Tag Archives: physics

The Coolest Film in the World (Still a Better Love Story Than Twilight)

IBM is pretty cool. As part of their ongoing research into data storage based on single atoms, they’ve made the world’s tiniest film. It’s called ‘A Boy and his Atom’.

It uses a handful of carbon atoms (a figurative handful of carbon atoms, obviously). A few dozen individual atoms to create a little stop-motion tale about a boy with a big grin and an atom of his very own.

The IBM film-makers used a scanning tunnelling microscope to move the atoms around and create pictures. (An IBM scientist won the Nobel Prize for Physics for inventing the STM in 1986.) It took the team of scientist film-makers two weeks of 18-hour days. Take a couple of minutes and marvel at how frickin’ awesome science is.

It’s a simple story using phenomenally complex technology. And it’s still a better love story than Twilight.

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May all the forces be with you!

The title of this blog is taken from Book 3: Predicting Motion from my S207: The Physical World OU course book. It made me chuckle.

At the moment, I’m studying forces and pressure, and the line above was in reference to the fact that we don’t implode under the weight of the atmosphere. Normal atmospheric pressure is about 1.013 x 105 Pa, which exerts a force equal in magnitude to the combined weight of 163 people, each of mass 63.5 kg, on a patch of Earth one metre square. That is a LOT of weight.

How are we not crushed? Well, the pressure inside our bodies is approximately equal to the pressure outside, so all the forces just about balance. Which means we are in perfect balance with our normal environments. Simple!

Fictitious forces

So, forces. Everyone knows what a force is, right? The equation is F = ma (force = mass x acceleration). There is frictional force, centripetal force, weight, and the linear restoring force… but what isn’t there?

Fictitious forces are not real forces at all; they are associated with real phenomena that arise when we use non-inertial frames of reference (i.e. frames of reference that move around). Newton’s laws of motion can only be applied in inertial frames of reference. They start to collapse in the face of excitement…

Gravity: No, gravity is not a force. Gravity is a downward acceleration that is, on Earth at least, approximately equal to 9.81 m s-2. That means that any object falling under gravity (assuming that there is no friction or air resistance) falls at a speed which increases at the rate of 9.81 metres per second, every second.

Gravity does, however, give rise to a force: weight. Our everyday use of the word ‘weight’ is not, technically, correct. We use it to mean ‘mass’, which is constant wherever you may be. Weight is a force arising from gravity, described by the equation W = mg (weight = mass x gravity) and it varies depending upon its environment. For example, you weigh more here than you would on the Moon.

Under gravity, objects exert a force (weight) upon the rigid surface on which they rest. The rigid surface exerts a force right back at it, called the normal reaction force. These two forces balance, meaning that the object stays where it’s put, unless it is acted upon by an unbalanced force, such as a good hard kick.

The Coriolis force: This is a weather phenomenon that is actually pretty cool. In the Northern Hemisphere, moving air masses tend to wander off to the right, as if they were being pushed there by a force.

Arising from the Earth’s rotation, this result is not due to an unseen force at all, but is due to the fact that the motion of the air masses is being observed from the non-inertial frame of the spinning Earth.

The air masses are moving in a straight line, as all things are wont to do under their own steam; it is the rotation of the Earth that makes the air appear to veer off to the right in the North. The effect is real enough; the force is an illusion.

Centrifugal force: Everyone who has ever travelled in a fast-moving car, or been on a roller coaster, knows exactly what centrifugal force is. It pushes you out to the side when you go round a sharp bend at speed.

Except it doesn’t. From the frame of reference of the car’s interior, you’re pushed by an outwardly directed ‘centrifugal force’, but this, too, is an illusion. Think outside the box. Or outside the car, if you like.

Unless acted upon by an unbalanced force, all objects in motion will tend to travel in a straight line – even you. Within a car, you will tend to travel in a straight line, regardless of what the car is doing. It is only when your forward motion connects with the side of the car as it’s making the turn that your motion deviates from the straight and narrow. So although it feels as though an unseen force is throwing you to one side, it isn’t. In fact, you are travelling in a straight line until you are no longer able to because the car door is in the way.

