Tag Archives: The scientific method

Fun Physics Questions: Does time flow in baby steps?

Cosmology, Education, Mathematics, Philosophy, Physics, Science, Time, , , , , , , , , , , , ,

Question: is it possible time flows in little steps?

At some small scale, could it be, that time is simply a ‘symptom’ of a sequence of events, or states, that there is no actual time passage ‘between’ those states?

This scenario has interesting implications – it suggests life is a bit like a movie – a series of pictures on a strip of celluloid, or pages in a book, and like a book, while the story may unfold to you at whatever speed you read it, it does not matter how fast you read the story itself still has its own pace.

This doesn’t mean the book has to be pre-written, it can still unfold with utter unpredictability, the book is unfinished if you like – the important point is that we are stuck experiencing the passage of time at a rate determined internally – by the rate of chemical reactions in our brains. The drum beat of those reactions would feel the same no matter how fast or slow they seems to an outside observer. They could even be paused for a few minutes – we could not tell!

Now physicists studying energy balances of sub-atomic particles have seen that energy often seems to come in little chunks (the ‘quanta in’ quantum), and that can imply that time may also be chunky (maybe Planck time?); alas, time chunking has contradictory implications – contradictory to common sense anyway- like infinite energy flux, not to mention infinite speeds, but hey if you can just get your head around some of the workarounds physicists have dreamed up (quantum tunnelling for example) everything’s all right again. I am personally highly suspicious of workarounds, and that is what I think they are!

Anyway, even if you try to get away from quantum weirdness, you get sucked back in – take for example this geometrical example. Consider the relative positions of three point objects (small particles?) moving freely in space: they could, for an instant, line up perfectly, but if your measurement were infinitely accurate, this could only occur for an infinitely small duration so long as the particles are moving. If you try to explain this by saying space is divided up into chunks (like ‘snap to grid’ in MS Powerpoint) you get into geometrical issues that three points cannot always be integer increments apart  (nor even rational increments apart) without breaking the most basic number axioms.

So even if space isn’t chunked, it turns out you can appeal to the uncertainty principle, which handily says you can only measure the position of anything infinitely accurately if you allow its momentum to be anything at all, including infinite – and infinite momentum is exactly what you (temporarily) need if you are bold enough to let time ‘leap’.

So none of these issues with time chunking turn out as solid proofs against the possibility, they just make things more slippery!

Aside: rather than a book, I like to think of our universe as being a bit like a computer program  – I like to think about Pac-man when it plays itself in ‘demo mode’ – in demo mode, used to allure people at the arcade, the computer controls both the ghosts and pac-man. In the computer, a sequence of commands is run in the CPU and the speed of the computer (like the reader of the book) controls the rate at which we ‘see’ the ghost-chase on the screen, but this speed is invisible to pac-man himself – yes the ghosts chase faster across the screen, but he can run faster too.

[youtube=http://www.youtube.com/watch?v=htl_vwkZWHw&NR=1]

Question: Does a time-increment universe allow time travel?

Well I don’t think we can ‘skip’ events out (we have to experience them all), but if we can go somewhere where events are more or less ‘dense’, maybe we can. We will not feel the difference, we will not get any extra life-span, our cells will age just the same – but if a friend had gone to another place is space-time, where events have bigger gaps, he may have aged at a different rate, and when you meet your friend again one of you will have time travelled forward and the other backward relative to one another.

Is this really possible? Well, yes, I think so – this model ties in very well with relativistic time travel: if you assume events are more spaced out (less dense, with bigger ‘leaps’ between them) in areas with more mass nearby. or when moving vary fast, it maps perfectly.

Conclusion

That’s it for now! Of course, maybe time does not leap, I don’t know, but its something I love to think about! Please let me know your thoughts…

Confirmation bias: confirmed as bias.

Atheism, Education, Psychology, Science, Science communication, Skepticism, The scientific method, , , , , , , , ,

I have this theory that ‘confirmation bias’ is a load of BS, so I looked on the net and found, after careful search, some people who clearly agree with me. Most don’t, but they must be idiots.

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Reality: a hard sell

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I can’t help but wonder if doggedly debunking all spewings from the purveyors of woo is somewhat a fool’s errand.

