Wednesday, May 4, 2011

Self Evaluation 3.

I feel like this blog evaluation period has pretty much been status quo. My second evaluation period was a major increase from the first evaluation, but I feel this period has been about the same as the second, but no better.

Post frequency: About 3 per week, sometimes 2, sometimes 4, but on average, 3. I've exceeded the minimum posts per week - about the same frequency as previous grading periods. This exceeds C level, but I don't think is A level according to the standards. I definitely could use improvement in this category.

Wrapping this up. Mostly.

Well, it's that time of year - the end of the semester. Except this time, I'm graduating! I'm approaching a busy summer - moving, traveling, and at the end, I'm getting married!

For those of you that didn't know, I've been writing this blog as a requirement for a class. I've also very much enjoyed writing it, but I may not have time to continue it, at least not in the detail that I'd like. I'll probably still post on this from time to time, but for the most part, you will not see too many more posts on this blog. Definitely if something new happens in the world of quantum mechanics, and I have the time, I'll add a post.

I'd like to time a moment to thank my readers, which were separated into two groups - the ones that had to read my blog (and others) because they were in the class, and the ones that wanted to. An extra special thanks to the readers that took the time to read my blog, even when it wasn't required!  I'd also like to thank Mr. James Redford for a LENGTHY discussion about Tipler's theory of everything - it was my first real blog debate I had.

It's been great, and I hope to see you all around, but for now, good bye!


I'm going to discuss yet another strange prediction of quantum mechanics - quantum tunneling. This effect allows scientists to image very tiny objects (atom sized objects) via a device called a scanning tunneling microscope (like the image to the left). That image is several atoms arranged in a ring, those bumps you see are the atoms! I direct you to Nano Nook for another example image.

So what is quantum tunneling? Well, think back to the potential that goes into Schrodinger's equation. Speciffically, I want you to consider a potential that looks like this.

You can visualize this like two hills that are sitting next to each other. Image you're sitting in the valley on the left, but you haven't eaten all day an you're exhausted. All your friends are waiting in the valley to the right, but you can't get there! You don't have enough energy! Well, this is the classical physics way of looking at things - no matter how hard you try, you don't have enough energy to make it up and over the hill.  Well, quantum mechanics says, you don't have to! Since your wave function extends in space, a small part of it overlaps with the other valley! What does this mean? There's a finite chance that you could be in the hill to the right! This is what quantum tunneling says, and this effect has been measured and is currently used a device called the scanning tunneling microscope (as well as MANY MANY other technologies.) Here's a gif I stole from wikipedia that shows this happening... sadly I didn't have time to make a simulation of my own.

Here you see a quantum particle penetrating a wall.

So how does the scanning tunneling microscope work? It's actually reasonably complicated, but the basic principle is as follows. A tungsten tip is held above the surface that you wish to image. There is nothing but vacuum between the tip and the surface, so normally, there's nothing to allows the electrons to flow to the surface. Fortunately for us, there's a finite probability that the electrons will "tunnel" to the surface, and this effect allows us to image the surface to extreme detail. Pretty cool, huh?

Not quantum, but I couldn't resist.

General Relativity, the theory of gravity that has existed since the early 1900s has been exceptionally difficult to prove. Early in the 20th century, several of it's major predictions have been proven, but it has taken a while to prove it's most basic predictions.

General Relativity treats time and space as interwoven (ever hear the term, the fabric of space-time?) and describes gravity as the curvature of space time. It's a very complicated and sophisticated theory - much too difficult for me to explain in detail.

Gravity Probe B, a NASA project to test General relativity was sent into orbit to measure the unconfirmed effects of GR. These were the geodetic effect (how objects curve space-time), and the frame dragging effect (essentially, the motion of an object around a rotating gravitating object is different than predicted by Newtonian gravity). Well, the geodetic effect was confirmed to an uncertainty of less than 0.5% in 2008, but what about the frame dragging effect? This effect is TINY, and requires extremely precise instrumentation. Well, NASA just released results that confirm the frame dragging effect to an uncertainty of less than 1%

What does this mean for you? Well, as it turns out, there a technology that many of us use every day that uses GR. That's GPS. GPS is already incredibly accurate (a couple of centimeters!), but these new advances may improve  the accuracy even more, allowing even better positioning. Being able to accuracy located objects from space is extremely important and has widespread applications.

I'm excited, I'm a big fan of General Relativity and an very excited to see this effect finally proven!

NASA on Gravity Probe B

Tuesday, May 3, 2011

Potentially exciting news in the world of particle physics!

This happened about a month ago, and I've been doing some reading in my spare time about it, but I think now's the time to make a post about it.

It's big news for particle physicists, but I doubt you've heard this on the evening news. The Tevatron particle accelerator at Fermilab in Illinois has data that potentially points to the existence of a NEW fundamental particle.

Currently, physicists describe all the fundamental interactions in nature (except for gravity) by something called the Standard Model. It's done well for the time it's been around, but most physicists believe it's incomplete. Fermilab may have found proof of this.

A particle accelerator is a large device that sends two beams of charged particles in opposite directions. When these beams collide, the particles in the beam break apart and energy is released. This energy sometimes reforms into different types of particles, and the rules governing this are contained in the Standard Model.

Take a look at the graph above. The red line is what they would expect to see with the collisions they were doing. The black dots are the data collected. The blue line is a curve fitted to the bump in the dots - this is what they are excited about. Because that bump isn't predicted, it could mean a new particle previously unknown to physicists!

