It also allows lasers and electron beams to pass through unimpeded and will even glow blue, if you make the plasma out of argon. The only drawback is that it requires huge amounts of energy to produce plasma windows of any size, so current examples are very small. In theory, though, there is no reason they could not be made much bigger.
There is nothing in the laws of physics to say invisibility is impossible, and recent advances mean certain types of cloaking device are already feasible. The last few years have seen a rash of reports concerning experimental invisibility cloaks , ever since a basic design for one was produced in These devices rely on metamaterials to guide light around objects.
The first of these only worked on microscopic objects and with microwaves. It was thought that modifying the design for visible light would prove very challenging, but in fact it was done just one year later — albeit only in two dimensions and on a micrometre scale. The engineering challenges involved with building a practical invisibility cloak remain formidable. This is a word with a long and rather dubious history.
It was coined by the paranormalist writer Charles Fort in his book Lo! Despite its fantastical origins, physicists have achieved a kind of teleportation thanks to a bizarre quantum phenomenon called entanglement. Particles that are entangled behave as if they are linked together no matter how wide the distance between them.
Performing the trick with anything larger than an atom was once thought impossible, but in a theoretical way to entangle even large molecules , providing they can be split into a quantum state known as superposition, was described. By Michael Marshall What is truly impossible?
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Remember, particles in solids only vibrate; particles in liquids move quicker and the particles are not as close; and then particles in gases move faster and are spread more apart. The third law that relates to weather is the Gay-Lussac's law. This law states: " the pressure of a fixed mass of gas at a constant volume varies directly with the Kelvin temperature. This means if the temperature increases, the pressure increases, as well.
Therefore, as air molecules are heated, they move faster, thus making more collisions and pressure is increased. The language used by meteorologists is high and low atmospheric or air pressure. Air pressure is the phenomenon of a column of air pushing down on a particular area. Air pressure not only pushes downward but it is the weight of air pushing in all directions. The atmosphere closest to Earth has more pressure than the atmosphere at higher altitudes because if you think if a column of air pushing down on an object, there is all the weight of the air nearest to the surface of the Earth.
The farther you go up in elevation, the less air is there to add to the weight. Air has properties which are mass and density, as well as pressure. The density of the atmosphere must be discussed, at this point. Since air has density, the denser the air is, the more pressure there is. In other words, denser air has more mass per unit volume than less dense air. Density is affected by three factors: the amount of water vapor, elevation and temperature.
Warmer air is less dense than colder air and warmer air holds more water vapor than colder air. Therefore, hot air with more water vapor is less dense and has lower air pressure. But, you may think that if air has more water vapor in it, that the air would be denser. This is where Dalton's law helps to explain this. Dalton's law deals with the pressure of a gas mixture which is the sum of each individual gas pressure.
We know that our atmosphere is a mixture of gases as stated above. Water vapor is less dense than nitrogen or oxygen of the other gases mentioned. Water vapor has a lighter molecular mass than diatomic nitrogen and diatomic oxygen, which are found in our troposphere. Water vapor has two hydrogen molecules and an oxygen molecule giving it an atomic mass of Diatomic nitrogen has an atomic mass of 28 and diatomic oxygen has an atomic mass of So, although air with water vapor feels heavier and is harder to breathe, it is still less dense than cold, drier air.
Water vapor is a greenhouse gas that traps heat on Earth, as well. It is like a sweater surrounding the Earth, trapping the heat radiation from the ground. Energy is stored in water vapor as heat. Water vapor is considered to be a positive feedback to greenhouse warming meaning as more water is evaporated into the air due to higher temperatures, the warmer the air will become, thus making a positive feedback loop.
However, along with more evaporation of water into the air leads to more cloud formation which can lead to the clouds reflecting the Sun's radiation away from the Earth.
The cloud cover lowers the temperature, thus producing a negative feedback loop and increased water vapor could have a self-correcting effect. There is much debate, currently, about this issue of water vapor and its impact on global warming, which is the gradual increase of the Earth's atmospheric temperature. Cloud formation is due to a phase change called condensation. Just the opposite of evaporation, condensation occurs when heat is released from a gas.
