How Things Work Fall 2014 at Towson University!: September 2014

Monday, September 29, 2014

Center of Gravity (or Center of Mass)

A very useful concept in physics is Center of Gravity (AKA CM, Center of Mass - they are usually the same point).

Recall the demo with the mass on a stick. Same mass, held at a further distance from the "fulcrum", is harder to support. It twists your wrist more - it requires a greater "torque".

So, what is torque?

Torque - a "rotating" force

T = F L

For an object to be "in equilibrium," not only must the forces be balanced, but the torques must also be balanced.

Consider a basic see-saw, initially balanced at the fulcrum: See image.

You can have two people of different weight balanced, if their distances are adjusted accordingly: the heavier person is closer to the fulcrum.

Mathematically, this requires that the torques be equal on both sides.

Consider two people, 100 lb and 200 lb. The 100 lb person is 3 feet from the fulcrum. How far from the fulcrum must the 200 lb person sit, to maintain equilibrium?

Torque on left = Torque on right

100 (3) = 200 (x)

x = 1.5 feet

We call the "balance point" the center of mass (or center of gravity).

It is the point about which the object best rotates.

It is the average location of mass points on the object.

It does not HAVE to be physically on the object - think of a doughnut.

The principle is believed to originate with Archimedes (287 - 212 BC). He is believed to have said, "Give me a place to stand on, and I will move the Earth."

FYI: http://en.wikipedia.org/wiki/Archimedes

Wednesday, September 24, 2014

Orbits and Gravitation

First, the applets:

http://www.physics.sjsu.edu/tomley/kepler.html

http://www.physics.sjsu.edu/tomley/Kepler12.html
for Kepler's laws, primarily the 2nd law

http://www.astro.utoronto.ca/~zhu/ast210/geocentric.html
for our discussion on geocentrism and how retrograde motion appears within this conceptual framework

Cool:
http://galileo.phys.virginia.edu/classes/109N/more_stuff/flashlets/kepler6.htm

http://physics.unl.edu/~klee/applets/moonphase/moonphase.html

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Now, the notes.

Johannes Kepler, 1571-1630

Kepler's laws of planetary motion - of course, these apply equally well to all orbiting bodies

1. Planets take elliptical orbits, with the Sun at one focus. (If we were talking about satellites, the central gravitating body, such as the Earth, would be at one focus.) Nothing is at the other focus. Recall that a circle is the special case of the ellipse, wherein the two focal points are coincident. Some bodies, such as the Moon, take nearly circular orbits - that is, the eccentricity is very small.

2. The Area Law. Planets "sweep out" equal areas in equal times. See the applets for pictorial clarification. This means that in any 30 day period, a planet will sweep out a sector of space - the area of this sector is the same, regardless of the 30 day period. A major result of this is that the planet travels fastest when near the Sun.

3. The Harmonic Law. Consider the semi-major axis of a planet's orbit around the Sun - that's half the longest diameter of its orbit. This distance (a) is proportional to the amount of time to go around the Sun in a very peculiar fashion:

a^3 = T^2

That is to say, the semi-major axis CUBED (to the third power) is equal to the period (time) SQUARED. This assumes that we choose convenient units:

- the unit of a is the Astronomical Unit (AU), equal to the semi-major axis of Earth's orbit (approximately the average distance between Earth and Sun). This is around 150 million km or around 93 million miles

- the unit of time is the (Earth) year

e.g. Consider an asteroid with a semi-major axis of orbit of 4 AU. We can quickly calculate that its period of orbit is 8 years (since 4 cubed equals 8 squared).

Likewise for Pluto: a = 40 AU. T works out to be around 250 years.

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Newton's take on this was quite different. For him, Kepler's laws were a manifestation of the bigger "truth" of universal gravitation. That is:

All bodies have gravity unto them. Not just the Earth and Sun and planets, but ALL bodies (including YOU). Of course, the gravity for all of these is not equal. Far from it. The force of gravity can be summarized in an equation:

F = G m1 m2 / d^2

or.... the force of gravitation is equal to a constant ("big G") times the product of the masses, divided by the distance between them (between their centers, to be precise) squared.

