Shepcons Science and Stuff

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What colour is your shirt today? Whether it’s black, white, blue or red, it’s visible. Today we’re talking about things that you and I can see. Specifically, the visible spectrum of light. Also called the optical spectrum of light, this is the wavelength that is visible to our eyes (via the cones). The most convenient way to start this off is to talk about the rainbow. Starting from the top, the colours on the rainbow are red, orange, yellow, green, blue, indigo and violet. Every one of those colours has a different wavelength (740nm, 625nm, 590nm, 565nm, 520nm, 500nm, and 435 respectively [2]).

Most of the light that we encounter in our day to day life is white, and in fact all light originates as a white light. We see the different colours of the rainbow when an object reflects or refracts a specific wavelength of the white light. The orange that you have in your kitchen is that colour because an orange absorbs all the wavelengths of visible light except for the 590nm-625nm range, which gets reflected into your eyes. That is how most of the objects are perceived as colour to us. This also explains why the leaves on the trees change colour in the fall. Chlorophyl (which you may recognize as the chemical that allows photosynthesis) absorbs all the light except for green, but as the hours of sunlight decrease in fall they stop producing chlorophyl, when carotene and anthocyanins remain the only chemicals. Carotene makes the leaves appear yellow and orange, while anthocyanins cause the reds and purples.

That absorption and reflection of light is only a partial story about why we see rainbows as a beautiful series of colours though, nothing else in nature really occurs like a rainbow does. That’s because white light has an interesting property when shining through a prism. It will refract the range of wavelengths that are contained in white light to separate the colours perfectly (as is demonstrated on Pink Floyds Dark Side of the Moon album cover). A rainbow occurs when water particles in the air act as the prism and separate the wavelengths on a large scale. You see the same exact effect when you play with a hose on the mist setting on a sunny afternoon.

One of the most interesting aspects of visible light in my opinion is the colour magenta. It is a colour that doesn’t actually have a place on the electromagnetic spectrum. How can this be possible? What is a colour if it doesn’t actually exist? That’s because every colour on the EM spectrum has a complimentary colour, which is the colour you will see if you stare at something long enough and then take it away (ie, blue and green mixed together will produce a cyan colour). The complimentary colour to green though exists between red and blue, and as we learned above they exist on opposite ends of the visible light spectrum. Magenta is your brains best estimate to what the naturally occurring compliment would be for green.

[1]http://mirror-au-nsw1.gallery.hd.org/_c/natural-science/prism-and-refraction-of-light-into-rainbow-AJHD.jpg.html

[2]http://physics.about.com/od/lightoptics/a/vislightspec.htm

[3]http://chemistry.about.com/od/colorchemistry/f/how-magenta-works.htm

[4]http://chemistry.about.com/od/colorchemistry/f/how-magenta-works.htm

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Wavelength: 7 x 10^-7 - 1 x 10^-3 m

Frequency: 3 x 10¹¹ - 4 x 10¹⁴ Hz

Energy: 2 x 10^-24- 2 x 10^-22 eV

Infrared (IR) is the closest to visible light we’ll get to on this end of the spectrum. At it’s shortest wavelength it is just bordering on what we can see with the naked eye. The IR radiation can be broken up further into the following spectrum:

Near Infrared: 0.7µm - 1.3µm wavelength

Short Infrared: 1.4µm – 3µm wavelength

Mid Infrared: 3µm - 8 µm wavelength

Long/Thermal Infrared: 8µm - 30µm

Far Infrared: 15µm – 1000µm

Astronomers divide the spectrum differently, usually as follows [1]:

Near IR: 0.7 µm – 5 µm

Mid IR: 5 µm – 40 µm

Far IR: 40 µm – 350 µm

Mid Infrared and Long Infrared are emitted by an object naturally, while Near Infrared and Short Infrared are reflected off an object.

IR was first theorized by Emilie du Chatelet in 1737 in a paper titled Dissertation sur la nature et la propagation du feu. Her theory was proved correct in 1800 when William Herschel published the first record of experimental proof of IR radiation.

The most common type of IR radiation that you or I would recognize is heat. IR radiation from the Sun provides Earth with 49% [2] of its heat, with thanks to greenhouse gases. Without any of those, no IR heat would be absorbed and slowly released back into our lower atmosphere to keep us at our cozy temperature.

Without IR radiation, we wouldn’t be able to use nightvision technology. Both traditional nightvision and thermal imagine use light in the IR spectrum to enhance images in otherwise dark areas. The absorption of IR into clouds and the atmosphere allow our weather satellites to make mostly accurate weather predictions that you end up seeing on the nightly news. In astronomy, IR can be used to measure through clouds of molecules, nebulae, and detect redshifted objects [3].

