# Modern ideas. A Brief History of Beginnings Non mythological beginnings, that is Non mythological beginnings, that is Georges Lemaître and his primordial.

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Modern ideas

A Brief History of Beginnings Non mythological beginnings, that is Non mythological beginnings, that is Georges Lemaître and his primordial atom Georges Lemaître and his primordial atom Vatican Astronomer Vatican Astronomer Alexander Friedman: Big Bang Alexander Friedman: Big Bang Russian Mathematician Russian Mathematician He didnt name the beginning The Big Bang He didnt name the beginning The Big Bang It wasnt remotely big and it didnt go BANG! It wasnt remotely big and it didnt go BANG! A pejorative term given by Sir Frederick Hoyle A pejorative term given by Sir Frederick Hoyle Einstein wasnt comfortable with either theory, although he did verify the correctness of Friedmans mathematics Einstein wasnt comfortable with either theory, although he did verify the correctness of Friedmans mathematics N.B. We will have to think in very, v-e-r-y short times scales here! N.B. We will have to think in very, v-e-r-y short times scales here!

The Evidence

Hubbles Law Edwin Hubble found that, the more distant the galaxy, the faster it was receding from us H o is the slope of this line Currently is thought to be ~ 73 H o is in units of km/sec/Mpc Ultimately units of time Gives us the age of the Universe! 13.75 +/- 0.12 Gyr

The Rationale: According to the Red Shift of distant galaxies, the Universe is expanding According to the Red Shift of distant galaxies, the Universe is expanding If the Universe is expanding, we can run the clock backwards and find the starting point (whatever that means) If the Universe is expanding, we can run the clock backwards and find the starting point (whatever that means) Important! Wrap your minds around this: Important! Wrap your minds around this: By the beginning we dont mean that all the matter and energy exploded into an existing space. By the beginning we dont mean that all the matter and energy exploded into an existing space. We mean that all matter, energy, SPACE and TIME all began at this singular point. We mean that all matter, energy, SPACE and TIME all began at this singular point.

Definitions Homogeneous The same everywhere at a certain scale Isotropic The same in every direction 123rf.com

String-Theory Stems from the transition from continuum Physics to quantum Physics at the turn of the 20 th C Stems from the transition from continuum Physics to quantum Physics at the turn of the 20 th C Starting in the 80s the notion arose that strings were a better model for the basic constituents of matter Starting in the 80s the notion arose that strings were a better model for the basic constituents of matter

Strings were on the Planck length scale Strings were on the Planck length scale 10 -35 m 10 -35 m Since we cant see detail at that scale, particles would naturally be the first approximation Since we cant see detail at that scale, particles would naturally be the first approximation First applied to describe strong interaction, but the theory generated gravitons, much to everyones surprise First applied to describe strong interaction, but the theory generated gravitons, much to everyones surprise And strings demanded 10 dimensions! And strings demanded 10 dimensions!

Feynman diagrams too convoluted to incorporate these extra dimensions Feynman diagrams too convoluted to incorporate these extra dimensions Branes are introduced to explain interactions Branes are introduced to explain interactions

Dimensions

M-Theory String theory required 9+1 dimensions String theory required 9+1 dimensions However, this produced 5 equally valid variations! Unacceptable! However, this produced 5 equally valid variations! Unacceptable! A lesser known theory, Supergravity, postulated 10+1 dimensions A lesser known theory, Supergravity, postulated 10+1 dimensions Merging the two ideas resolved the 5 variations Merging the two ideas resolved the 5 variations However, the addition of the 11 th dimension caused the strings to weave into Membranes However, the addition of the 11 th dimension caused the strings to weave into Membranes

Insane in the (mem)Brane A theory of the trigger A theory of the trigger Multidimensional Universe or multiverse Multidimensional Universe or multiverse Gravity is the weakest force because it stretches between branes and is diluted Gravity is the weakest force because it stretches between branes and is diluted Intersection of branes initiates a BB Intersection of branes initiates a BB So time didnt have to begin with the BB So time didnt have to begin with the BB

Other Dimensions Flatland, a Romance in Many Dimensions Edwin Abbott Abbott, 1885 A square and his wife in Flatland An introduction to greater dimensions

Lisa Randall Astrophysicist at Harvard Leading Brane proponent Warped Passages: Unraveling the Universe's Hidden Dimensions See also David Deutsch, Hugh Everett…

How the Universe Got Its Spots Jenna Levin and others propose a more topological description of cosmology than String Theory

An Aside About Theories… Theories like Newtons Law of Gravitation and Einsteins General Theory of Relativity are testable and have been verified many, many times Theories like Newtons Law of Gravitation and Einsteins General Theory of Relativity are testable and have been verified many, many times Inflation is not yet testable because the energies are too high to be currently reproduced in the laboratory Inflation is not yet testable because the energies are too high to be currently reproduced in the laboratory Furthermore, direct evidence supporting inflation is not visible because it happened long before the Universe was transparent Furthermore, direct evidence supporting inflation is not visible because it happened long before the Universe was transparent

Why Bother with Inflation? It accounts for certain observed phenomena: It accounts for certain observed phenomena: Flatness Flatness Horizons Horizons No monopoles No monopoles Not a deus ex machina Not a deus ex machina The Universe is currently inflating, after all The Universe is currently inflating, after all

