Tutor in Math, Physics, Statistics, and Computer Science. Ph.D. Email:admin@TutorState.com, Skype:znamenski

## Saturday, April 30, 2011

## Thursday, April 28, 2011

### Подготовка по математике к экзаменам и тестам.

Здравствуйте!

Хотите заниматься математикой со мной?

У меня больший опыт подготовки к разным экзаменам студентов разного уровня.

Обычно я беру за занятия: $30 за часовое занятие или $50 за двухчасовое занятие.

Если к студенту надо ехать на дом и это не близко, то я прошу добавить.

Занятия можем провоить как на русском языке, так и на английском (нужно знать математические термины на английском и уметь понимать постановку задач.)

Самый удобный Вариант для меня, когда студенты приходят ко мне: 52 92nd St, Brooklyn, NY 11209.

Также можем договориться о проведении занятий где-нибудь в библиотеке, кафе или у Вас дома.

С уважением,

Василий.

Phone: 718-223-0228

http://www.TutorState.com/

## Wednesday, April 27, 2011

### Core Vocabulary List, Physics

absorption

acceleration

action/reaction pair

amplitude

angle of incidence

angle of refraction

applied force

atomic structure

attractive force

centripetal

acceleration

centripetal force

charged particle

circuit element

closed system

coefficient of friction

conductivity range

conductor

constant velocity

cosmic level

critical angle

curved mirror

digital analysis

direction of

propagation

discrete packet

discrete values

dispersive medium

Doppler effect

elastic potential

energy

electric charges

electric circuit

electric field

electrical energy

electrical power

electro-weak force

electromagnetic

energy

electromagnetic

radiation

electromagnetic wave

elementary charge

equilibrium

field strength

free fall

frequency

friction

friction

gravitational field

gravitational force

gravitational potential

energy

ideal mechanical

system

impulse

inertia

internal energy

internal reflection

inverse square law

kinetic energy

Law of conservation

of energy

linear motion

longitudinal

magnetic field

maximum frictional

force

mechanical energy

mechanical wave

medium

momentum

natural frequency

net force

nuclear energy

Ohm’s Law

oscillating charge

oscillating system

parallel circuit

period

periodic wave

perpendicular

components

phase

photon

plane mirror

polarization

polychromatic light

potential difference

potential energy

power

Principle of

Superposition

projectile path

pulse

quantization

quantum nature of

fundamental forces

quark

real image

reflection

refraction

relative index of

refraction

relative motion

repulsive force

resistance

resonance

scalar quantity

schematic diagram

series circuit

spring constant

standing wave

strong force

subnuclear

subnuclear level

charge

tangental velocity

temperature

thermal energy

time-rate

total energy of a

system

transmission

transmitted wave

transverse

transverse wave

unbalanced force

### 101 "pfacts" for the Physics regents exam.

# Physics Regents Exam Tutor

**Phone: 718-223-0228**

**Email: admin@TutorState.com**

**Website: www.tutorstate.com**

## 101 "pfacts" for the Physics regents exam.

The original 101 pfacts can be found at: http://homepages.go.com/~abcdeder/101facts.html(revised by Drew Panko, June 2002)

1. Mass and inertia are the same thing. (Mass actually measures inertia - in kilograms… Much as monetary resources measures financial wealth - in dollars.)

2. Weight (force of gravity) decreases as you move away from the earth by distance squared. (It decreases, but only approaches zero, never reaching it, even far beyond the solar system.)

3. Weight (in newtons) is mass x acceleration (w = mg). Mass is not Weight! Mass is a scalar and measured in kilograms, weight is a force and a vector and measured in Newtons.

4. Velocity can only be constant when the net force (and acceleration) is zero. (The velocity can be zero and not constant - for example when a ball, thrown vertically, is at the top of its trajectory.)

5. Velocity, displacement [s], momentum, force (weight), torque, and acceleration are vectors.

6. Speed, distance [d], time, length, mass, temperature, charge, power and energy (joules) are scalar quantities.

7. The slope of the distance-time graph is velocity.

8. The slope of the velocity-time graph is acceleration.

9. The area under a velocity-time graph is distance.

10. Magnitude is a term used to state how large a vector quantity is.

11. At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the minimum value (at 180) to the maximum value (at zero) is the total range of all the possible resultants of any two vectors.

