Models of the Universe and waves

Aristotle proposed that the heavens were composed of spheres to which the planets and moons were attached and which rotated at different velocities with the Earth at the centre. In the Geocentric model the Earth is at the centre of the solar system. Aristotle’s and Ptolemy’s model of the solar system Early Ideas about the Solar System

The Copernican Model: A Sun-Centered Solar System The Heliocentric System In a book called On the Revolutions of the Heavenly Bodies (that was published as Copernicus lay on his deathbed), Copernicus proposed that the Sun, not the Earth, was the center of the Solar System. In the heliocentric model the Sun is at the centre of the solar system. Polish astronomer Nicolai Copernicus ( ).

How were these models devised? Direct observations:- looking and recording the movement of planets in the sky relative to the background stars. Predicting the movement of planets. Using data recorded by previous scientists. With the development of telescopes more detailed observations could be made.

Galileo Galilei Four hundred years after it put Galileo on trial for heresy the Vatican is to complete its rehabilitation of the great scientist by erecting a statue of him inside the Vatican walls. The planned statue is to stand in the Vatican gardens near the apartment in which Galileo was incarcerated while awaiting trial in 1633 for advocating heliocentrism, the Copernican theory that the Earth revolves around the Sun. Galileo Galilei 15 February 1564 – 8 January 1642), commonly known as Galileo, was an Italian physicist, mathematician, astronomer and philosopher.

Galileo’s Observations (important) Galileo observed there were moons orbiting around Jupiter He argued that not everything orbits around the Earth. These observations of the moons orbiting Jupiter contradicted the Geocentric Model. Jupiter Moon Diagram shows how the position of the moons change.

Astronomy today Luminous objects in space give out visible light which allow scientists to study distant objects. Many objects in space do not give much visible light, but do give out other waves such as radio waves and microwaves. Different types of telescopes can be used to detect different types of waves

Longitudinal wave Example of a longitudinal wave: sound wave, p-waves

The vibration of the particles is parallel to the direction in which the is energy is carried

Transverse wave Examples of transverse waves: water waves and light waves. The vibration of the particles is perpendicular to the direction in which the energy is carried

Transverse waves - summary 1) Amplitude – this is “how high” the wave is: 2) Wavelength ( ) – this is the distance between two corresponding points on the wave and is measured in metres: Examples of transverse waves include: light waves and water ripples 3) Crest –the highest point of the wave 4) Trough – the lowest point of the wave

Frequency = number of waves per second Hertz (Hz) 1 second What is the frequency of the wave above? 3 Hz

The Wave Equation Wave speed (v) = frequency (f) x wavelength ( ) in m/s in Hz in m v f

1)A water wave has a frequency of 2Hz and a wavelength of 0.3m. How fast is it moving? 2)A water wave travels through a pond with a speed of 1m/s and a frequency of 5Hz. What is the wavelength of the waves? 3)The speed of sound is 330m/s (in air). When Dave hears this sound his ear vibrates 660 times a second. What was the wavelength of the sound? 4)Purple light has a wavelength of around 6x10 -7 m and a frequency of 5x10 14 Hz. What is the speed of purple light? Some example wave equation questions