Acceleration in a straight line: Another car example. Cars are great for describing and examining forces in physics. When a car accelerates, you get pressed back into the seat by the force of… what? Well, nothing. In an inertial frame of reference, e.g. the one attached to the road, there is no physical force moving you backwards.

The non-inertial reference frame attached to the moving car does have a backward fictitious force though. In fact, the real force is the forward force produced by the car’s engine. When the car accelerates, you carry on moving at the pace you were moving at before, until the solid seat requires you to move along with it.

Put your mind outside the car and observe from there: you’re not subject to any forces that the car is not subject to.

Treating the fictitious forces as real forces within their non-inertial frames of reference allows us to apply Newton’s laws them, which can be kind of useful. It’s important though to remember that they are not real forces. They are nature’s illusions.

S207: the story so far

So far, S207 is fabulous, but very challenging. The maths is extremely tricky for those without a background in maths, so I’m finding it hard going. Challenging is good: it makes it all the more rewarding when I realise I understand something fully. TMA01 netted me 78 per cent, which I’m pretty happy with – plus my tutor’s comments were really helpful. Bring on TMA02!

Things I am struggling with so far:

  • Simple harmonic motion: not so simple
  • Interpreting graphs. I don’t know why; it’s a mental stumbling block

Everything else, I’m taking my time with. The more I do, the more it makes sense. And every now and then I come back to something I was struggling with, and suddenly it makes perfect sense. Which is nice…

S207: Very small, or far away?

Crikey. The largest distance measurable is 1044 times bigger than the smallest distance measurable.

Universe

The observable Universe

That is so far out of our range of understanding, it’s almost meaningless. It’s difficult enough for us to imagine relatively small stellar distances, let alone the numbers we’re talking about here.

The largest distance we can measure is the size of the observable Universe, at 1026m. It’s taken light about 13 billion years to reach us; and that’s just a fraction of the Universe’s actual size *boggle*.

Quark

The quarks making up a proton

The smallest distance we can measure is that of a quark (the bits that make up a proton – two up quarks and a down). A quark is about 10-18m. Again, so small that it’s almost incomprehensible.

Human beings have evolved on a scale that runs from around 10-4m to around 104m (plus a little very recent expanding of our horizons) so that fact that we can measure and understand such tiny and vast distances at all is staggering.

I love the fact that my first foray into S207 has completely blown my mind. I knew these facts anyway, from my study of S104 and from general interested geekiness, but the course has presented it in such a way that I see things differently.

The first multimedia sequence is presented by Jocelyn Bell Burnell, the inspirational British astrophysicist. Born in 1943, she was a real pioneer for science (and for women): as a postgraduate student, she discovered the first radio pulsars with her thesis supervisor, Antony Hewish. Shockingly, her name on the paper publishing the discovery was listed second, and she did not share in the Nobel prize awarded to Hewish for her discovery. She is remarkable.

I’ve dived into S207 a little early to try to get a head start, and the very first paragraph of the very first book made my heart soar! The first words I read were:

“Studying physics will change you as a person. At least it should.”

The authors went on to say:

“We want your exposure to physics to change you, and we want you to be consciously aware of that change.”

It is a joy to learn when the teachers are passionate about their subject, and their aim is to inspire and develop a deep love for the subject in their students. I knew I would love this course anyway, because the subject matter is endlessly fascinating. But now I’m sure I’ll love it because it’s going to be taught in such a way that it makes you approach learning with delight.

Studying physics has changed me already over the past few years. I’m looking forward to it changing me more.

Here AND there; or, brain addling for beginners

This post is going to addle your brain. I make no apologies for this, for it is in the name of science, and knowledge, and enlightenment. Tying your brain in knots is good mental exercise and provides me with a little light entertainment.

You see, I understand this. I do. Well, when I say I understand it, what I mean is that I understand my lack of understanding. But explaining it to others is incredibly difficult, because it requires the suspension of every day common sense, and a lot of people find it very, very difficult to do that. Plus, it requires a new language of the faintly absurd.

Here goes.

Electrons and the double-slit experiment

Electrons are particles. They have mass (1/1836th of a proton) and charge (negative, 1/2 spin). When they are fired out of an electron gun, they arrive one by one as points of light on a screen. The screen is coated with a phosphor that will produce a small burst of light when an electron strikes it. (Incidentally, this is how old-fashioned TVs used to work.)

