Revamping Intro Physics Laboratory - Part 3

OK, I haven't forgotten this yet.

To me, the biggest problem with the current structure of intro physics lab is that we give students a list of things they have to do and measure, and hand-hold them into getting the result. In other words, they don't have to think too much to complete the exercise. They may have to do a bit of thinking and understanding of physics to complete the write-up, but the actual part of performing the experiment requires simply the ability to follow instructions.

I believe that we should have a more open-ended experiment to be given to the students. So I'll give an example. Note that while thing is something that I've thought about for a while, I'm still writing this off the top of my head. So there may be other problems with it that I haven't carefully considered.

Give them a problem to solve such as something like this:

Construct a pendulum clock. To make this clock useful, it would be helpful if the pendulum can swing back and forth once as close to 1 second as possible. Then each complete oscillation will take just one second. That way, this clock and measure time in increments of one second. You may use a stop watch to calibrate your pendulum to verify that it makes a one-second swing. Try to build this as accurately as possible. You must describe in detail in your lab report how you accomplish this task and why you chose to do it this way.

Now, as apparatus, give them a length of string, a set of weights, and a stop watch, plus other necessary items for them to be able to mount the pendulum on something.

Here's what I expect to occur. You'll have some students doing this by trial-and-error. They'll mount a length of string, and then start changing the weights to change the period of oscillation. Of course, there's no guarantee here that there is JUST the right weight for that length of pendulum to produce a 1-second period of oscillation. So students doing it this way may face a problem, but that's OK, because at the end when we discuss on to do such a thing, they'll discover why their technique isn't the best way.

You'll also get a bunch of student who would use a fixed weight, but tries to vary the pendulum's length. Again, they may try this simply by trial-and-error, adjusting it a little bit at a time until the period is close to 1-second interval. This technique is of course, more "refined" than the earlier one, since there's a high possibility of getting the right period.

Of course, what should be done, rather than simply doing a trial and error method, is simply to use a fixed weight, then measure a set of period corresponding to a set of pendulum lengths. Using the table, one can plot period versus lengths, and from there, interpolate (or extrapolate, depending on the range of lengths that were used) the exact length to produce a period of 1 second can be read off. So after the experiment is done and the students write their report, the lab instructor can start a discussion on the best possible technique to get the most accurate result. One can even make it a bit more complicated and ask the students how accurate is their clock as they let it swing for a length of time. This is where if they constructed a clock that swings over a large angle of oscillation, they may discover that it doesn't keep time very well.

What this type of lab forces them to do is think on the relationship between two measured variables. The first group had to figure out how the period changes as they change the weights. The second group is finding out the relationship between the period and the length of the pendulum. There may be a 3rd group that may be changing both the length and the weights simultaneous. If they do, and they're doing this by trial-and-error, god help them! :) But no matter what, the students are forced to think of what to do, and why they're doing it, to accomplish the task. They are not told how to do it. The experiment and the equipment give are familiar enough to them that this isn't something out of the ordinary. In fact, when they were kids, they probably played with something like this. The curiosity with finding how to do things is the purpose of the lab exercise. It is really playing, it is just that now, they have to think on what they are doing, why they are doing it, and how to present it in writing.

Next time, I'll try to present another possible laboratory exercise along this line.

Zz.

New Video on "Dark Matter" With Teacher Notes to Benefit Students, From Perimeter Institute

Hum.... a video on "dark matter" for high school students? With teacher's notes?

I haven't seen this yet, but this was the press release from the Perimeter Institute on something they are producing. If you have time and want to view it, you can directly go to this link.

Tell me what you think after viewing it. Do you think this can be an effective tool to introduce dark matter to students at that level? Would the teachers be able to understand it, even with the teachers guide?

A More Accurate Clock, and Fine Structure Constant Isn't Changing

Talk about killing 2 birds with one stone.

A new paper out of physicists from NIST has managed to accomplish to very important task. The first is the use of an optical clock that is way more sensitive and accurate than the atomic clock. Secondly, due to the highly sensitive and accurate nature of the clock, they have shown essentially that the fine structure constant isn't changing over time.

