1. What is the limit of human speed?
Jamaica Bolt broke the world 100-meter record at the 2009 World Championships in Berlin and won the gold, improving the world record held by himself by another 0.11 seconds. What is the limit of human speed? Stanford University's Mark Denny (Mark Denny) is very curious about this issue, and decided to conduct an in-depth investigation of how fast the human 100 meters.
He analyzed the world records of various track and field competitions (including even horse races) since 1920, and found that the results of many competitions follow a similar pattern, i.e., the results are gradually improved until stabilized. At the Kentucky Jockey Club, for example, many of the horses that competed in the race reached their speed limits in 1949 and then struggled to break through. Human athletes appear to follow the same pattern. Women's 100-meter times stabilized in 1977, and men's sprinting times are still improving, although Danny said that based on models developed for other races, it looks like that performance is approaching its limit as well.
Based on his projections, the limit for the men's 100 meters is 9.48 seconds, just 0.1 seconds less than Bolt's current world record. Danny said, "If the current momentum continues, Bolt will soon be close to that limit." What is the cause of this human speed limit? Danny believes the reason is similar to an athlete's strength-to-weight ratio. Beyond a certain point, the advantages of stronger muscles and longer limbs are offset by the increased energy expenditure of lifting heavier weights.
2. How long does the human attention span last?
How long does the human attention span last?
Focus is the challenge most of us face when we meet deadlines for papers, work late into the night, and drive long distances. How long do we actually hold on mentally before our brains need a break? For those who need to give their full attention to a job, such as truck drivers, power plant operators, and flight pilots, 12 hours is the limit. But for doctors, complex surgical procedures can sometimes exceed 12 hours, although the longest procedures are often shared by more than one team.
Before 2004, British doctors working weekend shifts were expected to work from Friday morning until Sunday night, a total of 80 hours***. At best, they could only sleep for a few hours, and in the worst cases, they didn't even close their eyes for 80 hours. As Helen Fernandes, a neurosurgeon at Addenbrookes Hospital in Cambridge, England, recalls, "You were probably working the vast majority of the time."
Over time, our attention spans follow suit. As a result, productivity is lower, decision-making takes longer, and mistakes begin to mount. David Dinges, a neuroscientist at the University of Pennsylvania in the US, says: "Alertness is one of the aspects that makes people most susceptible to fatigue." Dinges' research team studied the brains of workers engaged in very high levels of alertness using MR*** vibration imaging. As people became less responsive, activity in certain parts of the brain decreased. Dingus found that participants' performance on the test could be predicted based on their blood flow to the right frontoparietal bone.
3. How long can a person live in a vacuum?
How long can a person live in a vacuum?
Unfortunately, we do know how long a person can live when suddenly exposed to a vacuum. in 1971, a faulty valve in the Soviet Union's Soyuz 11 spacecraft suddenly depressurized the craft at an altitude of 168 kilometers just before re-entry into the Earth's atmosphere, killing all three cosmonauts on board. An investigation later found that the Soyuz 11's pressure suddenly dropped to zero, which continued for 11 minutes and 40 seconds until it re-entered the atmosphere.
The astronauts died after 30 to 40 seconds due to lack of oxygen. Jonathan Clark, a former crew member on NASA's space shuttle mission, said, "You need both oxygen and air pressure to get oxygen to the brain." However, it is possible to be resuscitated if you are in a vacuum for a much shorter period of time.In 1966, a NASA technician was testing space suits in a vacuum chamber when the pressure in the chamber suddenly dropped to levels we only encounter at 36,500 meters. He lost consciousness for 12 to 15 seconds.
The last thing he remembers is that the saliva on his tongue vaporized because water evaporates at low pressure. 27 seconds later, the pressure in the vacuum chamber returned to the equivalent of 4,200 meters, and the technician was lucky to regain consciousness. Although pale, he suffered no adverse health effects.
When the external pressure drops, bubbles form in the blood and the lungs are damaged within minutes. The nervous system is damaged within hours as nitrogen dissolves from the blood. Pressure dips are fatal to the body: air seeping into the lungs explodes within seconds. But, according to Clarke, it's possible we could survive for up to a minute if we enter a near-vacuum in a more appropriate manner and are surrounded by a team of enhanced medical monitoring services.
4. How much can humans actually remember?
How much can humans actually remember?
Memorizing 11-digit phone numbers is hard enough for most of us, but the current world memory champion, China's Lu Chao, was able to recite 67,890 digits of pi in 2005. Is this really just a drop in the ocean compared to what the brain is really capable of?
