are familiar

• Other baryons and heavy charged leptons are far less common in our daily life because they are unstable and decays rapidly into the above familiar light particles

• Created by cosmic rays and particle accelerators

Most elementary particles are rare Most elementary particles are rare from daily experiencefrom daily experience

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• neutrinos• Little cousins to charged leptons• Come in three familes: electron-

type, muon-type, tauo-type neutrino

• “ghost particle”• Neutral in electric charge• Almost massless• Extremely inert• ~1012 passing through you every

seconds, unaware• Leptons also have the +1/2, -1/2

‘flavour’ as the quarks• Flavour ½ = charged leptons• Flavour -1/2 = neutral leptons

Neutral leptonsNeutral leptons

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Matter particleMatter particle

• Matter particle = leptons + quarks

• Quarks made up mesons (q+anti q) and baryons (3q)

• Leptons = charged (e, mu, tau) + neutral (neutrinos)

• Matter particles have spin ½

• They are ‘fermions’

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• 4 fundamental types• Strong force (among

coloured quarks) - gluons• Electromagnetic force

(among charged particle) - photons

• Weak force – among flavoured particles – Z, W+, W-

• Gravity – among all types of particles – graviton

• They are boson, with integral or 0 spin

Interactions among the matter Interactions among the matter particlesparticles

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Unification of forcesUnification of forces• Interactions are similar to

‘languages’ spoken in the stage play

• Disparate interactions are thought to be low energy manifestation of a unified force higher up

• EM + weak = electroweak force (accepted, Standard Model)

• Electroweak + strong = Grand Unified Theory, GUT (in the making, not experimentally confirmed)

• GUT + gravity = TOE (theory of everything) (???)

• Thought to have occurred during the early Universe when temperature is extremely hot

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Questions on the cosmos:Questions on the cosmos:

• Is the Universe finite in space?

• Does the Universe has a beginning or does it exist since the infinite past?

• If it has a beginning, how and why did it get created…

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Olbers paradoxOlbers paradox

• Olbers, German astronomer, 1826

• Paradox regarding ‘night sky is dark’

• Night sky should be as bright as the surface of the sun according to calculation!!!

• What went wrong in the calculation?

• Have wrongly assumed stars (galaxies) are static in the Universe

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The Universe is expanding !!!The Universe is expanding !!!• 1929 detected by Edwin

Hubble • Predicted by GR• Measured value of

Hubble constant tell us the receding speed of galaxy, age and size of universe using GR

• Age = 13.7 billion years old

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The Universe …The Universe …

• is finite is size • Is finite in age• does not exist since

forever• does not maintain a

state of eternality• It necessarily evolves

with time

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Hot Big Bang Hot Big Bang

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Rewinding UniverseRewinding Universe

• We can trace the evolutionary history of the Universe using physical laws

• Can trace the history as early as we can, until the logical links break down at the First Moment of creation

• Good thing: Can check predictions against observations

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Primordial plasmaPrimordial plasma

• Universe today is vast in space, cool and no collisions between particles

• But as Universe goes back in time further, temperature rises to millions and trillions of degrees

• All matter would melt down into the elementary particles, mixed with forces particles in hot soup called plasma

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Particle physics and evolution of Particle physics and evolution of the Universethe Universe

• Particle physics meets cosmology in the early universe

• Interplay between the elementary particles physics with cosmology directly affect the later evolution of the Universe (including our FATE)

• Many predictions can be made

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CMBR: hard core evidence to big CMBR: hard core evidence to big bang, produced at age 300,000, bang, produced at age 300,000,

3000 K3000 K

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Other confirmation: BBNOther confirmation: BBN

• Big bang nucleosynthesis• tells us how Helium, deuterium

etc. are formed from the primordial ingredient neutron and proton around 1 - 3 mins

• Predicts the abundance of He in present in our Universe

• has been measured to be just the right amount as predicted

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Is our Universe unique?Is our Universe unique?

• Steps to create a universe?• Prepared spacetime by whatever means• prepare laws of physics • prepare initial conditions in terms of natural constants• prepare ‘boundary condition’ of ‘there is nothing outside the Universe’• supply the ingredient matter and energy• then says, “let’s rock’

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Does GOD has any choice?Does GOD has any choice?• Evolve a universe is easy• But not so if want to evolve one

with a conscious mind to ask the question about the Universe

• Required extreme fine tuning and consistency of physical laws

• Einstein asked: 'How much choice did God havein constructing the universe?’

• Maybe He don’t given the extremely tight constraint

• Anthropic principle?• Since we can’t ever access ‘the

other universe’ physically we can’t tell scientifically if we are unique

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What caused big bang?What caused big bang?

• Need to understand quantum gravity and Planckian physics to answer this question

• Don’t know what’s the answer at the moment (from physics point of view)

?

??

?

?

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ConclusionConclusion• Questions asked by

philosophers are now being provided by physics

• Amazing! Successful application of physical laws across so many orders of magnitude in physical scales to understand the Universe

• Still many fundamental questions unanswered due to ignorance of the Planck’s domain

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Will we finally knows everything Will we finally knows everything and understand our Universe with and understand our Universe with

physics?physics?• A lost traveler moving

in a seemingly endless desert, could he ever know whether he will reach an oasis at the end of the horizon, or will he just find another endless piece of desert land?

• We don’t know, but still, we keep walking.