Friday's Physical Law - Work Work Work

As we have previously seen force impacts a lot on motion. Today I want to look at how we apply forces, or rather what allows us to apply forces, and as you may have guess by the title this involves the concept of work.

When we exert a force on an object what we are doing is work on that object. And by work we don't mean what one does 9 to 5 but rather transferring energy. To be precise work W is done on an object when ever and object is moved a distance d parallel to a force F acting on the object

• W = F d cosθ

when F and d are parallel θ = 0 and then cosθ = 1 and the work is maximum when the angle (θ) between F and d is 90° then they are perpendicular and cosθ and hence W = 0.

Well that can all be a little complicated and daunting, but essentially you can think of it in terms of a box, if I push the box across the floor I give it motion and hence energy (by doing work: force across direction across), however if I hold it while walking across the room the box itself is only in motion because I am and as such is not getting any energy from me (so no work done: force up direction across).Of course while I was lifting the box (before I carried it across the room) then I was doing work on it.

So as you an see (hopefully) work is done and energy transferred when giving an object motion or changing its position with respect to gravity. We refer to these forms of energy as kinetic energy and gravitational potential energy, respectively.

So we will now look at these a bit closer. Firstly, kinetic energy occurs when anything has velocity (is moving), and is dependant only on the mass of the object and the velocity it has:

• E = ½mv²

And gravitational potential energy, is a form of potential (or stored) energy which depends on position with a gravitational field, and it depends on height (above ground), the mass of the object, and gravity (on Earth the acceleration due to gravity, g, is about 9.8 at the surface of the Earth, but this will vary for other planets and heights, at this stage I plan to deal with this next week):

• E = mgh

There are many other types of energy that we will get to in the fullness of time, such as the potential energy of a spring, thermal energy (heat), electrical energy, nuclear energy etc, but the important thing to note is that energy can never be created or destroyed only converted (transferred) from one form to another (this incidentally is the first law of thermodynamics).

And when it comes to motion this idea of conservation of energy can simply be put as:

• ½mv²_f + mgh_f = ½mv²_i + mgh_i + W

where the _f indicates the object in a final state and the_i indicates the object in an initial state. And we can see that friction is a case of work acting against the motion of an object, reducing its kinetic energy and creating heat (thermal energy).

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Hot off the presses

The 54th edition of the Skeptics circle is up over at Action Skeptics, and Akusai has upped the standard, focusing on "The Stuff That Woos are Made Of"

My cat Loki and I moved in, I arranged the furniture to minimize qi flow, and I called the painter. He made me some very pretty words on the front door: "Jack Bixby, Skeptical Investigator."

With some of the highlights being:

• Orac's look at critical thinking in medical schools or lack thereof
• Skeptico's anniversary special "why did the chicken re-cross the road"

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How to ... "Design" a Car

OK so yes you may have noticed a certain anti-ID theme appearing in this series of posts, well science education is something that I take seriously, and one of the anti-science themes that is prevalent in my readings at present (such as Robyn Williams' Unintelligent Design) and hence giving me my ideas for this is ID so that is where I am going but I promise I will diversify (at some point).

I digress, this is somewhat of a response to the "Watchmaker" argument that has been put forward at various times. Essentially it states that something that complex cannot have occurred naturally and hence has to have been designed as a whole. In particular this is a response to the idea of "Irreducible Complexity" (IC) that underpins the the ID arguments.

Essentially if a car was IC then if you removed a bit of it, then it would no longer work. And this is approximately the case (well at least if you consider a very basic car model) especially if you fail to account for other uses of the components - in other words if you take away everything but a wheel you no longer have a car or anything that works as a car does but you still have a wheel which is useful in its own right - which seems to be something that has happened from the IC proponents.

So how have we designed (or perhaps evolved would be closer to the truth) a car:

