Perpetual motion won’t stop

We all know you can’t get something for nothing. In particular, everyone knows that the Law of Conservation of Energy means you can’t get free power out of nowhere.

But that doesn’t seem to stop people thinking that law doesn’t apply to them, as every few years someone tries to invent a new perpetual motion machine.

The most notable attempt in recent years was an Irish company called Steorn, who in 2006 published a full page ad in The Economist announcing their discovery, and inviting scientists and engineers to evaluate it. Their invention, called Orbo, uses a clever arrangement of magnets that, so they claim, causes it to keep turning and generating more energy than is put in.

Five years later and, although Steorn is still going, you really have to conclude the proof is in the pudding: if it was real, we’d all be wallowing in free energy.

Beyond that though, it’s very hard to properly evaluate their claims; and not just because you have to pay them a licence fee to get any details. The trouble is that conservation of energy is pretty fundamental to the laws of physics you need to evaluate the theory behind their claims.

As an example, consider the classic overbalanced wheel:

The overbalanced wheel, uses swinging weights around the rim to try and ensure there's always more torque on one side (the right hand), so it keeps turning.

At first glance it looks like it could work: the weights on the right-hand side swing out further, so they exert more torque on the wheel. But if you sit down and calculate the actual forces and torques that apply, you’ll find that the fact there are more weights on the left, they balance it out and the wheel won’t turn.

And of course this is entirely consistent with conservation of energy. The change in an object’s energy due to a force acting on it – called work - is equal to the force multiplied by the distance it acts over.

This means that force, motion and energy are all related, and the laws of dynamics that govern how things behave simply cannot violate conservation of energy.

So our Irish friends, no matter how they try to justify their claims with “magnetic interactions whose efficiency varies as a function of the time frame of the interaction”, are going to find the same thing. Energy conservation is as intrinsic to the laws of electromagnetism as it is to Newton’s laws of motion, gravitation, etc.

Now, it’s entirely possible Steorn are quite sincere in their beliefs, thinking they just have a few engineering problems to solve until they obtain unlimited free energy. But no matter how they try to bend the laws of physics, it’s going to remain impossible.

Sorry to disappoint, but I wouldn’t go holding your breath.

Maybe the multiverse is real in another reality

The idea that there is more than one universe, more than one version of reality, a multiverse if you will, is a very compelling one.

Especially if there are an infinite number of universes: there would have to be others identical – or almost identical – to our own. Somewhere out there could be another you, reading a blog nearly as good as this one.

It’s also an attractive idea for physicists, as it naturally leads to the Anthropic Principle, which is one of the easiest ways to explain why our universe is the way it is – and in particular why it seems to be just right to support intelligent life.

Basically, with an infinite number of possible universes, there has to eventually be one capable of supporting life; and of course, we can only exist in that type of universe.

You can decide yourself whether the Anthropic Principle is a truly satisfying explanation, or just an over-complicated attempt at getting out of explaining anything at all. The question for today is, can we ever know if it’s true?

Normally you’d have to say no: the whole idea of these being separate universes is that they’re, well, completely separate to our own. But there’s one multiverse theory in which each universe exists in a bubble, and if these bubbles were to collide, they’d leave telltale signs.

This from an idea called eternal inflation. Our universe is believed to have gone through a period of extremely rapid inflation early in its life (from around 10⁻³⁶ to 10⁻³² seconds after the Big Bang). This inflation stopped when the universe reached a stable state.

But what if there was more space beyond the boundaries of our universe that didn’t ever reach stability? Our universe would be a bubble within this eternally inflating region; and if there’s one bubble, why not more? And what’s to stop them colliding with our own universe?

To see the signs of these collisions you’d have to see the edge of the universe, which of course is a very long way away. But fortunately at the start of the universe it used to be a lot closer, and we can still see the results of this in the leftover heat from the Big Bang, the Cosmic Microwave Background (CMB).

Full sky map of the cosmic microwave background. The red, green, orange and light blue areas are the areas most likely to be bubble collisions, but even then they're not very likely. The data comes from the Wilkinson Microwave Anisotropy Probe (WMAP).

A team of physicists from University College, London, and elsewhere, have come up with an algorithm for searching the CMB for circular patterns that could be the result of bubble collisions.

So, did they find any? Well, there were a few possibilities (see the image above), but they weren’t really significant enough to separate from random noise. The best they could really do is put an upper limit on how many collisions there are (less than 1.6, at 68% confidence).

