The key to some of the fundamental questions about our Universe

1. The key to some of the fundamental questions about our Universe Since the dawn of cilvalisation, many philosophers have asked questions about the fundamental nature and intrinsic properties of our Universe. This talk will explain, in layman terms, how the work of physicists sine the past millennium have unveiled the keys to answers to 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

2. Plan 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

3. General description of the Universe

4. Hierarchy 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

5. A plethora of diversified physical phenomena

8. Definition of Universe • Everything is inside the Universe • Equivalently: nothing can exist outside the Universe

9. Two aspects of the Universe • Physical – space, time, matter, energy and interactions • Non-physical –Consciousness, spirituality

10. Hence science is not omniscient • Restricted to only the physical aspect of the Universe • It is not supposed to be able to answer questions outside its scope

11. The general features of Physics • 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

12. Fundamental Physical laws are UNIVERSAL • Invariant (unchanged) in time and space • Valid to all observers • Repeatable

13. Features 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

14. Comparison with philosophy and ancient 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

15. Two fundamental theories that governs 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

16. GR and QM are two mutually exclusive 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

17. Planck 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

18. The Grand Play in the physical Universe • 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

19. 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

20. Fundamental 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

21. Constituent of matter

22. Quarks • 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

23. Mesons 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

24. Charged 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

25. Most elementary particles are rare from daily experience • 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

26. Neutral leptons • 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

27. Matter 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’

28. Interactions among the matter particles • 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

29. Unification 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

30. 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…

31. Olbers 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

32. 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

33. 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

34. Hot Big Bang

35. Rewinding 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

36. Primordial 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

37. Particle physics and evolution of the 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

38. CMBR: hard core evidence to big bang, produced at age 300,000, 3000 K

39. Other 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

40. 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’

41. 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

42. 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) What caused big bang? ? ? ? ? ?

43. Conclusion • 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

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