12. An

*unbalanced*force

*must*produce an acceleration and the object

*cannot*be in equilibrium.

13. If an object is not accelerating, it is in equilibrium and no unbalanced forces are acting.

14. The equilibrant force is equal in magnitude but opposite in direction to the resultant vector.

15. Momentum is conserved in all collision systems. Energy is conserved (in the KE of the objects) only if a collision is perfectly elastic.

16. Mechanical energy is the sum of the potential and kinetic energy.

17. UNITS: a = [m/sec

^{2}]; F = [kg•m/sec

^{2}] = Newton; work = PE = KE = [kg•m

^{2}/sec

^{2}] = Joule; Power = [kg•m

^{2}/sec

^{3}] = [Joules/sec] = Watt

18. 1ev is a very small energy unit equal to 1.6 x 10

^{-19}joules - used for small objects such as electrons. This is on the Reference Chart.

19. Gravitational potential energy increases as height increases.

20. Kinetic energy changes only if mass or velocity changes.

21. Mechanical energy (PE + KE) does not change for a free falling mass or a swinging pendulum. (when ignoring air friction)

22. A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].

23. Short, fat, cold wires make the best conductors.

24. Electrons and protons have equal amounts of charge (1.6 x 10

^{-19}coulombs each - known as one elementary charge). This is on the Reference Chart.

25. Adding a resistor in series increases the total resistance of a circuit.

26. Adding a resistor in parallel

*decreases*the total resistance of a circuit.

27. All resistors in series have equal current (I).

28. All resistors in parallel have equal voltage (V).

29. If two similar charged spheres touch each other add the charges and divide by two to find the final charge on each sphere after they are separated.

30. Insulators contain no electrons free to move.

31. Ionized gases conduct electric current using positive ions, negative ions and electrons.

32. Electric fields all point in the direction of the force on a positive test charge.

33. Electric fields between two parallel plates are uniform in strength except at the edges.

34. Millikan determined the charge on a single electron using his famous oil-drop experiment.

35. All charge changes result from the movement of electrons not protons. (an object becomes positive by losing electrons)

36. The direction of a magnetic field is defined by the direction a compass needle points. (The direction an isolated north pole would feel.)

37. Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.

38. Magnetic flux is measured in webers.

39. Left hands are for negative charges and

*reverse*answer for positive charges.

40. The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant.

41. Solenoids are stronger with more current or more wire turns or adding a soft iron core.

42. Sound waves are longitudinal and mechanical.

43. Light slows down, bends toward the normal and has a shorter wavelength when it enters a medium with a higher index of refraction (n).

44. All angles in wave theory problems are measured to the normal.

45. Blue light has more energy, a shorter wavelength and a higher frequency than red light (remember- ROYGBIV).

46. The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest. They are all electromagnetic and travel at the speed of light (c = f ! l ).

47. The speed (c) of all types of electromagnetic waves is 3.0 x 10

^{8}m/sec in a vacuum.

48. As the frequency of an electromagnetic wave increases its energy increases (E = h ! f) and its wavelength decreases and its velocity remains constant as long as it doesn't enter a medium with a different refractive index (i.e. optical density).

49. A prism produces a rainbow from white light by dispersion. (red bends the least because it slows the least).

50. Transverse wave particles vibrate back and forth perpendicular to the direction of the wave's velocity. Longitudinal wave particles vibrate back and forth parallel to the direction of the wave's velocity.

51. Light wave are transverse (they, and all (

*and only*)transverse waves can be polarized).

52. The amplitude of a non-electromagnetic wave (i.e. water, string and sound waves) determines its energy. The frequency determines the pitch of a sound wave. Their wavelength is a function of its frequency and speed (v = f ! l ). Their speed depends on the medium they are traveling in.

53. Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase.

54. At the critical angle a wave will be refracted to 90 degrees. At angles larger than the critical angle, light is reflected

*not*refracted.

