Although it officially turns full at 12:11 a.m. EDT on Monday (Oct. 26), the Hunter's Moon will appear almost perfectly full as it rises on both Sunday (Oct. 25) and Monday evenings, giving skywatchers two opportunities to observe it.

October's full moon is nicknamed the Hunter's Moon because it was traditionally a signal for hunters to prepare for the coming cold winter by hunting, slaughtering and preserving meat, according to Time and Date. That's an Anglo-Saxon name; Native American names for October's full moon include the Drying Rice Moon, the Falling Leaves Moon and the Freezing Moon.

The first chance to see the Hunter's Moon comes just before sunset on Sunday, when the almost-full moon will rise in the east. The second opportunity comes on Monday, when the moon — still essentially 100% illuminated — will again rise just after sunset. Because it will be in a slightly darker sky, Monday's moonrise will likely be more dramatic.

As it rises Sunday, the moon will appear in the constellation Aries, and Saturn will be to its upper right. On Monday, it will rise above the Pleiades open cluster (M45).

For the best view on either evening, find somewhere with a clear view low to the eastern horizon and be in position shortly before moonrise where you are. An elevated viewpoint, open field or coastline is ideal because buildings, trees and hills can delay the moment the moon becomes visible.

Although the full moon will look magnificent with the naked eye, a backyard telescope or good stargazing binoculars can help you zoom in on various lunar features.

The Hunter's Moon may appear unusually large thanks to the "moon illusion," which makes the moon seem bigger when it's seen beside familiar objects, such as trees and buildings, near the horizon. The illusion stems from the fallacies of how our brains use distance to perceive size.

October's Hunter's Moon isn't a supermoon, but it comes immediately before a notable sequence of four consecutive supermoons. The first will be the next full moon, the Beaver Moon, on Nov. 24, followed by full moons in December, January and February. A supermoon occurs when a full moon happens while the moon is relatively close to Earth in its slightly elliptical orbit, making it appear somewhat larger and brighter than average.

How much do you know about the moon? Test your lunar smarts with our moon quiz!

'> Watch the full 'Hunter's Moon' rise next to Saturn this weekend Nazca Lines there are, but they number in the thousands, with new geoglyphs continuing to be discovered with the help of AI.

But why were the Nazca Lines built?

Scientists have been debating this question since the lines were first formally investigated in the early 20th century. Although the definite answer remains unknown, experts have proposed various reasons for the famous geoglyphs.

There "are many ideas out there about their function and meaning," Ana Nieves, a professor of art history at Northeastern Illinois University, told Live Science in an email. "If you look at the area's geoglyphs closely, though, there are different styles of geoglyphs, some are relatively larger and some smaller, some are on hillsides while some are on the pampas. It is not likely that a single explanation would apply to all."

Different perspectives

A vast array of theories for the lines' uses have been proposed over the years, with the most outlandish of these suggesting that they were sites for aliens to land spaceships.

More grounded theories link the lines to cultural and religious practices.

"The question of why the geoglyphs exist is difficult to answer, given that we lack any type of preserved oral or written testimony," Karsten Lambers, an art history professor at the University of Augsburg in Germany, wrote in an essay published in the book "Los geoglifos: imágenes y escenarios en el desierto de Nazca y Palpa [The Geoglyphs: images and settings in the desert of Nazca and Palpa]" (University of Augsburg, 2017). It's possible that the uses for the geoglyphs changed over time, he added.

One suggestion is that they were initially used to mark routes for travelers and caravans and later became places for gathering and feasting.

In a 2026 study, researchers noted that some of the earlier Nazca geoglyphs were constructed on hillsides, seem to be located on trails, and "were visible from considerable distances." This means the geoglyphs may have been used to mark travel routes and indicate areas that were good for temporary camps. The team suggested that the markings became places for gathering and feasting.

Another idea is that the geoglyphs were used to match astronomical alignments to serve as a kind of calendar. In December 1941, historian Paul Kosok examined the lines and determined that they had astronomical alignments. Mathematician Maria Reiche followed up on Kosok's work, examining the Nazca Lines for more than 40 years to identify many geoglyphs she believed have an astronomical relationship to various celestial bodies, a research team noted in a 2021 paper. Yet after analyzing the geoglyphs, the modern-day team found that only a relatively small number had a possible alignment to a star or solar event such as a solstice.

"The results suggest that the geoglyphs, as a whole, certainly cannot be interpreted as a calendar system," the team wrote. However, this doesn't discredit the idea that the Nazca Lines had an astronomical significance, Christiane Richter, a researcher at the University of Applied Sciences in Germany and first author of the 2021 paper, told Live Science in an email.

