Revolution & Insolation

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SWBAT identify the seasons of the Earth, and where Earth’s vertical ray falls at different points in Earth’s orbit (equinox/solstice) | SWBAT identify the length of daylight of different points of the Earth at different latitudes

Big Idea

This lesson has student's explore where the Sun hits the zenith at different latitudes during different points of the year and how daylight changes at those different latitudes throughout the year

Lesson Introduction

[Note: For embedded comments, checks for understanding (CFUs), and key additional information on transitions and key parts of the lesson not necessarily included in the below narrative, please go to the comments in the following document: 4.2 - Revolution & Insolation (Whole Lesson w/comments). Additionally, if you would like all of the resources together in a PDF document, that can be accessed as a complete resource here: 4.2 - Revolution & Insolation (Whole Lesson)[PDF]. Finally, students may need their Earth Science Reference Tables [ESRT] for parts of the lesson (a document used widely in the New York State Earth Science Regents course) as well.]

This is a continuation of the content from the first day of the unit, in that is is a continued exploration of the Sun during the Equinoxes/Solstices. However, this extends that content further through analysis of where the Sun's "vertical ray" (when the Sun is at a 90 degree angle with the ground) strikes at different points throughout the year. 

Do Now & Objective

10 minutes

Students come in silently and complete the (attached) Do Now. In this case, the Do Now is a review of material from Unit 3 (Geologic History), in preparation for the upcoming interim assessment. After time expires (anywhere from 2-4 minutes depending on the type of Do Now and number of questions), we collectively go over the responses (usually involving a series of cold calls and/or volunteers), before I call on a student and ask them to read the objective out loud to start the lesson.

As a general note, the Do Now serves a few purposes:

  1. It serves as a general review of the previous day's material; (again, this is a bit different, as they are reviewing for the quarterly Interim Assessment)
  2. It is a re-activation of student knowledge to get them back into "student mode" and get them thinking about science after transitioning from another content area or alternate class;
  3. as a strategy for reviewing material students have struggled with (for example, using this as a focused review for material that they have struggled with on unit assessments or recent quizzes); and,
  4. It is an efficient and established routine for entering the classroom that is repeated each day with fidelity (I never let students enter the classroom talking. While it may seem potentially severe to have students enter silently each day, this is both a school wide expectation and a key component of my classroom. In many respects, I find that students readily enjoy the focus that starting with a quiet classrooms brings each day).

Solstices & Equinox

20 minutes

Post Do-Now, we launch into the Solstices & Equinoxes component of the lesson with a continued exploration of much of what was covered in the first day of the unit. On the first page of the resource, students learn that the vertical ray is when sunlight strikes the Earth at an angle of 90 degrees. This happens at particular latitudes on the solstices and equinoxes throughout the year, although (as mentioned in the resource), it always falls between the tropics (as in the Tropic of Cancer, at 23.5 degrees North, and the Tropic of Capricorn, at 23.5 degrees South). Using the image, we then answer the two questions related to the image on the first page - the vertical ray hits at the Equator, and (this is a trick question!) the hemispheres receive equal sunlight on the Equinoxes. 

We then (as a class) take a very similar approach with the illustrations featuring both the summer and winter Solstices. On page three (3) of the Solstices & Equinoxes resource, on the Summer Solstice, students see that the vertical ray falls on the Tropic of Cancer (23.5 degrees N), and that the Earth's Northern Hemisphere is tilted toward the Sun. The opposite is true in the Winter Solstice, as the vertical ray falls on the Tropic of Capricorn (23.5 degrees S), and the Southern Hemisphere is tilted toward the Sun. That also indicates that the seasons are always opposite in the Northern and Southern hemispheres. To help explain how the daylight changes at different latitudes as a result of the seasonal changes, I show them a brief clip of the 'Arctic Midnight Sun' during the Northern Hemisphere summer, when the Sun does not set below the horizon at latitudes above the Arctic Circle. 


Finally, on the last page of the Solstices & Equinoxes resource, students partner up and complete information pertaining to recognizing seasonal changes in a diagram of Earth's annual revolution around the Sun.

[Note: The embedded comments found in the Word document in the Lesson Introduction are particularly helpful in this section]


25 minutes

The Practice section in this lesson is fairly similar to most other traditional practice sessions in my classroom, although I should mention that I found students struggled a bit more with some of the more advanced questions here (I don't really know if there's anything I would do differently next time - I think struggling is okay a lot of the time! See the reflection in this section for more thoughts on this). But I would definitely allow adequate time to review some of the more contextually difficult questions in this section. For example, #5-6 and #8-9 I remember being somewhat challenging for students, as they have to carefully think about what the question is asking them, apply knowledge from earlier in the lesson to a novel scenario or image they haven't seen before, and have everything sufficiently top of mind to be able to do that reasonably quickly. 

In terms of student work habits, I tend to sometimes make this decision in the moment, and as a response of what I know about the students and how they're processing the material on, but I'll either ask them to work independently, in partners, or give them the option. Usually, before starting practice, we tend to go over some steps for self-help ("What should you do if you're stuck?"), and I might reference a previously used multiple-choice or free response strategy in order to build their skills while simultaneously learning content (as an example - one popular one we always use - "If you aren't sure what the right answer is, see if you can eliminate some wrong answer choices"). I tend to circulate for compliance and then hone in on specific students while they're doing this. 

After about 10 minutes, we go over their responses. Students who finish early are encouraged to work on the exit ticket (resource below) and double-check their responses. We use a combination of strategies (active voting, cold calling, popsicle sticks, volunteers) to go over the responses, where students correct their work and ask any clarifying questions. 

Exit Ticket & Closing

5 minutes

In the last few minutes of class, I have students complete the daily Exit Ticket. For the sake of time, I have students grade them communally, with a key emphasis on particular questions and items that hit on the key ideas of the lesson (Note: This usually manifests as students self-grading, or having students do a "trade and grade" with their table partners). After students grade their exit tickets, they usually pass them in (so that I can analyze them) and track their exit ticket scores on a unit Exit Ticket Tracker. 

After students take a few seconds to track their scores, we usually wrap up in a similar way. I give students time to pack up their belongings, and I end the class at the objective, which is posted on the whiteboard, and ask students two questions:

  1. Do you feel that you mastered the objective for the day?
  2. Can you reiterate one thing you learned about (in this case, information on where the vertical ray falls on the respective Equinoxes/Solstices, etc.)?

Once I take 2-3 individual responses (sometimes I'll ask for a binary "thumbs up/thumbs down" or something similar), I have students leave once the bell rings.