What is Plasma, what are its uses, and where does it come from?

What is plasma? Plasma is considered the 4th state of matter. Plasma is a cloud of protons, neutrons and electrons where all the electrons have come loose from their respective molecules and atoms. And it could reach up to a whopping 10,000 kelvins or 17000 degrees fahrenheit. Akshat Mahajan from BSc Physics UCLA says, “A plasma is any ionised (charged) gas. It doesn't have to be fully charged (i.e. completely stripped of all its atoms or completely ionised) - even partial ionisation is sufficient to call something a plasma.” What he is basically saying is the plasma can occur wherever a charge is missing. And plasmas can be quite beautiful. An aurora borealis mainly is solar wind flowing past the earth, and a solar wind is mainly made out of plasma, which is held by the earth's magnetic field.

Plasma is used in many applications. Plasma is used in television, neon signs and fluorescent lights. Stars, lightning, and some flames consist of plasma. ThoughtCo says, “More exotic sources of plasma include particles in nuclear fusion reactors and weapons, but everyday sources include the Sun, lightning, fire, and neon signs. “ Other examples of plasma include static electricity, plasma balls, and the ionosphere.

Most people know plasma from a popular film called star wars. More specifically the lightsabers they use to fight with. These blades, are made out of plasma powered by the fictional kyber crystal. Unfortunately, it is not very easy to create something with that power, knowing that it will take 20 megawatts or 20 million watts just to melt through through steel. And that can power about 14000 households before the battery goes out.

Overall plasma is a very extraordinary thing that most people don't know about. Some things people don't know about plasma it is a state of matter. Which is mainly because when taught in school they only learn the main three. Pluto.space.swri.edu says, “A plasma is a hot ionized gas consisting of approximately equal numbers of positively charged ions and negatively charged electrons. The characteristics of plasmas are significantly different from those of ordinary neutral gases that is why it is the 4th state of matter”.Therefore plasma is the 4th state of matter.

(Source: Neil Lapsia)

Acoustics

Acoustics is the science of sound and someone who studies acoustics is called an acoustician.

There are many kinds of sound and many ways that sound affects our lives. For example, we use sound to talk and sound is important for designing musical instruments, concert halls, surround sound stereo and hearing aids. Sound can also be used to find oil and gas, to study earthquakes and climate change, and to make sure that the baby in a mother’s womb is healthy. There are the sounds humans can hear, but there are also sounds that only some animals can hear, like a dog whistle.

There are a lot of different acoustics fields of study. If you study acoustics, you might study the production, control, transmission, reception, or effects of sound on people, animals or even objects.

Mathematical Biology

Mathematical and theoretical biology is a branch of biology which employs theoretical analysis, mathematical models and abstractions of the living organisms to investigate the principles that govern the structure, development and behavior of the systems, as opposed to biology which deals with the conduction of experiments to prove and validate the scientific theories. The field is sometimes called mathematical biology or biomathematics to stress the mathematical side, or theoretical biology to stress the biological side. Theoretical biology focuses more on the development of theoretical principles for biology while mathematical biology focuses on the use of mathematical tools to study biological systems, even though the two terms are sometimes interchanged.

Mathematical biology aims at the mathematical representation and modeling of biological processes, using techniques and tools of applied mathematics and it can be useful in both theoretical and practical research. Describing systems in a quantitative manner means their behavior can be better simulated, and hence properties can be predicted that might not be evident to the experimenter. This requires precise mathematical models.

Because of the complexity of the living systems, theoretical biology employs several fields of mathematics, and has contributed to the development of new techniques.

(Ref: Wikipedia)

Laser

How do laser engineers use physics?

We use geometric optics to design the optical resonator. We use wave optics to predict the performance of the laser and resonator.

Depending on the type of laser we may use chemical kinetics, gas dynamics, and other disciplines to predict the flow of gases in the gain medium. We may use solid state physics to model the gain medium.

We use quantum mechanics of molecules and quantum electronics to model the states involved in the energy process of pumping and extracting energy. We use thermal and statistical physics to determine how and by how much to cool the gain medium. We may make use of stimulated brillouin scattering to control the wavefront errors introduced by a non-homogeneous gain medium.

Once the beam exits from the resonator, we make use of interference to determine the wavefront error of the laser beam. We then make use of some fancy processing to calculate the best fit deformable mirror surface but avoiding unstable eigen modes that can latch up.

We use knowledge of diffraction to determine how large the beam must be expanded to propagate the distance we need to place a spot on a distant object.

We use knowledge of the atmospheric density statistics to determine the structure function along the propagating path to know how much wavefront aberration and scintillation we will get. If it is too much, we propagate additional laser beams along the path to remotely measure the atmospheric turbulence so that we can pre-correct for it.

We use computational fluid dynamics to determine the air flow around the laser telescope to minimize he impact on the laser beam.We have to use physics to determine how much laser signal we will get back and since it is not enough, ways to use the signal that we will get.

We may use Doppler shifting of the reflected laser beam to help determine how fast the object is moving. We may use short pulses and time of flight to determine how far away the object is. Rayleigh scatter theory helps determine if we will be able to detect where the beam is before it gets to the object of interest.