55. Doppler effect: when a wave source moves toward you, you will perceive waves with a shorter wavelength and higher frequency than the waves emitted by the source. When a wave source moves away from you, you will perceive waves with a longer wavelength and lower frequency.

56. Double slit diffraction works because of diffraction and interference.

57. Single slit diffraction produces a much wider central maximum than double slit.

58. Diffuse reflection occurs from dull surfaces while regular (spectacular) reflection occurs from smooth (mirror-like) surfaces.

59. Only waves show diffraction, interference and the polarization.

60. The period of a wave is the inverse of its frequency (T = 1/f ). So waves with higher frequencies have shorter periods.

61. Monochromatic light has one frequency.

62. Coherent light waves are all in phase.

63. In order to explain the photoelectric effect, Einstein proposed particle behavior for light (and all electromagnetic waves) with E = h f and KE

_{max}= hf – W

_{o}.

64. A photon is a particle of light (wave packet).

65. To preserve the symmetry of the universe, DeBroglie proposed wave behavior for particles ( l = h/mv). Therefore large fast moving objects (baseballs, rockets) have very short wavelengths (that are unobservable) but very small objects, particularly when moving slowly have wavelengths that can be detected in the behavior of the objects.

66. Whenever charged particles are accelerated, electromagnetic waves are produced.

67. The lowest energy state of a atom is called the ground state.

68. Increasing light frequency increases the kinetic energy of the emitted photo-electrons in the photo-electric effect (KE

_{max}= hf – W

_{o}).

69. As the threshold frequency increases for a photo-cell (photo emissive material) the work function also increases (W

_{o}= h f

_{o})

70. Increasing light intensity increases the number of emitted photo-electrons in the photo-electric effect but not their KE (i.e. more intensity>more photons>more electrons emitted). This is the particle nature shown by light.

71. Key to understanding trajectories is to separate the motion into two independent components in different dimensions - normally horizontal and vertical. Usually the velocity in the horizontal dimension is constant (not accelerated) and the motion in the vertical dimension is changing (usually with acceleration of g).

72. Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle. (Centripetal

*means*towards the center!)

73. An object in orbit is not weightless - it is its weight that keeps it moving in a circle around the astronomical mass it is orbiting. In other words, its weight is the centripetal force keeping it moving in a circle.

74. An object in orbit is in free fall - it is falling freely in response to its own weight. Any object inside a freely falling object will appear to be weightless.

75. Rutherford discovered the positive nucleus using his famous gold-foil experiment.

76. Fusion is the process in which hydrogen is combined to make helium.

77. Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons, which, in turn, can go on and cause more fissions.

78. Radioactive half-lives are not effected by any changes in temperature or pressure (or anything else for that matter).

79. One AMU of mass is equal to 931 meV of energy. (E = mc

^{2}). This is on the Reference Charts!

80. Nuclear forces are very strong and very short-ranged.

81. There are two basic types of elementary particles: Hadrons & Leptons (see Chart).

82. There are two types of Hadrons: Baryons and Mesons (see Chart).

83. The two types of Hadrons are different because they are made up of different numbers of quarks. Baryons are made up of 3 quarks, and Mesons of a quark and antiquark.

84. Notice that to make long-lived Hadron particles quarks must combine in such a way as to give the charge of particle formed a multiple of the elementary charge.

85. For every particle in the "Standard Model" there is an antiparticle. The major difference of an antipartcle is that its charge is opposite in sign. All antiparticles will anhililate as soon as they come in contact with matter and will release a great amount of energy.

85. Notice that to make long-lived Hadron particles quarks must combine in such a way as to give the charge of particle formed a multiple of the elementary charge.

86. Notice that the retention of the Energy Level Diagrams on the new charts implies that there will be questions on it. The units (eV) can be converted to Joules with the coversion given on the first Chart of the Regents Reference tables. And can be used with the formula (given under

**Modern Physics**formulas) to calculate the energy absorbed or released when the electron changes levels.

And by using another formula (given under

**Modern Physics**formulas) you can calculate the frequency of electromagnetic radiation absorbed or released. AND using the Electro-magnetic spectrom given on the charts you can find out what kind of electromagnetic radiation it is (infrared, visible light, UV light, etc.)

