Origin and Etymology of ephemeral : Greek ephēmeros lasting a day, daily, from epi- + hēmera day https://www.merriam-webster.com/dictionary/ephemeral
Accented and unaccented vowels are pronounced the same in Greek. The accent only shows the position of the syllable with the "stronger" pronunciation.
Unaccented vowels don't get reduced to shwa as they do in English.
The vowels in χώρος "place" and χορός "dance" sound identical - only the position of the word stress moves.