There are a number of pseudo-scientific disciplines whose concepts are inherently highly attractive and contagious to the average Joe, saying things that make him feel good and making him want to pass on the good news. Think of how easy to sell these messages are:

  • organic food – frolicking chickens, steaming compost, happy farmers, healthy food – a return to basics, back to a purer time when humans actually had roots in the earth and cared for it; you too can go organic!
  • complimentary medicine – age-old wisdom, so long suppressed by big pharma is unlocked just for those open-minded enough to look. Are you open-minded! Yes? Here are your keys to healthy prosperity!
  • astrology – our fates, entwined with the universe, form a beautiful unity; enigmatic scholars have acted custodian to its cipher through the ages. Are you a spiritual soul? You too can share time’s secrets!
  • parapsychology – our minds are more powerful than science knows, and we all have potential beyond our wildest dreams! But hold on! Only those willing to break free from the trappings of conventional science will ever see the light…
  • and of course the big kahuna, religion – imagine for a minute the greatest most wonderful thing in all the world, and that is but nothing compared with the joys that await the believer, and for all eternity too!

It is little wonder the bible I had as a kid said “Good News” on the cover.

The issue is that the logical shredding of these pieces is often a sobering dose of reality that fills most people with instant sleepiness:

  • organic food is not always kinder to the planet and claimed health benefits are of the ‘hard to verify’ sort
  • alternative medicine actually does work, but only the level one would expect from getting time, care, attention and the placebo effect
  • the laws of physics do allow marvellous things (x-rays, computers, holograms) but it takes serious study to understand why they don’t allow for the positions of stars and planets to have predictable effects of the day-to-day ongoings in suburbia.
  • the mind is indeed fabulously clever and poorly understood, but those tedious laws of physics, and indeed dry, cold logic, are annoyingly sticky when it comes to clairvoyance, ESP, psychokinesis and precognition.

So YAWN! Boring!! Logic and analysis mean effort, work, thinking things through, totting up totals, cross-checking claims, testing, questioning and doubting. Pretty much the opposite of nice & easy. Accepting we are not all-powerful, we are not immortal and that we will all be forgotten someday is just no fun. These are not messages that will go viral, that will breed missionaries, that would generate a manic fervour. More like manic depression.

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So the deck is stacked. Pseudo-scientific ideas persist because they are tenacious memes, and they are almost impossible to kill. They are contagious and sticky, and lovely and easy, and fighting them off requires not just the will, but also the ammunition.

And that is why it worthwhile to continue to fight the good fight – to keep trying to debunk poor thinking – to provide the ammunition to that small number, those that may be on their own, surrounded by superstition, but with that gift in their heart that is that first inkling of doubt.

I will do it for those that think they are alone as I once did.

We live in a time of unprecedented opportunity – people have better access than ever to the tools to arm themselves to achieve a new sort of ideal: to make life choices with full access to all the facts. We are after all free to choose to believe anything, the problem only comes when we are not given the choice. No information, no balance, no choice.

Hysteresis Explained

Education, Environment, Science, Science communication, The scientific method, Things Explained, Time, , , , , , , , , ,

Hysteresis (hiss-ter-ee-sis). Lovely word. But what on earth does it mean?

Hysteresis is one of those typically jargonny words used by scientists that instantly renders the entire sentence if not lecture lost on its audience. Sure, you can look it up on wikipedia, but you may die of boredom before you get to the point, so I am going to explain it here.

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Hysteresis on the way to school

Let’s go for a walk. Let’s say we are ten years old and we are walking to school. The route is simple. The school is a few hundred yards down the hill on the other side of the road. Now consider the question: at what stage do we cross the road? Immediately? Or do we walk all the way to opposite the school before crossing – or somewhere between?

Assuming there are no ‘official’ crossing points, I bet you cross immediately, then walk down the far side of the road.

How can I make this prediction? Well, I assume that crossing the road requires there to be no traffic, so if there is no traffic as you start the journey, it is a good time to cross. If there is traffic, you just start walking down the road until a gap appears, then you cross. This strategy allows you to cross without losing any time. If your strategy had been to cross at the school there is a real risk you will need to wait, thus losing time. So it turns out the best strategy to avoid any waiting is to cross as soon as you can.

So now picture your walk home. Again, it makes sense to cross early on. The result is that the best route to school is not the same as the best route from school. This is an example of hysteresis – or a ‘path dependent phenomena’.

