Ancient thought, even among the rabbis of the Talmud, was that the Zodiac controlled certain Earthly events. In Hebrew, the signs of the Zodiac are מזלות, now known as "luck".
For example, in Shabbat 129b:
בתלתא בשבתא מאי טעמא לא? משום דקיימא ליה מאדים בזווי
Basically, don't let blood on Tuesday because Mars is in power then.
In modern Jewish thought, does the Zodiac control/influence anything? Or is it merely superstition?
Rambam repudiates astrology, writing that only fools believe in astrology (Hil. Avoda Zara 11:17-8):
יז ודברים האלו--כולן, דברי שקר וכזב הן; והן שהטעו בהן עובדי עבודה זרה הקדמונים לגויי הארצות, כדי שיינהו אחריהן. ואין ראוי לישראל, שהן חכמים מחוכמים, להימשך בהבלים אלו, ולא להעלות על הלב שיש בהן תעלה: שנאמר "כי לא נחש ביעקוב, ולא קסם בישראל" (במדבר כג,כג), ונאמר "כי הגויים האלה, אשר אתה יורש אותם--אל מעוננים ואל קוסמים, ישמעו; ואתה--לא כן, נתן לך ה' אלוהיך" (דברים יח,יד).
יח כל המאמין בדברים אלו, וכיוצא בהן, ומחשב בליבו שהן אמת ודברי חכמה, אבל התורה אסרה אותן--אינו אלא מן הסכלים ומחסרי הדעת, ובכלל הנשים והקטנים שאין דעתן שלמה. אבל בעלי החכמה ותמימי הדעת, יידעו בראיות ברורות--שכל אלו הדברים שאסרה תורה, אינן דברי חכמה, אלא תוהו והבל שנמשכו בהן חסרי הדעת, ונטשו כל דרכי האמת בגללן. ומפני זה אמרה תורה, כשהזהירה על כל אלו ההבלים, "תמים תהיה, עם ה' אלוהיך" (דברים יח,יג).
These practices are all false and deceptive and were means employed by the ancient idolaters to deceive the peoples of various countries and induce them to become their followers. It is not proper for Israelites who are highly intelligent to be drawn by such inanities or imagine that there is any benefit in them, as it is said "For there is no enchantment with Jacob, neither is there any divination with Israel" (Numbers 23:23; and further "For these nations that you are to dispossess hearken to the soothsayers and diviners; but as for you "The Lord your God has not suffered you so to do" (Deut. 18:14).
Whoever believes in these and similar things and, in his heart holds them to be true and scientific and only forbidden by the Torah, is nothing but a fool, deficient in understanding, who belongs to the same class with women and children whose intellects are immature. Sensible people, however who possess sound mental faculties know by clear proofs that all these practices which the Torah prohibited have no scientific basis but are chimerical and inane; and that only those deficient in knowledge are attracted by those follies and, for their sake, leave the ways of the truth. The Torah, therefore, in forbidding all these follies, exhorts us, "You shall be wholehearted with the Lord your God (Ibid 18:13)" (Trans. based on R. Dr. Twersky; A Maimonides Reader 75-6).
The list of forbidden activities he is repudiating at the end of the chapter, includes astrological predictions, as in halakha 9)
Elsewhere he also references "the stupid astrologers" (Hil Teshuva 5:4):
כמו שבודים מליבם הטיפשים הוברי שמיים
Rambam wrote a letter on astrology cited and translated here (original Hebrew text here in which he writes:
Know, my masters, that every one of those things concerning judicial astrology that (its adherents) maintain—namely, that something will happen one way and not another, and that the constellation under which one is born will draw him on so that he will be of such and such a kind and so that something will happen to him one way and not another—all those assertions are far from being scientific; they are stupidity.
Nevertheless he believes that the constellations are more than just stupid rocks. (Cf. Hilchos Yesodei Hatorah 3:9). They are channels for divine intervention in the world.
Just as we maintain that the Holy One, blessed be He, performs signs and wonders through the angels, so do these philosophers maintain that all these occurrences in the nature of the world come through the spheres and the stars. They maintain that the spheres and the stars possess souls and knowledge. All these things are true. I myself have already made it clear, with proofs, that all these things involve no damage to religion. And not only this, but what is more I have understood from the sayings of the sages in all of the Midrashim that they maintain as the philosophers maintained. There is no controversy whatever between the sages of Israel and the philosophers on these matters.
Rambam's main point is that ultimately the goings on in the world are exactly in line with God's will in response to our good or bad behavior, and no other entity calls the shots. (This seems pretty similar to Ramban's statement in the end of his commentary to parshas Bo that our goal is to realize that ultimately God pulls the strings on everything in life).
The controversy lies in this, that the true religionists, and that is the religion of Moses our Teacher, maintain that what happens to individuals is not due to chance, but rather to judgment... This is a root of the religion of Moses our Teacher, that everything happening to human beings is a (just) decree and judgment. Hence, the sages maintained: "There is no death without sin and no affliction with transgression" (Shabbat 55a).
