Fermi National Laboratory


Questions and Answers from Virtual Ask-a-Scientist of December 18, 2003

More information about the program

Moderator
I'm Elizabeth Clements of Fermilab's Office of Public Affairs. Matt and Vivek are ready for your questions! Fire away!

Student
How can you calculate the spin of a particle ?

Matt Malek
Fundamental particles are divided into two types. Matter particles are called Fermions, and have half integer spin. Force carriers are called Bosons, and have integer spin. The spin itself is angular momentum.

MarchHare
What's "prarie preservation" about, and who takes care of the buffalo?

Moderator
Hi Marchhare, Fermilab has a great prairie restoration project. The site is 4800 acres, and we have 1100 that are restored prairie. It is really an amazing program. We have a herdsman on site who takes care of the buffalo. Once a year, a veternarian comes on site to give the buffalo a check up and give them their shots.

Student
I'm a student.

Vivek Jain
hi student, are you a college student, high school, graduate student?

Student
What are the Fermi-Dirac statistics & the Bose-Einstein statistics?

Vivek Jain
hi student, take a look at Matt's previous response about half-integer and integral spins.

Chilled
Hi. Can you tell me what the relationship between Sloan Digital Sky Survey and Fermilab is?

Matt Malek
At Fermilab, there are groups working on various projects. Sloan is one of the projects that the lab is involved with.

MarchHare
Is the Auger experiment online, or is it still under construction?

Matt Malek
Regarding Auger, when completed, the experiment will have 24 telescopes and 1600 water tanks, which will be used for detecting the highest energy cosmic rays... (MORE)

Chilled
Vivek--If you're with Brookhaven, why are you at Fermilab?

Vivek Jain
hi chilled, there are a handful of labs around the country where they have accelerators - Cornell, Brookhaven, SLAC, Fermilab, etc. My experiment is running at Fermilab, so I spend time here.

Matt Malek
Currently, six of the telescopes are operational and 150 of the water tanks are functioning in Argentina. The full construction is expected to be completed by the end of 2005. {MORE}

Matt Malek
Auger is designed such that each component (telescope or water tank) can be used to collect data as soon as it is deployed. So even though the full experiment is not completed, it is indeed online and collecting data. {ONE MORE}

Matt Malek
Even at its present size, the Auger detector is the largest detector in the world for ultra high energy cosmic rays

Student
What are the first and the second-order corrections of the time-independent, non-degenerate perturbation theory, and are they used for renormalization? Could you describe the time-independent, non-degenerate perturbation theory ?

Vivek Jain
hi student, I am an experimental physicist by training, which means that I don't actually deal with Hamiltonians on a daily basis. To answer your questions, I would have to look at some basic quantum mechanics books - that might be a good thing for you to do.

Don S.
When an electron and positron annihilate, mass is converted to energy, charge cancels and momentum is conserved by the pair of photons emitted in opposite directions. It seems that the tiny gravitational field associated with the mass should be accounted for as well. Is a graviton emitted or is the gravity associated with the mass accounted in some other way?

Vivek Jain
hi don, I am thinking about how to answer your question. give me a minute

MarchHare
Has Auger detected any rays? They seem to arrive so infrequently.

Matt Malek
The Earth is continually bombarded by cosmic radiation. Much of it is stopped by the atmosphere, but even at the surface there is constant radiation. (This is why certain neutrino experiments are placed underground -- to minimize the effects of cosmic rays] {MORE}

Matt Malek
As you look to higher energy cosmic rays, the rate at which they strike the earth drops very quickly. Each time you double the energy of the cosmic rays that you are looking for, the rate decreases by about a factor of eight. Auger was designed to detect cosmic rays with energies starting at 10,000,000 times that produced by the world's largest particle accelerator (at Fermilab). {MORE}

Matt Malek
When Auger is finished, it is expected to see about 3000 cosmic rays per year at these "lowest" energies, and about 30 per year at the highest energies. At it's current size, Auger has detected cosmic rays, though not too many so far.

Carraac
How do you smash atoms?