Hysteresis  everywhere

The dictionary will drone on about magnetism and capacitance and imaginary numbers. A much nicer example is melting and freezing of materials – some substances actually melt and freeze at different temperatures. This shows that the answer to the question: “is X a solid at temperature Y?” actually depends – on the path taken to that temperature. Just like what side of the road you are halfway between home and school will depend on whether you are coming or going.

It seems to me that falling asleep and waking up also bear some of the hallmarks of hysteresis; although they could be considered a simple state change in opposite directions, they feel very different to me – I  seem to drift to sleep, but tend to wake to alertness rather suddenly.

Now think of a golf club in mid swing. As the golfer swings, the head of the club lags behind the shaft. If the golfer where to swing in reverse, the club head would lag in the other direction – thus, you can  tell the direction of movement from a still photograph. We can therefore say the shape of a golf club exhibits hysteresis – and again you see see why it is so-called “path dependent”.

This logic can be taken further still – wetting is not the opposite of drying and likewise heating is rarely the inverse of of cooling. Let’s imagine for example that you want to make a chicken pie warm on the inside and cool on the outside. This is best done by warming the whole pie and then letting it cool a little. The temperature ‘profile’ inside your pie thus depends not only on the recent temperature but has a complex relationship with its more distant temperature history. This particular point is somewhat salient at the moment as we ask the question: is the earth heating up? 

So what?

Good question. I’m not a fan of jargon, and hysteresis is not a word I hope to need to use in my smalltalk. However, you can see that it encapsulates a rather specific and increasingly important concept that is pretty hard to replace with two or three simpler words; thus it passes my test of “words a scientist should understand that most don’t”. Please let me know your own additions to such a list!

 

 

Will art, the talent for emotional manipulation, be overtaken by science?

Art, Philosophy, Science, , , , , , , , ,

There is something in our makeup that makes us appreciate hard work. When we admire the pyramids at Giza, or the fine chinese lacquerware, we can imagine the effort that must have been involved. Not just the muscle – but the discipline – lifetimes of work.

When I was a teenager, I spent many hours drawing – and I got pretty good but at some point, I think I was 19, I just stopped. Why? I think I looked at my creations and compared them with photographs and found them wanting. What was the point of photo-realistic drawing in a world full of cameras? It occurred to me that of course I was still impressed with work like that of Chuck Close, but I could not understand why. Not only does he bring realism to it’s logical extreme, but then he takes to tricks like using how our eyes merge small dots to compose images. Why is this trickery impressive? It goes beyond realism, it impresses us with it’s cleverness, rather than it content – the content becomes pretty much irrelevant.

So we are impressed not only by the evidence of labour, but of cleverness. However, when I think about what I achieve in life, I do not want to be known for simply being hard working, or clever, but rather for what I actually achieve. Simply drawing well demonstrates an ability, but unless that ability is then applied to important work: protecting the environment, mitigating injustice, that sort of thing, or at least to inspire others to do so, it could be considered pure vanity.

So I gave up on drawing. I am a bit older now and have come to re-evaluate this position with the benefit of a few more years.

One thing I have learnt (from my closest family who turned out, as luck would have it, to be talented artists) is that there is more to art than my painfully logical mind wants to admit. I can obviously not explain art in a nutshell – besides, like so many things worth knowing one really needs to find this out for oneself.

What I want to focus on here, as usual, is the scientific approach to art, and to start I will make a controversial claim…

Art taps into instincts, and does not understand itself.

Think of a beautiful singing voice. It is clearly possible to play the heartstrings with the right voice. Even if the song were written by someone else, one would struggle to argue that the songwriter or singer can explain why the song plays the heartstrings. I venture that this is similarly true for beauty.

On the other hand, the field of science progressing fastest of late is the study of the human mind. We are only just starting to understand its complex mechanisms, and if a good neuroscientist is happy to admit we are scratching the surface, then it is probably fair to say the poet is playing the instrument of the mind the way most people use a computer – without a full understanding of its workings.

Without insight into the workings of a system, the poet is reduced to trial and error, treating the mind like a black box, poking it and prodding it and seeing the response. While this type of analysis has revealed much about the mind, it is necessarily lacking and frequently runs into inconsistencies that cannot be explained.

As our ancestors have interacted for millennia, we have developed very strong insights for how the mind works and instincts about how to manipulate it; science is still playing catch-up to what every mother, every teenager or anyone with heartache already knows.

