I was wondering
if we were allowed multiple chances for the online quizzes or if the quiz was
just to be taken once and that grade stands.Posted on: January 28, 2008 (Mastering Physics; Reading Quizzes )
I was wondering
if we were allowed multiple chances for the online quizzes or if the quiz was
just to be taken once and that grade stands.
When you do
a Homework or a Reading Quiz that you see that you always have several tries
for each item. If you get stuck on one or more of them you can interrupt, maybe
ask questions of me or your TAs, and then go back. Once you have gone through
everything and you completed all items the Quiz is finished and the score stands.
Posted on: March 8, 2007 (Chapter#s on Schedule)
At our schedule
in Physics 406 website, it says that we are responsible from 4th, 5th and 6th
chapters. However, we also went over other chapters like 9th and 10th.
Does it mean that we do not have to know these chapters(9th and 10th and some
others) in detail, just reading the course review will be enough?
By chapter#s
I mean according to the Syllabus and my Lecture Notes. That we draw from different
chapters in the book occasionally has to do with the fact that every author
has a specific preference, and I do have my preference how to teach a subject.
There is no "perfect" book for a course. There are very good ones
that we use, but in order to get the most important topics into a 1-semester
course some adjustments need to be made.
So, in essence, please read the chapters as in the Syllabus. This should be
consistent with the Course Review and the Lecture Notes.
Posted on: January 30, 2003 (Problems with the CPS Remote)
When I tried
to create my student account an error came up that my serial number was already
in use. I attempted a few more times and finally it seemed to worked, but as
I found out after it was a typo and not the right number. I tried to edit the
number on my information page but it keeps telling me that my serial number
isn't valid.
If you have
problems with either the Remote or your Enrollment Code that you purchased from
the MUB Bookstore or from Durham Book Exchange, please bring the item back to
them and explain your problem. The are taking back faulty items and replace
them. They send the faulty ones back to EInstruction.
Posted on: January 30, 2003 (Dark Observation Site close to Campus)
I have a
question about homework #2 (observation of spring night sky). Where would be
the best place on campus for me to do this? You see I don't have a car or access
to someone who does, and I don't know anyone in the class. I was hoping to find
a place that I could walk to or get to by campus shuttle to minimize my time
outside traveling so I can spend more time outside observing without freezing
to death. It's hard to think of a place on campus that isn't well-lit at night.
Do you have any advice?
A good place
to go that is not farther away than the UNH Observatory, but much darker, is
at the old Durham Reservoir. Go out Main Street past the Field House up to where
Mast Rd. goes off to Channel 11. Take a right, pass the Horse Barns and follow
a road along where a temporary construction parking lot is (unfortunaelt well
lit). Go past that until you come to a small body of water. Here you find a
good place to watch. Go in a group to work together. Look
at the Map for more advice.
Posted on: April 22, 2002
As I stare
out my window at 2:30am on Saturday morning I can't believe what I see. In the
20 years or so that I have been staring at the sky I have never in my life seen
anything as breath-taking as the Northern Lights are tonight. I have seen the
northern lights probably a hundred times before (from my camp near Canada),
but I have NEVER seen them from anywhere this far south. Is it unusual to be
able to see the Northern Lights vividly from a location of this latitude? Is
is also unusual to be able to see them so vividly during this time of year?
I always thought the Northern Lights occured strongest during the late fall
and early winter time. Have they always been visible from our current vantage
point and I just missed them in the past?
Darn!! I
should have stayed up late on Saturday! That's life. I haven't seen an aurora
here, only in Alaska or from the plane so far.
Congratule yourself to seeing this spectacle.
It is indeed not so unusual to see an aurora here in NH. It has happened several
times over the past few years. The reason is the sun's activity, which was at
its maximum 200 and 2001. The activity is still high and has produced a few
strong coronal mass ejections over the past couple of weeks. When they hit Earth
they can push the aurora farther south than usual.
This one apparently was even seen in San Diego. See: http://www.spaceweather.com/
for information.
The blast has to hit at the right time of the day to make it strong, i.e. at
or past midnight at the place where you look. That is why you saw it at 230
AM.
Auroras do not correlate with the seasons. Only further north you may have a
hard time to see an aurora in the summer, as it doesn't get really dark too
far north at that time.
Posted on: April 19, 2002
I was just
wondering how you would prefer us to include the sources in our papers. What
I mean by this is can we just give you a list of all the sources we used at
the end, or do you want us to cite them every time we use them in the actually
text?