Big G = 6.67 x 10^-11, which is a tiny number - therefore, you need BIG masses to see appreciable gravitational forces.

This is an INVERSE SQUARE law, meaning that:

- if the distance between the bodies is doubled, the force becomes 1/4 of its original value
- if the distance is tripled, the force becomes 1/9 the original amount
- etc.

Weight

Weight is a result of local gravitation. Since F = G m1 m2 / d^2, and the force of gravity (weight) is equal to m g, we can come up with a simple expression for local gravity (g):

g = G m(planet) / d^2

Likewise, this is an inverse square law. The further you are from the surface of the Earth, the weaker the gravitational acceleration. With normal altitudes, the value for g goes down only slightly, but it's enough for the air to become thinner (and for you to notice it immediately!).

Note that d is the distance from the CENTER of the Earth - this is the Earth's radius, if you're standing on the surface.

If you were above the surface of the earth an amount equal to the radius of the Earth, thereby doubling your distance from the center of the Earth, the value of g would be 1/4 of 9.8 m/s/s. If you were 2 Earth radii above the surface, the value of g would be 1/9 of 9.8 m/s/s.

The value of g also depends on the mass of the planet. The Moon is 1/4 the diameter of the Earth and about 1/81 its mass. You can check this but, this gives the Moon a g value of around 1.7 m/s/s. For Jupiter, it's around 2.5 m/s/s.

HW answers

1. See notes.

2. 40 / 0.5 = 80 m/s/s

3. lower acceleration

4. See notes. Tablecloth pull, etc.

5. firearm recoil, etc.

6. Principia Mathematica, 1687.

7. Many things, but especially the transition from geocentrism to heliocentrism.

8. Ptolemy (ancient - epicycles, etc.) --> Copernicus (1543 dies; first good account of heliocentrism) --> Galileo (1642 dies; telescopic discoveries, great arguments for sun-centered universe) --> Newton (1642-1727; mathematical reasoning for everything, particularly gravity)

9. They helped explain retrograde motion - the apparent backwards motion of planets. Really, planets are orbiting the Sun and there are times that some bodies are "behind" -- it's like when you pass someone on the highway and they "appear" to be moving backwards at that time.

10. mass - the amount of stuff (in kg); weight - the gravitational pull on this stuff (in newtons). The weight depends on where you are (in terms of how the gravitational acceleration changes). For example, your weight on the Moon is 1/6 that of Earth.

11. newton; pound

12. See 11 above.

13. Greater mass has a greater gravitational pull (weight), HOWEVER it also has more resistance to motion. These two effects exactly cancel.

14. accelerate

15. Letting g = 10 m/s/s --> 10 m/s, 5 m

Monday, September 22, 2014

homework for Newton's laws, etc.

1. Describe each of Newton's 3 laws.

2. A 0.5 kg toy car is pushed with a 40 newton force. What is the car's acceleration?

3. Without calculating anything, what would be the effect (in problem 2) of increasing the mass of the car?

4. Give an example of Newton's 1st law in action.

5. Give an example of Newton's 3rd law in action.

6. Newton's "big book", what I claim is the most important non-religious book of all time is _____ and was published in _____.

7. What things are worth remembering about the so-called Scientific Revolution?

8. Have a basic idea of historical chronology between these fellows: Newton, Copernicus, Ptolemy, Galileo. And roughly, why their contributions are important.

9. What are epicycles and why are they important in the history of science?

10. Distinguish between weight and mass.

11. What is the SI unit of force? What is the English unit of force?

12. How does weight depend on gravitational acceleration?

13. Why do objects in freefall fall with the same acceleration? Give one of the arguments that appeals to you.

14. Think about Newton's 2nd law. What exactly does a constant (unbalanced) force do to an object?

15. Freefall review. Consider a ball falling from rest. How fast would it be moving after 1 second? How far would it fall in this time?

