Mercury retrograde is an optical phenomenon: from Earth, Mercury appears to move backward in its orbit. It does not stop, it does not change direction - it is a matter of relative perspective between two planets with different orbital speeds.
In astrology, Mercury rules communication, mental processing, contracts, technology, and short-distance travel. When it retrogrades, these themes enter a revision cycle. It is not that "everything goes wrong" - it is that what was unresolved comes to the surface. Incomplete conversations, decisions made without sufficient information, ambiguous agreements: Mercury retrograde illuminates them.
From ERA's interpretive methodology, the real impact of Mercury retrograde depends on your progressed chart, not your sun sign. If your progressed Mercury is in a mutable sign (Gemini, Virgo, Sagittarius, Pisces), you will feel these transits intensely. If it is in a fixed sign, the effect is more subtle.
The real impact of Mercury retrograde depends on your progressed chart - where your Mercury is TODAY, not where it was born.