Notice that because of the new syllabus, we've "lost" some facts students had to know before 2002.

This is a work in progress, these facts must be tested against four or five of the "new syllabus" regents exams to get fine-tuned.

101. Physics is phun!! (This is key. Honest!)

Special thanks to Physics teacher Jim Davidson for creating the original list.

(revised 6/2002 by D. Panko)

VI. Motion in a plane

V. Modern Physics

IV. Wave Phenomena

III. Electricity and Magnetism

II. Energy

I. Mechanics

### Regents Physics Exam Prep

**Regents Physics Exam Prep: 101 Facts You Should Know**

Compiled by Jim Davidson, High School Physics Teacher

Compiled by Jim Davidson, High School Physics Teacher

- Weight (force of gravity) decreases as you move away from the earth by distance squared.
- Mass and inertia are the same thing.
- Constant velocity and zero velocity means the net force is zero and acceleration is zero.
- Weight (in newtons) is mass x acceleration (w = mg).
**Mass is not weight!** - Velocity, displacement [s], momentum, force and acceleration are vectors.
- Speed, distance [d], time, and energy (joules) are scalar quantities.
- The slope of the velocity-time graph is acceleration.
- At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the difference to the sum is the total range of possible resultants.
- Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle.
- An unbalanced force (object not in equilibrium) must produce acceleration.
- The slope of the distance-tine graph is velocity.
- The equilibrant force is equal in magnitude but opposite in direction to the resultant vector.
- Momentum is conserved in all collision systems.
- Magnitude is a term use to state how large a vector quantity is.
**Energy** - Mechanical energy is the sum of the potential and kinetic energy.
- Units: a = [m/sec
^{2}], F = [kg•m/sec^{2}] (newton), work = pe= ke = [kg•m^{2}/sec^{2}] (joule) - An ev is an energy unit equal to 1.6 x 10
^{-19}joules - Gravitational potential energy increases as height increases.
- Kinetic energy changes only if velocity changes.
- Mechanical energy (pe + ke) does not change for a free falling mass or a swinging pendulum.
*(when ignoring air friction)* - The units for power are [joules/sec] or the rate of change of energy.
**Electricity** - A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].
- Short fat cold wires make the best conductors.
- Electrons and protons have equal amounts of charge (1.6 x 10
^{-19}coulombs each). - Adding a resistor in parallel decreases the total resistance of a circuit.
- Adding a resistor in series increases the total resistance of a circuit.
- All resistors in series have equal current (I).
- All resistors in parallel have equal voltage (V).
- If two charged spheres touch each other add the charges and divide by two to find the final charge on each sphere.
- Insulators contain no free electrons.
- Ionized gases conduct electric current using positive ions, negative ions and electrons.
- Electric fields all point in the direction of the force on a positive test charge.
- Electric fields between two parallel plates are uniform in strength except at the edges.
- Millikan determined the charge on a single electron using his famous oil-drop experiment.
- All charge changes result from the movement of electrons not protons (an object becomes positive by losing electrons)
**Magnetism** - The direction of a magnetic field is defined by the direction a compass needle points.
- Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
- Magnetic flux is measured in webers.
- Left hands are for negative charges and right hands are for positive charges.
- The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant.
- Solenoids are stronger with more current or more wire turns or adding a soft iron core.
**Wave Phenomena** - Sound waves are longitudinal and mechanical.
- Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
- All angles in wave theory problems are measured to the normal.
- Blue light has more energy. A shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
- The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest.
- A prism produces a rainbow from white light by dispersion (red bends the least because it slows the least).
- Light wave are transverse (they can be polarized).
- The speed of all types of electromagnetic waves is 3.0 x 10
^{8}m/sec in a vacuum. - The amplitude of a sound wave determines its energy.
- Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase.
- At the critical angle a wave will be refracted to 90 degrees.
- According to the Doppler effect a wave source moving toward you will generate waves with a shorter wavelength and higher frequency.
- Double slit diffraction works because of diffraction and interference.
- Single slit diffraction produces a much wider central maximum than double slit.
- Diffuse reflection occurs from dull surfaces while regular reflection occurs from mirror type surfaces.
- As the frequency of a wave increases its energy increases and its wavelength decreases.
- Transverse wave particles vibrate back and forth perpendicular to the wave direction.
- Wave behavior is proven by diffraction, interference and the polarization of light.
- Shorter waves with higher frequencies have shorter periods.
- Radiowaves are electromagnetic and travel at the speed of light (c).
- Monochromatic light has one frequency.
- Coherent light waves are all in phase.
**Geometric Optics** - Real images are always inverted.
- Virtual images are always upright.
- Diverging lens (concave) produce only small virtual images.
- Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium
*{frequency remains constant}*. - The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red.
**Modern Physics** - The particle behavior of light is proven by the photoelectric effect.
- A photon is a particle of light
*{wave packet}*. - Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave.
*(DeBroglie Waves)* - All electromagnetic waves originate from accelerating charged particles.
- The frequency of a light wave determines its energy (E = hf).
- The lowest energy state of a atom is called the ground state.
- Increasing light frequency increases the kinetic energy of the emitted photo-electrons.
- As the threshold frequency increase for a photo-cell (photo emissive material) the work function also increases.
- Increasing light intensity increases the number of emitted photo-electrons but not their KE.
**Internal Energy** - Internal energy is the sum of temperature (ke) and phase (pe) conditions.
- Steam and liquid water molecules at 100 degrees have equal kinetic energies.
- Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
- Temperature measures the average kinetic energy of the molecules.
- Phase changes are due to potential energy changes.
- Internal energy always flows from an object at higher temperature to one of lower temperature.
**Nuclear Physics** - Alpha particles are the same as helium nuclei and have the symbol .
- The atomic number is equal to the number of protons (2 for alpha)
- Deuterium () is an isotope of hydrogen ()
- The number of nucleons is equal to protons + neutrons (4 for alpha)
- Only charged particles can be accelerated in a particle accelerator such as a cyclotron or Van Der Graaf generator.
- Natural radiation is alpha (), beta () and gamma (high energy x-rays)
- A loss of a beta particle results in an increase in atomic number.
- All nuclei weigh less than their parts. This mass defect is converted into binding energy. (E=mc
^{2}) - Isotopes have different neutron numbers and atomic masses but the same number of protons (atomic numbers).
- Geiger counters, photographic plates, cloud and bubble chambers are all used to detect or observe radiation.
- Rutherford discovered the positive nucleus using his famous gold-foil experiment.
- Fusion requires that hydrogen be combined to make helium.
- Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons.
- Radioactive half-lives can not be changed by heat or pressure.
- One AMU of mass is equal to 931 meV of energy (E = mc
^{2}). - Nuclear forces are strong and short ranged.
**General** - The most important formulas in the physics regents are:
- Physics is fun. (Honest!)