Vivek Jain
hi carrac, "smashing atoms" is a way to explain what we do. We can target protons into say a tank of liquid neon. The "size" of the protons depends on their energy - the higher the energy, smaller their size. Some of these protons find the nucleus and break it apart. We can do similar things with other particles, e.g., electrons on lead, copper, etc. more later

Vivek Jain
hi carrac, we "photograph" collisions in a variety of ways. In the old days, people used something called a bubble chamber. This was a chamber filled with liquid hydrogen, neon, or a mixture. When particles went through, they heated the track along their path and caused bubbles to grow (technically correct answer will take much longer to write) - these bubbles were photographed with a camera. In the modern days, we use electronic detectors. For example, we can have a cylindrical chamber filled with gas, e.g, a mixture Argon-Ethane. this cylinder has wires with high voltage (2000 V or so). when a charged particle goes through the gas, it ionizes it, i.e., separates the electrons from the nucleus. these electrons are picked up on some other wires, and produce an electrical signal - an electronic photograph.

Student
What are the mean lifetime of the "up" and the "top" quarks?

Matt Malek
The top quark decays extremely quickly -- the lifetime is approximately 10^-24 seconds, or about one trillionth of one trillionth of a second.

Don S.
This is a great site, my first time trying it out. Thank you for your time! Here is another question: Could you comment on the "size" of an electron. I've seen values of 10^-15 to 10^-18, or described as a "point" entity or a much larger particle (how large?) with an embedded point-like charge. Are quarks and electrons similar in size?

Vivek Jain
Well, we believe that particles like electrons are fundamental particles, i.e., they are not made up of anything else, so in a sense they have no size. IN contrast, protons are made up of quarks and have a size. We do experiments to break apart an electron, but have not succeeded. The numbers that you have seen correspond to the sensitivity of the experiments. Same answer for quarks.

conor
quick question: anyone here from university of chicago?

Matt Malek
Not here -- Vivek is from Brookhaven National Laboratory, and I work directly for Fermilab.

Don S.
No, I'm in the middle of Kansas.

MarchHare
With only 30 of the highest-energy rays per year, what scientific data can you get from that? Won't it take a long time for results?

Matt Malek
At the highest energies, only eleven cosmic rays have ever been detected. The detection happened at the AGASA experiment in Japan. Another cosmic ray experiment, HiRes -- in Utah, does not see any cosmic rays at the highest energies. {MORE}

Matt Malek
One of the goals of Auger is to resolve the possible discrepancy between these two results. Besides its great size, Auger's design makes it ideal for this purpose. AGASA detects cosmic rays by looking at the shower of particles that hit the ground. HiRes uses a telescope to look at the cosmic rays in the atmosphere. {MORE}

Matt Malek
Auger is a "hybrid" detector, with water tanks to look at the shower when it hits the ground, and telescopes to look at the cosmic ray as it moves through the atmosphere. So even with only 30 events per year, Auger may provide a definitive answer for how many cosmic rays there are at the highest energies. {MORE}

Student
What is the decay mode of the lambda particle that has a rest mass of 2281 MeV/c^2, whose quark constitution is udc?

Vivek Jain
hi student, take a look at http://pdg.lbl.gov

Matt Malek
Theoretically, interactions in space should cause cosmic rays to lose energy, so the question of whether or not they exist above a certain energy is very interesting. We think that above a particular "cut-off" energy, all cosmic rays are coming from the near universe, so if we see many of these cosmic rays, it provides a clue to where they are coming from.

Student
How can neutron stars be stable if neutrons decay over time?

Vivek Jain
hi student, free neutrons are unstable, not those which are bound. for example, most atoms contain neutrons, and Don S.
Speaking of cosmic rays, Is there any safe and inexpensive way to visualize cosmic rays? I give a talk to local students on meteorites every year and always wanted to show the kids something coming from the sky in real time. The alcohol-dry ice cloud chamber is too cumbersome (the talks are out on a farm) and not very impressive. I've heard of a "super cooled gel" to show tracks. Any ideas here?

Matt Malek
The simplest cosmic ray counter that I know of is just two geiger counters set up in parallel to each other. If a cosmic ray passes through perpendicular to the two, they will each get a signal. Random background will cause a signal in only one, and can be dismissed as not being a cosmic ray.

