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Showing posts from January, 2013

F.A.Q's: Particle Physics

Why are the laws of physics not symmetrical between left and right, future and past, and between matter and antimatter?  I.e., what is the mechanism of CP violation, and what is the origin of parity violation in Weak interactions?  Are there right-handed Weak currents too weak to have been detected so far?  If so, what broke the symmetry?  Is CP violation explicable entirely within the Standard Model, or is some new force or mechanism required?Why is there more matter than antimatter, at least around here?  Is there really more matter than antimatter throughout the universe?  This seems related to the previous question, since most attempts at explaining the prevalence of matter over antimatter make use of CP violation.Are there really just three generations of leptons and quarks?  If so, why?  For example, the muon is a particle almost exactly like the electron except much heavier, and the tau particle is also almost the same, but heavier still.  Why do these three exist and no more? …

F.A.Q's:Cosmology and Astrophysics

What happened at or before the Big Bang?  Was there really an initial singularity?  Does the history of the Universe go back in time forever, or only a finite amount?  Of course, these questions might not make sense, but they might.Are there really three dimensions of space and one of time?  If so, why?  Or is spacetime higher-dimensional, or perhaps not really a manifold at all when examined on a short enough distance scale?  If so, why does it appear to have three dimensions of space and one of time?  Or are these unanswerable questions?Is the Universe infinite in spatial extent?  More generally: what is the topology of space?
We still don't know, but in 2003 some important work was done on this issue:Neil J. Cornish, David N. Spergel, Glenn D. Starkman and Eiichiro Komatsu, Constraining the Topology of the Universe. Briefly, the Wilkinson Microwave Anisotropy Probe (WMAP) was used to rule out nontrivial topology within a distance of 78,000 million light years—at least for a lar…

F.A.Q's:Quantum Mechanics

How should we think about quantum mechanics?  For example, what is meant by a "measurement" in quantum mechanics?  Does "wavefunction collapse" actually happen as a physical process?  If so, how, and under what conditions?  If not, what happens instead?
Many physicists think these issues are settled, at least for most practical purposes.  However, some still think the last word has not been heard.  Asking about this topic in a roomful of physicists is the best way to start an argument, unless they all say "Oh no, not that again!".  There are many books to read on this subject, but most of them disagree.Can we build a working quantum computer big enough to do things ordinary computers can't easily do?
This question is to some extent impacted by the previous one, but it also has a strong engineering aspect to it.  Some physicists think quantum computers are impossible in principle; more think they are possible in principle, but are still unsure if they …

F.A.Q's :Condensed Matter and Nonlinear Dynamics

What causes sonoluminescence?  Sonoluminescence is the generation of small light bursts in liquids caused by sound.  Bubbles form in the liquid at low pressure points of the sound wave, then collapse again as a high pressure wave passes.  At the point of collapse a small flash of light is produced.  The exact cause has been the subject of intense speculation and research. For more details, try this:
Sonoluminescence, Wikipedia.What causes high temperature superconductivity?  Is it possible to make a material that is a superconductor at room temperature?  Superconductivity at very low temperatures has been understood since 1957 in terms of the BCS theory, but high temperature superconductors discovered in 1986 are still unexplained. To learn more about superconductivity, see this web page and its many links:Superconductivity, Wikipedia.How can turbulence be understood and its effects calculated?  One of the oldest problems of them all.  A vast amount is known about turbulence, and we ca…

Gravitation: Frequently Asked Questions (F.A.Qs)

62. What is gravitation?
The attraction that every particle of matter in the universe has for every other particle.

63. When the moon comes' between the sun and the earthy how does that affect the attraction between the sun and the earth ?
Such interposition of matter has no effect on the attract-
ive force originally existing.

64. What is the first law of gravitation?
The attractive force (gravitation) between two bodies varies as the product of the masses of the two bodies.