He further emphasizes that man has absolute free will.
Every action of human beings is left to them and that there is nothing to constrain or draw them. Rather, if he so pleases, a man will worship God and become wise and sit in the house of study. And if he so pleases, he will follow the counsel of the wicked and run with thieves and hide with adulterers. There is no influence or constellation under which one is born that will draw him in any manner toward any one of these ways. Hence it was commanded and told to him: "Do this and do not do that."
In regard to the position of the Rabbis he writes:
I know that you may search and find sayings of some individual sages in the Talmud and Midrashim whose words appear to maintain that at the moment of a man's birth, the stars will cause such and such to happen to him. Do not regard this as a difficulty, for it is not fitting for a man to abandon the prevailing law and raise once again the counterarguments and replies (that preceded its enactment). Similarly it is not proper to abandon matters of reason that have already been verified by proofs, shake loose of them, and depend on the words of a single one of the sages from whom possibly the matter was hidden. Or there may be an allusion in those words...
Note that Rambam doesn't quote the astrological advice about Mars from the Gemara in Shabbat, even though the Gemara expresses no doubt about it.
Elsewhere he emphasizes how unreliable astrologers are (Yesodei Hatorah 10:3).
He further writes in his Iggeret Teiman (quoted here).
I note that you are inclined to believe in astrology and the influence of the past and future conjunctions of the planets upon human affairs. Dismiss such notions from your mind. Cleanse your mind of them as one cleanses dirty clothes. Accomplished gentile and certainly Jewish scholars refuse to believe in the truth of this science. Its postulates can be refuted by real proofs on rational grounds, but this is not the place to enter into a discussion of them. (Halkin translation, p. 116)
R. Qafih concludes that according to Rav Saadya Gaon (cf. commentary to Iyov ch. 39 pp. 194-5 and commentary to Exodus 21:13), the Hovot HaLevavot (Shaar Yihud HaMaaseh ch. 5 in ed. R. Qafih), Rabbi Yehuda HaLevi (cf. Kuzari 1:1, 4:23), and Rambam (see above and Shemonah Ferakim ch. 8, and Moreh Novokhim 3:29), astrology is meaningless and forbidden. (Ketavim Vol. I p. 93). R. Qafih's own approach is to follow Rav Saadya Gaon, Hovot HaLevavot, Rambam, and the rest of that school. In this vein, he discourages use of the expression 'mazal tov', as it is astrological, as does his student R. Ratson Arussi.
Without a particular source (yet) I imagine that later thinkers would not agree to the point that the celestial bodies have intelligence. This may well have been a medieval belief that was reverse engineered into Jewish sources. They would presumably agree to his core points that man has free will to do good or bad, and that God will is expressed fully in the world through whatever media he desires.
Rashi on the Gemara that says אין מזל לישראל (Shabbos 156a), says:
אין מזל לישראל - דעל ידי תפלה וזכות משתנה מזלו לטוב
There is a modern Jewish hashkafa that the Zodiac can have an effect on our lives, but we have the ability to "get out of it". אין מזל לישראל means that Jews can be beyond their mazal, and are not bound to it.
The Shulchan Aruch in Yoreh Deah 179 siff 1 says we may not ask astrologers or use lotteries (to figure out the future). The Ramma quoting the Beis Yosef explains the reason is the Torah says תמים תהיה עם ה׳ אלהיך.
In the next siff, the Ramma informs us from tshuvos Rashba (hamiyuchos liRamban) that if someone is somehow aware that a certain act is against his mazal, he should not carry through and rely on a miracle, we just don't seek out this information because of תמים תהיה.
This Ramma is brought as recently as the Chachmas Adam Klal 89 siff 5.
The Shach there #1 points to the Ramma who said witchcraft is a bigger issur than astrology, and therefore we are more stringent and would only allow such practices for sick people going to witches and people involved in divination for a cure. Maharai allows it for all sicknesses while Maharshal only allowed it for a life threatening one.
This Shach is brought as recently as the Kitzur Shulchan Aruch in siman 166 siff 5.
The Shach in this siman also points to the Ramma in Orach Chaim 664 about divining in the moonlight on the night of Hoshana Rabba, there he merely suggests against it so as not to ruin one's Mazal, and because people don't really know what they're doing, and because of תמים.
Unfortunately, none of the common poskim have anything written on that Ramma and whether or not these things still work. Shulchan Aruch HaRav is missing there. Aruch HaShulchan And Mishna Berurah don't discuss it. Only one that comes close is Kaf HaChaim who has a long quote how exactly to do it. (Stripping bare from linen clothing in the open field. Yeah.)
But anyways, its nice to be philosophical and scientific and say this stuff is a long forgotten hoax, but halachicaly we must take it into consideration.