Of course, no paper is complete without saying that further data will help their chances of finding something in future. But still: it’s pretty amazing to think that other universes could collide with our own, and we could detect them. You just wouldn’t want to be standing there when it happens.

And also, it’s worth pointing out that even if no other bubble universes ever collided with our own, that doesn’t mean they’re not out there somewhere. After all, the eternally inflating multiverse has to be pretty big.

Read more about this study in the recently published papers, Feeney SM, Johnson MC, Mortlock DJ & Peiris HV 2011, “First observational tests of eternal inflation”, Physical Review Letters 107, 071301 and Feeney SM, Johnson MC, Mortlock DJ & Peiris HV 2011, “First observational tests of eternal inflation: analysis methods and WMAP 7-year results”, Physical Review D 84, 043507.

Or, read a take-down of the media hype around this study – i.e., all the news articles claiming they did find something - on the blog Not Even Wrong.

Static cling is a wrap

So, how does cling wrap cling? Is it just sticky, or does it have something to do with static electricity?

The answer is yes and no. Yes it really is sticky, and no, it’s mostly not static electricity – but also yes it is a little bit.

First, the stickiness. Plastic wrap is usually made from something like polyvinyl chloride (PVC) or low density polyethylene (LDPE), to which they often add LLDPE as well (that’d be linear low density polyethylene).

These substances are naturally clingy without static electricity (LDPE less so, but the LLDPE helps). Static electricity is, after all, an electrical charge that’s usually built up by rubbing two non-conducting materials, or insulators, together. Like rubbing your feet on the carpet, or rubbing a balloon against your hair.

The usual explanation for what’s happening here is that by rubbing the materials together you’re transferring electrons from one to the other – so one piece is positively charged, the other negative.

(Incidentally, this is where electricity gets its name: the ancient Greeks discovered they could charge rods of amber by rubbing them with fur, and so in 1600 when the English scientist William Gilbert did his own experiments he named it after the Greek word for amber, ήλεκτρον, or electron.)

Of course, the thing with plastic wrap is that it can also stick to metal or damp surfaces, which would be expected to conduct away any accumulated static electric charge.

But hang on! If you play with plastic wrap you’ll notice that it doesn’t just cling to surfaces, it also attracts things towards it, just like anything else charged with static electricity. And this is where things get complicated…

Because our plastic wrap has picked up its charge by being pulled off a roll of other plastic wrap. So if the usual explanation for static electricity is right, how was charge transferred between two identical substances? Why would one piece be positive and the other negative?

Thankfully, a recently published paper may give us the answer. Researchers from Northwestern University in Illinois US used Kelvin force microscopy, which is able to measure the amount of charge on a surface, to examine two pieces of similar material that been brought together (Baytekin HT, Patashinski AZ, Branicki M, Baytekin B, Soh S & Grzybowski BA, “The mosaic of surface charge in contact electrification”, Science DOI: 10.1126/science.1201512, published online 23 June 2011).

Charge on the surface with static electricity, at the top, and without, at the bottom (Image from Science)

What they found was that you didn’t get a uniform arrangement where one piece was all positive and the other was all negative. Instead, each surface was covered in a mosaic of both positive and negative charges, in tiny areas less than a micrometre across.

Overall there’s a slight imbalance, so the material behaves as if it’s got a net charge. But the charge density in each of these microscopic regions is much, much higher than you’d expect.

And these charges seem to be caused by chemical reactions taking place on the surface. The materials used in the experiment were similar, but not identical: one contained fluorine, one contained silicon, and when they tested them afterwards, they found that some of the material had been transferred.

So that’s what seems to be going on with our plastic wrap! There is static electricity, but it’s more complicated than the one-way transfer we’re all used to.

And it also shows there’s always something new to learn, even about phenomena we’ve thought we understood for hundreds of years.

Geoengineering as climate change plan B

Clearly, the best way to address climate change caused by greenhouse gas emissions is to stop emitting greenhouse gases. Which is great, except we don’t seem to be very good at that – particularly in terms of getting international cooperation.

So what do we do if it turns out we can’t cut emissions quickly enough to avoid catastrophe? Or to put it another way, science and technology kind of got us into this mess, so can it get us out of it?

