Questions and Answers from Virtual Ask-a-Scientist of March 19, 2002
More information about the program
Curriculum Vitae, Roger L. Dixon
Curriculum Vitae, Robin D. Erbacher
Hi! Welcome to virtual
Ask-a-Scientist! Roger and Robin are ready to answer all your physics questions.
Roger, can you tell
me a little about astrophysics?
attempts to use the knowledge we have of the way matter behaves at the very
smallest scales-- quarks and leptons-- and uses it to understand the universe at
the very large scales. Got any specific questions about how all this works?
On this webpage you
can see Live Events from the detectors of CDF and DZero
How big is the
tevatron? How much bigger will the new accelerator in Europe be?
The Tevatron is
approximately 4 miles in circumference. The LHC at CERN is 27km. One mile is 1.6
I see that Fermilab is
allowing easier visitor access. When will this be back to normal?
Hi Carl, There is
a press release right off of the FNAL website which explains the status. The
good news is that we now allow pedestrians and cyclists into Fermilab without
having to register. People in automobiles still have to request visitor's passes
and arrive in the Pine street entrance, unless they want to go to the Lederman
Science Center only. We hope that we will return to normal access soon, but we
do not have a date.
I noticed on Robin's CV
that she is interested in - was it Top Quark? Is Fermilab working on quarks?
Hi Barb, This is
Robin. Yes, Fermilab scientists are working on studying many different quarks.
The top quark is the heaviest of them all, and was discovered at Fermilab in
1995. We still have many things we'd like to learn about this quark, so we are
busily sifting through the data as they come in!
Recent Fermilab Press
Release: Fermilab offers guided tours.
Are there any quarks left
to be "discovered", or are they all accounted for now?
Well, all of the
quarks that we have so far expected have been discovered, which we consider a
great success for our models that predicted them. There may be something called
squarks, which are the supersymmetric partners of quarks, but so far this has
not been proven and is only a very elegant theory.
On this webpage you
can see Live Events from the detectors of CDF and DZero
What will happen to the
Tevatron after the LHC goes into operation with the new upgrades ?
The Tevatron will
probably continue to run after the LHC comes on. It will still have useful
physics to do. However, there will come a time when we will want to replace it
with a machine that will be more interesting and more competitive.
Will that be the VLHC?
The VLHC is a
wonderful project, but very ambitious for the current technology. The US high
energy physics community is now supporting a future Linear Collider, which would
be an electron-positron colliding machine in the 500GeV-1.5TeV range. This is so
far in the design and proposal stage, so we'll see what happens.
How are things
progressing with NumiMinos?
The MINOS detector
being constructed in the deep iron mine in northern Minnesota is progressing
very well. It will be done well in advance of the beam, which is also
progressing well at Fermilab, but a little slower. The detector should be
finished by the end of 2003, I think.
Fermilab publishes a
bi-weekly magazine called FermiNews. On this webpage you can read the latest
There was an article in
the current American Scientist entitled "Is String Theory Even Wrong?" Any
comments on this from Fermilab?
Hi KLHess, That
sounds like a very interesting article. Unfortunately, neither Roger nor I have
read it, though now I plan to go look it up. Fermilab itself doesn't usually
make official comments on articles. Do you have any specific questions that
maybe we could answer about that?
The author, Peter Woit,
suggested that theorists are paying too much attention to a theory that "cannot
be falsified by any conceivable experimental result." He suggests it's time to
explore some alternatives.
Hmmm. Some of my
colleagues feel that way, too. :) Really, though, in my opinion (and everyone
has different opinions on the subject) string theory is a very elegant
mathematical model, and has been successful at achieving many things that we
would like to see achieved in this science, such as Grand Unification. However,
being an experimentalist, it is frustrating not to be able to search for
To follow up with
KLHess question on the article, the theory of supersymmetry came from string
theory, and we can (and in fact do) search for SUSY particles at our
well i would like to
know, what properties would an object have to exibit in order to be clasified as
a black hole?