Burch
I am curious about spooky action at a distance, aka, entanglement of photons

Matt Malek
Sounds good -- is there a specific question that you have about entanglement? By the way, photons are not the only particles that can be entagled. E.g. electrons can also. Entaglement has interesting applications, such as quantum teleportation.

Carraac
What kind of classes should a kid take to be able to so what you do?

Vivek Jain
well, carrac, I did science in school, i.e., three years of physics, chemistry and math. In college, I majored in physics, and then did a Ph.D in particle physics. Are you in high school? I can answer better if I know

MarchHare
What does "how many" high-energy rays tell you?

Matt Malek
Right now, there are three big mysteries in cosmic ray physics. We have no idea what can cause a particle to have such high energy, we have no idea where these cosmic rays come from, and we are not sure what the cosmic rays are made of. {MORE}

Matt Malek
So experiments like Auger look to see if cosmic rays are coming from a particular direction, or if they come evenly from all directions. As for their composition, the two leading suspects are protons and iron nuclei -- because iron is the heaviest element made in normal stars and protons (i.e. hydrogen nuclei) are the most abundant element in the universe. {MORE}

Guest
could you guys explain force carriers. i dont understand how they can cause attractive forces and how they dont cause matter to just constantly decay away.

Vivek Jain
hi connor, this is a very good question. I don't have an easy answer for you. Here is something for you to ponder over while I think of one without resorting to jargon and math. The electromagnetic force, e.g., attraction between an electron and a proton, or repulsion between two protons is mediated by a photon. However, a photon itself has no charge - so how does it know whether to convey an attractive or repulsive force.

Matt Malek
Looking at how many cosmic rays there are gives us a clue of what to look for. If we know how many there are at various energies, that constrains what sort of astrophysical objects could be the source. We know a lot about what's out there in space and so the answer to "What causes cosmic rays?" has to be consistant with everything else that we know.

Don S.
Thanks Matt, I'll need to get a second counter but I understand the principle. Will I get many counts during a 1/2 hour talk? Is there an increased frequency of cosmic rays during sun spot activity?

Matt Malek
Depending on the size of your counters, you should get a count every few seconds, so no problem for your half hour talk. I'd recommend aligning the two counters horizontally, but if you can get two more, set them up vertically to demonstrate how most cosmic radiation is coming from above (the vertical counters will record far fewer counts)

Student
Can there be a baryon whose quark constitution is t t t ? If so, what would be its expected mass?

Vivek Jain
hi student, because of its heavy mass, the top quark is quite special. It decays before it has the time to combine with other quarks to make baryons or mesons. So, there is no ttt baryon.

MarchHare
What's quantum teleportation?!!

Matt Malek
Quantum teleportation, in its simplest form, involves two particles that are "entangled." Take electrons, which have a magnetic field similar to that of a bar magnet. If you place the electron in a magnetic field, its north pole can either point towards the field or against it. Entangled electrons used for quantum teleportation always have their north pole's pointed in opposite directions. {MORE}

Matt Malek
These pairs can be used for teleportation. Please keep in mind that in this teleportation, you are not transporting matter, you are transporting information. The spin state (i.e. magnetic pole alignement) of a particle is information. If you and I split an entangled pair of electrons, and we head far away from each other, I can use the entanglement to teleport the information of another particle's spin to you. I make a join measurement on a new particle and my entagled particle, and this measurement causes the spin state of the new particle to be teleported to your entagled particle. {ONE MORE}

Matt Malek
Although theorized for some time, quantum teleportation was first realized experimentally in 1997. It sounds fantastic, but it really can be done!

Burch
can you describe the method for causing to particles to be entangled in the first place?

Matt Malek
Sorry, Burch, but I don't know enough about the actual experimental side of quantum teleportation to be able to answer your question.

Student
Why is it that the Standard Model predicts 3 generations of quarks, no more and no less?

Vivek Jain
hi student, the standard model doesn't predict 3 generations. Nature seems to be telling us that there are 3 generations, and the standard model can accomodate that. If there were more, then they can be accomodated too. There are many papers in the literature which have worked out predictions based on four generations.

