1. What is the limit of human speed?
Bolt, who broke the world's 100-meter record at the Berlin World Championships, added 0.11 seconds to his own world record. What is the limit of human speed? Stanford University's Mark Denny (Mark Denny) is very curious about this issue, decided to human 100 meters of speed in-depth inquiry into how fast.
He went through the world records of various track and field competitions (including even horse races) and found that the results of many competitions follow a similar pattern, i.e., the results gradually improve until they stabilize. In the Kentucky Race, for example, many of the horses in the race had difficulty breaking through after reaching their speed limits in years. Human athletes appear to follow the same pattern. The women's 100-meter times stabilized over the years, and the men's sprint times are still improving, but Danny said that based on models developed for other races, that performance looks to be 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 motorists, 12 hours is the limit. But for that matter, complex surgical procedures can sometimes exceed 12 hours, although the longest procedures are often shared by more than one team.
Years ago, weekend shifts in the UK would run from Friday morning until Sunday night, totaling **** 80 hours of work. At best, they got a few hours' sleep, and in the worst cases, they didn't even close their eyes for 80 hours. As Helen Fernandes, a neurosurgeon at Addenbrookes 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 survive sudden exposure to a vacuum. In 2007, moments before re-entry into the Earth's atmosphere, a faulty valve on the Soviet Union's Soyuz 11 spacecraft suddenly depressurized the craft at an altitude of kilometers, killing all three cosmonauts on board. An investigation later found that the pressure of the Soyuz 11 spacecraft suddenly dropped to zero, which continued for 11 minutes and 40 seconds until it re-entered the atmosphere.
The astronauts were dead after 30 to 40 seconds due to lack of oxygen. Jonathan Clark, a former crew member on NASA's airplane missions, 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 2007, 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 within 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 a level equivalent to that of a meter in the air, 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 can be damaged within minutes. The nervous system is damaged within hours as nitrogen dissolves from the blood. Pressure dips can be fatal to the body: the air that seeps into the lungs does so within seconds. But, according to Clark, we could potentially survive for up to a minute if we enter a near-vacuum in a more appropriate manner and are surrounded by a team of intensive monitoring services.
4. How much can humans actually remember?
How much can humans actually remember?
Memorizing an 11-digit code is hard enough for most of us, but the current world memory champion, China's Lu Chao-nian, can recite the pi digit. Is this really nothing more than a drop in the ocean compared to what the brain is really capable of?
Our ability to take in information is quite powerful. Thomas Randall, who worked at Bell Communications Research in Morristown, N.J., in 2007, studied how much visual and verbal information people can store when they look at pictures and messages and how quickly they forget. As a result of his research, he estimated that adults can store about M of this information over a lifetime, the equivalent of a copy of Moby Dick.
It's harder to memorize a long string of numbers in the right order and accurately than it is to memorize 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 a method of memorization. Before they start memorizing numbers, they associate each four-digit number from to with a person or object. The rounded numbers are then transformed into a sequence of these people or objects, by making up a story to get the people or objects up. This also enhances the fun of the unordered numbers, and it reinforces the memory. It took Lu Chao about hours to memorize the digit 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 10,000 bits by his 70th birthday.
5. How low a temperature can a human being be subjected to?
How low can humans be subjected to?
Humans hate the cold for a reason: we have long limbs, which tend to dissipate heat extremely easily and do not conserve 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 subs.
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. Jeremy Powell, nutritional guide to David Bryan when he resumed eating after his hunger strike performance in London in 2007, argues that humans don't need to wait for their energy to run out completely to die: "You could be dead before that." 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 is Kieran Dougherty, an Irish hunger striker who died after 73 days on hunger strike. With vitamin and water supplements, people can live without food for a year. Powell Teck says, "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 Dec. 28, 2012, Randy Gardner, a 17-year-old school student in San Diego, California, woke up at 6 a.m. feeling refreshed, and continued to do so until Jan. 8, 2012, when he went back to sleep, meaning that he hadn't slept in 11 days. After Gardner broke his previous record of hours of sleeplessness, the hour record he set is still the longest scientifically verified length of time without sleep. William DeMent, a researcher at the Stanford University School of Medicine in California, who told the story in a paper in 2007, 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 did not take it during this period of sustained sleeplessness. But someone did stay with him to keep him awake. Without help, you have to try to restrain yourself from going to sleep after 36 hours, and after 48 hours you feel unable 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 up to 9g of gravity in the 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 ineti, 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 ineti has in Farnborough, Hampshire, England. They learn to tighten their legs 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's 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; 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 meters above sea level are at 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 (meters) without acclimatizing to your new environment, you would probably be dead in less than 2 minutes. Only a few people have climbed Everest without supplemental oxygen. In 2007, 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 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 .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, who would have struggled to lift 45 kilograms of weight over his head. The record for the overhead lift is .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, thereby utilizing their muscles to a greater extent. In addition to this control, another key factor in success is training. And, of course, genetics play an important role. Wasser 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 of 2007, 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 suffered vomiting, followed by diarrhea and vertigo. Little did they know that the discarded device was actually a source of high radiation used to treat cancer patients.
This source of radiation is capable of emitting in the dark. Scrap dealer Deval Ferreira took a keen interest in it and ended up spending money down the line. Ferrera placed the cup-sized jar containing the powdered substance in the 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 **** 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 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, despite the 7 sieverts of radiation, Ferreira survived. In 2007, 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 hardly hold their breath for more than a minute, Frenchman Stéphane Mifsou has remarkable self-control. On June 8, 2008, Mifosu set a new world record for static breath-holding by performing a feat that lasted 11 minutes and 35 seconds.
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 their breath-holding limit? 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 can lead to a 37 percent increase in blood levels of SB protein, a marker for hypoxic brain damage. He said that while this increase was much lower than levels found in hypoxia, the damage suffered by people challenged with static breathing may be building up.