Proposals

Another thing that Professor Greenside shared with us through the Adopt-a-Physicist Program was about proposals. When he first mentioned it in the forum, we thought that the proposals that he was talking about were no different from the research proposals we have done at school as our projects. He explained that these proposals that scientists like him work on are different from what we expected and are very important for a scientist for him to continue his research work.

Professor Greenside also shared with us that scientists like him submit proposals on a regular basis, in his case, every three years, to national scientific agencies such as the National Science Foundation, the Department of Energy, and the National Institute of Health. Each proposal that will pass the agency's panel of reviewers will earn him $300, 000 or more which will be used for funding his research work and sustaining his family's needs. However, there are also some times when his proposals get "rejected" by an agency. But according to Prof. Greenside, having his proposals rejected once in a while is only natural for a scientist like him because this means that the scientist is being innovative and is trying something new.

Here is an excerpt of our conversation with Prof. Greenside regarding proposals:

"In the United States, scientists need to obtain funding to support their research. They obtain this funding by submitting proposals to national agencies like the National Science Foundation, the Department of Energy, and the National Institute of Health. These proposals are carefully evaluated by a panel of scientists and the best of the proposals are awarded money; the other proposals are simply discarded.

A proposal will typically support the needs of a scientist for about three years, in some cases up to five years. The money is used to pay for graduate students, postdocs, experimental equipment, summer salary for professors, travel to conferences or for collaboration, and to pay journals for the cost of publishing papers. Typical proposals would request between $200,000 to $1,000,000 over a period of three years, depending on how big the project is.

So basically as a scientist, I spend 3-4 weeks every three years writing a proposal that may be 15-20 pages long, and that is worth $300,000 or more if awarded. It is extremely difficult to do science without a funded proposal so writing successful proposals is an important aspect of being a scientist. "

~Henry Greenside

Neurobiology

The human brain is highly complicated and unique. It gives us the power to think, imagine, and decide. Moreover, it contains billions of neurons to perform such specific tasks like regulating body temperature, perceiving and interpreting sensations, and causing secretions of hormones. All of these were coordinated and controlled just by an organ weighing approximately 1.3 kilograms.

In our third year Advanced Biology Class, one of the topics we’d discussed was the human nervous system, the main component of which is the brain. Because of this, we have become interested in the human brain, its functions, and how it is able to control virtually every other part of the human body. Fortunately, Mr. Greenside also specializes in neurobiology - the study of the nervous system - and he was able to explain a few things about the human brain that were certainly new to us.

"All details about how brains work are poorly understood at this point, not just by physicists but by everyone, including neurobiologists. The parts of brains that are well understood tend to be the parts of brain that are involved with input (the neurons that convert sound, light, chemicals, touch, etc into signals that the brain can understand) and with output (so-called motor neurons which directly connect to muscles and that cause the muscles to contract). But once you are more than about two neurons deep into the brain, when each neuron is in contact with 5,000 or more other neurons and all are actively transmitting information simultaneously, almost nothing is understood about how brains represent information or how they process the information. The situation is rather like chemistry before the discovery of the periodic table. People know a huge number of facts about brains: what happens if you destroy certain parts of brain tissue, what happens to behavior if you apply drugs or electrical stimulations to various parts of brains, how electrical activity of particular neurons correlates with stimuli. But scientists still lack a conceptual and theoretical framework to know which of these many details are important or central.

As one example of the difficulties involved, scientists still don't understand how memory works in any brain. They know from experiments that certain anatomical parts of brains called synapses, little micron-size nanomachines that connect one neuron to another, change their internal properties when an animal learns something new or when it forgets something, and all scientists believe that learning and memory is related to changes in synapses. (Human brains have a large number of these synapses, about 10^14 = 100,000,000,000,000, and that partly explains your ability to remember so much information.) But we don't know how brains read out the changes in synapses to actually extract a memory; we don't know the algorithm brains use to change the synaptic properties to encode memory.

So from one point of view, scientists studying the brain are educated guesses as to what might be happening, and we need to wait for (or help to develop) future inventions of new technology, and perhaps the invention of new kinds of mathematics, that will be able to confirm our guesses.

