CK-12 21st Century Physics: A Compilation of Contemporary and Emerging Technologies
Page 12
Describe “super symmetry,” abbreviated SUSY.
Overview
The standard model appears to be incomplete. While it does describe many phenomena and can predict many more, there are a few concepts it does not adequately describe.
Electron Size
According to the standard model, when examining the forces involved in the electron, it cannot be any smaller than due to repulsion in the electron cloud.
Figure 5.7
According to the standard model, the electron cannot be smaller than in diameter. This is due to the internal forces pushing outwards. However, an electron is approximately in diameter. If you include superparticles, using the concepts of super-symmetry, then this smaller size is allowed by this modified standard model.
Singular “Super Force”
As the universe ages it cools down. To examine the conditions of the universe when it was young, it must be heated up. One current belief is that in the beginning all the forces acted as one “super” force. Perhaps the electroweak and the strong forces combined to create a single super force. If the universe is heated up, physicists have shown that their strengths change. Electroweak get weaker and the strong force also gets weaker. However, according to the standard model, these forces don’t converge as the universe gets hotter.
Figure 5.8
Comparison of the Two Standard Models
In a super collider such as the LHC, much of the kinetic energy of the colliding particles is converted into thermal energy. This re-creates the high temperatures believed to have existed at the moment the universe was created. Essentially this is looking back in time to when the universe was young. During a collision the LHC will experience temperatures of million billion degrees Celsius, or . This is million times hotter than the Sun, (www.YouTube.com, LHC accelerator at CERN, 2008).
The Search
Evidence of super symmetry (SUSY) lies in finding tangible evidence of “superpartner” particles. Some evidence has already been found at experiments at Fermilab’s Tevatron, KEK’s KEKB collider in Japan, and PEP II storage ring at Stanford Linear Accelerator Center in the United States (U.C. Department of Science, "Particle Physics as Discovery’s Horizon,” 2006). A "superpartner” is related to the particles in the standard model.
Figure 5.9
Visual Representation of the Standard Model
In the standard model the particles can be divided into particles responsible for mass and particles responsible for force. The electron, , muon, , the tau, , the three neutrinos, , , , and the quarks are responsible for mass. The photon, , gluon, , boson, , and the boson, are responsible for force. In other words, the quarks and leptons pictured on the left in the standard model’s table are called fermions and are responsible for mass. The four particles in the last column on the right are called bosons and are responsible for all the forces. If the Higgs particle is confirmed in collider experiments, the standard model table could change to look something like the table below (Cox, TED, 2008).
Figure 5.10
This chart shows how the standard model could change if evidence of the Higgs particle is substantiated.
The super–symmetry model says that matter and force are not separate but somehow connected. Because of this connection, every fermion has a super–symmetric partner boson and for every boson there is a super–symmetric fermion. These super–symmetric particles are called the superpartners for the particles in the standard model. The superpartner particles are different from their counterparts by having half a quantum spin difference. They also have specific names and symbols.
Figure 5.11
The chart shows how the standard model could change if the superpartners are found.
The symmetrical particles for the fermions are the superpartner bosons. The suffix, “ino,” is added to the name. The symmetrical particles for the bosons are the superpartner fermions. The letter, “,” is added in front of their name.
Particle and the Corresponding Symmetrical Particle Fermion Symmetrical Boson
quark squark
electron selectron
neutrino sneutrino
muon smuon
tau stau
boson symmetrical fermion
photon photonino
gluon gluino
Zino
Higgs Higgsino
Many of the superpartners are very heavy. This means they are short–lived during and after a collision and can only be created by converting a lot of kinetic energy to mass. The LHC could provide enough energy to create these superpartners. One theory has the sneutrino as being responsible for dark matter.
Dark Matter and Dark Energy
Lesson Objectives
Describe what led to the theory of dark matter.
Describe what dark matter may be made from.
Describe what led to the concept of dark energy.
Overview
There is much that scientists don’t know. When astronomers peer into space, they take pictures and make observations about the change in locations of the stars and galaxies above. From this data they propose theories and make sense of motions. One of the most exciting events is when the galaxies and stars don’t behave as predicted. Scientists then begin to think how and why they are getting unusual results. Eventually a theory will arise that is supported more than others. It does not mean that it is correct, it may just be the most heavily tested at the time. Now is one of those times and dark matter and dark energy is one of those theories.
When astronomers look at the speed of each planet in our solar system, they see that the farther away the planets are from the Sun the smaller the planet’s velocity. This can be calculated according to Newton’s law of universal gravity and the concepts of circular motion. This concept extrapolates to the motion of galaxies as well as our solar system. But when astronomers look at the motion of other galaxies to examine the velocities of the stars in the systems, the results do not match the expectations. Instead, after a certain distance the speeds remain relatively constant.
