I’ll try not to make this too much of a rant. Having had a physics education over the years, I tend to pick up on people’s confusion of certain concepts. The most common one is that people don’t seem to be aware of the difference between weight and mass.
Roughly speaking, mass, is a measure of how much stuff there is of something, and we measure it in “Kilograms“. Whereas, weight, is how much downwards force an object exerts due to its mass, and we measure force in “Newtons“. So you see, it is an invalid statement to say that something weighs 10 kilograms. Also, when you weigh something, you’re determining its mass, by measuring its weight. Scales are calibrated to read off in units of mass, by now much weight/force is being exerted on them.
Numerically, the difference between the weight and mass of a given object comes from the Earth’s gravity. Denoted “g“, it has a value of around 9.81 m/s2, that’s “meters per seconds squared” to you, which is the unit by which we measure acceleration. The formula to convert mass to weight is simply (yes there’s some maths!),
Weight = Mass * Earth’s Gravity
W = M * g
So next time you’re talking about how much of something you’re getting, you’re talking about mass, unless you’re talking about lifting or carrying something, then it’s weight. When you read your bathroom scales, that number isn’t your weight, it’s your mass. If you don’t remember this lesson for yourself, then remember it for all us poor balding physicists who are slowly tearing our hair out at such misuse of language!
A first for this blog, a movie review, again on the theme of the International Year of Astronomy. BLAST The Movie tells the the tale of an intrepid team of scientists hoping to travel back in time … on a balloon.
Yes, it sounds like science fiction, but it isn’t. BLAST is an acronym for Balloon-borne Large Aperature Sub-millimetre Telescope. The BLAST project, lead by principal investigators, Mark Devlin and Barth Netterfield, was a project to both train graduate astrophysics students and to probe into views of the very early universe.
How do we see back in time? Because light travels at a set speed, it does not instantly go from point A to point B. So, light from the most distant sources is also the oldest light. That is how we see back in time.
Seeing back into time
This film was by Paul Devlin (any relation to Mark? Mark Devlin’s brother, thanks gmarsden) who has made two previous films (“Slam Nation” and “Power Trip“). While still paying all due attention to the scientific content, the documentary covers much more. In fact, it has many ingredients of a great drama. Much attention is given to Mark Devlin’s family and the effect that his prolonged absences have on his wife and two young sons. Also, some scenes are given over the two project leaders, Devlin and Netterfield, where they talk about science and their religious views. Devlin being an atheist and Netterfield being a Christian. All the while the spectre of failure hangs over the project as they hope they can collect the best astronomical data possible and then retrieve it from some of the harshest environments on Earth!
However, the greatest moments of drama belong to the telescope itself, by virtue of old saying what goes up, must come down. Both of the BLAST flights lasted for six days, during which time it collected vast amounts of data, far too much to be transmitted to satellites. Therefore the data had to be recorded to hard drives instead, which meant that BLAST had to parachute back to Earth and be recovered. I shall not give away whether BLAST was successfully recovered or not from either flight though! All I will say, as above, was that success was by no means guaranteed, given that the first flight had to be recovered from the far frozen north of Canada, and the second flight from the frozen wilderness of Antarctica!
BLAST's hard drives which need to be recovered after a flight
In case you are not into astronomy and wondering why on Earth (pun intended) you would want to fly a telescope on a balloon, here’s why. Above our heads, we have about 20 miles of swirling gas, i.e. the atmosphere. All of of this blurs and distorts light coming from space and limits the effectiveness of ground based telescopes. (Addendum: Not only that, but our atmosphere absorbs almost all of the wavelength the BLAST scientists wanted to observe. thanks gmarsden). You’ve probably heard of the Hubble Space Telescope. This is a huge telescope orbitting our planet which is most definitely outside of our atmosphere. However, achieving such a feat is hugely expensive. Therefore, creating a more modest telescope, flown up by a balloon instead of the shuttle is cheaper and somewhat easier to do. As I aluded to above, the disadvantage seems to be the recovery procedure.
I only came across this film as part of a BBC4 astronomy night. It was on the BBC iPlayer (UK viewers only), which has now expired, so I know I’m a little late to be telling you how good this was. However, you will be able to buy a DVD from the BLAST website if you are interested by my write up. Also, you can simply donate to the project if you would like to support the BLAST Movie project (by means of funding or hosting screenings), which IMHO is a fantastic way to reach out to children and the general public about the valuable work being done in astrophysics and experimental cosmology. Support BLAST!
In the meantime, you can watch a trailer for BLAST The Movie.
Since 2009 is the International Year of Astronomy, here is something I thought I’d pull out of my personal archive. It is a dissertation I wrote for the third year of my MPhys, reviewing achievements in cosmology between 1916 and 1999. I invite everyone who reads this to add any achievements in cosmology since then in the comments! If I get enough interest in this post, I’ll consider writing an updated version.
Something I heard about on Security Now (Ep.117) has got me rather excited and I wanted to report about it on here.