Still, there are experiments that strongly suggest what might be happening in some parts of the brain and there is enough experience in physics and mathematical modeling for people like myself to suggest plausible mechanisms. For example, ingenious experiments have shown that a part of a songbird's brain called "HVC" (high vocal center) has neurons that behave in an unusual way as a bird sings: each neuron is completely quiet until the song reaches a certain point, and then the neuron fires a brief 6 millisecond pulse of action potentials and then becomes quiet again. Different neurons fire their pulses at different times during the song and people believe that each part of the song is represented by at least one neuron. We don't know how these neurons are connected to one another or the purpose of the bursts they fire, but a simple guess that explains this sparse firing is that the neurons form a long chain, like a line of dominoes. When one neuron fires, it activates the next neuron in the chain and so on like dominoes falling over one after the other. My group has done mathematical calculations to explore the hypothesis that the neurons form a chain and our calculations show that a chain is compatible with the known experimental data, although only if extra assumptions are made which then suggest new experiments to try. For example, one can show theoretically that the chain, if it exists, can't be a single row of neurons, there has to be redundancy with multiple chains that are cross connected. This redundancy then leads to further calculations and predictions, e.g., what happens if you kill a neuron in the chain or what happens if you add noise via an electrical stimulus to a neuron in the chain, or what happens to the bird's song if you modify the chain in various ways.

It is not known but an extremely interesting question is whether human brains have something like HVC, which seems to be a digital clock that provides a high resolution time sequence with which one can organize various time dependent behaviors. One thing humans can do but songbirds cannot is speed up and slow down their speech at will (songbirds always sing their songs at the same speed). It is an interesting puzzle about how to set up a circuit of chains that would allow you to vary the duration of speech at will, or whether some completely different arrangement of neurons is needed to provide this capability."

~ Henry Greenside

The Scientific Truth Behind Spiderman 2

Spiderman 2 was undoubtedly fascinating – the characters, plot, and special effects in the movie were inarguably impressive. However, according to Prof. Henry Greenside, there are other parts in the movie (where Doctor Ock’s fusion device was involved) that had unfortunately made no scientific sense. Here are his several observations:

• Doc Ock would have to use deuterium-tritium fusion also, there is no practical alternative. But the nuclear reaction between deuterium and tritium produces a high-energy neutron and a working fusion reactor produces such a high intensity of such neutrons that all nearby life forms would be killed. There is no way that Doc Dock, Spiderman, Mary Jane or anyone else could get close to a fusion plasma and survive, especially without wearing any kind of protective armor. The only practical armor to stop a high intensity source of neutrons is several feet of concrete, not something a person could wear or walk around in. The need to protect against neutrons also explains why you won't be able to have miniature fusion reactors in a car (like in the movie "Back to the Future") or in your house, it is difficult to block high-energy neutral particles, you need a lot of shielding.

• The magnetic bottle that confines fusion plasma is extremely delicate, the smallest change in its properties will cause the bottle to fail and the plasma will be lost almost instantaneously (microseconds). So the parts of the movie showing the plasma wobbling around and even falling into a river were wildly unrealistic.
  
• It takes a lot of complicated big equipment and a lot of energy (tens of megawatts) to boost the temperature of a deuterium-tritium mixture up to 100,000,000 K, when fusion starts to occur. There was no evidence of such equipment in the movie, so how did Doc Ock actually get the plasma started? If the tokamak at Princeton were hooked directly to the power grid, it would knock out the power for most of the northeast part of the US. So what Princeton does is store energy over many days in eight big (15 m diameter) flywheels, and then use the energy stored in the flywheels to start the process of heating the plasma.
  
• The properties of the magnetic bottle change on microsecond time scales. This is way too fast and complicated for Doc Ock to respond to and correct the magnetic fields that confine the plasma, no matter how complicated those arms of his are. The control room of a fusion reactor is actually highly sophisticated, with tens of computers simultaneously changing the magnetic fields of hundreds of magnets that help to confine the plasma, and other computers analyzing data in realtime about the properties of the plasma (as measured by different kinds of laser and radiowave probes). No human being, or group of human beings, could process the data quickly enough nor adjust the hundreds of magnets quickly enough to control the plasma.
  
• The parts of the movie in which all nearby metal objects were being sucked into the plasma make no sense. The magnets that generate the donut-like magnetic field lines that confine the plasma have a special geometry; they are not bar magnets that would attract all iron objects towards them.

It is probably a good thing that the people who made the movie chose to ignore the physics, otherwise the movie would not have been so much fun. It is unfortunate that most viewers don't realize how wrong the science was.

The human race has nearly succeeded with the design of fusion devices. Physicists have created tokamaks that have created plasmas that exceed 300,000,000 K in temperature, kept the plasma confined for over a second, and generate several hundred megawatts of power. But they don't know yet how to create a reactor that can sustain a plasma for hours and that produces gigawatts of energy (the level needed to be practical), they also haven't solved the material science problems of how to reduce the damage to metal and concrete supports caused by the neutrons, they haven't worked out all the details of how to breed tritium fuel by having neutrons bombard liquid lithium that flows through the hole in the magnetic donut. But they have come impressively far, to the point where improvements by factors of three could lead to success.