Monday, September 15, 2014

sites from class tonight

http://astro.unl.edu/naap/motion3/animations/sunmotions.swf

On the size of things:

http://htwins.net/scale2/

http://scaleofuniverse.com/

http://xkcd.com/482/

http://xkcd.com/1331/
This is just cool.

http://workshop.chromeexperiments.com/stars/

http://www.youtube.com/watch?v=8yCzzTkDSMo

Jack Horkheimer (R.I.P.), for your interest. Not related to the Celestial Sphere stuff.

Newton's laws

Newton and his laws of motion.

Newton, Philosophiae naturalis principia mathematica (1687) Translated by Andrew Motte (1729)

Lex. I. Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.

Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon.

Projectiles persevere in their motions, so far as they are not retarded by the resistance of the air, or impelled downwards by the force of gravity. A top, whose parts by their cohesion are perpetually drawn aside from rectilinear motions, does not cease its rotation, otherwise than as it is retarded by the air. The greater bodies of the planets and comets, meeting with less resistance in more free spaces, preserve their motions both progressive and circular for a much longer time.

Lex. II. Mutationem motus proportionalem esse vi motrici impressae, & fieri secundum lineam rectam qua vis illa imprimitur.

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.

If any force generates a motion, a double force will generate double the motion, a triple force triple the motion, whether that force be impressed altogether and at once, or gradually and successively. And this motion (being always directed the same way with the generating force), if the body moved before, is added to or subtracted from the former motion, according as they directly conspire with or are directly contrary to each other; or obliquely joined, when they are oblique, so as to produce a new motion compounded from the determination of both.

Lex. III. Actioni contrariam semper & aequalem esse reactionent: sive corporum duorum actiones in se mutuo semper esse aequales & in partes contrarias dirigi.

To every action there is always opposed an equal reaction; or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.

Whatever draws or presses another is as much drawn or pressed by that other. If you press a stone with your finger, the finger is also pressed by the stone. If a horse draws a stone tied to a rope, the horse (if I may so say) will be equally drawn back towards the stone: for the distended rope, by the same endeavour to relax or unbend itself, will draw the horse as much towards the stone as it does the stone towards the horse, and will obstruct the progress of the one as much as it advances that of the other.

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And now, in more contemporary language:

1. Newton's First Law (inertia)

An object will keep doing what it is doing, unless there is reason for it to do otherwise.

The means, it will stay at rest OR it will keep moving at a constant velocity, unless acted on by an unbalanced force.

2. Newton's Second Law

An unbalanced force (F) causes an object to accelerate (a).

That means, if you apply a force to an object, and that force is unbalanced (greater than any resisting force), the object will accelerate.

Symbolically:

F = m a

That's a linear relationship.

Greater F means greater a. However, if the force is constant, but the mass in increased, the resulting acceleration will be less:

a = F / m

That's an inverse relationship.

We have a NEW unit for force. Since force = mass x acceleration, the units are:

kg m / s^2

which we define as a newton (N). It's about 0.22 lb.

3. Newton's Third Law

To every action, there is opposed an equal reaction. Forces always exist in pairs. Examples:

You move forward by pushing backward on the Earth - the Earth pushes YOU forward. Strange, isn't it?

A rocket engine pushes hot gases out of one end - the gases push the rocket forward.

If you fire a rifle or pistol, the firearm "kicks" back on you.

