# How to! 5) Multiply two digit numbers in your head

Hi,
today I was sitting outside, chilling out and just as that I started to multiply numbers always adding one: 1*1=1 2*2=4 3*3=9 and so on. And I wondered, how far can this go without paper or calculator?

Well I finished with 100*100 without leaving single number and after a while I started to use this kind of fast and intuitive technique which in this post will be used only to multiply two same numbers smaller than 100.

Lets say you need to multiply 47*47.   (40+7)*(40+7)

Fourty will be called “base number”. The first thing you need to do is to multiply base numbers to get your base. This is simple because 40*40 is the same as 4*4 plus two zeros which means 1600.

Base is quite easy to remember so you do not need to concentrate on that much. Now we need to combine base numbers with, lets call them “pariah numbers”.

In our case pariah number is 7. You multiply it with base number to get 40*7=280 or simply 4*7=28 (+ zero from base number). Because we have two same brackets we need to multiply this twice and add it which is the same as multiplying your result by 2.

280*2=560

Now just add this “double number” to your base which should be quite easy:

1600+560=2160

Repeat this one few times and then add the product of two pariah numbers to get the result:

2160+(7*7)=2160+49=2209

Try this few times, and if you are sure in this simple case try any two digit numbers. It is quite nice way to warm up your brain 😉

Dragallur

# How to! 4) Go stargazing for the first time

Hi,
since I went out stargazing couple of times already, I would like to mention few things here for you, when you decide to go alone or maybe with your boyfriend/girlfriend stargazing. While I live on northern hemisphere all of these tips will be useful to south people.

### Preparation

Check out the time when the sun sets where you live. This page is quite useful for that, you just need to insert your location.

It is quite useful to know what these terms mean, astronomical dusk is what you are looking for.

So you need to watch out for the time when first stars/planets appear which will be some time after the dusk, of course there must be clear sky which you need to check on Google forecast [1] or in TV.

Then while it depends on the time of year, it is good to take some extra clothes, because most probably you will be standing still for some time, so you might get cold.

### How to stargaze

First option: take some sky map on paper with you. You can print some from internet but check if you are printing the right hemisphere. For this, you will need also some light, but not white, since you would never build night vision, take red, eyes are not so sensitive to it.

Second option: take your smartphone and download application with stars, I use Star Walk 2 Free and it is pretty good, especially because there is option for night vision so it is red, this is very useful though you must never lock your phone, because when you want to use it again the light from you display would pretty much destroy the night vision you build up.

What is night vision anyway? It is the activation of all your non color sensors in eyes and the adjusting of your vision in darkness by enlarging the part that collects light, it take about 30 minutes though you may see the effect even after 4 or 5.

### Pick a good location

Be sure to pick a good location. If you are in big city, than make sure to drive to countryside because the light pollution would just waste your time.

Best is hill though it is good to be on some field or place where there are no trees.

Keep away from any buildings and streets. It is important for you to keep the night vision, one single mistake when you look in street light could destroy the whole process.

# Enjoy 😉

Dragallur

PS: it is better to go stargazing when there is new moon, otherwise, full moon spoils the view of huge part of sky.

[1] To get in Google forecast just type “weather” and “your location”.

# How to! 1) Using stars to navigate

Hi,
here it goes, here it comes. Just because of random I just made another series which may not continue anymore but I don`t care I made it just for fun and today I will write about really practical skill if you dont know where the hell you are. You just have to know couple of things.

It is always crucial to know the constant direction in which you want to walk. If you have compass it should not be a problem unless when you are in the mountains there may appear bubble because of different pressure and it wont disappear again so watch out for this because then it wont be so accurate.

So the easiest thing is to find Polaris or North Star on the northern hemisphere. It is one of the most bright stars and and also Polaris is exactly at the point around which whole sky is rotating so it will always be on the same spot as you can see on the picture with high exposure.

You can find it when extending the big dipper, which is very bright constellation, 5 times.

Polaris will always point to the north and it should rise as you go north and set while you go south. This concept is very useful when measuring your latitude.

For this you need something to measure degrees. I heard that your fist on the length of your arm is about 10° or you can use watch that are not digital because the difference between two numbers should be 30°. If you are PRO then you will have sextant of course :D. You should measure 90° on poles and zero on equator.

To know your longitude it is a bit more complicated. You need clockwatch which has some time like Greenwich, just that you know where this time is. Then during day you will measure when the Sun is highest which can be almost anytime since your watch are not on the time zone where you are.

Then because there is 24 time zones you know that for one time zone there is 15° of longitude + you will add half hours or whatever you measured when was the Sun highest. Then you will know how much you moved to west or east. With the method of sextant you can easily measure where is your place on the Earth. I will make sure to try it when it will be clean sky to see how accurate it is. Anyway if you want this to be useful you have to check the map to see the coordinates of some cities.

But you can use any star to orient yourself!
Put two tall things about meter apart. Than line up the tops of the things with any star and wait to what direction it moves.

• If the star rose, you’re facing east.
• If the star sank, you’re facing west.
• If the star moved to the left, you’re facing north.
• If the star moved to the right, you’re facing south

Btw. for this last one thanks to wikihow article, I did not know that.

Also on south to know south, use South cross. Line up the two stars that
are making the T and they should point Alpha Centauri, the closest star and Alpha Centauri points to south.
Dragallur

Polaris photo 1st and 2nd
Sextant photo and South cross photo