Blackbody radiation is the natural amount and type of electromagnetic radiation that an object absorbs at any given temperature above absolute zero. At Earthly temperatures, blackbody radiation exists in the IR range [4], as that is the only range on the spectrum that it won’t absorb entirely.

Some animals have evolved natural mechanisms that allow them to detect IR light. These animals include pit vipers, pythons, some boas, vampire bats, and some insects. It is unknown the degree to which these animals can sense IR light, but there’s no doubt that it must help them hunt prey or avoid predators!

[1]http://www.ipac.caltech.edu/outreach/Edu/Regions/irregions.html

[2]Passive Solar Heating & Cooling Manual. Rodale Press, Inc.. 1980. Retrieved 2007-08-12 

[3]http://www.ipac.caltech.edu/outreach/Edu/importance.html

[4]http://galileo.phys.virginia.edu/classes/252/black_body_radiation.html

[5]http://www.medcatalog.com/images/Meditherm.gif

Let’s take a step back and talk about the most basic measurements in physics. Measurement and observation are the two most important parts of science, bar none. Without observation, we would have no way to verify our theories. Whether you prefer theoretical or experimental physics, both of these aspects are critical. Right now I’m going to discuss the basics of measurement.

The four most important measurements you will ever need in physics are speed, volume, density and acceleration. Almost any equation you look at will feature some of these four in a large way. You can find these using length (metres or m), time (seconds or s), and mass (kilograms or kg). The different combinations of these base measurements will give you anything you need to know about an object.

To find the speed of a given object, you must divide the distance (length) an object travels by the amount of time it took said object. If a car travels 132km in 92 minutes, the equation would look like:

v=112km/92min

v=1.2km/min, therefore it would be travelling at 1.2km/min. To turn that into kilometres per hour, we just need to multiply by 60 (as there are 60 minutes in an hour), for an answer of 72km/hr. Of course, this is assuming that the car was travelling at that speed from the first moment of measurement.

To find the acceleration of an object, you must divide the change in velocity by the time it takes for that change to occur (a=Δ v/t or a=[v2-v1]/t). To find the rate of acceleration of the car above, we’ll say that it accelerated from 0km/hr to a speed of 72km/hr in 8 seconds. Using the equation above, we’ll find:

a=[72km/hr-0km/hr]/8s

a=[72km/hr]/8s

a=9km/hr/s

With that, we know that if the car accelerated constantly, its speed increased by 9km/hr every second. Of the four basic measurements, acceleration is probably the hardest for most people to wrap their minds around as it includes two separate measures of time.

Now, let us assume that we have a very poor auto designer that made this car, and it is a perfect rectangle. It is 3m long, 1m wide and 1.5m tall. If you want to know the volume inside the car, you use the equation x=(l)(w)(h), or volume=length times width times height. So for this car, it would be:
x=(3m)(1m)(1.5m)

x=4.5m^3

So now we know the car has 4.5 metres cubed of space.

Now we want to know how dense this brick of a car weighs! I’m going to tell you that the vehicle weighs 500kg. We know that it has a volume of 4.5m^3, and with those two pieces of information I can show you how to find the density! It’s quite simple actually, it is just d=m/v, or density equals mass divided by volume. Let’s just go right ahead and plug numbers into the equation:

d=500kg/4.5m^3

d=111kg/m^3

Now we know that the car has a density of 111kg for every metre cubed of space, it has 4.5 cubic metres of space, it can accelerate 9km/hr/s, and travel 72/km/hr.

With all of the above measurements, you can find out how much cargo you can fit in a ship, how much fuel per kilogram of mass you’ll need to launch out of the Earths atmosphere, how long you’ll have to accelerate to get to a cruising speed, and how long it will take to travel the distance to Mars at that speed. You can then figure out deceleration for landing and the weight of the cargo and astronauts under the new gravity on Mars.

Now there is one important aspect to measurements like this that I haven’t mentioned, as it isn’t important for hypothetical scenarios like the car above. It is the uncertainty of a measurement, or sometimes referred to (incorrectly in my opinion) as an error in measurement. If I wanted you to find the density of the car, and I only knew the mass give or take 100kg, you wouldn’t be able to find the exact density. That is alright in measurements, but you have to take that into consideration as a +/- factor so that you can be aware of the 200kg (100kg over 500kg, 100kg under 500kg for a total difference of 200kg) gap.