Satellite image of fires and deforestation on the Amazon frontier, Rondonia, Brazil, on 12 August 2007. Intact forest is deep green, while cleared areas are tan or light green. Clearing forest like this releases a great amount of carbon dioxide and removes a valuable carbon sink, so why not try and reverse the process? (By Jesse Allen and Robert Simmon of NASA Earth Observatory, via Wikimedia Commons)

What we’re talking about is geoengineering. It may sound far-fetched, or perhaps like a super villain plot, but it’s being given considerable thought by seriously serious bodies like Intergovernmental Panel on Climate Change (IPCC) Expert Meetings and, more locally, a Pilot Workshop on Asian perspectives.

But what exactly is geoengineering? Well, the options analysed in an influential 2009 paper by the UK Royal Society can be split into two categories: carbon dioxide removal and solar radiation management.

In the list below, we rate these options by their predicted effectiveness and craziness – the inverse of the Royal Society’s assessment of affordability, timeliness and safety.

More junk than space

During 3CR’s Radiothon week (it’s not too late – donate now), I was asked a question by our colleagues from Spoken Word: how much space junk is there?

Thanks for asking! And the answer, unsurprisingly, is a lot.

Plot of the roughly 22,000 pieces of space junk large enough to track (> 10 cm). The outer ring is the very useful geostationary orbit, at an altitude of 35,786 km. But the vast majority of objects are in the dense white region further in - this is low Earth orbit, between 160 and 2000 km altitude. (Image by NASA)

Let me be more specific. Like, millions, or even tens of millions of pieces.

Vehicle traffic and fluid flow

Traffic can be difficult to model mathematically, comprising as it does thousands of drivers in metal boxes making their own decisions and moving in a coordinated – or uncoordinated – fashion. But at the risk of over-simplifying things, it can be instructive to treat certain road conditions as a fluid.

Consider bottlenecks, where a blockage reduces multiple lanes of traffic down to one.

Diagram of a road bottleneck: the rate of cars entering the section is the same in both directions, but the reduced flow around the roadworks forces the traffic into one lane, slowing cars to a crawl (Image by Smurrayinchester, via Wikimedia Commons)

In the diagram above, roadworks have forced all the cars from three lanes into one. The restriction of the single lane determines how many cars can pass through the entire section of road in any period of time.

Since cars can’t magically appear or disappear, they must be going into the blockage at the same rate – if you like, we can call this the conservation of cars. But because the three lanes mean there are three times as many cars going in, to satisfy the law of conservation of cars, they must be moving at one third the speed.

This may seem counter-intuitive, after all we normally assume that wider roads make traffic move faster. But you’ve probably observed the effect yourself when you encounter roadworks. It implies that widening roads won’t help if there’s some form of limiting factor, like an exit to a freeway. Adding more lanes to the diagram above will only cut the speed further.

This same principle applies to fluids, except it’s not conservation of cars, it’s more like conservation of mass. And the overall rule is called the continuity principle.

You can easily see the continuity principle in action in your home: for instance, water coming out of a tap accelerates under gravity, so when it’s moving faster the cross-sectional area has to reduce to keep the rate of flow the same. Which is why the stream narrows further from the tap.

Or for another example, when you put your thumb over the end of a hose you restrict the area it can flow through, and so the water moves faster – and you can squirt the water further.

But as a final interesting twist, there is a maximum speed you can reach by reducing the area like this: thanks to Bernouilli’s principle, increasing the speed of flow also reduces the pressure. And eventually the pressure gets so low that the water can actually boil at room temperature.

This is what sets the maximum speed: it’s known as choked flow. And this room temperature boiling, with bubbles of vapour forming and collapsing, is the cause of the characteristic hissing noise of taps.

And that’s what freeway construction and roadblocks have to do with noisy plumbing!

Help, our mass is missing

The universe is not what you think it is. We look out into space and imagine it’s full of worlds like ours, but most of what’s out there is completely different and entirely baffling.

First, the obvious. Those lights you see in the night sky are mostly stars – billions and billions of stars. Our galaxy alone contains about 300 billion of them, and with an estimate of more than 170 billion galaxies in the universe, that makes the total number over 50×10²¹. That’s 50 followed by 21 zeroes, which is an exceptionally big number.

