The Seasons and Other Tidbits of Information

1. The Seasons and Other Tidbits of Information Mrs Naylor Honors Earth Science Fall 2013

2. Here’s what we do understand! • The Earth orbits the Sun in an ellipitical orbit. • Perihelion is the point of the orbit at which the Earth is closest to the Sun. • Aphelion is the point of the point at which the Earth is the farthest distance from the Sun.

3. The Earth is tilted on its axis. • This tilt means that the radiation from the Sun does not hit the Earth equally.

4. Mrs Naylor has some misconceptions…. • Look at the diagram below and determine what Mrs Naylor’s misconceptions are. Then formulate a reason as to why you think she may have these misconceptions.

5. The CORRECT Information The Earth is actually closer to the Sun at the winter solsitice than it is at the summer solstice.

6. So.. Here’s what we really need to understand • Because of the tilt of the Earth’s axis, more of the Sun’s radiation hits the northern hemisphere at the summer solsitice. The Earth just happens to be at the aphelion of its orbit.

7. The seasons are influenced more by the tilt of the axis than by the location in the Earth’s orbit.

8. Determine the seasons

9. Other little tidbits

10. Why isthe moon attracted to the Earth? • Have you ever really thought about this? • This is due to Gravitational Attraction

11. Did you catch all that?!??! • Basically what you need to understand is this: • Gravitational attraction between two object is determined by two things: • The mass of the two objects • The distance between the two objects

12. The Expanding Nature of our Universe

13. The stars are moving! How do we know? • The Doppler effect is the change in wave energy, such as sound or light, as that energy moves toward or away from an observer. • Ex. As the train approaches, the sound waves ahead of it are compressed. These shorter waves have a high frequency, so the horn sounds high. Behind the train, the sound waves are stretched out. These longer waves have a lower frequency, so the horn sounds lower.

14. Measuring the Stars Stars in motion: The Doppler Effect in astronomy… (longer wavelength) ROY G BIV (shorter wavelength) • When the star moves closer or further from you, wavelengths of visible light (colors) from the star are “shifted” or moved due to the Doppler effect. • If a star is moving toward you,the visible light from the star is shifted toward shorter wavelengths, or blueshifted(BLUE is on the RIGHT) just like the sound waves from the train coming toward you getting higher in pitch. • If the star is moving away, the wavelengths become longer, or redshifted(remember, RED is on the LEFT) just like the sound waves from the train moving away from you getting lower in pitch. The higher the speed, the larger the shift, and thus spectral line wavelengths can be used to determine the speed of a star’s motion.

15. Doppler Effect as a Speedometer

16. This animation shows why these changes occur. As the source moves toward the right, it "catches up" with the waves it has emitted in that direction and shortens their wavelength, shifting the light to the blue. Similarly, it "leaves behind" the waves it has emitted to the left, shifting the light to the red. The Doppler Effect blueshift redshift Y O U

17. Edwin Hubble, the Doppler Effect and The “Big Bang” • In the 1930’s, Edwin Hubble observed most stars to be red-shifting. Using the Doppler Effect, he knew this meant the stars were moving away from Earth. • From this, Hubble guessed that the universe must be expanding. That means if its getting bigger in the future, it used to be smaller in the past. • Theory says all atoms in the universe were in 1 very small atom, then started moving outward.