Physics and History of Cosmology Midterm Practice

Flashcards covering key cosmological figures, physics principles of motion and relativity, and astronomical facts based on midterm review questions.

Johannes Kepler

The first person to determine that planets move in elliptical orbits.

Newton's Laws of Motion applicability

Laws valid only in an inertial rest frame and for speeds much less than $c$.

Ole Roemer

The scientist who performed the first measurement of the speed of light using observed variations in the orbital period of Jupiter's moon Io.

Electromagnetic Wave Field Orientation

The electric and magnetic fields point perpendicularly to each other and to the direction of propagation of the wave.

Gravitational Mass

The quantity that explains why objects in free-fall all fall at the same rate $g$.

Special Relativity Validity

Einstein's theory that is valid only in inertial reference frames.

Proxima Centauri

The nearest star to Earth, located $4\,light\,years$ away.

Epicycles

Features introduced by Ptolemy into his geocentric model to explain why planets were observed to sometimes stop and reverse their motion (retrograde motion).

Saturn's Moon Orbital Variations

The observation that orbital periods of Saturn's moons become longer as Earth moves away from Saturn because of the finite speed of light.

Galileo's Observation of Venus

The discovery of the phases of Venus, which showed that Venus orbits around the sun.

Tycho Brahe's Contribution

His principal contribution to cosmology was his precise measurements of the orbits of planets.

Anaximander's Universe Model

The first model of the universe in which the Earth was described as a freely floating object in space without mechanical support.

Aristarchus of Samos

The first person to propose that the Earth orbits the sun and to measure the relative sizes of the sun, Earth, and moon.

Electromagnetic Spectrum Order

Ranked by increasing wavelength: Gamma rays, x rays, ultraviolet, visible, infrared, microwave, radio.

Escape Velocity Kinetic Energy

If an object is launched with exactly the escape velocity, its kinetic energy after it has escaped to infinity from the planet will be zero.

X-ray vs. Gamma-ray

Compared to a gamma-ray, an x-ray photon has less energy.

Solar Wind Speed Cause

Solar wind particles are highly energetic because the sun's high temperature gives them large kinetic energies.

Inertial Mass

The quantity that tells you how difficult it is to get an object moving.

Venus Magnetic Field Absence

The main reason Venus lacks a magnetic field is that it rotates too slowly.

Kepler's Three Laws Importance

These laws were critical because they led Newton to formulate his laws of gravitation and motion.

Visible Universe Size

The visible universe is approximately $46\,billion\,light\,years$ in size.

Solar Wind Composition

A stream of protons and electrons (electrically charged particles) from the sun.

Aristarchus Heliocentric Reasoning

Aristarchus decided the Earth orbited the sun because he determined the sun is much bigger than the Earth.

Newtonian Simultaneity

In the context of Newton's laws, if you see two flashes simultaneously, a moving friend (Bernice) will also see both flashes as simultaneous.

Length Contraction (Spaceship)

The distance between the Earth and a star system appears shorter as seen from a moving spaceship compared to the distance seen from Earth.

Andromeda Galaxy Distance

The Andromeda galaxy is located $2.5\,million\,light\,years$ away.

Speed of Light Constancy

The postulate that the speed of light in vacuum will always be observed to be $c = 300,000\,km/s$ by all observers, irrespective of their motion.

Principle of Inertia

The physics principle stating that an object will move with constant speed and direction if there are no forces acting on it.

Aurora

The northern or southern lights caused by solar wind particles funneled to the Earth's poles by the Earth's magnetic field.

Earth's Magnetic Field Origin

Generated by the Earth's rotation in combination with free electric charges in its hot liquid core.

Cosmic Rays

High-energy particles traveling through intergalactic space that are mostly composed of protons.

Relativistic Simultaneity

In Einstein's special theory of relativity, an observer moving from left to right (Bernice) would see a flash on the right occur first if both were seen simultaneously by a stationary observer.

Principle of Relativity

The statement that the laws of physics are the same in all inertial reference frames.

Photon

A quantum particle of light.

Electromagnetic Wave Initiation

To create light or an electromagnetic wave, one must have accelerating electric charges.

Philolaus' Model

The first model of the universe in which the Earth was not at the center but placed in orbit around another celestial body.

Refractive Index Speed Limitation

Inside matter, particles with mass (such as neutrinos) can travel faster than light in that specific medium.

Inertial Reference Frame

A reference frame that moves with constant speed and direction.

Virgo Supercluster

The galaxy supercluster that contains the Local Group and the Milky Way.