# SETI's First Contact

**URL:** <https://boards.straightdope.com/t/setis-first-contact/229813>\
**Category:** Factual Questions\
**Created:** [February 18, 2004, 4:56pm UTC](https://boards.straightdope.com/t/setis-first-contact/229813 "2004-02-18T16:56:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\
**Post date:** [February 18, 2004, 4:56pm UTC](https://boards.straightdope.com/t/setis-first-contact/229813/1 "2004-02-18T16:56:06Z")

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No, it hasn’t happened yet…unless you count the “wow” event :rolleyes: .

Suppose we encounter a radio transmission from an extra-terrestrial planet or ship. How do we compensate for the doppler shift of an object moving toward/away in respect to Earth at an uneven rate?

I mean, a planet orbits a star, and in regards to a distant stationary object, is seen to approach and then recede. This means its frequency increases and decreases.

How does SETI compensate for that?

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**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\
**Post date:** [February 18, 2004, 5:01pm UTC](https://boards.straightdope.com/t/setis-first-contact/229813/2 "2004-02-18T17:01:16Z")

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The planet orbiting a star would likely now move enough relative to the Earth during its transmission to make frequency changes significant. If it did the change would be smooth and easy to compensate for. I mean there’s only so many ways to orbit a star.

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**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\
**Post date:** [February 18, 2004, 5:11pm UTC](https://boards.straightdope.com/t/setis-first-contact/229813/3 "2004-02-18T17:11:25Z")

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now = not.