Confused at a Higher Level

•  "Before I came here I was confused about this subject. Having listened to your lecture I am still confused. But on a higher level." - Enrico Fermi

Two clouds on horizon

Black body radiation Properties of

light

Black body radiation

Atoms

Paradox #1: Double-slit paradox

• How can you be in two places at once when you aren’t anywhere at all? - Firesign Theater

Double slit

Bullets and waves

Delayed choice

Quantum eraser

Delayed choice & quantum eraser

Six Blind Men & the Elephant

Shut up and

calculate

Collapse

Many worlds

Paradox #2: Infinite means zero

Quantum electrodynamics continuously tosses up quantities which are: 1) Infinite 2) Really small (but o*en measurable)

Lamb shi*

Renormalization

But tiny

Casimir effect, classical

Casimir effect, quantum

Infinite and tiny

•  ``It appears therefore that the theory as it stands now must be strangely near to the final solution, yet it cannot possibly be correct, as the mathematical procedure used to extract these results is plainly unacceptable.'' - Heitler

Paradox #3: how can time go both ways at one time?

Entropic time

•  Time measured by increasing entropy:

•  The direction bombs explode in, eggs cracks in, people age in, and the like.

•  Unfortunately, Schulman has shown that this can go both ways!

time

time

“Opposite thermodynamics arrows of time” L. S. Schulman

Acme Wormhole Construction Company

Visser’s recipe for a time machine:

1.  Acquire a traversable wormhole

2.  Induce a “time-shi*” between the two mouths of the wormhole

3.  Bring the wormhole mouths together

Davies’s How to Build a Time Machine

How do you go about constructing a traversable wormhole and turning it into a time machine?

Black Holes & Timewarps�- Kip S. Thorne

“Time’s Up for the Time Bandits”

•  Cover Story in New Scientist, 20th of September 2003

•  "Forget about coming back to murder your great-grandfather. It never happened, and there are forces out there making sure it never will."

"For better or for worse, most canonical quantum field theories are found by starting with a classical field theory and then 'quantizing' it. To be sure, there is something intellectually unsatisfactory about this: given that quantum theory is the more fundamental theory, we would prefer to work in the other direction, that is, to recover classical field theories from quantum starting points" – Wallace

Conundrum

“This is often the way it is in physics – our mistake is not that we take our theories too seriously, but that we do not take them seriously enough. It is always hard to realize that these numbers and equations we play with at our desks have something to do with the real world. Even worse, there often seems to be a general agreement that certain phenomena are just not fit subjects for respectable theoretical and experimental effort.” – Steven Weinberg

Through the looking glass

I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose. – J. B. S. Haldane