You would not be
able to see it directly as no light can escape from it. You would see x-rays
coming from the material that is falling into it as the matter is accelerated
and torn apart. You would see evidence that there was a lot of mass in the area
where you see nothing. In summary, it would be very strange behavior, and we do
see lots of objects out in the universe that fit this description.
On this webpage we
post an accelerator update on a daily basis:
Did you know that
there is an exceptional variety of birds living, breeding on Fermilab grounds?
Here is a link to our "bird pages":
I can understand the
repulsion between two electrons as the result of bombardment of each by virtual
photons. But how does attraction between a positron and an electron work using
the same virtual photon principles? Keep in mind that I'm not overly fond of
falling back on "skyhooks" or mysterious fields as an explanation. Are the
virtual photons between oppositiely charged particles 180 degrees out of phase
so that when they interact they cancel out leaving the net force behind the
particles and so they are "pushed" toward each other?
Good question. This
one is difficult, The main difficulty is that you are trying to build up the
attractive force between two particles by looking at just one tiny part of it.
You have to remember that there are many interactions going on between the two
charged particles and the net force is the result of all those interactions. It
is not a single scatter. It is many scatters, and the net result is an
Also, remember that
the virtual photons themselves can split into charged particles pairs and all of
these get involved in the net interaction.
What are the chances that
the linear collider (if built) will be at Fermilabs ?
Hi sri, Fermilab
has endorsed pursuing the LC as the next major project here. It is a very
ambitious goal. The German community is looking at a similar proposal called
TESLA right now, and Japan is trying to write a proposal as well. Unfortunately,
it is often a question of political support and willingness to be a leader in
science around the world to make it happen. We only have some small amount of
control over political decisions. But you all have a voice via your
At Fermilab we have an
education center called "Lederman Science Center". This is their homepage:
QuarkNet is a research
collaboration between high school students, teachers and particle physicists.
This is the QuarkNet website: http://quarknet.fnal.gov/
are there any projects
going on (or planed), where users can volenteer their spare CPU clock cycles to
help find new balck holes, and other objects in the universe (ala seti)
I am not aware of
any such projects (other than SETI) which uses people's CPU's at home. Black
holes are observed by x-ray satellites and ground based instruments, but those
efforts always have enough computing power built into them. Much like Fermilab
does not go to individual's cpu's to analyze our data.
Fermilab gets a lot of
physics questions from curious people. Physicists answer these question and they
get posted on the Fermilab website:
On the Fermilab
website you can find a High Energy Physics timeline, explaining who discovered
what and when. This is the url:
Is my view of the
repulsive force between like charge particles to simplistic?
Well, not exactly.
You view is basically right, but it is the subtleties of all virtual
interactions that can go on to make the net force that is difficult to predict
from basic interactions.
The moderator is
informing us of a number of what I would call "outreach" programs. Do you have
an individual that coordinates such outreach activities? I have just completed
year 1 of a pilot program I founded called Science Buddies.
www.klhess.com/mentoring The program enables high school students to mentor
middle school students (junior high in the Midwest) doing a science fair
project. The students are backed up by professional scientists. If you have an
outreach czar, I would be interested in contact information.
I suggest that you get in touch with the Education Office here at
Fermilab. Phone number is (630 840 3092.
Fermilab is on 6000
acres of prairie and farm land. Here is a link to information about the
restoration of the prairie:
Physics is our
mission, but buffalo may be Fermilab's main attraction for visitors. What are
buffalo doing at a physics laboratory? Here is the
What is a Linear Collider?
Is it linear as in a "straight line" or is it also circular, like the Tevatron?
A Linear Collider
is indeed in (more or less) a straight line. In some of the designs, the
electrons are accelerated on one side in a straight line, and the positrons
(antimatter electron) are accelerated on the other side, but the two
accelerators are not exactly in a straight line. This saves real estate. But you
can correct the beam positions with magnets in the final focusing. Electrons do
better being accelerated in a straight line because if they go in a circle, they
radiate away some of their energy in synchrotron radiation.
Can Fermilabs produce and
store antimater consitently and reliably. Do you forsee any commercial uses of
antimatter in the near future ?
and stores antimatter reliably for the collider. The quantity we produce is very
small compared to what you would need to make a star ship, but people are
beginning to think of commercial uses for it. I am only vaguely aware of these.