Since the paper's publication, Richter and her team's research has indicated that around 8% of the geoglyphs have some form of lunar alignment. It is "highly probable that celestial bodies played a role in the creation of the drawings," Richter said in an email.

Offerings such as ceramics, crabs, corn and earrings made from Spondylus shells (a genus of bivalves known as thorny oysters) were also placed on low rock platforms near some of the geoglyphs, especially those shaped like trapezoids, Lambers noted in his paper. Spondylus shells are normally found farther north, in Ecuador, but during El Niño events, they can appear farther south, in Peru. These shells, alongside crabs and corn, tend to be associated with water and fertility, Lambers noted.

Another idea is that the geoglyphs themselves may have been used for ritual processions. Some of the geoglyphs are made with a single, uninterrupted line," Nieves said. "Those are the ones that would lend themselves for processions since people could walk them in a single file."

Some of the activities at the Nazca Lines may have helped foster a sense of community and equality, said Darryl Wilkinson, a professor of religion at Dartmouth University who has written about the geoglyphs. For instance, "walking the lines was a group activity, and participating in such processions would have likely created a feeling of community among those involved," Wilkinson told Live Science in an email. "I interpret the Nasca lines as geared towards the realization of a relatively more equal expression of community."

Whatever the reasons for their construction the Nazca Lines are awe inspiring today. Lambers wrote in his essay that the Nazca people who built them "succeeded in transforming one of the driest deserts in the world, over the course of many centuries, to serve the region’s inhabitants as an expression of their cultural ideas and a setting for their social activities."

'> Why were the Nazca Lines built? she said on a podcast that she felt she was "back at square one, where I don't know what's going on with me."

Applegate's case is not totally unique, although MS diagnosis has improved over the years. Studies offer different estimates of how frequently MS is misdiagnosed, with rates ranging from 5% to over 40%, depending on the patient population and clinical setting. There is also some degree of underdiagnosis — cases in which people with MS aren't flagged as having the disease.

So, how difficult is MS to identify, and what does that mean for patients? Live Science spoke with experts about the current state of MS diagnostics and the improvements that may be coming in the future.

"It's also really important that doctors and patients be aware that it's not inappropriate to revisit a diagnosis — to make sure it's right," Dr. Ari Green, chief of the Division of Neuroimmunology and Glial Biology at the University of California, San Francisco, told Live Science.

The importance of early diagnosis

MS is an autoimmune disorder in which the immune system attacks the central nervous system, meaning the brain and spinal cord. These attacks harm neurons directly and also take aim at myelin — a fatty, insulating substance that coats neurons' outgoing wires and helps them send signals efficiently.

This damage leads to distinctive scarring in nerve tissue and causes a range of symptoms, including vision problems, muscle weakness, tingling sensations, dizziness and bladder control issues. Patients with untreated and advanced MS can lose the ability to walk and stand or, in some cases, develop partial or complete paralysis.

These severe outcomes are becoming rarer as treatments have improved significantly, Green said. Current treatments keep immune attacks at bay and thus prevent further nerve damage.

"It's moved from people ending up with severe, profound disability at 10 or 20 years of disease, and now it's at like 30 or 40 years of disease, they have modest disability," Green told Live Science. The disease most often emerges between age 20 and 40, although it can occur in any age group. Importantly, Green said, "the earlier people initiate treatment who have MS, the better they do over the long term."

For that reason, it's important to reach an MS diagnosis efficiently, so that patients can start that critical treatment, said Dr. Yohance Allette, a neuroimmunologist and researcher at Penn State Health. "You're trying to be as proactive as possible with this."

"A diagnosis of exclusion"

However, there is no single, surefire test that can reliably show that a person has MS. "With MS, it comes down to the keyword 'criteria," Allette said.

MS experts have compiled a list of criteria, which are updated periodically, that reflect how the features of MS show up in lab tests; brain, optic nerve and spinal cord scans; and patients' symptoms. (Green was among the dozens of experts involved in the latest update, which was conducted in 2024 and published in 2025.)

So, what does diagnosis look like for a patient today? The first step is to recognize symptoms that might point to MS.

Those early symptoms — such as issues with balance, vision or bowel control — vary significantly from person to person and may not immediately raise red flags that the patient has a neurological problem, Green said. The way those symptoms emerge can be a clue, though; typically, MS symptoms worsen over the course of a day or a few days and then dissipate, he noted.