Student
What are "magnetic monopoles", and can they exist?

Matt Malek
Electric monopoles are simply any charged particle. The term "monopole" simply means that an electric field is emitted from the particle. In contrast, magnetic fields exist as dipoles -- there is a north and south pole. There is no such thing (that we know of) as magnetic charge. Magnetic monopoles would be magnetic charges, and they were postulated as a way of explaining why charge is quantized. However, years of experimental searches have not yielded evidence of magnetic monopoles.

Guest
what kind of experiments are being done to affirm string theory?

Vivek Jain
hi conor, string theory is at a stage, where it does not really have testable predictions. People are looking for it by searching for extra dimensions (other than the three space dimensions that we live in). I'll have to look up some papers to tell you exactly how they do these searches.

Student
What does it mean that space is isotropic?

Matt Malek
We believe that space is both isotropic and homogenous. By homogenous, we mean that the universe looks basically the same, no matter where you are -- there is no preferred location. By isotropic, we mean that the universe looks basically the same, no matter which direction you look in. Essentially, it is a way of saying that we aren't located anywhere special.

Student
What is the coupling constant?

Matt Malek
Actually, there are three coupling constants that we know of. The electromagnetic force, the weak force, and the strong force each have a coupling constant. The coupling constants are basically a measure of the strength of each force. The larger the coupling constant, the more readily the matter particles (fermions) COUPLE to the force carrier particles (bosons)

Don S.
Can you help me to understand the arguments for dark energy and matter? I've heard that it is related to the measured fluctuation in the cosmic background radiation. Also, the universe is expanding at a increasing rate-what is the evidence for this concept?

Vivek Jain
hi don, the argument for dark matter goes as follows. BY looking at the amount of light which is generated by a distant galaxy, one can infer a mass - if you were to fly over the US at night, and try and judge its population by the lights on the ground. You can also infer the mass of the galaxy by studying its rotation. One usually finds that the latter mass is higher than the former - the difference is referred to as dark matter. more about dark energy in a bit...

Burch
I found several extra dimensions of space on Google once, but when I went back the URL's had expired...

Vivek Jain
too bad you didn't publish when you had a chance ;-)

MarchHare
Do the people who work at the lab enjoy the buffalo, or do they ignore them?

Matt Malek
Hundreds (thousands) of people work at the lab. Since the buffalo are not constantly surrounded by admiring throngs, I would have to conclude that most people ignore them, or enjoy them only in a passive way. Personally, I really like working at a particle physics lab that has buffalo and other wildlife (e.g. deer), and have been known to take walks out to the buffalo field, or stop my car and get out to watch them.

Moderator
I think that people at Fermilab enjoy having the buffalo around, especially in the spring when they have our babies. Our neighbors certainly like having buffalo around and often stop by to visit them.

MarchHare
Do you know how the electrons remain entangled even after they're split?

Matt Malek
The entaglement of the electrons is a quantum state that does not require the electrons to be in physical proximity to each other. So the question of "how do they remain entangled" doesn't really apply. Disrupting the entanglement would require something other than separation, such as a magnetic field.

Burch
Any thoughts on my previous question about speed of interaction of entangled particles? Has any attempt been made to measure it to see if speed of light, or some other limit, applies?

Matt Malek
The entangled particles exist in one quantum state. So doing something to affect one particle also affects the other. The entire state is affected as one, so the interaction is instantaneous. Hence the term "teleportation"

Burch
Is there any indication that there is a transmission delay in the state change.. IOW if I took an entangled electron 10 light years from its partner and flipped its state, would the other react now, or in 10 years?

Matt Malek
The other particle would react now, not in ten years time.

Vivek Jain
hi don, re: dark energy. People have been doing experiments looking at distant galaxies and other objects like quasars, and they noticed that the results indicated that the expansion of the universe was accelerating. Similar indications have also been observed in the cosmic background radiation experiments. These have led people to propose the presence of an energy pervading the universe - for a lack of a better word, they call it dark energy.

MarchHare
Wow! What other spooky actions are there? (was that the term?)

