Goodbye, Cassini

I met Cassini in 1996 at JPL before it departed for Saturn. For 20 years I have cheered its mission. That mission is over, and Cassini’s watch has ended.

I posted this six years ago here at haibane, but it’s worth reposting in salute: an incredible compilation of a flyby of the Saturnian system:

5.6k Saturn Cassini Photographic Animation from stephen v2 on Vimeo.

the hype about Hyperloop

Elon Musk comes to town
Elon Musk comes to town

This article makes an important point about the Hyperloop:

America has the means to reduce traffic and connect people to where they want to go in less time — but solving these problems entails politically difficult choices to shift travel away from cars and highways. Any high-tech solution that promises a shortcut around these thorny problems is probably too good to be true.

I can’t help but see an echo of the wishful thinking surrounding the EMDrive in the Hyperloop marketing campaign. Maybe I’ll be proven wrong.

Here’s the original white paper PDF from Elon Musk, and here’s a rather detailed critique by mathematician and transit analyst Alon Levy. Anyone who takes Hyperloop seriously should read both.

the Ummm… Drive

figure19

So, there is now a peer-reviewed paper on the fabled EmDrive, which empirically measured a statistically significant thrust. The important results are in Figure 19 up above, and here is what the paper has to say about it:

Figure 19 presents a collection of all the empirically collected data. The averaging of the forward and reverse thrust data is presented in the form of circles. A linear curve is fitted to the data and is shown with the corresponding fitted equation. The vacuum test data collected show a consistent performance of 1.2±0.1uN/kW

It’s not clear if the fit was to the averaged data or the raw data. I suspect the averaged, because looking at the raw data, at no time did thrust exceed 130 uN, even when power was increased from 60 to 80 kW. In fact the data at 80 kW points averages out to the same thrust as at 60 kW, and the error bars are a textbook example of the difference between accuracy and precision.

These results are peer-reviewed, and there is a “statistically significant” linear fit to the data that does demonstrate a correlation between the input power and the observed thrust, but this data does not show that the EmDrive actually works. As Chris Lee at Ars Technica put it, the drive still generates more noise than thrust:

The more important point is that the individual uncertainties in their instrumentation don’t account for the variation in the thrust that they measure, which is a very strong hint that there is an uncontrolled experimental parameter playing havoc with their measurements.

Lee also points out that there are a lot of experimental questions left unanswered, including:

  • Why are there only 18 data points for an experiment that only takes a few minutes to perform?
  • Where is the data related to tuning the microwave frequency for the resonance chamber, and showing the difference between on-resonance mode and an adjacent mode?
  • What is the rise-time of the amplifier?
  • What is the resonance frequency of the pendulum?

on that last point, Lee elaborates:

The use of a pendulum also suggests the sort of experiment that would, again, amplify the signal. Since the pendulum has a resonance frequency, the authors could have used that as a filter. As you modulate the microwave amplifier’s power, the thrust (and any thermal effects) would also be modulated. But thermal effects are subject to a time constant that smears out the oscillation. So as the modulation frequency sweeps through the resonance frequency of the torsion pendulum, the amplitude of motion should greatly increase. However, the thermal response will be averaged over the whole cycle and disappear (well, mostly).

I know that every engineer and physicist in the world knows this technique, so the fact that it wasn’t used here tells us how fragile these results really are.

This is really at the limit of my empirical understanding, but it’s a question that the authors of the paper (not to mention anyone over at /r/emdrive) should be able to field with no worries.

Basically, this paper doesn’t answer any of the substantive questions. But it does at least validate the notion that there is something going on worth investigating. But let’s be real about the outcome – because we’ve seen this before:

For faster-than-light neutrinos, it was a loose cable. For the BICEP2 results, it was an incorrect calibration of galactic gas. For cold fusion, it was a poor experimental setup, and for perpetual motion, it was a scam. No matter what the outcome, there’s something to be learned from further investigation.

and that’s why we do science. It’s not as if scientists are fat cats out to protect their cash cow. (Seriously. I wish it were so). Maybe we are on the verge of another breakthrough, but it will take a lot more than this paper to convince anyone. And that’s as it should be.

“Blood moon” lunar eclipse as seen from Madison, WI

Photos of the blood moon eclipse of April 15th 2014, taken at 3:00 am using a Canon G5:

IMG_8057IMG_8048

No tripod, unfortunately. But well worth the interrupt in sleep. The window in the cloud cover was perfect! Magnificent!

UPDATE – great writeup from EarthSky on why Mars was so close to the moon, and a nice illustration from Classical Astronomy page on Facebook that matches the picture – the blue star to the lower right is Spica and Mars is the bright red spot on the upper right.

eclipse-mars-spica-Classical-Astronomy

Reason is a limited process and can never explain everything objectively

Reason is a limited process because it arises from consciousness, which observes the universe via filters. The mind has physiological filters (ex, wavelengths of light you can perceive, frequencies of sound you are limited to), chemical filters (the specific biochemistry of your brain, your mood and emotion, etc), and mental filters (pre-existing ideas and biases, fidelity of your metal models and assumptions, simple lack of knowledge). These are all best understood of as filters between you and the “objective” truth of reality. The universe as you observe it and understand it is vastly more complex than you can understand. The process of reason happens only with information you can process at the end of that chain of filters, so you are always operating on an insufficient dataset.

The brain is actually evolved to extrapolate and infer information based on filtered input. The brain often fills in the gaps and makes us see what we expect to see rather than what is actually there. Simple examples are optical illusions and the way the brain can still make sense of the following sentence:

Arinocdcg to rencet rseaerch, the hmuan brian is plrectfey albe to raed colmpex pasasges of txet caiinontng wdors in whcih the lrettes hvae been jmblued, pvioedrd the frsit and lsat leetrts rmeian in teihr crcerot piiotsons.

As a result, there are not only filters on what we perceive but also active transformations of imagination and extrapolation going on that actively modify what we perceive. These filters and transformations all happen “upstream” from the rational process and therefore reason can never operate on an untainted, objective reality. Despite the filters and transformations, the mind does a pretty good job, especially in the context of human interactions on the planet earth (which is what our minds and their filters and transformations are optimized for, after all). However, the farther up the metaphysica ladder we go, the more we deviate from that optimal scenario for which we are evolved (or created, or created to have evolved, or whatever. I’ve not said anything to this point that most atheists and theists need disagree on).

A good analogy is that Newton’s mechanics were a fantastic model for classical mechanics, but do not suffice for clock timing of GPS satellites in earth orbit. This is because Newton did not have the tools available to be aware of general relativity. Yes, we did eventually figure it out, but Newton could not have ever done so (for one thing, his civilization lacked the mathematical and scientific expertise to formulate the experiments that created the questions that Einstein eventually answered).

Godel’s theorem makes this more rigorous by demonstrating that there will always be statements that can neither be proved nor disproved by reason. In other words, as Douglas Hoftstadter put it, Godel proved that provability is a weaker notion than truth, no matter what axiom system is involved. That applies for math and it applies to philosophy, it applies to physics and it applies to the theism/atheism debate.

Related – more detailed explanation of Godel’s Theorem and implications on reason.