How do we know the sun is a star?
Today, it's common knowledge, but it took scientists centuries to figure out.
Adam Frank is a professor of astrophysics at the University of Rochester and a leading expert on the final stages of evolution for stars like the sun. Frank's computational research group at the University of Rochester has developed advanced supercomputer tools for studying how stars form and how they die. A self-described “evangelist of science," he is the author of four books and the co-founder of 13.8, where he explores the beauty and power of science in culture with physicist Marcelo Gleiser.
- The simplest questions are often the hardest to answer.
- At first blush, the sun and stars are very different. The former is close and hot, the latter far away and cold.
- We couldn't confirm the sun to be a star until telescopes and spectroscopes were invented.
Sometimes, as a scientist, you forget how much you take for granted about the amazingness of the universe. The other day, my colleagues and I traded stories about how non-scientist friends would often ask us questions that we don't even realize are questions. One of my compatriots related how a friend had been completely amazed that the sun was just another star. I really loved that story because, when you think about it, humans have only figured out what stars are — and that the sun is a star — very recently in our 300,000-year history.
So let's step back and ask that basic question: How do we know the sun is a star?
Of course, the sun is a light in the sky, and stars are lights in the sky. But for someone starting from scratch, they might seem really different. The sun is only "up" in the day, but the stars are only up in the night. The sun can be so hot that it literally burns your skin. Stars, on the other hand, give off no warmth at all. How did astronomers see that the sun and the stars were beasts of the same feather?
One key point was understanding that their energy output per time (what astronomers call luminosity) is similar. If stars look dim while the sun appears blinding, it's just because the sun is much closer. The luminosity of an object can be found by knowing how bright it appears to be and its distance. That means once you know the distance to an object, you can calculate its luminosity. The problem, then, of determining if the sun and stars had similar luminosities really came down to figuring out their distances. Clever people as far back as the ancient Greeks started estimating how far away the sun was, but distance measurements to the stars took humanity a lot longer.
The problem of parallax
Credit: JustinWick via Wikimedia Commons
The problem for the stars was the method required for calculating distances. The easiest way is what's called parallax, which relies on how a distant object shifts its position relative to a nearby object when you, the observer, shift position. You can see the effect by putting your finger up against your nose, looking at a picture on a wall, and then closing one eye and then the other. The position of your finger relative to the picture on the wall jumps back and forth as you do this.
But here's the catch. The farther away the picture on the wall, the smaller the shift in its position. Since stars are so far away, astronomers had to wait until they had reasonably powerful telescopes before they could get accurate parallax measurements and, hence, accurate distances. Once these were determined, they found that, yes, the sun and the stars pump out comparable amounts of energy every second.
It's worth noting that big stars can be millions of times brighter than small stars, but for our purposes here, what matters is that astronomers were able to determine that stars and the sun were in the same category of "luminous stuff."
We are all star stuff
The next big step in showing that the sun was a star was to show that both were basically made of the same stuff. People had long imagined the sun to be made of burning stuff for obvious reasons, but what kind of stuff? Was it wood, candle wax, or coal? And what about the stars that seemed to burn so less intensely?
The barcode of the sun.Credit: NOAO / AURA / NSF
The answer to this question came with the invention of spectroscopy, which involves sending sunlight or starlight through a prism to break it up into its component colors (like a rainbow). When astronomers did this with powerful enough spectrographs, they saw that the rainbow was not complete. There were dark bands or missing colors as if something had eaten the light at specific wavelengths. The dark lines were not random but appeared in specific patterns. Remarkably, physicists soon found that these patterns of dark lines were like the fingerprints of specific elements (such as hydrogen, helium, nitrogen, and oxygen) in the gas that the light passed through on the way to the spectrograph.
The dark lines, therefore, seen in light from the sun or distant stars were giving astronomers an inventory of their composition. It was telling them what the sun and stars were made of. Lo and behold, the patterns of dark lines for both were basically the same. The stars were made of the same stuff as the sun, and the sun was made of the same stuff as the stars!
This discovery was the true game changer. With spectroscopy, astronomy became astrophysics, and soon a true science of stars began. In the decades that followed, astronomers would unpack the secrets of the inner architecture of stars, as well as the nuclear energy source that powers their titanic engines.