I wonder if the J.K. Webb camp will be responding to this report....

Zz.

Review: The Mystery of the Missing Antimatter

This is a book review of Helen R. Quinn and Yossi Nir's "The Mystery of the Missing Antimatter". As the reviewer has noted, there are only 3 major mysteries in cosmology today: the nature of Dark Energy, the nature of Dark Matter, and why matter dominates antimatter in our universe today.

This might be something I might try to get in the next few months. Helen Quinn, if you've read this blog for any considerable period of time, wrote a while back an article that I had characterized as something all scientists and science students must read. So she certainly has a clarity of thought and a concise use of words.

Zz.

'Expatriates' From Physics Careers Find Funding, Fulfillment in Medicine

I think the field of Medical Physics has not been getting enough publicity among incoming students, which is too bad considering the graduates from this field continually fetch good starting salary and continue to be highly sought after.

This news article highlights the migration into Medical physics by students who suddenly face funding shortage and cutbacks. Considering the economic outlook especially in the rest of physics, these setbacks may be a blessing for these students going into this field of study.

Zz.

Bill Foster Wins Election

It's no secret that I've mentioned about physicist Bill Foster campaign to win the House of Representative seat vacated by Dennis Hastert. He has done the upset and won the special election yesterday against Republican Jim Oberweis. So we have another physicists in Congress.

Unfortunately, this is only to serve the remaining term that was vacated by Hastert. We will have deja vu all over again this coming November when the two of them fight it out for the full term.

Zz.

The Wave-Particle Duality of Light: A Demonstration Experiment

Other than the fact that I don't quite like the title, this is an excellent demonstration paper that was published recently in AJP. Very much like the J.J. Thorn et al. paper on the which-way experiment, these profound phenomena can actually be performed in an undergraduate physics lab.

First, the exact citation:

T.L. Dimitrova and A. Weis, Am. J. Phys. v.76, p.137 (2008).

They basically performed a Mach-Zehnder interferometer experiment using very low intensity light so much so that only one photon is in the apparatus at any given time. They also have a second stronger laser beam that traverse the same apparatus, but slightly displaced that exhibit the clear wave-like interference pattern.

So far, this is fine and dandy, and it would not have caught my eye because it would be a nice, undergraduate physics lab exercise. But at they end, they did something simple, yet, can be quite profound to a student. I'll quote what they said:

The demonstration, whose result is astonishing for students, is realized in the following way. First the fringe pattern is locked to a photodiode as explained in Sec. IV B, and the photomultiplier is moved to a fringe minimum, as characterized by a low photon count rate which can also be displayed acoustically. If now path A of beam 1 is blocked inside the interferometer, it is possible to hear (and see) a distinct increase of the click rate. This result demonstrates that if we give each photon the choice of taking either path A or path B, it has a low probability to appear at the detector. In contrast, if we force the photon to follow a specific path by blocking the other path, then the probability to arrive at the detector is much higher. The puzzling fact that a two-path alternative for each photon prevents it from reaching the detector, while blocking one of the paths leads to a revival of the clicks, is most intriguing for beginning students. This experiment is well suited for illustrating this remarkable quantum mechanical effect, which can be explained only if we assume that each photon simultaneously takes both paths A and B; that is, each photon, in the phrasing of Dirac, "interferes with itself."

Gorgeous!

It is something we know would happen, but the way this is demonstrated is so clear that I would say this is an experiment worth doing at every undergraduate level. Well done to the authors!!

Zz.

Campus Ceremony Will Celebrate New Stamp for Physicist John Bardeen

I mentioned about the new US Post Office stamps set celebrating American scientists which includes a stamp of John Bardeen. Well, if you happen to be at the University of Illinois campus today (March 6), there is a small ceremony to mark the unveiling of the stamp.

The U. of I. physics department will host Urbana Postmaster Kathleen J. Burr, regional U.S. Postal Service officials, university administrators, and family and friends of Bardeen (1908-1991) at the ceremony. The event is free and open to the public. It will begin at 12:15 p.m., in room 144 of Loomis Laboratory, 1110 W. Green St., Urbana.