However, we are now rapidly approaching the stage when science will start to ‘have an opinion’ about the merit of Shakespeare or Puccini – observing in vivid detail how stories or melodies act to create virtuous cascades in the mind.

So if this analysis is fair, what are the implications? Does it render the arts any less valuable? No, let me explain.

The analysis suggests that the arts are the field of emotional manipulation, developed as an emergent* ability, a field that has been inaccessible to the sciences due to the complexity of the mind – but will not remain so. The arts pull on thousands of years of learning about the human mind, what impresses, what inspires, what angers and what calms. These learnings will not be rendered invalid, they will simply be explained.

Perhaps the artist in you is reviled by this possibility, perhaps the opposite – the emotions will still be real and we will be able to drive them all the better.

I personally suspect there is merit in the vagueness of art. Some of my favourite songs seem to lose their appeal when I finally learn all the lyrics and find them more mundane than I had imagined.

Perhaps the arts can just ignore the march of science?

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Footnotes:

*Emergence is the phenomena of complexity (such as the arts) developing as a side effect of simpler lower order phenomena (emotional stimulus & response). It implies the higher order phenomena was not designed, is not deliberate and therefore cannot credit anyone (or itself) for its merits.

Stuff I Wish I Had Read When I Was Younger

Economics, Education, Evolution, Mathematics, Philosophy, Psychology, Science, Science communication, Skepticism, The scientific method, , , , , , , , , , , , , , , , , , , , , , , , , , ,

Over the years I have supervised and mentored several PhD students, and recently our firm started to award scholarships to undergrads, and I was asked to support one such scholar. These scholars are from the best and brightest and so I got to thinking…

Graduates today have it tough, competition is tough, people work longer and harder than ever and stress is hitting us earlier and earlier in life – or so it seems. I would argue that, to some real extent, things have always been getting worse, and therefore by induction, we can prove that they have haven’t really changed at all.

No, the graduates of today have unparalleled opportunity to learn, to travel and to experience. The brightest graduates have the world at their feet and will be its commanders when we are are all retired and done for.

So what could I do to support this scholar? In the end it was easy – I asked myself – what do I know now that I wish I had known sooner? Most of this is in attitudes and is deep in my psychology, and is the result of direct experience – but it turns out that a healthy chunk of my scientific learning experience can be re-lived – by reading some of the books I think steered my course.

So I made a point to summarize some of the best science related books I have read (and some of the most useful internet resources I have found), and dumped the list complete with hyper-links in an email to the scholar. I hope she goes on to be president!

Now having gone to the effort, it would be a crime to keep this email secret, so here it is, (almost) verbatim!

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As promised, here is a list of useful resources I wish I had known about when I was an undergrad. I am glad I got round to this, it should be useful for several other students I work with, and has also led to me revisiting a few things! I think I may brush it up and pop in on my blog if you don’t mind…obviously I won’t mention you!
Anyway, back to the business. To me, science is not all about chemistry, molecules, atoms, valence electrons and so on. To me, is is the process of trying to understand the world, and this set of materials I have hand picked, should you get through even a part of it, will not only educate but inspire.

This may not be the very best list, and I am sure there are many great books I have not read, but I have stuck with ones that I have, so you will have to rely on other people for further recommendations.

Jarrod’s reading list: science/psychology/economics & so on

  • I’ll start with something really easy, relevant and engaging – an excellent (if quirky) summary of material science: The New Science of Strong Materials – Prof Gordon  has written another on Structures that is also worth reading.
  • Ok, this next one is not a book, but a paper; I like it because it shows that many stuffy professors are wrong when they prescribe boring scientific prose for papers. This paper uses the criminal “us” and “we” and discusses subjects as if with a friend. Shocking form, especially for a junior scientist. This paper by an unknown, changed the world.
  • “Guns, Germs and Steel” – this is large-scale scientific thinking at its best- the book looks at how we can explain why the world is the way it is (especially the inequality) by looking at how technology spreads through societies.
  • “Mistakes were made…but not by me” – this is required reading if you want to work with other people, so its basically for everyone then…
  • Then to take it to the next level – “How the mind works…” – Stephen Pinker‘s other books are also good if you like this one.
  • “Flatland”, (full text here) was written in 1884, and is essential reading because it defines the cliche “thinking outside of the box”.
  • To make your upcoming economics courses more interesting, first read this easy-to-read popular book: “The Undercover Economist“.
  • Also, Freakonomics– it’s shameless self promotion by egotistical authors, but hell they are smart, so put up with it.
  • The Tipping Point –  Malcolm Gladwell is a current thinker I really like; he’s not satisfied to focus on one thing for very long – his other books are on totally different stuff, but are equally thought provoking.
  • “The selfish gene” – Obviously I would firstly recommend “On the Origin of Species”, (full text here) but if you are short of time (which you should be as an undergrad), you can learn most of the basics, and also get updated (well up to the 1970’s at any rate) by reading Dawkins’ classic.
  • I couldn’t ignore statistics, so I will include two – one classic, “How to Lie with Statistics”  and a more modern one “Reckoning with Risk“, they are quite different, but either will get the important points across.