Wavelength: 1 x 10^-3 - 1 x 10^-1 m

Frequency: 3 x 10⁹ - 3 x 10¹¹ Hz

Energy: 2 x 10^-24- 2 x 10^-22 eV

Microwaves are the next stage of electromagnetic radiation. They have wavelengths from 1mm to 1m and frequencies from 0.3GHz to 300GHz. This puts them in between radio waves and infrared on the EM spectrum. Jagadis Chandra Bose was the first person to really experiment with the EM spectrum in the microwave range. In 1895 and 1896, before Marconi was credited for the first radio message, Bose sent information over a mile using microwaves in the 2-5mm wavelength [1]. This makes him the first person to use radio waves to transmit information.

Microwaves pass through clouds, fog, clothes, and most non metal materials with relative ease which makes them excellent for communications[2]. They don’t penetrate most metal materials however, which means containing them in a metal area (such as the walls of a microwave oven) will concentrate the waves, making them more powerful. Anything with a high enough water content will absorb microwaves, causing the particles within to vibrate and give off heat. This is the basic principle that a microwave oven uses to cook your food, and it’s also why the tupperware containers that you throw in there won’t heat up.

Other than the microwave oven, sources of microwaves include the maser, which is similar to a laser but it concentrates microwaves as opposed to visible light, the sun and other celestial objects, and Cosmic Microwave Background Radiation (CMB). The CMB was detected in 1964 by Arno Penzias and Robert Wilson [3], and it is a nearly uniform level of microwave radiation everywhere in the universe. The equal levels in all directions is one of the huge proofs for the Big Bang, or Big Expansion.

Household wireless communications, from modems and routers, cell phones, cordless phones, and nearly any other cordless technology uses microwaves in the 2.4GHz to 4GHz range (Take a look at your cordless phone, odds are it will say 2.4 on it somewhere, unless it’s a newer phone which might have 4.something on it. That’s the frequency that it uses).

Microwave radiation is a non-ionizing radiation, which means that it is not powerful enough to knock electrons away from particles. That is how stronger forms of radiation lead to cancer, so sitting in front of your microwave is almost universally considered to be safe. The harm that could come from concentrated microwaves such as in the microwave oven would be from the excitement of water particles, which would essentially cook whatever they hit. Again though, it has to be on the powerful end of microwave radiation and concentrated to have that effect.

[1]http://www.tuc.nrao.edu/~demerson/bose/bose.html

[2]An introduction to atmospheric radiation, Kuo-Nan Liou, pg349

[3]http://aether.lbl.gov/www/science/cmb.html

Wavelength: > 1 x 10^-1 m

Frequency: < 3 x 10^9 Hz

Energy: < 2 x 10^{-24 eV}

Continuing on with the Electromagnetic Spectrum (to be called EM spectrum from now on) topic, today I’ll talk about radio waves specifically. They are the longest waves in the EM spectrum, having a wavelength from the size of an American football to an American football stadium. Since it is made of photons, the waves travel at the speed of light, which is pretty damn fast. Artificial sources of radio waves include radio towers (duh.), RADAR, satellite communications, garage door openers, and many many other sources. Naturally produced radio waves come from sources such as lightning strikes and astronomical objects.

Radio waves were first predicted to exist theoretically by James Clerk Maxwell in 1865[1]. He noticed a striking similarity between the behaviour of visible light, and electronic/magnetic waves. In 1887 Heinrich Hertz generated the first radio waves experimentally, which launched into an age of radio communications. I think we can all agree that this was a positive step for humanity.

Different frequencies of radio waves behave differently. They reflect, refract, polarize, diffract and absorb into the surroundings in different ways. Because of this, different frequencies have different specialized uses. Radio waves that you use to listen to music and talk radio are intercepted by an antenna, and then a tuner resonates at the specific wavelength frequencies to make one station stand out above the rest[2]. Radio wave are also used in medicine for the treatment of sleep apnoea, in MRI’s, and for bloodwork. My personal favourite use of radio waves though is in radio astronomy. Using radio satellites, scientists can look at objects in the sky with an amazing amount of accuracy, since objects in space give off radio waves. Some of the wavelengths of these objects can actually extend longer than a mile![3]

That’s all I have to say on the topic of radio waves. Those of you that are clever can probably guess my next topic. It rhymes with Dicrodaves.

[1]http://www.juliantrubin.com/bigten/hertzexperiment.html

[2]http://www.infoplease.com/ce6/sci/A0860617.html

[3]http://science.hq.nasa.gov/kids/imagers/ems/radio.html

http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

If you’re looking at a monitor of some sort right now, you have electromagnetic radiation to thank for that. The electromagnetic spectrum ranges from radio waves to gamma rays, and is responsible for a surprising amount in between. Everything on this spectrum is a form of radiation, although most of it isn’t harmful to us.

