Understanding the Universe: Celestial Bodies and Energy
Geocentric System
The geocentric system is a planetary model which states that the Earth is the center of the Universe, and the other planets and the Sun revolve around it.
Heliocentric System
The heliocentric system is a planetary model where the Sun is the center of our system, and the other planets, including Earth, revolve around it.
Astrophysics
Astrophysics is the branch of astronomy that studies the structure, composition, and evolution of the Universe.
Light-Year
A light-year is the distance that light travels in one year, moving in a vacuum at a speed of approximately 300,000 km/s. It is equivalent to 9.5 trillion km.
Big Bang
The Big Bang is a model that attempts to explain the formation of the universe from the expansion of a point that continues to create space and energy. This expansion resulted in the energy in the universe being counted as particles, the constituents of matter.
Galaxies
Galaxies are groupings of billions of stars, rotating around a common axis. They are usually elliptical, spiral, or irregular.
Milky Way
The Milky Way is the spiral galaxy where Earth is located.
Stars
Stars are celestial bodies mainly composed of hydrogen, whose atoms fuse to produce helium, emitting light and heat.
Supernova
A supernova is the final stage of a star’s explosion, with a mass greater than 1.5 times that of our Sun, also called a neutron star.
Black Hole
A black hole is the final state of a star with a mass at least three times that of the Sun. Its force of attraction is so great that not even light can escape.
Planet
Planets are objects without their own light that revolve around a star, formed by material that was not agglomerated for it, and that have other smaller objects called satellites revolving around them.
Law of Universal Gravitation
Two bodies attract each other with a force directly proportional to their masses and inversely proportional to the square of the distance that separates them.
Centripetal Force
Centripetal force is the central force caused by the gravitational interaction between two bodies, causing one to revolve around the other.
Weight of a Body
The weight of a body is the force with which the Earth or any other planet or star attracts an object.
Gravity
Gravity is the acceleration with which a body falls freely. Its value depends on the mass and radius of the planet that attracts it.
Cosmology
Cosmology is the branch of astronomy that studies the origins, structure, and evolution of the Universe.
Energy
Energy is the capacity of a system to produce change in itself or its surroundings.
Work
Work is the energy transmitted by a force. A force transmits energy when it does work. The work done by a force acting on a body is equal to the product of the force by the displacement experienced by the point of application of the force in the same direction of the movement. W = F(ΔX) = FΔX. Its unit in the international system, as well as that of energy, is the joule (J).
Machine
A machine is any device that allows the transmission or change of a force to perform a certain task. The work supplied to the machine is equal to the work done by the resistance force. In a simple machine, there is a driving force and a resistance force. The most important simple machines are the lever, the inclined plane, and the hydraulic press.
Lever
A lever is a simple machine consisting of a rigid bar that rotates on a point called the fulcrum. It is of the first kind if the fulcrum is located between the driving force and the resistance force, of the second kind if the resistance force is between the fulcrum and the driving force, and of the third kind if the driving force is in the middle.