Physics
drorzel | October 9, 2009Inspired by yesterday's post about the speed of light, a poll about c:
What do you think of the speed of light?(surveys)
So, how do you feel about the speed of light?
drorzel | October 8, 2009A couple of days ago, I answered a question from a donor to the Uncertain Principles challenge page in this year's Social Media Challenge (we've raised $1,807 thus far-- thank you all). If you'd like a question of your own answered on the blog, all you need to do is send me the confirmation email for a donation of at least $20, and your question.
The donor from the other day, Lauren Uroff, had a second question as well, also on behalf of her teenager:
He's an avid Discworld fan (where the speed of light seems to be variable) and wants to know what would happen in our real world if the speed…
drorzel | October 7, 2009Prompted by working on lecture notes for Quantum Optics last night, a Dorky Poll about the mathematical formalism of photon number states
What's your favorite photon operator?(polls)
I know it's hard to pick, but choose only one.
rallain | October 6, 2009Many textbooks are pumped up about Newton's 3 laws of motion. For me, not so much. First, (as many other's point out) these are really Newton's ideas about force. Second, the first law is pretty much a special case of the second law. Here are the first two laws (in my words):
Newton's First Law:
The natural state of an object is constant motion.
Yes. I know that is not how it is normally written.
Newton's Second Law:
The rate of change of an object's speed is proportional to the amount of net force on the object and inversely proportional to the mass of the object.
This could also be…
ejohnson | October 6, 2009With high speed photography, I can use a high voltage spark to create a flash of only 1/1,000,000th of a second in duration. The problem is that there are not a lot of things that move this fast that such a flash is required to stop the motion. Bullets are such a subject requiring a very high speed flash system. Around the lab we jokingly call this "ludicrous speed". After photographing bullets hit just about every conceivable object it is time to move on to other subjects. In this case a paint ball is sent into the edge of a straight razor blade. The paint ball crosses two optical…
esiegel | October 6, 2009You're sweet as a honey bee
But like a honey bee stings
You've gone and left my heart in pain
All you left is our favorite song
The one we danced to all night long
It used to bring sweet memories
Of a tender love that used to be
Now it's the same old song
But with a different meaning
Since you been gone --The Four Tops
Those of you who've been with me since the start of our current series on Dark Matter, including parts I, II, III, and 3.5, know that I'm a big proponent of dark matter. I think, based on everything that we know, that it is the simplest, easiest, and most likely explanation for…
rallain | October 6, 2009You know I like demos, right? This one is quite fun to do even in a class. The basic idea is to take a bucket of water and swing it around in a circle over your head. Simple, but if you have never done this one, it can be a little intimidating. Here is an example.
Water Demo from Rhett Allain on Vimeo.
So, how does this work? What does it show? Really, the question is: why doesn't the water fall out of the bucket?
First, I like to talk about "fall" what does that mean? I guess that means that the object has a downward gravitational force, but no force upward to give it a zero…
drorzel | October 6, 2009We're six days into the DonorsChoose challenge, and at the time of this writing, ten people have contributed just over $1,700 to the Uncertain Principles challenge entry. That's an impressive average, and I thank you all for your generosity.
I also offered a number of incentives, and Lauren Uroff is claiming one:
I'd like to take you up on your offer to answer questions. The first question I'd like help with is telling me how to tell my teenager about wave-particle duality, the classic experiments that show light is both a particle and a wave, and why he should care.
As It happens, I have…
pontiff | October 6, 2009Israel Gelfand, one of the great mathematicians of our age, apparently passed away yesterday at the age of 96. Check out the list of results that bear his name on the above linked Wikipedia page. Wow. Today I will, in his honor, think a bit more about Gelfand-Tsetlin basis and what they can be used for in quantum computing.
pontiff | October 6, 2009The Nobel Prize in Physics for 2009 has been announced and goes to Charles K. Kao for "for groundbreaking achievements concerning the transmission of light in fibers for optical communication" and to Willard S. Boyle and George E. Smith for the "for the invention of an imaging semiconductor circuit - the CCD sensor."
I'm crazy busy so don't have time to comment on the physics of these awards at the moment, but the thing that struck me about this selection will probably strike a few others and can be summarized in two words: Bell labs. Boyle and Smith are retired from Bell labs which is…
drorzel | October 6, 2009The sneaky folks at the Nobel Foundation have thrown a spanner in the works when it comes to the Physics prize. All the speculation has surrounded exotic quantum effects and theoretical esoterica, and they turn around and give it to something -gasp- practical...
The 2009 Nobel Prize in Physics is split three ways: half to Charles K. Kao "for groundbreaking achievements concerning the transmission of light in fibers for optical communication," and the other half to Willard S. Boyle and George E. Smith "for the invention of an imaging semiconductor circuit - the CCD sensor."