The entire spectrum is composed of photons, which are particles of light. They are measured by their wavelength, frequency, and energy. The wavelength is a measurement from the peak of one wave to the peak of the next, and on this spectrum can range from Nanometres (one billionth of a metre) to 100+ metres(m). The frequency of a wave is how many peaks pass a certain point per second, and is measured in hertz (Hz). Lastly, we have the measurement of energy. This is simply how much energy the photons have, measured in electron volts (eV). You can find the energy of a photon using the equation E=(h)(c)/λ. E is equal to the energy (eV), h is Plancks constant, c is the velocity of light (just like in that good ol’ E=mc^2 equation), and λ is the wavelength (the symbol is called Lambda. You don’t need a crowbar to open up this symbol).

If you plug the numbers into the above equation, you’ll quickly find that the wavelength and frequency are inversely proportional, which is also common sense once you think about it. A wave that is 100m long will pass an individual point less times per second than a wave that is 1nm. Something strange does happen with the different wavelengths and energies though. The lower end of the spectrum with low energy has the photons behaving as a wave, whereas the high energy end of the spectrum has the photons behave as particles. This is called wave-particle duality[1], and is responsible for the famous Double Slit experiment.

I think it’s about time to get into the actual types of radiation all along this spectrum.

Radio waves: That’s right, listening to the radio is a form of electromagnetic radiation. This is also where over the air TV signals come from, and a lot of phone signals. I couldn’t imagine the world today without these wonderful waves. They have the longest wavelength, reaching 100m and higher.

Microwaves: Another convenience of the modern world, microwaves are here too. In addition to cooking your food, telecommunications satellites use microwaves to get signals down through Earths atmosphere, it’s used in RADAR and it has a strong Doppler effect. My personal favourite part is the Cosmic Microwave Radiation that we are now able to detect everywhere in the universe, which tells us a lot about the Big Expansion.

Infrared: This is in your remote control for your television. It’s also the heat from the Sun, the police use infrared cameras before they bust your grow op, and some animals such as snakes can see in the infrared range.

Visible: As useful as the previous types have been, this is the one that we’re the most familiar with. We see in this range of light. When you’re looking at what colour anything is, you’re seeing the light that is reflected off that object. Within visible light, the spectrum goes Red, Orange, Yellow, Green, Blue, Indigo, Violet. You may know those colours as Roy G. Biv, or the colours of the rainbow. Red has the longest wavelength, and violet has the shortest. Now the names of the previous and next items make sense.

Ultraviolet: This is the one that makes a lot us hate the Sun. If you’ve ever had a sunburn, you have ultraviolet light to thank for that one! The ozone layer blocks most of the ultraviolet light which we can be thankful for, but enough gets through to be a pain in the skin. Some insects have the ability to see in the ultraviolet spectrum, and you’ve probably seen them use UV lights in shows like C.S.I.

X-Rays: If you’ve ever broken a bone, you know about these first hand. X-rays are a very high energy form of radiation, and occurs naturally in space. Luckily our atmosphere blocks almost all of the x-rays from hitting us. This is a form of Ionizing radiation, which means that it knocks electrons lose. These electrons flying around in your body can break DNA cells, which sometimes repair with mutations. That’s called a cancerous cell, and it’s a good idea to avoid getting those.

Gamma Ray: Watch out, Radioactive Man! This is the big daddy of the electromagnetic spectrum. You want to avoid gamma rays at all costs, as they are even more energetic than x-rays. These have a wavelength in the nanometre range, and will cause you lots of trouble. They are caused by nuclear explosions and radioactive atoms. They do occur naturally in space quite frequently, which is a danger for astronauts who don’t have our atmosphere to protect them. One of the most devastating forces in the universe is called a Gamma Ray Burst, and it is a huge beam of gamma rays that flies in a single direction killing everything in its path. In my attempt to be a fear monger, I’ll let you know that it’s possible for one of these bursts to hit Earth at any moment, without warning, killing everything that is facing the burst instantly. On the plus side, because gamma rays are so energetic, they can also be used to destroy cancerous cells in some forms of treatment.