Stelliferous Era From about 380,000 years A.B.B (after the Big Bang) until now From about 380,000 years A.B.B (after the Big Bang) until now Galaxies at about 1 billion A.B.B Galaxies at about 1 billion A.B.B Average temp = 3K Average temp = 3K The era of stars, galaxies, and us The era of stars, galaxies, and us What weve talked about most of the semester! What weve talked about most of the semester! Top down vs. bottom up Top down vs. bottom up Did massive clouds of gas form first, generating the stars (top down) or did stars form first, collecting into galaxies (bottom up)? Did massive clouds of gas form first, generating the stars (top down) or did stars form first, collecting into galaxies (bottom up)? Probably a combination Probably a combination Where gas was dense enough, stars formed first Where gas was dense enough, stars formed first Where gas was rarefied, dark galaxies formed, later yielding stars Where gas was rarefied, dark galaxies formed, later yielding stars Era will continue until the year 100 trillion A.B.B Era will continue until the year 100 trillion A.B.B Youngest object ever imaged @ 800MYr A.B.B Youngest object ever imaged @ 800MYr A.B.B

The First Stars

The Universe at 2 Gyr Old

Hubble Ultra Deep Field 1 million second exposure Red shifts allow for dating and therefore 3D imaging Looking back to 700 million years A.B.B. The last image shows a red galaxy, the earliest object ever imaged

Then, 40 Years Ago

Current Mix of Cosmological Stuff

Vacuum and/or Dark Energy Very low energy density Very low energy density If the whole Earth volume were V.E. it would be about 1 days worth of electricity for 1 person If the whole Earth volume were V.E. it would be about 1 days worth of electricity for 1 person The Quintessence ( ) is B-A-C-K! The Quintessence ( ) is B-A-C-K! If true, then constants evolve If true, then constants evolve

And here we are today… What will happen in the distant future?

Fate

Entropy vs Gravity (curvature) Entropy: a thermodynamic law dictating the inevitable march to disorder Entropy: a thermodynamic law dictating the inevitable march to disorder Simple disorder, like breaking glass Simple disorder, like breaking glass Thermodynamics disorder: concentrations of energy, as in a star Thermodynamics disorder: concentrations of energy, as in a star The arrow of time The arrow of time Gravity (curvature) pulls together (order), entropy corrupts (disorder) over time Gravity (curvature) pulls together (order), entropy corrupts (disorder) over time

Expansion The Universe continues to expand Expansion occurs partially due to, the cosmological constant Where matter is closely spaced, gravity (curvature) overwhelms Elsewhere wins And ultimately will win!

The Future: The most likely* outcome will be the open Universe The most likely* outcome will be the open Universe AKA The Big R.I.P. AKA The Big R.I.P. The actual density of the Universe is less than the critical density The actual density of the Universe is less than the critical density The Universe will expand forever The Universe will expand forever Three Foreseeable Epochs (after the Stelliferous Era): Three Foreseeable Epochs (after the Stelliferous Era): The Time of Degeneracy The Time of Degeneracy The Time of Black Holes The Time of Black Holes The Time of Photons The Time of Photons

But first… A way to get a handle on these massive time scales A way to get a handle on these massive time scales Remember from our first lectures, the idea of powers of 10? Remember from our first lectures, the idea of powers of 10? 10 1 = 10 10 1 = 10 10 2 = 100 10 2 = 100 10 3 = 1000, etc 10 3 = 1000, etc Lets define a cosmic decade, 10 t years Lets define a cosmic decade, 10 t years 10 1 years is the first cosmic decade, 10 2 is the second, and so on 10 1 years is the first cosmic decade, 10 2 is the second, and so on The decade is t The decade is t Like stairs where every next step is 10X the height of the last Like stairs where every next step is 10X the height of the last We are in the 10 th cosmic decade We are in the 10 th cosmic decade The Stelliferous Era will last to the 14 th cosmic decade The Stelliferous Era will last to the 14 th cosmic decade

The Time of Degeneracy Not about deplorable behavior: how matter behaves Not about deplorable behavior: how matter behaves From cosmic decade 14 to 37 From cosmic decade 14 to 37 How do we know? How do we know? From the mean half-life of a proton, 10 37 years From the mean half-life of a proton, 10 37 years Once in a while, two White Dwarfs may collide and produce a supernova Once in a while, two White Dwarfs may collide and produce a supernova If not, all WDs will shine away all their energy If not, all WDs will shine away all their energy The End of Structure The End of Structure

The Time of Black Holes Cosmic Decade 37 to 100 Cosmic Decade 37 to 100 How do we know? How do we know? Steven Hawking determine the rate of black hole evaporation, now know as Hawking radiation Steven Hawking determine the rate of black hole evaporation, now know as Hawking radiation Particle pair production near the event horizon Particle pair production near the event horizon Due to the stretching of space-time Due to the stretching of space-time One particle falls in, the other escapes One particle falls in, the other escapes Radiation follows blackbody curve Radiation follows blackbody curve Cooling time can be calculated Cooling time can be calculated

The Time of Photons Cosmic Decade 100 until ??? Cosmic Decade 100 until ??? Very long wavelength photons Very long wavelength photons Cold, dark Cold, dark Entropy wins Entropy wins Or does it? Or does it? Very difficult to make predictions 10 100 years in the future Very difficult to make predictions 10 100 years in the future Could be that new complexity begins Could be that new complexity begins From other branes From other branes Via processes we cant imagine Via processes we cant imagine

THANK YOU FOR YOUR INDULGENCE! But this will all happen after the final exam But this will all happen after the final exam

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