Matt Malek
The term was "spooky action at a distance," and it was coined by Einstein. Outside of Halloween, I don't think that any other physics interactions have been explicitly termed spooky.

Matt Malek
Seriously, though, the reason it was termed spooky is because you can't see how the information is transferred. So, if you think about two separate particles, it seems spooky. The easiest way to understand it is what I said before: You are affecting a single quantum state.

Student
What is an isospin doublet?

Vivek Jain
wow, you seem to know a lot about particle physics! The six quarks (up, down, charm, strange, top and bottom) are arranged as three pairs (up, down), (charm, strange) and (top, bottom), or as doublets. An up quark can change to a down quark via the weak force (they exchange the W boson). Isospin refers to the mathematical struture of the weak force.

MarchHare
Dark energy sounds spooky. There's no reason thay named it that?

Matt Malek
Dark energy was given that name because we have no idea what it is yet. It was only discovered in 1998, though it was first hypothesized by Einstein long ago (who called it a "cosmological constant"). At present, our best measurements show that the universe is 5% visible matter, 25% dark matter, and 70% dark energy. So we really know very little of what is out there.

Burch
For reasons that are unimportant, I once tried to compute the Swartzchild (sp?) radius of the known universe based on some mass and radius numbers I found on the Internet. I came up with something that was close to implying that the universe is a black hole. Of course my physics is so rusty I could be all wet. Any thoughts on that possibility?

Vivek Jain
gee, you are a better person than I am - I would never dream of attempting to calculate the Schwartzchild radius of anything ;-)

Student
Is/Are there any particle process(es) that violate(s) CPT invariance?

Vivek Jain
none that we know of.

MarchHare
Is there some reintroduction of butterflies around the lab?

Moderator
Hi Marchhare, Last fall we tried to reintroduce the Silver-Bordered Fritillary to Fermilab's prairie restoration project. Unfortunately, the silver-bordered fritillary caterpillars did not survive the winter. This might be because the caterpillars were too mature. Snow provides a blanket for hibernating caterpillars, and we didn't have a lot of snow last winter which would have protected them. We will try to reintroduce the silver-bordered fritillary again though.

Moderator
Marchhare, Here is a Ferminews article about reintroducing the rare silver-bordered fritillary to Fermilab's prairie: http://www.fnal.gov/pub/ferminews/ferminews02-11-01/p3.html

MarchHare
So "dark" means unknown, not invisible or without light? Is all energy dark?

Vivek Jain
hi march hare. in this case, dark does mean unknown. well, all energy is not dark. for instance, when you see fireworks, the lights you see are a form of chemical energy, or the light from an electric bulb is electromagnetic energy. does this help?

Burch
Admit it, you just like typing the word fritillary...

Moderator
It's not an easy word to type! And I'm on a role tonight with typos! :)

Matt Malek
Student: Searches are being done for CPT violation. For instance, experiments such as Super-Kamiokande have shown that the three different types of neutrinos mix with each other. Other experiments, such as KamLAND, are looking at mixing between the three types of anti-neutrinos. The mixing depends on the mass of the neutrinos (or anti-neutrinos) and a mixing angle. If the results of these experiments show that the masses (or mixing angles) of neutrinos and anti-neutrinos are different, then that would provide evidence of CPT violation. None seen yet.

Matt Malek
MarchHare: For dark energy, the dark just means unknown. For dark matter, it means both unknown AND unseen.

Don S.
This question relates to one I saw in previous sessions. If I understand, virtual pairs of particles are continuously created and destroyed in "empty space". Is pair production influenced by external fields? For example, if an electric field is established between a pair of parallel plates, does the frequency of pair production change? How about a gravitational field?

Matt Malek
By changing the amount of energy locally available, external fields can enhance the pair production of particles.

Burch
It beats a poke in the eye with a sharp stick.

Matt Malek
It sure does!

Burch
OK New topic. My math days were double digit years ago and ended with calculus. Can someone give a simple definition of the term Manifold - the math kind, not the one under the hood of my car..

