Velocity Curve Activity Question

[hiltonml]

In the teacher notes for the velocity curve activity, part 1 it is mentioned that depending on the time of the year, the quadrant II peaks may not all be blue-shifted and the quadrant III peaks may not all be red-shifted. What time of year is this? Or does it vary from year to year?

Thank you,
Mike Hilton

[jmakous]

The orbital motion of the earth around the sun causes a change in the relative motion of different parts of the galaxy relative to earth. So a part of the galaxy for which the shift is only slightly red-shifted or slightly blue-shifted, relative to the sun, can become blue- or red-shifted, respectively, at different times of the year. The earth’s speed around the sun is approximately 29 km/s, and the earth’s orbital motion results in a sinusoidal velocity shift relative to the sun. So, for instance, a part of the MWG that is always slightly red-shifted relative to the sun will be more red-shifted at certain times of the year, and then become blue-shifted at other times of the year.

The lesson titled ”Measuring the Earth's Speed around the Sun” under the DSPIRA-Lessons Portal has a good activity to do with the students. There is a nice sinusoidal graph under the teacher notes showing the relative motion of the earth.

[hiltonml]

Thank you very much for your reply. This data explains the discrepancy between my class' doppler shift measurements and the "theoretical" results we expected. Mike Hilton, Ph.D. <https://www.eckerd.edu/computer-science/faculty/hilton/> Assistant Professor of Computer Science 727.864.8272 Pronouns: he/him/his Eckerd College <http://www.eckerd.edu> 4200 54th Avenue South St. Petersburg, Florida 33711 [image: Eckerd College logo] *Instructions for living a life:Pay attention.Be astonished.Tell about it.* *-- *Mary Oliver, *Sometimes*

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On Thu, Jan 20, 2022 at 5:31 PM jmakous ***@***.***> wrote: The orbital motion of the earth around the sun causes a change in the relative motion of different parts of the galaxy relative to earth. So a part of the galaxy for which the shift is only slightly red-shifted or slightly blue-shifted, relative to the sun, can become blue- or red-shifted, respectively, at different times of the year. The earth’s speed around the sun is approximately 29 km/s, and the earth’s orbital motion results in a sinusoidal velocity shift relative to the sun. So, for instance, a part of the MWG that is always slightly red-shifted relative to the sun will be more red-shifted at certain times of the year, and then become blue-shifted at other times of the year. The lesson titled ”Measuring the Earth's Speed around the Sun” <https://wvurail.org/dspira-lessons/EarthAroundSun> under the DSPIRA-Lessons Portal has a good activity to do with the students. There is a nice sinusoidal graph under the teacher notes showing the relative motion of the earth. — Reply to this email directly, view it on GitHub <https://github.com/WVURAIL/dspira-lessons/discussions/10#discussioncomment-2010451>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/APSF5N2HLCEJFE6S3QIBXTTUXCEMNANCNFSM5MDIZVFA> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you authored the thread.Message ID: ***@***.***>