In the early 20th century, the universe seemed like a much smaller place. At the time, astronomers thought the Milky Way was all there was to it. They didn’t know that there are billions of other galaxies out there. They didn’t know how young we really are.
They did not know this because they could not measure the distances to distant stars. why? There was a very simple problem in astronomy: a bright, distant star looks just like a faint star close by.
It’s the same here on earth. Imagine that you are on the beach at night and you see two glowing lighthouse lights in the distance, but one appears brighter than the other. If you are aware of Both beacons used the same lamp, you can infer that the dim light is too far away. But it’s also possible that the dim light is coming from a low-wattage bulb, perhaps one closer to you.
Scientists needed a way to figure out the intrinsic brightness of stars – to find out their electrical strength, So to speak. That’s when Henrietta Levitt, “computer” was born in Massachusetts and worked at the Harvard College Observatory. in 1908, She published a discovery that It may seem small but it is one of the most important in the history of astronomy. As we discuss on this week’s Unexplainable podcast (see embed above), the universe has opened up.
Flashing lights provide a scale for measuring the universe
Before Henrietta Levitt, many astronomers I looked at the stars In what is known today as the Andromeda Galaxy – some of them 2.5 million light years away – and mistakenly believed that they were part of our galaxy, the Milky Way (which is only about 100,000 light year in diameter).
Those Andromeda stars were orders of magnitude apart. Scientists just didn’t know that.
At that time, astronomers He had some Methods to find the distances to the stars, but it only worked for stars relatively close to Earth. Levitt’s discovery—correlating the pulsation of one type of star with its actual brightness, shown in the graphic above—was key to measuring the farthest and farthest objects in space.
Levitt’s discovery showed that if astronomers wanted to measure distant objects, they only had to look for kyphids. Its formula has led astronomers to plot the relative distances of stars: they can use it to compare two stars and see which is closer.
It took more work by other scientists to calibrate this scale and put specific numbers on it. But as soon as they did that, and started measuring with it, the universe grew and grew.
Leavitt paved the way for Edwin Hubble to discover galaxies beyond our own
Curtis believed Andromeda was a separate galaxy, far from the Milky Way. At the time, this was a strange idea. Like Chablis More mainstream show – that Andromeda was just a nebulous, hazy region within our galaxy, which it was recently estimated to exist 300,000 light-years across. This was also the supposed size of the entire universe.
If Curtis was right, that would mean the universe was two or three times the size that Shapley had estimated—at least.
to settle the debate, Edwin Hubble – namesake of the famous space telescope – looked for Cepheid stars in Andromeda. night after nightHowever, he took pictures of Andromeda, searching for Cepheid. In October 1923, he found one, flashed in one of Andromeda’s spiral arms. Another week out Notes It allowed him to follow Leavitt’s formula and determine the distance.
Hubble estimated that it is about a million light-years from Earth – outside the bounds of Shapley’s universe. (He was a little Hubble Off: Andromeda is closer to 2.5 million light-years away.) After reading about Hubble’s discovery, Shapley reportedly He said: “This is the message that destroyed my universe.”
Scientists have continued to build on Levitt’s ruler to measure the universe. And as they used these measuring tools, their understanding of the universe advanced. They realized that it was much larger than previously thought, that there are billions of galaxies out there, and it is expanding: these galaxies are moving farther and farther away from each other.
Astronomers also realized that the universe had a beginning. If galaxies are moving away from each other now, that means they were closer together in the past – leading scientists to the idea of a Big Bang.
It also led them to realize that the universe might eventually end.
This week’s episode of inexplicablea Vox podcast about unanswered questions in science, tells that story and more.