LECTURE 3 Flashcards
How did Galileo solidify the Copernican Revolution?
Earth can not be moving cause if it did objects in the air would be left behind
Non-circular orbits are not perfect
If Earth was really orbiting the sun we’d detect stellar parallax (objects closer to you move faster, but the stars are too far away so he thought that we didn’t detect parallax)
Overcoming Galileo’s First Objection
Galileo showed that objects will stay in motion unless a force acts to slow them down (newtons first law)
Realized that gravity would keep objects bound to Earth’s surface
Overcoming Galileo’s second objection
Sunspots on the sun were imperfections
Craters on the moon were imperfections
Overcoming the third objection
Galileo showed that stars must be much farther than Tycho thought, if they are farther away then lack of detectable parallax was no longer so troubling
How did Galileo also prove that not all objects orbit the earth (moons)
He saw that 4 moons are orbiting jupiter
How did Copernicus, Tycho and Kepler challenge Earth’s-centred idea?
Copernicus created a sun-centered model
Tycho provided the data that is needed to improve this model
Kepler found a model that fitted Tycho’s data
What are Kepler’s 3 laws of planetary motion?
- the orbit of each planet ellipse with the sun at one focus
- As a planet moves around its orbit it sweeps out equal areas in equal times
- More distant planets orbit the sun at slower average speeds
What was Gallileo’s role in solidifying the Copernican revolution
His experiments and observations overcome the remaining objections to the sun-centered solar system model
Explanation of Kepler’s laws
1678
Realized that the same physical laws that operate on Earth also operate in the heavens
Discovered laws of motion and gravity
Force= mass x acceleration
What determines the strength of gravity
Every mass attracts every other mass
Attraction is directly proportional to the product of their masses
Attraction is inversely proportional to the square of the distance between their centers
Consequences of Newton’s law of gravity
Ellipses are not the only orbital paths Orbits can be bound or parabola
+ Kepler’s first 2 laws
Energy
The ability to do something
Form of currency of Nature
Units: Joule, Electron Volt
Exmaples of Energy
Speed of Car = Kinetic energy
Intake from food
Operating at a metabolic rate (bruning Kcal)
Power
Energy used or produced per time
Unit: 1Watt = 1Joule/ s
Besal metabolic rates in humans
How do we experience light?
The warmth of sunlight tells us that light is a form of energy
How do light and matter interact
Absorption
Transmission
- Objects transmit light
-Objects block/ absorb light
Reflecting
Emission( release/ output)
Reflection and Scattering
Mirrors reflects light in a particular direction
Movie screen scaters light in all directions
Interactions between light and matter
Determins the appearance of everything around us
What is light
Particles of light are called photons
Light can either act like a wave or like a partical
Waves
pattern of motion that can carry energy without carrying matter along with it
Properties of Wave length
Wavelength- Distance between 2 wave peaks
Frequency- number of times per second that a wave vibrates up and down
Wave speed= wavelength x frequency
Light: Electromagnetic Waves
A light wave is a vibration of electric and maggnetic feilds (electrons)
Light interacts with charged particles through these electric and magnetic fields
Electro magnetic waves
Electric field and Magnetic fields that moves back and forth Electric fields moves up and down and magnetic fields move left and right
wavelength x frequency= speed of light= constant
Wavelength = 1/2cm
Frequency= 2 x 30 GHz= 60 GHz
Particles of Light
Photons
Each photon has a wavelength and a frequency
Energy of a photon depends on its frequency
Relationship with Frequency, energy, wavelength
High Frequency = high energy = small wavelength
Small frequency= small energy= large wavelength
What is light
Light can behave either like a wave or a particle
A light wave is a vibration of electric and magnetic fields
Light waves have a wavelength and a frequency
Photons are particles of light
What is the electomagnetic spectrum
Human eyes can not see most forms of light
The entire range of wavelengths of light is kown as the electromagnetic spectrum
