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Is the universe infinite?
Determining if the universe is infinite pushes the limits of our knowledge.
- The size and shape of the universe has yet to be resolved.
- The size of the universe is linked to understanding its shape and the limits of our observations.
- New studies and going deeper into space will help us answer the question: "Is the universe infinite?"
Does the universe keep extending endlessly into the abyss of space, or does it have a defined end?
Of all the scientific questions you may ponder, "Is the universe infinite?" is one of the hardest. It is impossible to answer with certainty at this point. Scientists have proposed both possibilities, and each has its own supporters and detractors. Determining whether the universe has some kind of boundary ultimately depends on figuring out its shape, size, and how much of it we can actually observe.
Is the universe infinite? And what shape is it?
The shape of the universe would have a lot to do with its size. Cosmologists have theorized that a universe would likely come in one of three possible shapes, which are dependent on the curvature of space. As described in Discover Magazine, the universe could be flat, having no curvature, but spatially infinite. Or it could be open, shaped like a saddle (with negative curvature) and also infinite. Or it could be closed, look like a sphere, and be spatially finite.
So which shape really is it? Nobel Prize-winning cosmologist John Mather of NASA's Goddard Space Flight Center, also the chief scientist for the James Webb Space Telescope, maintains that recent observations of cosmic microwave background radiation (CMB) remaining from the time of the Big Bang support the idea of the universe being flat, without any curvature (at least to the limit of what is observable).
"The universe is flat like an [endless] sheet of paper," shared Mather. "According to this, you could continue infinitely far in any direction and the universe would be just the same, more or less."
The geometry of the universe is determined by the density parameter Ω within cosmological Friedmann Equations.Credit: NASA / WMAP Science Team
Measuring the size of the universe
Current calculations say that the observable universe extends 46.5 billion light-years in every direction, making its diameter 93 billion light-years across.
Consider this: The age of the universe is 13.8 billion years, which means it took 13.8 billion light-years for the light from the farthest edge of the observable universe to reach us. But in that time, the universe has continued to expand at a rate that appears to be speeding up. Now, the edge of the observable universe has moved and is 46.5 billion light-years away.
These gargantuan numbers are almost impossible to grasp. How did scientists come up with them?
As shared in an interview with BBC by Caitlin Casey, an astronomer at the University of Texas at Austin, scientists use a variety of tools and methods called "the cosmic distance ladder" to estimate distances between objects in the vastness of space. They start out with distances they can actually measure directly, like through bouncing radio waves off nearby bodies in the solar system, noting the time required for the waves to come back to Earth.
For distances that are harder to gauge, like those for galaxies at the boundary of the universe, astronomers utilize inferences based on calculations and observational evidence.
For instance, they employ "parallax measurement" that relies on measuring a star's shift in relation to objects in its background, as well as "main sequence fitting," which takes advantage of our knowledge of stellar evolution. (Stars evolve over time, changing size and brightness.) Knowledge of how brightness is connected to distance is paramount in determining the location of distant objects. So is analysis of redshift, which involves measuring changes in the wavelengths of light coming from faraway galaxies.
What about the unobservable universe?
If you notice, the numbers above pertain to the observable universe, the ball-like part of the universe that can be somehow seen from Earth or detected using our space telescopes and probes. But what about parts of the universe we cannot see? Some portions of the universe may be just too far away for the light emitted after the Big Bang to have had sufficient time to reach us here on Earth.
One study from a group of UK scientists estimated that if you take that into account, the actual size of the universe could be at least 250 times larger. They found that if you refer to space in terms of a so-called Hubble volume, which is similar to the volume of space in the visible universe, a closed and finite universe would contain roughly 250 to 400 Hubble volumes.
Another possibility entertained by scientists like Nobel Prize-winning Roger Penrose is that the Big Bang was just one of the periods of cosmic regeneration that our universe has experienced. There could have been multiple Big Bangs, followed by Big Crunches, periods in which a universe would stop expanding and collapse upon itself.
If all we know about the universe is derived from how it expands after the latest Big Bang, the questions if the universe is infinite or what size it may be are almost moot. As is often the case, more study and confirmation of our theories is needed.
Is there an edge to the universe?
Whether we have a finite universe or an infinite universe like an ever-expanding bubble, does it still have an "edge"? Is there some place you can go and say, "Yep, this is the end of the universe"? The simple answer is likely no.
As explained to LiveScience by Robert McNees, an associate professor of physics at Loyola University Chicago, the universe is isotropic. That means it follows the so-called "cosmological principle" and has the same properties and follows the same laws of physics in all directions.
If that is so, then the universe is much like the surface of a balloon. Imagine being an ant walking along a balloon. You wouldn't know there's an edge to it if you kept walking forward. You'd likely come back to where you started eventually, but the journey around and around could keep going without end.
If someone were to blow more air into the balloon as you keep walking along it, you'd experience some parts of the balloon moving farther away from you. Still, you'd be no closer to finding the balloon's edge.
