Portal:Physics/2007 Selected pictures

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This is an archive of entries that have appeared or will appear on Portal:Physics's Selected picture section in 2007.

[edit] Week 1

The incandescent metal embers of the spark used to light this Bunsen burner emit light ranging in color from white to orange to red. This change correlates with their temperature as they cool in the air. Note that the flame itself is luminescent (not incandescent) as its blue color is due to various other atomic and molecular energy transitions.

[edit] Week 2

Raising the air temperature inside the envelope of a hot air balloon makes it lighter than the surrounding (ambient) air. The rising hot air exerts pressure on the upper hemisphere of the balloon to provide lift, making the balloon capable of flight.

[edit] Week 3

The Prandtl-Glauert singularity, the point at which a sudden drop in air pressure occurs, is generally accepted as the cause of the visible condensation cloud that often surrounds an aircraft traveling at transonic speeds, though there remains some debate. It is an example of a mathematical singularity in aerodynamics.

[edit] Week 4

A plasma lamp is usually a clear glass orb that is filled with a mixture of various gases at low pressure and driven by high frequency alternating current at high voltage (approx. 35kHz, 2-5kV), generated by a high voltage transformer. A much smaller orb in its center serves as an electrode. Beams or snakes of "light" (actually emergent patterns in ionized gas) extend from the inner electrode to the outer glass container, giving an appearance similar to multiple constant beams of coloured lightning (see corona discharge and electric glow discharge). The beams first follow the electric field lines of the dipole, but move up due to convection.

[edit] Week 5

The Teller–Ulam design is a nuclear weapon design which is used in megaton-range thermonuclear weapons, and is more colloquially referred to as "the secret of the hydrogen bomb". This diagram depicts the basics of the Teller–Ulam configuration: a fission bomb uses radiation (from the bottom section) to compress and heat a separate section of fusion fuel (the top section).

[edit] Week 6

[edit] Week 7

Views of spacetime along the world line of a rapidly accelerating observer (see Lorentz transformation).

Vertical direction indicates time. Horizontal indicates distance, the dashed line is the spacetime trajectory ("world line") of the observer. The lower quarter of the diagram shows the events visible to the observer. Upper quarter shows the light cone- those that will be able to see the observer. The small dots are arbitrary events in spacetime.

The slope of the world line (deviation from being vertical) gives the relative velocity to the observer. Note how the view of spacetime changes when the observer accelerates.

[edit] Week 8

Halos, also known as icebows, are optical phenomena that appear near or around the Sun or Moon, and sometimes near other strong light sources such as street lights. There are many types of optical halos, but they are mostly caused by ice crystals in cold cirrus clouds located high (5–10 km, or 3–6 miles) in the upper troposphere. The particular shape and orientation of the crystals is responsible for the type of halo observed. Light is reflected and refracted by the ice crystals and may split up into colors because of dispersion, similarly to the rainbow.

[edit] Week 9

Wake turbulence is turbulence that forms behind an aircraft as it passes through the air. This turbulence includes various components, the most important of which are wingtip vortices and jetwash. Jetwash refers simply to the rapidly moving air expelled from a jet engine; it is extremely turbulent, but of short duration. Wingtip vortices, on the other hand, are much more stable and can remain in the air for up to two minutes after the passage of an aircraft. Wingtip vortices make up the primary and most dangerous component of wake turbulence.

[edit] Week 10

Arc welding uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. They can use either direct (DC) or alternating (AC) current, and consumable or non-consumable electrodes. The welding region is sometimes protected by some type of inert or semi-inert gas, known as a shielding gas, and/or an evaporating filler material. The process of arc welding is widely used because of its low capital and running costs.

[edit] Week 11

Aerogel is a low-density solid-state material derived from gels in which the liquid component of the gel has been replaced with gas. The result is an extremely low density solid with several remarkable properties, most notably its effectiveness as an insulator. It is nicknamed frozen smoke, solid smoke or blue smoke due to its semi-transparent nature and the way light scatters in the material; however, it feels like extruded polystyrene to the touch.

