PPT 1 for physics 101

1. Things that we will see in the course
* What is science, what is not.
* Where science stops.
* How an ICBM works
* Why we need howitzers
* How the eye works
* How radiography works
* Photovoltaics and solar collectors. What is the difference.
* Nuclear bombs and nuclear power plants are not the same thing.
* Why I have a radioactive source in my pocket and I do not care.
* Why you are sitting on a radioactive source and you do not care.
* Why your muscles attach to certain places in the skeleton and not in others.
* And more....

2. An unexpected radioactive source……..

3. What causes the
different colors?
Why are the
colors in the fainter
rainbow in reverse
order?
What is Science?

4. An acceptable explanation must agree with what is
observed.
An acceptable explanation must have predictions
that can be tested.
Typical scientific process
Observation Explanation
Experiment

5. Example
You leave some meat out in the open.
After a few days, you may see some worms in the meat.
This is the observation part.
You want to know where the worms come from.
You may come up, say, with an idea.
* Some insects may deposit their eggs in the meat.
This is the explanation part.
Someone else, however, may think
* The meat turns itself into worms.
To verify the idea, you put some netting around the meat.
* No worms! This rules out the spontaneous transformation.
This is the testing (experiment) part.
Then you go on... You take a microscope to confirm the
presence of eggs, then you try to understand which insect lays
its eggs, etc. etc. etc....

6. Alternative (but less intuitive) view: Popper
A scientific statement makes predictions that can be proven
wrong.
(Popper’s definition)

7. Example.
Newton stated that masses attract each other.
Many experiments have been attempted since.
All experiments, to date at least, show that masses
DO indeed attract each other, no matter how small they are.
Do these experiments prove Newton’s ideas?
Not really.
They show that the masses that we have tested do
attract each other. However, we have not tested all masses
of the Universe.
So, these experiments are not a real proof.
The experiment, however, do not prove Newton’s ideas
to be wrong.
We never measured a repulsion, for example.
Had we measured a repulsion, Newton’s theory would be wrong,
or it would need to be amended.

8. Following Popper, we conclude that
There is no such thing as scientific proof.
Scientific statements are required to be tentative and
disprovable.
At its best, science tells us what has not yet been shown to
be wrong.
But why, then, do we (often at least) term
Scientific statements as laws?
Because in most cases many people have tried to prove some ideas
wrong. All these experiments failed to prove the ideas wrong.

9. Bottom Line:
Scientific evidence is always circumstantial. There is never an
absolute proof.
Does it mean that scientific theories are useless?
Well, science is quite useful….
No science = no internet, no bypass surgery, no airplanes.
Does it mean that scientific theories are glorified fantasy?
No. Scientific theories are quite linked to reality.
Some theories of physics that have stood up to every test for over
400 years.
Are we positive that these laws are correct? --- No.
Would you bet that they are wrong? --- Only if you like losing
bets.

10. Sometimes, a well-tested scientific theory is proven “wrong“.
How? By experiment.
Does it mean the people who developed and used the theory were
idiots?
No. These people made a number of experiments to test the theory,
and the tests agreed with the theory.
Usually, if a theory was verified and accepted for a long time,
new experiments show that the theory is a special case of a
more comprehensive phenomenon.

11. Example.
The theory of gravitation.
Developed in the 1600s, it remained THE theory until the early 1900s,
when Einstein showed that it was a special case of a more general
theory.
Newton’s theory was OK when the masses of the objects were small.
For large masses (e.g., a star), other rules applied.
Einstein’s theory was confirmed by experiment (i.e., not proven
wrong) by Eddington.

12. More recently:
* About 15 years ago, a new force, called “dark energy”,
was discovered. Dark energy repels things, opposing gravitation.
Dark energy was not foreseen by our models of the Universe.
How did scientists react?
* A couple of years ago, some experiments suggested that neutrinos
May move faster than light. This would have contradicted Einstein's
Relativity theory. How do you think scientist reacted?

13. Science, however, is not the only thing in the world…

14. Scientific statements are always tentative. Alas, many
things in life cannot be tentative.
Politics, law
Matters of life and liberty cannot be based on tentative
decisions. The constitution cannot be proven wrong. It
can be amended, though.
In mathematics and logic, definitions, axioms, and
proven theorems are not falsifiable. The content of
established mathematics and logic is not science (as
defined by Popper).

15. Religion
Both testaments make it very clear that the Bible is not
about tentative, testable statements. Same for the other
religions. They are not tentative.
Does it mean that religion is wrong, or bad?
No, it just means that the criteria that we use in science do
not apply to religion.
We do not compare apples with oranges…
The meaning which you find in a work of art can never be
wrong. However, it can be trivial or superficial. One may
or may not like it, but nobody sane of mind can deny the
value of art.

16. Pseudo-science
… is something that presents itself like science,
looks like science, sounds like science, but it is not science…
Examples
• Homeopathy. Look up discussion on quackwatch.com.
Tested several times, and proven not to work each time.
Yet, it has been around for more than 100 years.
• Claims that the earth has been visited by aliens.
When the claims fail to stand up to Popper's test
(If they are wrong, can you prove them wrong?), they are pseudo-science.