**Mechanics**

## Saturday, April 16, 2011

## Friday, April 15, 2011

### ax+by=cx+dy=zx+zy

Find z as function of a, b, c, and d;

Solution:

a(x/y)+b=c(x/y)+d=z(x/y)+z;

let (x/y)=t;

at+b=ct+d;

(a-c)t=d-b;

t=(d-b)/(a-c);

ct+d=zt+z;

z=(ct+d)/(t+1);

z={c(d-b)/(a-c)+d}/{(d-b)/(a-c)+1};

z={c(d-b)+d(a-c)}/{(d-b)+(a-c)};

z=(cd-cb+da-dc)/(d-b+a-c);

z=(cb+da)/(d-b+a-c);

z=(ad+bc)/(a-b-c+d);

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## Thursday, April 14, 2011

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## Wednesday, April 13, 2011

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## Tuesday, April 12, 2011

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## Monday, April 11, 2011

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## Sunday, April 10, 2011

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## Tuesday, April 5, 2011

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## Monday, April 4, 2011

### Superconductivity from nowhere

Superconductivity from nowhere - physicsworld.com

# Superconductivity from nowhere

Mar 29, 2011 14 comments

In just over a week scientists will celebrate the centenary of superconductivity: the discovery, in 1911, that some materials cooled towards absolute zero allow electric charge to flow without resistance. But now one physicist believes superconductivity can appear when there is no material at all.

