Ever since humans began observing the heavens through telescopes, we gradually realized that from a celestial perspective, we are clearly not that special. It turns out that the Earth is not the center of the universe. It wasn’t even the center of the solar system! Unfortunately, the solar system was not the center of the universe either. In fact, there were many star systems basically similar to this one, which together formed a galaxy. And didn’t you know, this galaxy isn’t special, it’s just one of many galaxies, all with their own solar systems and planets, some of which are probably cosmic. It seems to be inhabited by a group of selfish creatures who have over-exaggerated their importance. .
This concept of banality is baked into cosmology in the form of the “cosmic principle.” The gist is that the universe is basically the same everywhere you look, homogenized like milk, made of common materials evenly distributed in all directions. At the top of the cosmic hierarchy, huge groups of galaxies are consolidated in vast material-rich filaments or sheets around gaping intergalactic gaps, but beyond that the structure declines. It seems like it will happen. Alexia Lopez from the University of Central Lancashire in the UK says that if you could zoom out and see the entire universe, “it would look very smooth.”
Lopez compares space to a beach. If you take a handful of sand under a microscope, the sand grains will look like special individuals. “You’ll see different colors, shapes, and sizes,” she says. “But when you walk across the beach looking at the dunes, all you see is a uniform golden beige color.”
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It means that Earth (or the trillions of other planets that are supposed to exist) and its tiny corner of the universe don’t seem to occupy a particularly privileged position compared to everything else. Masu. And this uniformity is good for astronomers. Because it allows us to look at parts of the universe as a reliable way to reason about the universe as a whole. Whether we’re here in the Milky Way or in some unnamed galaxy billions of light-years away, the general situation should be essentially the same.
This spirit of simplification applies to everything from understanding how dark matter weighs down galaxy clusters to estimating how common life-friendly conditions are throughout the universe, and it’s important to note that astronomy It allows researchers to simplify mathematical models of the universe’s past and predictions of its future. . “It’s all based on the idea that[the cosmic principle]is true,” Lopez says. “It’s also a very vague assumption, so it’s very difficult to test.”
Verification becomes particularly difficult when significant evidence to the contrary exists. And a number of recent observations actually suggest that the universe may be stranger and more volatile than cosmologists have easily assumed.
If so, humans (and others out there) may actually have some kind of privileged view of the world beyond light years – though not a privileged one per se. , not even average. That “average” is no longer even an average value. A concept that is useful on a large enough scale. At least on large scales, “different observers may see slightly different universes,” says Valerio Mara, a professor at Brazil’s Federal University of Espírito Santo and a researcher at Italy’s Trieste Observatory. .
Astronomers have not yet abandoned the cosmological principle, but they are gathering clues about its potential weaknesses. One approach involves looking for structures large enough to challenge the smoothness of the universe even at very wide zooms. Scientists calculate that anything wider than about 1.2 billion light-years would disrupt the uniform apple car of the universe.
And astronomers have discovered some. For example, López discovered a monster called the Giant Arc, a curve in the galaxy that spans about 3.3 billion light years. She also discovered the Big Ring, a torus of galaxies about 1.3 billion light-years in diameter and 4 billion light-years around. The two oddities are close together and may themselves be connected to a larger structure.
The study of cosmology itself also gives reasons to frown upon the cosmological principle. For example, the leftover light from the Big Bang, called the cosmic microwave background radiation, has some mysterious large-scale fluctuations that don’t appear to be completely random, says Dragan Hutterer, a cosmologist at the University of Michigan. do. “This was never satisfactorily explained,” he says.
Some scientists argue that such potential challenges to cosmological principles may be explained by another principle, cosmic dispersion, which refers to the statistical uncertainty inherent in astronomers’ measurements of the universe. I’m doing it. We are always limited by what we can see, so we are always mathematically uncertain about what conclusions we will draw from a limited sample. Perhaps the fluctuations that astronomers saw were simply the result of imperfections rather than an actual reflection of the nature of the universe. Perhaps what looks like an unusual bump in the smoothness of the universe will flatten out compared to the unobserved clumps of space that flank the volume we see.
And when it comes to studying appropriately sized parts of the universe, cosmologists are actually very limited. The observable universe is only that big. “If you say, ‘I’m going to study the shapes of galaxies,’ you’re in luck. There are billions of galaxies in the universe. You can use statistics to address your questions, and the variance of your sample is very small. It’s smaller,” Hutterer said. At larger scales, we only get a few examples, because the observable universe is only divided into so many large sections.
Mara had thought for some time that certain cosmological contradictions could be the result of differences in the universe. But, according to his and others’ calculations, just explaining it is no longer enough.
Still, most cosmological observations often violate cosmological principles. Scientists therefore have enough information to reasonably question the validity of this idea, but they are not at all ready to abandon it. At least, because no one has a solid alternative schema to replace that idea.
“There is no conclusive evidence of a violation of the principles,” Hutterer said. “But there are some very interesting anomalies.”
In any case, this is a difficult problem to decipher due to the nature of cosmology. “Unlike laboratory experiments, which can be repeated over and over again, you only get one universe,” says Hutterer.
