## Archive for April, 2013

### The Astronaut Always Wrings Twice

CSA Astronaut Chris Hadfield performed a simple science experiment designed by grade 10 Lockview High School students Kendra Lemke and Meredith Faulkner.

### Expertise is Fascist

The Fascism of Knowing Stuff

I attempted to explain to the journalist that the world we live in has never been more complex or filled with things that require work and patience to understand. Though democracy lovers may shiver at the idea, the penalty for living in the civilisation we currently walk through is that we must sometimes accept our ignorance and defer to others.

We should not trust people just because they are experts, but if we are not prepared to put the time and effort in to understand something, to take a step beyond that column we read in The Guardian or “what my friend Phil told me”, then we are placed in a position where must defer and try and make the best decision we can as to who we should defer to.

This is some pretty good stuff. I’ve mentioned things like this before — science is a meritocracy of ideas, not a democracy; similar to something Isaac Asimov said

Anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that ‘my ignorance is just as good as your knowledge.’

There is a reality that you have to accept: that there are things you don’t know and will never learn, so at some point you will have to trust an expert. Fortunately for people, weeding out the charlatans and lower tiers of self-proclaimed experts is not too difficult, if you have armed yourself with some basic knowledge and thinking skills — things that some basic science literacy can provide.

### Antares, Ahoy

The Flight Of Antares – Where To Look For It

What to look for, presented from a few different vantage points in the mid-Atlantic region, using Google earth as a backdrop.

### Powerful Things in Small Packages

New Microbatteries Are Tiny But Can Jump-Start A Car

With so much power, the batteries could enable sensors or radio signals that broadcast 30 times farther, or devices 30 times smaller. The batteries are rechargeable and can charge 1,000 times faster than competing technologies – imagine juicing up a credit-card-thin phone in less than a second. In addition to consumer electronics, medical devices, lasers, sensors and other applications could see leaps forward in technology with such power sources available.

No indication of when this might be commercially viable, or if it scales up to something that might power an electric car.

### A Hexapod Robot Makes a Cameo

I was cleaning up my inbox the other day and accidentally opened up the box below Admin, which is Answerguy, and one I had forgotten about. Several years ago I was “The Answer Guy” (or at least I had his email address) for our web page, back in the days when I took care of my research group’s web page. The legacy site is still present but in some sense is no longer “official” and has not been maintained in some time (the cesium fountain page has been dormant even longer). The current official page for work is much more sterile and doesn’t even discuss the clock details at all.

I got a number of inquires over the three or four years that the email address was active. A few crackpotty ones, several good questions, and a few from people who couldn’t find contact info on the pages other departments were maintaining, so there were several moon phase and time-of-sunset inquiries I punted. But I like this one, in particular:

To whom it may concern, My name is Christopher I am a sophomore in highschool and conducting a science fair project on time travel. I am not sure if this is the appropriate email address for this, but i am trying to obtain an atomic clock that measures to the nanosecond. If you have any information please please email me as soon as possible.

Sincerely, Christopher

### We Did a Science!

And by “we” I really mean the first author (Steve) who did all legwork of analyzing the copious clock data we generate, and had realized that our continuously-running clocks had an advantage over other groups who have been doing these measurements over longer intervals. I helped out a bit with the clock-building (and clock building-building) and thus data generation, and some feedback.

The arXiv version of “Tests of LPI Using Continuously Running Atomic Clocks” was posted (some time ago, sorry this is late) so you can follow along with the home version of the game, if you wish. Keep in mind that I am an atomic physicist, Jim, and not someone who really works with general relativity past the point of including gravitational time dilation in discussions about timekeeping.

One of the tests of general relativity, or specifically of the Einstein equivalence principle, is that of local position invariance. That is, local physics measurements not involving gravity must not depend on one’s location in space-time. Put another way, there shouldn’t be any effects other than gravitational ones if you do an experiment in multiple locations — the gravitational fractional frequency shift should only depend on the gravitational potential: $$frac{Delta f}{f} = frac{Phi^2}{c^2}$$

So you look for a variation in this. One possibility of investigation is to compare co-located clocks of different types as the move to a new location, that could behave differently if LPI were violated. This can arise if the electromagnetic coupling, i.e. the fine structure constant, weren’t the same everywhere. Then clocks using different atoms would deviate from the predicted behavior. Since we’re looking at transitions involving the hyperfine splitting, nuclear structure is involved, so the other possibilities that can be tested are variations in the electron/proton mass ratio and the the ratio of the light quark mass to the quantum chromodynamics length scale. One need not do any kind of (literal) heavy lifting of moving the clocks into different gravitational potentials because the earth does it for us by having an elliptical orbit — we sample different gravitational potentials of the sun over the course of the year.

In order to get the statistics necessary to put good limits on the deviation, other groups have done measurements over the span of several years, but this was because their devices were primary frequency standards, which (as I’ve pointed out before, probably ad nauseum) don’t run all the time, so you only get a handful of data points each year. Continuously running clocks, on the other hand, allow you to do a good measurement in significantly less time. You want to sample the entire orbit along with some overlap — about 1.5 years does it (as opposed to a few measurements per year, where you really need several years’ worth of data to try and detect a sinusoidal variation).

Another key is having a boatload of clocks. Having a selection is especially important for Hydrogen masers, since they have a nasty habit of drifting, and sometimes the drift changes. Having several from which to choose allows one to pick ones that were well-behaved over the course of the experiment. Having lots of Cesium clocks, which are individually not as good (but don’t misbehave as often), allows one to average them together to get good statistics. Finally, having four Rubidium fountains, which are better than masers in the long-term, adds in another precise measurement.

All of the clocks are continually measured against a common reference, so you can compare any pair of clocks by subtracting out the common reference, so we have relative frequency information about all the clocks. The basic analysis was to take the clock frequency measurements and remove any linear drift that was present in the frequency, and check the result for an annually-varying term. The result isn’t zero, because there’s always noise and some of that noise will have a period of a year, but the result is small with regard to the overall measurement error such that it’s consistent with zero (and certainly does not exclude zero in a statistically significant way).

We’ve pushed the limit of where any new physics might pop up just a little further down the experimental road — relativity continues to work well as a description of nature.

### A Mathectomy Will Kill the Patient

Math and Science Are Not Cleanly Separable

What I, and many other physical scientists, object to is the notion that math and science are cleanly separable. That, as Wilson suggests, the mathematical matters can be passed off to independent contractors, while the scientists do the really important thinking. That may be true in his home field (though I’ve also seen a fair number of biologists rolling eyes at this), but for most of science, the separation is not so clean.

As much as I agree with Wilson’s statement about the need for detailed knowledge to constrain math, even in physics, there is also some truth to the reverse version of the statement, which I have often heard from physicists: If you don’t have a mathematical description of something, you don’t really understand it. Observations are all well and good, but without a coherent picture to hold them all together, you don’t really have anything nailed down. Big data alone will not save you, in the absence of a quantitative model.

Yeah, what he said.

### Now You've Done It

Wired posts a picture of The Quiet Sun and two days later the sun farts in our general direction: Spring Fling: Sun Emits a Mid-Level Flare

Nice going.