Alas, books are perhaps becoming obsolete, so I better include some other media:-

  • The first one is so good I can’t believe its free – try watch at least one a week, but the odd binge is essential too. http://www.ted.com/
  • Next, an excellent physics recap (or primer) – but  you need lots of time (or a long commute!) to get through this lot – look on the left menu for Podacts/Webcasts on this webpage: http://muller.lbl.gov/teaching/physics10/pffp.html – I cannot begin to praise the worthwhileness of this enough. It used to be called “Physics for future presidents” because it teaches you enough to understand the risks of nuclear energy, and the likelihood that we will all run our cars on water – and let you know when you are being duped or dazzled by big words.
  • When I was somewhat younger there was a TV show called Cosmos, hosted by Carl Sagan, you may know of it. You could watch in now here, though obviously it is dated, so perhaps you shouldn’t; the reason I mention it, is because it was key in creating a generation of scientists, people who were inspired by Carl to be inspired by the universe. The previous generation had the space race and the moon landings to inspire them, but since then science has been on a downhill, with 3-mile island, global warming, etc, etc, and we have had no more Carl Sagans to cheer for us; Cosmos was a rare bit of resistance in the decline of the importance of science in society. You may also know that there have been battles in society (well in the circles on intelligentsia at any rate) about science – on the one had the ‘two cultures debate‘ and more recently, the ‘anti-science’ movement (suggested in books like “The Republican War on Science“. I do not wish to indoctrinate you, but rather make you aware that being a scientist used to be cooler and used to be more respected and something is indeed rotten in the state of Denmark.
  • Getting back on track, here is an excellent guide to critical thinking (something else sadly lacking in the world) – don’t read it, listen to the podcast versions (also on itunes):
    “A Magical Journey through the Land of Logical Fallacies” – Part 1 and Part 2
    I think this should be taught in school. Brian Dunning’s other Skeptoid podcasts put these lessons into practice showing how a scientific approach can debunk an awful lot of the nonsense that is out there (alternative medicine, water dowsers, fortune tellers, ghost hunters, etc etc).
  • If you do happen to have any time left, which I doubt, there are several other podcasts on critical thinking – that use a scientific approach to look at the world and current affairs: –

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Postscipt – Dear readers, please feel free to append your own recommendations to my letter in the comments section below. If there is one thing I know well, and that’s how little I know. I feel I only started to read ‘the good stuff’ far too late in life, and so those with more years than me (or better mentors), please do share. But bear in mind, this is principally a science oriented list, and is meant to be accessible to undergraduates – I left out books like Principia Mathematica (Newton) because it is really rather unreadable – and the Princeton Science Library (though awesome) is probably a bit too intense. Also, in the 30 minutes since I sent the email, I have already thought of several others I sort of, well, forgot:

That’s it for now…

What exactly is temperature? Ever wondered?

Education, Environment, Physics, Science, Science communication, The scientific method, Things Explained, , , , , , , , ,

We take it for granted. We understand it. It is obvious what temperature is. Cold, warm, hot…obvious.

But how many of us have asked the next question: what is the real difference between a hot stone and a cold one? The answer is interesting and helps us to realise that measuring temperature is much trickier than we tend to suppose.

Over many hundreds of years, many clever people have devised lots of experiments to understand what temperature is, I hope in this article to round up the facts!

Temperature and Energy

For much of history, there were only a few sources of heat – the sun, fire, lava and of course the warmth of living creatures.

People were puzzled by what created it, but it was immediately obvious that it had one consistency – whenever it had the chance, it flowed – put something hot next to something cold, and the heat would flow.

