I've been reading about how dark matter and dark energy are used to explain some puzzling observations in the universe like the way galaxies rotate or why the universe's expansion is accelerating.

While I understand these concepts are supported by a lot of evidence, they still feel like placeholders for something we don't fully understand yet. This got me thinking:

Could parallel universes or extra dimensions offer an alternative explanation? For example:

• Could gravitational effects from nearby universes or dimensions mimic the gravitational pull we attribute to dark matter?
• Might dark energy arise from interactions with higher dimensional spaces?

I’d love to hear if there’s any scientific basis or ongoing research exploring these ideas, or if these concepts are too speculative compared to the current models.

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Abu Mahmud Hamid ibn Khidr al-Khujandi, one of the greatest astronomers and mathematicians of the Islamic East, captivated his contemporaries and subsequent generations of scholars with his intellect, knowledge, and groundbreaking discoveries. Al-Biruni, in his work The Determination of the Coordinates of Places for the Correction of Distances between Cities, referred to Khujandi as "unparalleled in his era in constructing astrolabes and other instruments."

Life and Contributions

While the exact year of Abu Mahmud Khujandi's birth remains uncertain, most scholars estimate it to be around 940 CE. He spent his early years in his hometown of Khujand, where he likely acquired his foundational knowledge in astronomy and instrumentation. Later, he moved to Ray (modern-day Iran), where he built an observatory on Mount Tabarak under the patronage of the ruler Fakhr al-Dawla. There, he constructed the Fakhri Sextant, the largest and most precise instrument of its time, named in honor of his patron.

Khujandi also briefly lived in Baghdad, where

he is believed to have built an astrolabe, further highlighting his contributions to the development of astronomical tools.

The Fakhri Sextant

The Fakhri Sextant was a monumental achievement in astronomical instrumentation. With this device, Khujandi measured the obliquity of the ecliptic—the angle between the celestial equator and the path of the Sun across the sky. In 994 CE, he calculated this angle to be 23º 32′ 21″, an unprecedented level of accuracy for the time. Prior to his measurements, calculations had been accurate only to the nearest minute; Khujandi refined them to the second.

Al-Biruni, who visited Khujandi's observatory and studied his instruments, praised the sextant in his book Geodesy, stating that it surpassed all previous and subsequent instruments in size and precision.

The Astrolabe of Khujandi

Khujandi’s astrolabe, considered a masterpiece of its kind, is currently housed in the Museum of Islamic Art in Doha, Qatar. Made of bronze, it measures 151 mm in diameter and 6 mm in thickness. An inscription on the reverse side reads, "Made by Hamid al-Khidr al-Khujandi in the year 374 AH" (corresponding to 984/985 CE). This astrolabe has been the subject of significant scholarly attention, including studies by Dutch historian Wilfred de Graaf and Islamic science historian David A. King.

Influence and Legac

Khujandi's work greatly influenced later scholars, including Jamshid al-Kashi, who constructed an even larger sextant in Samarkand under Ulugh Beg's guidance. The Fakhri Sextant also inspired the design of instruments in observatories in Jaipur, Delhi, and other cities.

Until Galileo's invention of the telescope, the Fakhri Sextant remained the most precise astronomical instrument in history.

Honoring Khujandi

In recognition of his contributions, the planetarium in Khujand was named after Abu Mahmud Khujandi in 1986, and a semi-portrait of the scholar was erected. In 2020, the city inaugurated a park dedicated to him, featuring a 6.5-meter statue, a modern planetarium, and a model of the Fakhri Sextant. Additionally, a documentary titled Abu Mahmud Khujandi was produced in 2020 and is available on YouTube.

