1. What is the speed limit of human beings?
Jamaican aviator Bolt broke the 100-meter world record and won the gold medal at the 2009 World Championships in Berlin, increasing his own world record by 0. 1 1 sec. What is the speed limit of human beings? Mark Denny of Stanford University in the United States was very curious about this question and decided to make an in-depth study on how fast humans can run 100 meters.
By analyzing the world records of various track and field competitions (even horse racing) since 1920, he found that the results of many competitions followed a similar law, that is, the results gradually improved until they were stable. For example, in the Kentucky Derby, it is difficult for many horses to break through after 1949 reached the speed limit. Human athletes seem to follow this pattern. The women's 100 meter performance tends to be stable at 1977, and the men's sprint performance is still improving, but Danny said that this performance seems to be reaching its limit based on the models established in other events.
According to his prediction, the limit of men's 100-meter performance is 9.48 seconds, which is only 0. 1 second less than Bolt's current world record. Danny said: "If we continue to maintain the current momentum, Bolt will soon be close to this limit." What caused this human speed limit? Danny thinks the reason is similar to the strength-to-weight ratio of athletes. Beyond a certain point, the advantages of stronger muscles and longer limbs will be offset by the increased energy consumption of lifting heavier objects.
2. How long can human attention last?
How long can human attention last?
When we finish our papers before the deadline, work overtime until late at night and drive long distances, concentration is a challenge for most of us. How long should I persist psychologically before my brain needs a rest? For those who need to concentrate on a certain job, such as truck drivers, power plant operators and flight drivers, 12 hours is a limit. However, for doctors, complicated operations sometimes exceed 12 hours, although the longest operation is often shared by multiple teams.
Before 2004, British doctors in weekend classes had to work 80 hours from Friday morning to Sunday night. They can only sleep for a few hours at most, and in the worst case, they haven't slept for 80 hours. According to Helen Fernandez, a neurosurgeon at Aidan Brooks Hospital in Cambridge, England, "You may be working most of the time."
As time goes on, our attention will also decline. This leads to lower work efficiency, longer decision-making time and more mistakes. David Dinges, a neuroscientist at the University of Pennsylvania, said: "Being alert is one of the easiest aspects of fatigue." Dinges's team used magnetic resonance imaging to study the brains of highly alert workers. As people become unresponsive, the activity of some parts of the brain will decrease. Dinges found that participants' performance in the test could be predicted according to their blood flow in the right frontal parietal bone.
3. How long can people live in a vacuum?
How long can people live in a vacuum?
Unfortunately, we do know how long people can live when suddenly exposed to a vacuum. 197 1 year, just before the Soviet spacecraft 1 1 re-entered the earth's atmosphere, a faulty valve suddenly depressurized the spacecraft at the altitude of 168 km, resulting in the death of all three astronauts on board. After investigation, it was found that the pressure of Soyuz spacecraft 1 1 suddenly dropped to zero and lasted for 1 1 min for 40 seconds until it re-entered the atmosphere.
The astronaut died after 30 to 40 seconds due to lack of oxygen. Jonathan Clark, a former crew member of NASA's space shuttle mission, said, "You need oxygen and air pressure to transport oxygen to your brain." However, if you spend less time in a vacuum, you may be saved. 1966, a technician from NASA was testing the spacesuit in the vacuum chamber when the indoor air pressure suddenly dropped to the level we encountered at an altitude of 36,500 meters. He lost consciousness within 12 to 15 seconds.
The last thing he can remember is that the saliva on his tongue evaporated, because water will evaporate at low pressure. Within 27 seconds, the pressure in the vacuum chamber returned to the level equivalent to 4200 meters, and the technician was lucky to regain consciousness. Although he looks pale, his health has not been adversely affected.
When the external pressure drops, bubbles will form in the blood, and the lungs will be damaged within a few minutes. Because nitrogen is dissolved from the blood, the nervous system will be damaged within a few hours. The sudden drop in pressure is fatal to the human body: the air seeping into the lungs will explode in a few seconds. However, according to Clark, if we enter the near vacuum state in a more appropriate way and have a dense medical monitoring service team around us, we may survive for one minute at most.
4. How many things can humans remember?
How many things can humans remember?
Most of us have a hard time remembering the telephone number of 1 1 digit, but the current world memory champion, Lv Chao of China, can recite the pi of 67,890 digits in 2005. Is this really just a drop in the ocean compared with the real ability of the brain?