Once concerning symptoms are flagged, MRIs of the brain and spinal cord are taken. The scans may reveal evidence of myelin damage, and neurologists note the shape, size and location of those lesions. Damage often appears near blood vessels, since that's where immune cells access the brain, Green noted.

Other conditions — like migraine, uncontrolled diabetes or vascular disease — can also come with some myelin damage, so it's key to look for specific patterns related to MS. Neurologists who specialize in MS are practiced at this task, while doctors in other neurological specialties may not know how to distinguish MS-related myelin damage from that caused by other conditions, Allette and Green both noted.

MRIs of the optic nerves can also show MS-related damage, and these scans are emphasized in the latest diagnostic criteria, Allette noted. Electrophysiologic tests, which assess the function of nerves, are also "super important because they tell you something totally different than just seeing a lesion on MRI," Green said. Further signs of MS can be found via spinal taps, which sample the fluid around the brain and spinal cord that may carry proteins and inflammatory cells related to MS.

In addition to collecting these clues, doctors must rule out diseases that look similar to MS. These include neuromyelitis optica and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) — two other autoimmune conditions that affect the central nervous system. Both these diseases are associated with distinctive, rogue immune proteins, called autoantibodies, that latch onto various parts of the nervous system; those specific antibodies are not seen in MS.

Other conditions — such as the inflammatory disease lupus and neuromuscular disease myasthenia gravis — can sometimes look like MS at first glance, as well. Some of these "MS mimics" can be ruled out with data from spinal taps or antibody tests, while others require a more laborious battery of assessments.

"Ultimately, it's a diagnosis of exclusion," Allette said. "There are things that you can rule out quickly," while others take time to investigate thoroughly.

Conditions like MOGAD and neurosarcoidosis, an inflammatory condition sometimes mistaken for MS, can actually be worsened by MS medications, Green noted. So if a patient's MS flare-ups worsen after they start a treatment, that could hint that something else is the culprit, he said. But because there may be long gaps between flare-ups, doctors may need to track a patient for some time before their worsening becomes apparent.

Gaps to fill?

Given all the tools available, a patient can be reasonably confident in their MS diagnosis, Green said.

"In general, there's a fair amount of diagnostic confidence that comes with MS diagnosis today," he said. However, that confidence is highest when the tools are in the hands of a specialist who is following the most up-to-date criteria, he noted. The test results require interpretation, and that's one place where uncertainty can creep in.

Regarding Applegate's circumstances, "to speak bluntly, I think the case came as a bit of a shock because we always expect that part of society to have quick access [to high-quality medical care]," Allette said. For some patients, the road to accessing specialty MS care can be long, which can result in missteps, and even misdiagnoses, along the way. Applegate went five years with an incorrect diagnosis, but "would that have been seven or eight years for somebody who doesn't have that access?" Allette speculated.

Without knowing the details of Applegate's case, Allette and Green said it would be difficult to speculate on what resulted in her misdiagnosis. (Applegate mentioned that her brain scans had been reassessed with a "new technology," but didn't go into specifics.)

Looking toward the future of MS diagnostics, Green and Allette think emerging proteomic tests hold a lot of promise. Such tests generate a profile of the proteins and smaller fragments, called peptides, in a patient's blood or cerebrospinal fluid. They can be designed to look for proteins involved in driving the underlying immune attacks, as well as signs of nerve damage that MS wrecks, they explained.

These in-depth, protein analyses could help paint a more comprehensive picture of MS, which could ultimately help scientists "look at that whole system in concert" to reach a strong diagnosis, Allette said.

No proteomics-based diagnostic tests for MS have been approved yet, Green clarified. And even with those upcoming advances, Green doubts there will ever be a simple, one-time test that can determine a patient has MS. "I think that's probably unlikely, that it would ever be that straightforward," he said.

He does think that, in time, scientists could pare down the number of tests required to reach a diagnosis, but he argued that the clinical evaluation conducted by a neurologist will likely remain crucial. "I'm doubtful that there's going to be a test that will fully replace that," he said, "at least in the foreseeable future."

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'> Christina Applegate misdiagnosis: Why can MS be difficult to diagnose?

Other commenters echoed this sentiment. "It will never happen as some cheap alternative to electric or petrol driven vehicles," one person responded. "Gravity is master on this planet so to rise above that and be floating or propelled around on some sort of air current, Nah! I cannot imagine the damage that will take place in any livable area, towns, suburbs, cities, parks, etc, etc., that list is endless. And imagine the protests should a general public be allowed to dive and fly above any or all livable areas."

