the Ummm… Drive


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:


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.


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.

definitive proof that time travel is impossible

If time travel is possible, then the present is the past for an infinite number of futures. (Assuming the time stream is changeable by travelers, and not fixed).

In an infinite number of futures, there are a sub-infinity number of those futures in which a time traveler exists who finds today, the day you are reading this blog post, a fascinating and pivotal moment in history.

Therefore, even if only a small fraction of those infinite future travelers obsessed with our today actually bother/have the means to travel to today, there are still an infinite number of them.

Therefore, today there should have been an infinite number of time travelers appearing from an infinite number of different futures. Or, as Douglas Adams would have said, “whop

Of course the same argument holds for every moment of every day in all of recorded history, so basically we should be inundated with infinite numbers of time travelers arriving at every moment of time for all time.

Since that is clearly not happening, time travel must be impossible.

I’d love to see a What-If XKCD on the idea of an infinite number of time travelers arriving today, actually… would probably be a mass extinction, the Earth would suffer gravitational collapse, and we’d be in a black hole. I think.

why I love the snow (a #Nemo tale)

In Wisconsin, we got the tail end of Winter Storm Nemo last night, with just a few inches, and today it’s a beautifully sunny day. The outlook for the east coast however is between a foot and two feet, which is truly monstrous.

But no matter how much it snows (and living in Wisconsin these past few years, I’ve seen and shoveled my fair share), I can’t resist the snow. It is just beautiful, it always manages to enchant me. One of my favorite writers on the internet, Auston Habershaw, penned a perfect paean to snow that speaks to me as well as for me:

Snow is something enchanted. It changes the whole world, flake by flake, degree by degree, until we emerge from our hiding places and find ourselves somewhere new and clean and fresh. The drab ordinariness of our daily world is now blanketed in silence and light, glowing beneath an invisible sun. You breathe deep, and the air sears your lungs with its chilly clarity. It’s like waking up from a bad dream and letting all the heavy, sticky violence of your nightmare fall away. There ‘s just you, alone, calm and surrounded by the quiet beauty of a new world.

It is no accident to my mind that CS Lewis had Lucy stumble through the wardrobe and into a Narnia locked in eternal winter. There seems nothing else in nature that captures the mystery and enchantment of life than a wood cloaked in shimmering ice.

there’s more, read the whole thing. I shared it on Facebook too and I hope it goes viral. Snow is beautiful. Even if you live in Northrend.

Also, did you know that it’s the Weather Channel that started naming these winter storms, not the National Weather Service? Literally an invention of their marketing department, and inspired by Twitter. Go figure.