Is there any evidence that time can move backwards?

Is there any evidence that time can move backwards?

That is a fascinating question. Time is one of the most mysterious and intriguing concepts in physics, and there are different ways to approach it. One way is to ask whether the laws of physics allow for the possibility of time moving backwards, or reversing its direction. Another way is to ask whether there is any empirical evidence of time moving backwards, or behaving differently from our usual experience.

From the first perspective, most of the laws of physics, like gravity and quantum mechanics, are symmetric with respect to time. That means that it doesn’t matter whether time moves forward or backward, the equations that describe the physical phenomena work the same. However, there is one law that breaks this symmetry, and that is the second law of thermodynamics. This law states that in any isolated system, such as the universe, entropy (or disorder) has to increase, or at least stay the same. This implies a direction of time, from low entropy to high entropy, or from order to chaos. This is why we see things like eggs breaking, ice melting, and stars dying, but not the other way around. This is also why we remember the past, but not the future. The second law of thermodynamics is often used to explain the arrow of time, or why time seems to only move in one direction.

However, some physicists have challenged this view, and proposed that the second law of thermodynamics is not a fundamental law, but a statistical one. That means that it is not impossible, but just extremely improbable, for entropy to decrease in a system. In other words, there is a tiny chance that time could move backward, or reverse its direction, in some isolated regions of the universe, or under some special conditions. For example, some physicists have suggested that at the moment of the Big Bang, when the universe was in a state of very low entropy, it could have given rise to two universes, one moving forward in time, and one moving backward in time. These two universes would be mirror images of each other, and would have opposite physical charges and parity. This idea is based on a mathematical solution to the equations of general relativity, called the Janus solution.

From the second perspective, there is no conclusive evidence of time moving backwards, or behaving differently from our usual experience, in the observable universe. However, there are some intriguing experiments and observations that suggest that time is not as simple or linear as we think. For example, some physicists have claimed to find evidence of a parallel universe, where time runs backward, by detecting anomalous particles that appear to come from the Earth’s surface, instead of from outer space. These particles are called tau neutrinos, and they are the antiparticles of electrons. They are produced by high-energy cosmic rays hitting the Earth’s atmosphere, and they usually travel downward, not upward. The physicists used a balloon-borne instrument called ANITA, which stands for Antarctic Impulsive Transient Antenna, to detect these particles over Antarctica. They speculated that these particles could be coming from a parallel universe, where time runs backward, and where the Big Bang happened at the same time as ours, but in the opposite direction.

Another example is an experiment conducted by physicists at the Technical University of Darmstadt, who claimed to find evidence of time being reversible in glass. They used ultra-sensitive video cameras to record the minute fluctuations of molecules in glass and plastic, and found that these fluctuations were time-reversible when viewed in terms of material time, an internal clock within the material that ticks at a rate independent of our conventional timekeeping. They argued that this shows that the molecular movements in disordered materials like glass and plastic are not locked on a path towards equilibrium, but can vary as particles push and pull one another into new arrangements. They also suggested that this phenomenon could be used to measure the age of materials, by comparing their material time with our conventional time.

These experiments and observations are very intriguing, but they are also very controversial, and have not been widely accepted or replicated by the scientific community. They could be explained by other factors, such as errors, noise, or alternative interpretations. Therefore, they do not constitute conclusive evidence of time moving backwards, or behaving differently from our usual experience. However, they do show that time is a very complex and fascinating concept, and that there is still much to learn and discover about it.

21 st Century Learning Assessment: Open-book Exams

 21 st Century Learning Assessment: Open-book Exams 

Teachers don't teach; they share! 

Over the past several years, many teachers have consistently regarded the concept of teaching as a unilateral transfer of knowledge with sporadic assessments (tests, exams) to determine the extent of learning that has taken place in the student. Often, these assessments would be memory-testing-based formats given as short-answer or long-answer questions, or variants. To be relevant in the 21st century, I promote the concept of teaching as the "sharing" of information where both the teacher and student learn together, sharing what they know about the subject. This way, when the student makes the effort to source new information via newspaper reading or the internet, they are excited to share it with their teacher and classmates. This form of learning actively helps update both the teacher's and student's knowledge, in addition to using such information in project work assignments. I would also like to see the nature of learning assessments change to include more application-based ideas and hypotheses that will drive research to help overcome problems in the living environment. The use of recall-based formats may be limited to Class 4; a mix of such questions with application-based questions may be used from Class 5 through 9; and application-based questions with research synthesis and evaluation-based questions may be given to students in Class 10–12. 