Hubble Ultra Deep Field image, taken in 2004, showing more than 10,000 galaxies looking back about 13 billion years in time, all within a patch of sky less than 1/10 the diameter of the full Moon and that looks empty when seen from Earth (Image: NASA)

The point here is that they far outweigh any planets that may be out there. In our solar system, all the planets, dwarf planets (hello Pluto!), asteroids, comets, etc. make up only about 0.14% of the mass – the remaining 99.86% is the Sun.

But although stars are pretty much all we can see, there’s plenty more out there that we can’t see. And recently, two separate teams of Australian researchers have shed some light on what this missing mass may be.

Why is it so?

Those who are older than, say, 30, should remember the great Professor Julius Sumner Miller.

The late, great, Professor Julius Sumner Miller, as seen in the heyday of black and white TV (photo: ABC)

A real professor – actually a physicist who studied under Albert Einstein – Julius Sumner Miller demonstrated science to Australian television audiences from 1963 to 1986. Tragically, he died in 1987 at the age of 77 (although, if he had lived, he’d be 102 by now, which would be quite impressive).

But if you’re craving some old-fashioned science communication, you can see some clips of his program Why is it so? on the ABC website, at www.abc.net.au/science/features/whyisitso.

Or, if you must, you can watch a certain chocolate commercial featuring an egg and a milk bottle.

And in the tradition of encouraging the enquiring of minds, here’s a conundrum from his book of “Millergrams”, also called Why is it so?

Take a spring scale. Hang 1000 grams on it: it reads 1000 grams. Now hang 2000 grams on it: it reads 2000 grams. All very simple! Now place this scale on a horizontal platform. Fix strings to its ends. Let these strings pass over pulleys, if you wish, to minimise friction trouble. Now from each end of the scale hang 1000 grams. So now we have 1000 grams pulling to the lef and 1000 grams pulling to the right. We ask: what does the scale now read?

Let me offer you some help! A thousand to the right and a thousand to the left – aha! The scale reads 2000. But wait a minute! Instead of aiding they may be opposing. So it clearly reads zero! What do you think?

A most ingenious paradox: tell me your answer in the comments!

Another 10 beautiful, er… minds

So recently we looked at the top 10 physicists in the world, using a fairly arbitrary but meaningful ranking system. All very impressive, but after seeing the movie Thor the other night, it struck me that there are plenty of worthy physicists in movies and television too.

Natalie Portman as Jane Foster, doing physical research with the god of thunder (played by Chris Hemsworth)

In Thor, Natalie Portman plays Jane Foster, a young physicist who’s doing some sort of research that involves chasing dimensional portals around New Mexico. Which is actually pretty impressive, although maybe not up to the level of Juan Maldacena’s work.

But perhaps you might have noticed that Ms Portman – who, I should point out, is herself a published psychologist – has the edge on Professor Maldacena and many of his colleagues in another way. And interestingly, this is something common to a number of other fictional physicists.

Click through after the jump to see 10 of Jane Foster’s predecessors (presented in chronological order, so I don’t have to choose).

Feel the hotness

We all know about absolute zero, right? You know, the theoretical lowest limit of temperature?

Because of course temperature is really just a measure of the energy of atoms and molecules randomly jiggling around. So absolute zero is when they’ve stopped jiggling and are completely motionless. And since you can’t move slower than stopped, you can’t get lower than absolute zero.

But what about the other direction? Is there a maximum temperature to the universe? An absolute hotness, if you will (and I will)?

Theoretically, yes there is. This mightn’t seem possible, as you’d think the jiggling energy could just keep increasing forever. But as energy increases, it affects the way the fundamental forces of the universe behave.

In particular, there’s an energy at which gravity becomes a purely quantum force. And because gravity is intimately connected with the structure of space-time, the laws of physics as we know them break down and reality itself turns into a sort of quantum foam.

Quantum foam, a lumpy mess of distortions and fluctuations in space-time at the Plank scale

This energy – or the temperature it corresponds to – is known as the Planck temperature, and it’s the theoretical maximum temperature of the universe.

And it’s pretty hot. Roughly about 1.4×10³² Kelvin, or if you prefer, 140 nonillion Kelvin. If you prefer your temperatures in Celsius, it’s still about 1.4×10³² °C (at that level they may as well be the same).

Of course, once we truly understand the quantum nature of gravity, we might find it’s possible to go beyond this temperature. Or it could be that the maximum is at a different level entirely – for more on these possibilities, see the PBS Nova column on Absolute Hot.

And for some more milestones on the temperature scale, click through after the jump.