Astronomers measure the mass of a galaxy by looking at the average luminosity of the galaxy and the star density. This luminosity is then proportioned to our Sun’s luminosity to mass ratio. If Newton’s law of universal gravity is used to verify the the motion of the galaxies, then it turns out that more mass must be in the galaxy than can be accounted for. About percent or more of the needed mass is unaccounted for (Imamura, 2008). This is too much to be accounted for by the unseen planets in the galaxy’s solar systems. Not enough additional objects can be seen using frequencies above or below the visible light spectrum to account for the % missing mass. Because this mass is not giving off any form of energy in the electromagnetic spectrum, it is given the name "dark matter.”
Dark matter is not detectable by looking in the electromagnetic spectrum. The collisions at the LHC may discover evidence of dark matter. It could find a connection between the lightest super partner and dark matter, or it may find evidence of multi-dimensions supporting string theory. A lot is to be determined (Green, 2008).
More Evidence of Dark Matter: Einstein’s Rings
Before Einstein it was thought that all light traveled in a straight line between the galaxies and the observers on Earth. Einstein proposed as part of his theory of general relativity that gravity not only curves the trajectory of objects and particles like baseballs and electrons, but it also bends light by bending the trajectory of photons.
Light from a distant galaxy travels in all directions. Some of the light travels straight to the observers on the Earth. Many light rays would pass the Earth.
Figure 5.12
If there is a massive galaxy between the Earth observer and the distant galaxy, the light could be bent toward the Earth as pictured above.
Figure 5.13
The Earth observer will see the galaxy as if the galaxy cluster in the middle were not there. The observer will see the galaxy at the end of the dotted line.
Figure 5.14
The distant galaxy will also emit other rays that will bend around the galaxy to reach the Earth.
Figure 5.15
This means that the Earth observer will see the distant galaxy in another position.
Because Earth exists in a three–dimensional space, the Earth observer will see more than these galaxies. He will see an infinite number of galaxies. All these galaxies will form a distorted ring in space. This distorted ring is called an Einstein ring.
Figure 5.16
Using the Hubble telescope, astronomers have discovered many visual examples of an Einstein ring. This is an image of Galaxy Cluster Abell 2218. In this image you can see white circular streaks. These streaks form the image of Einsteins rings.
For these rings to appear in images, there must be something in between the Earth and the observer. It is theorized that that something is dark matter—A substance that does not reflect or emit any energy in the electromagnetic spectrum but does exert the forces of gravity on photons.
Vocabulary
B-field
The abbreviation for magnetic field. The use of the letter “” is rumored to have come for the variable “” that was used in a published paper by Michael Faraday.
boson
A subatomic particle, such as proton, that has no quantum spin. They follow the description given by Bose and Einstein. These particles are responsible for forces in the universe.
bunch
A collection of electrons or nucleons. For the LHC a bunch equals charges.
CERN
European Organization for Nuclear Research: The Abbreviation originates from the original title, Conseil Europeén pour la Recherche Nucléaire.
collider
A machine in which two particles are guided into a head–on collision.
Coulomb
The Systems International’s standard unit of charge. Abbreviated with a capital “.” Named after Charles Coulomb.
dark matter
A substance with mass that does not emit, absorb, or reflect any type of electromagnetic energy.
E-field
The abbreviation for electric field.
electric field
A force field that moves objects with a charge that is positive or negative. Measured with the standard Systems International units of a Newton/Coulomb or the non-standard unit of a volt/meter.
electron volt
A small unit of energy directly proportional to the charge of an electron. : Abbreviated .
fermion
A subatomic particle, such as electrons, a quantum spin of a half. They follow the description given by Fermi and Dirac. These particles are responsible for mass.
giga
Prefix standing for billions. Example: A gigabyte hard drive stores four billion bytes of information.
hadron
A subatomic particle including baryons and mesons.
Higgs
A subatomic particle believed to be responsible for mass. Direct evidence of its existence has not been found as of February 2009.
Joules
The Systems International’s standard unit of energy. Abbreviated with a capital "." Named after James Joules.
kinetic energy
The energy associated with moving objects.
LHC
Large Hadron Collider.
lineac
Linear accelerator used to accelerate subatomic particles to high velocities.
magnetic field
A force field that affects moving charges. Natural sources are iron, nickel, cobalt, etc. The standard Systems International unit is the tesla.
mega
Prefix standing for millions. Example: Six megavolts is six million volts.
tera
Prefix standing for trillions.
Review Questions
How much money would a “meganaire” have?
At one time Bill Gates was worth billion dollars. Express this in words using the science prefixes for sizes.
A particle of negligible mass moves between two plates of a linear accelerator as shown in Figure 17. By how much does the energy (in ) of the particle’s energy change?