• we started with the development of using trees as rollers to aid transporting heavy objects (such as one often sees in depictions of the building of the pyramids in Egypt).
• later these we modified to a pair of wheels linked by an axle and a bed on which to put things to be transported, so now the wheels stayed with the load instead of being rolled over and then moved.
• Of course something needs to move this simple cart, and we have had plenty of option in terms of man power (or slave labour) or beasts of burden (horses, oxen etc).
• Wheels are simplified so that instead of being solid wood they now consist of a rim and spokes radiating out of the centre to that rim, this reduces weight of the wheel and allows for greater speed (for example chariots).
• A two wheeled cart is not a stable platform, if left to its own devices it will tip forwards or back wards so we will add another set of wheels and now we have a stable platform that does not need to be constantly hitched to something.
• Brakes can help in the situations where you need to stop.
• In addition to being pulled wheels can also be ridden on lo and behold we have a bicycle (or at least the fore runner to a bicycle)
• Pedals and maybe some gearing might help with the riding of the bicycle as it comes towards its modern form.
• An ability to steer (normally the front wheels but rear wheel steering works too) helps you get more accurately to where you are going.
• Of course for those of you tied of pedal power or with a lame horse why not power it with a steam engine (trains and tractors are good examples of how this was done).
• If steam is not your thing then why not try the new fangled internal combustion engine.
• Multiple gearing that is easily switched between will of course help speed up travel.
• Oh and don't forget the Pneumatic tires.

And of course now you have a car - although you might want to think about adding a stereo so you can listen to your tunes, maybe 4WD for going off road, GPS for when you get lost etc etc etc.

As you can plainly see that a car did not come fully assembled in one foul swoop, but gradually evolved over thousands of years.

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Friday's Physical Law - Conservation of Momentum

Well all have experience Newton's Third Law of Motion in action, every time we push on something like a door we can feel it pushing back on us.

What we have here is action and reaction, and as it is normally put Newton's third law reads every action has an equal and opposite reaction. So if I push the door with a force of 5 N the door pushes back with the same force.

Of course the main thing to note about these forces is that they operate on different objects. Many people seem to get this confused by thinking that the forces cancel out, which can only happen when forces are acting on the same object, which is not the case here. To use my previous example: I push on the wall and the wall pushes back on me.

Of course the action and reaction occur at the same time, they start at the same time and they finish at the same time. So this gives us another measure of the motion that results from these forces. Remember that as we saw a couple of weeks ago

• F = ma,

and since we know the force applied in the action and reaction and the mass of each object and now the time over which the force acts we can work out the change in velocity (remember that a = v/t). So this gives us what we refer to as impulse:

• F t = mΔv = Δp

What we have here is another measure of motion, momentum (p) which is equal to an objects mass times its velocity. And from Newton's third law we see that when ever we have to objects interacting (action and reaction) then their is a change in momentum is equal (and opposite). That is the total (nett) momentum of two interacting objects is conserved (the same before and after the interaction).

As we progress through this series we will see many more examples of the idea of conservation of quantities. But in this case we have a very good means to analyse the interaction of objects (the idea of two objects interacting can be extended to multiple objects where momentum will still be conserved) such as in collisions.

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How to ... sweep almost all science under the rug

In the "culture wars" with ID (intelligent design) I have always found it amusing at the big tent attempts of the IDists to encompass such a wide range of creationists into their folds.

We know that all creationists try to sweep good science under the rug by ignoring, denying or misrepresenting it, mostly in biology and related fields such as anthropology and palaeontology. But some take their anti-science to greater and greater heights, particularly YEC (young Earth creationists) who manage to be not just anti-evolution but anti-every-thing-else-in-science as well.

The YEC seems to be the most vocal proponents of ID, but why then are other groups such as OEC (old Earth creationists) backing the completely anti-science stance of YEC when they are more intellectually consistent with the rest of us?

This is something that I cannot answer, maybe some one else can for me, but what I want to look at here is just what science exactly does the YEC position deny? (WARNING: this could be a very long list) In brackets I have listed some examples of our understanding of which exactly is undermined by YEC. The ones with * are also in common with all IDists.

1. Microbiology* (antibiotic resistance)
2. Botany* (breeding plants)
3. Zoology* (breeding animals)
4. Ecology* (co-evolution of plants and animals)
5. Biochemistry* (protein synthesis)
6. Medicine* (Germ theory of Disease)
7. Anthropology* (Descent of Man)
8. Palaeontology* (fossil records) - Note that YEC also has issues with the dates of fossils
9. Chemistry/Atomic Physics* (cause of mutations in DNA and hence their effect)
10. Nuclear Physics (radiometric dating)
11. Cosmology (age of the universe)
12. Particle physics (since it goes hand in hand with cosmology)
13. Geology (formation of rocks and fossils)
14. Tectonics (the movement of tectonic plates)
15. Physical Geography (the shape of the land)

Hmmmm well I think my list is not as long as I thought it was going to be, but then again I think that I have pretty much covered the whole spectrum. And if I have forgotten anyone's speciality please tell me. I also realise that I could have made this list longer by including more specialities that I have lumped into generalities (eg medicine). And while the list is longer in the section that is ID general rather than YEC specific those YEC specific areas are rather broad.