Of course you could argue that it was the ‘cold’ that flowed (the other way), but there were no obvious sources of ‘cold’. While ice was clearly cold, it was not a sustainable ‘source’ of cold the way a fire was.

It was also noted that heat melted things – like fat or butter and that it make some liquids (like molasses) thinner. It could even boil water and make it ‘vanish’. The mechanisms for these were unknown and a source of fascination for early scientists.

Early experimenters noticed that gases would increase in volume upon heating, and that compressing gases would cause them to heat up. They also investigated other sources of heat, like friction, (rubbing your hands together).

It was the work with gas that led to the big breakthrough. Boyle and Hooke, as well as Edme Marriotte, working in the 17th century, realized that the temperature of a gas would increase consistently with pressure, and like-wise, decrease consistently with pressure. This sounds unremarkable, until you note that you can only decrease pressure so much…

Once you have a vacuum (no pressure), you should have ‘no temperature’. Thus their observations implied that there really was a limit to how cold things could get, and predicted it was around -275 Celsius. They were of course unable to cool anything that far simply by expanding it because heat always flows into cold things, so to achieve this you need much better insulation than they had available.

So they had a big clue in the search to understand what temperature is, but still no explanation.

It took until 1738 until another great scientist moved us forward. Daniel Bernoulli realised you could use Newton’s (relatively new) laws to derive Boyle’s temperature-pressure relationship. He basically asked: what if gas was made of a large number of very small billiard balls flying around crashing into everything? What if pressure was just the result of all these collisions? Using this theory he realised, for the first time I think, what temperature truly is.

Source: Wikimedia Commons

It turns out that his model equated temperature with the speed of the billiard balls. A hot gas only differs from a cold gas in the speed of the molecules flying around. Faster molecules crash with more momentum and thus impart more pressure. Squashing the gas into a smaller volume does not give them more speed, but means more collisions each second, so higher pressure.

This is a pretty serious finding. It basically says ‘there is no such thing as temperature’. There is only lots of little balls flying around, and their number and speed dictate the pressure they exert, and there is no ‘temperature’.

If we put a thermometer into the gas, what is it detecting then? Great question.

It turns out that solids are also made of lots of balls, except, instead of being free to fly around, they are trapped in a matrix. When a solid is exposed to a hot gas,  it is bombarded by fast flying atoms. When a solid atom is hit, instead of flying off, it starts to vibrate, like a ball constrained by a network of springs.

So the ‘temperature of a solid is also a measure of speed of motion, but rather than linear speed it’s a measure of the speed of vibration. This makes a lot of sense – as the solid gets hotter, the balls are going literally ‘ballistic’ and eventually have enough speed to break the shackles of the matrix (aka melting).

Source: Wikimedia Commons

So this model of heat as ‘movement’ not only explains how gases exert pressure, but also explains how heat flows (through molecular collisions) and why things melt or vaporise.

More importantly, it shows that temperature is really just a symptom of another, more familiar, sort of energy – movement (or kinetic) energy.

Energy is a whole story of its own, but we can see now how energy and temperature relate – and how we can use energy to make things hot and cold.

Making Things Hot

There are many easy ways to make things hot. Electricity is a very convenient tool for heating – it turns out that when electric current flows, the torrent of electrons cannot help but buffet the atoms in the wire, and as they are not free to fly away, they just vibrate ever faster, ‘heating’ up.

Another way to heat things is with fire. Fire is just a chemical reaction – many types of molecules (like methane, or alcohol) contain a lot of ‘tension’, that is to say, they are like loaded springs just waiting to go off. Other molecules (often oxygen)  hold the ‘key’ to unlocking the spring, and when the springs go off, as you can imagine, it is like a room full of mousetraps and ping-pong balls – and all that motion – means heat.

[youtube=http://www.youtube.com/watch?v=Pmy5fivI_4U]

Making Things Cold

Manipulating energy flows to make things cold is much trickier.

One way it to just put the thing you want to cool in a cold environment – like the north pole. But what if you want to make something colder than its surroundings?