Using the Open-book Exam System 

The present closed-book type of student learning assessment at the school and college level has outlived its usefulness in the 21st century. With an ever-widening base of information in every area of human knowledge and an examination system that is orbiting itself in memory-based testing, the closed-book form of learning assessment is as antique as space. For example, as an adult in the workplace, when you are faced with a problem and are unable to solve it, do you give up? Does your supervisor stop you from communicating with your peers to discuss a solution? I don't think so. Rather, don't you seek the help of someone knowledgeable in the problem area? You sure will do that. However, why is our educational examination system promoting a practice where you are prevented from corresponding with information sources? Whereas in reality, in the workplace, you are free to refer to books, manuals, and information directories in the library or consult specialists. In essence, the principle is to work in cooperation with the understanding that we all need each other's brainpower if we are to resolve problems in the workplace or personal life. With this brief illustration, I believe it is best to change the learning assessment systems, particularly from LKG through college, to include open-book and take-home types. The advantages are several, ranging from virtually eliminating the scourge of copying to ensuring that students will find learning meaningful when they learn how to source information in their quest to apply learned knowledge to resolve problems that are posed as assessment questions. High school and college teachers will need to attend professional development workshops that focus on the design, use, and evaluation techniques of questions that can be used in open-book and take-home-type examinations. Parents who are employed in industries or professional areas that constantly utilise advanced concepts relating to the subjects students study in high school and college need to be involved in such workshops. Such professionals will be able to share their experiential knowledge of real-life problems in the workplace that require them to constantly use their subject-matter knowledge in practice. Giving students a choice of such learning assessment systems also lessens examination tension, especially since each student has a different learning style and performs better in a specific learning assessment system that suits their learning style. 

Erasing exam tension  

I believe the following seven significant and effective tips will potentially help ease students' exam tension, regardless of which of the above three assessment types are used to evaluate their learning. To ensure instructional and learning excellence, the teacher must: (a) know the subject material and also constantly demonstrate grasp of current knowledge; (b) use simple and advanced instructional technology, including the overhead projector and internet: (c) read, write, and speak English as faultlessly as possible; (d) present the learning matter in an organised and comprehensible manner; (e) ensure that simple activities are used to help reinforce the concepts and keep students actively involved with the lesson; (f) genuinely show that they care for their successful learning; and. (g) work with each student, expressing that they believe in their potential to be successful. 

Role of Parents 

The role of parents in the student's success is equally vital. I have come across a number of parents who spare no efforts to ensure that their children secure admission into a school or college. And, after this, they sit back and hardly make any periodic visits with the teacher until a problem arises or the school celebrates sports day or some occasion in which their children are participating. Parents need to take two actions towards ensuring their children's successful learning: (a) visit with the teacher at least once a month and ask them for suggestions on how best, as parents, they can use strategies that ensure their children's success; and (b) ensure that the suggested strategies are implemented with seriousness and follow-up feedback to the teacher is done regularly. 

Physics in shuttle badminton

 

Physics in  Shuttle Badminton 

History: The game has derived its present name from a place in Gloucestershire, England, where it was played in a party hosted by the Duke of Beau-fort, in 1873. Badminton was the name of the Duke's mansion. In the USA, it started in 1878 in a club inNew York City. International Badminton Federation (IBF) was formed in 1934 with just nine member countries (England, Canada, Denmark, France, New Zealand, Netherlands, Ireland, Scotland, and Wales). Today, IBF has 142 members.

Famous Shuttle Badminton tournaments : [1] Thomas Cup for men [2] Uber Cup for women [3] Sudirman Cup for mixed doubles [4] World Championship [5] World Juniors [6] World Grand Prix [7] World Cup. In 1992's Olympics the game earned a medal game status in Barcelona, Spain.

The Game: This indoor game is played on non-slippery 44 ft by 20 ft color court. This court is divided by a 5 ft - high net into two parts; each of 22 ft by 20 ft. The cock has 16 feathers. It weighs about 4.74 gm to 5.50 gm. The racket weighs 3.5 ounces.

Rules: The goal is to drop the shuttlecock in the opponent's court before the opponent does so. The shuttle should pass over the net and fall within the opponent's court boundary. To begin the game, a player serves in an underarm fashion as per the rule and wins if he is successful in dropping the shuttle 15 times for men's and 11 times for women's tournament. If the opponent is able to do the same, service is treated as broken without conceding any points and the opponent becomes the server. Generally, three games are played in a match and a high level of skill is needed to win.

Skill: In a good match where the speed of shuttle-cock could be beyond 200 miles per hour, the response time is in milliseconds, and more than 90° in body-direction may be needed. A crisp, devastating drop and accurate rallies are the crux of the game.

A focused mental alertness, concentration, thinking power, conviviality and fighting spirit along with suppleness, agility, stamina, strength, fitness and coordination characterize the dedicated player.

Training: The players are trained through jogging, running, skipping, shadow drills, net practice, drop-lift game and so on. Where in lawn tennis, you need to be a good sideways running player, badminton adds frequent front and back movements, making this game more challenging. The speed of a shuttle is faster than the speed of the ball in any comparable game like lawn tennis or volleyball where the fastest stroke will look like a slow motion movie if the camera movement is adjusted to capture the shuttlecock.

Mathematical considerations player's movements:

Three Mathematical considerations are needed in order to reach a shuttle placed by the opponent.

1. Equal time to reach all around the court. 2. Striking the shuttle 3. Recovery of body - balance for next follow-up move. A proper mathematical treatment can be given to these considerations.