Much like the ants, we're unlikely to get to the end of the universe. But we may still be able to answer one day "is the universe infinite" or does it have an actual boundary?
Evolution proves to be just about as ingenious as Nikola Tesla
- For the first time, scientists developed 3D scans of shark intestines to learn how they digest what they eat.
- The scans reveal an intestinal structure that looks awfully familiar — it looks like a Tesla valve.
- The structure may allow sharks to better survive long breaks between feasts.
Considering how much sharks are feared by humans, it is a bit of a surprise that scientists don't know much about the predators. For example, until recently, sharks were thought to be solitary creatures searching the seas for food on their own. Now it appears that some sharks are quite social.
Another mystery is how these prehistoric swimming and eating machines digest food. Although scientists have made 2D sketches of captured sharks' digestive systems based on dissections, there is a limit to what can be learned in this way. Professor Adam Summers at University of Washington's Friday Harbor Labs says:
"Intestines are so complex, with so many overlapping layers, that dissection destroys the context and connectivity of the tissue. It would be like trying to understand what was reported in a newspaper by taking scissors to a rolled-up copy. The story just won't hang together."
Summers is co-author of a new study that has produced the first 3D scans of a shark's intestines, which turns out to have a strange, corkscrew structure. What's even more bizarre is that it resembles the amazing one-way valve designed by inventor Nikola Tesla in 1920. The research is published in the journal Proceedings of the Royal Society B.
What a 3D model reveals
Video: Pacific spiny dogfish intestine youtu.be
According to the study's lead author Samantha Leigh, "It's high time that some modern technology was used to look at these really amazing spiral intestines of sharks. We developed a new method to digitally scan these tissues and now can look at the soft tissues in such great detail without having to slice into them."
"CT scanning is one of the only ways to understand the shape of shark intestines in three dimensions," adds Summers. The researchers scanned the intestines of nearly three dozen different shark species.
It is believed that sharks go for extended periods — days or even weeks — between big meals. The scans reveal that food passes slowly through the intestine, affording sharks' digestive system the time to fully extract its nutrient value. The researchers hypothesize that such a slow digestive process may also require less energy.
It could be that this slow digestion is more susceptible to back flow given that the momentum of digested food through the tract must be minimal. Perhaps that is why sharks evolved something so similar to a Tesla valve.
What is Tesla's valve doing there?
Above, a Tesla valve. Below, a shark intestine.Credit: Samantha Leigh / California State University, Domi
Tesla's "valvular conduit," or what the world now calls a "Tesla valve," is a one-way valve with no moving parts. Its brilliance is based in fluid dynamics and only now coming to be fully appreciated. Essentially, a series of teardrop-shaped loops arranged along the length of the valve allow water to flow easily in one direction but not in the other. Modern tests reveal that at low flow rates, water can travel through the valve either way, but at high flow rates, the design kicks in. According to mathematician Leif Ristroph:
"Crucially, this turn-on comes with the generation of turbulent flows in the reverse direction, which 'plug' the pipe with vortices and disrupting currents. Moreover, the turbulence appears at far lower flow rates than have ever previously been observed for pipes of more standard shapes — up to 20 times lower speed than conventional turbulence in a cylindrical pipe or tube. This shows the power it has to control flows, which could be used in many applications."
A deeper dive
Summers suggests the scans are just the beginning. "The vast majority of shark species, and the majority of their physiology, are completely unknown," says Summers, adding that "every single natural history observation, internal visualization, and anatomical investigation shows us things we could not have guessed at."
To this end, the researchers plan to use 3D printing to produce models through which they can observe the behavior of different substances passing through them — after all, sharks typically eat fish, invertebrates, mammals, and seagrass. They also plan to explore with engineers ways in which the shark intestine design could be used industrially, perhaps for the treatment of wastewater or for filtering microplastics.
It could fairly be said, though, that Nikola Tesla was 100 years ahead of them.
The non-contact technique could someday be used to lift much heavier objects — maybe even humans.
- Since the 1980s, researchers have been using sound waves to move matter through a technique called acoustic trapping.
- Acoustic trapping devices move bits of matter by emitting strategically designed sound waves, which interact in such a way that the matter becomes "trapped" in areas of particular velocity and pressure.
- Acoustic and optical trapping devices are already used in various fields, including medicine, nanotechnology, and biological research.
Sound can have powerful effects on matter. After all, sound strikes our world in waves — vibrations of air molecules that bounce off of, get absorbed by, or pass through matter around us. Sound waves from a trained opera singer can shatter a wine glass. From a jet, they can collapse a stone wall. But sound can also be harnessed for delicate interactions with matter.
Since the 1980s, researchers have been using sound to move matter through a phenomenon called acoustic trapping. The method is based on the fact that sound waves produce an acoustic radiation force.
"When an acoustic wave interacts with a particle, it exerts both an oscillatory force and a much smaller steady-state 'radiation' force," wrote the American Physical Society. "This latter force is the one used for trapping and manipulation. Radiation forces are generated by the scattering of a traveling sound wave, or by energy gradients within the sound field."
