October is a good time for battling and fighting, but in November, it’s time to gather acorns.

That’s some of the timely advice from medieval astrologers featured in a new exhibit at the Getty Museum in Los Angeles called Rising Signs: The Medieval Science of Astrology.

For centuries, astrology was taught in major European universities as part of the scientific disciplines, including medicine. Kings hired court astrologers and consulted them on questions of diplomacy and military strategy. The position of the stars and planets at the time of a person’s birth was thought to affect the organs in their bodies and the diseases they might be most likely to develop. A Gemini was seen as more susceptible to respiratory problems, Sagittarius to muscle and joint problems, and Scorpio to sexually transmitted diseases.

Today, the study of the stars has shifted from an elite intellectual practice to a popular pastime. The Getty’s exhibit has already attracted at least one A-list celebrity, Andrew Garfield, who called the collection of illuminated manuscripts “kind of dope”. But it’s also proved challenging to some visitors, since it explains that their primary zodiac sign might actually be different based on medieval calculations.

The exhibit’s curator is Dr Larisa Grollemond, the Getty’s assistant curator of manuscripts, who is also writing a book on medieval wellness practices. Grollemond spoke to the Guardian about how the culture of astrology has changed over the centuries, what shocks contemporary astrology fans about medieval practices and why people in the middle ages would have loved Instagram. The conversation has been edited for length and clarity.

What are some of the big differences between how people use astrology today and how they used it in medieval Europe?

Contemporary astrology is much more focused on aspects of personality – often on questions of compatibility, romantic things, how you relate to other people. Astrology in the middle ages was a much more scientifically minded pursuit. People gave it a lot of credence as a principle for understanding the passage of time, and the influence of the sun and moon and other planets on the body. It had much more to do with daily life: diet, medicine, activities you should be undertaking at a particular moment of the year.

How many people across medieval Europe would have known their sign?

It’s a fascinating question, and it’s difficult to answer. The zodiac and astrology was definitely part of intellectual discourse. It was part of university learning. It was part of medical practice. It’s fair to say most people who are being treated for medical ailments of any kind would have come into contact with some sort of astrological ideas, whether that has to do with the balance of humors in their body [fluids like blood and phlegm, which were thought to influence personality], or the right time to bloodlet, for example. Whether that meant every peasant in the countryside of medieval France [knew their sign] – probably not.

You’re saying astrology was used as part of medical treatment? Would people who were sick and trying to get treatment be asked about their astrological sign?

Within medicine, you have a huge variation in practices. You might have someone like a barber surgeon, who is performing more elaborate, slightly more invasive surgeries and doing more bloodletting, and you might have someone who is a folk medicine practitioner who is prescribing herbal remedies or doing some light bloodletting. In both of those cases, there would be some consultation with astrological ideas, whether that meant a more in-depth analysis of someone’s sun sign and the time of year or their humors and their ailment – or it could be much more surface level: is this a good season to take medicine generally? It was believed that different signs ruled different parts of the body.

This exhibit explains to visitors that, according to medieval astrology, your astrological sign might be different from the one you have today. Why is that?

In the middle ages, the system was much simpler: each month was associated with a sign. With increased precision in astronomical observation, we have much greater information today about the position of certain constellations at certain times of year, which informs a greater specificity in the dates assigned to corresponding zodiac signs.

The idea that you could have a different sign in the middle ages – it shakes people’s identity in a way that I think is quite fascinating. Our astrological sign is part of our personality in a way that makes us legible to other people. I’m a September Virgo. In the medieval system, I’m a Libra, and I don’t identify as a Libra at all. People who have the same sign in the middle ages and today, they’re reassured that sign is really who they are, and they have a sense of superiority about it.

Was there as much skepticism about astrology in the middle ages as there is today?

It was pretty common practice for noble and royal courts to employ an astrologer, who consults with kings and rulers on macro-level decisions, military decisions. There were always whispering about counselors who are too influential, or which ruler put too much stock in what his astrologer says. That’s where the skepticism started to come in. They were skeptical of the idea of using astrological interpretation for future-telling, or aspects of divination, because it presumes something about humans being able to figure out God’s plan in a way that is maybe overstepping boundaries.

People who dismiss astrology today dismiss the whole idea. Medieval opinion was a little more nuanced.

We think today of astrology being separate from Christianity – maybe even a spiritual competitor, or an alternative to religious practice. Was that the case in the middle ages?

The zodiac signs often appeared in devotional or religious books, and the interpretation of the movement of celestial bodies was really consistent with a Christian worldview. It was believed that God not only divinely created everything, he individually placed the stars where they were ordained to go. The interpretation of those divinely created objects was consistent with what God wants humans to do.

You recently hosted a conversation with online astrologers. One of the panelists, Kyle Thomas, said there have been big changes in the culture of astrology in just the past few years, and that gen Z and other young people have a much more rigid and literal approach to astrological guidance than previous generations. What did you make of that?

There is something about communally tragic events like the pandemic that forces a re-evaluation of how people exist in the world, and the fact that people are using astrology to fill that void, to answer those questions, is such an interesting cultural shift. It makes me wonder if, in 600 years, people will think of 2024 as a particularly astrological time.

What’s one of the biggest similarities you found between astrology centuries ago and now?

Towards the end of the 15th and 16th centuries, some of these astrological treatises went into print. The information became much more widely disseminated, and there was an increased knowledge about different temperaments based on the humors and astrological signs. There was a cultural parallel between that, and people today having a greater access to the details of astrology via social media and apps. I think it’s fueling an increased interest in astrology, in the same way that print did in the fifteenth century.

You mentioned that medieval astrological illustrations are very popular with people on social media today; these very old images are still relatable, even sharable, content. Do you think people from the middle ages would also be able to relate to today’s online astrology content?

I believe the average medieval person would love Instagram, because it really is an inherently visual experience. They would be able to recognize some of the astrological content that we have today, especially representations of the Zodiac symbols. I think they would get a little lost in the idea of personality, like, ‘Because you’re a Virgo, you’re this.’

What advice does medieval astrology offer for us this October and November?

October is a good time for battling and fighting, that’s a very Scorpio thing. Also a good time for taking medicine generally. November is Sagittarius. It’s a particularly good time for gathering acorns, harvesting and getting married, as well as reconciling with enemies and bloodletting from the arms.

People always ask if it’s a good season for bloodletting. That’s all people want to know.