It is not difficult to find an answer to this question.
They find out what is going to happen in your life also much the same way as you find out an answer to your question today by typing out what you want to know in the Search box of the Internet. You type out your query and down you get a list of so many Links found out by the Search Engines of Google or Yahoo.
Astrologers commit to memory which combinations of various Houses (12 of them), the Grahas (9 of them) occupying them, the Nakshatras (27 of them) occupying them ( since when ), the Dasha or Mahadasha and various Raashies (Zodiac Signs) influence which aspects of life, such as, education, business, marriage, friendships, health problems (related to stomach, orthopaedics, kidney or liver etcetera), personal disputes (related to the ownership of land or property), financial losses and profits and they start looking at your Grahas (9 of them) occupying them, the Nakshatras (27 of them) occupying them ( since when ), the Dasha or Mahadasha and various Raashies (Zodiac Signs) at various times of your life.
They dig out what sort of things had happened in the life of others in the past under such combinations of the Houses, Grahas, Nakshatras, Dashas and Raashies as you may be having at that time to` tell you what you could expect to happen in your life.
Of course no one can guarantee whether such predictions may be really true.
The astrologers only expect that what usually happens under such combinations may happen in your case as well.
But you need not question, how stars located that far away from us may play any role in our life.
We see so many stars in the sky. We are able to see them since the light coming from them enters our eyes.
The light may be very feeble but it may also influence us much the same way as the bacteria and the viruses affect us even though they are so tiny in size.
True but we should bear in mind we can expect some errors due to following reasons.
- When astrology had been developed the axis of the Earth did not point toward Polaris. It pointed toward Thuban or Vega as shown below.
- Astrologers decide the Zodiac Signs assuming as if the constellations corresponding to them would ascend into the sky on the same dates every year while it is not at all so.
- Neptune, Uranus and Pluto had not been discovered when astrology had been developed.
- The astrologers preferred to have only 12 Zodiac Houses since 360° can be easily divided by 12 but not by 13 even though they very well knew about the existence of Ophiuchus.