Try searching for antimatter in the internet and see what you come up with.
And to make the
Fermilab animal story complete, I would like to inform you about the butterfly
activity. A total of 51 species of butterflies were seen on the Fermilab campus
during the past three years.
Well can I generally
assume then that whatever are the complexities of the total interactions, that
the "attractive" force bewteen unlike charged particles is really due to a net
propellant force toward the opposite particle which looks like an attraction but
is really a propulsion toward each particle?
I don't know what
you mean by "propellant force" but the particles are attracted to one another,
and in principle, you can build that attraction up from the basic interaction
between the two particles. You have to integrate over all possibilities to get
the right answer.
Back to physics. At
this moment we have an exhibit called "Pulse - Accelerator science in medicine".
We put it online: http://www.fnal.gov/pub/pulse/
Where are the electrons
of a lightning bolt an instant before the bolt. Does their extremely high
potential come from their being near each other??
I would state the
reason for the potential in a little bit different way than you have. There is
an excess of electrons in a different place than there is an excess of positive
charge. This is what causes any electrical discharge or current to flow. Right
before the lightening strikes the electrons are distributed in the clouds, air
and ground a little more unevenly than they are when there when there is no
threat of a lightening strike. This uneven distribution causes some strong
electric fields that eventually causes the electrons to avalanch, or begin
flowing in one direction. This becomes your lightning strike.
How does the Fermi
National Accelerator compare to the CERN counterpart?
Well, CERN and
Fermilab are similar laboratories in what their missions are, and in the
scientists that work there.
Let me restate that, how
does Fermilab's accelerator compare to CERN's techinaly?
Follow up to
Milosz: For example, I could go and work at CERN because they are particle
physicists just like me. And people who have worked at CERN come here as well.
In fact, many scientists who have worked at LEP, the recently finished
experiment there, are now working on the Tevatron here since the LHC is still
several years away.
If you are referring to the actual experiments and machines, well that depends
on which experiments you are comparing to. Earlier in this session I mentioned
that the new project being developed at CERN (the LHC) is going into the LEP
ring, which is 27 km. (1mile = 1.6km) The Tevatron is about 4 miles. But really
the important thing is what kind of science are we doing. The LEP experiment at
CERN used electrons and positrons, and made many precision measurements on the W
and Z bosons. They also searched for new physics, like SUSY particles and Higgs.
The Tevatron uses protons and antiprotons. The different methods can do
different types of physics, so they are complementary.
But I thought the photon
(virtual or not) was the force carrier in EM reactions. How can an electron's
photon reach out and "grab" a positron or proton? There has to be a physical
action even at the sub-atomic level, no?
Yes, the photon is
the force carrier, and virtual photons are responsible for the force between any
two charged particles. All I have been trying to say is that one single
interaction between a photon from one of the charged particles and the other
particle does not necessarily lead to a deflection that brings the particles
together. But, when you add up millions of these interactions with all the
possibilities that can take place with the virtual photon, the net effect
between two like-charged partciles is an attraction.
On this webpage we
post an accelerator update on a daily basis:
i have another one....If
space is expanding why don't we observe the distance to say the moon,
The simple answer is
that everthing we use to measure is expanding. So, how do we know that the
universe is expanding? Because we see things moving away from us. And the light
that comes from distant places in the universe is stretched out. We can tell
this from absorption and emmission spectra, etc. Also, the effect between the
moon and earth is miniscule on the scale of the Universe.
Every year a Tornado
and Severe Weather seminar is organized at Fermilab. This year this very popular
seminar is on Saturday, April 13. Here is information about the program.
Do you have any
videos on your website?
Yes, we have VideoNews
and streaming video of lectures and colloquia. Here is the url:
Virtual Tour: The next
best thing to visiting Fermilab in person.
OK, I think I'll follow
up on this with a Saturday visit to AAS at the Lederman Center. A pad and pencil
will add to the visualization. One further question, what actually defines
charge, i.e. what is it about an electron that makes it negative and what is it
about a positron that makes it positive? We toss these terms around as if
they're givens, but I suspect there is more to it that would help with the
explanation of attraction and repulsion.
