gravity on a spaceship, akin to the giant rotating ring from Stanley Kubrick's 1968 film "2001: A Space Odyssey."

But is that technology ever coming, or will it remain science fiction?

"There's really no reason it couldn't happen," Torin Clark, an associate professor of aerospace engineering at the University of Colorado Boulder, told Live Science. "From a technical perspective, this is something that could happen in the very near future."

In fact, artificial gravity has almost made its way to space before. The Centrifuge Accommodation Module was a planned 8.2-foot-wide (2.5 meters) centrifuge for the International Space Station (ISS), but the project was canceled in 2005 for budgetary reasons.

"[Artificial gravity] is one of those things ‪—‬ like all of a sudden, it's super popular, and then all of the scientists at NASA and everybody … have a lot of funding to understand how to actually implement this, and then it just dies," Ana Diaz Artiles, an associate professor of aerospace engineering at Texas A&M University, told Live Science. "And then it comes back, and dies, and comes back. I've been going through a couple of these cycles in the time that I've been doing this."

Besides budgetary concerns, there are questions about how such a solution would be implemented.

"Everybody agrees it's a good thing to do. The problem is that we don't know how to implement it," Diaz Artiles said. "How much gravity do you need? How big does [the device] have to be? How long do you need it to be? And how long do you have to use this? Should we use continuous gravity or a short-radius centrifuge, something where you go in and out?"

Researchers have three main approaches for creating artificial gravity. One is the classic sci-fi idea: a giant ring that rotates passengers' entire living quarters so they live and work under forces similar to Earth's gravity.

"You have a relatively long radius, which means you don't have to spin very fast to create gravity," Diaz Artiles said. "But this is massive. You can't get all the parts up there in the same spacecraft — you need multiple spacecraft and to assemble everything. So, of course, you can see what a big endeavor this is."

A short-radius centrifuge is a more feasible option. It's essentially a tube with a radius of 6 to 10 feet (1.8 to 3 m) that spins to simulate gravity. A passenger sits or stands inside, with their head closest to the center of rotation, so the spin generates the strongest pull down toward their feet.

Instead of allowing passengers to live in artificial gravity, this smaller device would be used in short daily sessions. "It's kind of like an exercise device," Diaz Artiles said. "In the ISS, you have a treadmill, you have this resistive exercise machine, so you go there for 30 minutes to do your exercise, and then you get out."

The final option is for spacecraft to create gravity via linear acceleration. This works in the same way that an accelerating car pushes passengers back into their seats, except the spacecraft would be oriented to push an astronaut's feet into the floor. To slow down, the spacecraft would turn around, firing its thrusters in the opposite direction to decelerate smoothly while maintaining a roughly similar gravity for its occupants.

"But then you need something like an engine that is able to accelerate all the time," Diaz Artiles said. "And propulsion-wise, I think we're not there yet."

Although a short-radius centrifuge is the most feasible approach in terms of both cost and engineering, it does have some drawbacks. For one, its fast spin can induce the Coriolis cross-coupled illusion ‪—‬ a sensation of tilting or tumbling that happens when you tilt your head off-axis while rotating.

This is the effect that causes motion sickness, Clark said.

However, Clark and his team have found that people can build a tolerance to the sensation with training, simply by being in a slowly spinning centrifuge and gradually increasing the speed when they no longer feel the sensation.

"If you very slowly, incrementally increase the spin rate … and do that not just over one session but over multiple sessions across multiple days, as far as we could tell, anyone can be made to incrementally acclimate to the rotating environment [of] up to 20 to 30 rotations per minute," Clark said.

Would artificial gravity prevent harmful effects on the body?

But researchers still don't know how fast the centrifuge would need to rotate, or how long someone needs to spend inside it, to benefit. Long periods in microgravity can lead to bone and muscle loss, loss of aerobic fitness, blood clots, and visual issues from fluid shifts in the eyes. The hope is that artificial gravity could prevent those effects, but exactly how much gravity is necessary remains an open question.

Studies of people on head-down tilt bed rest ‪—‬ the standard research method for simulating spaceflight deconditioning ‪—‬ have found that 30 minutes a day in a centrifuge did prevent some loss of muscle function.

"Thirty minutes a day … maybe is not enough," Clark said. "Maybe an hour or even two hours a day, and maybe at higher G levels, would be beneficial."

But these studies are expensive and time-consuming. "It's very difficult," Diaz Artiles said. "I think people are interested in this concept, but we just don't have a good answer."

In the end, it's not a technological challenge that's keeping artificial gravity from being used in space; it's knowing the best way to employ it and securing the budget for it.

"We know how to do this. As humans, we have done more difficult things," Diaz Artiles said. "We need the money, but we also need to better understand the need."

See how much you know about human exploration into space with our spaceflight quiz!