Khujandi’s legacy serves as a reminder of the remarkable achievements of Islamic scientists during the Golden Age and their enduring influence on modern science. His contributions to astronomy, mathematics, and instrumentation reflect the ingenuity and brilliance of this era, earning him a rightful place among the giants of scientific history.
Rizoi Bakhromzo

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Reaching for the Stars: Carl Sagan’s Contact and the Quest for Meaning

Carl Sagan is undoubtedly one of the most brilliant minds I’ve had the pleasure of exploring through his writing. Earlier this year, I embarked on a journey through Sagan’s works—a decision that came about almost on a whim. I had made a New Year’s resolution to read more non-fiction, and in January, I picked up Cosmos. I was blown away.

From there, I read Pale Blue Dot, followed by The Dragons of Eden, The Demon-Haunted World: Science as a Candle in the Dark, and Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium. Each book left me more enamoured than the last. Sagan's ability to convey dense, complex concepts with such eloquence and clarity is nothing short of brilliant.

Initially, I didn’t plan to immerse myself so deeply in Sagan’s catalogue. But as I turned the final pages of Cosmos, I couldn’t resist diving headfirst into more of his work. His voice, his ideas—they simply resonate with me.

When I picked up Contact, it was no different. I wasn’t surprised at all by how much I loved it. The book feels like a culmination of his non-fiction and essays, woven into a scientifically rich work of fiction. It reads like a companion piece to The Demon-Haunted World, so much so that I’d argue it’s essential reading to fully appreciate the broader ideas Sagan explored. That’s not to say these books must be read in a particular order, but enjoying one will undoubtedly enhance the experience of the other. Contact makes it clear where many of its ideas originated.

One of Sagan’s most impressive feats is his ability to navigate the interplay between religion and science—two deeply contested subjects—with breathtaking ease. In Contact, he takes the principles of clear, rational thought from his nonfiction works and integrates them seamlessly into a deeply entertaining narrative.

That said, Contact is a slow burn. It’s quite technical, which might deter some readers who find it dry. But I urge anyone who picks it up to give it a chance. In my opinion, the deliberate pacing works exceptionally well as Sagan balances philosophy and science on a razor’s edge with effortless grace.

Everything he’s written (at least, what I’ve read so far) feels purposeful. Whether he’s discussing humanity’s place among the cosmos, reflecting on our “pale blue dot,” or exploring skepticism and religion, each idea fits perfectly into his broader narrative. And there’s so much more to unpack.

Contact is not only a great entry point into Sagan’s vision of humanity, but it’s also a fantastic standalone story. The narrative remains grounded, set mostly on Earth, with technology that feels plausible and rooted in reality—only stretching into the speculative where necessary to tell this epic story of humanity’s place among the stars. The level of detail is astonishing.

Interestingly, I find it hard to categorize Contact purely as a science fiction novel. Perhaps this is a semantic argument, but to me, it feels more like a fictionalized exploration of his scientific ideas. It’s every bit as quintessentially “Sagan” as his non-fiction works.

The book tackles profound philosophical questions with incredible nuance. Questions like, “What is God?” and “What would happen if we discovered a more intelligent presence in the universe?” are explored in ways that leave a lasting impact.

While this review may feel more like a love letter to Carl Sagan than a focused critique of Contact, I think that’s a testament to the man himself. His brilliance, humanity, and unique outlook on the universe shine through in every word he wrote. Contact is no exception.

If you’re a fan of science fiction, this book is a must-read. If you’re someone who values clear thought and seeks to understand the world around you (and I hope that applies to everyone), pick up this book. But don’t stop there. Dive into the rest of Sagan’s works—they’re profoundly important.

Carl Sagan’s contributions to bringing science into public consciousness cannot be overstated. For that, I’m endlessly grateful. He has had a profound impact on my life, and I’m confident that if you give his work a chance, you’ll feel the same way.