Below is a table listing all the wavelengths, frequencies, and energy levels of the different types of radiation. [2]

Wavelength (Hz) Frequency (m) Energy (eV)

Radio

> 1x10^{^-1} Hz

< 3x10^{^9 m}

< 2x10^^-24 eV

Microwave

1x10^^-3 - 1x10^^-1 Hz

3x10^⁹ - 3x10^{^11 m}

2x10^{^-24}- 2x10^^-22 eV

Infrared

7x10^{^-7} - 1x10^{^-3} Hz

3x10^¹¹ - 4x10^^14 m

2x10^^-22 - 3x10^{^-19} eV

Visible

4x10^^-7 - 7x10^{^-7} Hz

4x10^¹⁴ - 7.5x10^{^14 m}

3x10^{^-19} - 5x10^^-19 eV

Ultraviolet

1x10^{^-8} - 4x10^^-7 Hz

7.5x10^{^14} - 3x10^{^16 m}

5x10^^-19 - 2x10^^-17 eV

X-ray

1x10^{^-11} - 1x10^^-8 Hz

3x10^¹⁶ - 3x10^{^19 m}

2x10^^-17 - 2x10^^-14 eV

Gamma Ray

< 1x10^^-11 Hz

> 3x10^^19 m

> 2x10^{^-14} eV

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[1] http://physics.about.com/od/lightoptics/a/waveparticle.htm

[2] http://imagine.gsfc.nasa.gov/docs/science/know_l1/spectrum_chart.html

[3] http://science.hq.nasa.gov/kids/imagers/ems/index.html

The laws of Thermodynamics are in actuality the Law of Conservation of Mass Energy put into practice. These laws are a big reason why almost anything works. They are quite easy to state and explain though, despite how important they are.

Thermodynamics in essence deals with the relationship between heat and other properties. Specifically, any system where thermal energy is converted into any other kind of energy, be it potential, kinetic, electrical, or anything else is governed by the Laws of Thermodynamics. Any energy that is being used anywhere in the universe, is being governed by the Laws of Thermodynamics.

Think about the impact of that statement for a moment. Anywhere that something is moving, something is heating or cooling, or anywhere that basically anything is happening, is being governed by these laws. Me typing this out, or you reading this. It is all thermodynamic. Now that you have a grasp on the import of this law, lets get into some of the driving forces behind it. There where be a few definitions up ahead, so bear with me.

Thermal Contact: This is when heat transfers from one object to another

Thermal Equilibrium: Equilibrium is achieved when two objects no longer transfer heat to one another

Thermal Expansion: When an object expands because of heat (Think of a hot air balloon. Thermal Contraction also exists)

Conduction: This is when heat flows through a solid object, such as a copper wire.

Convection: When heated particles transfer their energy (heat) into another substance it is convection. This is like cooking an egg in boiling water.

Radiation: Not as scary as the word sounds, this is just the transfer of heat through electromagnetic waves. The Sun radiates heat onto us, your microwave radiates heat onto a Hungry Man

Insulation: This one should be obvious, it’s when something is used to prevent the transfer of heat.

Those are the methods of heat transfer, all of which are important. Any time one of those results in anything other than pure heat, the Laws of Thermodynamics step in.

If you want to figure out the heat capacity (C) of an object, we must use the following equation.

C=Δ Q/Δ T where Δ Q is the change in heat or energy, and Δ T is the change in temperature. A good conductor of heat would have a low value of C, meaning that it doesn’t hold on to the heat too well (lets clarify this right now, there is a difference between heat and temperature as I’m sure some of you are questioning. Temperature is the measure in a single body, so I hope my temperature doesn’t reach 103F. Heat is how energy is transferred from one object to another. If I was dropped into a cannibals sauce pan, it would heat me up until my temperature was hopefully around 425F internally so that I wouldn’t cause food poisoning).[1]

Now for the meat and potatoes (which are hopefully at an appropriate temperature). The actual Laws of Thermodynamics are coming up, so hold on to your butts.

Zeroeth Law of Thermodynamics: Two systems in thermal equilibrium with a third system are in thermal equilibrium to eachother.

This is a law that is so basic, and so understandable that it was called the “Zeroeth Law” after all the other laws were discovered. It really just means that if Object A is the same temperature as Object C, and Object C is the same temperature as Object B, then Object A and B must be the same temperature. This makes taking temperature possible, and was only actually considered a Law come the beginning of the 20^th century.

First Law of Thermodynamics: The change in a system’s internal energy is equal to the difference between heat added to the system from its surroundings and work done by the system on its surroundings.

This is another very simple law, as they all are really. If you heat an object up, the object will either have an increase in temperature, or energy will go towards doing work. It can be either one of those, or a combination of the two. A perfect example is a steam engine. Coal heats up water, the water gets turned into steam, and the steam will turn a turbine or piston. There is a mathematical representation of this law, which is this:

U₂ - U₁ = Δ U = Q – W

U_{2 is the internal energy at the end of the process}

U_{1 is the internal energy at the end of the process}

_{Q = heat transferred into (Q > 0) or out of (Q < 0) the system}

W = work performed by the system (W > 0) or on the system (W < 0).

