dinsdag 30 april 2013

In Memoriam: Job Vlijm

Last week a dear person in my life past away. He will be missed. After his dead I read a speech of a scientist about what he would say at a funeral. For me this gave me support, therefore I put it here for everybody to read (I got it from a well known facebook page).

You want a physicist to speak at your funeral. You want the physicist to talk to your grieving family about the conservation of energy, so they will understand that your energy has not died. You want the physicist to remind your sobbing mother about the first law of thermodynamics; that no energy gets created in the universe, and none is destroyed. You want your mother to know that all your energy, every vibration, every Btu of heat, every wave of every particle that was her beloved child remains with her in this world. You want the physicist to tell your weeping father that amid energies of the cosmos, you gave as good as you got.

And at one point you'd hope that the physicist would step down from the pulpit and walk to your brokenhearted spouse there in the pew and tell him that all the photons that ever bounced off your face, all the particles whose paths were interrupted by your smile, by the touch of your hair, hundreds of trillions of particles, have raced off like children, their ways forever changed by you. And as your widow rocks in the arms of a loving family, may the physicist let her know that all the photons that bounced from you were gathered in the particle detectors that are her eyes, that those photons created within her constellations of electromagnetically charged neurons whose energy will go on forever.

And the physicist will remind the congregation of how much of all our energy is given off as heat. There may be a few fanning themselves with their programs as he says it. And he will tell them that the warmth that flowed through you in life is still here, still part of all that we are, even as we who mourn continue the heat of our own lives.

And you'll want the physicist to explain to those who loved you that they need not have faith; indeed, they should not have faith. Let them know that they can measure, that scientists have measured precisely the conservation of energy and found it accurate, verifiable and consistent across space and time. You can hope your family will examine the evidence and satisfy themselves that the science is sound and that they'll be comforted to know your energy's still around. According to the law of the conservation of energy, not a bit of you is gone; you're just less orderly. Amen.
-Aaron Freeman.
In Memoriam

Job Vlijm


Semarang, 26 February 1954 - Leiden, 28 April 2013



zondag 21 april 2013

Reducing uncertainty: Jupiter really has four big moons, I just wasn't sure

This week I had to defend science a lot (which means I was a lot on facebook and twitter, following discussions between religious people, scientists and people that just like to shout things). I noticed that the definition of science is unclear, not well understood and just disregarded in internet discussions. I know that you cannot be right on the internet (You will miss a good night sleep, next to a gorgeous lady (xkcd)), but I can try ;). There are many definitions of science but I like the following one:

"Science has the purpose to reduce uncertainty with use of observation and discussion"

It clearly states that science does not (really not, so please keep this in mind) have absolute answers to all the questions in life, but tries to keep us busy (with a lot of discussion) by reducing the uncertainty in the answers. It says don't panic, just look around and enjoy. Observations play a primarily and important role in this process. My link to the rest of the blogpost (I got some feedback of a dear friend, who is reading this blog, saying that I jump from subject to subject without clear preparation for the reader. I think it just keeps you focused :)).

A historic observation which changed mankind's view of the world, also changed me in some sense. It happened on a late summers evening. I visited my parents house in Renesse (known by Dutch youth for its interesting summer holiday parties, but known by astronomers for the clearest sky in whole of the Netherlands). My dad and I were enjoying some good whisky that evening. We were gazing at the sky,  the moon was very visible making the scene fantastic (or maybe the whisky, lets just say we had some good discussions). During that summer also the planet Jupiter was clearly visible in the night sky. Being a little bit intoxicated by a very good 'tasters choice' edition of a 16 year old Lagavullin whisky, we decided to make pictures of Jupiter, hoping to catch a glimpse of its moons (who are not visible with the naked eye, even if you squint your eyes and put your hands like a binocular).

Our theory was to use a long shutter time and a fully deployed (zoomed in) camera lens to catch a few photons reflected of the surface of the four Jovian moons. Making an engineering-based camera holder (in other words, study books and the camera strapped together with a lot of duck tape), such that the camera was immovable and pointing towards the largest planet of our solar system. We totally forgot that in those few seconds (shutter time), the Earth moved a little bit, making Jupiter and its moons, seen as five parallel white lines in the night's sky. But we did not give up and experimented for a few minutes when suddenly we saw the same figure as Galilei Galileo did (and Simon Marius, but he was three days to late, see previous blog), changing our perspective of our view of mankind. For me it was the beginning (well sort of, one of the several beginnings) of my scientific mindset.


This picture was taken on 21 august 2010 23:51:27 (Amsterdam time). In a backyard of a house in Renesse, Schouwen Duiveland, Zeeland (So you can figure out which dot belongs to which moon, ephemeris data can be found here).