Through all these steps, the sun was finally recognized as just another star in the late 19th or early 20th century. It was our parent ball of nuclear fusion — neither different nor unusual compared to other stars, but, to us, very special.
That's as fast as a bullet train in Japan.
The way an elephant manipulates its trunk to eat and drink could lead to better robots, researchers say.
Elephants dilate their nostrils to create more space in their trunks, allowing them to store up to 5.5 liters (1.45 gallons) of water, according to their new study.
They can also suck up three liters (0.79 gallons) per second—a speed 30 times faster than a human sneeze (150 meters per second/330 mph), the researchers found.
The researchers wanted to better understand the physics of how elephants use their trunks to move and manipulate air, water, food, and other objects. They also wanted to learn if the mechanics could inspire the creation of more efficient robots that use air motion to hold and move things.
Photo by David Clode on Unsplash
While octopuses use jets of water to propel themselves and archer fish shoot water above the surface to catch insects, elephants are the only animals able to use suction both on land and underwater.
"An elephant eats about 400 pounds of food a day, but very little is known about how they use their trunks to pick up lightweight food and water for 18 hours, every day," says lead author Andrew Schulz, a mechanical engineering PhD student at the Georgia Institute of Technology. "It turns out their trunks act like suitcases, capable of expanding when necessary."
Sucking up tortilla chips without breaking them
Schulz and his colleagues worked with veterinarians at Zoo Atlanta, studying elephants as they ate various foods. For large rutabaga cubes, for example, the animal grabbed and collected them. It sucked up smaller cubes and made a loud vacuuming sound, like the sound of a person slurping noodles, before transferring the vegetables to its mouth.
To learn more about suction, the researchers gave elephants a tortilla chip and measured the applied force. Sometimes the animal pressed down on the chip and breathed in, suspending the chip on the tip of its trunk without breaking it, similar to a person inhaling a piece of paper onto their mouth. Other times the elephant applied suction from a distance, drawing the chip to the edge of its trunk.
Elephants inhale at speeds comparable to Japan's 300 mph bullet trains.
"An elephant uses its trunk like a Swiss Army knife," says David Hu, Schulz's advisor and a professor in Georgia Tech's School of Mechanical Engineering. "It can detect scents and grab things. Other times it blows objects away like a leaf blower or sniffs them in like a vacuum."
By watching elephants inhale liquid from an aquarium, the team was able to time the durations and measure volume. In just 1.5 seconds, the trunk sucked up 3.7 liters (just shy of 1 gallon), the equivalent of 20 toilets flushing simultaneously.
Soft robots and elephant conservation
The researchers used an ultrasonic probe to take trunk wall measurements and see how the trunk's inner muscles work. By contracting those muscles, the animal dilates its nostrils up to 30%. This decreases the thickness of the walls and expands nasal volume by 64%.
"At first it didn't make sense: an elephant's nasal passage is relatively small and it was inhaling more water than it should," Schulz says. "It wasn't until we saw the ultrasonographic images and watched the nostrils expand that we realized how they did it. Air makes the walls open, and the animal can store far more water than we originally estimated."
Based on the pressures applied, Schulz and the team suggest that elephants inhale at speeds comparable to Japan's 300-mph bullet trains.
"By investigating the mechanics and physics behind trunk muscle movements, we can apply the physical mechanisms—combinations of suction and grasping—to find new ways to build robots," Schulz says.
"In the meantime, the African elephant is now listed as endangered because of poaching and loss of habitat. Its trunk makes it a unique species to study. By learning more about them, we can learn how to better conserve elephants in the wild."
The paper appears in the Journal of the Royal Society Interface. The US Army Research Laboratory and the US Army Research Oﬃce 294 Mechanical Sciences Division, Complex Dynamics and Systems Program, funded the work. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the view of the sponsoring agency.
Source: Georgia Tech
Original Study DOI: 10.1098/rsif.2021.0215
The experience of life flashing before one's eyes has been reported for well over a century, but where's the science behind it?
At the age of 16, when Tony Kofi was an apprentice builder living in Nottingham, he fell from the third story of a building. Time seemed to slow down massively, and he saw a complex series of images flash before his eyes.