Our ability to receive information is quite strong. Thomas Randall worked in Bell Communication Research Company in Morristown, New Jersey from 65438 to 0986. He studied how much visual and verbal information people can store when they look at pictures and information, and how quickly they forget. After research, he estimated that adults can store about 125M of this information in their lifetime, which is equivalent to 100 Mobidick.
It is more difficult to remember a long list of numbers accurately in the right order than to remember short messages or pictures. In order to explore the limits of memory length, it may be helpful to consider the skills used by memory champions. Many of them use mnemonics. Before they begin to memorize numbers, they will associate every four-digit number from 0000 to 9999 with people or things. Thus, the number of pi is transformed into a sequence of these people or things, which are connected by fabricating a story. This can also enhance the interest of unordered numbers and consolidate memory. It took Lu Chao about 65,438+0,000 hours to remember the 40,000 digits of pi. No matter how good the memory is, if a person spends 12 hours a day from the age of 20, he will be able to recite about 8.76 million words by his 70th birthday.
5. How low temperature can humans tolerate?
How low temperature can humans tolerate?
There is a reason why human beings are afraid of cold: our limbs are long, it is easy to dissipate heat, and it is difficult to preserve heat. Slender limbs are of great significance in the hot African prairie where human beings first evolved. Mike Tipton, who studies human thermoregulation at Portsmouth University, points out that we can still live without the means to keep out the cold-clothes, heating and houses.
Living in the cold is to protect the core body temperature. People's core body temperature is 37 degrees Celsius, but the speed of its decline is surprising. Flores Harman, a physiologist at the University of Ottawa in Canada, said that if the weather is humid and windy, the ambient temperature of 20 degrees Celsius will lead to hypothermia. When it is cold, the body begins to tremble and blood stops flowing to the limbs. Hypothermia will occur as long as the core body temperature drops by 2 degrees: first, people begin to lose consciousness, and then their heart rate will drop. At about 24 degrees, the heart will stop beating and people will die. However, some people can survive with a significant drop in core body temperature. Anna Ba Gen's family is such a person. Her temperature dropped to 13.7 degrees Celsius, and she is still alive. At that time, she accidentally fell into a cold stream and was trapped for 80 minutes before being rescued.
The flowing ice water cooled her body to such a temperature that her breathing stopped and her heart stopped, and her brain basically didn't need oxygen, giving her a chance to recover completely.
6. How long can you live without eating or drinking?
How long can you live without eating or drinking?
How long can humans live without water and food? Theoretically, if you finally run out of fat, protein and carbohydrates, your body will stop working because of energy exhaustion. Jeremy Powell Teck, a nutrition guidance doctor who resumed eating after david brian's hunger strike in London in 2003, believes that human death does not need to wait until the energy is completely exhausted: "You may die before that." If there are enough water-soluble B vitamins in the body to help store fat metabolism, fat people may live longer. Therefore, it is entirely possible for people to have fat in their bodies when they starve to death.
The longest record of not eating was Kieran Doherty, an Irish hunger strike protester in 198 1 year, who died after 73 days of hunger strike. With vitamins and water supplements, people can live for a year without eating. Powell Teke said: "About 30 years ago, this was a very popular way to lose weight.
With vitamins and without water, the survival time will be greatly shortened. A person can live for several weeks without food, but a thirsty and dehydrated person can only live for a few days. "It depends on the rate of water loss," said Michael Savaka of the US Army Institute of Environmental Medicine in Massachusetts. Without water, the blood volume in the body will decrease and blood pressure will also drop. Blood becomes more and more viscous, blood circulation in the body becomes more and more difficult, and people's heart rate will increase to compensate. Even in a cold environment, without water, people can only persist for about a week.
7. How long can humans last without sleep?
How long can humans last without sleep?
1On February 28th, 963, Randy Gardner, a 0/7-year-old student in San Diego, California, got up at 6 am. He felt full of energy and didn't sleep again until1June 8, 964, which means 1 1 day. After Gardner broke the previous record of 260 hours of sleepless, his record of 264 hours is still the longest sleepless time verified by science. William Dement, a researcher at Stanford University School of Medicine in California, told this story in a paper at 1965. He spent the last three days with Gardner.
