During the 20th century, scientists would just look at the night sky and imagine How do we know how far a star is and what is its brightness? Because a star which would be very bright wold seem to be very dim if it was very distant from you. Stars pulse too i.e., they blink from bright to dim, they may do that really fast or slow.Henriatta Leavitt clicked photos of a clusters of stars in the sky for a veryyy long period of time, and she discovered a pattern, a pattern which opened all doors of space science. It was:The brighter a star is, the slower it pulses.read it thrice, think about it.

Henriatta Leavitt

Hubble measured the distance to a star which was so far, that the science community declared it to be of somewhere out of the Milky Way Galaxy; the andromeda galaxy.Henriatta indirectly hepled discovering a new galxy, and the expansion of the universe. Hubble noticed that the galaxies are moving apart and apart. This idea completely changed everyone's perception. Before this discovery, it was believed that the cosmos is constant. It has always been there and it never contracts or expands.Assume a balloon with dots on it, you inflate the balloon and the dots move apart. This is an analogy.

The doors she opened

If universe has a beginning, it must have an end, right? I mean look at you, you born and you will die. There are 2 ways:<ol><li>The heat death- It states that everything will go sooooooooooooooooooo distant that the entropy would be zero and nothing will interact. And all will die. (More likely)</li><li>The Big Rip- This states that everything will start to rip from the centre. The stars to planets to earth to humans to atoms to quarks. AMD dark energy will cause this. And that's how it will end. (Hoho, hollywood)</li></ol>But relax you won't experience it anyways. 100 billion years to go bro.

The end of the universe

Imagine you throw a ball up in the sky, but instead of coming down, it slows for 1 sec and then shoots off in space like a rocket. What will be your reaction?Scientists had the same reaction when they discovered that the expansion of the universe is speeding up very fast.Because it was thought to be slowing down but it has always been speeding up.Physics is so astonishing.

Speed of the expansion

Let us understand this- Suppose stars are light bulbs ok? 100 watt bulb=bright star.Now, you see a 100 watt bulb in the sky, but you notice that it pulsing very fast i.e., it is going from bight to dim to bright to dim very fast. But according to Henriatta, a 100 watt bulb would pulse slow (a bright star pulses slow). which means that this is a 30 watt bulb close to the earth, and you see it bright because it is close to you . BINGO!Ex 2- you see a dim star pulsing slowly, which is false cuz Dim pulses fast. Hence, this star is actually very bright but it is far away from you.(Got it?)

Understanding her discovery

The dots on the balloon move apart, when you blow air in it. What causes the universe to do so or to expand?.It turns out to be dark energy. Scientists know 1 thing about dark energy that they don't know it. Dark energy is 1 of the biggest mysteries, no one can say anything about it. But we know it is causing the universe to expand.So, if the universe is expanding, it would have started with 0, right? I mean imagine the expansion in reverse. This imagination is what gave rise to The big bang theory (about that in another stash)

Beginning and dark energy

Listen to this episode from Unexplainable on Spotify. In the early 1900s, Henrietta Leavitt made one of the most important discoveries in the history of astronomy: a yardstick to measure distances to faraway stars. Using this tool, scientists eventually transformed our understanding of the universe. They realized space was expanding, that this expansion was accelerating, and that ultimately, everything will end.  For more, go to http://vox.com/unexplainable It’s a great place to sign up for our newsletter, view show transcripts, and read more about the topics on our show. Also, email us! unexplainable@vox.com We read every email. Support Unexplainable by making a financial contribution to Vox! bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices