Tuesday, December 16, 2014

Practice for test

Consider 700 nm light ray, hitting a block of plastic at 40 degrees.  It refracts to an angle of 25 degrees.  Find:

- Index of refraction of plastic
- speed of light inside plastic
- wavelength inside plastic
- frequency of light

Consider a lens, focal length of -20 cm. An object is 30 cm in front of it.  Find:

- Image location
- type of image
- magnification of image


Tuesday, December 9, 2014

Attention A block

Your lab draft will be due next Monday (NOT this Thursday).  Lab will then be due next Wednesday.  The test will still be on Friday of next week.

I'll gladly look at labs on Thursday if you like, but we spent too much time on other problems today.  You would benefit from more class time on the lab - which you'll have on Thursday.

So in conclusion:

Monday - lab draft due
Wednesday - final lab due
Friday - test

We'll review for the test Monday and/or Wednesday.

Monday, December 8, 2014

Reminder about formulas for the lab

Thin Len (or Mirror) Equation:

1/f  =  1/di  +  1/do

Remember:  it's quickest to use the x^-1 key on your calculator (4th key down on the left on most calculators).


Percent error = [(experimental - theoretical)/theoretical] * 100

Or if you prefer:

[ (exp - theo) / theo ] * 100

In our experiment, the calculated f (using the thin lens equation) is "experimental".  The "theoretical" value is the one that was printed on the lens or mirror.  (The mirror focal lengths were all 20 cm, except for the one that was 22 cm.)

You'll need to calculate the experimental focal lengths for EACH trial where you have numerical do and di data.  Do these calculations before the next class and add them to your data table (along with the percent error).

Lab guidelines

Basic structure of the lab report:

* Title

* Purpose of lab

* Your hypothesis (from the earlier homework)

* Data table - include all columns from your data, AND 2 more columns:  calculated f, and percent error
   - be sure to calculate these for all trials where you have numerical data for real images

* Sample calculation for focal length (your data table will have ALL of the calculated values, but there is only need for one calculation to be shown)

* Graph(s) if you made any (they are not required, but a graph of di versus do might be instructive)

* Conclusion - probably the biggest, most detailed part of the lab:
 - Address your hypothesis.
 - Give sources of error.
 - Discuss how the image formation depends on object distance.  Note if there "transition points", etc.  This is the tough part of the conclusion (and the most mathematical).
 - Give a general conclusion.

Friday, December 5, 2014

HW for Tuesday A and Wednesday F

Use the lens equation to calculate experimental focal lengths (f) for all of your trials with di and do values - for both convex lenses and concave mirrors.

Play around with this, if your computer will run it:

http://phet.colorado.edu/sims/geometric-optics/geometric-optics_en.html


Wednesday, December 3, 2014

HW for A (Friday) and Monday (F)

Look at your lab data - note trends, if you can see any.  Things like:  does the images become virtual at a certain point, does the image go from smaller to bigger at a certain point, etc.  

Look up the "thin lens equation."  It will have the variables:  di, do, and f.

Thanks!

Tuesday, December 2, 2014

Lab image

See also the previous blog notes about the hypothesis.


Note above - the light source ("object") is on the left, the lens is in the middle, and the screen (where any "real image" forms) is on the right.

Distance between object and lens is do.

Distance between image and lens is di.

In your lab, you will record this data (at least):

do
di
Real or virtual image
Up or down image
Relative size of image (bigger, smaller, same)
Other info

You will perform the experiment for a convex lens, concave lens, concave mirror, and convex mirror.



Monday, December 1, 2014

HW for A (for Wednesday's class). F can do this if you didn't finish it earlier.

Find a formal definition for "focal point" and/or "focal length" of a lens.  Does this apply to all lenses (convex and concave)?

Also, please revisit the hypothesis and tweak it, if you like.

Finally, if you are still unclear about real and virtual images, do a little research about this, too.

As always, this site is helpful:

http://www.physicsclassroom.com/

Also, my apologies for not discussing the hypothesis - when I wrote it on the blog, I forgot to mention that it was optional.  I really didn't want to give you work over Thanksgiving!  Sorry to stress anyone out.


Monday, November 24, 2014

Hypothesizing for the next lab

E block - please try to have this prepared for Tuesday (December 2).  Don't worry if you are still confused.  I just want us to have somewhere to start our conversation.


Upon our return to class after Thanksgiving, we will begin a new formal lab.  This lab is all about convex and concave lenses and mirrors.  You have played with lenses and mirrors a bit in class.  For our next class, please write a formal hypothesis for this experiment.  The hypothesis should address the following:

How will the distance between object and lens affect whether or not an image is formed, how (relatively) large the image is (bigger/smaller) and whether or not the image is right-side up or upside-down?  Also, address what types of optics (concave or convex lenses and mirrors) will produce images (real or virtual).

FYI - a "real" image can be projected onto a screen (think of setting fire with a magnifying glass), whereas "virtual" images are only seen "inside" lenses or mirrors (think of looking at yourself in a bathroom mirror).

Answers may be something like:

- I believe that all images will form at the focal point, and I think that all images will be real.
- I believe that images will only form if the object is very close, but that these images will be virtual.
- I believe that images will be formed only when the object is between the theoretical focal point and twice the theoretical focal point, and that these real images will always be smaller than the object.
- etc.

Be sure to type out your hypothesis and keep a copy for your formal lab report - I will be checking these at the beginning of class.


Friday, November 21, 2014

What to expect on the quiz

1.  Doppler effect
- use of the formula (be sure to understand 't a t a')
- understanding what it means
- red shift, blue shift

2.  Use of trig - Be sure that you can solve for things like:
- sin 20
- finding angle when you know the sine - for example, what is theta when sin(theta) = 0.75

3.  Snell's law and refraction

n = c/v

v = frequency x wavelength

n1 sin (theta 1) = n2 sin (theta 2)

There are two other versions of Snell's law, but you don't actually have to use them - in fact, if you are confused by all the formulas, just forget that those exist and use only the 3 above.

4.  Being able to draw the refracted path when light goes from one medium to another.

SAMPLE PROBLEM:

Light (wavelength 585 nm) goes from air to a new material.  Angle of incidence is 40 degrees and the angle inside the material is 20 degrees.  Both angles are measured with respect to the normal/perpendicular line.  Find the following:

a.  index of refraction of material
b.  speed of light inside material
c.  frequency of light
d.  wavelength of light inside material

Monday, November 17, 2014

HW (for F Weds, A Thursday)

Note:  We will have a quiz on Friday (F) and Monday (A).

Review the variations of the Snell's law equations and create/solve a problem which asks for:

- refracted ray angle
- refracted ray wavelength, speed, and frequency

Consider an equilateral triangular prism of glass (n = 1.5).  A light ray hits it on the left side such that the ray refracted inside the glass runs parallel to the bottom of the prism.  Find the initial angle of incidence (theta 1) on the left side.  Find also the exiting angle on the right side of the prism.

A (also):  Finish informal lab calculations.  Look up the index of refraction of salt water.  Are you close?  Does it change a lot from regular water?

Wednesday, November 12, 2014

HW due Friday for A, and Monday for F

Look up these terms and write down definitions and/or equations:

index of refraction

Snell's law

A picture may be useful for one or both of these.

Monday, November 10, 2014

HW (due Weds A, Thurs F)

Review your notes from the ripple tank lab.

Next, find some definitions for:

reflection
refraction
diffraction
interference

Consider these in light of your experiment notes/drawings - how do these definitions match what you saw?  What was happening in your experiment.

Please write down answers - I will be checking these in our next class.


Friday, November 7, 2014

Problems to try for F block - A block, read up on the Doppler effect

A police car traveling at 30 m/s has a siren that normally blasts a 1000 Hz tone.  Find the frequency you hear when:

A.  The car approaches you
B.  the car drives past you
C.  The car approaches you while you run toward it at 5 m/s
D.  The car has past you while you are running away from it at 5 m/s



Thursday, November 6, 2014

Doppler Effect and more!


http://www.lon-capa.org/~mmp/applist/doppler/d.htm

http://falstad.com/mathphysics.html
Run the Ripple tank applet -
http://falstad.com/ripple/

The key in the Doppler effect is that motion makes the "detected" or "perceived" frequencies higher or lower.

If the source is moving toward you, you detect/measure a higher frequency - this is called a BLUE SHIFT.

If the source is moving away from you, you detect/measure a lower frequency - this is called a RED SHIFT. Distant galaxies in the universe are moving away from us, as determined by their red shifts. This indicates that the universe is indeed expanding (first shown by E. Hubble). The 2011 Nobel Prize in Physics went to local physicist Adam Riess (and 2 others) for the discovery of the accelerating expansion of the universe. Awesome stuff!

http://www.nobelprize.org/nobel_prizes/physics/laureates/2011/

It's worth noting that the effect also works in reverse. If you (the detector) move toward a sound-emitter, you'll detect a higher frequency. If you move away from a detector move away from a sound-emitter, you'll detect a lower frequency.

Mind you, these Doppler effects only happen WHILE there is relative motion between source and detector (you).

And they also work for light. In fact, the terms red shift and blue shift refer mainly to light (or other electromagnetic) phenomena.

Wednesday, November 5, 2014

HW

Read up about the Doppler effect for our next class.  Take notes.

Monday, October 27, 2014

Test Prep

Waves:
- mechanical
- electromagnetic

Further division of wave type:
- transverse
- longitudinal (compressional)

wave equation:
speed (v) = frequency (f) x wavelength (lambda)

Harmonics on a string:
- wavelength = 2L/n
- drawing waveforms
- calculating frequencies and speeds
- knowing that the frequencies go up linearly

Harmonics in a tube:
- same as above, but remember that there are antinodes on both ends (NOT nodes)
- if tube is open on ONE end only, lowest harmonic is one octave lower than if tube is open on both ends
- use speed of sound as your wave speed

Music stuff:
- octave (double frequency)
- go up a semi-tone (guitar fret, piano key, etc.), multiply by 1.0595 (twelfth root of 2)

Saturday, October 25, 2014

Organ pipes info

Waves in organ pipes are similar to waves on strings - both are mechanical, requiring a medium.

The string wave is fixed (nodes) at both ends.  The organ pipe waves is open at both ends - it has anti-nodes at both ends.

http://www.physics.smu.edu/~olness/www/05fall1320/applet/pipe-waves.html

Also, the string wave is TRANSVERSE.  The wave energy travels up and down - perpendicular to the medium (string).

The sound wave is LONGITUDINAL, also known as compressional.  The wave energy (manifested in the motion of the air molecules) jiggles back and forth - parallel to the medium.

However, the air molecules motion can be modeled with a sine wave.  Even though the molecules themselves don't move up and down like a sine wave, their relative position (and therefore the relative density inside the tube) behaves in a sine-like fashion.  So, we can model the motion with a sine graph and treat it just like a string, even though it's very different.  The math, as it turns out, is the same for both.

Wednesday, October 22, 2014

HW (for F on Monday, and A on Friday)

1.  Consider an organ pipe 0.7-m long and open on both ends.  Find the following:

a.  the wavelengths of the first 3 harmonics
b.  the frequencies of the first 3 harmonics (speed of sound is 340 m/s)
c.  the wave shapes associated with the first 3 harmonics - draw them
d.  What would happen if you cap this pipe on one end?
e.  What is the similarity between tubes open on both ends and strings fixed on both ends?

2.  Middle C is 261.6 Hz.  Find the following:

a.  the next two C's above this note (one and two octaves above)
b.  the C one octave below middle C
c.  C#, which is one semi-tone (or piano key or guitar fret) above C
d.  D, which is two semi-tones above C
e.  The wavelength of middle C, if the speed of sound is 340 m/s

(You will probably not be able to do c-e until the next class.)

3.  Practice with waves:

a.  Draw the graph of y = 2 sin(x)
b.  Draw the graph of y = 3 sin(2x)
c.  Draw the graph of y = 4cos(2x) + 2sin(3x)

Use this program (if helpful):

http://graphsketch.com/

4.  Practice with:  c = f l  (where l = lambda)

Find the frequency associated with a blue LED (450 nm).

5.  Recall the demonstrations with Chladni plates and the Ruben's (fire) tube.  Make sure you understand them.



Saturday, October 18, 2014

Practice problems

1.  Differentiate between mechanical and electromagnetic waves.  Give examples.

2.  Draw a wave and identify the primary parts (wavelength, crest, trough, amplitude).

3.  Find the speed of a 500 Hz wave with a wavelength of 0.4 m.

4.  What is the frequency of a wave that travels at 24 m/s, if 3 full waves fit in a 12-m space?  (Hint:  find the wavelength first.)

5.  Approximately how much greater is the speed of light than the speed of sound?

6.  Harmonics

a.  Draw the first 3 harmonics for a wave on a string.
b.  If the length of the string is 1-m, find the wavelengths of these harmonics.
c.  If the frequency of the first harmonic (n = 1) is 10 Hz, find the frequencies of the next 2 harmonics.
d.  Find the speeds of the 3 harmonics.  

7.  Compute the wavelength of the radio signal 107.9.  Note that MHz means 'million Hz."

8.  A C-note vibrates at 262 Hz (approximately).  Find the frequencies of the next 2 C's (1 and 2 octaves above this one).

9.  A red LED has a wavelength of 662 nm.  What is the frequency of light emitted from it?

Monday, October 13, 2014

HW

Don't forget your lab draft on Tuesday/Wednesday.

Also, try these problems - mostly as practice with scientific notation and your calculator.

1.  What is the wavelength of the radio station 97.9 ("98 Rock").  Keep in mind that the number refers to the frequency in MHz.

2.  The visible range of human eyesight is 700 nm to 400 nm.  What are the frequencies associated with this, and which end is red and which is violet?

Friday, October 10, 2014

Wave notes FYI. Lab draft due next week (Tues/Weds)


So - Waves.....  

We spoke about energy.  Energy can, as it turns out, travel in waves.  In fact, you can think of a wave as a traveling disturbance, capable of carrying energy.

There are several wave characteristics (applicable to most conventional waves) that are useful to know:

amplitude - the "height" of the wave, from equilibrium (or direction axis of travel) to maximum position above or below

crest - peak (or highest point) of a wave

trough - valley (or lowest point) of a wave

wavelength (lambda - see picture 2 above) - the length of a complete wave, measured from crest to crest or trough to trough (or distance between any two points that are in phase - see picture 2 above).  Measured in meters (or any units of length).

frequency (f) - literally, the number of complete waves per second.  The unit is the cycle per second, usually called:  hertz (Hz)

wave speed (v) -  the rate at which the wave travels.  Same as regular speed/velocity, and measured in units of m/s (or any unit of velocity).  It can be calculated using a simple expression:





There are 2 primary categories of waves:

Mechanical – these require a medium (e.g., sound, guitar strings, water, etc.)

Electromagnetic – these do NOT require a medium and, in fact, travel fastest where is there is nothing in the way (a vacuum). All e/m waves travel at the same speed in a vacuum (c, the speed of light):

c = 3 x 10^8 m/s

First, the electromagnetic (e/m) waves:

General breakdown of e/m waves from low frequency (and long wavelength) to high frequency (and short wavelength):

Radio
Microwave
IR (infrared)
Visible (ROYGBV)
UV (ultraviolet)
X-rays
Gamma rays

In detail, particularly the last image:



http://www.unihedron.com/projects/spectrum/downloads/full_spectrum.jpg

Mechanical waves include:  sound, water, earthquakes, strings (guitar, piano, etc.)....

Again, don't forget that the primary wave variables are related by the expression:

v = f l


speed = frequency x wavelength

(Note that 'l' should be the Greek symbol 'lambda', if it does not already show up as such.)

For e/m waves, the speed is the speed of light, so the expression becomes:

c = f l


Note that for a given medium (constant speed), as the frequency increases, the wavelength decreases.

Next up - Sound!

Monday, October 6, 2014

Labbage.

The purpose of today's lab is to determine mathematical relationships regarding harmonics on a string.  You will vary the frequency (number of string vibrations per second) and see exactly the wave forms change.

Brief procedure:

1.  Set up string and oscillator.  Record length of string from pulley to point where it is tied to oscillator.
2.  Find the lowest frequency that produces an n=1 harmonic ("one hump").  Record this frequency.
3.  Find the next series of frequencies that produce harmonics.  Record the harmonic number, frequency, and wavelength.  Repeat for several harmonics.
4.  Repeat the trials with a different weight on the end - this is effectively changing the tension in the string.

Calculations:

Determine the speed of the wave for each trial, using the expression:  speed = frequency x wavelength.  The speed values should be in the data table.

The data table should have:  harmonic number (n), frequency, wavelength, speed, mass.

Include a graph of frequency vs. harmonic number (for at least one of the runs).

In your conclusion, discuss the mathematical relationships you've found.  For example, how are frequency and harmonic number related?  How does tension affect the frequency?

Also include sources of error for this experiment.

Basic structure of the lab report:

Title
Purpose of lab
Data table
Sample calculation for speed (your data table will have ALL of the calculated values, but there is only need for one calculation to be shown)
Graph(s)
Conclusion - probably the biggest, most detailed part of the lab

Friday, September 26, 2014

HW for Tuesday (A) and Wednesday (F) including the QUIZ

Quick quiz next class (Tuesday and Wednesday):

period of pendulum (equation)
motion of the pendulum, in general
SI units - what are the standards based on
basic use of sine, cosine, tangent (on calculator)

Also, be prepared to start our formal lab:

Look up the definition of the following wave words:

harmonics
frequency
wavelength

Think about this question and craft a hypothesis.  Do this WITHOUT looking something up online, etc.

How are the frequency, wavelength and speed related to each other in a wave?  How can one affect the other, etc.?


Tuesday, September 23, 2014

HW for Friday (A) and Monday (F)

This homework clearly takes a backseat to any family plans you have between Wednesday and Friday.  A-block:  See also the previous post, if time permits.

1.  For those of you who have little or no trig background:

See me if you're confused about sine (sin), cosine (cos), and tangent (tan).  Look up these values on your calculator:

sin 0
sin 30
sin 45
sin 90
cos 0
cos 30
cos 45
cos 90

Chat with me about SOH-CAH-TOA if you are confused at all.

2.  Go to this website:

http://graphsketch.com/

Under "enter graph equations", type in:

sin(x)

When you hit plot (or return), the graph will emerge above.  To change the size of the graph, play around with the limits.  For a regular sine graph, the y-limits are -1 to 1.  The x-limits are whatever you want them to be, but note that the default units are radians (not degrees).  Recall that 2pi (radians) equals 360 degrees.

Play around with the graphing program.  It's fun!

3.  Finally, come to class with a definition of a WAVE.

Monday, September 22, 2014

HW for Wednesday (F) and Friday (A)

Check out the list of humorous units (for fun!):

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

In this spirit, create your own unit(s).