When tiny particles encounter this radiation, they tend to be drawn toward regions of certain pressure and velocity within the sound field. Researchers can exploit this tendency by engineering sound waves that "trap" — or suspend — tiny particles in the air. Devices that do this are often called "acoustic tweezers."
Building a better tweezer
A study recently published in the Japanese Journal of Applied Physics describes how researchers created a new type of acoustic tweezer that was able to lift a small polystyrene ball into the air.
Tweezers of Sound: Acoustic Manipulation off a Reflective Surface youtu.be
It is not the first example of a successful "acoustic tweezer" device, but the new method is likely the first to overcome a common problem in acoustic trapping: sound waves bouncing off reflective surfaces, which disrupts acoustic traps.
To minimize the problems of reflectivity, the team behind the recent study configured ultrasonic transducers such that the sound waves that they produce overlap in a strategic way that is able to lift a small bit of polystyrene from a reflective surface. By changing how the transducers emit sound waves, the team can move the acoustic trap through space, which moves the bit of matter.
Move, but don't touch
So far, the device is only able to move millimeter-sized pieces of matter with varying degrees of success. "When we move a particle, it sometimes scatters away," the team noted. Still, improved acoustic trapping and other no-contact lifting technologies — like optical tweezers, commonly used in medicine — could prove useful in many future applications, including cell separation, nanotechnologies, and biological research.
Could future acoustic-trapping devices lift large and heavy objects, maybe even humans? It seems possible. In 2018, researchers from the University of Bristol managed to acoustically trap particles whose diameters were larger than the sound wavelength, which was a breakthrough because it surpassed "the classical Rayleigh scattering limit that has previously restricted stable acoustic particle trapping," the researchers wrote in their study.
In other words, the technique — which involved suspending matter in tornado-like acoustic traps — showed that it is possible to scale up acoustic trapping.
"Acoustic tractor beams have huge potential in many applications," Bruce Drinkwater, co-author of the 2018 study, said in a statement. "I'm particularly excited by the idea of contactless production lines where delicate objects are assembled without touching them."
Australian parrots have worked out how to open trash bins, and the trick is spreading across Sydney.
Dumpster-diving trash parrots
In a study about these smart birds just published in Science, researchers define animal culture as "population-specific behaviors acquired via social learning from knowledgeable individuals."
Co-lead author of the study Barbara Klump of the Max Planck Institute of Animal Behavior in Konstanz, Germany says, "[C]ompared to humans, there are few known examples of animals learning from each other. Demonstrating that food scavenging behavior is not due to genetics is a challenge."
An opportunity presented itself in a video that co-author Richard Major of the Australian Museum shared with Klump and the other co-authors. In the video, a sulphur-crested cockatoo used its beak to pull up the handle of a closed garbage bin — using its foot as a wedge — and then walked back the lid sufficiently to flip it open, exposing the bin's edible contents.
Major has been studying Cacatua galerita for 20 years and says, "Like many Australian birds, sulphur-crested cockatoos are loud and aggressive." The study describes them as a "large-brained, long-lived, and highly social parrot." Says Major, "They are also incredibly smart, persistent, and have adapted brilliantly to living with humans."(Research regarding some of the ways in which wild animals adapt to the presence of humans has already produced some fascinating results and is ongoing.)
Clever cockie opens bin - 01 youtu.be
The researchers became curious about how widespread this behavior might be and saw a research opportunity. After all, says John Martin, a researcher at Taronga Conservation Society, "Australian garbage bins have a uniform design across the country, and sulphur-crested cockatoos are common across the entire east coast."
Martin continues, "In 2018, we launched an online survey in various areas across Sydney and Australia with questions such as, 'What area are you from, have you seen this behavior before, and if so, when?'"
Word Gets Around
Credit: magspace/Adobe Stock
Although the cockatoos' maneuver was reported in only three suburbs before 2018, by the end of 2019, people in 44 areas reported observing the behavior. Clearly, more and more cockatoos were learning how to successfully dumpster dive.
As further proof, says Klump, "We observed that the birds do not open the garbage bins in the same way, but rather used different opening techniques in different suburbs, suggesting that the behavior is learned by observing others." One individual bird in north Sydney invented its own method, and the scientists saw it grow in popularity throughout the local population.
To track individual birds, the researchers marked 500 cockatoos with small red dots. Subsequent observations revealed that not all cockatoos are bin-openers. Only about 10 percent of them are, and they are mostly males. The other cockatoos apparently restrict their education to a different lesson: hang around with a bin-opener, and you will get supper.
Thanks to the surveys, the researchers consider the entire project to be a valuable citizen-science experiment. "By studying this behavior with the help of local residents, we are uncovering the unique and complex cultures of their neighborhood birds."
The few seconds of nuclear explosion opening shots in Godzilla alone required more than 6.5 times the entire budget of the monster movie they ended up in.