So until we have a quote from someone more recent who's opinion outweighs all of these, we must still take it into consideration that it is real.
A possible contender is the Torah Temimah in Parshas Shoftim chapter 18 #64 quoting a Mahari Chagiz in Eitz Chaim, who says "after the light of Hashem has already spread to the world and people believe there is no other power besides Him, these impure powers no longer work and only fools believe in them."
Those words were originally written in the seventeenth century or so. Post Ramma and Shach, but before Chachmas Adam and the Kitzur.
One possible data point regarding this topic is the issue of kiddush on Shabbat night "during the seventh hour".
There is a position that making kiddush immediately after nightfall (the seventh hour) should be avoided, because that is the hour of the dominant astrological influence of Mars. Instead, one would either make kiddush while it is still daylight (if one accepted Shabbat early) or else delay kiddush until after the planetary hour of Mars has passed.
This position is brought by the Magen Avraham on Shulhan Arukh, אורח חיים, siman רעא:
וכתוב בתקוני שבת שיקדש קודם לילה כי בתחלת ליל שבת הוא מזל מאדים ובסוף יום ו' הוא מזל צדק לכן יקדש בצדק וכ"כ בתשובות מהרי"ל סי' קס"ג
It says in Tikkunei Shabbat that one should make kiddush before nightfall because at the beginning of the night of Shabbat there is the astrological influence of Mars, while at the end of the day of Friday there is the astrological influence of Jupiter, therefore one should make kiddush in Jupiter. And so it is written in the responsa of the Maharil.
Mention of this position is then included in the code of law of the Ba'al Ha-Tanya, Shulkhan Arukh Ha-Rav, in אורח חיים חלק - הלכות שבת - רעא:
יש נזהרים שלא לקדש בשעה ראשונה של הלילה (דהיינו שעה שביעית אחר חצות היום עיין סי' תכ"ח) אלא או קודם הלילה או לאחר שעה תוך הלילה לפי שבשעה הראשונה הוא מזל מאדים וסמא"ל מושל עליו
There are those who are careful not to make kiddush during the first hour of the night, instead making kiddush either before nightfall or after one hour of night has passed. This is because in the first hour of the night there is the astrological influence of Mars and the samekh-mem rules over it.
Shulhan Arukh Ha-Rav is a primary halachic authority in the contemporary world, especially for Hasidim, and this position is taken into account by those communities.
This is not primarily a question of Jewish belief or practice. It is essentially a scientific question. And, because halakha expects man to be in touch with reality, I believe that a Jew may not believe in astrology.
We have known for several centuries that the stars and planets have no influence over human affairs. Pre-modern halakhic sources on this subject are interesting but mostly irrelevant to contemporary Jewish life.
See my article where I discuss this topic at some length: http://realiajudaica.blogspot.com/2012/05/may-jew-believe-in-astrology.html
Astrology is listed as part of prohibition #335 in the list of mitzvot here:
Not to practice onein (observing times or seasons as favorable or unfavorable, using astrology) (Lev. 19:26) (CCN166).
However, some sources including the Ein Yaakov disagree that astrology falls under the prohibition of me'onein; see here.
I think, we should not confuse the question of whether the stars have influence with How religious Jews should treat astrology. I also assume the question is not about the physical reality and scientific validity of astrology, but our Sages' outlook.
I would formulate my answer a bit differently:
In general, serious knowledge of astrology allows making very realistic and true predictions.
The most straightforward evidence is that all of the examples of astrological predictions in the Torah and the Gemorah turned out to be true! (most of them by gentiles, though).
For example,
Torah: Egyptian astrologists predicting Eshet Putifar/his daighter marriage to Yossef, predicting Moses, his birth, his rise and his "fall", predicting Israel not entering the promised land etc.
Gemmorah: all aforementioned cases of "אין מזל לישראל", charity altering own fate (as in R' Akiva's daughter wedding, ibid) turned out to be true.
I could not recall a single case where the gentile astrologists interpreted the situation in one way, but the reality was totally different and non-related, so the Sages could declare astrology folly or nonsense.
If so, how can I explain the numerous rulings @mevaqesh cited against my conclusion? The answer is simple - the Poskim (see Rambam in Moyreh Nevochim) target the question of Jews practicing astrology, not the question of validity of ancient predictions. So, as a ordinance, they forbid it.
Moreover, based on Rambam's beggining of Ilchot Avodah Zarah, it is clear to me, that all forms of idolatry originally had true powers, as being Hashem's servants, however, people were satisfied with their powers and turned from Hashem. I did not see where Rambam or others claim soundly that idolatry is vacuous, pointless and useless.
NB. I personally practiced natal astrology some 25 years ago, when studying BA in Psychology , and I was very surprised of the results. This is consistent with R' Chanina's "הכל בידי שמים חוץ מיראת שמים" (Berochos 33b), personality traits, physical forms and health, overall life conduct is pre-destined.
;-)