Figure 5.17
A particle of negligible mass moves between two plates of a linear accelerator as shown in Figure 18. How much energy (in ) does the particle’s energy change by?
Figure 5.18
A particle of negligible mass moves between two plates of a linear accelerator as shown in Figure 19. How much energy (in ) does the particle’s energy change by?
Figure 5.19
What is the centripetal acceleration needed to turn a particle with a mass of exactly protons traveling at around a ring the size of the LHC (?
References / Further Reading
Stanford Linear Accelerator Center, 2009, http://www2.slac.stanford.edu/vvc/accelerator.html(SLAC length)
Schwartz, Cindy (1997). A Tour of the Subatomic Zoo. New York, NY: Springer-Verlag, 83-84.
CERN, 2009, http://public.web.cern.ch/public(location)
CERN Courier, Jan., 25, 2001, http://cerncourier.com/cws/article/cern/28361 (CERN History)
CERN, 2008, http://public.web.cern.ch/public/en/LHC/LHC-en.html(CERN Experiments)
CERN–ALICE Collaboration, 2008, http://aliceinfo.cern.ch/Public/Welcome.html
CERN–ATLAS Experiment, 2008, http://atlas.ch/
CERN, 2008, http://public.web.cern.ch/public/en/LHC/TOTEM-en.html
CMS–Outreach, 2008, http://cms-project-cmsinfo.web.cern.ch/cms-project-cmsinfo/index.html
CERN–LHCb Experiment, 2008, http://lhcb-public.web.cern.ch/lhcb-public/
CERN, 2008, http://public.web.cern.ch/public/en/LHC/LHCf-en.html
What is CERN Large Hadron Collider LHC? End of the World? Search for God Particle and Micro Black Holes..
CERN–Outreach, 2008, http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach (Number data) .
CERN–Outreach, 2008, “LHC Beams,” http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/beam.htm
CERN 1999, “History,” http://lhc.web.cern.ch/lhc/general/history.htm
LHC accelerator at CERN.
Office of Science, U.S. Department of Energy, US/LHC Large Hadron Collider 2008, Particle Physics as Discovery’s Horizon, http://www.uslhc.us/LHC_Science/Questions_for_the_Universe/Undiscovered_Principles
Imamura, Jim, 2008. Lecture notes, http://zebu.uoregon.edu/~imamura/123/lecture-2/mass.html
Hooper, Dan, October 2007, www.YouTube, “Supersymmetry and the Search for Dark Matter.”
Cox, Brian, TED – Technology Engineering and Design, “Brian Cox: An Inside Tour of the World's Biggest Supercollider,” http://www.ted.com/index.php/talks/brian_cox_on_cern_s_supercollider.html
Greene, Brian, 2008, TED – Technology Engineering and Design, “Brian Greene: The Universe on a String.” http://www.ted.com/index.php/talks/brian_greene_on_string_theory.html
Virginia Physics Standards of Learning
This chapter fulfills sections PH.3, PH.4, PH.5, PH.6, and PH.14 of the Virginia Physics Curriculum.
Chapter 6: A Brief Synopsis of Modern Physics
Angela Cutshaw. "Modern Physics", 21st Century Physics FlexBook.
Outline
1. What is modern physics?What is quantum mechanics and why did it develop? What part of physics was not complete? What is relativity and why did it develop? What part of physics was not complete?
Question 1 How do you see?
Question 2. Why can’t we see atoms? Objects are made of atoms and light is reflecting off of them, right? Why don’t we see the little balls that make up the object?
Question 3. So how do we know atoms exist?
Question 4. How do we know the basic structure of an atom?
Question 5. How do we know there are electrons? Is it the same experiment as for the nucleus?
Question 6. Why are there neutrons in the nucleus with the protons?
Question 7. What are quarks and how do they play a role inside the
atom?
Question 8. What are alpha particles and where do we get them?
Question 9. What really is radioactivity? Why do some elements emit or “put off” streams of alpha particles? Do any elements emit particles other than alpha particles?
Question 10. What is Quantum Mechanics and why did it develop? What part of physics was not complete?
Question 11. What is the photoelectric effect? What does it mean to say that matter has wave-like properties?
Question 12. What is Relativity and why did it develop? What part of physics was not complete?
2. What parts of modern physics are still being researched?
Question 13 : What can be considered the big problem facing physicists today?
3. What are the implications of some of Modern Physics (including nanoscience, dark matter, black holes, parallel universes, and the graviton)?
Question 14 : What are some of the implications of quantum mechanics and relativity? In the news there is mention of string theory, black holes, parallel universes, and other bizarre things.
This chapter has been written as a series of questions in the effort to lead you through an understanding of how modern physics came about, some of its components, some of the still lingering problems in its theories, and some of its implications. This is by no means an exhaustive discussion and you are urged to read further and go deeper by asking experts.