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Psychics are bad for you

For all those who are fans of psychics maybe you have found the wrong blog to be reading.

The Amazing Randi has updated the terms of his paranormal challenge, in which if you can prove you have paranormal powers in a mutually acceptable test then you walk home with $1,000,000. Now instead of merely waiting for applicants they will go out and target high profile paranormalists, taking the challenge to them.

Several notable psychics have said they will take the challenge only to back down, one major example of this Sylvia Browne, and there is now an online petition that you can sign to urge her to step to the plate

You can read more about all this here where Skeptico gives us a good run down.

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OV-102, may she rest in peace

And from the I can't believe I nearly forgot to post about it files comes some thing that is very dear to me.

February 1 2003 (Thursday was the 4th aniversary) the space shuttle Columbia broke up on re-entry killing all seven astronauts aboard.

I have always felt a special bond with the space race and Columbia in particular since my birthday falls on Cosmonaut's Day (April 12), which is the anniversary of the first manned space mission Vostok 1 (1961) in which Yuri Gagarin became the first man in space. And what does that have to do with Columbia, on the 2oth aniversary of Vostok 1, STS-1 the first orbital test flight of the space shuttle was launched. So Columbia (OV-102) with two people on board was launched on my first birthday (1981). Of course I was only one and didn't really register such things, but looking back on it well I thought it was cool and special (ok I really am a nerd aren't I - but is that really such a bad thing) and that Columbia was my shuttle.

Also the STS107 mission was a science mission and one of the experiments was using the Isreali Dust storms Experiment camera to try to take picture of Red Sprites (to put it simply a form of upwards lightning) and to help orient themselves on the storms the made use of the World Wide Lightning Location Network (WWLLN - pronounced "woollen" as in made of wool) which was started by a now retired member of my research group and is a project that we are still much involved in. So I hade multiple connections to this tragedy

So like I mentioned February 1 she broke up on re-entry, killing all seven of the crew, so if we could take a moment to remember Brown, Husband, Clark, Chawla, Anderson, McCool, Ramon. And please give me a moment to mourn my shuttle.

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Friday's Physical Law - Reflections

In the first two weeks of this series I started out with simple motion as my fundamentals and then built from there, and I do intend to continue in that vein but every now and then I am going to feel like something different and this week is one of those times.

Today I am going to discussing some thing that is part of my PhD research and is also something that merits a comment when talking about Climate change. That is reflection.

To begin with we must have a wave travelling along that interacts with an object (or the boundary between two media - ie water and air). Now when this wave (and for the most part I will be dealing with electromagnetic (EM) waves such as light, radio waves etc., although this applies to all types of waves) interacts with an object any of three things can happen:

1. Reflection
2. Transmission
3. Absorption.

Which of these occurs depends on the properties of the object and the wave. And in most cases two or even three of these things happen together.

Reflection is where the light strikes the object and bounces off. Transmission is where the light passes through the object. Absorption is where the light is ... well ... absorbed.

If we start of with a wave intensity of 1 then:

• R + T + A = 1

where R, T, and A are the amounts of the wave reflected, transmitted and absorbed respectively.

The obvious examples are a mirror for reflection, a window for transmission, and a black object for absorption.

And you will notice that I mentioned a colour specifically for the absorption, in fact it is due to reflection and absorption that we see colour. Light shines on an object and if red light is reflected and the green and blue light absorbed then we see the object as being red.

Now what does all this have to do with my research, well, I study the electrical interactions of the upper atmosphere (more about this another time) and the main tool we use is by using the ionosphere and ground as a mirror (albeit and imperfect ones) and sending radio waves long distances between these two "surfaces" and so the reflective properties of particularly the ionosphere are very important. And by looking at the changes in the signals we receive we can determine the changes in the reflections along the way and hence the local (or global) changes that has caused them.

And of course I also mentioned that reflections can affect climate change, if you have snow, ice or tundra then the sunlight reflects of this quite well, as any one who has gone skiing can attest to. But as these melt less of the sunlight is reflected and hence more is absorbed (since the Earth is not very transparent). This leads to more heat being trapped in the Earth-atmosphere system leading to more warming (even if only locally) which will lead to more melting which will lead to more absorption and so on. In other words it is a positive feedback loop for the warming which is not a good thing, especially since we can quite easily measure the amount of ground covered by snow, ice and tundra and it is decreasing.

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