Time Dilation Effects in Physics

Time Dilation Effects in Physics Time dilation is the phenomenon where two objects moving relative to each other (or even just a different intensity of gravitational field from each other) experience different rates of time flow. Relative Velocity Time Dilation The time dilation seen due to relative velocity stems from special relativity. If two observers, Janet and Jim, are moving in opposite directions and as they pass by each other they note that the other persons watch is ticking slower than their own. If Judy were running alongside Janet at the same speed in the same direction, their watches would be ticking at the same rate, while Jim, going in the opposite direction, sees both of them having slower-ticking watches. Time seems to pass slower for the person being observed than for the observer. Gravitational Time Dilation Time dilation due to being at different distances from a gravitational mass is described in the general theory of relativity. The closer you are to a gravitational mass, the slower your clock seems to be ticking to an observer farther from the mass. When a spaceship nears a black hole of extreme mass, observers see time slowing to a crawl for them. These two forms of time dilation combine for a satellite orbiting a planet. On the one hand, their relative velocity to observers on the ground slows time for the satellite. But the farther distance from the planet means time goes faster on the satellite than on the surface of the planet. These effects may cancel each other, but also can mean a lower satellite has slower-running clocks relative to the surface while higher-orbiting satellites have clocks running faster relative to the surface. Time Dilation Examples The effects of time dilation are used often in science fiction stories, dating back to at least the 1930s. One of the earliest and most well-known thought experiments to feature time dilation is the famous Twin Paradox, which demonstrates the curious effects of time dilation at its most extreme. Time dilation becomes most apparent when one of the objects is moving at nearly the speed of light, but it manifests at even slower speeds. Here are just a few ways we know time dilation actually takes place: Clocks in airplanes click at different rates from clocks on the ground.Putting a clock on a mountain (thus elevating it, but keeping it stationary relative to the ground-based clock) results in slightly different rates.The Global Positioning System (GPS) has to adjust for time dilation. Ground-based devices have to communicate with satellites. To work, they have to be programmed to compensate for the time differences based on their speeds and gravitational influences.Certain unstable particles exist for a very brief period of time before decaying, but scientists can observe them as lasting longer  because they are moving so fast that time dilation means the time that the particles experience before decaying is different from the time experienced in the at-rest laboratory that is doing the observations.In 2014, a research team announced the most precise experimental confirmation of this effect yet devised, as described in a Scientific American article. They used a particle accelerat or to confirm that time moves slower for a moving clock than for a stationary one.

Thulium Facts

Thulium Facts Thulium is one of the rarest of the rare earth metals. This silver-gray metals share many common properties with other lanthanides but also displays some unique characteristics. Here is a look at some interesting thulium facts: Although the rare earth elements arent all that rare, they are so-named because they are difficult to extract from their ores and purify. Thulium actually is the least abundant of the rare earths.Thulium metal is soft enough that it can be cut with a knife. Like other rare earths, it is malleable and ductile.Thulium has a silvery appearance. It is fairly stable in air. It reacts slowly in water and more quickly in acids.Swedish chemist Per Teodor Cleve discovered thulium in 1879 from an analysis of the mineral erbia, a source of several rare earth elements.Thulium is named for the early name for Scandinavia- Thule.The principal source of thulium is the mineral monazite, which contains thulium at a concentration of  about 20 parts per million.Thulium is not toxic, although it has no known biological function.Natural thulium consists of one stable isotope, Tm-169. 32 radioactive isotopes of thulium have been produced, with atomic masses ranging from 146 to 177.The most common oxidati on state of thulium is Tm3. This trivalent ion most commonly forms green compounds. When excited, Tm3 emits a strong blue fluorescence. One interesting fact is that this fluorescence, along with red from europium Eu3  and green from terbium Tb3, is used as security markers in Euro banknotes. The fluorescence appears when the notes are held under black or ultraviolet light. Because of its rarity and expense, there are not many uses for thulium and its compounds. However, it is used to dope YAG (yttrium aluminum garnet) lasers, in ceramic magnetic materials, and as a radiation source (after bombardment in a reactor) for portable x-ray equipment. Thulium Chemical and Physical Properties Element Name: Thulium Atomic Number: 69 Symbol: Tm Atomic Weight: 168.93421 Discovery: Per Theodor Cleve 1879 (Sweden) Electron Configuration: [Xe] 4f13 6s2 Element Classification: Rare Earth (Lanthanide) Word Origin: Thule, the ancient name of Scandinavia. Density (g/cc): 9.321 Melting Point (K): 1818 Boiling Point (K): 2220 Appearance: soft, malleable, ductile, silvery metal Atomic Radius (pm): 177 Atomic Volume (cc/mol): 18.1 Covalent Radius (pm): 156 Ionic Radius: 87 (3e) Specific Heat (20 °C J/g mol): 0.160 Evaporation Heat (kJ/mol): 232 Pauling Negativity Number: 1.25 First Ionizing Energy (kJ/mol): 589 Oxidation States: 3, 2 Lattice Structure: Hexagonal Lattice Constant (Ã…): 3.540 Lattice C/A Ratio: 1.570 References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Langes Handbook of Chemistry (1952), CRC Handbook of Chemistry Physics (18th Ed.) Return to the Periodic Table