GENERAL KNOWLEDGE Flashcards
“I think therefore I am” in Latin, please! Who said it?
“Cognito ergo sum” - Descartes.
Who popularized the “earth-centered” model of the universe? Why was it recognized?
Roman/Egyptian Astronomer - Claudius Ptolemy of Alexandria, Egypt (90-168 CE) accepted Aristotle’s view of an earth-centered universe. Based on observations he made with his naked eye, Ptolemy saw the Universe as a set of nested, transparent spheres - with Earth in the center. He posited that the Moon, Mercury, Venus, and the Sun (heavenly realm encased in these chrystaline spheres) all revolved around Earth (sub-lunar realm). Because real visible events in the sky seemed to confirm the truth of Ptolemy’s views (ex:the earth didn’t appear to move), and because this theory was backed by the Church, his ideas were accepted for centuries.
Who was the 1st prominent figures of the 16th Century to challenge the Ptolemaic system? How so?
Polish-born astronomer Nicolaus Copernicus (1473-1543) showed that some problems with Ptolemy’s system - like retrograde motions of planets could be resolved if we put the Sun at the center of the universe.
Who was the prominent German astronomer to challenge the Ptolemaic system? How so?
German astronomer-mathematician Johannes Kepler (1571-1630) showed that planets move in elliptical orbits, not in perfect circles.
Who was the infamous Italian Renaissance man to challenge the Ptolemaic system? How so?
3) Italian Renaissance man- Galileo Galilei (1564-1642) used a new instrument - the telescope- to disprove Ptolemy’s claim.
- He discovered that the Moon-like phases of Venus demonstrated that the neighboring planet had an orbit independent of Earth. This showed conclusively that Venus circled the Sun.
- based on his observations of the dark spots on the Sun that are caused by intense magnetic activity challenged the view that the heavens were a realm of perfection and hinted that the same fundamental laws might apply on Earth as in the heavens.
- He also showed that we do not experience the earth’s motion through space because like passengers on a ship, we share that motion.
What important theories did Isaac Newton contribute to our understanding of the universe?
Sir Isaac Newton (1642-1727) developed the three basic laws of motion and the theory of universal gravity, which together laid the foundation for our current understanding of physics and the Universe.
In Principia Mathematica (1687) he explained the elliptical orbits of the planets as the result of a universal force of attraction (gravity) that existed between all objects, in heavens and on earth.
What is the name of the female astronomer in the 17th Century and what did she discover and how did it contribute to our understanding of the universe?
American astronomer, Henrietta Leavitt (1868-1921) studied Cepheid variables and discovered the relationship between the intrinsic brightness of a variable star and the time it took to vary in brightness, making it possible for others to estimate the distance of these faraway stars, conclude that additional galaxies exist, and begin mapping the Universe.
A certain group of variable stars (Cepheid variables), fluctuate in brightness (luminosity) in a regular pattern called their “period.” This period ranges from about one day to nearly four months.
By comparing thousands of photographic plates, Leavitt discovered a direct correlation between the time it takes for a Cepheid variable to go from bright to dim and back to bright, and how bright the star actually is (its “intrinsic brightness”). The longer the period of fluctuation, the brighter the star. This meant that even though a star might appear extremely dim, if it had a long period it must actually be extremely large; it appeared dim only because it was extremely far away. By calculating how bright it appeared from Earth and comparing this to its intrinsic brightness, one could estimate how much of the star’s light had been lost while reaching Earth, and how far away the star actually was.
What did Edwin Hubble discover?
In the late 1920s, American astronomer, Edwin Hubble (1889-1953) showed that the entire universe is expanding.
Using the most technologically advanced telescope at the time and building on Leavitt’s work, Hubble located Cepheid variables so far away that they conclusively established the presence of other galaxies. By 1925, most astronomers agreed that our galaxy is one among a multitude — a small outpost in a Universe full of galaxies.
In 1926, building on the work of Vesto Slipher, who measured the red-shifts associated with galaxies more than a decade earlier, Hubble and his assistant, Milton Humason, discovered an odd fact: almost every galaxy he observed appeared to be moving away from the Earth. He knew this because the light coming from the galaxies exhibited red-shift. Light waves from distant galaxies get stretched by the expansion of the Universe on their way to Earth. This shifts visible light toward the red end of the spectrum. Hubble showed that all remote objects are shifted to the red end of the spectrum, which meant they were moving away from us. The more remote, the greater the red shift or the rate at which they were moving away from the earth.
By 1929 they had formulated what became known as Hubble’s Law.
What is the name of the German glass maker who invented the spectroscope, what does it do?
In 1814, German glass maker, Joseph von Fraunhofer, invented the spectroscope - a prism-like device that splits light into its component wavelengths. He identified dark “absorption lines” in the spectra of starlight. These correspond to particular elements in the stars themselves, because each element absorbs light energy at different frequencies.
What is the name of the 19th Century American astronomer that first studied the Doppler effect with light?
In the late 19th century, Vesto Slipher showed that some stellar absorption lines were shifted away from their expected frequencies. Slipher interpreted these shifts as the result of a Doppler effect - an apparent change in wavelengths caused by the relative movements of two bodies. This meant that changes in absorption lines could tell us whether distant objects were moving toward or away from us and at what speed.
Galaxies and stars moving away from us have their light stretched out, making it more red. And stars moving toward us have their light compressed making it more blue.
How do pigments/ dyes work?
Subtractive colour mixing occurs when the source of colour is pigment/dye. The refractive properties of the molecules within the pigments/dyes absorb some wavelengths or lights and reflect others. So when these dyes subtract/take away the wavelength by absorbing them, we are left with the colours that are reflective.
What are the different ways atoms can become excited - light sources?
There are 2 principal sources of light: incandescent (temperature - hotter temp-more energy, more light) and luminance (chemical changes, electro-luminance, re-emittance).
What are Newton’s 3 Laws of Motion?
Newton’s three Laws of Motion are:
01 - Every body continues at rest or in motion in a straight line unless compelled to change by forces impressed upon it. (Galileo first formulated this, and Newton recast it.)
02 - Every change of motion is proportional to the force impressed and is made in the direction of the straight line in which that force is impressed. (A planet would continue outward into space but is perfectly balanced by the Sun’s inward pull, which Newton termed “centripetal” force.)
03 - To every action there is always opposed an equal reaction, or the mutual action of two bodies on each other is always equal and directed to contrary parts.
What is the Law of Universal Gravitation and who theorized it?
Putting these laws together, Newton was able to state the Law of Universal Gravitation: the gravitational attraction between two bodies decreases rapidly as the distance between them increases.
What are Cepheid Variables and what are they used for?
Cepheid Variables are very luminous stars, 500 to 300,000 times greater than the sun, with short periods of change that range from 1 to 100 days. They are pulsating variables in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude. They are therefore useful in measuring interstellar and intergalactic distances.