As he described it, “In my mind's eye I saw many, many things: children that I hadn't even had yet, friends that I had never seen but are now my friends. The thing that really stuck in my mind was playing an instrument". Then Tony landed on his head and lost consciousness.
When he came to at the hospital, he felt like a different person and didn't want to return to his previous life. Over the following weeks, the images kept flashing back into his mind. He felt that he was “being shown something" and that the images represented his future.
Later, Tony saw a picture of a saxophone and recognized it as the instrument he'd seen himself playing. He used his compensation money from the accident to buy one. Now, Tony Kofi is one of the UK's most successful jazz musicians, having won the BBC Jazz awards twice, in 2005 and 2008.
Though Tony's belief that he saw into his future is uncommon, it's by no means uncommon for people to report witnessing multiple scenes from their past during split-second emergency situations. After all, this is where the phrase “my life flashed before my eyes" comes from.
But what explains this phenomenon? Psychologists have proposed a number of explanations, but I'd argue the key to understanding Tony's experience lies in a different interpretation of time itself.
When life flashes before our eyes
The experience of life flashing before one's eyes has been reported for well over a century. In 1892, a Swiss geologist named Albert Heim fell from a precipice while mountain climbing. In his account of the fall, he wrote is was “as if on a distant stage, my whole past life [was] playing itself out in numerous scenes".
More recently, in July 2005, a young woman called Gill Hicks was sitting near one of the bombs that exploded on the London Underground. In the minutes after the accident, she hovered on the brink of death where, as she describes it: “my life was flashing before my eyes, flickering through every scene, every happy and sad moment, everything I have ever done, said, experienced".
In some cases, people don't see a review of their whole lives, but a series of past experiences and events that have special significance to them.
Explaining life reviews
Perhaps surprisingly, given how common it is, the “life review experience" has been studied very little. A handful of theories have been put forward, but they're understandably tentative and rather vague.
For example, a group of Israeli researchers suggested in 2017 that our life events may exist as a continuum in our minds, and may come to the forefront in extreme conditions of psychological and physiological stress.
Another theory is that, when we're close to death, our memories suddenly “unload" themselves, like the contents of a skip being dumped. This could be related to “cortical disinhibition" – a breaking down of the normal regulatory processes of the brain – in highly stressful or dangerous situations, causing a “cascade" of mental impressions.
But the life review is usually reported as a serene and ordered experience, completely unlike the kind of chaotic cascade of experiences associated with cortical disinhibition. And none of these theories explain how it's possible for such a vast amount of information – in many cases, all the events of a person's life – to manifest themselves in a period of a few seconds, and often far less.
Thinking in 'spatial' time
An alternative explanation is to think of time in a “spatial" sense. Our commonsense view of time is as an arrow that moves from the past through the present towards the future, in which we only have direct access to the present. But modern physics has cast doubt on this simple linear view of time.
Indeed, since Einstein's theory of relativity, some physicists have adopted a “spatial" view of time. They argue we live in a static “block universe" in which time is spread out in a kind of panorama where the past, the present and the future co-exist simultaneously.
The modern physicist Carlo Rovelli – author of the best-selling The Order of Time – also holds the view that linear time doesn't exist as a universal fact. This idea reflects the view of the philosopher Immanuel Kant, who argued that time is not an objectively real phenomenon, but a construct of the human mind.
This could explain why some people are able to review the events of their whole lives in an instant. A good deal of previous research – including my own – has suggested that our normal perception of time is simply a product of our normal state of consciousness.
In many altered states of consciousness, time slows down so dramatically that seconds seem to stretch out into minutes. This is a common feature of emergency situations, as well as states of deep meditation, experiences on psychedelic drugs and when athletes are “in the zone".
The limits of understanding
But what about Tony Kofi's apparent visions of his future? Did he really glimpse scenes from his future life? Did he see himself playing the saxophone because somehow his future as a musician was already established?
There are obviously some mundane interpretations of Tony's experience. Perhaps, for instance, he became a saxophone player simply because he saw himself playing it in his vision. But I don't think it's impossible that Tony did glimpse future events.
If time really does exist in a spatial sense – and if it's true that time is a construct of the human mind – then perhaps in some way future events may already be present, just as past events are still present.
