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Across
  1. 4. Refers to any information, data, or material that supports, verifies, or substantiates a claim, hypothesis, or belief. It is used in various contexts, such as science, law, and everyday decision-making, to establish the truth or validity of a statement or theory.Key aspects include:Empirical Evidence: Information obtained through observation or experimentation, often used in scientific research.Testimonial Evidence: Statements made by witnesses or experts, commonly used in legal settings.Documentary Evidence: Written or recorded materials, such as contracts, letters, or digital files.Physical Evidence: Tangible objects or traces, like fingerprints or DNA, often used in forensic investigations.Purpose:To confirm or refute a hypothesis or assertion.To provide a basis for belief or action.To support or challenge arguments in a debate or legal case.Evaluation:Relevance: How directly relates to the matter at hand.Reliability: The trustworthiness of the source.Sufficiency: Whether the quantity and quality are adequate to support a conclusion.
  2. 5. The distance that light travels in a vacuum over one year. Light moves at a speed of approximately 299,792 kilometers per second (or about 186,282 miles per second). Over a full year, this speed allows light to cover a vast distance, which is used as a unit of measurement to describe the vast spaces between stars, galaxies, and other celestial objects. It helps astronomers express how far away objects are in the universe.
  3. 7. is the collection of celestial bodies, including a star at its center, which is the Sun, and the various objects that orbit around it due to gravitational forces. These objects include eight major planets, their moons, dwarf planets like Pluto, asteroids, comets, and other small bodies.Key features include:The Sun: The central star, which provides the gravitational pull that keeps all the other objects in orbit and is the primary source of light and heat.Planets: Eight primary planets that revolve around the Sun, including Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Each planet has its own set of moons, except for Mercury and Venus.Dwarf Planets: Smaller planetary bodies that also orbit the Sun but are not classified as full-fledged planets. Pluto is one of the most famous examples.Asteroids and Comets: Smaller rocky and icy bodies that also orbit the Sun, primarily found in the asteroid belt between Mars and Jupiter, and in the Kuiper Belt beyond Neptune.The Oort Cloud: A distant, spherical shell of icy objects surrounding the outermost regions, believed to be the source of long-period comets.This system represents the local environment of our planet Earth and is a small part of the larger galaxy.
  4. 10. refers to the vast, all-encompassing space that includes everything that existsโ€”matter, energy, planets, stars, galaxies, and the vast voids between them. It encompasses all of space and time, including the physical laws and constants that govern them.Key aspects include:Galaxies: Massive systems of stars, stellar remnants, gas, dust, and dark matter bound together by gravity. Galaxies are the fundamental building blocks of the cosmos.Expansion: The cosmos is expanding, with galaxies moving away from each other over time. This expansion is driven by a force often referred to as dark energy.Cosmic Background Radiation: A faint glow present throughout the cosmos, which is a remnant of the early stages following the Big Bang.Dark Matter and Dark Energy: Mysterious substances that do not emit light or energy but have significant effects on the structure and expansion of the cosmos.Time and Space: The cosmos includes all dimensions of space and the progression of time, forming a continuous fabric that affects the behavior of matter and energy.This term covers everything from the smallest particles to the largest structures, and it represents the totality of existence as we understand it.
  5. 11. a well-substantiated explanation for a wide range of phenomena in the natural world, based on a body of evidence and repeatedly tested and confirmed through observation and experimentation. This type of explanation provides a framework for understanding and predicting how certain aspects of the universe behave. It is developed through the scientific method, beginning with hypotheses that are rigorously tested, refined, and supported by empirical data. Theories are widely accepted by the scientific community when they consistently explain and predict outcomes across various contexts.
  6. 13. A massive, gravitationally bound system that consists of stars, stellar remnants, interstellar gas, dust, and dark matter. They are the fundamental building blocks of the universe, and they come in various shapes, sizes, and compositions. They can range from dwarf galaxies, with just a few billion stars, to giants with trillions of stars.Key components and features of galaxies include:Stars: The most visible components range from young, hot, blue stars to older, cooler, red stars.Nebulae: Clouds of gas and dust within that can be the birthplaces of new stars.Star Clusters: Groups of stars that are gravitationally bound to each other. These can be open clusters or globular clusters.Dark Matter: An invisible substance that makes up a significant portion of its mass, inferred from gravitational effects on visible matter.Supermassive Black Holes: Have a supermassive black hole at their center.Classification: Often classified into several types based on their shape and structure:Spiral Galaxies: Characterized by a flat, rotating disk with spiral arms, like the Milky Way.Elliptical Galaxies: Rounded or oval in shape with little structure and typically older stars.Irregular Galaxies: Lack a defined shape and structure, often chaotic in appearance.Lenticular Galaxies: Have features of both spiral and elliptical galaxies, with a central bulge and a disk but no prominent spiral arms.Often in groups or clusters, and play a crucial role in the large-scale structure of the cosmos.
  7. 14. A fundamental unit of measurement in a given system of units that is defined independently and not derived from other units. In the International System of Units (SI)Meter (m) - the unit of length.Kilogram (kg) - the unit of mass.Second (s) - the unit of time.Ampere (A) - the unit of electric current.Kelvin (K) - the unit of thermodynamic temperature.Mole (mol) - the unit of amount of substance.Candela (cd) - the unit of luminous intensity.Each is defined by a specific, universally accepted standard, such as the speed of light for the meter or the fixed numerical value of the Planck constant for the kilogram. These definitions are crucial for ensuring consistency and accuracy in scientific measurements globally.