When electrons are fired at a screen in this way, but a barrier with a double slit cut into it is put in the way, you would expect the pattern on the screen to look like this, right?

Double-slit_expected_result

Common sense tells you to expect this result.

This is where the strangeness of the quantum world begins. The pattern doesn’t look like that.  It looks like this:

double-slit_actual_result

This is the pattern produced by the electrons travelling through the double-slit to the screen.

If you’re familiar with the properties of waves, you’ll recognise this as an interference pattern. When two waves, such as water waves, meet they either reinforce each other, or cancel each other out. What you end up with is something like the above: an interference pattern.

This means that the electrons are somehow interfering with each other as if they were waves. Doesn’t it? Well, no.

Slowing things down

The experiment was slowed right down. One electron at a time was fired from the gun; the point of light was recorded; a short time passed to allow things to settle down; and another electron was fired. And so on.

This is where it becomes really strange: the interference pattern built up gradually. From individual electrons. Whatever is causing the interference pattern does not involve two or more electrons interacting with each other. So what is happening here?

Is the electron passing through both slits at once? In fact, there isn’t any way to know this. We have no idea how the electron is travelling from gun to screen; only that it is, and what the pattern looks like when it gets there.

This is where you need to be able to step out of the ordinary, everyday world of large objects like trees, spoons and elephants, and dive into the quantum world. Suspend your disbelief; leave behind your prejudices and preconceptions (actually, this is good advice for life in general); and open your mind to the world of the natural.

Somehow, each electron is interfering with itself as it passes through the slit(s). As if it were a wave. We need to be very clear: electrons are NOT waves; they are particles. But somehow on their travels from the electron gun to the screen they are behaving like waves. They have wave-like properties.

As each electron travels from the gun to the screen, it spreads out into what I like to call a “probability wave”. It occupies every conceivable path from A to B simultaneously, only “deciding” where it is when it reaches its destination. As the probability wave passes through the double slit, two new waves are formed, which interfere with one another just as any other wave would.

This is why each individual electron produces a random interference pattern. It is impossible to predict exactly where the electron will land on the screen; it could land in any one of an infinite number of places. The overall pattern, however, is predictable as the stripes above.

Addled?

Stretch your mind. Think about this experiment from start to finish: is there any way – any way at all – in which the interference pattern could be produced from single electrons if they behave in an everyday way? (There isn’t, but think about it anyway because once you’ve convinced yourself, it’s easier to accept the crazy.)

Then think a little more about probability waves. It’s mind bending, and completely awesome.

Image

Do you understand the Higgs boson?

Do you understand the Higgs boson?

This post has a nice dual purpose for me. A bit of geek humour, and a bit of a demonstration that infographics are a fab way of putting lots of info into an easily-digested format.

Well, do you?

Higgs made simple(r)

Just a quickie – in my infographics travels, I came across this little gem. It’s a beautiful explanation of the Higgs boson (and the wider particle world). Grit your teeth through the first couple of minutes of very annoying background noise – the graphics that follow are well worth it!

Higgs boson explained

Higgs!

Well, this is incredibly exciting! The scientific community has been searching for this for more than 45 years – and today, CERN has announced the discovery of a new particle consistent with the Higgs boson.

There have been a few premature shouts of excitement in the past couple of years, but an analysis of the data sets shows a level of certainty that allows the teams to announce the new particle. This level of confidence is at the five-sigma point.

In simple terms, this means that the chances of observing the results they have if there is NO Higgs boson stand at around 1-in-3.5 million. Which is pretty close to saying they’re 100% sure.

Here are a few vital statistics on the new particle:

  • Mass = 125.3 GeV (gigaelectronvolts)
  • 133 times more massive than a proton
  • The particle decays into photons, Z bosons and W bosons
  • Gives matter mass
  • Holds the fabric of the Universe together

Don’t underestimate how important this discovery is. It’s a giant step forward in our understanding of how and why our Universe works. I think it is exceedingly unlikely that this will not prove to be practically useful; but even if it is not immediately practically useful, the discovery is fantastic. Amazing. Awesome!

Taking another step, walking over the next hill, is vital in our journey. Look at how far we’ve come in the past few hundred years. Who knows where we’ll be next? I’ll be watching closely. Will you?