Gardner experienced mood swings, memory and attention problems, lack of coordination, slurred speech and hallucinations, but he was otherwise normal. One day after 1 1, his first sleep only lasted 14 hours. According to Dement, Gardner did not take stimulants during this sleepless period. But someone was with him to keep him awake. If there is no help from others, you must try to restrain yourself from going to sleep after 36 hours, and you will feel irresistible to sleep after 48 hours.
However, before you finally go to bed, you may have had several "micro-sensations": people who lack sleep will fall into "micro-sensations" from time to time-when you are distracted, you will fall asleep within a few seconds, during which you often keep your eyes open. How long can Gardner last, regardless of mini-sleep? No one knows this problem, but we know that lack of sleep will eventually lead to death. If rats are forced to stay awake for two weeks, they will die, which is shorter than the time they need to starve to death.
There is no record that a person deliberately stays awake until death, but a genetic disease called fatal familial insomnia shows that human beings have a maximum time without sleep. The disease finally deprived patients of their sleep ability and caused them to die within three months.
8. How much gravity acceleration can ordinary people bear?
How much acceleration of gravity can ordinary people bear?
When the roller coaster swoops down, we will bear the acceleration of 5g gravity in a short time, and then we will feel dizzy and sick. These seats must be specially designed so that people will not faint. Our ability to withstand gravitational acceleration depends not only on the change and duration of acceleration or deceleration, but also on the direction of our body. We are most sensitive to the external force applied in the direction of our feet, because it makes blood flow to our brains. When the body is in a vertical state for 5 to 10 seconds in an environment of 4 to 5g, it often causes tubular vision and then loses consciousness.
The gravity acceleration of the fighter plane in the vertical state can reach 9g. The stronger the pilot's tolerance to this environment, the better it is for air combat. Some pilots wear "gravity acceleration suits" to prevent the blood in their legs from rushing to their heads. The person who has the strongest ability to bear gravity is called "monster G". Alec Stevenson, a biologist at Qinetiq, a British-based defense company, said, "Some of us can really stay awake in a 6g environment." Others will pass out in the 3g environment.
Pilots can improve their natural tolerance to gravity by training in centrifuges. Qinetiq has such a centrifuge in Farnborough, Hampshire, England. They learn to tighten leg and abdominal muscles, promote blood flow to the upper body, and lower blood pressure through special breathing methods. The maximum gravity that a person can bear is 3 1.25g, but in order to achieve this goal, a doctor from NASA, Flanagan Gray, entered a special water tank, which exerted pressure on his body and helped him to bear such a large gravity acceleration. John stapp, the pioneer of American Air Force, holds the highest record of horizontal gravity acceleration.
9. How high can humans climb?
How high can humans climb?
The difference in altitude will have a strange effect on the human body. In most cases, the oxygen pressure in the air at high altitude will decrease. Human cells need oxygen to survive. At higher altitudes, hemoglobin, the blood protein that transports oxygen from the lungs to cells, cannot effectively transport oxygen, leading to hypoxia in the human body. The brain is very sensitive to oxygen level, which is also the first reaction of altitude sickness and the cause of headache and dizziness. McGlocott of the University of Southampton in the United Kingdom said that if people stay at an altitude of more than 5,000 meters for a long time, the risk of muscle atrophy and lung and hydrocephalus will increase significantly, but they may not be able to give birth there because high altitude temporarily inhibits male fertility. Glocott studied the effect of altitude difference on physiology.
If people live in this environment for a long time, most people will eventually adapt. A good experience is that the higher you climb, the shorter your stay. If you are suddenly sent to Mount Everest (8,848 meters) before adapting to the new environment, you may die within 2 minutes. Only a few people climb Mount Everest without oxygen supplement. 1999, the Sherpas of Babu Chiri lived in the anoxic environment of Mount Everest for 2 1 hour, breaking the world record. Glocott said, maybe ChirishSherpa people are born with the ability to adapt to high altitude environment. How high can humans live? Maybe Everest is close to this height. Glocott said that so far, only one person has climbed Mount Everest without an oxygen device in winter, when the atmospheric pressure dropped even lower and there was less oxygen in the air. "I think the highest altitude that humans can bear may be 9000 meters."
10. How much weight can humans lift at most?
How much weight can humans lift at most?
The world weightlifting record was set by British weightlifter Andy Bolton. He lifted the weight of 457.5 kilograms from the ground to his thigh. Dan Wasser, a sports coach at Youngstown State University in Ohio, said that a strongman like Bolton may be five or six times stronger than ordinary people, and it is already difficult for ordinary people to lift 45 kilograms above their heads. The overhead weightlifting record is 263.5 kg.
