Natural Science 120

Prof. Andrew Reynolds

CC219

Where are we in the universe?

Aristotle (384-322 BCE)

Copernicus (1473-1543)

Kepler (1571-1630) Galileo (1564-1642)

Newton (1642-1727)

Einstein (1879-1955)

Edwin Hubble

• Red-shifting of galaxies implies they are moving away and universe expanding

• Implies in past universe was much, much smaller (sub-atomically small)

• ‘The Big Bang’

The Big Bang

The Big Bang

• Creation of Space and Time• What caused it?1. A Supernatural Intelligence? (God)2. A random fluctuation in the quantum

vacuum?3. Question a non-starter: causes

presuppose existence of space-time; ‘creation’ of space-time could have no cause in the standard sense

Fine-Tuning Argument

• Physical constants (mass of electron, strength of nuclear forces etc.) seem to be ‘perfectly’ tuned so to permit the formation of life in the universe. Why?

• Coincidence or not?

• Chance or sign of intelligence/purpose?

Anthropic Principle• Two Forms:• Q1: “Why do we find the constants set such that we are possible?”• D’uh! If they weren’t set such as to allow for intelligent life we

wouldn’t be here to ask the question. (Like a million dollar lottery ticket holder asking ‘why am I, a millionaire, in possession of this winning ticket?’)

• Q2: “Why are the constants, of all the possible values they could have taken, set at those values which permit (intelligent) life?” (Like anyone asking “Why did I win the lottery?”)

• Maybe because God set them that way; • or maybe it’s just luck/chance; (“But isn’t that just too improbable?”)• Maybe there are many universes in which the constants do take

different values, and of course we occupy one of those universes that are suitable for life (Multiple Universes hypothesis)

The conditions on earth and in the solar system are just so perfectly arranged that it can’t possibly be an accident that there is life here; there must have been some intelligence behind it.

Is it so surprising we find life in the place that is most suited to it?

But why is there life at all?

Design? Or inevitable result of the laws of chemistry and physics?

Finding Our Place in the Universe

Where are we?

Old Answer:

At the center of the universe

New Answer:

We don’t know where we are in any absolute sense; only in a relative sense – relative to other bodies (planets, stars, galaxies) and ‘here’ is no place special

• Only makes sense to ask where we are in an absolute sense (where are we really) if the universe has boundaries – and that we do not know

• We do know much better how to describe motion accurately

• And we can use this theoretical knowledge to do things – i.e. technology has vastly improved (space travel to other planets, satellites, GPS)

Here are some sample exam questions to help you study.1. Describe Newton’s Law of Universal Gravitation.

2. Describe some of the evidence that supports Newton's version of the heliocentric model of theuniverse.

3. What does it mean to say that Newton provided us with a "space-ship physics"?

4. Why did physicists propose that there was such a thing as the "luminferous ether"?

5. What is 'special' about Einstein's Special Theory of Relativity?

6. Describe Einstein’s Special Theory of Relativity.

7.Why is it that time slows down for systems moving at near the speed of light. (Use the lightclock example.)

8. Explain Einstein’s principle of the equivalence between gravitation and acceleration.

9.What surprising prediction did Einstein draw from the equivalence of acceleration of a frame ofreference and gravitation? Why was it surprising?

10. How did Einstein account for the equivalence of inertial and gravitational mass? How is thisrelated to his account of gravity?

11. What kind of response can we give to the question “Where are we in the universe?”

Prof. Andrew Reynolds History and Philosophy of

Science

Second term

In what relation do humans stand (according to modern science) in

relation to other forms of life?

Are we superior? Are we the ‘most highly evolved’?

HMS Beagle 1831-36

Darwin 1809-1882

Cell theory and

Developmental biology

SuperOrganisms