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*Physical evolution has its limits in the long term.

The fact that the Earth will not last forever poses a fiendish challenge to all the lives on the planet. No matter how successfully life forms have evolved in the Earth’s environment, they will inevitably go extinct once their home planet has disappeared. Different directions of evolution must be chosen by any species with the ambition to discover the ultimate truth about the universe.

*The evolution of intelligent species is no longer physical, but mental.

Driven by natural selection, physical evolution takes a long time because genetic characteristics are only passed…

The news about the arrival of Covid-19 vaccines was exciting last year. Many people, however, are still hesitant to get immunized.

It is vaccinations that will end the pandemic at the lowest cost. I think that a vaccination dashboard is needed for the illustration of vaccine quality.

The dashboard includes the information about Covid-19 vaccination such as how many people vaccinated, together with the ratios of infections, severe cases, deaths, side effects and etc. These vaccination data could be compared with the non-vaccination data to illustrate a vaccine’s safety and effectiveness. …

We know the covid-19 virus mostly spreads through close contacts between people. While close contacts are greatly limited in public, they are generally accepted at home. It is time to introduce transmission control into homes when a lockdown is in place or when the number of cases is escalating. Measures to reduce the risk of infection between households are similar to those in public. For example:

1. Keep physical distance from each other.

2. Wear face coverings.

3. Practice personal hygiene.

4. Maintain good ventilation.

5. Communicate through text rather than mouth.

6. Follow the instructions from local health departments.

Mathematics involves a lot of calculation with numbers. Since the calculating process is a logical one, it is important for a language to form the right words for numbers. Twenty-six, for instance, is a right word for 26, because ‘twenty-six’ indicates 2 before 6. Sixteen, on the other hand, is a confusing word for 16, because ‘sixteen’ sounds like 6 before 1. In fact, the words for the numbers from 11 to 19 are all puzzling in the same way. We need precise words to represent the numbers. For example:

11 = ten-one

12 = ten-two

13 = ten-three


A creative problem-solver needs logical thinking with imagination, because imagination enables one to form something new in the mind while logical thinking helps to distinguish an effective solution from impractical ones.

Without imagination, you will probably get stuck in a new problem. Without logic, on the other hand, you are likely to get lost in an imaginary world. Logical thinking with imagination is the key to solving new issues.

Studying mathematics is good for logic training. Playing chess involves a lot of rational moves. Writing programs makes the brain run as a computer. …

Most patients with Covid-19 can be infectious about two days before they develop symptoms. Some patients who never show any symptoms can still infect others before their recovery. The transmission during both asymptomatic periods is hard to detect.
As asymptomatic patients hardly cough or sneeze, their spread of the virus should be through talking, breathing and singing. Since most of Covid-19 infection has spread from person to person indoors, some recommendations for indoor activities would be:
1. Less talking. The purpose of talking can be achieved mostly by exchanging text on smartphones, computers or a piece of paper.
2. Safe breathing. As physical…

As schools are usually empty at weekends, it is possible to reduce the density of students by keeping schools open on Saturday and Sunday. In theory, the density will be reduced by 28% (2/7=28%). For example, if a school has 5 classrooms and 5 classes, then divide students evenly into 7 classes. The new 7 classes are named as 1 to 7 respectively. A weekly schedule for the classes will be:

Monday: 1,2,3,4,5

Tuesday: 2,3,4,5,6

Wednesday: 3,4,5,6,7

Thursday: 4,5,6,7,1

Friday: 5,6,7,1,2

Saturday: 6,7,1,2,3

Sunday: 7,1,2,3,4

In the schedule, each class has five days at school and two days at home…

Since most of Covid-19 infection has spread from person to person indoors, smartphones should be able to find out indoor contacts when making a risk evaluation of infection for users. There are two methods to detect whether people are inside a building or not.

1. The GPS signals are usually weaker indoors than outdoors because buildings are blocking the signals sent by GPS satellites. So, if smartphones find weak GPS signals, their users are likely in a building.

2. People are normally more physically active outdoors than indoors. We know smartphones can detect their own vibrations. …

Since Google and Apple made changes to Android and iPhone operating systems to facilitate digital contact tracing, many countries have been developing Bluetooth-based apps. Despite serious doubts about their accuracy and efficiency, these apps could still help control the Covid-19 epidemic by providing users with risk evaluations of infection and with recommendations.

Firstly, make a set of criteria for daily evaluation, such as,

1. How many contacts has the user made?

2. How much time has the user spent with the contacts?

3. How many places has the user visited?

4. How many symptoms of Covid-19 has the user developed…

A single figure doesn’t tell much. The relationship between two numbers is more interesting, especially between one and the total number of confirmed cases.

*The proportion of patients who have recovered: the higher, the better.

A high rate of recovery is usually due to a great proportion of the patients with mild diseases, because it takes much longer time for patients with severe symptoms to recover than those with mild or no symptoms.

Active measures, such as conducting massive PCR testing and efficient contact tracing, are needed to find out more people with Covid-19.

*The proportion of hospitalized patients: the…

Xu Jun

A learner.

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