Have all
your refernces in the paper. Please place a list of all your references at the
end of the paper with all pertinent information: Authors, title, (in case of
book: publisher, location of publisher, year; in case of journal: journal, volume,
page #s, year). I do not insist on a specific format, but your list should follow
a consistent pattern. See below:
In the text you need torefer to your references either by (a) putting author
and year [A_author et al., 1987] or (b) a number that points to the reference
[1]. In the latter case you need to have all references numbered in sequence
at the end. This makes the two possible ways of your reference list:
(a) A list that is alphabetized according to 1st authors:
A_author, ..., Title, Journal, Volume#, Page#, Year
B_author, ..., Title, Publisher, Location of Publisher, Year
C_author, ....
(b) A list numbered in sequence:
1) B_author, ..., Title, Publisher, Location of Publisher, Year
2) A_author, ..., Title, Journal, Volume#, Page#, Year
3) C_author, ...
Posted on: September 13, 1999 Part I
New information
from the Hubble telescope against the elastic rubber band effect (universe
to pulling back a small ball) shows the universe going out to infinity.
What is pulling the Universe out? Gravity, and from what? A large black
hole? And their universe with gravity?
What you are
asking about, is the expansion of the universe, whether this expansion
may be stopped one day and reversed. The rate of expansion is measured
km/s per MegaParsec (distance of 1 million Parsec), as galaxies that are
farther away than others move away from us at a faster speed. The current
best number for this "Hubble Constant" (named after Edwin Hubble, who
found this expansion first) is Å 70 km/s per MegaParsec (give and take
Å 10 km/s per MegaParsec). Because the universe contains mass (all the
galaxies with their stars etc.), it was expected that the expansion would
slow down due to the gravitational force between the masses. Therefore,
the big question was, whether this expected deceleration of the expansion
would be strong enough to stop and reverse the expansion in the distant
future or not. However, new observations of very distant galaxies with
Hubble Space Telescope and other big telescopes on Earth now seem to indicate
that expansion is even accelerating, and not decelerating! [For more information
see the Press Release of UC Berkeley
on this from earlier this year] If these results are confirmed, the universe
for sure will expand forever. Then, of course, the task will be to find
the "pushing" force that is still expanding the universe. This is one
of the unresolved mysteries! It definitely cannot be a black hole or any
other object, because the force acts everywhere in the universe and points
outward everywhere.
Posted on:September 13, 1999 Part II
If you believe
in the big bang theory, why do some scientists believe that some stars
are older than the universe itself? This is like the baby being older
than the mother. Isn't that impossible?
This is a
typical problem that arises, when observations and related models are
not accurate enough yet. Such a paradox usually points to a remaining
problem, as it does here. This result can mean:
All of these observations and models have their inaccuracies. However, currently it looks like the main reason for this puzzle may be found in the surprising observation cited in the answer to the previous question. If the expansion of the universe indeed accelerates, we have derived the age of the universe under the wrong assumption, i.e. the universe is in fact older than we have deduced before. With the current best value for the expansion speed of the universe all galaxies started from the same place about 14 billion years ago, if we assume the speed remained same. The must be even shorter, if the expansion was faster in the past, i.e. gravitation decelerates the universe. The oldest stars are thought to be about 13-14 billion years old. This created the puzzle. However, if the expansion was lower in the past, as new observations indicate, the universe is older than 14 billion years, ergo no problem! Look at it with the following example: If you drive from New York City to Durham, it takes you for the Å 240 miles 4 hours at 60 miles per hour. If you are speeding at 80 miles per hour for the first hour, then you get a ticket and you slow down to 60 miles/hour, the trip is shorter than 4 hours. If you go only 40 miles/hour during the first hour, because of traffic congestion, and then you speed up to 60 miles per hour, it takes you longer than 4 hours. If someone just uses the speed with which you arrive at Durham to estimate your travel, the result will be 4 hours, either too short or too long for the last two examples, because the beginning of the trip was not taken into account properly.
Posted on:September 13, 1999 Part III
If we see
a star at large distance from us, we see it in the frame of the time here on
Earth. Let's assume we could stand on this star and look back at Earth in that
star's time. Which time is correct? Is it the time we are in?
Time is always
defined by a measurement made at the location of the observer, i.e. by
the time piece of the observer. There is no such thing as "the correct
time". To make sure that two observers in two different locations are
talking about the same time, they will have to synchronize their clocks
by passing the time information to each other (of course, they must take
into account that the information [by radio waves or light] takes some
time to get there). Normally this is not such a big problem, because time
passes by at the same rate for all observers (if nobody is traveling really
fast). This changes only, if one the observers travels at a speed that
is a substantial fraction of the speed of light. Then time passes by slower
for the fast traveler.
Posted on:September 13, 1999
I was wondering
if there was any specific outline that you wanted for our term paper,
i.e. length, specific aspects to be included, format, etc. I was just
wondering if this information could be found anywhere...
