Presentation on theme: "How to Study the Universe"— Presentation transcript:
1 How to Study the Universe Question:How are we going to be able to “understand”what we see in the universeif all we have to work withis the LIGHT that we see?
2 Answer:We will apply some basic “knowledge” that we already know about the universe (on earth) to what we see beyond the earth.Using this “basic knowledge” we can examine what we see and create an explanation or hypothesis that we can test.We then use the SCIENTIFIC METHOD to test our hypothesis.This allows us to understand and explain what we observe.ALL of THIS CAN BE ACCOMPLISHED FROM A DISTANCE.
3 We will use our “Problem Solving Techniques.” ********************************************************We will begin our examination by asking “What is given”.We can sayWe have a good knowledge of things on our earth.We understand the concepts ofmassmotionforceenergyelectromagnetic radiation (to be examined later)
4 We will apply our knowledge of these conceptsbeyond the earthto attempt to understandwhat we observe in the universe.
5 Next we must ask “What is asked for”? What do we see when we observe the universe?The answer is we observe some of the same things we see on our earth.We observe some of the following:- mass moving (orbiting planets, moons)- light patterns (red shifts, Doppler movements)4. So, to understand these observations in space- we need to understandhow these “observations” occur on our earth.
6 Having identified the things we are looking for we can ask “What type of problem is this”?Just like we do on earth.Therefore we must examine the relationships betweenmassmotionforceenergyelectromagnetic radiation (later)So we begin our journey with a review of these concepts.
8 MOTIONMotion = a mass moving Two types of movement- linear (straight line)- angular (non-linear can be-- a circle or an ellipse)
9 VELOCITY Velocity = (the speed) + (direction) of the motion of mass. Expressed as a VECTOR QUANTITYMAGNITUDEexpressed as distance/time (10km/hr)DIRECTIONexpressed in a direction (west)30 km/hrwest
10 How do we describe motion? Precise definitions to describe motion:Speed: Rate at which object movesExample: speed of 10 m/sVelocity: Speed and directionExample: 10 m/s, due eastAcceleration: Any change in velocity; units of speed/time (m/s2)Basic vocabulary of motion. Emphasize that turning, slowing, and speeding up are all examples of acceleration.
11 Acceleration Magnitude increases Direction changes Magnitude decreases Acceleration: Any change in velocity; units of speed/time (m/s2)
12 Force Is defined as anything that can cause a change in the momentum of an objectWe observe it as a change in themotion of an objectPUSHPULL
13 Momentum Because there are two types of motion (linear and non-linear) we have two types of momentumLinear Momentum = (mass) x (velocity)Angular momentum = (mass) x (velocity) x (radius of circle)
14 What type of motion do we observe? We can observe a mass to do three things:1. remain at rest (no motion)2. move at a constant velocity-- in a straight line (linear motion)-- in circular direction (angular motion)3. accelerate, this can be can be a change in-- speed-- direction-- both
15 SpaceIf we can understand the relationship betweenthese types of motion andthe concepts of mass, force and energywe can explain the motion we observe.It doesn’t matter of the motion is on earth or space.Earth
16 Fortunately,Isaac Newton put all of this togetherin his famousthree laws of motion.
17 How did Newton change our view of the universe? He realized the same physical laws that operate on Earthalso operate in the heavens:one universeHe discovered laws ofmotion andgravity.Much more: Experiments withlightfirst reflecting telescope,calculus…Sir Isaac Newton (1642–1727)
18 An object moves at Newton’s first law of motion constant velocity unless a net force actsto change its speed and/oror direction.You may wish to discuss the examples in the book on P. 83–84.If a body is at rest it will remain at rest.If a body is in motion it will remain in motion.
19 Newton’s second law of motion Force = mass acceleration.F = ma
20 Newton’s third law of motion For every force,there is always an equaland oppositereaction force.
21 ENERGY We have now seen the mass in motion, but what causes the mass to move?The answer isENERGYEnergy is what makes matter move
22 Basic Types of Energy Kinetic (motion) Radiative (light) Stored or potentialEnergy can change type but cannot be destroyed.
23 Thermal Energy: The collective kinetic energy of many particles (for example, in a rock, in air, in water)Thermal energy is related to temperaturebut it is NOT the same.Temperature is the average kinetic energyof the many particles in a substance.Students sometimes get confused when we’ve said there are three basic types of energy (kinetic, potential, radiative) and then start talking about subtypes, so be sure they understand that we are now dealing with subcategories.
24 Temperature Scales Astronomy uses the Kelvin scale. Use this figure to review temperature scales.Astronomy uses the Kelvin scale.
25 Gravitational Potential Energy on Earth it depends on…an object’s mass (m).the strength of gravity (g).the distance an objectcould potentially fall.We next discuss two subcategories of potential energy that are important in astronomy: gravitational potential energy (this and next slide) and mass-energy.
26 Gravitational Potential Energy in Space an object or gas cloudhas more gravitational energywhen it is spread out thanwhen it contracts.A contracting cloudconverts gravitational potential energyto thermal energy.We next discuss two subcategories of potential energy that are important in astronomy: gravitational potential energy and mass-energy.We will examine this more closely when we look at the formation of the solar system and stellar evolution.
27 Let us review, we have observed - mass moving- mass having momentum- the presence of a force- causes motion- which tells us that- energy is involved
28 E = mc2 Mass itself is a form of potential energy. A small amount of masscan release agreat deal of energy.
29 Now we must introduce two more very important concepts The conservation of total energyThe conservation of total momentum
30 Conservation of Energy Energy can be neither created nor destroyed.It can change form or be exchanged between objects.The total energy content of the universewas determined in the Big Bang and remains the same today.You might wish to go through the example tracing the energy of a baseball back through time, as described on p. 90 of the text.
31 Conservation of Momentum The total momentum of interacting objectscannot changeunless an external force is acting on them.Interacting objects exchange momentumthrough equal and opposite forces.You may wish to discuss the examples given in the text on p. 79.
32 What keeps a planet rotating and orbiting the Sun? You may wish to go over this figure in some detail to be sure the idea is clear.
33 Conservation of Angular Momentum angular momentum = mass velocity radiusThe angular momentum of an objectcannot change unless anexternal twisting force (torque)is acting on it.Earth experiencesno twisting force as it orbits the Sun,so its rotation and orbitwill continue indefinitely.You may wish to discuss the examples given in the text on p. 79.
34 Angular momentum conservation also explains why objects rotate faster as they shrink in radius.Discuss astronomical analogs: disks of galaxies, disks in which planets form, accretion disks…
35 What is Gravity? Gravity is a force of attraction that exists between any two masses,any two bodies,any two particles.
36 Gravity is not just the attraction between objects and the Earth. It is an attraction that exists between all objects,everywhere in the universe.
37 Sir Isaac Newton ( ) discovered that a force is required to change the speed or direction of movement of an object.He also realized that the force called "gravity“must make an apple fall from a tree,or humans and animals live on the surface of our spinning planet without being flung off.Furthermore, he deduced that gravity forces exist between all objects.
39 Important things we have learned. Objects in the universe have mass.The motion of body is described by Newton's three laws.A force is required to cause motion or a change in motion.Energy is what causes the force.All mass (matter) is attracted to other matter.This force of attraction is called GRAVITY.GRAVITY exists between all mass (matter) in the universe.
40 Therefore If we can observe and understand it on earth understand it in space.