(Ref: Bill Otto)

Molecular Astrophysics

Molecular Astrophysics concerns the study of emission from molecules in space. Lew Snyder recently presented a list of the 110 currently known interstellar molecules. These molecules have large numbers of observable transitions. To find specific frequencies, try Herb Pickett's Molecular Spectroscopy Home Page or Frank Lovas' list of recommended rest frequencies. Tom Kuiper has put together an explanation of molecular radio spectroscopy for emission lines. Lines may also be observed in absorption--for example the highly redshifted lines seen against the gravitationally lensed quasar PKS1830-211.

High energy radiation, such as ultraviolet light, can break the molecular bonds which hold atoms in molecules. In general then, molecules are found in cool astrophysical environments. The most massive objects in our Galaxy are giant clouds of molecules and dust, creatively named Giant Molecular Clouds. In these clouds, and smaller versions of them, stars and planets are formed. One of the primary fields of study of molecular astrophysics then, is star and planet formation. Molecules may be found in many environments, however, from stellar atmospheres to those of planetary satellites. Most of these locations are cool, and molecular emission is most easily studied via photons emitted when the molecules make transitions between low rotational energy states. One molecule, comprised of the abundant carbon and oxygen atoms, and very stable against dissociation into atoms, is carbon monoxide, CO. The wavelength of the photon emitted when the CO molecules falls from its lowest excited state to its zero energy, or ground, state is 2.6mm, or 115 gigahertz (billion hertz). This frequency is a thousand times higher than typical FM radio frequencies. At these high frequencies, molecules in the Earth's atmosphere can block transmissions from space, and telescopes must be located in dry (water is an important atmospheric blocker), high sites. Radio telescopes must have very accurate surfaces to produce high fidelity images. NRAO pioneered development of accurate antennas and high frequency receivers, and the development of molecular astrophysics, with the 11m radio telescope. In 1982, the surface of the 11m was replaced with a much more accurate 12m surface.

(Ref: National Radio Astronomy Observatory)

Acoustics

Acoustics is defined as the science that deals with the production, control, transmission, reception, and effects of sound (as defined by Merriam-Webster). Many people mistakenly think that acoustics is strictly musical or architectural in nature. While acoustics does include the study of musical instruments and architectural spaces, it also covers a vast range of topics, including: noise control, SONAR for submarine navigation, ultrasounds for medical imaging, thermoacoustic refrigeration, seismology, bioacoustics, and electroacoustic communication.

(Ref: BYU Acoustics Research Group)

The perceptional capabilities of the human ear, three different frequency ranges are distinguished. The range of hearing stretches from about 16 Hz to 16 kHz. Lower frequencies are called infra-sound, higher frequencies are called ultra-sound.

The field of acoustics can be subdivided into several special topics such as:

Theoretical acoustics, Nonlinear acoustics, Underwater acoustics, Ultrasound, Vibrations, Noise control, Room acoustics, Building acoustics, Electroacoustics, Acoustics of the ear.

Speed of sound in air:

temperature [◦C]   | speed of sound c [m/s]

   0                                                                 331.3

                        10                                      337.3

                        20                                      343.2

Density of air at sea level:

temperature [◦C]   |  density of air ρ [kg/m3 ]

        0                                              1.292

     10                                               1.247

     20                                               1.204

Acoustic impedance:

temperature [◦C]   |   ρc [Ns/m3 ]

       0                                       428.0

    10                                       420.5

    20                                       413.3

(Ref: Kurt Heutschi)

Dark Matter Physics

Dark matter is composed of particles that do not absorb, reflect, or emit light, so they cannot be detected by observing electromagnetic radiation. Dark matter is material that cannot be seen directly. We know that dark matter exists because of the effect it has on objects that we can observe directly.

Dark matter may account for the unexplained motions of stars within galaxies. Computers play an important role in the search for dark matter data. They allow scientists to create models which predict galaxy behavior. Satellites are also being used to gather dark matter data. In 1997, a Hubble Space Telescope image revealed light from a distant galaxy cluster being bent by another cluster in the foreground of the image. Based on the way the light was bent, scientists estimated the mass of the foreground cluster to be 250 times greater than the visible matter in the cluster. Scientists believe that dark matter in the cluster accounts for the unexplained mass.

Scientists have produced many theories about what exactly dark matter may be normal objects such as cold gasses, dark galaxies, or massive compact halo objects (called MACHOs, they would include black holes and brown dwarfs). Other scientists believe that dark matter may be composed of strange particles which were created in the very early universe. Such particles may include axions, weakly interacting massive particles (called WIMPs), or neutrinos.

Understanding dark matter is important to understanding the size, shape and future of the universe. The amount of dark matter in the universe will determine if the universe is open (continues to expand), closed (expands to a point and then collapses) or flat (expands and then stops when it reaches equilibrium). Understanding dark matter will also aid in definitively explaining the formation and evolution of galaxies and clusters. As a galaxy spins it should be torn apart. This does not happen, so something is holding the galaxy together. The something is gravity; the amount of gravity required to do this, however, is enormous and could not be generated by the visible matter in the galaxy.

(REF: StarChild )