Since the two objects (m and M, let's say) experience the same force:

m A = M a

That's a little trick to convey in letters but, the larger object (M) will experience the smaller acceleration (a), while the smaller object (M) experiences the larger acceleration (A).

history of science info

First, some history: epicycles

http://astro.unl.edu/naap/ssm/animations/ptolemaic.swf

Worldviews:

http://www.stumbleupon.com/su/2jRGYC/dd.dynamicdiagrams.com/wp-content/uploads/2011/01/orrery_2006.swf/

http://www.solarsystemscope.com/

Some background details will be discussed in class. Here are some dates of note:

Nicolaus Copernicus
1473 - 1543
De Revolutionibus Orbium Celestium

Tycho Brahe
1546 - 1601

Johannes Kepler
1571 - 1630
Astronomia Nova

Galileo Galilei
1564 - 1642
Siderius Nuncius
Dialogue on Two Chief World Systems
Discourse on Two New Sciences

Isaac Newton
1642 - 1727
Philosophiae Naturalis Principia Mathematica (1687)

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For Galileo:

http://galileo.rice.edu/

http://galileo.rice.edu/bio/index.html

I also recommend "Galileo's Daughter" by Dava Sobel. Actually, anything she writes is pretty great historical reading. See also Sobel's book "Longitude."

It is also worth reading about Copernicus and the Scientific Revolution.

For those of you interested in ancient science, David Lindberg's "Beginnings of Western Science" is amazing.

In general, John Gribbin's "The Scientists" is a good intro book about the history of science, in general. I recommend this for all interested in the history of intellectual pursuits.

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More historical information regarding Newton:

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

This is really exhaustive - only for the truly interested.

This one is a bit easier to digest:

http://galileoandeinstein.physics.virginia.edu/lectures/newton.html

We'll return to Newton's gravitation (along with Kepler) later in the course.

Saturday, September 13, 2014

Text references

Hello and happy Saturday!

For those of you following in the text, here are worthwhile readings:

Chapter 1: 1.1 (though we'll cover forces shortly), 1.2

Friday, September 12, 2014

motion practice problems

Woo Hoo – it’s physics problems and questions! OH YEAH!!

You will likely be able to do many of these problems, but possibly not all. Fret not, physics phriends! Try them all.

1. Determine the average velocity of your own trip to school: in miles per hour. Use GoogleMaps or something similar to get the distance, and try to recall the time from your last trip. Use your trip from home to Towson, or something that makes sense to you. If possible, do it in miles per hour AND m/s.

2. Consider an echo-y canyon. You stand 200-m from the canyon wall. How long does it take the echo of your scream (“Arghhhh! Curse you Physics!!!”) to return to your ears, if the speed of sound is 340 m/s? (Sound travels at a constant speed in a given environment.) Also, keep in mind that the sound has to travel away from AND back to the source.

3. What is the difference between traveling at an average speed of 65 mph for one hour and a constant speed of 65 mph for one hour? Will you go further in either case?

4. What is the meaning of instantaneous velocity? How can we measure it?

5. What is the acceleration of a toy car, moving from rest to 6 m/s in 4 seconds?

6. How far will a light pulse (say, a cell phone radio wave) travel in 1 second? In one minute? In one year? You don't have to work this out, but you should show HOW it would be calculated. Keep in mind that the light pulse travels AT the speed of light.

7. What do you think a negative acceleration indicate?

8. Consider an automobile starting from rest. It attains a speed of 30 m/s in 8 seconds. What is the car’s acceleration during this period?

9. In the above problem, how far has it traveled in the 8 seconds?

10. Review these ideas. Write down answers, if it would be helpful.

a. standards for the m, kg, and s. Know the original meaning of the standard, and the current standard (approximate meaning - don't worry about the crazy numbers)

b. indicators of pseudoscience

11. Review your notes and the blog entries. Is anything especially unclear at this point?

12. Define the acceleration due to gravity (g).

13. A ball is dropped from rest from a great height. After 2.5 seconds, how fast is it traveling? How far did it fall in this time? (You may use an approximate value of 10 m/s/s for g.)

14. Revisit problem 13. If this has been done on the Moon, would it take more, less or the same time to fall to the ground? How about on Jupiter?

