Do We Live In A Special Part Of The Universe?

[Riddick]

Ever since humans started gazing at the heavens through telescopes, we have discovered, bit by bit, in celestial terms we’re apparently not so special - Turns out not only did we not occupy the center of the universe, Earth wasn’t the center of the solar system! In fact, the solar system wasn’t central point either -

There were many star systems fundamentally like it, making up a galaxy. And the galaxy wasn’t special but one of many, which all had their own solar systems, which also had planets, some of which presumably host their own ensemble of egoistic creatures with an overinflated sense of cosmic importance.



This notion of mediocrity has been baked into cosmology, in the form of the “cosmological principle.” Its gist is that the universe is basically the same everywhere we look.

This homogeneity is convenient for astronomers because it lets them look at the universe in part as a reliable way of making inferences about the whole; whether here in the Milky Way or in a nameless galaxy billions of light-years distant, prevailing conditions should be essentially the same.

But recent observations could overturn this long-held assumption. Astronomers are gathering clues about its potential weaknesses. One approach involves looking for structures so large they challenge cosmic smoothness even at a hugely wide zoom. And astronomers have found some.

The study of cosmology itself also gives reason to question the cosmological principle. For instance, the light leftover from the big bang, called the cosmic microwave background, has some mysterious large-scale fluctuations that don’t look totally random, and that has never been satisfactorily explained.

Some scientists argued such potential challenges to the cosmological principle might be explained by another principle, cosmic variance, which refers to the statistical uncertainty inherent in astronomers’ measurements of the universe.

We are always limited by what we can see and therefore always mathematically uncertain about what conclusions to draw from a limited sample. And when it comes to studying suitably large patches of the universe, cosmologists are very limited indeed: the observable universe is only so big.

Most cosmic observations hold up against the cosmological principle very well. Certain cosmological discrepancies could be a result of cosmic variance, but it’s not enough to explain it anymore.

Validation is especially challenging when significant contrary evidence exists—and a host of recent observations suggest indeed the universe could be stranger and have larger variations than cosmologists had so comfortably supposed.

If that’s the case, humans (and anyone else out there) actually might have a sort of special view of the light-years beyond—not privileged, per se, but also not average, as “average” is no longer a useful concept at sufficiently large scales.

Still, while scientists have enough information to reasonably question the idea’s validity, they aren’t at all ready to throw out the cosmological principle just yet—least of all because no one has a solid alternative schema to replace it.

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