Also, check out the list of SI prefixes:

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

Next, determine the length of:

- a microcentury
- a milliday

Your answer should be in units that make sense.  Minutes, years, etc. - whatever seems appropriate.

Thursday, September 18, 2014

HW for Monday (F) and Tuesday (A)

Look up the SI standards for time and mass.  Write down a short version.

Also:

Read my old blog posts for homework.  Write down anything you find interesting, or any questions you may have.

http://howdoweknowthat.blogspot.com/2009/07/how-do-we-know-that-earth-is-spherical.html

http://howdoweknowthat.blogspot.com/2009/07/so-how-big-is-earth.html


And if you have time:

http://howdoweknowthat.blogspot.com/2009/07/how-far-away-is-that.html

Tuesday, September 16, 2014

Homework to turn in Thursday (F) and Friday (A)

Please finish these questions/problems - try them all - and be prepared to turn this in to me in class on Thursday.

1.  What is a "simple pendulum"?  What makes a simple pendulum "simple" or why do we call it simple?

2.  Calculate the period of a simple pendulum with a 0.5-m long length:
a.  on Earth
b.  on the Moon, where g = 1.7 m/s/s
c.  on Jupiter, where g is about 2.5 times that of Earth

3.  Draw the approximate shape of the graph for period vs. length of a pendulum.

4.  Draw the approximate shape of the graph for period vs. angle of swing (from 0 to 90 degrees).

5.  You want a pendulum to swing with a period of 2 seconds.  How long must it be?

6.  What is the current standard of the meter based on?

Monday, September 15, 2014

HW for F and A

Yikes - forgot to update this with the homework for Tuesday (F):

Look up the equation/relationship for the period of a simple pendulum.

Describe how the equation works; the variables involved, etc.

>

For A block (Wednesday):  2 things

First, look up the equation/relationship for the period of a simple pendulum.

Describe how the equation works; the variables involved, etc.

Second, look up the definitions of the meter and the second.

Thursday, September 11, 2014

Hmmmm

There is some problem downloading Logger Pro.  I guess the password has been changed and I'm not sure what the new one is.

Try the demo version for now:

http://www.vernier.com/downloads/logger-pro-demo/


Wednesday, September 10, 2014

HW for F (for Friday) and A (for Monday)

If you have a computer at home, please download LoggerPro - a software package site-licensed to Park School:

https://parkscience.pbworks.com/w/page/351271/LoggerPro

Run the installer.  When prompted for a password, type:  ecosystem


Open the software and play around with it.  If you have data for period (in seconds) vs. length (in cm, or whatever unit you used), plot it.

You may need to "autoscale" the graph -- to make it fit nicely.  Do this by right-clicking and choosing autoscale (twice).  On a Mac, right click is a two-finger tap on the keypad or CTRL-click.

If you are feeling ambitious, try a "curve fit" under the analyze heading.

If you are able, print out your period vs. length graph.

Tuesday, September 9, 2014

Lab prep

We determined in class that the length of a pendulum seems to matter most - it seemed to have the greatest effect on the time for one complete swing of a pendulum (also known as the period).  Angle mattered a little, but mostly if you were at an angle greater than 15 degrees (with respect to vertical).

For next class, prepare a data table for many trials.  You'll be measuring time/period vs. length.  In your data table, decide:  the units for each column, whether or not you're timing one swing or multiple swings (and have a separate column for a single swing), enough space for 20 different lengths (and maybe multiple trials of each), etc.  Also, prepare a short statement that describes your technique for measuring the time of swing (period).

Ultimately, you will produce a graph that suggests a mathematical relationship (if there is one to be found).

Wednesday, September 3, 2014

HW for A and F block classes

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.

>


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

>

Also keep in mind sites like:

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


>


Alien Autopsy film - when you watch it, consider what makes it believable or NOT believable.
If you ever have an hour to kill - the definitive documentary on pseudoscience and psychic stuff, in general.