Good idea on going
to Lederman. Anyway, charged particles all emit and aborb virtual photons. It is
always difficult to describe a properties of the particle by beginning with the
fundamental emission and aborption of the photons. But the properties of this
cloud of photons around the particle does determine what the other particle
interacting with it sees and does. In the end you have positive and negatively
charged particles. The charge is not defined by the cloud. It is defined by the
way the particles behave, which, in principle could be determined form the
virtual cloud if you were a lot smarter than me. Your question is really a good
one for a theorist. They might tell you how to begin the calculation, and maybe
even finish it.
Thanks very much. You
HAVE been helpful. I'll try these questions in more detail on your colleagues on
Saturday. See you again.
Does the presence of a
body( say an atom) affect the growth of the space it occupies or the space
gravity (general relativity) equations do combine space with all of the matter
around it, and does demonstrate these effects. However, we don't really know how
to apply GR to things on the scale of the atomic size. Gravity is so weak
compared to the other forces: 10^-41 times weaker than the electromagnetic
forces. Particle physicists deal with very small particles, so gravity never
comes into play. However, on the scale of planets and such, the GR equations
Fermilab publishes a
bi-weekly magazine called FermiNews. You can sign up, it's free! Here is a link
to the online version of the magazine
http://www.fnal.gov/pub/ferminews/ferminews02-03-15/index.html Here is a link to
the online subscription form
Do you guys do any weapons
Hi Carl, No, we
do not work on any weapons here at Fermilab. We are specifically doing
scientific research for a knowledge base in particle and astrophysics. Of
course, along with that comes huge strides in technology, some of which can then
be applied to advance society (examples: world wide web, superconducting
magnets, accelerators in medicine, and on and on). Other Dept of Energy labs do
work on weapons, but we are more like a giant university here.
A short while ago we
put together an online photo collection that introduces Fermilab in all its
facets. Here is the link:
What is the Tevatron
doing right now? Check the Tevatron status:
What's the difference
between CDF and DZero?
Hmm. Well, during
the Tevatron Run 1 (~1986-1996) there was a much bigger difference. They were
designed differently: CDF built in a large magnet and a tracking chamber,
whereas Dzero built a finely segmented calorimeter. Both experiments produced a
lot of very nice results, and together they discovered the top quark. Today for
Run 2 the detectors are much more similar, although both have different
strengths and weaknesses. We can look forward to very interesting results out of
both of them. I would say that they are complementary, but we also need each
other to combine our statistics so that we get more precise answers.
i have a school debate
about the big bang, i am split half way (it happened / it didn't happen) after
seeing all the "evidence" for both sides, epecial hearing all the arguments that
shot holes in what i belived about the big bang to this moment, if you could
tell me one argument for the big band, that would explain why it did occur and
how do we know that
There are two very
strong pieces of evidence for the big bang. The first is the fact that all the
other galaxies in the Universe are moving away from us. The second is that we
see all the radiation that is leftover from the bang, and it has exactly the
properties we would predict for it. So, there was a time when the universe was
much, much, much smaller. Now if you ask a more difficult question such as was
there really a singularity, you might get a good discussion going and find that
there is some disagreement about what happened on the earliest and smallest
I was just wondering in
all the experiments involving CP Violation and the occurence measured for mesons
was the velocity of the mesons ever measured, if not do you happen to know the
velocities of Kaons and B-mesons
Hi David, The
velocities (momenta) of the various particles that are created in these
experiments vary. We measure them with our tracking detectors in the
experiments. We need to know the momenta so we can perform the necessary
measurements. Of course, in the end we try to stop the particles in our
calorimeters completely, so they give off their energy and we have a good
measure of their energy. B mesons decay very repidly, though, so we usually see
the daughter particles that come from them. We can then reconstruct the
Fermilab has a big
audience that visits the lab for cultural events. On this page you can see what
we offer: http://www.fnal.gov/pub/events/culture.html
Is the modern science
close to explaining gravitational force on quantum scale ( gravitons..). Is it
such a big deal!??