Admittedly, this is very difficult to make sense of. But why should everything make sense to us? As I have suggested in a recent book, there must be some aspects of reality that are beyond our comprehension. After all, we're just animals, with a limited awareness of reality. And perhaps more than any other phenomenon, this is especially true of time.
Might as well face it, you're addicted to love.
- Many writers have commented on the addictive qualities of love. Science agrees.
- The reward system of the brain reacts similarly to both love and drugs
- Someday, it might be possible to treat "love addiction."
Since people started writing, they've written about love. The oldest love poem known dates back to the 21st century BCE. For most of that time, writers also apparently have been of two (or more) minds about it, announcing that love can be painful, impossible to quit, or even addictive — while also mentioning how nice it is.
The idea of love as an addiction is one that is both familiar and unsettling. Surely it can't be the case that our mutual love with our partner — a thing that can produce euphoria, consumes a great deal of our time, and which we fear losing — can be compared to a drug habit? But indeed, many scientists have turned their attention to the idea of "love addiction" and how your brain on drugs might resemble your brain in love.
Love and other drugs
In a 2017 article published in the journal Philosophy, Psychiatry, & Psychology, a team of neuroethicists considered the idea that love is addicting and held the idea up to science for scrutiny.
They point out that the leading model of addiction rests on the notion of a drug causing the brain to release an unnatural level of reward chemicals, such as dopamine, effectively hijacking the brain's reward system. This phenomenon isn't strictly limited to drugs, though they are more effective at this process than other things. Rats can get a similar rush from sugar as from cocaine, and they can have terrible withdrawal symptoms when the sugar crash kicks in.
On the structural level, there is a fair amount of overlap between the parts of the brain that handle love and pair-bonding and the parts that deal with addiction and reward processing. When inside an MRI machine and asked to think about the person they love romantically, the reward centers of people's brains light up like Broadway.
Love as an addiction
These facts lead the authors to consider two ideas, dubbed the "narrow" and "broad" views of love as an addiction.
The narrow view holds that addiction is the result of abnormal brain processes that simply don't exist in non-addicts. Under this paradigm, "food-seeking or love-seeking behaviors are not truly the result of addiction, no matter how addiction-like they may outwardly appear." It could be that abnormal processes cause the brain's reward system to misfire when exposed to love and to react to it excessively.
If this model is accurate, love addiction would be a rare thing — one study puts it around five to ten percent of the population — but could be considered a disorder similar to others and caused by faulty wiring in the brain. As with other addictions, this malfunction of the reward system could lead to an inability to fully live a typical life, difficulty having healthy relationships, and a number of other negative consequences.
The broad view looks at addiction differently, perhaps even radically.
It begins with the idea that addiction exists on a spectrum of motivations. All of our appetites, including those for food and water, exist on this spectrum and activate similar parts of the brain when satisfied. We can have appetites for anything that taps into our reward system, including food, gambling, sex, drugs, and love. For most people most of the time, our appetites are fairly temperate, if recurring. I might be slightly "addicted" to food — I do need some a few times per day — but that "addiction" doesn't have any negative effects on my health.
An appetite for cocaine, however, is rarely temperate and usually dangerous. Likewise, a person's appetite for love could reach addiction levels, and a person could be considered "hooked" on relationships (or on a particular person). This would put love addiction at the extreme end of the spectrum.
None of this is to say that the authors think that love is bad for you just because it can resemble an addiction. Love addiction is not the same as cocaine addiction at the neurological level: important differences, like how long it takes for the desire for another "hit" to occur, do exist. Rather, the authors see this as an opportunity to reconsider our approach to addiction in general and to think about how we can help the heartsick when they just can't seem to get over their last relationship.
Is "love addiction" a treatable disorder?
Hypothetically, a neurological basis for an addiction to love could point toward interventions that "correct" for it. If the narrow view of addiction is accurate, perhaps some people will be able to seek treatment for love addiction in the same way that others seek help to quit smoking. If the broad view of addiction is correct, the treatment of love addiction would be unlikely as it may be difficult to properly identify where the cutoff of acceptability on a spectrum should be.
Either way, since love is generally held in high regard by all cultures and doesn't quite seem to be in the same category as a bad cocaine habit in terms of social undesirability, the authors doubt we'll be treating anyone for "love addiction" anytime soon.
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