I can only hope that those who don't know much about him will now have the impetus to learn more about what Bardeen has done and how he has directly influenced how we live today.

Zz.

Follow-Up On Fredrick Seitz

I mentioned in a previous blog entry of the passing of Fredrick Seitz. Someone asked me why I didn't mention anything about his later-years opposition to Global Warming. After all, he was one of the more prominent skeptic of that effect.

I'm not sure why that would be relevant, frankly. The Fredrick Seitz that I know and admire came from his work on Solid State Physics. That was how he made his name, and that was how he became prominent. I'm sure he has his reasons for looking at the available data to be convinced that global warming isn't what it has been claimed. He's entitled to that. It's not as if he's supporting massive human extermination, which was the issue surrounding most German scientists during World War II.

So even though I don't agree with him regarding the issue of global warming, it remains a fact that he has a major influence in the field of solid state physics/condensed matter. Just for that, he deserves to be saluted.

Zz.

Frederick Seitz Dies at 96

The name "Frederick Seitz" should be very familiar to anyone who has studied Solid State Physics. Seitz is one of the instrumental figures in Solid State Physics and may even be one of its founding fathers.

This distinguished physicist passed away this past March 2nd, 2008. Our modern civilization, in no small part, has be shaped by his work.

Thank you, and rest in peace.

Zz.

The Best Years of Your Life?

It may not feel that way when you're embarking on pursuing your Ph.D, but it can be. This is an article from PhysicsWorld that reviews several students in the middle of their Ph.D program in physics. It has several good advices for anyone thinking of pursuing a physics Ph.D, especially if you are in Europe. This should plug some holes in my "So You Want To Be A Physicist" essay that essentially focused mainly on the US Ph.D program. Note the important difference between the US and UK/Europe program:

Having a research topic in mind is absolutely essential when applying for PhD positions in the UK and elsewhere in Europe, since you will usually begin working on your chosen research problem straight away. In the US, however, PhD students spend two years doing coursework and exams in all areas of physics and only then begin proper research.

“Most physics students in the US start their PhDs without a specific research field in mind,” says Jayatilaka. This adds at least an extra year to the process, but it makes the US a good option for those who want to learn a bit more physics before choosing an area to specialize in, or for students who want to undertake a PhD project in an area that they do not have much experience in.

Zz.

Journal Club For Condensed Matter Physics

This is such a terrific idea.

The Division of Condensed Matter Physics of the American Physical Society (APS) has sent out e-mail highlighting the existence of a "Journal Club for Condensed Matter Physics". This is where prominent physicists recommend papers and preprints that they find important, fascinating, or have a passion for. You get a more in-depth review of the paper/preprint, especially a discussion on the salient point being made.

I will include this link in the Blog's Physics Links collection.

Zz.

Physicists Successfully Store and Retrieve Nothing

This could easily fit in as an episode of the Jerry Seinfeld series.

It appears that there is such a thing as a "squeezed vacuum", and it takes some effort to store and retrieve this "nothingness".

To see what this is, begin with a normal light wave. Classically, this is a smooth wave of electromagnetic fields with equally spaced peaks and dips. But throw in quantum mechanics and things get more complicated. The precise height of the wave becomes uncertain, so the wave gets fuzzy (see figure). Physicists have learned how to manipulate that inevitable uncertainty--for example, making it smaller at the peaks and larger in between. That makes "phase-squeezed light." Now imagine turning down the intensity of the phase-squeezed light to zero. The wave itself goes away, but the waxing and waning uncertainty remains, creating a squeezed vacuum.

It's interesting that two separate groups produced work on this at almost the same time. This, of course, is not unusual, and PRL, Nature, and Science have been known to put such things in the same issue. It serves to reinforce the discovery.

Zz.

I'm Back!

I'm back from a short vacation. It was great to be away for a while, but now I feel so out of touch with what has been happening. So I'll need at least a couple of days to get back up to speed. Hope I didn't miss any earth-shattering "we found proof of aliens" or "convincing evidence for the mechanism of high-Tc superconductors" news.

Zz.