We have now
included the Outdoor Lab Manual on the www page, which includes a discussion
of the Term Paper requirements. Special links have been established to
the Term Paper requirements from the Syllabus and the News page.
Posted on:November 9, 1998 Part I
On p. 110
of Kuhn's text (viz., "close up"), he writes: Light is not like this,
and we cannot classify it simply as a wave or a particle. Instead of saying
what light is, we talk about how light acts. Here, then, we have an example
in science where a new theory has not replaced an older one, but rather
the two conflicting theories coexist to give us today's description of
an important part of nature (Kuhn 1998, p.110).
This goes
at the heart of the "wave-particle dualism" in physics. It is not a question
of either or, but of coexistence. There are some experiments tha tell
us: light is a wave, and others in a similarly clear way: light in particles.
This only seems conflicting, in Quantum Physics it is not. The wave and
the particle are the two projections that we "see" when we test light
with our experiments. We cannot see the full "3-dimensional" (Analogy!!)
picture of light, as it is! We can only come up with a mathematical model
that has both aspects. That is what Kuhn means. Refer to the section about
that in my Lecture Notes (in Chapter VII, with the spectral lines and
Bohr's Model).
Posted on:November 9, 1998 Part II
The latter
part of the passage above seemed quite interesting, especially in relation
to the philosophy of science. I take it, then, that simply because a better
theory of light exists, say, particle theory, it does not simply replace,
or reduce, the older wave theory (could you provide some references in
regard to the nature of light and coexisting theories)? Moreover, could
you provide a couple of examples (maybe from physics) where more sophisticated
theories of a given phenomena, do not reduce less sophisticated theories
of the same phenomena?
It is not
the question of a coextince of two theories, there is only one: Quantum
Theory, and that contains both wave and particle! In fact, it requires
both for light and for all particles (electrons, protons etc.).
Posted on:October 6, 1998
I have a
question concerning the homework that is due on Monday. Question 5 asks
for the length which a star rises in the SE above Durham is in the sky.
Going through the steps, I think the answer is shorter than 12 hrs. But
I think I remember that stars in north declination are up for more than
half a day. Does this vary according to where the star rises or am I making
a mistake somewhere?
You did arrive
at the correct answer going through the steps. In fact, a star that rises in
the SE is at southern Declination. This can be seen, when one compares this
with the behavior of a star on the Celestial Equator (i.e. at 0 Degrees Declination).
Such a star rises due E and sets due W. Therefore, a star that rises SE must
be south of such a star, i.e. at southern Declination, which, of course, leaves
this star up in the sky over Durham less than 12 hours.
Posted on:September 28, 1998
I understand
the concept of the moon's gravitational field creating the tides in the
earth's ocean and vise-versa. But why then is the difference in water
level at high tide and low tide approximately 12 ft here in NH, when the
difference in water level is approximately 16 feet in Nova Scotia, and
only about 2 or 3 ft in Bermuda? Does it have to do with the path of the
moon about the earth? Or the fact that the earth is not perfectly round?
: The effect
of the tides on the overall water level of the oceans is relatively small
(of the order of what you find in Bermuda, islands in the ocean!). The
higher difference in the tides at other places has to do with the coastlines.
A coast will in general lead to higher tides, because the water has nowhere
to go and gets stopped, or when it runs away at low tides no water comes
from the coast. The most dramatic case though is the Bay of Fundy, where
you find tides that exceed even 60 ft! The bay is a funnel into which
the water gets piled up. On top of this you may also get effects from
the wind. If the wind blows into a funnel shaped coastline, this leads
to even larger tides.
Posted on:September 28, 1998
If the planets
have angular velocity around the sun, then our entire solar system must
have torque. right? Could you illustrate this sometime? It's hard to envision.
I guess this
is a mix-up between "Angular Momentum" (any rotating or orbiting object has
this!) and "Torque" . Torque is the equivalent quantity to a force, when we
discuss rotation. Torque is defined as: Force x Distance from the center (Applying
the same force with a longer lever increases the applied Torque) So, you need
Torque to change a rotational or orbital motion. Or in other words: Torque changes
the Angular Momentum. As the Angular Momentum of the planets remains constant,
as we discussed in class, there is NO Torque involved.
Posted on:September 16, 1998
I want to know if
it is essential for us to bring our books to class. Some of my other teachers
require it but others have said that we won't need them IN class. I would
like to know because it makes my bag a little lighter if I know I don't
need it.
You don't need the
book in class. I ask you to bring the Syllabus and the Course Review.
If you bring the Syllabus, you can mark up the reading assignement for
the next class, as I show the respective page on a viewgraph. The Course
Review may help you in some of the activities, and you may highlight important
things said in class or add remarks that you don't seem to find in there
and you feel you should remember. There is no need to copy down everything
that I say in class, since a lot is in the review.