Vivek Jain
hi burch - my math years ended in graduate school, about 15 years ago, so we are at the same place. I don't know topology, the field of mathematics that deals with manifolds. Let me give you an example. In string theory, one usually has extra space dimensions. To bring this theory down to reality, i.e., to three space dimensions, one has to get rid of the extra dimensions. this is usually referred to as the compactification of manifolds. does this help?

Student
Why does the proton not oscillate?

Vivek Jain
why should it oscillate?

Burch
FWIW, there is a small wetland area outside my office window in Deer Park (about 30 miles north of Fermilab). It is amazing, the variety of wildlife that I see in there. From waterfowl, to muskrats, and a variety of birds. I can't see flutter-bys - too far even with the binocs.

Moderator
Wetlands are amazing. Fermilab also has a wetland mitigation project that is doing very well. It is very cool to work at a place that smashes protons and antiprotons and has such a large prairie restoration project.

Student
What are pseudoscalar mesons?

Matt Malek
Mesons are particles made up of a bound state between a quark and an anti-quark. Both the quark and the anti-quark have a spin (i.e. angular momentum) value equal to 1/2 of Plank's constant -- let's just call it 1/2. When bound together in a meson, the angular momentum can add to one (called a vector meson) or cancel out to zero. The case where they cancel out gives you a pseudoscalar meson.

Burch
I will accept that is is not a simple concept and move on

Vivek Jain
whew!

Student
The proton is a massive particle, and particles that are massive usually oscillate. However, for the proton, it does not appear so. Why?

Vivek Jain
what other massive particles do you know that oscillate?

MarchHare
Those butterflies (and caterpillars) are cool looking. Beside buffalo, what wildlife is popular?

Matt Malek
There are deer (drive slowly!), and more geese than you can shake a proton at! Then there are frogs and coyote -- and over 250 species of birds. I know people often think of physics labs as dull, dry, and boring... but Fermilab really is a beautiful place, and it is great to work here!

Moderator
The Birds at Fermilab site is at: http://www.fnal.gov/pub/about/campus/ecology/wildlife/birds.html

MarchHare
You can't shake a proton, they don't oscillate!

Vivek Jain
is that directed at me or at student ;-)

Burch
I realize the inherent danger in trying to relate physics concepts to everyday experience, and I'm not sure how to put this into a cogent question, but let me have a bash at it....

Matt Malek
Okay, give it a shot!

MarchHare
Matthew is shaking protons at geese. I think "massless boson" sounds like a great insult. Are there physicists' insults?

Vivek Jain
well, a massive boson can be a little more insulting ;-)

Student
For example, the electron neutrino can oscillate to become a muon neutrino. That's how they found out that the neutrinos were massive ( or rather, that's what the scientists told me during the previous session ).

Matt Malek
Actually, the initial discovery of neutrino oscillation (in 1998, at the Super-Kamiokande experiment) was of muon neutrinos disappearing. Now, we are pretty confident that they oscillated into tau neutrinos, not electron neutrinos. Later results have shown electron neutrinos oscillating to one of the other neutrino types. However, neutrinos are the ONLY type of massive particle that we know of that undergoes this sort of oscillation. Which is why neutrino physics is a very exciting section of particle physics right now.

Matt Malek
MarchHare: We know of 12 bosons right now. Eight are gluons, which carry the strong force, and one is the photon (i.e. light). All nine of these are massless. Only the W+, W-, and Z bosons (which carry the weak force) are massive. Do you consider calling somebody light to be an insult? :)

Burch
I know a physics joke... What's new?.... Photon energy over Planck's constant... Big yucks in freshman physics.

Vivek Jain
i guess I must be slow today ;-) took me a little while to get that one....

MarchHare
I don't know what a boson is, it just sounds like bozo. Calling someone an airhead is pretty bad. Light-weight bozo?

Matt Malek
I don't know insults slung at other physicists, but Earnest Rutherford once said "In science, there is only physics. All else is stamp collecting." I think scientists in other disciplines may consider this to be a physics insult...

Burch
If we think of drinking from a straw, it is not the suction pulling the water up, but atmosphereic pressure pushing it. Thus the limit on how high water can be pulled from a source. Now, we think about gravity as an attractive force, the earth pulls us down, but what if the earth was a "low pressure" zone and something was pushing us down. Has that been worked on, or is is simply a meaningless frame of reference thing...