65. Illustrate this law.

If two bodies contain 5 and 10 pounds of matter respectively, the product may be represented by 5a \\ two
other bodies contain 4 and 25 pounds of matter respectively, the product may be similarly represented by
100. Acting at like distances, the attraction between the second two will be twice (=Vrf') as great as the at-
traction between the first two.

66. How would doubling the matter in one of the bodies affect their gravitation?
It would double one of the factors, and thus the …

Work and Energy:Frequently Asked Questions (F.A.Qs)

38. What is work?

Work is the overcoming of resistance. The term implies
a change of position and is independent of the time
taken.

39. What may we take as a type of work?

The lifting of a bodv against the force of gravity, i, e,.
against the  pull  of the earth.

4a How may we measure such work ?

By considering both the weight of the body and the height
which it is raised.

41. How are work-units classified?

As gravitation units and absolute units, with two in each
class.

42. What are the gravitation units of work ?

The work expended in lifting one pound one foot against
the force of gravity is called a loot-pound. The work
expended in lifting one kilogram one meter against the
same force is called a kilogrammeter.

43. What are the absolute units of work ?

The work done by one poundal in producing a displace-
ment of one foot is called a foot-poundal. The work
done by one dyne in producing a displacement of one
centimeter is called an erg.

44. What is the numerical relation between th…

Force and Motion : Frequently Asked Questions (F.A.Qs)

1. What is motion?
Change of position.

2. What is velocity ?

Rate of motion ; it may be uniform or variable.

3. What is acceleration ?

Rate of change of velocity ; i. e,, the change of velocity
per unit of time.

4. What is force ?

Any cause that tends to produce any change of motion.

5. What is momentum?
Quantity of motion.

6. How is it measured?

By the product of the number of units of mass into the
number of units of velocity.

7. What is the unit of momentum called ?

It has no specific name. We may compare the momenta
of two moving bodies by the ratio between the two
measuring products as above explained. The momentum
of a body having a mass of 40 pounds and a velocity of
15 feet per second is twice as ereat as that of a body
having a mass of 10 pounds and a velocity of 30 feet per
second.

8. What is the first law of motion ?

Every body continues in its state of rest or of uniform
motion, in a straight line^ unless compelled to change
that state by some external force.

9. From what…

Properties of Matter : Frequently Asked Questions (F.A.Qs)

26. What is a property of matter ?
Some quality that pertains to matter.

27. What is a universal property of matter ?

A quality that pertains to all matter, a quality without
which matter, as we know it, could not exist.

28. What is a characteristic or accessory property of matter?

A quality that pertains to some kind or kinds of matter
and not to others, and that thus enables us to distinguish
one substance from another.

29. Name some of the universal properties of matter.
Extension, impenetrability, indestructibility, weight and
inertia.

30. Name some of the characteristic properties of matter.
Hardness, as of the diamond ; tenacity, as of steel ; brit-
tleness, as of glass; malleability, as of gold; ductility,
as of platinum.

31. What is extension ?

The property of matter by which matter takes up room,
i. e.y occupies space.

32. To what does it refer?

To length, breadth and thickness, a combination that is
essential to the existence of matter.

33. What is impenetrability ?

The pro…

How to construct the Camera Obscura ( Pin Hole Camera)

Make a circular hole in the shutter of a window, from whence there is a prospect of some distance; in this hole place a magnifying glass,
either double or single, whose focus is at the distance of five or six
feet; no light must enter the room but through this glass. At a
distance from it, equal to its focus, place a very white pasteboard,
(what is called a Bristol board, if you can procure one large enough,
will answer extremely well;) this board must be two feet and a half
long, and eighteen or twenty inches high, with a black border round
it: bend the length of it inward to the form of part of a circle,
whose diameter is equal to double the focal distance of the glass. 