Batteries vs Capacitors
Standard mobile phone Li Ion battery
Currently, the state of the art for energy storage in contemporary electronic devices is Lithium Ion batteries. Despite the material used (the electrolyte), batteries are all pretty much the same, in as much as a chemical reaction occurs inside the battery which drives electrons that our electronic devices can use to do work. Rechargeable batteries use a reversible reaction, so that once you do electrical work on the battery (i.e. charge it), the reaction is reversed and can begin again to power your devices.
There are a number of disadvantages to this. Firstly, because we are reversing the chemical reaction of the battery, it takes quite a while to charge them. Also, again because of relying on a chemical reaction, disposing is difficult because the contents are toxic. Also, rechargeable batteries degrade over time, so there are only so many times that you can discharge and recharge them.
Various capacitors
In electrical circuits energy can stored in components called capacitors. Capacitors aren’t used in place of batteries because the amount of energy you can store for a given size (i.e. their energy density) has been tiny. A little bit of physics for you here, which you need to know to understand the significance of what I’m leading up to telling you! The standard unit of capacitance is the Farad. Most capacitors you come across are rated at the micro Farad level (i.e. a millionth of a Farad), ranging up to a few hundred micro Farads. In my personal experience I have only seen 1 Farad capacitors for car stereo systems, although the things are massive and expensive.
A capacitor is two parallel metal plates (connected to a circuit) sandwiching a non-conducting material called a "dielectric".
Capacitors work differently to batteries. The general model of a capacitor is two parallel metal plates separated by a non-conducting material called a “dielectric“. The idea is that when you apply a voltage to a capacitor no current can flow through, but instead the electrons pile up at the cathode and create an electric field within the dielectric. Therefore, energy is stored in a capacitor as an electric field. Hence, a desirable dielectric material is one in which electric fields can easily form (which is a physical property known as permittivity). There are some limits in which you can rely on capacitors, first all there is something called the “breakdown voltage“, which is the limit of voltage you can apply to the capacitor before the current starts forcing its way through (and thus damaging) the dielectric. The amount of voltage you can safely apply to a capacitor is the limiting factor in how quickly you can charge it to its full capacitance. There is also a “leakage current“, which is the rate at which the capacitor looses energy, due to the dielectric having a very small amount of electrical conductivity.
The advantages of all this over batteries is that you can charge up a capacitor much more quickly than an electrochemical battery due to there being no chemical reaction to reverse, and there is no limit to the number of times you can charge and discharge a capacitor. The latter point is great because you have a much more durable storage system and you don’t have to worry about disposing of toxic chemical batteries.
The next generation
Now, I can hear you saying wouldn’t it great if we could have a capacitor that could store as much energy as a Lithium Ion battery, in the same size package? Well, funny you should say that, because a patent as been filed by a company called EEStor for something called a Super Capacitor that has a huge capacity, huge breakdown voltage, and twice the energy density of Lithium Ion technology.
An EeStor Cell
The patent that Eestor has filed details a device with a capacity of 31 Farads (remember before we were talking in millionths of a Farad?), with a breakdown voltage of 3,500 Volts (and it could even tolerate up to 5,000 volts). The amount energy this device can store is around the 52KWh (187 Mega Joules), with a volume of around 33 Litres, this has an energy density of around 1 Mega Joule per cubic metre, which is about double that of Lithium Ion. You could charge this thing at 3.5MV 3.5KV in around 5 minutes! While Lithium Ion batteries slowly discharge themselves at around 5% a month, according to EEStor, the super capacitors will only discharge at 0.1% per month.
The Tesla Roadster
Just to give you some sense of scale of this, consider the first commercial electric car that is currently being made, the Tesla Roadster. Currently, its Li Ion battery can be charged with 53KWh of energy in 3.5 hours at 375 volts, and has a range of 250 miles. With a super capacitor, it could be charged in 5 minutes and go twice as far.
What’s more, EEStor claim to have taken one of the super capacitor units (a small subsection of the 52KWh model), and performed one million charge/discharge cycles, then tested the unit’s performance – No degradation!
Potential uses
Of course, when we are all charging our electric cars at home in the future, we are not going to have megavolt power supplies. Although the idea is that these super capacitors could be used as energy buffers. You slowly charge up a super capacitor in your home, over night while the electricity is cheap. Then in the morning, you can zap all the power from your home capacitor into your car’s capacitor. This will really help power companies smooth out the power demands.
Energy buffers won’t just be useful for homes, think about renewable energy sources like wind power or solar. This could be an efficient way to store energy which is coming in at unpredictable times and amounts too. Come to think of it, attach solar panels to your house and they could top up your home capacitor during the day!
As I mentioned above homes won’t be equipped to charge these large capacitors in super fast time, and will instead have to slowly trickle charge on their domestic supplies. Although I imagine we’ll have the electrical equivalent of petrol stations, equipped with high voltage supplies to zap power into our car capacitors as quickly as possible.
