1512: Horoscopes

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If you live in the Northern hemisphere. In the southern hemisphere, due to the coriolis effect, babies are born nine months BEFORE they're conceived.
Title text: If you live in the Northern hemisphere. In the southern hemisphere, due to the coriolis effect, babies are born nine months BEFORE they're conceived.


Horoscopes purport to predict someone's personality or future, based on the position of planets and stars at the time of their birth and at present. Horoscopes commonly group people into twelve groups based on zodiac signs. The names of the horoscope Zodiac signs are based on the names of twelve constellations that were the backdrop for the path of the sun in the ancient times when the rules of settings horoscopes were originally developed. Today, due to precession of the Earth's axis of rotation (and to a lesser degree due to the modern formal definitions of constellations), the Zodiac signs do not correspond fully to the names of actual constellations in the path of the Sun. One's zodiac sign is determined by the position of the sun on their birthday, with each sign representing a specific 30.4 day period (1/12th of a year), starting from the First point of Aries.

Modern science has found no basis for horoscopes, which is why the comic jokes about the fact that its horoscopes at least may be true. Actual horoscopes are typically so vague that they could be true for almost anyone regardless of their sign. Note that this horoscope mainly makes sense for people living in the northern hemisphere (as mentioned in the title text) and it is especially tailored for an audience in the United States, as most cultural references are centered on "Western" or even specific "American" culture, several won't even work in Europe, for example. However, with the principle understood, it is easy to apply local traditions for more accuracy in non-Western cultures.

The 12 category zodiac signs in horoscopes are based on birth dates. The average length of pregnancy, culturally considered to be nine months, is actually given as the 40 weeks (9.2 months) after the last menstrual period. However, what is relevant here is that it is only 38 weeks after conception (8.75 months). The first two weeks of the 40 week period is before Ovulation, and the conception cannot occur before that.

Based on this knowledge Randall can do some informed guessing about the context of someone's conception (apart from the obvious), depending on the sign. For example, people of the sign Virgo have been born between August 23 and September 22. This makes it most likely that they are conceived during December the year before. Given contemporary holiday music preferences, Christmas songs were likely to be playing the day they were conceived. This leads to the guess "You may have been conceived while a Christmas song played". See detailed description of all the signs and explanation of the horoscopes in the table below.

Randall phrases his "predictions" as possibilities ("you may have") rather than declarations, acknowledging that it is a guess, and that it, unlike actual horoscopes, doesn't necessarily apply to everyone.

The title text refers to the Coriolis effect which applies to a body that is moving relative to an object that is spinning. Since the Earth is rotating, a force (the Coriolis force) causes moving objects to be deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This effect is the reason that weather systems (most clearly seen for hurricanes) spiral in one direction in the northern hemisphere and in the opposite direction in the southern hemisphere.

There is also a common misconception that the Coriolis force in respect of the Earth affects objects on a much smaller scale, such as the direction water will spiral down a drain in the two hemispheres (see also 843: Misconceptions). In reality, the relative rotational speed of the Earth (one rotation per day) is insufficient to affect anything but large-scale, relatively slow movement, such as prevailing winds and ocean currents.

Randall plays on this type of misconception to make a joke involving reversing the flow of time. So whereas babies are born nine months after conception in the northern hemisphere (clockwise) the Coriolis effect is the reason why babies are being born nine months before in the southern hemisphere (counterclockwise). Note that unlike these horoscopes, which are declared to have an "actual basis in fact", it makes no sense for the conception of a baby to happen after its birth[citation needed].

Table of Astrological signs[edit]

Here below is a table with data and explanation of the individual horoscopes:

Astrological sign
(English name)
Horoscope prediction Explanation
(The Ram)
March 21 – April 21 June 28 – July 28 You may have been conceived after a 4th of July fireworks show In the US the Independence Day is celebrated on the 4th of July, and this is customarily celebrated with huge fireworks. Fireworks are a common metaphor for the culmination of sex (i.e. the orgasm), and offer a convenient opportunity for social gatherings that might lead to conception.
(The Bull)
April 20 – May 20 July 27 – August 27 You may have been conceived on a hot August day In most of the northern hemisphere there are many hot days in August. Hot days can lead to less clothing and more lust.
(The Twins)
May 21 – June 21 August 28 – September 28 You may have been conceived as the leaves began to change In the northern part of the northern hemisphere the autumn starts at the end of this time period, so the leaves will begin to change color.
(The Crab)
June 21 – July 21 September 28 – October 28 You may have been conceived by people trying on costumes This period ends a few days before Halloween, so it is not unlikely that the people who conceived you (mom and dad) tried on their new costumes when they made you. Roleplay, enhanced with costumes, can be a way to spice up a relationship and can lead to sex and procreation.
(The Lion)
July 22 – August 23 October 29 – November 30 You may have been conceived during Thanksgiving Thanksgiving is celebrated in the US on the fourth Thursday of November.
(The Maiden)
August 23 – September 22 November 30 – December 29 You may have been conceived while a Christmas song played It is very common for Christmas songs to be played in the month of December.
(The Scales)
September 22 – October 23 December 29 – January 30 You may have been conceived after a New Year's Eve party Since New Year's Eve always falls on December 31, and since the party goes on into the new year this fits with Libra. As it is very likely that people are together in a way that may lead to conception at this type of parties, there may even be rather more than a 30th part of the people that are Libra that are conceived at such a party.
(The Scorpion)
October 23 – November 22 January 30 – February 29 You may have been conceived by people stuck inside after a long winter This period is during the coolest part and towards the end of the winter in the northern hemisphere. People may even be forced to stay at home due to snow. When people have nothing else to do many babies are born 9 months later.
(The Archer)
November 22 – December 21 February 29 – March 28 You may have been conceived during March Madness Originally March madness referred to the early part of the mating season for the European Hare, in which females fight off male suitors. Today, in a US context, this is an American college Basketball tournament that started in 1939 and is mainly held in March. It is even covered on TV under the name NCAA March Madness.
(The Goat)
December 22 – January 19 March 29 – April 28 You may have been conceived during a sexy Easter Egg hunt Easter falls between March 22 and April 25 so most Easter Egg hunts, sexy or not, will fall in the most likely period to conceive Capricorn children. The goal of an Easter egg hunt can be to find as many eggs in a given time, or find a sequence of eggs, each containing a clue to the next. It is not difficult to think of adult variations on these themes. Most Egg hunts do not involve people who should make them sexy! On the other hand, the egg itself, as an Easter symbol, is a symbol of fertility and after the little ones have gone to bed the adults may want to produce more little ones.
(The Water Carrier)
January 20 – February 18 April 27 – May 25 You may have been conceived on Mother's Day Mother's Day in the USA,and some other countries, is on the second Sunday in May, between 8 and 14 May. The husband of a Mother being celebrated may wish to show his appreciation for her by paying her special private attention, potentially leading to sex and conception.
(The Fish)
February 19 – March 20 May 25 – June 27 You may have been conceived at someone's wedding It may have been your own parent's wedding, as the traditional wedding honeymoon typically includes sex (potentially lots of it). However, it is also not uncommon that people meet at weddings, and may even go so far as to risk conceiving a child at someone's wedding. June is widely reported as the most popular month for weddings in the United States. The tradition of a June Bride (late spring and beginning of summer in the northern hemisphere) may be an old one and hence explains the reference for Pisces which lies mainly in June. ABC claim that in the 15th and 16th century, May would have been the month for an "annual bath", and moreover June is named for Juno, goddess of marriage and childbirth.


[Above the frame:]
With an actual basis in fact
[A list with the name of each astrological sign in the first column (in gray) and a horoscope for each sign in the second column. Here given in table form]
Aries • You may have been conceived after a 4th of July fireworks show
Taurus • You may have been conceived on a hot August day
Gemini • You may have been conceived as the leaves began to change
Cancer • You may have been conceived by people trying on costumes
Leo • You may have been conceived during Thanksgiving
Virgo • You may have been conceived while a Christmas song played
Libra • You may have been conceived after a New Year's Eve party
Scorpio • You may have been conceived by people stuck inside after a long winter
Sagittarius • You may have been conceived during March Madness
Capricorn • You may have been conceived during a sexy Easter egg hunt
Aquarius • You may have been conceived on Mother's day
Pisces • You may have been conceived at someone's wedding

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So funny - especially the title text made me laugh :-) --Kynde (talk) 07:05, 15 April 2015 (UTC)

Nine months later, it would certainly eliminate the stress of wondering if you were gonna "get lucky" that night. - Equinox 16:13, 15 April 2015 (UTC)

The "coriolis effect" in the title text refers to the spin direction of vortices (rotating currents such as cyclones, whirlpools, and water draining from a basin), which is counter-clockwise in the northern hemisphere and clockwise in the southern hemisphere. The title text is a joke extending the reversal to the flow of time.