Not everyone was as adverse, with another commenter remarking on how far Tesla's technological development has come. "The flying roadster is a statement of what Mr. Musk can do with technology more than anything else. In the same way he can make the Roadster fly, be sure that the technology designed into the Tesla Y, the Cybercab or the Starship are at the very frontier of science. Mr Musk has singlehanded revolutionized the car industry and space travel in less than 20 years (the first Tesla car was sold in 2008). No small feat."

Do you agree or disagree with our readers? Tell us your thoughts in the comments.

'> 'Most people can't handle driving in 2 dimensions let alone 3': Readers respond to our poll about flying cars

However, in its current form, the same AI technologies that add watermarks can also strip them away, other experts warned.

New ways to hide watermarks

The unveiling of the AI program AlphaFold in 2020 was a milestone in protein engineering. The tool, which won Demis Hassabis, John Jumper and David Baker the Nobel Prize in Chemistry in 2024, can reveal the 3D structure of a protein from the sequence of its building blocks, called amino acids. Proteins fold like origami, adopting 3D shapes that dictate their function.

However, AlphaFold's technology also opened the door to generating brand-new proteins that could be used to create biothreats, including viral proteins that can evade our immune systems and existing vaccines.

"Anything that can be used for good can be used for bad," said George Rose, professor emeritus of biophysics at Johns Hopkins University.

Current screening tools identify novel dangerous or restricted molecules by seeing how similar their amino acid sequences are to those of recognized threats. But the problem is that AI could come up with proteins that don't look like anything we've ever seen. That's what the new watermarking technique aims to solve.

The DeepMind team has framed the watermarking effort as a "family" of related techniques they call SynthIDBio. The first member of this family is SynthIDBio-sequence, which encodes watermarks into the amino acid sequences of proteins created by a program called ProteinMPNN.

When users tell ProteinMPNN the desired 3D shape for their protein, it chooses amino acid options that ultimately fold into that shape. SynthIDBio-sequence subtly influences how the program chooses each amino acid according to a secret watermarking "key." Once the sequence is generated, anyone who knows the hidden code can assess how likely the sequence is to have been created under the key's bias. In their recent study, the DeepMind team showed that proteins built with this watermark could still bind to their targets as well as non-watermarked proteins.

A sister technique, called SynthIDBio-structure, instead embeds a watermark directly into the protein's structure. It does this by altering the function of AlphaFold 3, DeepMind's flagship protein prediction algorithm.

When AlphaFold predicts a structure, SynthIDBio-structure gives it a side mission: The AI must make minuscule tweaks to how the atoms in the protein are arranged. These tweaks can be picked up by a detector later, and they're small enough that they don't look like obvious distortion.

In a test, these two systems created hidden watermarks that could be detected with incredible accuracy, flagging more than 99% of watermarked proteins and correctly ignoring 99.9% of non-watermarked proteins.

How to bypass a protein watermark

Live Science spoke to several experts who agreed that SynthIDBio was an impressive technical feat. However, they said it wasn't ready for widespread implementation yet.

The two techniques are "effective but brittle," Bruce Wittmann, a principal applied scientist at Microsoft, told Live Science in an email. That's because, as the DeepMind team also notes in their paper, the watermarks can be easily removed.

"For sequences, watermarks can be removed by 'resequencing' — effectively, altering the protein amino acid sequence such that the watermark is no longer detectable," Wittmann said. "For structures, watermarks can be removed by adding noise to or otherwise modifying the spatial coordinates of the structure." Screening tools wouldn't be able to detect if a watermark had been removed from a protein.

Experts are also skeptical that watermarking would provide a long-term solution for biosecurity.

An indelible watermark could identify who originally made a nefarious protein, or identify when a user was accessing a protein generation software without permission. This might deter some criminals, but terrorists looking to create a novel protein for a biological weapon would be less likely to care about being identified after a successful attack, said Max Brackmann, a chemical, biological, radiological, and nuclear arms expert at the Spiez Laboratory in Switzerland.

Additionally, the vast majority of software for protein prediction and generation is open-source, meaning much of the code is freely available to use and modify. That makes it far harder to bake watermarking into these programs. Wittmann warned that the field would have to shift toward closed-source models before watermarks could become an industry standard.

He added that watermarking could act as one layer of a biosecurity defense shield, rather than offering standalone protection. Top-down regulation would be challenging to enforce. "I imagine it would be very difficult to ensure the regulations were being followed," he said.

Rose was even blunter about regulating the use of generative proteins.

"I'm convinced it won't work," he said. "Once there's a sweet technology that does something, government regulation to keep it under wraps has never been really successful."

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'> Scientists can now 'watermark' AI-generated proteins to deter bioweapon creation. But will it really work?