There are now very popular models for quantum gravity. I forget the title, but
there is a very nice treatment of such ideas in a book by Andre Linde from
Stanford University. Stephen Hawking always has nice treatments of such things
as well. As far as gravitons go, this is the boson (force carrier) for the
gravitational force. However, on the scale of subatomic particles, it is
impossible to see gravitons or measure their properties (though we have quantum
numbers for them) since gravity is 10^-41 times weaker than the electromagnetic
force. There are several experiments that are trying and have tried to measure
gravity waves. One is LIGO (CalTech is involved) and another is the Gravity
Probe B out of Stanford, that is due to be launched (or has been launched... I
have to check).
Okay, I have a
question about red shift that I have never really understood. We see objects
moving away from us as red shifted. That means the photons have lost energy.
What happens to the energy? Is energy not conserved in general relativity?
The answer to your
question lies in the Einstein equation. Yes the photons have lower energy, but
essentially, they have given it up to the expansion of the universe. Energy is
Did you know that
Fermilab had the second (or third) website in the U.S.A.? Read more about this:
I saw an article on the
web today about a huge asteroid that zipped past earth recently, but went
undetected for a few days because it came from the direction of the sun. How
often does this happen, and what can we learn from these types of events?
Since I don't really
work in that field, and we don't do that sort of astronomy at Fermilab, I can
only answer you in general. Asteroids do zip by the come close to the earth
quite frequently, and there are many asteriods that have not been found. We find
new ones all the time. And, it is not only the ones that are coming toward us
from the sun that have not been observed. It is just that it is very difficult
to find and measure the orbits of all of them. An object that is 10 kilometers
across is difficult to see, but it would do considerable damage to the earth if
it scored a direct hit. You know, they might have to cancel the NFL preseason,
Fermilab maintains a
good relationship with the neighboring communities. We often get questions from
our neighbors. We answer and post them on our Community Forum website:
A question some people
ask us is "Why support science?". We devoted a webpage to the answer:
the events of the big
bang that happened at later times make sence to me, but the "something from
nothing" theory as shown in our books, dosn't make a lot of sence to me, infact
it makes as much sence, as the oposite view, that it was created by god in 7
days (adam and eve, etc)
The fact of the
matter is, you can get back to a time when we don't understand what came before,
or why it came. We keep pushing back as far as we can and so far, we keep
getting more answers. This means that there will only be questions that can be
answered by believing something. And we all do that-- even scientists.
To get our protons on
the way we use a "chain of accelerators". Here is more information:
This is the website of
Cryogenic Dark Matter Search, Roger's experiment:
And this is the
website of CDF, where Robin does her research: http://www-cdf.fnal.gov/
Thanks to all of you
guys...you have a wonderful site, too...best compliments!!!!
Mieke, Kevin, and
Judy et al of the Public Affairs Office deserve credit for the website. Mieke is
the moderator here and Kevin is the ChatMaster. They are great. I have a lot of
fun browsing through our site (when I'm not just going to the work-related
pages). Thanks for joining us and asking such good questions!
bi-weekly magazine, features stories about Fermilab's experiments and the people
that work on them. You can sign up, it's free! This is a link to the current
issue: http://www.fnal.gov/pub/ferminews/ferminews02-03-15/index.html This is a
link to an online subscription form:
What's the best thing about
being a scientist?
Not having to worry
about what you wear to work everymorning. Well, that's not really it. The best
part is getting to work on answering some of the big questions about the world
we live in and getting paid to do it. It is great to be a part of discovering
something important for the first time.
The Fermilab Education
Office offers seven programs for under-graduate students:
So...What's the worst
part of being a scientist?
Hi Barney, Since
I didn't comment on the *best* part of it, I'd say that I agree with Roger. It
is really a great feeling to try to understand something for the first time, or
to measure something that will progress the knowledge of humankind. However,
being a scientist is very challenging in many ways. It takes many years to get
to the level of professor or tenured researcher, and you gamble that you will
eventually even get to such a position. You are often well into your 30s before
you know. It also doesn't pay very much. But we do it for the love of our work.