1. Equal time to reach all around the court: The players generally fix an anchor position in order to move all around the court. After every hit, the tendency to return to this fixed position becomes a mental commitment. Had the speed of human beings been equal in all directions, this anchor point would have been the geometric center of the court, from where all the corners lie at a distance of around 14 feet. However, reaching any shuttle near the backside of the court away from the net needs more travel time. In addition, the backward speed of human beings is almost half of their forward speed, and reach at the backside is always restricted compared to reach at the front. All these factors put together need selection of anchor points at a distance slightly behind the geometric center, preferably at the right hand side, if the racket is held in the left hand. In fact, total time for reaching shuttle can be divided into three micro motion reaction time of 50 ms, movement time depending on distance, and a recovery time of around 200 ms.

A normal healthy human being can run at a speed of 6 feet per second for a short time only, which can be taken as his forward speed. The shuttle-cock can be assumed to travel at a nominal speed of 150 feet per second. When a player hits the shuttle, it takes 200 ms to the opponent's court, traveling an average distance of 30 ft. But the reaction time reduces the time available for movement to 150 ms, resulting in RESTRICTING THE AVERAGE TRAVEL DISTANCE TO 9 FT ONLY. This shortens the required time for the player to do a complete court coverage. Here, agility, swiftness, anticipation and similar skills become important to be successful in this fast-moving game.

2 Striking the shuttle: In general, winning a game depends on how fast, how accurate, how cleverly, and how deftly the shuttle is hit. All always loves rally. If shuttle trajectory in a medium, free from gravity and air resistance is considered, straight line joining the end of the court with the top of the net needs player's reach to be 10 ft at the end of other court and, that, too, at some angle of the racket, precisely 12.8 degrees from vertical. However, these two factors reduce the height barrier for the players, and also, a straight vertical racket can meet the requirements.

For simulating shuttle trajectory, major variables include location of player, height of shuttle-racket collision and angle of collision. One major factor is drag coefficient, which simulates the effect of air resistance over shuttle trajectory. In general, reduction in acceleration is proportional to the square of velocity. And, constant of proportionality is termed here as drag coefficient, which assumes a value of 0.025 for floaters or service.

However, for smashes or high velocity practices, the value is much reduced (0.001). For short double serve, requirements include clearing the net and fall of shuttle just near the short service line, lying at a distance of 6 ft 6 inches from the net on either side. This needs low velocity (26 ft/s) and high angle of impact (50 degrees) for a player serving from very near to his short service line 15 ft from end at a height of impact of 2 ft. If angle of impact is raised for the same velocity the shuttle will not clear the net. If simultaneous rise in shuttle velocity is considered, the fall of the shuttle will be far off from the near service line giving enough time for the opponent to reach the shuttle. However, in flick serve, the velocity is raised further to materialize a height of around 10 ft near the opponent's short service line so that the opponent is deceived to catch the shuttle at a low height and hits it in a floater rather than a high velocity smash. In singles, long high service is preferred, where the shuttle has to fall almost vertically near the end of the It needs high velocity of the opponent's court. impact (80ft/s) at a low impact angle (37 degrees).

Smashes: The velocity of a smash is of order 300 ft/s. The impact angle of the racket starts at zero from vertical to a maximum 20 degrees. It is these types of smashes that give points and need to be perfected. If the shuttle is attempted at 2 ft from the back of the court, a very small angle of impact is available for proper landing of the shuttle in the opponent's court. This type of smash enhances dwell time available for the opponent to react. However, if the player striking the shuttle is near the net the shuttle reaches faster to the opponent, and available angle of impact is enhanced and fall of shuttle a has larger available area. If the shuttle is hit from near the service line at a height of 10 ft, maximum available angle can go as high as 137 degrees with a fall of shuttle in straight line, reaching almost the entire court with duration point of impact with racket and ground reducing to less than 100 ms. Definitely this type of shot is preferred. A simulated trajectory for smash (300 ft/s) from a 10 ft distance from backline at a height of 10 ft shows an available angle for judgment of the player to only 4 degrees (106 to 110 degrees).

3. Recovery time: Movement to the anchor position to be covered during the flight time of the shuttle to the opponent is around 300 ms on an average. However, body balance and action need proper coordination to overcome these split millisecond phenomena. Proper stretching is always implemented for covering forward movement from the anchor position, and center of gravity of the body for any net play must liè at the back of the body to augment backward motion during recovery phase. Similarly, for reaching a shuttle placed at the back of the court, full body has to be brought behind the shuttle so that recovery starts with hitting action. This adds some extra distance to be covered during the shuttle-reach phase. Recovery phase becomes very important for negotiating the next shot from the opponent. Returning to anchor position before the shuttle reaches the opponent is a major challenge during this phase of the play.

Conclusion: With more and more sophisticated techniques being adopted for perfecting the game, the game has evolved from mere hardwork to computer-simulated animation, where a player can analyze his or her own micro-motions to achieve professional excellence. Assessment of the game with more and more mathematics will surely help in taking corrective measures for attaining perfection. It is better to play badminton scientifically rather than go for a ride with conventional coaching. A good player may think to correct his grip from forehand to backhand or vice-versa before attempting any handshake.