The Skeptical Teacher

Musings of a science teacher & skeptic in an age of woo.

Live Blog of CFI Chicago’s “Dangerous Nonsense” – Entry #2

Posted by mattusmaximus on April 24, 2010

Speaker #2: Dr. Michael Albrow , physicist at FermiLab, talking about “What’s True and What’s Untrue in Physics Today?”

Opening joke: please take away from this that physics is much simpler than biology! :)

Some knowledge is as certain as certain can be, while some things are necessarily uncertain.  There is much we know is not possible, but there is much which we know is also outside of our domain.

The beginning of modern science probably started with Galileo and his conflict with the Church.  Differences between science & religion…

Science:

*distrust authority / only Nature is authority

*criticism encouraged

*all hypotheses are testable by repeatable experiments / observations

*try to fault existing theories, make progress

*theory = explanation

*disagreements are healthy

*accepted standards of statistics & evidence

Religion/Nonsense/Nonscience:

*dogmatic

*questioning / criticism not encouraged

*not fundamentally upheld to testing

*”theory” = speculation

*disagreements discouraged / when scientists disagree that mans they’re wrong

*poor understanding or misuse of statistics & numbers

For example, the idea of perpetual motion is okay (the Earth moves perpetually around the Sun, atoms move perpetually due to thermal energy, etc).  But perpetual motion machines… or energy generation… is impossible.  That is because whenever energy converts from one form to another, due to the Second Law of Thermodynamics, some random heat is made.  These transformations thus have a maximum level of efficiency.

What about grabbing energy out of the vacuum? Only possible when looking at extraordinarily small time scales (due to the Heisenberg uncertainty principle).

Bottom Line: don’t go buying “free energy” shares anytime soon!

Noether’s Theorem (1915): To every continuous symmetry there corresponds a conserved quantity.  This includes symmetry under rotations (angular momentum), translations (linear momentum), and translation in time (energy).  Energy conservation is as certain as certain can be… but what about in the big bang?!

Quantum Mechanics: let’s talk about Schrodinger’s Cat… put a cat in a box with a radioactive source.  If the source randomly emits a particle it sets off a device which kills the cat.  The box is closed and time passes – is the cat alive or dead?  The answer, in the view of QM, is that before the box is opened the cat is in a combined state of being both alive & dead simultaneously!

But what about the role of the “observer”?  Well, the universe evolved for billions of years without any observers (except the “gods” :) ).  So the notion of a wavefunction suddenly “collapsing” when an event is “observed” is questionable.

Wavefunctions “collapse” when quasi-irreversible event occurs, such as radioactive decay, ionization, neutron decay into a proton-electron pair, etc.  This is because while energy is conserved, the level of entropy increases.  So this has nothing to do with “observers”.

Canonically Conjugate Variables: momentum & position, energy & time, and angular momentum & orientation.

Heisenberg Uncertainty Principle (HUP): you cannot know both precisely the values of these CCVs, so there is an absolute limit to our knowledge.  This is another nail in the coffin of determinism.  However, usually the HUP applies at the (sub)atomic level; but some quantum events can be amplified to macroscopic proportions.

Aside… where do thoughts start?  Are they simply the result of quantum fluctations in the brain at the neuronic level?

Apart from QM, there are examples classically that the future is not determined by the past.  For example, look at classical physics branch points: unstable equilibrium of a pencil standing on its tip, asteroids (interplanetary billiards & death of dinosaurs), and volcanoes in Iceland!

The ultimate quantum amplification is probably the Cosmic Background Radiation (CBR), where the early universe had tiny variations in density & temperature in the microwave background only about 300,000 years post big-bang.  These variations are only colder or hotter by about 1/1000th of a degree Kelvin.  From this, and other info, we know the universe is about 13.7 Byr old (not 6000!).  In addition, the behavior of the universe’s expansion breaks down as follows: matter we understand 4%, dark matter 26%, dark energy 74%.

Once upon a time, 13.7Byr ago… inflationary theory tells us that a “dot” about 10^-33 cm across came into being.  It wasn’t really BIG, and it wasn’t so much an explosion so there wasn’t a BANG.  But it’s still exciting.

Recently, the National Science Board held its biannual survey of scientific literacy in the U.S. deleted two questions and the results from its report…

“The universe began with a big explosion” 33% yes

“Humans evolved from earlier forms of animals” 45% yes

The defense was that we don’t want to ask science questions that are “value related” – WTF?