Some people would consider this law to be the foundation of the Law of Conservation of Energy, as it is stating that all energy going into a system has to be used for something, none of it can be lost along the way.

Second Law of Thermodynamics: It is impossible for a process to have as its sole result the transfer of heat from a cooler body to a hotter one.

Leave a hot bowl of soup on the counter, what happens? The soup will cool down, as it’s impossible for heat to transfer from a cooler object into a hotter one. This is closely related to entropy, and the law itself can be restated to say “In any system, the entropy must remain constant or increase”. This has unbelievably far reaching consequences. Quite possibly the largest is the arrow of time, it means that everything will continue to get slightly cooler and more chaotic, we will never be able to go backwards to what used to be.

Third Law of Thermodynamics: The entropy of a perfect crystal of an element in its most stable form tends to zero as the temperature approaches absolute zero.

What this means is that a perfect structure at a temperature of absolute zero will have absolutely no entropy. No energy will be exchanged in any way, nothing will be moving. Essentially, it will be a perfectly stationary object. Now, it is impossible for anything to have an entropy value of zero, therefore it is also impossible for anything to reach absolute zero. There will always be some outside energy reaching into the system to stop zero kelvin from being reached. That is a temperature of -273.15°C[2] so you know, and outer space on average is −270 °C or 3 Kelvin[3.

[1]http://physics.about.com/od/thermodynamics/p/thermodynamics.htm

[2]http://chemistry.about.com/od/chemistryfaqs/f/absolutezero.htm

[3]http://en.wikipedia.org/wiki/Outer_space

Matter cannot be created or destroyed. It can be converted into energy, but you will never be able to create something out of nothing. This is the Law of Conservation of Mass-Energy. Everything that is in the universe today has existed since its creation some 13.7 billion years ago, in one form or another. As usual there is an equation that relates to this law, and although it’s relatively unknown, you may have heard it once or twice in your life. It is known as E=mC^2. The amount of energy (E) an object has is equal to its mass (m) times the speed of light (C) squared.

Some of you aspiring scientists out there may have questions about this, because this law isn’t immediately apparent. If matter can’t be destroyed, then how does first almost completely destroy a sheet of paper or a log? Where does all that woody matter go? Well, the first piece of this puzzle is a fairly obvious one. When you burn a log, a lot of its mass is still there in the form of ash. That doesn’t solve the problem entirely though. If you were to create a chamber full of stuff and put it on a scale, it would weigh the same no matter what happens to the stuff inside the chamber. You could light it all on fire, and it would weigh the same as long as it is a closed system. In addition to the ashes of the burned log above, some of its mass is converted into a gas, the smoke that you see rising from the fire. But this still doesn’t quite account for the entire mass of the original log. There’s a last piece of the puzzle that’s still missing.

Energy! That’s the answer, matter can be converted into energy. How do we know this? Well in addition to the closed chamber thought experiment above, we can feel it! Why is a fire such a great idea on a cool Autumn night? Because it creates heat, that is matter turning into energy. Now that we have all the puzzle pieces, lets put them together in a new experiment courtesy of an old frenchman.

Antoine-Laurent Lavoisier was one of the first scientists to realize that this law has no exceptions, no matter what. He set up an experiment in which he heated mercury Oxide (HgO) in a closed system, and measured its mass to the milligram[1]. Now normally if you heat something up enough in a closed system such as a glass container, pressure will build until it explodes. No one wants an unintentionally exploding experiment. To get around this, Lavoisier used an upside down bowl in a basin of water. As the HgO was heated, it produced a gas that pushed the water out of the way as it expanded. This gas was later named Oxygen, but that’s not important right now. What is important is that he ended up with oxygen, and a silver liquid, mercury. Although the mercury took less space than the HgO originally did, it had the same mass in a closed system. That means nothing was actually destroyed! Lavoisier had just invented the Law of Conservation of Mass-Energy! Well, more accurately, it was just the Law of Conservation of Mass, it wasn’t until Einstein that we combined the two separate laws for energy and mass.