Wednesday, September 10, 2014

Gravitational acceleration

Tonight we discuss the acceleration due to gravity - technically, "local gravity". It has a symbol (g), and it is approximately equal to 9.8 m/s/s, near the surface of the Earth. At higher altitudes, it becomes lower - a related phenomenon is that the air pressure becomes less (since the air molecules are less tightly constrained), and it becomes harder to breathe at higher altitudes (unless you're used to it). Also, the boiling point of water becomes lower - if you've ever read the "high altitude" directions for cooking Mac n Cheese, you might remember that you have to cook the noodles longer (since the temperature of the boiling water is lower).

On the Moon, which is a smaller body (1/4 Earth radius, 1/81 Earth mass), the acceleration at the Moon's surface is roughly 1/6 of a g (or around 1.7 m/s/s). On Jupiter, which is substantially bigger than Earth, the acceleration due to gravity is around 2.2 times that of Earth. All of these things can be calculated without ever having to visit those bodies - isn't that neat?

Consider the meaning of g = 9.8 m/s/s. After 1 second of freefall, a ball would achieve a speed of .....

9.8 m/s

After 2 seconds....

19.6 m/s

After 3 seconds....

29.4 m/s

We can calculate the speed by rearranging the acceleration equation:

vf = vi + at

In this case, vf is the speed at some time, a is 9.8 m/s/s, and t is the time in question. Note that the initial velocity is 0 m/s. In fact, when initial velocity is 0, the expression is really simple:

vf = g t

Got it?

The distance is a bit trickier to figure. This formula is useful - it comes from combining the definitions of average speed and acceleration.

d = vi t + 0.5 at^2

Since the initial velocity is 0, this formula becomes a bit easier:

d = 0.5 at^2

Or....

d = 0.5 gt^2

Or.....

d = 4.9 t^2

(if you're near the surface of the Earth, where g = 9.8 m/s/s)

This is close enough to 10 to approximate, so:

d = 5 t^2

So, after 1 second, a freely falling body has fallen:

d = 5 m

After 2 seconds....

d = 20 m

After 3 seconds....

d = 45 m

After 4 seconds...

d = 80 m

This relationship is worth exploring. Look at the numbers for successive seconds of freefall:

0 m

5 m

20 m

45 m

80 m

125 m

180 m

If an object is accelerating down an inclined plane, the distances will follow a similar pattern - they will still be proportional to the time squared. Galileo noticed this. Being a musician, he placed bells at specific distances on an inclined plane - a ball would hit the bells. If the bells were equally spaced, he (and you) would hear successively quickly "dings" by the bells. However, if the bells were located at distances that were progressively greater (as predicted by the above equation, wherein the distance is proportional to the time squared), one would hear equally spaced 'dings."

Check this out:

Equally spaced bells:

http://www.youtube.com/watch?v=06hdPR1lfKg&feature=related

Bells spaced according to the distance formula:

http://www.youtube.com/watch?v=totpfvtbzi0

Furthermore, look at the numbers again:

0 m

5 m

20 m

45 m

80 m

125 m

180 m

Each number is divisible by 5:

All perfect squares, which Galileo noticed - this holds true on an inclined plane as well, and its easier to see with the naked eye (and time with a "water clock.")

Look at the differences between successive numbers:

All odd numbers. Neat, eh?

FYI:

http://www.mcm.edu/academic/galileo/ars/arshtml/mathofmotion1.html

Monday, September 8, 2014

What's all this about velocity and acceleration?

Motion!

THE EQUATIONS OF MOTION!

First, let's look at some definitions.

Average velocity

v = d / t

That is, displacement divided by time.

Another way to compute average velocity:

v = (vi + vf) / 2

where vi is the initial velocity, and vf is the final (or current) velocity.

Average velocity should be distinguished from instantaneous velocity (what you get from a speedometer):

v(inst) = d / t, where t is a very, very, very tiny time interval. There's more to be said about this sort of thing, and that's where calculus begins.

Now this idea (velocity) is pretty useful if you care about the velocity at a specific time OR the average velocity for a trip.