Check out my blog where I talk about book content like this: https://blog-on-books.blogspot.com/

Any fellow amature astronomers in yuma az

Hey folks, ive been seeing video reviews of the new seestar s30 and the older seestar s50 and thought they were really cool, but it seems as if though a lot of hardcore amateur astronomers have a strong disdain for the idea of a smart telescope. So i wanted peoples opinions on it. Me personally as someone who doesnt have 2000$ to speend on a deep sky rig, i definitely see my self buying one of these. The ease of use and budget friendliness make these scopes a great option in my opinion. As for it doing the a lot of the work for you, i dont understand how this is a bad thing. Imagine if we never made automated stacking soft wares because it did the hard work for you, or if we still rode around on horses because cars made things to convinient. I want to know what Amateur community thinks so type away but stay respectful!

I've recently discovered home planetariums and will probably buy one soon.
Has anyone done or know of any comparisons between especially the quality of different star discs for them?

I am looking at the Sega Homestar Flux mostly because of the many different alternative star discs from various publishers. While searching for discs I found not just Sega, but also Miller Engineering, Astrial and Kweller/Redmark make them (for the same product).
(Although there are others who have interchangeable star discs like Pococo and Orzoz, or several for Uncle Milton products.)

The main selling point of Miller Engineering is that their star discs are apparently much more detailed. For example, their Northern Hemisphere star disc shows 1.2 million stars while Sega's original shows 60,000. I don't know how ME's other discs compare or how the same type of disc from the other publishers compare.

I tried googling various combinations and the only thing I found was comparison videos between Sega's original discs and the ones from Miller Engineering (although usually as part of comparing different home planetariums), but none of the others.
And I found that Astrial has some kind of partnership with Sega. I assume that means that their discs are of a similar quality. But I haven't found anything that confirms that.

Is the quality of the others closer to Sega or Miller Engineering or somewhere in between the two? Are all the discs from Miller Engineering more detailed or only some of them? Has anyone done a direct comparison?

I am building a telescope and need some help aligning the distance between the primary and secondary mirrors (Newtonian). The 6” mirror I am using had no information on it as I got it second hand. I used a flashlight to find the approximate focal point, but when I assemble it I can’t get a view. I’ve tried to manually move the secondary mirror along the scope to find the best point, but with no success. Any ideas?

Hello!

I read about suncalc and case of the malaysian airlines MH17, in which this technique was used to estimate the time a of a picture of the BUK that shot the airpline. Reference: https://www.bellingcat.com/news/uk-and-europe/2014/07/28/two-more-key-sightings-of-the-mh17-buk-missile-launcher/

I´m trying to write an article which main idea is to answer this question: Given a shadow length, object height, and exact timestamp of the picture, can I calculate areas in the world map where this object may possible be?

This is relevant for geolocation, as a lot of picture from cellphones and digital cameras have relatively reliable timestamps. So I started to some research and tried to write some code.

I tried to geolocate this pole on this (no special reason about it): https://www.suncalc.org/#/-7.1457,-34.8044,19/2016.09.02/09:38/1/1

If I have the UTC time of the image, by brute forcing calculations, I can estimate the area with this code, using a tolerance of 0.01 on solar angle: https://gist.github.com/albcunha/13f112eeb9f50d70cfe24040d6a44e56 . On the variables I provided, I get this map plot:

https://preview.redd.it/975e8bxp8h1e1.png?width=1291&format=png&auto=webp&s=b8b95806cec5002cfc66c2270b5ed58e6f952743

Then I tried to make the same graph, but now, it would use local time. So I tried first using a theorical local time, without considering real timezones, based on longitude only, with this code: https://gist.github.com/albcunha/fddb9123b35a4f5d102f936165dd2938

Then I run in some problems. The the real localtion I used as reference, is actually on -2 timezone, but Brazil adopts -3 for the area. So, if I correct the local time to the correct theorical timezone, it works. In this case, I change the local hour from 09:38 -3 UTC to 10:38 -2UTC, I get this plot that passes trough the correct point:

https://preview.redd.it/ul0coj2gdh1e1.png?width=3056&format=png&auto=webp&s=fe02c2aa4de927f9d23c9bc661a7afd55b8f5e2d

Then I tried to make something similar, but considering the correct timezones. The problem is that I dont find any good strategy, by brute force, to make this graph.