Now, I want to share my favourite implication of this law to close this lesson. If Energy cannot be created or destroyed, where did exactly we come from as humans? We evolved from older creatures, which evolved from bacteria and single celled organisms. They came from amino acids which are made of protein. Proteins are made of sulfur, oxygen, simple inorganic materials but with a kickstart. These building blocks of life are just littered around the Earth and other planets, and in space rocks as well. They’re created in our Sun, and ejected into our solar system. The Sun is able to spit these outs, because it was made from gases such as hydrogen and metals such as iron. You can keep tracing all of these back to when the universe was just a cosmic soup, forming the first elements out of energy. Carl Sagan said it perfectly in the final PBS episode of his Cosmos series. “We are star stuff harvesting star light. Our lives, our past and our future are tied to the sun, the moon and the stars.”[2]

[1]http://www.lightandmatter.com/html_books/7cp/ch01/ch01.html

[2]http://www.cooperativeindividualism.org/sagan_cosmos_who_speaks_for_earth.html

I can explain that! Today we’re going to be talking about Gravity. Now what exactly is gravity? We all know that it stops us from floating off into space, but what else does it do? Well, everything that has mass attracts everything else in the universe that has mass. The Earth is pulling down on you, and you are pulling up on the Earth. The Moon is pulling on the oceans to create tides, and the oceans are pulling on the Moon as the tide goes in and out. Now why does this all happen? Well, it’s simple to give the answer, but to truly explain is a very complicated thing. For now we’ll stick with the simple parts, and we’ll come back to the complicated parts of gravity once I get into Particle Physics and String Theory. Let’s start with the equation, and find applications for it farther down the line.

[1]
In the above equation, F is equal to the force given by the inverse square law. The inverse square law is simply that the strength is inversely proportional to the square of the distance from the source of gravity[2]. The “G” is the Gravitational Constant, and is intentionally capitalized. A lowercase “g” would represent the local gravity conditions, ie. a free fall through Earths atmosphere without friction. G is a complicated number to calculate on its own, so just assume that you have it to an accurate degree for now. “r” is the distance between the centre points of the two objects being measured (eg. The Earth and the Sun). The last two variables, m1 and m2 represent the masses of the two objects being measured.

Now you astute readers may be asking yourselves by now, “If the Earth pulls on the Sun with the same force that the Sun pulls on us, why is it that we orbit the Sun and not the other way around?”. Good question! I was hoping you would be clever enough to ask that, and the answer is quite simple. We have to turn to our dear friend Isaac Newton to answer this, so lets allow him to speak for a moment.

“The alteration of motion is ever proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.”

Why Sir Isaac, I could not have said it better myself! If you recall, my friendly reader, that was Newtons second law of motion. The force exerted on an object its mass times the rate of acceleration. Because the Sun has a much larger mass than the Earth, we are the ones that accelerate into an orbit.

The Sun is still affected by the Earth, and we pull it to and fro ever so slightly. Without going into to much detail, this is how we detect some distant planets. Our telescopes are so accurate, that we can detect the back and forth wobbling of a distant star. Through this, we can gather roughly the size of a Neptune or larger sized planet that is yanking the star around as it orbits.

Wait! Everyone just wait one second…something isn’t right about this. No one move until I figure it out, gravity is a fickle mistress, and we don’t want to upset it or we may find ourselves hurtling into space at random. Someone just threw a monkey wrench into Newtons gravitational theory, and it came from 1905. Einstein just created his Theory of Relativity, and it has some problems with Newtons theory. According to that equation up there, if the mass of the Sun were to suddenly change to nothing and it disappeared out of existence, we would notice right away as everything in the solar system was flung into interstellar space. But we all know that nothing can travel faster than light, not even the information that gravity has just changed at the center of this solar system. So if it takes like ~8 minutes to travel to Earth from the Sun, it would take at ~8 minutes for the Earth to get the message that it needs to stop orbiting.

Don’t let this trick you into thinking that Newton was wrong though, his equations work, and they do work beautifully. But Einstein doesn’t want to look at gravity as a force that one object exerts on another. Einstein came up with the idea that if something has a large enough mass, it will distort space around it. A good visual comparison would be a bowling ball at the center of a trampoline, and you throw a large marble at a high speed just passed the ball. The marble will orbit around the bowling ball because of the distortions that were created. If you were to remove the bowling ball, it would take time for the depression it created to flatten out again, therefore the marble would orbit for a time afterwards. It would be a relatively short time, but the orbit wouldn’t change instantly, which appeases the almighty monkey wrench for now. There are flaws with the analogy, but for now I’d prefer to not get into to much depth with Relativity. It just gives you a good idea of what the concept looks like.

So we are at the point where Newtons theory still gives us a wonderful way to figure out the numbers behind gravity, while Einstein took the idea and ran a marathon with it so as to not break the universal speed limit of light. There are some caveats about gravity, such as what happens in a black hole, but that requires some more basic lessons first. I can’t wait for the Cosmology classes, how about you students?