One of the more frustrating things, though, is the fact that our funding (and in
fact funding for all of the physical sciences, surprisingly) has been cut
constantly now, for more than a decade. We would love it if everyone out there
placed as high a value on the work of science as we do, but it doesn't always
happen. It's hard when you depend on the government for funding, and they keep
changing their minds about whether or not they want to support you.
afternoon, from 1 to 3 p.m., two Fermilab scientists answer questions at the
Lederman Science Center at Fermilab. This program inspired us to go online and
answer questions from people that can't come to the lab. Here is more
Is there any particular
reason that Soudan, Minnesota was chosen for the location for the CDMS detector?
Is there something special about that location other than the existence of the
It was known back in
about 1995 that the CDMS collaboration would need a deep site to extend the
search for dark matter. They were setting up to run under the Stanford campus at
that time. Meanwhile, Fermilab was planning to do the MINOS experiment in
Soudan, so it was natural for the CDMS people to get together with Fermilab and
plan to do the next phase of their experiment there. This way it was possible to
take advantage of an existing laboratory and facilities. Which brings me back to
Barney's question-- the worst part of being a scientist? That would be the
coffee in Sadie's Bakery in Tower Minnesota-- that and having to go down in a
hole and work all day when you are basically a mountain person.
How much does your
reseach cost anyway? The answer can be found on our Budget webpage:
I read that lots of
foreigners work at Fermilab. How do they all communicate? How do they get along?
Hi Spy, nice
icon! :) Yes, we do have a LOT of collaborating scientists from institutions
around the world (and sometimes who are employed by U.S. institutions). It's
wonderful! I have learned so much about other countries and cultures, and
sometimes we meet in other countries to exchange information with physicists
around the globe. We communicate in English: the official language now that is
used at most conferences. At labs such as CERN in Europe, the official languages
are both French and English, but conferences are typically in English. It used
to be that German and Russian and other languages were very important as well,
but now the default seems to be English. They are making it too easy for us
English-speakers to get away without learning another language! But many of us
who go to work at a lab in Germany or Japan or Switzerland will learn the local
language out of interest and out of necessity to live in that society. It really
keeps life interesting.
i missed most of the chat and
it might be answered already but from what i know dark matter is not an
antimatter, so how these three (matter, dark matter and antimatter) coexist and
why if matter is "balanced" by antimatter there is a dark matter too
I have been waiting for these dark matter questions. Anyway, you are right. Dark
matter is not antimatter, but guess what? Dark matter is made up of dark matter
and anti dark matter too-- well maybe. Since we are not certain what it is yet--
we haven't detected and studied it in the laboratory-- we can't be certain of
this, but one of the favorite theories would predict this. In fact, one of the
ways to detect it might be to see energetic neutrinos from the annihilations.
By the way, matter
is not really balanced by antimatter in the universe. As near as we can tell,
the universe is made up of matter and not antimatter. This has to do with almost
all the matter in the universe annihilating and there being just a little bit of
matter left over due to something called CP violation-- maybe. What was left
over is what we see today.
director, Robert Wilson, loved to sculpture and design. He greatly influenced
the design of the entire laboratory site. Here is more info:
brochures online: http://www.fnal.gov/pub/about/public_affairs/brochures.html
i've heard it said that the
"fabric of the universe" is bent/curved the closer one is to something with
mass, like planets. what is the "fabric of the universe"?
The fabric of the
Universe is spacetime, and yes, it is bent by matter. Surprisingly, space is not
nothing. It is something that can be bent. Virtual particles pop in and out of
it. It is actually fairly complicated, and we are just learning about all of its
Hey Robin. Thanks for the
answer. Sounds as if you really get to go places. Cool.
Yes, travel is
one of the "perks" of being in such a global field, but we also use a lot of
email. Communicating with collaborators who are far away was one of the reasons
the world wide web was developed at CERN and then at SLAC. But certainly nothing
compares with going there and sharing information and designing things face to
... I need to run now. I'll
be back, Spy
Virtual Tour: The next
best thing to visiting Fermilab in person.
