2. Bit of Administration …. Lab 2Lab 2 –New observation dates: March 22 - April 5 No need to duplicate observations in hand!No need to duplicate observations in hand! –New due date: April 9 at my office HomeworkHomework Reading Reading –BSNV pp. 153 - 168 No office hours todayNo office hours today –Feel free to e-mail for later in week

3. Astronautics Interplanetary Travel Interplanetary Travel The Central Concept … The Central Concept … The paths of interplanetary spacecraft are The paths of interplanetary spacecraft are simply orbits around the Sun … simply orbits around the Sun … And the spacecraft obey the same physical laws as do planets. as do planets.

4. Astronautics Transfer Orbit = Minimum Launch Energy Transfer Orbit = Minimum Launch Energy Launch in the direction of motion of the launch platform. Launch in the direction of motion of the launch platform. Arrive at destination at aphelion ( for outer target) or Arrive at destination at aphelion ( for outer target) or perihelion (for inner target) of spacecraft orbit. perihelion (for inner target) of spacecraft orbit. (Aphelion - point of orbit most distant from Sun (Aphelion - point of orbit most distant from Sun Perihelion - point of orbit closest to Sun) Perihelion - point of orbit closest to Sun)

5. Transfer Orbit for the Moon

6. Astronautics Transfer Orbit = Minimum Launch Energy Transfer Orbit = Minimum Launch Energy Launch in the direction of motion of the launch platform. Launch in the direction of motion of the launch platform. Arrive at destination at aphelion ( for outer target) or Arrive at destination at aphelion ( for outer target) or perihelion (for inner target) of spacecraft orbit. perihelion (for inner target) of spacecraft orbit. (Aphelion - point of orbit most distant from Sun (Aphelion - point of orbit most distant from Sun Perihelion - point of orbit closest to Sun) Perihelion - point of orbit closest to Sun) Advantages - Fuel efficiencyAdvantages - Fuel efficiency Disadvantages - Long travel timeDisadvantages - Long travel time

7. Astronautics Gravity Boosts Gravity Boosts Gain in energy due to gravitational “slingshot” around Gain in energy due to gravitational “slingshot” around a more massive body. a more massive body. Note: More massive body loses energy, but in case of Note: More massive body loses energy, but in case of planet and spacecraft this is not a problem! planet and spacecraft this is not a problem!

8. Astronautics Gravity Boosts Gravity Boosts In frame of Jupiter In frame of Solar System but Jupiter is moving …

9. Astronautics Gravity Boosts - NASA missions Gravity Boosts - NASA missions

11. The Physics of Light Light as a Wave = Electromagnetic Radiation Light as a Wave = Electromagnetic Radiation Wavelength ( ) has units of length Wavelength ( ) has units of length Frequency ( ) - number of crests passing per second Frequency ( ) - number of crests passing per second - has units of cycles per second, or Hertz - has units of cycles per second, or Hertz Speed - for light, c = 3x10 5 km/sec Speed - for light, c = 3x10 5 km/sec Wavelength 3 x 10 5 km/sec

12. The Physics of Light Light as a Wave = Electromagnetic Radiation Light as a Wave = Electromagnetic Radiation Wavelength ( ) has units of length Wavelength ( ) has units of length Frequency ( ) - number of crests per second Frequency ( ) - number of crests per second Speed - for light, c = 3x10 5 km/sec Speed - for light, c = 3x10 5 km/sec Large wavelength Small frequency Small wavelength Large frequency

13. The Physics of Light Light as a Wave = Electromagnetic Radiation Light as a Wave = Electromagnetic Radiation Wavelength ( ) has units of length Wavelength ( ) has units of length Frequency ( ) - number of crests passing per second Frequency ( ) - number of crests passing per second - has units of cycles per second, or Hertz - has units of cycles per second, or Hertz Speed - for light, c = 3x10 5 km/sec Speed - for light, c = 3x10 5 km/sec

14. The Physics of Light Electromagnetic Electromagnetic Spectrum Spectrum 1 km = 1000 m 1 m 1 mm = 0.001 m = 10 -3 m 1  m = 10 -6 m (“micron”) 1 nm = 10 -9 m (nanometer)

15. The Physics of Light Electromagnetic Radiation Electromagnetic Radiation Light acts as an electric force Light acts as an electric force Light acts as a magnetic force Light acts as a magnetic force - - - - - - - - - - - - - - S N N S S N S N N S N S S N S N S N N S N S N S

16. The Physics of Light Electromagnetic Radiation Electromagnetic Radiation - - - - - - - - -Antenna

17. The Physics of Light Doppler Shift Doppler Shift

18. The Physics of Light Doppler Shift Doppler Shift Source moving toward observer or Source moving toward observer or observer moving toward light source observer moving toward light source Shorter Wavelength Shorter Wavelength Higher Frequency Higher Frequency Blueshift Blueshift Light source moving away from observer or Light source moving away from observer or observer moving away from light source observer moving away from light source Longer Wavelength Longer Wavelength Lower Frequency Lower Frequency Redshift Redshift

19. The Physics of Light Doppler Shift Doppler Shift Source across observer’s line of sight Source across observer’s line of sight Same Wavelength as emitted Same Wavelength as emitted Same Frequency as emitted Same Frequency as emitted No Shift No Shift

20. The Physics of Light Doppler Shift Doppler Shift v = velocity of light source or observer (+ => toward each other) = rest wavelength = rest wavelength  = change (shift) in wavelength c = 3 x 10 5 km/sec