[1]http://plus.maths.org/content/how-does-gravity-work

[2]http://en.wikipedia.org/wiki/Inverse-square_law

Democritus of Abderra

Democritus was a Greek philosopher and scientist who was born around 460 BCE and lived in Abderra, according to most accounts. He was called the “Laughing Philosopher” because of the fact that he never ventured outside without laughing at the follies of humanity to everyone who would listen. There is a lot of uncertainty about his life, and most of what we do know is from second hand reports. He came from a noble family with money, and was educated in astronomy and theology by Magi that were left to him from the Persian Empire as a reward for helping the Monarch and its army.

He travelled the world to gain more knowledge, studying in Egypt, Ethiopia, Persia and India. Two of his known teachers and friends were Leucippus and Anaxagoras. Leucippus was on of the first scientists or philosophers to come up with the idea of Atomism, the idea that if you look down far enough then everything is made of some indivisible building blocks[1]. This is an idea that Democritus expanded on greatly, and is one of his greatest accomplishments.

Right now, I’m going to pause to clarify something. There is a difference between the Atom that Leucippus and Democritus imagined from the Atom that we know and love. They referred to it as an abstract idea, whereas we have the atom that people recognize in a Bohr-Rutherford diagram. I am going to take a page from Leon Lederman, and refer to Democritus’ indivisible piece as the a-tom, and the object that we know and study will be called the atom, from now on. Now that this is cleared up;

Anaxagoras had a cosmological theory that everything that we know has always existed in some form, but they existed as pieces that were smaller by unimaginable amounts in a kind of primordial soup[2]. It wasn’t until the development of mind, he believed, that these objects were able to be seperated into the world we know today.

Once Democritus returned from his travels, he became known for his extraordinary grasp of natural phenomena occurring in the world, including his unprecedented ability to forecast the weather. People at the time of course thought this to be incredible, and some accounts say that he claimed to be able to predict future events through his meteorology.

According to Diogenes Laertius, Democritus had a large number of works on topics such as physics, mathematics, ethics, cosmology and music. Most importantly though, is his A-tom. While Leucippus may have put Democritus on the path of the A-tom, it is essentially Democritus’ theory alone. He believed that nothing could be created out of nothing, so there must be some basic building blocks that created everything that we see in the world around us. This was his indivisible A-tom. He didn’t experiment to come to these conclusions, he performed mental experiments where he would cut an object in half, then cut that in half with a smaller knife[3]. He would mentally continue that process until he was left with some block that was so small, it could not be divided by a knife of any miniscule size. You can see that this is different from the atom, as we have been blasting that apart into quarks and leptons, gluons and muons, protons and electrons. Democritus may have started science on the path of particle physics that we know today.

This troubled many scientists for many reasons at the time, with one of the biggest problems being; What exists in between these A-toms for them to travel through? It can’t be a substance, because that substance would have to be smaller than the A-tom which just wouldn’t make sense. No one at the time wanted to believe that there was just nothing, an empty void in between A-toms, because that was borderline heresy. In the end, a popular opinion was that these A-toms travelled through the aether, which would be related to a water A-tom, although Democritus himself liked the idea of the “void”.

Democritus compared the different forms of A-tom to the different letters of the alphabet. You could combine different A-toms together that have different properties to create everything we see in the world, just like you can combine letters of the alphabet together to form words, sentences, paragraphs, and books.

In perhaps the most shocking foresight of Democritus’, he believed that the images we see of everything is just a type of A-tom that is being shed from whole objects. He believed that it was like a stretchy film that could shrink and it could expand, but only the group of a-toms that clustered together small enough could enter our eyes[4]. We know today about photons reflecting off objects at particular wavelengths to create the images we see, but without any real tools to measure something like that in Democritus’ time it is an incredibly close guess to how vision actually receives images in the world.

There are many other theories and hypotheses that Democritus put forth into the world, some surprisingly accurate and others missing by an atoms length. But for what we need to know in regards to modern science, the theories that we’ve just discussed are more than enough to give you an idea of how brilliant this Laughing Philosopher really was. It would be like if I guessed spaceships of 2500 years from now were powered by chemical reaction that is only found in the Eye of Jupiter, when in reality the fuel comes from the Rings of Saturn. An incredibly close guess based on something we don’t understand yet at all.

[1]http://en.wikipedia.org/wiki/Leucippus

[2]http://en.wikipedia.org/wiki/Anaxagoras

[3] Lederman, Leon. The God Particle pp32-58, 1993

[4]http://plato.stanford.edu/entries/democritus/