What is the maximum weight that humans can lift? Todd Skorod of the University of Southern California in Los Angeles believes that we are close to the limit we can reach. He said: "Looking back at the previous weightlifting records, you will find that although the performance has been continuously improved, it has begun to reach a stable level. Today's weightlifters, including those who take steroids, are close to the limits of human physical fitness. "
How much weight you can finally lift depends on your muscles. In weightlifting competition, most failed attempts will not harm the body, because weightlifters choose to give up because they can't bear the weight they want. But if you try hard, failure will often lead to tearing of muscle fibers, usually fibers near tendons.
It can effectively control muscles and give weightlifters an advantage. The human body has a natural inhibition mechanism to protect the body from being overweight. This work is achieved by controlling the number of muscle fibers involved in weightlifting at one time. Weightlifters are trained to know how to suppress these signals and then exert their muscle potential to a greater extent. Besides this control, another key factor of success is training. Of course, genetic factors also play an important role. Washer used to be a weightlifter. He said: "People with short limbs have greater strength, and some people have more muscle fibers than others."
1 1. How much radiation can the human body bear at most?
How much radiation can the human body bear at most?
1987 In September, two men walked into an abandoned clinic in Iania, Brazil, and removed a piece of equipment that they thought was very valuable. Within one day, both of them had vomiting symptoms, followed by diarrhea and dizziness. As everyone knows, this abandoned equipment is actually a high radiation source, which is used to treat cancer patients.
This radiation source can emit blue light in the dark. Deval Ferrara, a scrap dealer, became interested in it and finally bought it. Ferreira put a cup-sized jar containing powdered substances in the restaurant and invited friends and relatives to visit. They powdered themselves and turned themselves into luminous people. But what they never expected was that this magical powder turned out to be radioactive cesium chloride. Within a month, Ferreira's wife, 6-year-old niece and 2 employees all died of acute radiation syndrome. In this accident, a total of 249 people were polluted by this radioactive substance.
The unit of radiation dose is sievert, which is calculated according to the type of radiation and the body part to be irradiated. The calculation results show that the radiation dose received by all the deceased in a few days is 4.5 to 6 sieverts. The average annual radiation dose from natural radiation sources such as radon is 2.4 millisieverts. In other words, 4.5 to 6 sieverts is already a considerable dose.
Radiation dose of about 2 sieverts can lead to premature death, and 6 sieverts is likely to lead to death. Fortunately, Ferreira survived despite being exposed to 7 sieverts of radiation. From 65438 to 0994, he died of alcoholic cirrhosis. No one knows exactly why Ferrara survived such a high dose of radiation. The most likely explanation is that he and his wife spend most of their time outdoors, giving cells in the body time to repair some damage.
12. How long can humans hold their breath?
Most people find it difficult to hold their breath for more than a minute. In contrast, the Frenchman Stefan Mifusu has super self-control. On June 8, 2009, Mifsu made a feat, holding his breath for 1 1 min 35 seconds, setting a new world record for holding his breath still.
In the challenge, the contestants soaked their faces in a cold pool. This is not to prevent them from cheating, but to stimulate the instinctive diving of mammals. When the face is soaked in cold water, the external blood vessels contract and blood flows from the limbs to the heart and brain. This will slow down the heart rate and reduce the chance of oxygen spreading to the whole body. After training, the heart rate of breath-holding masters when immersed in cold water is only half that of non-divers.
It is also very important to breathe hard before challenging the time record of holding your breath. This is because the brain monitors the carbon dioxide content in the blood and determines when to trigger the respiratory reflex. Take a deep breath quickly to expel carbon dioxide from the body, and then hold your breath as long as possible before reaching your physical limit. Therefore, having a bigger lung is a natural advantage.
Has man reached the limit of holding his breath? John Anderson, a physiologist at Lund University in Sweden, gave a negative answer. The physiologist, who has been studying the effects of breath holding, said: "Before the breath holding record becomes stable, excellent divers are expected to extend the breath holding time to about 15 minutes."
But they may also be in danger in the process of holding their breath for a long time. Anderson found that static breath holding on land can increase the content of S 100B protein in blood by 37%, which is a sign of hypoxic brain damage. He said that although this increase is far below the level of hypoxia, the damage suffered by people who challenge static breath holding may accumulate for a long time.