Well there is a way. We learned earlier that gases  get hot when compressed – it turns out they do the opposite when decompressed or ‘vented’. This is the principle that makes the spray from aerosol cans (deodorant, lighter fluid, etc) cold. So how can we use this? First we use a compressor to compress a gas (most any gas will do); in the process it will warm up, then you let it cool down by contacting it with ambient air (through a long thin copper tube, but keeping it compressed), then decompress it again – hey presto, it is cold! Pump this cold gas through another copper tube, inside a box, and it will cool the air in the box – and hey presto, you have a refrigerator.

Measuring Temperature

Before we had thermometers, temperature was generally estimated by touch.

However this is where temperature gets tricky. Because the temperature we feel, when we put our hand on the roof of a car is not really the temperature of the car, it’s really the measure of energy flow (into our hand), which relates to the temperature, but also relates to the conductivity of the car.

This is why hot metal feels hotter than hot wood, why cold metal feels colder than cold wood – the metal, if at a different temperature to your hand, is able to move more heat into you (or take more heat away) faster than wood can. Thus our sense of temperature is easily fooled.

The ‘wind-chill factor’ is another way we are fooled – we generally walk around with cloths on, and even without clothes we have some body hair – therefore, we usually carry a thin layer of air around with us that is nearly the same temperature as we are. This helps us when it is cold and when it is hot – however, when the wind blows it rips this layer up and supplies fresh air to our skin – making us feel the temperature more than usual. Also, because our skin can be damp, there can be evaporative effects which can actually cool you below the air temperature.

Scientists have long known that we cannot trust ourselves to measure temperature, so over the ages many tricks have been developed – can the object boil water? Can it freeze water? A long list of milestone temperatures was developed and essential knowledge for early scientists – until the development of the lowly thermometer.

It was noted that, like gases, solids and liquids also expand upon heating. This makes intuitive sense if you think of hot molecules as violently vibrating – they push one another away, or at least if the charge  (electric charge is what holds these things together) is spread just a little thinner, adjacent molecules will have slightly weaker bonds.

The expansion of liquids may only be very slight, and if you have a big volume of liquid in a cup, the height in the cup will change only very slightly, but if its in a bottle with a narrow neck, the small extra volume makes a bigger difference to the level. This principle is used in a thermometer – it’s just a bottle with a very narrow and long neck. The bigger the volume and the narrower the neck, the more sensitive the thermometer. Of course the glass also expands, so it is important to calibrate the thermometer – put it in ice water, mark the liquid level – then put it in boiling water and mark the new level. Then divide the distance between these marks into 100 divisions – and hey presto! you have a thermometer calibrated to the centi (hundred) grade (aka Celsius) scale. Now you know where that came from!

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So that is temperature explained in a nutshell.  If you enjoyed this article you may enjoy my related article on energy.

How to prove that space is curved…

Cosmology, Mathematics, Physics, Relativity, Science, The scientific method, Time, , , , , , , , , , , ,

Question: if you lived in flatland (a 2-d world), how could you tell if the land was curved in the third dimension?

Answer: geometry!

It turns out many of the mathematical rules we learned at school ‘fall apart’ if the working surface is curved. For example, can you draw a square on the surface of a sphere? No!

So can we use this insight to tell if our 3-d world is curved in a mysterious fourth dimension? Yes!

If we set off from earth, went in straight line for, say 1 light-year, then turned 90º, went 1 light-year, turned 90º again, and then did this yet again, you should have traced a perfect square, and be back exactly where you started. If you aren’t, something is amiss!

 

Now it turns out that it we do this, we will indeed discover an error; but why? And how do we know this?

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Newton told us that a massive object in motion will continue to travel in a straight line, unless acted upon by external forces. Some people think that Einstein overturned this insight, but he didn’t; indeed he extended it: he said that the force of gravity is not actually a force, and thus objects falling under gravity are actually going in straight lines! Indeed this makes sense, as anyone ‘falling’ does indeed not sense any acceleration, but rather feels ‘weightless’. Thus they are not actually accelerating, they are going straight – in curved space.

Now anyone who has thrown a ball can see this is absurd on the face of it, but Einstein was serious, and he is right, from a certain perspective. The ball is not going in a straight line through ‘regular’ space, but is going on a straight path in a 4-d construct called ‘space-time’. Likewise, he would argue that the planets are tracing straight lines around the sun; and indeed the ‘parabola’ of a baseball is actually not a parabola, but a very small part of the enormous ellipse that would be traced in the baseball could fall though the earth and go into ‘orbit’ §.