Our ability to take in information is quite powerful, and in 1986 Thomas Randall, who worked for Bell Communications Research in Morristown, N.J., studied how much visual and verbal information people could store when they looked at pictures and messages, and how quickly they could forget them. As a result of his research, he estimates that adults can store about 125M of this information over a lifetime, the equivalent of 100 copies of Moby Dick.
It's harder to memorize a long string of numbers in the right order and accurately than it is to memorize text messages or pictures. To explore the limits of memory length, it may be helpful to consider the techniques used by memory champions. Many of them use one method of memorization. Before they start memorizing numbers, they associate each four-digit number from 0000 to 9999 with a person or object. The round numbers are then transformed into a sequence of these people or objects, and the people or objects are made to connect by making up a story. This also enhances the fun of the unordered numbers, and it reinforces the memory. It took Lu Chao about 1,000 hours to memorize 40,000 digits of pi. Regardless of how good the memory is, assuming that at this rate, a person who starts pi at age 20 and spends 12 hours a day would be able to memorize about 8,760,000 digits by his 70th birthday.
5. How low a temperature can humans tolerate?
How low can humans tolerate?
Humans hate the cold for a reason: we have long limbs, which tend to dissipate heat extremely easily and do not retain it easily. In the scorching African savannahs, where humans first evolved, long limbs were of great importance. Mike Tipton of the University of Portsmouth in the UK, who studies human thermoregulation, points out that all of us can still live without the means to protect ourselves from the cold - clothing, heaters and houses.
Surviving the cold requires protecting core body temperature. A person's core body temperature is 37 degrees Celsius, but it drops at a surprising rate. Fran Oschmann, a physiologist at the University of Ottawa in Canada, said an ambient temperature of 20 degrees Celsius can cause hypothermia if it's wet and windy. When it's cold, the body starts to shiver and blood stops flowing to the extremities. Hypothermia occurs as soon as the core body temperature drops by 2 degrees: first people start to lose consciousness, then their heart rate loses. At about 24 degrees the heart stops beating and the person dies. But some people can survive a significant drop in core body temperature. Anna Bagenholm is one such person, who once survived a drop in body temperature to 13.7 degrees Celsius when she fell into an icy stream and was trapped for 80 minutes before being rescued.
The flowing icy water chilled her body to this one temperature: breathing stopped, her heart stopped, and her brain essentially didn't need oxygen, which gave her a chance for a full recovery.
6. How long can you live without eating or drinking?
How long can you live without eating or drinking?
How long can humans survive without water and food? Theoretically, if you end up running out of body fat, protein and carbohydrates, your body will stop working due to energy depletion.According to Jeremy Powell Teck, the doctor who guided David Bryan's nutrition when he resumed eating after his hunger strike performance in London in 2003, human beings don't need to wait for their energy to be completely depleted to die: "You could be dead before then. " Fat people may live longer if they have enough water-soluble B vitamins in their bodies to help metabolize reserve fat. So it's perfectly fine for people to starve to death with fat still in their bodies.
The record holder for the longest period without food was Irish hunger striker Kieran Dougherty, who died after 73 days of hunger strike in 1981. With vitamin and water supplements, people can live without food for a year. Powell Teck said, "It was a very popular way to lose weight about 30 years ago."
Survival time is much shorter with only vitamins and no water. A person can live for weeks without food, but a thirsty, dehydrated person can last only a few days. Michael Savaca of the U.S. Army Research Institute of Environmental Medicine in Massachusetts says, "It depends on the rate of water loss." Without water, the amount of blood in the body decreases and so does blood pressure. The blood becomes thicker, making it harder to circulate through the body, and people's heart rates increase to compensate. Even in the cold, without water, people can only last about a week.
7. How long can humans last without sleep?
How long can humans last without sleep?
On December 28, 1963, Randy Gardner, a 17-year-old school student in San Diego, California, woke up at 6 a.m. feeling full of energy, and continued to do so until January 8, 1964, when he went back to sleep, meaning that he hadn't slept for 11 days. After Gardner broke his previous record of 260 hours of sleeplessness, his record of 264 hours remains to this day the longest scientifically verified period of sleeplessness. William DeMent, a researcher at the Stanford University School of Medicine in California who told the story in a 1965 paper, stayed with Gardner for the last three days he remained awake.