The camera we used was a simple Canon EOS 350D Digital, with a 70.0-300.0 mm lens. For this observation, we used the following set-up of the camera: Iso 800, 300.0 mm lens, F 5.6 and a shutter time of 1/3 second. This also solved the movement of Earth (the Earth doesn't move a lot in a blink of an eye), resulting in round (non striped) dots being Jupiter and its four large moons.


zondag 14 april 2013

My first 'real' scientific report: Rossby wave observations in the Atlantic Ocean

My background is not entirely scientific (maybe that is a good thing, I don't know). I've done my bachelor and masters at the faculty of Aerospace Engineering of TUDelft, which is a Technical University. The biggest part of the education is focused on engineering problems, team work and just building cool stuff. Which is great, but completely different from scientific research (we could debate this, but that is for another blog post (email me ;))). So what decided me to dedicate my life (well for now, I can't look in the future) to science.

In our last year of bachelor, we have an end project called the Design Synthesis Exercise. Ten students, ten weeks, locked up in very small room, creating, designing and engineering. Our assignment was to design a mission to Ganymede to find evidence for a sub-surface ocean. Cooooool!!! After a lot of work and fun, we came up with the Marius Space mission (Simon Marius (No not Galileo) was the second man (yes the first one was Galileo) that observed the Jovian moons, and gave them their current names (Galileo's were stupid)). One of the our team members had just followed a movie-making course, so you can see our end-result in a well designed Hollywood trailer (There is a rocket coming up from the ground, which is kinda cool. And you can see me nodding in-time, with a terrible haircut). Oh, the design looks a lot like the current Juice mission. We gave ESA our design, and they were well, flabbergasted (is this how you spell it) and used it...

Back to reality. During this assignment the supervisor of this project inspired me in looking at the science of the mission. I discovered the beauties of Ganymede and the men and women trying to get sense of what was going on there. His inspiration to me was so great that I decided to do my master thesis research under his supervisie.

My master thesis research was quite engineering oriented: Improving the current orbit determination of Cryosat-2 (the first one blew up), by looking at new laser ranging formats, trying different terrestrial reference frames and introducing a micromodel of the satellite for the solar radiation pressure modeling. All very engineering, however I discovered something very cool during my literature study.

My supervisor gave me a book (Satellite Altimetry and Earth Sciences, by Lee-Lueng Fu and Anny Cazenave) and said to read it, learn from it and try to summarize it. He gave me an extra task, which was the following. "Try to reproduce this figure."


This is not the true figure from the book, but my result, which looks the same (if you don't believe me, read the book and learn the wonders about satellite altimetry). What does this figure illustrates? I will try to explain.

First always look at the axis, what do they represent: x-axis, latitude in degree, ranging from -50 to 50 degrees (look at your globe, or use this), y-axis, propagation speed in cm/s (slow moving stuff). Then title: hmmm, that is not giving me any more information than when I not looked at it (google: hmmm, first find tells me something about an Interannual baroclinic Rossby wave, that is interesting!!!). Legend: There is something theoretical, something to do with basins (ah, ocean things, so the stuff must be propagation speed of waves (Rossby wave in particular). Just by not looking at the middle of the figure, I am getting there) and I see different names of altimeter satellites. In the end, looking at the figure: the dots, squares and asterix sort of follow the theoretical line, but not quite.

What we see is the dispersion relation of slow moving waves (Rossby waves) with their latitude dependence. Rossby waves move slower in areas with greater latitude and they move faster towards the equator. What we also see is that the theory doesn't quite fit the data, why this is I did not know, but I had some ideas (I think today researchers found the reason for the misfit with the linear theory, but I have to find the article (I will come back to you with that, maybe...)). 

But the most interesting thing is what are these so-called Rossby waves and how can you (yes, you, just like me) observe them. Rossby waves (oceanic ones, there are also atmospheric ones, the more famous ones, but I am with the underdog ;)) are waves that propage from east to west (against Earth's rotation) in the oceans. They are one of the only means to give climate information of eastern part of oceans to the western part. Their amplitude is usually a few centimeters, but their wavelength can go up to 100 kilometers. Due to these sizes you will not notice them when they pass you if your on a boat, but they are visible from outer space.

Altimeter satellites are measuring the oceanic surface for decades now. Satellites like ERS-1 and -2, TOPEX/Poseidon Envisat and Jason-1 and -2 have high accurate altimeters onboard, measuring the distance between the satellite and the ocean surface up to mm accuracy. After precise determination of the position of the satellite (which was my master thesis research goal, for Cryosat-2) the geometry of the ocean surface is measured. This data is available for everybody, so if you want to look at waves, go for example to the rads database. A database (set-up by our group) containing all space altimetry observations.

To view the Rossby waves, extract a long time series (few months, this is the time a Rossby wave needs to cross the North Atlantic) of one particular latitude of the tidal-free ocean height measurements. An area like depicted in the figure:

Collect all the measurements in bins of a few days of this area and plot the pixel rows below each other like a time serie (Just like the waterfall plot in my previous blog posts (hmm, science looks a lot a like)). The results would look like the following:


Here time runs from up to down and the x-axis depicts the longitude in degrees. I've normalized the height measurements. In the lower figure the bathymetry (ocean floor) is illustrated (I hoped to see some ocean floor dependency). In the color plot, Rossby waves are seen as stripes from up-right to low-left (reddish colors). To estimate the velocity of these waves, you should calculate the slope angle of these lines. If you do this correctly the velocity will be around 2-3 cm/yr (at 34 degree latitude). A clear distinction between the west and east part of the plot is seen (angle is smaller in west part than in east part), which tells us that Rossby waves flow faster in the west part at latitude 34 degree. 