According to Maxim Chernodub of the Université François-Rabelais Tours in France, superconductivity can appear – provided there is a very strong magnetic field – in the vacuum of empty space. If Chernodub is correct, the phenomenon could explain the origin of the extensive magnetic-field patterns seen in the cosmos. "This suggested vacuum superconductivity is very unusual," he says. "It has a few crazy properties that do not exist in 'normal' superconductors."

In normal superconductors, charge flows without resistance because all the charge carriers – that is, the electrons – "condense" into the same state. Physicists explain this behaviour with so-called BCS theory, which describes how electrons move through the superconductor's crystal lattice. When one electron moves, it distorts the lattice, attracting positive charge. The next electron is then attracted to this positive charge, and so becomes paired with the first electron. Together, all the paired electrons form a condensate that moves as a single entity.

Scientists have done a good job of explaining the physics of normal superconductors, like lead, which must be cooled close to absolute zero in low magnetic fields. But there are also superconductors that exist at relatively high temperatures of 30 K or more, and for these physicists are still working on a proper explanation.

### The strangest yet?

In a paper soon to appear in *Physical Review Letters*, however, Chernodub contemplates a type of superconductivity that might be the strangest yet. Unlike previously known superconductivity, it would survive at very high temperatures, perhaps billions of degrees. It would also exist alongside strong magnetic fields and, perhaps strangest of all, it wouldn't need a material to exist – just a vacuum.

How can superconductivity arise from nowhere, when apparently there aren't even any charge carriers? In fact, even the purest vacuum contains charge carriers. According to quantum mechanics, the vacuum is a soup of "virtual" particles that momentarily pop into existence, such as quarks and antiquarks. An up quark and a down antiquark can bind to form a positively charged rho meson, but the meson is normally so unstable that it decays.

Chernodub thinks that in a strong magnetic field the quarks would be forced to move only along the field lines – and this would make the rho mesons far more stable. In addition, the rho meson's own spin would interact with the external magnetic field, lowering the particle's effective mass to zero so that it can move freely, as in a superconductor. Chernodub's calculations, which are based on a well-known model in quantum chromodynamics (QCD), suggest the external magnetic field required for this superconductivity must be at least 10^{16 } T.

### A very strong field

That's a very strong field. The best magnets on Earth – which, perhaps ironically, use superconducting coils – can achieve fields approaching only 30 T, while the most magnetized objects in space, which are a type of neutron star known as a magnetar, probably reach fields of a mere 10^{10} T.

Yet Chernodub believes proof of his prediction could be found close to home at the Large Hardon Collider (LHC) based at Geneva, or the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in New York. Last November the first lead ions collided at the LHC. Because such ions are moving, they create magnetic fields, and Chernodub thinks that a "near miss" between two of them might – for perhaps just one yoctosecond (10^{–24} s) – generate a field at almost the required 10^{16} T. If vacuum superconductivity does arise at the LHC or the RHIC, he expects it would leave a trace of charged rho mesons.

"How realistic this is, I cannot really tell at the moment," says Igor Shovkovy, an expert in QCD at Arizona State University in the US. "One of the complications in high-energy collisions is a very short duration of the magnetic fields generated by the passing ions or protons. The other is the difficulty of extracting unambiguous signals that would single out this phenomenon from among others."

### 'Interesting idea'

Volodya Miransky, a particle physicist at the University of Western Ontario in Canada, calls Chernodub's prediction an "interesting idea" but adds that "the question whether one can observe this effect is open, I think, and this possibility deserves to be studied".

Vacuum superconductivity might not always need particle accelerators, however. Chernodub thinks the early universe might have had sufficiently strong magnetic fields, and that the subsequent super-currents might have seeded the mysterious large-scale magnetic fields seen across the universe today. "It sounds like a crazy idea, but what if it is true?" he says.

### About the author

Jon Cartwright is a freelance journalist based in Bristol, UK