Gardner experienced mood swings, memory and attention problems, lack of coordination, slurred speech and hallucinations, though he was otherwise normal. After this 11-day period, his first sensation lasted only 14 hours. According to Dement, Gardner was not doping during this period of sustained sleeplessness. But someone did stay with him to keep him awake. Without the help of others, you'd have to try to restrain yourself from going to sleep after 36 hours, and after 48 hours you'd find it impossible to resist the urge to sleep.
But before you finally go to bed, you'll probably have taken a few "mini-sleeps": People who lack sleep will slip into "mini-sleeps" from time to time-when you're not paying attention, you'll be asleep for a few seconds. When you're not paying attention, you'll fall asleep in a matter of seconds, often with your eyes open. How long did Gardner last, micro-sleeps aside? That's a question no one knows, but it's clear to us that sleep deprivation eventually leads to death. Force rats to go without sleep for two weeks and they die, which is less time than it takes them to starve to death.
There are no records of a person who intentionally stayed awake until they died, but a genetic disease known as lethal familial insomnia suggests that there is a maximum amount of time that humans can go without sleep. The disease eventually robs sufferers of their ability to sleep, killing them within three months.
8. How much acceleration of gravity can the average person withstand?
How much gravitational acceleration can the average person withstand?
When a roller coaster dives, we are subjected to 5g of gravity for a very short period of time, which can cause dizziness and nausea. The seats have to be specially designed so that people don't pass out. Our ability to withstand gravitational acceleration depends not only on the change and duration of acceleration or deceleration, but also on the orientation of our body. We are most sensitive to external forces applied in the direction of our feet, as this causes blood to flow to the brain. Having the body in a vertical position for 5 to 10 seconds at 4 to 5 g often causes tube vision and then unconsciousness.
Fighter jets can experience gravity accelerations of up to 9g in a vertical position, and the more a pilot can withstand this environment, the better it is for air combat. Some pilots wear "gravity suits," which prevent blood from rushing from the legs to the head. Those with the greatest ability to withstand gravity are called "monster g's". Alec Stevenson, a biologist at the U.K.-based defense company Qinetiq, says, "Some of us do manage to stay awake at 6g." Others pass out at 3g.
Pilots can improve their natural tolerance to gravity by training in a centrifuge, which Qinetiq has in Farnborough, Hampshire, England. They learn to tighten their leg and abdominal muscles to encourage blood flow to the upper body and lower blood pressure through special breathing methods. The maximum gravity that people can withstand is 31.25g, but to achieve this, NASA doctor Flanagan Gray went into a special tank that put pressure on his body to help him withstand that much gravitational acceleration. U.S. Air Force pioneer John Stapp holds the record for the highest horizontal gravity acceleration.
9. How high can humans go?
How high can humans go?
Differences in altitude can have strange effects on the human body, and in most cases the pressure of oxygen in the air is reduced at higher altitudes. Human cells need oxygen to survive. At higher altitudes, hemoglobin, the blood protein that carries oxygen from the lungs to the cells, is not able to transport oxygen efficiently, which leads to a lack of oxygen in the body. The brain is very sensitive to oxygen levels, which is why the first reaction to altitude sickness is a headache and dizziness. Mike Grocott of the University of Southampton in the United Kingdom says that people who spend long periods of time at altitudes of more than 5,000 meters lead to a significantly increased risk of muscle atrophy and fluid buildup in the lungs and brain, although they may not be able to have children there because the high altitude temporarily inhibits male fertility. Glocott studied the physiological effects of altitude differences.
If people live in such environments for a long time, most eventually adapt. A good lesson is that the higher you climb, the shorter you should stay. If you were suddenly sent up Everest (8848 meters) without acclimatizing to your new environment, you would probably be dead in less than 2 minutes. Only a handful of people have climbed Everest without supplemental oxygen, and in 1999, Babu Chiri Sherpa broke the world record by living in an oxygen-deprived environment on Everest for 21 hours. Grocott suggests that perhaps the Chili Sherpa was born with the ability to adapt to high altitude environments. What is the highest height at which humans can survive? Maybe Mount Everest is close to that height. Grocott said only one person to date has climbed Everest without an oxygen device in the winter, when atmospheric pressure drops even lower and there is less oxygen in the air. "I think the highest altitude that humans can withstand is probably 9,000 meters."
10.What is the most weight humans can lift?
How much weight can humans lift at most?
The world record for the hard lift was set by British weightlifter Andy Bolton. He lifted 457.5 kilograms from the ground to his thigh area. Dan Wasser, a sports coach at Youngstown State University in Ohio, said that the strength of a Hercules man like Bolton could be five or six times that of an ordinary person, and that an ordinary person would have struggled to lift 45 kilograms of weight over his head. The record for the overhead lift is 263.5 kilograms.
