Lost Art of Asking Questions - Henrietta Leavitt's yardstick to the universe.

If I asked you, Have you heard of Edwin hubble?, most like yes would be the answer, however if I asked you who is Henrietta Leavitt ? what would you say?

Henrietta Leavitt, worked at Harvard College Observatory as "Computer", yes they were called "computers" because they did complex calculations manually as this was era before computers. They were trying to map the stars in sky and it was believed that Milky way Galaxy is all we have in entire universe.

She observed, that these stars varied in brightness like beacons every 30 days or dim->bright->dim then she observed, brighter the star slower it blinked. So frequency of blinking told how bright a star was. If you knew how bright it is then you can see how dim it can appear from distance in space and this can be used to calculate the distance of this star.

Leavitt's Law or the period-luminosity relationship, gave astronomers a standard candle to measure the distance to other galaxies. By knowing the period of a Cepheid variable, astronomers could determine how bright it was and how far away it was, allowing them to measure distances up to 10 million light years. It became known as the "yardstick to the universe"

This was used by Hubble to find out that Andromeda is another galaxy as big as Milky way and today we know there are 100 billion galaxies.

Speculatively she seems to have asked

What is the relationship between a star's brightness and its distance from Earth?

How can we use variable stars to measure distances in the universe?

What are the characteristics of variable stars?

What are the underlying principles governing the behavior of Cepheid variables?

Miss Leavitt's Stars