The spin direction of whirlpools and basins is 'not' determined by the coriolis effect, on this scale its impact is way too small to make a difference. The title text refers to how the coriolis effect is often used to explain phenomena (especially with relation to the hemispheres), even when its wrong. -- 08:23, 15 April 2015 (UTC)

If the baby is born 9 months BEFORE they're conceived, would that account for the shift in seasons for the southern hemisphere? Born in March: Northern hemisphere -> conceived in June; Southern hemisphere -> conceived in December. June and December being summer respectively. If that's right, could someone add that to the wiki? User:none

The events described during which the conception of a person with a given birth month occurred assumes that the parents were in the United States at that time. The seasons would be shifted by six months in the southern hemisphere, and the holidays of the 4th of July (Independence Day -- Aries), Halloween (Cancer, conception in October), Thanksgiving (Leo, conception in November), Mother's Day (Aquarius, conception in May), and the NCAA (college) basketball playoffs ("March Madness" -- Sagittarius) , might either not be celebrated or celebrated on a different day. The Dining Logician (talk) 08:11, 15 April 2015 (UTC)

Halloween is starting to become common in Brazil, including the "Trick or Treat" stuff. Mother's Day is also celebrated at the same date. And I wouldn't be surprised if Thanksgiving became common here too, if not only for the sales... 19:47, 17 December 2015 (UTC)

"Today, horoscopes are admitted to be pseudoscience." Citation needed. But what rubbish. Horoscopes are not even pseudoscience, so who is it "admitting" they are? 08:36, 15 April 2015 (UTC)

Agree, I would like the citation for "today", as there were experiments disproving horoscopes in ancient Rome already (involving two babies born in same time, one rich, one slave). -- Hkmaly (talk) 12:48, 15 April 2015 (UTC)

The general trick to horoscopes is make them vague enough that anyone can think they're true, regardless of their sign. --PsyMar (talk) 10:34, 15 April 2015 (UTC)

"You will have an opportunity today, meet someone new and should take care of your finances. Family matters will continue as per the last few days." 13:41, 15 April 2015 (UTC)
It's the Forer effect. 21:55, 16 April 2015 (UTC)

I propose an addition to the "conceived during someone's wedding" -- it's more common that the conception is actually after the wedding, during the (somewhat expected) consummation by the actual married couple. Thus, "honeymoon babies"! --BigMal // 12:53, 15 April 2015 (UTC)

I read this as being conceived at someone else's wedding - attending weddings often being a trigger for romantic thoughts. 03:25, 17 April 2015 (UTC)

Wait, I though Superman goes back in time not by "going against earths rotation, but simply by going faster than light? 19:53, 15 April 2015 (UTC)

The expected conception column is off, therefore the explanations may be off. Length of a human pregnancy is 38 weeks after conception, or 9 1/2 months, not the 9 months that is commonly portrayed. I'm not sure if Randall took this into account or not. 20:40, 15 April 2015 (UTC)

This is true, except you must have meant 8½ month not 9½ since 38 weeks is less than 9 month. Actually it is very close to 8,75 month. But anyway you are correct, that all the dates should be fixed to go 38 weeks back, not 9 months!--Kynde (talk) 20:54, 15 April 2015 (UTC)
Yep, that is what I meant, sorry 05:26, 16 April 2015 (UTC)
Updated with the correct dates, but the explanations haven't been proofread to conform with the dates 05:34, 16 April 2015 (UTC)
Fixed explanations, then realized you went for 40 weeks, not 38, so changed them to 38 weeks and fixed explanations again ;) Nealmcb (talk) 17:58, 16 April 2015 (UTC)
Even 38 weeks is idealised - I have a niece and nephew who were born 22 weeks after conception (4 years old now and doing well!) And term isn't until 41 weeks (from last menstruation) in France. 38 weeks happens to be a useful average in many parts of the world, but even healthy term pregnancies in USA/UK/Australia(/others?) covers the range of 35-40 weeks from conception. Also, with the rise of babies conceived by IVF, it's no longer quite so obvious what was happening 38-ish weeks before birth! 03:30, 17 April 2015 (UTC)
I've added to this conversation, but I put my addition below since it's so long after the fact. EebstertheGreat (talk) 23:08, 12 October 2022 (UTC)