Of course, there's another possibility - this is statistical deviation from what we expect. The probability of this being the case is about 1 in 45. I like those odds, but they are far from conclusive. Only time will tell! This problem looks like it will be solved in the coming months by data collected at the LHC in Switzerland and France.


Friday, April 29, 2011

Schrodinger's cat - is the paradox gone?

For a long time, Schrödinger's cat has been everyone's favorite example of quantum mechanics. Who doesn't like cats (aside from the people that don't)? It's become an icon for quantum mechanics, but a new proposal for an experiment may expose the cat while he's in the box. This preprint, due to be published in Physical Review A. Remember my post about the quantum drum? If you don't here's a quick summary.

Physicists put a 30 micrometer (human hair is about 100 micrometers thick) long piezoelectric paddle into a quantum superposition state - it was vibrating and not vibrating at the same time. As soon as they measured it though, its wave function collapsed to either of the two states, but some careful measurements showed that it was truly in a superposition state.

Hear is where the story gets interesting. Some physicists aren't satisfied with this, and want to take it a step further! What if we can make a measurement of the drum while it's in a superposition state without causing it to collapse? This is precisely what they are trying to do. Physicists Kurt Jacobs, Justin Finn, and Sai Vinjanampathy propose an experiment with an isolated wire put into a superposition state (vibrating in opposite directions - at the same time). They aren't stopping here, however. They wish to track and control the quantum state without collapsing the wave function. If they can achieve this, this would be revolutionary in quantum theory in general, and more specifically quantum computing. Quantum computing can theoretically achieve computational efficiency and speed leaps about bounds faster than current computers. Unfortunately, this experiment is a few years off, as the team doesn't have sensitive enough equipment.

Where does this leave Schrödinger's cat? Well if this experiment works as hoped, he'll be either dead - or alive - forever.

Be careful what you believe.

Being skeptical is a good thing for scientists, but when is it going too far?

We are taught to question what we are told, yet we are expected to accept whatever is taught to us in school. Are we supposed to just take in the knowledge and accept it as fact? Well, a little yes, and a little no.

Should we question everything, nothing would get accomplished - there's many many many lifetimes of research that has been done, and sometimes you have to accept things an trust that it was done correctly. Hopefully someone else will independently corroborate those results. Basically, it's perfectly okay to be skeptical about things, just don't take it to far. How far is too far? Well, take a look at this. For those of you not wanting to read, I'm going to post snippets here.

Basically, this guy says all the current mysteries of the universe, including quantum mechanics can be explained by "expanding mass". Load of crap if you ask me, and by the looks of it, he doesn't understand basic physics.

"...Can light from a distant source be simultaneously both a “wave of pure energy” and a “quantum-mechanical photon particle”, only physically “choosing” one or the other based on how it is later observed? Can a magnet cling energetically to a fridge against the constant pull of gravity, yet need no explanation for this endless energy? "

All experiments point to the first being a reality, but I understand his skepticism - it's difficult to swallow. The second sentence is what bothers me. He claims to accept the previously uncovered laws of physics, yet seems to be missing something. The first law of thermodynamics says that energy cannot be created or destroyed. That's precisely why a magnet sticks on the fridge. "Work," in the fundamental sense requires something be moved to a different potential energy, that kinetic energy can only come about by a change in potential energy. It just so happens magnets have greater potential energy for their size, and dominate gravity. No new energy is being added into the system. He's completely misunderstanding the fundamental laws of physics (which have NEVER been observed to be violated.)

So then he goes on to claim he can explain everything with a simple theory. Well based on what I'd seen so far, I wasn't expecting to find much, but I wanted to keep an open mind. You can read the whole article if you like, but I'm only going to highlight a few points he makes.

"Today we think of matter as passive lumps of mass..."

Well that's kinda redundant. Mass is understood to be a number associated with a type of particle. Just as an electron always has a +1e charge, so does an electron always have the mass of one electron - this hasn't changed, and his statement is dumb. Continuing his thought...

"... with various ethereal energy phenomena actively driving everything. But what if, instead, it is matter itself that is active – both atomic and subatomic matter – and there are no separate “energy” phenomena at all?"

That's like saying, "What if people don't move with their legs, what if their legs just move and intrinsically people move with them!"

Worthless. He then talks about his theory...

"The simplest example of this is a rethink of gravity, where all atoms actively expand very slowly and in unison. Nothing would appear any different over time, but standing on an enormous expanding planet means we would certainly feel this expansion beneath us – as a force pushing upward under our feet."

Okay, I'll bite. These atoms just continuously expand? Since gravity appears to be constant, they MUST be accelerating at a constant rate, and must have been doing this for a long time. In order for us to feel a force equal to that of gravity, they must be moving pretty damn fast, just according to Newton's third law of motion (If a body applies a force on another body, that body exerts an equal and opposite force on the first body.)

He presents no calculations, no testable predictions, he just says, oh this theory explains what we see! Obviously our current theories are wrong! It gets much worse.

I guess the moral of the story is, be somewhat skeptical, but be on the lookout for crackpots like this and take everything at face value. There seem to be a lot of people that think String Theory is proven and accepted - it isn't, it's got a LONG way to go if it's ever to be proven. But still I think people believe it is because they are not skeptical enough. Sorry, a little ranty and long winded, but that article bothered me. I honestly was surprised that was posted on that blog - they seemed more reputable than that.