The Anthropic Cosmological Principle: A Universe made for me?

Geraint F. LewisSydney Institute for Astronomy

The University of Sydney

What is the “Anthropic Principle”?

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The Geocentric Universe

Nicolaus Copernicus(1473-1543)

The Heliocentric Universe

Galileo Galilei(1564-1642)

The Heliocentric Universe

Brahe & Kepler(1546-1601/1571-1630)

Isaac Newton(1643-1727)

The Clockwork Universe

William Herschel(1738-1822)

The Milky Way of Stars

The Milky Way of Stars

Hub

ble

Ultr

a-D

eep

Fiel

d

The Immense Universe

The Copernican Principle

The Copernican Principle says that we are not in a privileged location, in either space or time, and this should hold at all points in the Universe.

The Relativistic Universe

Albert Einstein(1879-1955)

The Dispassionate Universe

Or is it?

Robert Dicke(1916-1997)

From the first stars…

… to the last.

We could not live in the first few billion years of our universe, and could not arise after a few trillion years.

Curiouser and curiouser…..

The expansion of our universe depends upon the mix of “stuff” in it, such as matter, radiation and dark energy. If we imagine different universes with different mixes, some will collapse quite quickly, some will expand quite quickly.

Space

Tim

e

The Goldilocks Universe

So, our Universe appears to be a Goldilocks universe.

It has the right mix of stuff, not too much to recollapse, not to little to expand too fast. How lucky we are to find ourselves in this universe nicely “designed” for us.

Whoa!! Hold your Horses

“It’s rather is if you imagine a puddle, waking up one morning and thinking hmm this is an interesting world I find myself in, an interesting hole I find myself in, it fits me rather neatly, doesn’t it. In fact it fits me staggeringly well, must have been made to have me in it!

This is such a powerful idea that as the sun rises in the sky and the air heats up and, as gradually the puddle gets smaller and smaller it’s still frantically hanging onto the notion that everything’s going to be alright because this world was meant to have him in it, was built to have him in it. So the moment he disappears catches him rather by surprise.”

Douglas Adams

Do we live on a Goldilocks Earth? A planet apparently made for human life?

Curiouser and curiouser…..

At 1ns, the Universe had a density of a medium-sized asteroid per cubic centimetre. One gram more at the Universe would have collapsed before 10 billion years and we would not be here to talk about it.

Space

Tim

e

… and curiouser

In 1998, it was realised that the expansion of the Universe is accelerating, driven by a mysterious, dominant component known as Dark Energy

The Quantum Vacuum has the right kind of properties to be the source of Dark Energy. However, the theoretically expected value is

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

times larger than the observed value. Why the (ridiculously huge) difference?

… and curiouser

What if we played with the fundamental forces?: Gravitational ForceWeaker: Stars would not burn, or possibly even formStronger: Stars burn to quick, using up all of their fuel

http://www.particleadventure.org/

… and curiouser

What if we played with the fundamental forces?: Electro-Magnetic ForceWeaker: No atoms as electrons will not stick to nucleiStronger: Electrons strongly bound to atoms, allowing no molecules

http://www.particleadventure.org/

… and curiouser

What if we played with the fundamental forces?: Strong ForceWeaker: Nuclei would not exist, with only hydrogen in the UniverseStronger: Light elements would quickly join to make iron

http://www.particleadventure.org/

… and curiouser

What if we played with the fundamental forces?: Weak ForceWeaker: Reduced radioactivityStronger: Increased radioactivity, with everything becoming iron

http://www.particleadventure.org/

The Goldilocks Universe

If we randomly choose the mix of stuff and the forces of nature, the most likely universe we will end up with will be sterile.

But our Universe, of course, has not only the right mix of stuff, but also it has the right combination of fundamental forces, none too strong or too weak, allowing stars, elements, molecules and us to form.

The question is why?

The Anthropic Principle

In 1973, Brandon Carter articulated these ideas in the Anthropic Principle. This has two components;

Weak Principle: The fact that we, carbon-based life, are here, tells that that, while not central, we must have some privileged view of the Universe.

Strong Principle: The fact that we, carbon-based life, are here, tells us that the fundamental properties are such to allow complex, intelligent life to develop.

However, the question remains why?

Brandon Carter(1942-)

Is this getting us anywhere?

The only successful use of Anthropic Reasoning came from Fred Hoyle. As one of the first to realise the inner workings of stars, he also realised that that there was a problem in the formation of Carbon (known as the Beryllium Bottleneck).

He reasoned that as we are here, and are made of Carbon, their nuclei must possess a, as yet unknown, “resonance” to allow the reaction to occur. This was searched for, and found, where Hoyle said it should be.

Option 1: Fine Tuned/Just the Way it is!

“I don’t pretend to understand the Universe, it’s a great deal bigger than I am”

Thomas Carlye (1795-1881)

A divine creator Or not?

Option 2: An Underlying Beauty?

Perhaps the dimensions of space and time, the forces of nature and the fundamental particles are linked and there is no underlying freedom in the Universe. Our current attempts of a Theory of Everything suggest that this is not the case.

Option 3: A Many-Worlds Universe

Many-worlds is an idea from quantum mechanics, with the idea that every time a “decision” is made, the universe splits into two universes, each with a different outcome of the choice. Most universes would become sterile, but we would find ourselves only in that small number of universes that preserve life.

Option 4: The Multi-verse

The early universe had a burst of expansion called inflation. With this, different patches of the universe have their initial properties “frozen-in”. This means that many patches of the Universe are sterile, but, of course, we should expect to find ourselves in a patch whose properties can support life.

The Superstring Landscape

The “cutting-edge” of physics has the goal of unifying general relativity and quantum mechanics.

One of the leading contenders, string theory, has a huge (infinite?) possible combination of physical parameters (and hence and huge number of possible universes).

But which is the combination in which we live in? Physicists are turning to the anthropic principle to narrow down the huge volume. Will this solve the issue?

The Controversial Anthropic Principle

Published in 1986, Barrow and Tipler’s book pushed the meaning of the Anthropic Principle;

Weak Principle: All properties of space and time must be consistent with the existence of carbon-based life (including the number of dimensions etc).

Strong Principle: A Universe with these properties (i.e. our Universe) must develop intelligent life at some point in its history.

The Objectors

Every time the anthropic principle is raised, arguments ensue, with the point that (other than Hoyle’s work) the anthropic principle has explained nothing. Does it really give us clues to the underlying nature of the Universe?

Anthropic Weirdness

Self-Reproducing Universe Final Anthropic Principle (FAP)

Anthropic Weirdness

Self-Reproducing Universe Final Anthropic Principle (FAP)

Com

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idicu

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Ant

hrop

ic Pr

incip

le (C

RAP)

So, where are we…

Lynette Cook

The anthropic principle is an interesting concept, confronting our basic ideas in understanding our place in the Universe.But does this tell us anything we didn’t know about the Universe, or allow us to deduce why our Universe is as it is; to some yes, to others, no.

In either case, we have not heard the end of the Anthropic Principle.

So, where are we…

Lynette Cook

The anthropic principle is an interesting concept, confronting our basic ideas in understanding our place in the Universe.But does this tell us anything we didn’t know about the Universe, or allow us to deduce why our Universe is as it is; to some yes, to others, no.

In either case, we have not hear the end of the Anthropic Principle.

The End

Particle Astronomy – the Second Window by Dr Marc Duldig, Australian Antarctic Division

14 October – 6.00pm

Bankwest Theatre (Building 200), Curtin University of Technology, Bentley

RSVP is essential. Please respond by Friday 9 October 2009 by phone: 08 9266 2563 or email: events@curtin.edu.au