At this latitude the Gulf stream is flowing, which is a bit counter intuïtieve, because the Gulf stream flows the other way (west-to-east), against the Rossby wave. However due to some energy interaction (I don't have a clue), this results in an increase of propagation speed of the Rossby wave. They flow faster against the stream.

These kind of waves will never be seen on television or other media, but I think they are cool. We try to model these waves, which can only be observed by satellites, but still they show us strange interactions and can give new insights in ocean modeling. They are a good example of science that is purely curiosity based. But could have a great impact in modeling (for example in climate models, which is news and media important, ah well...).






A small update for those who care...

Just got back from the hospital. I could not believe it is already more than a week ago that we got the terrible news of my girlfriend's father. This week was a roller coaster of emotions for her, her family and me.

However, after just communicating with him, it all feels beter. The sun is shining in the Netherlands giving her father that extra energy for his recovery. And hopefully he will become his old self again :)

Thank you for the kind words we received during these stressful times. They were of great support to us. Thank you.

maandag 8 april 2013

The story of not attending EGU2013 in Vienna

A few ours before my flight to Vienna would depart, my girlfriend and I were called. We had to come to the hospital, because the father of my girlfriend was taken to Intensive Care. His lungs were failing and his blood pressure dropped. So instead of racing to the airport we got in the car and were flying to the hospital.

Arriving at the IC, the rest of the family was already there. He was put in an artificial coma and taken on a breathing apparatus. It all felt so fragile. The doctors and nurses were however able to make him stable for the rest of the day.

It all went so sudden and unannounced. The night before I had subscribed myself to be on the official EGU2013 blogroll to write about my experience visiting my first EGU conference. However, due to these circumstances I have decided not to participate in the conference. I want to support my girlfriend and her family.

There is some good news after 48 hours of stress and waiting. The doctors and nurses are in control. They probably found the cause of the lung failure and are treating for this. The first signs look promising.

I will not participate in EGU2013, however when I find some time for the webcasts I will report on some of them. Please have fun and find interesting science. You can contact me via this blog if you find something worth writing about.

Observe, connect and discuss...

See you at EGU2014



maandag 1 april 2013

Doubts of two scientists...

Last week I finally solved my satellite signal processing problem (with the help of my dear colleague). As I posted a few weeks ago, we are setting up a tracking station for satellites with some students here at the TUDelft. We record the signal coming from satellites and try to extract the frequency and frequency shift of that signal. Using the Doppler effect we can make an educated guess of where the satellites are and how fast they orbit the Earth (which is super-awesome!).

However, back to the problem. We record the signal in .wav format. This file consists of two channels, which both represent a signal as a time-serie with deviations from zero (when plotted it looks like a wavy pattern). However, there are two channels and at first I only used one of the two channels (I know now this is wrong, but hé, it was my first time dealing with this). In my first blog-post I showed a figure of the signal, however this figure was made by professional (wel, I think) open-source software. As a true Delft-engineer, I wanted to do it myself, just because I can. When I performed a Fourier transformation on the signal (one channel), I thought I got the correct result:

Time runs from up to down and the frequency bandwidth is shown on the horizontal axis. The signal was sort of mirrored around the center frequency (this was not a case of satellite synchronized swimming). I did something wrong, but me not being a signal processing expert, I could not understand what I did wrong. The best thing to do in such a case, is to leave the project alone (or go to the toilet with a cup of coffee, but I already tried that several times). 

After a few weeks, the problem was running around in my brain, screaming to be solved. Fortunately, my colleague needed to work with the Fourier transform (He is doing two-way laser ranging for interplanetary satellite missions, its kinda cool!!!). He asked me if he could use my data to see if his software is doing the correct thing. He got the same results as me, when he used only channel one of the .wav file. 

He, being a bit more (but also not an expert) known in the topic about electromagnetic radiation, came with the note that radio waves are complex. The radiation oscillates in the electric and magnetic field, creating a complex wave (A good figure is seen at, where else, wikipedia page). So he came up with the idea to make the second channel of the .wav file the imaginary part (just multiply the signal with the square root of -1, "Is this possible?", yes, it is.) of the complex signal and add it to the signal of the first channel. 

After doing the Fourier transform on the new and complex data (after zooming in on the signal), we got a beautiful figure of the Doppler shift in the carrier frequency of the satellite:

We'd extracted the same figure as the professional software did. I did a victory dance, for about two second, before I went back to work. But this is where my doubts started.

What was recorded on the .wav file? Is it the actual complex wave from the satellite, stating the trajectory of the energy package? Or is it a complex signal that could represent the signal best measured by the antenna, only stating the electric component of the signal, and therefore it is possible to see at both sides of the center frequency? This is where my knowledge stops about electromagnetic radiation. But I will try to find out what is really happening, because that is what science is about...