'> Could we ever create artificial gravity on a spaceship? bicephaly, is a rare developmental disorder that's typically caused by the incomplete splitting of a single embryo during the formation of identical twins. It results in conjoined twins that share one body but have two fully formed, independent heads.

Zak Mertz, CEO of New England Wildlife Centers, which includes the Cape Wildlife Center, said the recently discovered diamondback terrapin (Malaclemys terrapin) is an uncommon example of bicephaly in turtles. Both genetics and epigenetics ‪—‬ the study of how genes and environment can interact ‪—‬ are thought to play a role in the condition's development.

"Our understanding based on the available research is that bicephaly is caused by both genetic and epigenetic factors," Mertz told Live Science in an email.

"It may have to do with the relatively long lifespan of the turtles, their preference for returning to the same nesting sites, and a limited gene pool due to their conservation status," he said."It may also be influenced by environmental factors, such as the temperature, humidity during incubation, physical characteristics of the nesting sites, or potentially even things the parents are exposed to in the environment."

Having two heads is rare but not unprecedented. According to the center, this is the third bicephalic terrapin found in the area in the past five years, providing another opportunity to learn more about the animals. Other wild animals with bicephaly have been found in recent years, including a two-headed porpoise found off the coast of the Netherlands and a two-headed dolphin that was found on a Turkish beach.

A 2021 study found that rare two-headed and partially duplicated sea turtle embryos and hatchlings showed significant craniofacial and spinal abnormalities and were generally smaller than typical hatchlings. The research found bicephalic turtles faced survival challenges because their abnormal anatomy could impair coordinated movement, feeding, and other functions essential for survival, highlighting the importance of monitoring such deformities as potential indicators of population and environmental health.

Diamondback terrapins are found in brackish marshlands along the Atlantic and Gulf coasts of the United States. Brackish waters have more salt than fresh water but less salt than seawater, and often occur where the freshwater of a lake or river meets the salty sea. These terrapins are classified as threatened by the Massachusetts Endangered Species Act, and their broader conservation status at the federal level is currently under review.

Veterinarians are monitoring the rare terrapin's health closely. "It is fascinating and an area that certainly merits more study," Mertz said. "We are excited to care for these two and learn as much as we can to inform future study in the process."

'> Rare two-headed turtle hatchling discovered on Cape Cod strong El Niño has brought a rare gift to Chile's Atacama Desert: rain. In one of the driest places on Earth, that rare moisture has awakened millions of seeds and bulbs that can remain dormant underground for years, transforming the landscape into a spectacular carpet of color.

Known locally as "desierto florido," or "flowering desert," the phenomenon is one of nature's most remarkable transformations. Patches of purple, pink, white, red and yellow now spread across hillsides and plains that for much of the year appear almost completely lifeless.

"It is a unique phenomenon; there are more than 200 plant species," Jorge Carabantes, head of the Protected Areas Department at the National Forest Corp. (CONAF) in Chile, told The Associated Press. "This is a flowering event that is obviously extraordinary and unusual, very different from other blooms that occur elsewhere on the globe."

Typically, the Atacama gets just 0.6 inches (15 mm) of rain a year. But thanks to the super El Niño, record levels of rain fell between July and August in several Chilean regions, including levels not seen since the 1950s, with some areas receiving more than 7 inches (190 millimeters), Carabantes told the AP.

While this unprecedented precipitation has caused flooding in some areas of Chile, it's created a 6,560-square-mile (17,000 square kilometers) swath of flowering blooms across the Atacama Desert. This is the most extensive desert bloom since 1997, CONAF representatives told the AP.

For photographers and tourists, the landscape is breathtaking, with bright colors contrasted against the dark Atacama mountains and Chile's cloudless skies. But the bloom is fleeting; by the end of the Southern Hemisphere's spring, many of the flowers will disappear, leaving behind seeds and bulbs waiting for the next extraordinary rains.

Here are five photos from Getty Images photographer Javier Torres that showcase the beauty of this rare event.

'> Colorful wildflowers bloom across Chile's Atacama Desert in wake of 'super' El Niño

In the study, published Friday (Oct. 2) in the journal Science Advances, the researchers argue that the absence of animal fossils in some exceptionally well-preserved ancient rocks doesn't mean the animals were absent from history. Instead, they suggest that the fossil record may be missing a key chapter of animal evolution, potentially pushing the origins of animals back to between 800 million and 700 million years ago.

This would place the emergence of animals deep within the Neoproterozoic era (1 billion to 539 million years ago), possibly before or during some of Earth's most extreme ice ages.

Even though scientists haven't found undisputed animal fossils from the Neoproterozoic, that doesn't mean animals didn't live at that time. Fossils can be absent from rocks for several reasons, including because scientists are looking in the wrong places or the conditions were unsuitable for creating fossils, making it difficult to determine the earliest evolved animals.

"Until that evidence becomes available, the precise birth date of the animal kingdom remains uncertain," study co-author Ross Anderson, an associate professor of natural history at the University of Oxford, said in a statement.