Astronomy, Cosmology, etc: There are roughly 10^11 galaxies in the universe, with about 10^11 stars per galaxy, so how many have life, intelligent life, and even advanced civilizations?

What about interstellar space travel?  What is fiction vs. reality?  According to time dilation, what takes many years according to a stay-at-home person takes much less time for a spacewoman if she goes really fast.  But it only helps if you’re traveling a really high % of the speed of light, and this then begs questions of fuel storage and whatnot. What about travel through wormholes or other spacetime fantasies?  Almost certainly not, because “stable” wormholes” would be extremely small (~10^-33 m).

Antimatter rocket fuel or bombs?  FermiLab generates 60 MW for one day –> ~ 10^-9 grams of antiprotons –> 60W x 15 sec.  If you could bottle this, you’d only have ~10^-20 grams (???)

People often extrapolate wildly (“100 years ago no one thought we could fly”) and hope this leads to seemingly miraculous technological progress in the future.  But it butts up against fundamental physics.

Consider Gravitation: Pre-Newton – falling to the ground was the “natural state of things”, and ditto for the Moon and Sun in the sky.  Newton – Force = mass x acceleration and iit is a brilliant unification that almost fit everything.  Still: “every mass attracts every other mass…” could be disproved but never proved 100%.

Lititle problem with Newton was things like Mercury’s orbit precessing.  Einstein came along and used general relativity to revise Newton’s theory.  It fixed the problems with Newton’s theory, and so far every test of GR has confirmed the theory, but is there anything deeper / more correct (say, at the Planck scale) that we haven’t discovered yet?

Accorgind to GR, space & time are bent by curvature due to graviity.

Einstein Wannabees (EWs): Point to the fact that Einstein was also an unknown with no PhD working in a patent office, etc.  His relativity was also “difficult” to understand and has strange consequences.  But the difference is that Einstein’s ideas stood up to scientific scrutiny!

Particles: they are really tiny!  Probing the very, very small we find the Standard Model…

Each one of these particles has an anti-matter partner.  In addition, the mass of these particles is the same here as it is everywhere.  Why?  This is where the hypothetical Higgs boson comes in.

Force carriers: the electromagnetic force is carried by photons, weak nuclear is carried by W, Z bosons, and the strong nuclear is carried by gluons.  We haven’t yet detected the carrier for gravity – the graviton.

Looking for neutrinos: difficult to detect because they have no charge & practically no mass.  It took decades to finally detect them because there are three different types (flavors) that oscillate after leaving the Sun and change flavors, and the detectors were designed to detect only one flavor!  Here’s an example of a deep-underground neutrino telescope…

FermiLab: has the particle accelerator called the Tevatron (4 miles around).  Looking to answer questions like: what is dark matter? What is dark energy?  Does the Higgs boson exist? Are there higher dimensions to our universe?  String Theory?  Can we re-create the big bang in the lab? etc…

LHC: an even bigger particle accelerator in Europe created to answer similar questions.  This thing is huge!!!  The LHC is exciting because it will be probing energies about 10x higher than ever before.

What about “Theories of Everything” such as superstring theory?  Sounds neat, but it isn’t yet testable, falsifiable, and perhaps therefore not (yet) a full science.

Lots of “miracles” for us to get here… designed? Just is? The Goldilocks Dilemma.

Are there other universes?  If so, where are they?  What are their properties, laws of physics, etc?

With all this, how can anyone leave school still thinking creation was only 6000 years ago?

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2 Responses to “Live Blog of CFI Chicago’s “Dangerous Nonsense” – Entry #2”

  1. Michael Albrow said

    These are notes from my lecture, written up but not by me. One significant correction:
    “Antimatter rocket fuel or bombs? FermiLab generates 60 MW for one day –> ~ 10^-9 grams of antiprotons –> 60W x 15 sec. If you could bottle this, you’d only have ~10^-20 grams (???)”
    Should be rather:
    Fermilab uses (not generates) about 20 MegaWatts and produces about 10^14 antiprotons per day at great expense.
    IF (a big IF) you could store all these (an antimatter battery) and convert into electricity with 100% efficiency, you could light a 60W light bulb for about 15 seconds. A far more realistic idea (!) would be to power a rocket with AA batteries!

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