Why the need for the
extreme cold temperature in the CDMS detector? Is this done in other detectors
First of all there
are other people trying to make similar "cryogenic" detectors. The reason the
detectors have to be so cold is that we are trying to identify nuclear recoils
that occur when dark matter, or WIMP, particles bounce off the nucleus. It turns
out that one good way to do that is to measure both the ionization and the
sound, or phonons, produced in the crystal when the nucleus recoils. To detect
these very low level phonons the crystal must be very quiet, which means that
you must bring all the motion as close to a stop as you can in the crystal.
Hence the extremely cold temperatures-- 25 thousandths of a degree, or about 460
degrees below zero fahrenheit.
thanks Roger. so, when
light exhibits wave-like behavior, is it the spacetime that is waving?
Spacetime is bent,
or changes shape in a gravitational field. And, yes there can be oscillation, or
gravitational waves in spacetime.
A glossary and online
resources for those who would like to know more.
Physics questions from
real people and physics answers from Fermilab scientists.
i hear that sometimes light
acts like particles, sometimes like waves. when acting like waves, what is
The electric and
magnetic fields are oscillating in a light wave. This wave behavior is governed
by Maxwell's Equations.
Fermilab produced its
first high-energy particle beam on March 1, 1972. Since then hundreds of
experiments have used Fermilab's accelerators to study matter at ever smaller
scales. Here an overview of the top ten achievements so far.
Live Tevatron Status
shows the current status of Fermilab's Tevatron, the world's highest energy
particle accelerator, and is updated every 10 seconds.
Why is the Tevatron named
The Tevatron is
so called because we are running at energies close to a TeV, or a
tera-electron-volt. Electron volts is a basic unit of energy that we use: the
amount of energy it takes to accelerate one electron over one volt. A tera would
be 1000 times a Giga (you may be familiar due to the new PC capabilities), or a
1000 billion electron volts. The Tevatron is the highest energy accelerator in
the world right now, so we are on the energy frontier. We hope that we can
either see evidence for something new here, or even discovery something
"Is it safe to live
near Fermilab" This is a webpage with answers to this and more safety questions:
i'm sorry, i'm not very
mathematical. are the electric and magnetic fields associated with a particle?
do they exist by themselves apart from a particle? do/can they exist
independently from each other?
The electric and
magnetic fields are coupled to the charges on the particles. Again, Maxwells
Equations govern how all of this works. What I am saying is that the charges on
the particles generate the fields and the motions of the particles cause changes
in the fields.
Could there be a
communication medium (other than RF) that could work over far distances with low
interference using minimal power?
Good question: In fact the Navy spent some money at Fermilab some years back
investigating the possibility of communicating with submarines using
neutrinos. This only satisfies the low interference over long distances part
of your question. It takes significant power to create a neutrino beam, not
to mention the problem of aiming it at a particular submarine that is moving
around. Anyway, most of us at the Laboratory knew the answer to the Navy's
question before they even got started looking into it, but they insisted. It
is certainly possible to send a message using neutrinos. The problem is that
it would take several days to transmit a simple message such as S.O.S. That
is because you need so many interactions before you can be certain to get the
contents of the message. That is what you pay for the "low interference"
quality of your beam.
It is also possible to communicate with most all frequencies of the
electromagnetic spectrum, but there is not a great advantage to taking this
route although we have recently been using light in fiber optic cables.
People also communicate with their television sets with infrared signals.
You could also communicate with any kind of particle beam, but creating them
is expensive and clumsy. It is not easy to change aim a high energy beam to
any point you want to send a signal, so you are better off with low energy
beams which don't go very far. In the end, I don't know how you would win at
It's 3 p.m., Fermilab
time, and time to wrap up this chat session. Thanks to all of your questions. We
all had a lot of fun! In about a week the complete transcript will be online,
check the news box on the homepage or go to this url:
http://www.fnal.gov/pub/inquiring/virtual/aas_transcript3-19-02.html Next month
there is another chat, with different scientists, hope to see you again. Bye!
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