Fix it on a frame of the same figure, and put it on a moveable foot, thatit may be easily placed at that distance from the glass, where theobjects appear to the greatest perfection. When it is thus placed, allthe objects in front of the window will be painted on the paper in aninverted position, with the greatest regularity,…

Make Artificial Lightning and Artificial Thunder

Provide a tin tube that is larger at one end than it is at the other,
and in which there are several holes. Fill this tube with powdered
resin; and when it is shook over the flame of a torch, the reflection
will produce the exact appearance of lightning.


Mix two drachms of the filings of iron, with one ounce of concentrated
spirit of vitriol, in a strong bottle that holds about a quarter of a
pint; stop it close, and in a few minutes shake the bottle; then
taking out the cork, put a lighted candle near its mouth, which should
be a little inclined, and you will soon observe an inflammation arise
from the bottle, attended with a loud explosion.

To guard against the danger of the bottle bursting, the best way would
be to bury it in the ground, and apply the light to the mouth by means
of a taper fastened to the end of a long stick.


Another way.

Mix three ounces of saltpetre, two ounces of salt of tartar, and two
ounces of sulphur; roll the mixture up into a ball, of which take a
quantit…

The Magical Picture

Take two level pieces of glass, (plate glass is the best,) about three
inches long and four wide, exactly of the same size; lay one on theother, and leave a space between them by pasting a piece of card, or two or three small pieces of thick paper, at each corner.

Join these glasses together at the edges by a composition of lime
slaked by exposure to the air, and white of an egg. Cover all theedges of these glasses with parchment or bladder, except at one end,which is to be left open to admit the following composition.
Dissolve, by a slow fire, six ounces of hogs'-lard, with half an ounce
of white wax; to which you may add an ounce of clear linseed oil.
This must be poured in a liquid state, and before a fire, between the
glasses, by the space left in the sides, and which you are then toclose up. Wipe the glasses clean, and hold them before the fire, to
see that the composition will not run out at any part.
Then fasten with gum a picture or print, painted on very thin paper,
with its face t…

How to make The Exploding Bubble

If you take up a small quantity of melted glass with a tube, (the bowl of a common tobacco-pipe will do,) and let a drop fall into a vesselof water, it will chill and condense with a fine spiral tail, which being broken, the whole substance will burst with a loud explosion, without injury either to the party that holds it, or him that breaks it; but if the _thick_ end be struck, even with a hammer, it will not break.

How to produce Fire by the Mixture of two cold Liquids

Take half a pound of pure dry nitrate, in powder; put it into a retort
that is quite dry; add an equal quantity of highly rectified oil of
vitriol, and, distilling the mixture in a moderate sand heat, it will
produce a liquor like a yellowish fume; this, when caught in a dry
receiver, is _Glauber's Spirits of Nitre_; probably the preparation,
under that name, may be obtained of the chemists, which will of course
save much time and trouble.

You then put a drachm of distilled oil of cloves, turpentine, or
carraways, in a glass vessel; and if you add an equal quantity, or
rather more, of the above spirit, though both are in themselves
perfectly cold, yet, on mixing them together, a great flame will arise
and destroy them both, leaving only a little resinous matter at the
bottom.

Matter : Frequently Asked Questions (F.A.Qs)

1. What is Natural Philosophy or Physics?
Natural Philosophy or Physics is the branch of science that treats of matter, and of the forces operating upon it, and of the physical changes thereby produced.
2. What is science?
Science is classified knowledge.
3. What is matter ?
Matter is anything that takes up room.
4. Is this a real definition of  Matter?
It is not, for it simply tells something about matter in- stead of telling what matter really is.
5. Why then is it given ?
Because, in the present state of human knowledge, we can tell nothing of the real nature of matter and this does the next best thing ; it enables us to distinguish matter from that which is not matter.
6. Give some other " definition " of matter. Matter is anything that has weight
7. What are the divisions of matter? Atoms, molecules, and masses.
8. What is an atom ?
The smallest quantity of matter that can enter into com- bination. It is generally a part of a molecule.
9. How many kinds of atoms are ther…