Other interesting features of this technology is that it has been designed to be mass producible and scalable, based on integrated circuit technology. This means that the same technology can make up much smaller energy storage devices to power our mobile phones and laptops, etc. . This is where things get fun because these sorts of devices do operate on domestic voltages. Think about it we could get two to three times as much life span out of a charge on our mobile phone or laptop, but have a full recharge in 5 seconds!
Plausibility
From what I have read, there are some good reasons to think that this is not some sort of grandiose wishful thinking. Firstly, Kleiner Perkins Caufield & Byers have put venture capitol into this. This is the same company who first funded Amazon and Google. EEStor has signed a contract with Loáckheed-Martin for military and homeland security uses. Also, the material they are using as their dielectric (based on Barium Titanate) is in the same group of materials that other researchers are researching into for the same goal.
This blog post has been based on information I have gathered from episode 117 of Security Now and the Wikipedia article for EEStor.
We’re talking about Quantum Physics today, and how one of the most difficult to understand concepts is made twice as confusing as is necessary by one of the most poular popular-science gedankenexperiments (that’s German for “thought experiment”). If you don’t know about Schrödinger’s Cat, then this post probably isn’t for you. Although if you are a fan of physics or popular science (for which I applaud you), then read on.
Firstly, I’m going to outline what the “Schrödinger’s Cat” gedankenexperiment is actually meant to demonstrate, then once we understand that, I’ll look at what’s wrong with how the gedankenexperiment is presented to the public.
The weirdness of elementary quantum theory
In quantum mechanics, we find that particles (which are on the quantum-size scale) seem to be able to be in two places at once (position being just one example). Certainly this is WEIRD and counter intuitive. Don’t feel dim for wondering how this can possibly happen, never feel dim. In fact, everyone from the physicists who came up with all this, to the best minds we have today, still don’t understand the mechanism by which this happens.
The important thing to keep in mind, and to some this may be intellectually unfullfilling, is that as scientists we come up with a theory and then check to see that it agrees with nature (i.e. experimental observations). We can never truly know if our theories are telling the real truth about nature, all we can know is that our theories describe the behaviour of nature, within the limits of our technology and ability to test that theory.
In quantum mechanics we have a terminology, in which we say a particle is in a “superposition of states”. This simply means that we think of the particle having more than one physical state superimposed upon it. This could be more than one position, or more than one energy, etc. Again, this is strange, weird, counter-intuitive. However, we find that we must accept it, because there are experiments that test for this very behaviour and they all come back positive. I’d love to explain the experiments, but then this post would end up being three times as long as intended!
What causes this superposition of states to collapse into a single state is interaction with another physical object (whether it be another particle or some measurement apparatus, it’s all the same). Therefore, a particle in a superposition of states could spontaneously collapse due to collision with a cosmic ray, or it could be collapsed purposefully by someone interacting with it, by means of measurement.
The many flaws of the Schrödinger’s Cat gedankenexperiment
Before I continue, I am going to assume you are familiar with Schrödinger’s Cat. If you are not, please read this.
In the simplest of terms, the objective of the Schrödinger’s Cat gedankenexperiment is to demonstrate two things to the lay person:
That quantum systems can exist in a superposition of states.
That measurement of a quantum system actually changes the system.
However, it is my opinion that the Schrödinger’s Cat gedankenexperiment only serves to confuse an already abstract and confusing concept, all the while distracting and misdirecting your attention with the plight of a cute kitty!
In my opinion, the following is all that is wrong with the the Schrödinger’s Cat gedankenexperiment:
Leads the reader to think that the act of measurement is more meaningful than it really is.
Some people create the impression that the act of measuring, i.e. looking at, a quantum system is somehow a profound act, and that only by measurement can a superposition of states be collapsed. The reality is that measurement is simply introducing an external system to the object of our interest. Just because something is being introduced for means of measurement does not give it any special status in the theory. A photon emitted from a laser for purposes of measurement is no different than a photon of daylight. In the the Schrödinger’s Cat example, by opening the box and observing the contents we are lead to believe that simply looking into the box causes the superposition to collapse. Not at all! If anything, it is the daylight flooding in, interacting with the radioactive sample, that causes the collapse. Although, the sample could have already been forced to decay, or not, by cosmic rays entering the box, or infra-red photons (from the cat’s body heat), before we opened it!
Misleads the reader into thinking that an effect only observed at the quantum level can apply to a macroscopic object, such as a living creature.
To the casual reader/listener, there is a very firm impression given that cat is alive and dead at the same time; this is an unforgivable error when trying to educate people about such an important subject. Such large, complex, objects cannot, exist in a superposition of states.
I think I shall leave it there now, but it is for these reasons that I would hope a better gedankenexperiment is thought up to educate the public about the strangeness of superposition of quantum states. I have yet to hear any TV/radio science pundit use Schrödinger’s Cat without totally confusing the issue.
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