👩🏼‍🚒 👩🏻‍🎨 📘 What do coronavirus and chess have in common? 🐕 🚆 💃

The return of the old legend of the ancient king who did not develop the skills of exponential thinking.

Everyone already knows about coronavirus and why it is dangerous, but I came across an extremely high level of carelessness about this. Indeed, at the time of publication in Russia, officially there were 64 cases (like cells in chess) of infection and all of them are in quarantine. The problem seems to be somewhere out there, but so far everything is fine with us. I am sure that the readers of Habr have many friends with this attitude. This short article is for them.

According to legend, the inventor of chess asked the king for a reward for the first cell of his creation one grain of wheat, for the second 2, for the third 4 for the fourth 8 ... The

king was surprised at the modesty of the master, agreed ... and got into big debt.

It can be understood. Our thinking is poorly adapted to work with exponentially growing phenomena, however, the king fell on

2^{64} - 1 = 18446744073709551615

$2^{64}-1=18 446 744 073 709 551 615$ seeds (this is more than a trillion tons of grain).

Coronavirus asks for a more modest reward. He needs every day that the number of infected grows by only 20%. Maybe this modest does not require such a serious relationship?

Let's see how he will increase the number of cases in a month, if he does not interfere with doing his job.
Suppose he starts with 10 people who flew to a country from an infected region shortly after the outbreak (in the new year). Then

1 day = 10 h.
2 day = 1 day + 1 day * 0.2 = 10 * 1.2 h
3 day = 2 day + 2 day * 0.2 = 10 * 1.2 * 1.2 h =

10 * {1.2}^{2}

$10*1.2^{2}$
4 day = 3 day + 3 day * 0.2 = 10 * 1.2 * 1.2 * 1.2 h =

10 * {1.2}^{3}

$10*1.2^{3}$
...
N day =

10 * {1.2}^{N - 1}

$10*1.2^{N-1}$
...
February 1 =

10 * {1.2}^{31}

$10*1.2^{31}$ = 2,848 people
...
March 1 =

10 * {1.2}^{60}

$10*1.2^{60}$ = 563,475 people.

Suppose in this country on February 1 they introduced public awareness about hygiene and canceled mass events. Suppose also that it reduced the spread coefficient by only a quarter (up to 15%)

10 * {1.2}^{31} * {1.15}^{29}

$10*1.2^{31}*1.15^{29}$ = 164 004 at the beginning of March

563475/164004 = 3.43 times. Accordingly, by mid-March, at the end of the two-week incubation period in hospitals, we have three times fewer patients with serious complications.

We, of course, are not China, which builds and launches a hospital in 10 days, but a month of delay until the peak of the epidemic would be a great help so that the authorities can prepare and equip the clinics.

Exponential law gives us a simple technique for calculating the effectiveness of a strategy,
regardless of the current number of patients. In a month we have

(1.20 / 1.15)^{30} = 3.5851

$(1.20/1.15)^{30}=3.5851$ (the number of seriously ill patients is reduced by more than three times).

For the reader of this article, the most important thing is:

Understand that the virus is already here, in any city. Perhaps already with you or your neighbors. It is actively distributed
Strictly observe hygiene.
Take care of elderly relatives (16% mortality)
Refuse from mass events, and ideally take sick leave and sit at home with a couple of weeks (the situation will unfold in the coming weeks. We are not panicking, but getting ready).
Protect others. Wear a mask for any respiratory ailments
Share information with the widest possible range (this really significantly reduces the rate of spread of the infection)

Take care of yourself and your loved ones!

High-quality selection of information on the topic .

What do coronavirus and chess have in common?

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