Lecture 36

Question 1

What are the 6 common elements of life?

Answer 1

• order
• reproduction
• growth and development
• energy utilisation
• response to environment
• evolutionary adaptation

Question 2

What are the 3 key ingredients for life?

Answer 2

• source of nutrients
• energy gradient
• liquid water

Question 3

What is the Copernican Principle?

Answer 3

• we are not in the centre of the universe
• the universe appears more or less the same everywhere
• the laws of physics work the same everywhere
• we do not appear special in any way

Question 4

What is the fine-tuning problem?

Answer 4

Our universe appears to be precisely optimised for complex life

Question 5

What are the six numbers which govern physics and the universe?

Answer 5

• N = relative strength of gravity ≈10^-39x strength of EM force
• ε = ratio of neutron/proton mass = 1.001378419
• ΩM = matter density = 0.3
• ΩDE = dark energy density = 0.7
• Q = strength of primordial density fluctuations ≈10^-5
• D = number and type of space-time
  dimensions = 3 space, 1 time

Question 6

What would happen if we changed the relative strength of gravity?

Answer 6

• stronger gravity- collapse would be too fast for life to evolve
• weaker gravity- stars cannot form

Question 7

What would happen if we changed neutron/proton mass ratio?

Answer 7

• heavier neutrons- they would decay into protons too fast and there would be no helium
• heavier protons- p-p fusion wouldn’t produce energy and there would be no stars

Question 8

What would happen if we changed the Ω densities?

Answer 8

• too much matter- the universe would collapse to quickly
• too little matter (or too much dark energy)- the universe would expand too fast for stars and galaxies to form

Question 9

What would happen if we changed the strength of primordial density contrast?

Answer 9

• Q too small- galaxies would take too long to form
• Q too large- everything would collapse into black holes

Question 10

What would happen if we changed the number and types of dimensions?

Answer 10

• fewer dimensions= chemistry is very limited and too simple for life
• more dimensions- unpredictable physics
• multiple time dimensions- no idea

Question 11

What is the strong anthropic principle?

Answer 11

The universe was designed with intelligent life in mind and sentient life is the purpose of the universe

Question 12

What is the weak anthropic principle?

Answer 12

Our universe is a selection bias and no matter how unlikely it may be, the only universe we can inhabit is one suited to intelligent life

Question 13

What is the unique universe theory?

Answer 13

A deeper theory of everything will explain what seems to be arbitrary now and why universe is the way it is

Question 14

What is the self-explaining universe theory?

Answer 14

Universes can only exist when observed (causal loop, Participatory Anthropic Principle)

Question 15

What is the fake universe theory?

Answer 15

The universe is a simulation in a
computer somewhere

Question 16

What is the multiverse theory?

Answer 16

As the universe came from such a small piece of space, other places could have inflated differently. Our observable universe is one of the bubbles and other regions (bubbles) may have different laws of physics

Question 17

What is the quantum worlds theory?

Answer 17

The universe branches at every change and every possible universe exists simultaneously. For every real world there are many other possible realities. Overlapping realities do not overlap or communicate.

Question 18

What is Occam’s Razor?

Answer 18

In choosing between two equally supported theories, chose the simpler of the two