[edit] Week 12

The "energy flash" of a hypervelocity impact during a laboratory simulation of what happens when a piece of orbital debris hits a spacecraft in orbit.

[edit] Week 13

The "energy flash" of a hypervelocity impact during a laboratory simulation of what happens when a piece of orbital debris hits a spacecraft in orbit.

[edit] Week 14

Cutaway rendering of a cathode ray tube (see legend). The CRT was invented by Karl Ferdinand Braun, based on work by Philo Farnsworth, and was the display device that was traditionally used in most computer displays, video monitors, televisions, radar displays and oscilloscopes until the late 20th century before the advent of plasma screens, LCD TVs, DLP, OLED displays, and other technologies.

[edit] Week 15

A rope trick is the whimsical term given by physicist Dr. John Malik to the curious lines and spikes which emanate from the fireball of a nuclear explosion just after detonation. The image is from the Tumbler-Snapper test series of 1952.

The surface of the fireball is over 20,000 kelvins and emits huge amounts of visible light radiation. The 'rope tricks' which protrude from the bottom of the fireball are caused by the heating, rapid vaporization and then expansion of the mooring cables tethering the tower supporting the nuclear bomb at the start of the test.

[edit] Week 16

Portal:Physics/Selected picture/Week 16, 2007

[edit] Week 17

Portal:Physics/Selected picture/Week 17, 2007

[edit] Week 18

Portal:Physics/Selected picture/Week 18, 2007

[edit] Week 19

Portal:Physics/Selected picture/Week 19, 2007

[edit] Week 20

Portal:Physics/Selected picture/Week 20, 2007

[edit] Week 21

Portal:Physics/Selected picture/Week 21, 2007

[edit] Week 22

Portal:Physics/Selected picture/Week 22, 2007

[edit] Week 23

Portal:Physics/Selected picture/Week 23, 2007

[edit] Week 24

Portal:Physics/Selected picture/Week 24, 2007

[edit] Week 25

Portal:Physics/Selected picture/Week 25, 2007

[edit] Week 26

Portal:Physics/Selected picture/Week 26, 2007

[edit] Week 27

Portal:Physics/Selected picture/Week 27, 2007

[edit] Week 28

Portal:Physics/Selected picture/Week 28, 2007

[edit] Week 29

Portal:Physics/Selected picture/Week 29, 2007

[edit] Week 30

Portal:Physics/Selected picture/Week 30, 2007

[edit] Week 31

Portal:Physics/Selected picture/Week 31, 2007

[edit] Week 32

Portal:Physics/Selected picture/Week 32, 2007

[edit] Week 33

Portal:Physics/Selected picture/Week 33, 2007

[edit] Week 34

Portal:Physics/Selected picture/Week 34, 2007

[edit] Week 35

Portal:Physics/Selected picture/Week 35, 2007

[edit] Week 36

Portal:Physics/Selected picture/Week 36, 2007

[edit] Week 37

Portal:Physics/Selected picture/Week 37, 2007

[edit] Week 38

Portal:Physics/Selected picture/Week 38, 2007

[edit] Week 39

Portal:Physics/Selected picture/Week 39, 2007

[edit] Week 40

Portal:Physics/Selected picture/Week 40, 2007

[edit] Week 41

Portal:Physics/Selected picture/Week 41, 2007

[edit] Week 42

Portal:Physics/Selected picture/Week 42, 2007

[edit] Week 43

Portal:Physics/Selected picture/Week 43, 2007

[edit] Week 44

Portal:Physics/Selected picture/Week 44, 2007

[edit] Week 45

Portal:Physics/Selected picture/Week 45, 2007

[edit] Week 46

Portal:Physics/Selected picture/Week 46, 2007

[edit] Week 47

Portal:Physics/Selected picture/Week 47, 2007

[edit] Week 48

Portal:Physics/Selected picture/Week 48, 2007

[edit] Week 49

Portal:Physics/Selected picture/Week 49, 2007

[edit] Week 50

Portal:Physics/Selected picture/Week 50, 2007

[edit] Week 51

Portal:Physics/Selected picture/Week 51, 2007

[edit] Week 52

Portal:Physics/Selected picture/Week 52, 2007