Barry Barish and the GDE

Barry Barish of Caltech heads the Global Design Effort (GDE) for the International Linear Collider (ILC). As anyone who has followed the news since December 2007, the ILC has had two major, and possibly fatal blow to its plan: the UK pull-out and the drastic reduction in funding in the US.

This is a good article on Barish and his effort within the GDE, including his take on the future of the ILC. I think most people kinda agree that even if the ILC gets built, it will probably be the last of its kind because the cost to go beyond that is no longer realistic. Unless new acceleration schemes that are currently still in basic, fundamental research stages (such as plasma wakefield, etc.), particle accelerator for high energy physics will probably not get any bigger than the ILC-like design.

Zz.

Theistic Evolution - The New Theology?

This is a rather fascinating article from, of all places, the Chicago Tribune. It detailed the "inquisition" being faced by a physicist at Calvin College in Michigan for a book that was published years ago. In it, Howard Van Till dares to propose that his religious belief can be reconciled with the evolution.

Van Till roused a small but fervent pack of enemies at the conservative college with his book, "The Fourth Day," in which he argued that the stories of the Bible and science's account of evolution could both be true. His critics on the school's board of trustees had no interest in reconciling the religious account of creation with a naturalist explanation of how life and the universe have evolved over the ages. For years after the book's release in 1986, Van Till reported to a monthly interrogation where he struggled to reassure college officials that his scientific teachings fit within their creed.

Now that's an interesting tactic.

I suppose that many people do accept both, and I suspect that there are a lot more of them than those who are reverently anti-evolution or anti-religion. This is because many people of faith accepts that what they believe in is simply a matter of faith - devoid of physical and empirical evidence, and they're willing to accept that. They still continue to accept science as the workings of the world that they live in. I don't see anything wrong with that kind of a "compromise".

But this attempt at reconciling religion (or in this case, Christianity) with evolution is certainly interesting. It does mean that many who accept both don't have to feel any discomfort for an apparent contradiction.

A good article!

Zz.

Revamping Intro Physics Laboratory - Part 2

So what is the main purpose of intro physics laboratory?

Keep in mind that MOST students in such courses are NOT physics majors. In fact, for many, these are the only physics courses they'll ever take. So I see it as the best opportunity to introduce to the students how physics actually work. How exactly do we consider something to be valid in physics? After all, anyone and everyone can come up with some "theory" to describe something (and in the age of the internet, everyone does!). How do we select which ones are valid and which ones aren't? It all comes down to experimental verification. How we know something to be valid come from our empirical observations. Therefore, proper experimental techniques must be crucial since it can determine what is valid and what isn't. This is where the acquired skills come in.

When I say "skills", I don't just mean physical skills, such as the efficient way of using an oscilloscope, or one's agility in soldering a piece of wire. It also includes mental skill, which is the ability to think through a problem, or a nagging feeling that something isn't quite right. It also includes the ability to know what is the best and most accurate way of doing something. For example, why can't a student simply make one measurement of the restoring force of a spring, make the corresponding measurement of the spring extension, and then plug those values into the Hooke's law equation to find the spring constant? Why do we have to make a series of measurements instead? The ability to know why we need to do that is an acquired skill in proper technique to test a particular relationship of two different variables. One acquire such skill after consciously and repeatedly learning ways to make such tests. However, the students need to be told that these are the skills they are being taught, so that they are consciously aware of what they are doing and why. So often, in the usual physics labs, this awareness is lacking and not being emphasized.

What the labs can do is reveal in a very direct way how we gain and verify knowledge. What exactly is the relationship between variable x and y, and how do I test it? How do I know my result is valid? In the end, without one having to tell them point blank, they learn the difference between "scientific evidence" versus other forms of evidence, and they get a glimpse of some form of what people like to call "the scientific method". Considering that most of them will go on to do other things in life beyond just doing physics (or even science), I would think that this ability to have them understand what is involved in determining what is valid is something extremely valuable. This lack of understanding can easily be the cause of why people accept pseudoscience and other flaky ideas. That is why I consider these physics labs as extremely important not just in physics, but as part of a general education of the population.