So I would like some help.

1. First, maybe someone has already done this work and I can´t find it on the internet.

2. What would it be a good strategy to make the same graph, but with real timezones? The solution i found was to plot all latitude and longitudes, check timezone on it and then check if solar angle and local time matches, which is very computer intensive.

3. Also, maybe there is a smarter way to do these calcuations, as I´m pretty much relying on brute force, as my mathematical skills are very low standard.

Thanks for any help!

Hiii so for some context I am a international student (15F) intending to apply to colleges in the us in 1-2 years and I am at this stage of life where I am wondering if I will make the right choice for my future.

Ever since I was a kid I have always been passioned about stars, laws of physics, how the world works ect. I’ve grown up with the idea that one day I’ll be an astronomer or astrophysicist, but now I’m not sure if it’s the right path for me. Freshman year I did some research about the process to become an astrophysicist and everything and I was a bit taken aback by the fact that I had to get a phd if I wanted to become one. As a teenager that come from a low income family somewhere in Africa who have no means of funding my education other than scholarships and loans, I quickly understood that this wasn’t gonna be easy. Still I didn’t give up, I searched for ways to achieve my dreams and now I think about pursuing a double major in physics/astronomy and computer science So I can work as a computer scientist while doing my masters and saving up so I can pay for my students debt and do my phd. But I am worried about whether or not this will work out, as both cs and astronomy are 2 hard majors and if I will be able to handle that + working part time. I don’t want to give up my dream nor do I want to pursue something other than my dream, I see so many adults having regrets about not doing so and this motivates me to never give up, but there is always this uncertainty in the back of my head. So I’d like to ask to all these astronomers out here if it’s really worth it ?

The Heart Nebula, also called IC 1805, is a stunning cosmic feature located in the constellation Cassiopeia, known for its "W" or "M" shape. About 7,500 light-years from Earth, this nebula has a heart-like shape, glowing brightly among the stars. Despite its romantic appearance, the Heart Nebula is a busy region in the universe. Stretching about 200 light-years across, it's one of the biggest nebulae in the night sky. It's an emission nebula, meaning its gases, mostly hydrogen, shine with red light caused by the energy of young stars forming within it. The Heart Nebula is part of a larger system with the Soul Nebula (IC 1848). Together, they create a breathtaking view often called the "Heart and Soul Nebula." At the center of the Heart Nebula is Melotte 15, a cluster of young, massive stars. Some of these stars are 50 times larger than the Sun. Their radiation and winds shape the surrounding gas, creating structures like glowing pillars. This nebula is also a birthplace for new stars, with hydrogen lit up by ultraviolet light from young stars, giving it its fiery red color. Photos of the Heart Nebula are often captured using powerful telescopes like Hubble or advanced observatories. The colors in these images are enhanced to highlight different elements like hydrogen (red), oxygen (blue), and sulfur (yellow), showing the nebula's vibrant beauty. Beyond its beauty, the Heart Nebula is a key site for scientists to study how stars form and how gas clouds change over time. Radiation from its stars constantly reshapes the nebula. In the future, one of the massive stars in Melotte 15 may explode as a supernova, altering the nebula's structure and leaving behind a legacy of the ever-changing universe.

Last night, something cool happened. Not only was it a supermoon, the last of 2024, but this supermoon also went directly in front of the famous Pleiades star cluster! This happens fairly often, but is beautiful every single time.

This was my first ever attempt at an HDR moon photo, and while others can absolutely crush me in this catagory, I still think it's a pretty decent result!

🔭 Skywatcher Evostar 72 📷 Canon EOS Ra ⚙️ Single 7s and 0.01s exposures 💻 Blended and processed as HDR in GIMP