Also note: if you travel at an average velocity for a period of time (say, 60 mph average, for an hour), the resulting distance is exactly the same as if you'd traveled at a constant velocity for the same time.

Some velocities to ponder....

Approximately....

Keep in mind that 1 m/s is approximately 2 miles/hour.

Your walking speed to class - 1-2 m/s
Running speed - 5-7 m/s
Car speed (highway) - 30 m/s
Professional baseball throwing speed - 45 m/s
Terminal velocity of skydiver - 55 m/s
Speed skiing - 60 m/s
Speed of sound (in air) - 340 m/s
Bullet speed (typical) - 900 m/s
Satellite speed (in orbit) - 6200 m/s
Escape velocity of Earth - 11,200 m/s
(That's around 7 miles per second, or 11.2 km/s)

Speed of light (in a vacuum) -

c = 299,792,458 m/s

This number is a physical constant, believed to be true everywhere in the universe. The letter c is used to represent the value being of constant celerity (speed).

On the other hand, if you care about the details of velocity, if and when it changes, then we need to introduce a new concept: acceleration.

Acceleration, a

a = (final velocity - initial velocity) divided by time

OR

a = (change in velocity) / time

In equation form:

a = (vf - vi) / t

The units here are m/s^2, or m/s/s.

Acceleration is a measure of how quickly you change your speed - that is, it's a measure of 'change in speed' per time. Imagine if you got in a car and floored it, then could watch your speedometer. Imagine now that you get up to 10 miles/hr (MPH) after 1 second, 20 MPH by the 2nd second, 30 MPH by the 3rd second, and so on. This would give you an acceleration of:

10 MPH per second. That's not a super convenient unit, but you get the idea (I hope!).

Today we will chat about the equations of motion. There are 5 useful expressions that relate the variables in questions:

vi - initial velocity. Note that the i is a subscript.
vf - velocity after some period of time
a - acceleration
t - time
d - displacement

Now these equations are a little tricky to come up with - we can derive them in class, if you like. (Remember, never drink and derive. But anyway....)

We start with 3 definitions, two of which are for average velocity:

v (avg) = d / t

v (avg) = (vi + vf) / 2

and the definition of acceleration:

a = (change in v) / t or

a = (vf - vi) / t

Through the miracle of algebra, these can be manipulated (details shown, if you like) to come up with:

vf = vi + at

d = 0.5 (vi + vf) t

d = vi t + 0.5 at^2

vf^2 = vi^2 + 2ad

d = vf t - 0.5 at^2

Note that in each of the 5 equations, one main variable is absent. Each equation is true - indeed, they are the logical result of our definitions - however, each is not always helpful or relevant. The expression you use will depend on the situation.

In general, I find these most useful:

vf = vi + at

d = 0.5 (vi + vf) t

d = vi t + 0.5 at^2

By the way, note that the 2nd equation above is the SAME THING as saying distance equals average velocity [0.5 (vi + vf)] multiplied by time.

Also note that the 2nd and 3rd equations above both calculate d (distance). However, in the 2nd equation, a is missing. In the 3rd equation, vf is missing. So, it's not as though one is more right than another - one may be more appropriate for the situation, depending on what you know in the problem.

Let's look at a sample problem:

Consider a car, starting from rest. It accelerates uniformly (meaning that the acceleration remains a constant value) at 1.5 m/s^2 for 7 seconds. Find the following:

- the speed of the car after 7 seconds
- how far the car has traveled after 7 seconds

Then, the driver applies the brakes and brings the car to a halt in 3 seconds. Find:

- the acceleration of the car in this time
- the distance that the car travels during this time

Got it? Hurray!

There is another way to think about motion - graphically. That is, looking (pictorially) at how the position or velocity changes with time. We'll talk about this in class, and use a motion detector to "see" the motion a little better.

Physics - YAY!

Wednesday, September 3, 2014

What Is Pseudoscience?