Since I've already mentioned what is wrong with the current way of doing intro physics labs, I should put my money where my mouth is. What exactly should we do in such courses? In the next part, I will give an explicit suggestion on how to revamp these lab sessions.

Zz.

Webcast: Nobel Laureate on the History and Fate of the Universe, March 4th, 2008

Here's an announcement for the upcoming Honeywell-Nobel Initiative:

Honeywell will be presenting a Webcast – The History and Fate of the Universe – by Nobel Laureate Dr. George Smoot of the University of California, Berkeley. His talk will focus on the present status of cosmological observations and will make a forecast on things soon to come. It’s a big topic but one Dr. Smoot is well qualified to address.

In 1992, Smoot and his team detected and mapped tiny variations in the radiation from the early Big Bang. Gravity worked on these variations to grow the galaxies, clusters of galaxies and clusters of clusters that are found across the universe. For this work, Smoot was co-awarded the 2006 Nobel Prize in Physics.

Smoot will be delivering this lecture to the students and faculty of the Government College of Engineering in Pune Maharashtra, India on March 4th. A live Webcast of his remarks, as well as related content, will be available for viewing from Honeywell Science.

You can also find more information and details on our MySpace page.

Zz.

Revamping Intro Physics Laboratory - Part 1

I used to hate doing the lab in First Year college intro physics classes. It would be 2 hours of torture, and at that time, I didn't see the point. Unless things have changed, most students taking such classes would tend to feel the same way as I did. And I think this is a waste of opportunity to really get through to the students of THE most important aspect of science, and of physics in particular - the empirical testing of physical concepts, and how we arrive at our knowledge to accept something as valid. This is what separates science from pseudosciences (and even religion).

The problem here starts from the very beginning. When I was that freshman undergraduate, no instructor ever spent time explaining why the laboratory sessions are important, why it is crucial that we actually DO things, rather than just read or watch what is being done. No one was explaining to me the fact that the SKILLS that I could get out of the physics lab may turn out to be a rather important aspect of my education that transcends beyond just physics, but into other parts of my life. This means that it doesn't matter if you're a physics major or not, the physics labs can be quite beneficial as one progresses in one's education, career, and life. I strongly believe students should be made aware of this in no uncertain terms. The physics instructors must impress upon the students why doing these laboratory experiments is important, what kind of skills are being practiced, and why this is different than just sitting and reading. I would think that the students would at least become aware that there is a rational reason for forcing them to do such a thing, rather than just them being told that they need to do this for no valid reason.

When I was a lab TA years ago, I tried doing just the very thing. More than 3/4 of my students at that time were not physics majors, and I flat out told them that in the lab sessions, it was more important to pay attention to what they were doing, and reporting what they were doing, rather than the final "answer" or results that they were trying to measure. I was more interested in what they were thinking as they were doing the experiment, reporting accurately their observations, and if the results looked weird, to notice that they did look weird rather than just reporting the number and did not realize something was not quite right. In other words, I was more interesting in the doing of the experiments themselves rather than testing if the students understood the physics theory or idea that was being tested. I was more interested that the student acquire proper experimental skills. They can learn more effectively about the theory and principles in class. I wanted the lab session to be more "hands on" on how to think and conduct an experiment to measure something.

So already my philosophy in what an intro physics lab session should be was different than what I encountered during my undergraduate years. And after being in this profession for many years, and being an experimentalist, I am even more convinced that this is what such lab sessions should be.

Zz.

Unitarian Physicist to Speak on Separation of Church, State

This is a piece of news announcing a speech by a physicist. It would have been a rather innocuous announcement, except for one, historically-important fact about the person delivering this speech.

Schempp, a Unitarian, was the subject of a 1963 Supreme Court case banning school-sponsored Bible readings in public schools. While a high school student in Abington Township, Pa., in 1956, he and fellow students were required by state law to read 10 Bible verses every day. He protested and was disciplined at school. He and his father, with the help of the American Civil Liberties Union, sued the school district.

I tell ya, even as a child, physicists can be a pain in people's butt, aren't they? Still, I'm proud to know that a physicist (or in this case, an eventual physicist) was the one responsible for this. :)

Zz.