Where are the animals?

Until now, most researchers relied on the well-preserved rocks from the Ediacaran period, including the roughly 590 million-year-old Weng'an Biota in China, to investigate the timing of animal evolution. Because rock deposits there contain uniquely preserved microscopic organisms but no definitive animal fossils, experts have sometimes treated them as a kind of upper limit for when animals could have evolved.

"So the game is basically how much does it predate our first fossil discovery by and what happened in that evolutionary black box between when they actually originated versus when we get our first fossil window," Karma Nanglu, an assistant professor of evolutionary paleobiology at the University of California, Riverside who wasn't involved with the study, told Live Science.

But the researchers wondered whether other fossil sites from known animal periods actually had evidence of animal fossils.

To find out, Anderson and his colleagues studied more than 140 samples from the Kheseen Biota in Mongolia, which is more than 40 million years younger than the 590 million-year-old Weng'an Biota deposit. Given that it's a younger deposit, the researchers hypothesized that there should be evidence of animal life left in the rock. Using electron scanning microscopy, the researchers saw microscopic fossils preserved in extraordinary detail, including tiny, spherical organisms and embryo-like structures containing internal cells.

Yet, despite the quality of preservation, the researchers couldn't identify any of the microfossils as animals. That's important, because by the time the Kheseen Biota was deposited, animals were present elsewhere on Earth.

"The Kheseen Biota breaks the argument that the exceptional microfossils of Weng'an mean we would have seen animal fossils in the assemblage had they existed at the time," Anderson said. "The Kheseen microfossils are just as well-preserved, yet animals continue to be absent — despite the fact we know at that point they existed."

Using molecular clocks

Given the absence of fossil evidence, Anderson and his collaborators turned to another common method used to date ancient life: molecular clocks. Molecular clocks estimate when evolutionary lineages diverged by comparing genetic differences among living organisms and combining those differences with rates of genetic change. For example, if two bird species have five DNA changes and one DNA change takes about 1 million years to accumulate, scientists could estimate that the two species diverged around 5 million years ago.

"Molecular clocks are useful when we don't have a particularly good fossil record for a group of interest or a time period of interest," Nanglu said.

When the analysis was constrained by the younger Weng'an deposit, the estimated origin of animals was comparatively recent. When they used older geological constraints — specifically rock formations in Norway, Australia and Arizona deposited between around 850 million and 730 million years ago that have been used in the past for trying to find animals' early ancestors, the timeline changed. By comparing modern animal DNA to reference dates from the fossil record along with evolutionary rates of change — their estimate shifted back by roughly 200 million years, to between about 800 million and 700 million years ago.

"Pre-Ediacaran animal body fossils still elude us, and this analysis does not prove that animals existed 800 million years ago," study first author Orin Lole Durbin, a doctoral student of paleobiology at Virginia Tech who was a University of Oxford undergraduate at the time of the study, said in the statement. "Meanwhile, our molecular-clock analyses show how much further back their evolutionary history could extend."

Could animals have lived before "Snowball Earth"?

There are other clues that animals may have a longer history.

Chemical fossils, or biomarkers, have been interpreted as evidence consistent with sponges living at least 650 million years ago, tens of millions of years prior to the oldest known animal fossils.

If animals did originate 800 million years ago, their emergence would also intersect with the Cryogenian period, which began around 720 million years ago as part of the Neoproterozoic era. During this interval, Earth experienced enormous glaciations often referred to as "Snowball Earth."

Although there is no definitive answer to whether animals survived this uncertain time, the researchers plan to search additional Neoproterozoic rocks with different environments and preservation conditions to find more evidence for their analysis.

"Fossils themselves are by definition kind of hidden from general sight," Nanglu said."Beyond that there's an even more hidden world, and that has a lot of potential to tell us about animal origins."

Think you know about natural selection? Try your hand at our evolution quiz!

'> Animals may have evolved 200 million years earlier than previously thought, new study suggests "super" El Nino means the U.S. will likely face a higher risk of stormy weather and flooding, so experts are recommending Americans stock up on food.

And flooding is just one of the natural disasters people will face — many people are at risk of wildfires, power outages or earthquakes. While some disasters are unexpected, preparation can make a significant difference in how much they impact peoples' daily lives.

But is anyone actually prepared for the worst?

Levels of preparedness vary widely. Some may keep an emergency kit stocked with food, water and first-aid supplies, while others may have an evacuation plan, emergency contacts or designated meeting place for their household. And others do nothing at all. Although a recent study revealed there's no single place on Earth that's best prepared for global disaster, there are steps people can take to feel well equipped.

Experts recommend stocking up on food supplies and other essentials, especially in areas that might be more disaster prone. But how prepared are you? Answer our poll below, and share how you've prepared for emergencies or what you have in your disaster kit in the comments.

'> How prepared are you for a disaster?