Anyway, Einstein’s model says that light travels in straight lines, but we have seen that light bends when it passes near to the sun (this can most easily be tested during an eclipse) – so… if one of the sides of your ‘perfect square’ were to pass near the sun, it would also be bent and if you followed the above rule to draw the square, you would not end up where you started.

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Physicists have grown used to Einstein’s model, and better tests for the flatness of space have been developed. For example, if you drew a circle on the surface of a sphere, the area would not equal Πr2, but would be less. Likewise, in 3-D space, we could plot a sphere and then measure the volume and if it did not equal 4/3Πr3, we would know something was amiss.

So physicists have looked at how light bends, and how the planets move, and found out, amazingly (but predicted by Einstein) that the error in this spherical volume calculation is directly proportional to the mass of matter within the sphere – proving that the warpage in space is proportional to (and thus caused by) ‘mass’.  Thus mass warps space.

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MC Escher: 'Grid'

But is space really warped in some ‘extra’ dimension?

Well, this is a good question. Maybe it is some extra ‘spacial type’ dimension, but you could also look at time as a fourth dimension, and argue that this space is not ‘curved’ at all, but rather that space and time simply vary in density in different locations. I personally like this way of looking at it, it eliminates the need for some vague ‘extra dimension’, and therefore swiftly removes the possibility that space could be ‘closed’ or fold back on itself in this extra spacial dimension. Occam’s razor thus prefers the ‘density’ model!

Footnotes:

§. In Wikipedia, they state that balls bounce in perfect parabolas, but note they also mention a ‘uniform’ gravitation field, and it is well to remember that the earth gravitational field is not uniform, but radial. Thus I stand by my assertion that missiles follow elliptical paths just like planets and comets. Of course, an ellipse is a close relative of both the parabola and the hyperbola, so this is not really that dramatic.

Skeptics vs Deniers

Environment, In the media, Philosophy, Science, Science communication, Skepticism, The scientific method, , , , , , , , , , , , , ,

There is a growing movement, grassroots in nature, but starting to connect, called the skeptics community.

Who exactly are they? Are they people who are starting to uncover the truth – that most world governments are a sham and that secret societies control our every move? Do they deny the holocaust and suspect 9/11 was a complex plot?

No.

A skeptic is merely someone who needs to be convinced of things through reason, rather than one who accepts things on some-one’s say-so.

Simple!

So what is a global warming ‘skeptic’?

Climate science is complex, and consensus opinion is that man’s activity has led to increased greenhouse gas emissions which are likely to reduce outgoing radiation and thus lead to a net shift upward in the temperature of the Earth’s delicate surface. Yes, there are other possible causes, yes, the models contain assumptions, and yes, some fools have fabricated data to look cool. It is also true that many respected scientists will not say it is a cast iron ‘fact’.

So that is the scene – and there seem to be a few types of stakeholders:

  • the ‘global warming denier’
  • the  ‘global warming skeptic’
  • the regular ‘skeptic’
  • and lastly, the gullible!

A ‘global warming denier’ has come to mean someone who does not think the evidence stacks up enough to warrant concern, or worse, thinks it is all a giant conspiracy.

A ‘global warming skeptic’ has come to be somewhat synonymous with a denier, but perhaps without the conspiracy angle. However, many are just people who are on the fence – they are often very smart, and don’t just believe what they are told, but on the other hand, they are easily misled, as there is just so much misinformation out there. They may be the ones who say “I heard the jury is out…” rather than actually looking at evidence.

Some legitimate scientists have foolishly allowed themselves to be given this label, just because they debate some small details (like the rate of heating, or the likely nature of socio-political impacts). These scientists are then lumped with deniers. Tough luck to them.

I found this is some random folder on the 'net. If it's yours, please let me know, I love it! Update: it looks like it may well be from thisisindexed.com - click it to link - nice one Jessica Hagy!

Now a true skeptic will weigh all evidence according to the following principles:

  • is it logical?
  • does it conflict with other strong theories? If so, is it strong enough warrant a change to your previous understanding?
  • is there independent corroboration?
  • do the proponents have a  proven track record (credibility)?
  • is there any incentive by stakeholders to twist the facts?

This describes most good scientists, so its not a bad thing.

In the case of global warming, most true skeptics who have looked closely at the evidence and weighed it appropriately, agree that there is real cause for concern.

But yes, we skeptics will always retain just a little doubt, because you just never know…