Matt Malek
Well, remember that the atmospheric pressure is pushing water down because the atmosphere is being pulled to the Earth by gravity. In your case, I don't know what else could be pushing down on us if it weren't being driven by gravity.

Burch
Was Rutherford referring to theoretical or experimental physics? Just curious.

Matt Malek
I don't think he was trying to be divisive...

Burch
I never said it was a GOOD joke..

Vivek Jain
here's one for you "I do not know what is wrong with Heisenberg these days. He seems so sure of himself" I just typed typed physics jokes on google and out popped tons of them

Burch
I'm not saying it is not gravity, but rather the way in which gravity acts.

Matt Malek
I'm sorry, but I don't think I understand what you are asking here. Can you rephrase? (Or maybe I'm just a massless boson)

Burch
I'm uncertain what that means, let me consult with my cat-in-a-box, assuming that is is still alive

Matt Malek
Vivek's joke about Heisenberg being sure of himself was a pun on the Heisenberg uncertainty principle. Does that help?

Lucko
I hate to but in and I'm new here so I don't really know the rules. But since it is "ask a scientist" I have a question. I have been working on a science project on quicksand. Cornstarch and quicksand are compared as the same type of material in one reference I have. Can you explain to me how quicksand and cornstarch show the same thing?

Matt Malek
I'm sorry, Lucko, but I'm afraid that I know nothing about cornstarch beyond how to cook with it. And I don't know too much more about quicksand. Fundamental particles, cosmic rays, and astronomical objects are more my thing...

Lucko
Thanks anyway. This is a cool thing you are doing.

Matt Malek
Thanks! And it is a lot of fun, too!

Don S.
Thanks for your time! Good stuff and good night from Kansas.

Matt Malek
Good night to Don and to Kansas...

Cprossu
in the d0 and cdf how do you take the squiggly diagrams and figure out what particles/quarks have been created/annhilated....also just wondering what happened to the tev earlier in the day when i noticed the status said there wernt any protons or antiprotons in the ring?

Vivek Jain
hi cprossu: let's take an example of proton-anti-proton collisions. IN them, we can create a bottom and anti-bottom quark. In the detector, we don't see the quarks themselves, but we "see" other particles which contain them. For instance, the b quark could in a particle, we call the B- and the anti-b quark could be in a B+. We then detect the B- and B+ by the way they decay in the detectors. The accelerator is running today - you may have caught it at a time, before they started to store the protons.

MarchHare
How many physicists does it take to screw in a lightbulb? I don't know, I thought you guys might...

Vivek Jain
I don't know, but it took three of us this morning to get the video-conferencing system started ;-)

Burch
About gravity, another poor analogy might be water pulling a cork down a drain. If the water was not flowing, the cork would float. If the water is flowing it will push the cork down. So the question concerned how gravity acts. Is it truly pulling on us, or is some force carrier pushing down against us due the the mass of the earth. Like the hole in the sink bottom allows the water (force carrier) to flow.

Matt Malek
Okay, I think I understand you a bit better. The way that gravity works is still a bit of a mystery. If gravity works the same way as the other three forces, it would be carried by a force carrier boson particle (i.e. the graviton). However, general relativity tells us that gravity actually exists because physical masses bend spacetime. Reconciling the way gravity works in general relativity with the way it should work in quantum field theory (which describes the other forces) is a challenge.

Burch
I'm in Bartlett, I've probably been hit by some of your stray neutrinos :-)

Matt Malek
Ooops. Sorry.

MarchHare
You don't need lightbulbs with setting luminosity records! Good night from New York!

Matt Malek
Good night, New York!

Burch
thanks for putting up with me.. Catch you another time. This was fun.

Vivek Jain
fun for us too....

Cprossu
ive been watching it when i could-say it reach what 50 today?

Vivek Jain
that would be great.

Student
Good night!

Matt Malek
Goodnight all! It's been lots of fun!

Vivek Jain
good night everyone. this was the first time I tried it, and it was fun...

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