Clouds are formed when water vapor condenses around tiny solid particles in the air. Clouds are classified by their appearance and height. The three basic forms of clouds are stratus, cirrus, and cumulus. Cirrus clouds are high in the sky and are white, thin, and wispy. The cumulus clouds are puffy with a flat base and look dome-like resembling cauliflower. The stratus clouds look like sheets that cover the sky. The height of clouds classifies them further.
High clouds are usually white and made up of ice crystals. Since there is more water vapor available at lower altitudes, low and middle altitude clouds tend to be darker and denser.
The reason why not all clouds precipitate, although they all contain water, is that the size of droplets are so small that for high clouds, when the droplets fall, even in humid air, they evaporate before they reach the ground. A raindrop that reaches the ground is about a million times larger than a cloud droplet. For a rain droplet to form, these cloud droplets must join together in order to fall to Earth. This phenomenon is called the Bergeron process and the collision-coalescence process.
The Bergeron process relies on two peculiar properties of water. This is called being supercooled. This explains why airplanes collect ice when they pass through a liquid cloud made up of supercooled cloud droplets. Also, supercooled cloud droplets will freeze around solid particles that have a crystalline form.
These particles are named freezing nuclei and have given rise to the technology of cloud seeding. The second property, saturation, states that, "when air is saturated percent relative humidity with respect to water, it is supersaturated relative humidity greater than percent with respect to ice.
Therefore, when the relative humidity is percent with respect to water, then the relative humidity, with respect to ice is nearly percent. They grow large rapidly and then fall; on their descent, cloud droplets adhere to these ice crystals.
This chain reaction continues until larger crystals form producing snow crystals. The reason why snowflakes have a hexagonal shape is that the water molecules bind together to form a hexagonal shape and the snowflake is formed on particles called freezing nuclei. Therefore, even in summer months, snowflakes have formed, but melt before they reach the Earth's surface as rain droplets.
The spherical shape of rain droplets is due to another property of water called surface tension. Surface tension is the attractive force between particles in a liquid. Another, less obvious property of water is capillary action whereby the same properties of water that exist in surface tension exist here, as well, and that is the strong attraction between water molecules.
Capillary action is the attraction of the surface of a liquid to the surface of a solid. This can be evidenced by roots of plants taking up water to its leaves. How this fits into weather is that trees transpire, or give off some of this water to the atmosphere. Still another property of water is specific heat. Water has a relatively high specific heat.
This can explain why water takes much more heat to raise its temperature than land. There are other factors to explain the heat differential of water versus land. Water moves around where as land does not. This will cause water to heat more slowly than land. Another reason is that heat does not penetrate land deeply; therefore, only a thin layer above the land is heated. This is called conduction. Conduction is heat that is transferred from the ground to the air.
Molecularly speaking, conduction is the transfer of heat through matter by molecular activity. On land, there is a thin layer from the ground to the air above it that is being heated. Since water is moving, a much thicker layer of water is heated to just moderate temperatures.
That is why it is much more desirable to be near water in the hot summer months and the same holds true in the cold winter months. Land cools much more quickly because of the thin layer and since land is not mobile as water, land cools much more quickly than water. Also, the cooler water at the surface sinks and displaces the warmer water underneath; therefore, a larger mass of water will be cooled.
Since air is a poor conductor of heat, conduction is only important to the area of the ground; the air directly above the ground is, therefore, considered the least significant factor in heat transfer. Radiation plays a significant role in the transfer of heat from the land-sea surface to the atmosphere and vice versa. The heat that is gained by the lowest level of the atmosphere through radiation or conduction is usually transferred by convection.
It can only take place in liquids and gases. Relating specific heat and humidity, water vapor stores heat because it took energy to evaporate liquid water. This will explain why in the desert there are relatively colder nights to warmer days opposed to an area that is near a large body of water where increased evaporation can exist.
Another factor that contributes to the differences in heating of land and water is that land is opaque and heat is absorbed only at the surface, whereas water is transparent and allows more solar radiation to penetrate at a deeper level. Another factor is that evaporation, which is a cooling process, happens more from bodies of water than that from land. All of these factors help to explain why water warms more slowly and cools more slowly than land. The chemistry behind evaporation acting as a cooling agent is that it takes energy to evaporate and that energy comes from heat energy, thus making it feels cooler.