  8. 15. The galaxy that contains our Solar System. It is a vast, spiral-shaped galaxy with a barred structure at its center, where billions of stars, along with gas, dust, and dark matter, are gravitationally bound together. The Milky Way is part of a group of galaxies known as the Local Group, which also includes the Andromeda Galaxy and several smaller galaxies.Key characteristics of the Milky Way Galaxy include:Structure: has a flat, rotating disk with spiral arms that extend outward from a central bulge. The spiral arms are regions of active star formation and contain many young, bright stars.Size: About 100,000 light-years in diameter and contains an estimated 100 to 400 billion stars.Location of the Solar System: Our Solar System is located in one of the spiral arms, known as the Orion Arm or Orion Spur, about 27,000 light-years from the galactic center.Central Black Hole: At the heart lies a supermassive black hole called Sagittarius A*, which has a mass equivalent to about 4 million suns.Appearance: Appears as a band of light stretching across the night sky, which is the combined glow of the dense region of stars within the galaxy's disk.One of billions of galaxies in the universe, but it holds special significance as the home of our planet, Earth.
Down
  1. 1. (AU, or au), a unit of length effectively equal to the average the distance between Earth and the Sun, is defined as 149,597,870.7 km.
  2. 2. Regions in space where an enormous amount of mass is packed into a tiny volume. This creates a gravitational pull so strong that not even light can escape.
  3. 3. is a powerful and luminous explosion that occurs when a star reaches the end of its life cycle. This event marks the dramatic final stage of a star's existence, during which it sheds its outer layers into spaceKey aspects of this explosion include:Energy Release: The explosion releases an immense amount of energy, outshining an entire galaxy for a brief period. This energy disperses the star's outer material into space.Star Death: The cause of the explosion can vary. In one scenario, a star with a mass several times greater than the Sun collapses under its own gravity. In another, a star in a binary system accumulates matter from a companion star until it reaches a critical point.Remnants: After the explosion, the core left behind can become a neutron star or a black hole, depending on its mass. The ejected material enriches the surrounding space with heavy elements, which can contribute to the formation of new stars and planets.Observations: These events are important for astronomers as they provide insights into the life cycles of stars and the chemical evolution of galaxies.This type of stellar explosion plays a crucial role in the dynamics of galaxies and the synthesis of elements in the universe.
  4. 6. measured by the acceleration that it gives to freely falling objects. At Earth's surface the acceleration of gravity is about 9.8 metres (32 feet) per second per second. Thus, for every second an object is in free fall, its speed increases by about 9.8 metres per second.
  5. 8. A spiral-shaped galaxy is a type of galaxy characterized by a flat, rotating disk with a central bulge and extended arms that spiral outward. The disk contains stars, gas, and dust, while the central bulge is typically composed of older, redder stars.Key features include:Disk Structure: The disk is where most of the galaxy's stars, including younger, hotter stars, are located. The arms of the disk are often filled with nebulae, where new stars are born.Central Bulge: A densely packed region at the center of the galaxy, containing older stars and often a supermassive black hole.Spiral Arms: These are prominent, winding structures that extend outward from the central bulge. They are sites of active star formation and are often visually striking.Halo: Surrounding the disk and bulge is a spherical region of stars, star clusters, and dark matter, known as the halo.Examples of this type of galaxy include our own galaxy, which has a similar structure, as well as others like the Andromeda Galaxy. These galaxies are among the most common and well-studied in the universe.
  6. 9. is a vast cloud of gas and dust in space, often serving as a region where new stars are born or the remnants of dead or dying stars. Various shapes and sizes are among the most visually striking objects in the night sky.There are different types of nebulae, including:Emission Nebulae: These glow brightly due to the ionization of gas by nearby hot stars. An example is the Orion Nebula.Reflection Nebulae: These do not emit their light but shine by reflecting the light from nearby stars.Planetary Nebulae: These form when a dying star sheds its outer layers, creating a shell of gas around the star's core. The Ring Nebula is a well-known example.Dark Nebulae: These are dense clouds of gas and dust that block light from objects behind them, making them appear as dark patches against brighter backgrounds, like the Horsehead Nebula.Nebulae are essential in the life cycle of stars, providing the material from which new stars and planetary systems are formed.
  7. 12. a type of galaxy characterized by its ellipsoidal shape and smooth, nearly featureless brightness profile. Unlike spiral galaxies, elliptical galaxies lack a well-defined structure of arms and are generally more spherical or elongated in appearance.Shape: They range from nearly spherical (classified as E0) to highly elongated (classified up to E7).Stellar Population: Elliptical galaxies consist mostly of older, low-mass stars and have very little new star formation.Interstellar Medium: They contain little interstellar gas and dust, which is why star formation is minimal.Size and Mass: They can vary significantly in size, from small dwarf ellipticals to giant ellipticals, which can be among the largest galaxies in the universe.Dynamics:The stars in elliptical galaxies typically move in random orbits, leading to their smooth appearance.Often found in the centers of galaxy clusters and are thought to have formed through the merging of smaller galaxies.