No reference to the fact that November babies might be conceived on V day? Vkapadia (talk) 21:10, 15 April 2015 (UTC)

V-E day is not celebrated in the U.S. It has far less historical significance to us, since to us it was just an important date in the middle of a war. So the holidays that were included (like July 4 and October 31) make more sense in the U.S. for conception dates, even if they mean nothing internationally. EebstertheGreat (talk) 23:08, 12 October 2022 (UTC)

The real secret behind horoscopes and Nostradamus, is "vague shift"The Goyim speaks (talk) 01:36, 17 April 2015 (UTC)

In the second paragraph of the explanation, can we use either "i.e." or "for example," but not both? I don't have a particular preference for one or another; anyone who does is encouraged to make the correction. 06:32, 17 April 2015 (UTC)

I feel like there was a missed opportunity for Scorpio. Could have mentioned Valentines Day. (talk) (please sign your comments with ~~~~)

Aquarius could also, perhaps sadly/strangely, be prom babies. 22:29, 22 May 2016 (UTC)

Regarding about Gemini, which coincidentally I am one, doesn't apply to South-East Asian countries like Singapore(where I am born in), where the leaves doesn't change colors the whole year round. Same goes to the rest of the horoscopes as well. Boeing-787lover 13:56, 30 November 2017 (UTC)

The entire comic appears to be exclusively geared toward Americans. EebstertheGreat (talk) 23:08, 12 October 2022 (UTC)

Aries and to a lesser extent Cancer: kids went back to school, leaving house empty, or if your parents are in education (incl. college) they'd just started a new semester and met a bunch of new people. Singlelinelabyrinth (talk) 19:21, 26 July 2020 (UTC)

Gestation period[edit]

The accepted length of a pregnancy in the U.S. is 38 weeks, but this is not true everywhere. In France, for instance, the term is 41 weeks. Both of these are just traditional and not based on precise data. A good study to look to here is Jukic, Baird, Weinberg, McConnaughey, and Wilcox "Length of human pregnancy and contributors to its natural variation." This study is a very belated 2010 follow-up on a 1985 study on the rate of early pregnancy loss by Wilcox et al. They recruited women who had just ceased birth control because they intended to become pregnant. Although the study doesn't specify, they presumably had sex almost ever night, and according to the follow-up, urine samples were collected EVERY MORNING. These samples were tested for the presence of human chorionic gonadotropin (hCG), and if it was present above the threshold, the women were determined to be pregnant. Not much analysis was done on the question of how long after implantation it takes for hCG levels to rise above that threshold, but my tiny modicum of biological understanding suggests it should be hardly any time at all. The original study used this early-pregnancy data to measure the rate of loss of the fetus very early in pregnancy, controversially finding it to be around 30%.

The follow-up had a different goal. It re-contacted those same women and managed to recruit most (though not all) into a new survey. The goal was to determine which of these women had artificially shortened their pregnancies through cesarean sections or other methods in order to exclude them from the analysis (with measures taken to account for the biases this introduces). The women who were not excluded numbered 120 and had a (corrected) median gestational time (from ovulation to birth) of 38 weeks 2 days. But what is more interesting is that even after excluding premature outliers, this sample of 120 women had a range of 37 days. That means the earliest non-excluded birth was 37 days before the latest birth.

I think this explains why there is so much variation in how different countries treat births and why we never get a precise figure. Even within a single population of women (I think from around North Carolina? They don't say), the range of outcomes is enormous. Still, I think this is strong evidence that the average gestational period is closer to 38 weeks than to 40 weeks (or 41, as the French would have it). But at any rate, I imagine the magic number Randall had in mind was 9 months, figured as 3/4 of a year (i.e. about 274 days, or 39 weeks 1 day). EebstertheGreat (talk) 23:08, 12 October 2022 (UTC)