What Is Pseudoscience?
Distinguishing between science and pseudoscience is problematic

By Michael Shermer

Climate deniers are accused of practicing pseudoscience, as are intelligent design creationists, astrologers, UFOlogists, parapsychologists, practitioners of alternative medicine, and often anyone who strays far from the scientific mainstream. The boundary problem between science and pseudoscience, in fact, is notoriously fraught with definitional disagreements because the categories are too broad and fuzzy on the edges, and the term “pseudoscience” is subject to adjectival abuse against any claim one happens to dislike for any reason. In his 2010 book Nonsense on Stilts (University of Chicago Press), philosopher of science Massimo Pigliucci concedes that there is “no litmus test,” because “the boundaries separating science, nonscience, and pseudoscience are much fuzzier and more permeable than Popper (or, for that matter, most scientists) would have us believe.”

It was Karl Popper who first identified what he called “the demarcation problem” of finding a criterion to distinguish between empirical science, such as the successful 1919 test of Einstein’s general theory of relativity, and pseudoscience, such as Freud’s theories, whose adherents sought only confirming evidence while ignoring disconfirming cases. Einstein’s theory might have been falsified had solar-eclipse data not shown the requisite deflection of starlight bent by the sun’s gravitational field. Freud’s theories, however, could never be disproved, because there was no testable hypothesis open to refutability. Thus, Popper famously declared “falsifiability” as the ultimate criterion of demarcation.

The problem is that many sciences are nonfalsifiable, such as string theory, the neuroscience surrounding consciousness, grand economic models and the extraterrestrial hypothesis. On the last, short of searching every planet around every star in every galaxy in the cosmos, can we ever say with certainty that E.T.s do not exist?

Princeton University historian of science Michael D. Gordin adds in his forthcoming book The Pseudoscience Wars (University of Chicago Press, 2012), “No one in the history of the world has ever self-identified as a pseudoscientist. There is no person who wakes up in the morning and thinks to himself, ‘I’ll just head into my pseudolaboratory and perform some pseudoexperiments to try to confirm my pseudotheories with pseudofacts.’” As Gordin documents with detailed examples, “individual scientists (as distinct from the monolithic ‘scientific community’) designate a doctrine a ‘pseudoscience’ only when they perceive themselves to be threatened—not necessarily by the new ideas themselves, but by what those ideas represent about the authority of science, science’s access to resources, or some other broader social trend. If one is not threatened, there is no need to lash out at the perceived pseudoscience; instead, one continues with one’s work and happily ignores the cranks.”

I call creationism “pseudoscience” not because its proponents are doing bad science—they are not doing science at all—but because they threaten science education in America, they breach the wall separating church and state, and they confuse the public about the nature of evolutionary theory and how science is conducted.

Here, perhaps, is a practical criterion for resolving the demarcation problem: the conduct of scientists as reflected in the pragmatic usefulness of an idea. That is, does the revolutionary new idea generate any interest on the part of working scientists for adoption in their research programs, produce any new lines of research, lead to any new discoveries, or influence any existing hypotheses, models, paradigms or worldviews? If not, chances are it is pseudoscience.

We can demarcate science from pseudoscience less by what science is and more by what scientists do. Science is a set of methods aimed at testing hypotheses and building theories. If a community of scientists actively adopts a new idea and if that idea then spreads through the field and is incorporated into research that produces useful knowledge reflected in presentations, publications, and especially new lines of inquiry and research, chances are it is science.

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http://www.randi.org/site/index.php/encyclopedia.html

http://www.quackwatch.com/01QuackeryRelatedTopics/pseudo.html

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

http://www.skepdic.com/pseudosc.html

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Also keep in mind sites like:

snopes.com
http://www.straightdope.com/

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http://www.youtube.com/watch?v=NwyeK36Gh-s

Alien Autopsy film - when you watch it, consider what makes it believable or NOT believable.

https://www.youtube.com/watch?v=2MFAvH8m8aI&feature=player_embedded

If you ever have an hour to kill - the definitive documentary on pseudoscience and psychic stuff, in general.