Other properties, such as density, can also be calculated using equations of state. In the pressure-temperature phase diagram of CO 2 , the boiling separates the gas and liquid region and ends in the critical point, where the liquid and gas phases disappear to become a single supercritical phase. At well below the critical temperature, e.
The system consists of 2 phases in equilibrium, a dense liquid and a low density gas. As the critical temperature is approached K , the density of the gas at equilibrium becomes denser, and that of the liquid becomes lower.
At the critical point, Thus, above the critical temperature a gas cannot be liquified by pressure. At slightly above the critical temperature K , in the vicinity of the critical pressure, the line is almost vertical. A small increase in pressure causes a large increase in the density of the supercritical phase.
Many other physical properties also show large gradients with pressure near the critical point, such as viscosity, the relative permittivity, and the solvent strength, which are all closely related to the density. A close look at supercritical carbon dioxide : A pressure vessel made of aluminum and acrylic is filled with pieces of dry ice.
The dry ice melts under high pressure, and forms a liquid and gas phase. When the vessel is heated, the CO2 becomes supercritical — meaning the liquid and gas phases merge together into a new phase that has properties of a gas, but the density of a liquid. Supercritical CO2 is a good solvent, and is used for decaffeinating coffee, dry cleaning clothes, and other situations where avoiding a hydrocarbon solvent is desirable for environmental or health reasons.
Freezing is a phase transition in which a liquid turns into a solid when its temperature is lowered to its freezing point.
Freezing, or solidification, is a phase transition in which a liquid turns into a solid when its temperature is lowered to or below its freezing point. All known liquids, except helium, freeze when the temperature is low enough. Liquid helium remains a liquid at atmospheric pressure even at absolute zero, and can be solidified only under higher pressure.
For most substances, the melting and freezing points are the same temperature; however, certain substances possess different solid-liquid transition temperatures. Most liquids freeze by crystallization, the formation of a crystalline solid from the uniform liquid. Crystalline Solid : Model of closely packed atoms within a crystalline solid. This is a first-order thermodynamic phase transition, which means that as long as solid and liquid coexist, the equilibrium temperature of the system remains constant and equal to the melting point.
Crystallization consists of two major events: nucleation and crystal growth. Nucleation is the step in which the molecules start to gather into clusters on the scale of nanometers , arranging themselves in the periodic pattern that defines the crystal structure.
The crystal growth is the subsequent growth of the nuclei that succeed in achieving and surpassing the critical cluster size. Nucleation Leads to Crystal Formation : When sugar is supersaturated in water, nucleation will occur, allowing sugar molecules to stick together and form large crystal structures.
Crystallization of pure liquids usually begins at a lower temperature than the melting point, due to the high activation energy of homogeneous nucleation. The creation of a nucleus implies the formation of an interface at the boundaries of the new phase. Some energy is expended to form this interface, based on the surface energy of each phase. If a hypothetical nucleus is too small, the energy that would be released by forming its volume is not enough to create its surface, and nucleation does not proceed.
Freezing does not start until the temperature is low enough to provide enough energy to form stable nuclei. In the presence of irregularities on the surface of the containing vessel, solid or gaseous impurities, pre-formed solid crystals, or other nucleators, heterogeneous nucleation may occur.
Heterogeneous nucleation is when nucleation occurs on a surface that the substance is in contact with. Freezing is almost always an exothermic process, meaning that as liquid changes into solid, heat is released. This may seem counterintuitive, since the temperature of the material does not rise during freezing except if the liquid is supercooled.
But heat must be continually removed from the freezing liquid, or the freezing process will stop. The energy released upon freezing, known as the enthalpy of fusion, is a latent heat and is exactly the same as the energy required to melt the same amount of the solid. Interactive: Phase Change : Matter exists as solids, liquids and gases, and can change state between these. The model shows a liquid material on the left small atoms. The amount of heat energy is shown by kinetic energy KE shading, with deeper shades of red representing more energetic atoms.
On the right side of the barrier is a solid material large atoms. Not much. If nothing else, chemists have another oddity for the already long list of odd properties of this life-giving chemical. Not convinced? By providing your email, you agree to the Quartz Privacy Policy. Skip to navigation Skip to content.
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