Mercury’s year
Seen from the Earth, Mercury loops back on itself three times a year, and each loop is a time it passes between the Earth and the Sun. This is its path a year either side of today, worked out day by day.
Where Mercury is now
Furthest from the Sun
Mercury never strays more than about twenty-eight degrees from the Sun, so it is only ever seen low in the twilight, and best near its greatest elongations. For northern observers it shows best at evening elongations in spring and morning elongations in autumn, when its path stands steeply above the horizon at dusk or dawn; in the southern hemisphere it is the reverse.
Retrograde
Each time Mercury overtakes the Earth it seems to stop, run backwards for about three weeks and go on again. The dates are the stations, and the degrees are where Mercury stood when it turned.
Meetings with the Sun
Three passes between the Earth and the Sun take a little less than a year, so each one falls short of the one a year before, and the triangle they make turns slowly backwards through the signs.
Why three loops a year
Mercury goes round the Sun in eighty-eight days, faster than any other planet, and catches up with the Earth on average every hundred and sixteen days. Each time it does, it passes between the Earth and the Sun and seems from here to stop, go backwards and come on again, which is the small loop in the path. A hundred and sixteen days fit into a year a little over three times, so there are three loops a year and the whole pattern creeps round. Because its orbit is the most eccentric of the planets, the loops and the greatest elongations are not all the same size: an elongation can be anything from about eighteen to about twenty-eight degrees.
One loop, step by step
Every loop runs in the same order. Mercury comes out from behind the Sun into the evening sky and moves away from it until it reaches its greatest elongation east. A week or two later it slows and turns retrograde, drops back towards the Sun and passes between us and it at the inferior conjunction, about halfway through the three weeks it runs backwards. It then comes out on the other side, turns direct, and reaches its greatest elongation west in the morning sky before heading round the far side of the Sun again. So a retrograde always begins with Mercury as an evening object and ends with it as a morning one, and the best evening and morning views sit just outside the retrograde, not inside it. Through a telescope Mercury shows phases like the Moon’s as it goes: a small nearly full disc on the far side of the Sun, a larger thin crescent as it comes near.
How the loops move through the signs
In the hundred and sixteen days between one loop and the next the Sun, and Mercury with it, moves on about 114 degrees. That is just short of 120, a third of the zodiac, so three loops in a row fall in three signs of the same element, each a few degrees earlier in its sign than the one before. After a couple of years the loops slip back into the neighbouring signs, and the element changes. Astrologers who follow the retrogrades often note which element they are in for that reason. The pattern comes close to repeating after seven years, closer after thirteen, and closer still after forty-six, when 145 loops fit into the years almost to the day. Day-by-day visibility for all five planets is on the Visibility page, the retrograde dates of every planet on Backwards, and what Mercury stands for in a chart on Mercury.
How it is worked out
The path is Mercury’s position seen from the centre of the Earth, twice a day, flat on the ecliptic of the date, in the same frame as every wheel on the site. The meetings with the Sun and the greatest elongations come from searches in the same astronomy that gives the rest of the site its positions, and the retrograde stretches from where Mercury’s motion along the zodiac changes direction, exactly as on the retrograde page. Times agree with published tables to within a minute or two. How well Mercury can actually be seen also depends on the horizon, the weather and the latitude, which the page does not know.
What astrology makes of it
Mercury retrograde is one of the best-known phrases in astrology, and the tradition treats it as a time for going back over things rather than starting them. No measured effect on contracts, travel or electronics has ever been found. The page gives the dates and degrees, describes how they are read, and predicts nothing.
Questions people ask
Why does Mercury seem to loop backwards?
Mercury completes an orbit in eighty-eight days while the Earth takes a year, so Mercury keeps catching us up on the inside track. Each time it overtakes us it lines up between us and the Sun, and from our moving viewpoint it appears to slow, stop, run back along the zodiac for about three weeks and then carry on. That happens about every hundred and sixteen days, a little over three times a year, which is why the path on this page draws three loops a year and the pattern slowly turns.
When is the best time to see Mercury?
Near a greatest elongation, when Mercury stands furthest from the Sun, and even then only low in the twilight: in the west soon after sunset for an evening elongation, in the east before sunrise for a morning one. Some are far better placed than others, and the list of elongations on this page notes which suit northern observers and which southern. The line headed Seen says where Mercury is right now, or that it is too close to the Sun. A clear, low horizon helps more than anything else.
What is an inferior conjunction of Mercury?
It is the moment Mercury lies directly between us and the Sun, near the middle of a retrograde loop. Mercury is then close to its nearest to the Earth but lost in the Sun’s glare, and about thirteen times a century it crosses the face of the Sun as a small dark dot, which is a transit. When Mercury passes on the far side of the Sun instead, that is a superior conjunction. On this page filled dots mark the inferior conjunctions and open dots the superior ones.
How is Mercury retrograde read in astrology?
Astrology links Mercury with speech, writing, study, travel and trade, and a retrograde Mercury is traditionally read as turning those themes back on themselves: a stretch for revising, re-reading and returning to unfinished things rather than beginning new ones. It is a frame for reflection, not a forecast, and nothing measurable changes on the Earth while it lasts. The list headed Retrograde gives each stretch within a year either side of today, with the dates Mercury turns and the degree where it stood.