What is the maximum weight a human can lift? Todd Skrode, of the University of Southern California in Los Angeles, believes we are close to the limit. He says: "When you look back at past weightlifting records, you will see that while the results have continued to improve, they have begun to reach a level of stability. Today's lifters, including those on steroids, are approaching the limits of human fitness."
How much weight you can ultimately lift depends on the muscles. The vast majority of failed attempts at weightlifting competitions don't leave the body suffering because the lifter chooses to give up because he or she can't handle the desired weight. But if the attempt is forced, failure often results in tears in muscle fibers, usually those near the tendons.
The ability to effectively control muscles gives weightlifters an advantage. The body has a natural inhibitory mechanism that protects it from damage caused by lifting too much weight. This is accomplished by controlling the number of muscle fibers involved in a lift. Weightlifters are trained to inhibit these signals, thereby maximizing the potential of their muscles. In addition to this control, another key factor in success is training. And, of course, genetics play an important role. Vasser is a former weightlifter. He says, "People with short limbs have more strength, and some have more muscle fibers than others."
11. How much radiation can the human body withstand at most?
How much radiation can the human body withstand at most?
In September 1987, two men walked into an abandoned medical clinic in Goiania, Brazil, and dismantled a piece of equipment they thought was very valuable. Within a day, both men experienced vomiting, followed by diarrhea and vertigo. Little did they know that the discarded equipment was actually a source of high radiation used to treat cancer patients.
The source was capable of emitting a blue light in the dark. Scrap dealer Deval Ferreira became intrigued by it and eventually paid for it. Ferrera placed the cup-sized jar containing the powdered substance in his dining room and invited close friends and relatives to visit. They applied the powder to their bodies and transformed themselves into glowing people. But what they never expected was that the magical powder was actually the radioactive substance cesium chloride. Within a month, Ferrera's wife, 6-year-old niece, and 2 employees died of acute radiation syndrome. In total **** 249 people were contaminated with this radioactive substance in this accident.
The radiation dose is measured in sieverts and is calculated according to the type of radiation and the part of the body exposed. Calculations show that all of the dead received a radiation dose of between 4.5 and 6 sieverts over a period of several days. The average annual radiation dose we receive from natural sources of radiation such as radon is 2.4 millisieverts. That means that 4.5 to 6 sieverts is already a fairly large dose.
A radiation dose of around 2 sieverts can lead to premature death, and 6 sieverts is likely to be fatal. Fortunately, Ferrera survived despite being exposed to 7 sieverts, and in 1994 he died of alcoholic cirrhosis of the liver. No one knows exactly how Ferrera survived such a high dose of radiation. One of the most likely explanations is that he and his wife spent most of their time outdoors, giving the cells in his body time to repair some of the damage.
12. How long is the longest a human can keep his or her breath closed?
In contrast to the vast majority of people, who can barely hold their breath for more than a minute, Frenchman Stéphane Mifosu possesses exceptional self-control. on June 8, 2009, Mifosu performed a feat that saw him hold his breath for 11 minutes and 35 seconds, setting a new world record for static breath-holding.
During the challenge, participants submerge their faces in a pool of ice-cold water. This is done not to prevent them from cheating, but to provoke the mammal's instinctive dive launch. When immersing the face in cold water, external blood vessels constrict and blood flows from the ends of the limbs to the heart and brain. This slows the heart rate thereby reducing the chances of oxygen diffusing throughout the body. With training, a master shutterbug's heart rate while immersed in cold water is half that of a non-diver.
It's also important to breathe strongly before setting a record for closed-breath time. That's because the brain monitors the level of carbon dioxide in the bloodstream and decides when to trigger the breathing reflex. Breathing quickly and y removes the carbon dioxide from the body, maximizing the amount of time you can hold your breath before you reach your limit. So having larger lungs is a natural advantage.
Have humans reached the limit of breath closure? Johan Andersson, a physiologist at Lund University in Sweden, gives a negative answer. The physiologist, who has been conducting research on the effects of breath closure in divers, said, "Until the record for breath closure stabilizes, excellent divers can expect to extend their closure time to about 15 minutes."
But they can also be at risk during prolonged breath closure. Anderson found that static breath closure on dry land resulted in a 37 percent increase in blood levels of the S100B protein, a marker for hypoxic brain damage. He says that while this increase is much lower than the levels found in hypoxia, the damage suffered by people challenged with static breath-holding may be building up over the long term.