Now these aren't…
drorzel | October 5, 2009In this week's issue of Publishers Weekly there's a short review (scroll down) of How to Teach Physics to Your Dog (which will be released December 22):
How to Teach Physics to Your Dog Chad Orzel. Scribner, $24 (288p) ISBN 978-1-4165-7228-2
What do dog treats and chasing squirrels have to do with quantum mechanics? Much more than you might imagine, as Orzel explains in this fun introduction to modern physics based on a "series of conversations" with his dog Emmy. Dogs make the perfect sounding board for physics talk, because they "approach the world with fewer preconceptions than humans, and…
rallain | October 4, 2009There were a couple of things that bothered me about the MythBusters' myth where they fired bullets in the air. The myth was that a bullet fired in the air could kill you. The first problem is that it is not a myth. There are several reported cases of people being killed from bullets that were fired in the air. The Mythbusters tested this by finding out how fast a bullet would be going if fired straight up. A couple of problems:
First, they measured the terminal velocity of a tumbling bullet, not a spinning one. I really don't know how long a bullet will stay spinning, but I guess this…
drorzel | October 2, 2009Via His Holiness, there is an aggressively stupid paragraph in a New York Times movie review today:
Did you hear the one about the guy who lived in the land of Uz, who was perfect and upright and feared God? His name was Job. In the new movie version, "A Serious Man," some details have been changed. He's called Larry Gopnik and he lives in Minnesota, where he teaches physics at a university. When we first meet Larry, in the spring of 1967, his tenure case is pending, his son's bar mitzvah is approaching, and, as in the original, a lot of bad stuff is about to happen, for no apparent reason.…
drorzel | October 2, 2009I'm teaching my Quantum Optics class again this term, out of a completely different textbook than last time around-- I'm using Mark Fox's Quantum Optics from the Oxford Master Series in AMO Physics, which is more of a regular textbook. I've got six students-- four junior and senior physics majors, one senior chemistry major, and a retired scientist from GE who is interested in catching up on the latest new stuff.
Last time around, I posted my lecture notes as I went through the class, but I've forgotten to do that thus far this term, here in the Freezing Hell of Lab Grading. So here's a big…
rallain | September 30, 2009This is really a lab that I have students do, but I am pretty sure they don't read this blog - so it is ok. If they are reading this, hi!
We have these projectile cannons that shoot small balls. In order to look at projectile motion, they need to first determine the launch speed of the ball. I have a great method for this. Basically, shoot the ball horizontally off the table and measure how far horizontally it goes. You can get the final location of the ball by having it hit a piece of carbon paper on top of normal paper. If you don't know what carbon paper is, you are young.
Anyway,…
esiegel | September 30, 2009Many of you saw the pictures I posted Monday of colliding galaxy clusters. These pictures were spectacular, because they not only show galaxy clusters less than 200 million years after a collision (which is short, cosmically), they also show where the mass lies (traced in blue) and where the X-ray emitting areas are (pink). You get pictures like this one from the Bullet Cluster:
This one from MACS J0025:
And this one from Abell 520:
This is what happens when clusters collide, the normal matter gets separated from the dark matter! Let's tell you how.
Some normal matter is packed together in…
rallain | September 28, 2009I think we are entering a new era. An era where it is quite simple to find and get great videos. Oh, just saw a great tackle on the TV? In the old days, you would have to get that video off the TV yourself. Not anymore. Welcome to the interwebs. Also, the quality is awesome compared to 10 years ago. Here is the video. Yes, I know this is from several weeks ago - I am slow. Also, thanks to the person that put this on youtube - I edited your clip to remove the music and just look at the one collision. You did a good job though.
In terms of video analysis, this isn't too bad of a video…
ejohnson | September 28, 2009
I have photographed jugglers several times in the past for physics text books. I have been impressed with the level of skill some jugglers can obtain. It is difficult enough to juggle three balls, four is more difficult, and fire is a another story. When objects move in a circle they can undergo some fairly complicated motions. What would be the best way to show this motion in a still image?
In this case the camera is panned by the juggler at a constant rate on a computer controlled pan head. When the juggler is about the center of the frame a flash is set off. The image…
drorzel | September 28, 2009It's that time of year again, when the Nobel Prizes are announced-- the official announcements will be made starting next Monday. And, as usual, people are speculating about who will win, on both an amateur and professional basis.
Meanwhile, as we've done in the past, I will offer a valuable prize to anyone who predicts the winners of any of this year's Nobel prizes:
Leave a comment on this post predicting the winner(s) of one of this year's Nobel Prizes. Anyone who correctly picks both the field and the laureate will win a guest-post spot on this blog.
Rules and conditions are the same as…