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  • In 1929, astronomer Edwin Hubble noticed that almost all galaxies had a red shift to their

  • color, and the farther away they were, the redder they appeared.

  • He concluded that the waves of light from the galaxies had been stretched as they traveled

  • to us, meaning space itself was expanding in all directions.

  • This observation literally shaped our image of the universe, but now some researchers

  • think that shape may be a bit lopsided.

  • The idea that space looks pretty much the same everywhere is known as the cosmological

  • principle.

  • Sure, close up there are variations.

  • The structure of star systems, galaxies, or even galaxy clusters are going to be different.

  • But on an extremely zoomed-out scale of many billions of light years, it's believed the

  • universe looks and behaves the same way in every direction.

  • In other words, it's isotropic.

  • We think it started with a big bang 13.8 billion years ago, and like a balloon, has expanded

  • more or less evenly in every direction since.

  • A good piece of evidence supporting the notion that the universe is isotropic is the cosmic

  • microwave background, the afterglow left by the big bang, which looks pretty smooth and

  • uniform.

  • An isotropic universe is convenient.

  • If everything is behaving the same and expansion is happening evenly, then we can assume dark

  • energy, what we think is driving the accelerating expansion, acts the same everywhere, and has

  • been since the big bang.

  • But what if somewhere along the way the rules changed, and the universe isn't expanding

  • evenly anymore?

  • Some astronomers decided to double check using X-ray emissions from galaxy clusters, and

  • have concluded that the universe may not be as isotropic as we thought, in other words,

  • it could beanisotropic.”

  • The researchers looked at data from almost 850 galaxy clusters.

  • Using their X-ray emissions, the astronomers estimated each cluster's temperature, and

  • thus its luminosity.

  • Keep in mind that luminosity is how much light a celestial object gives off, meaning it's

  • an intrinsic property and should be the same no matter how you measure it.

  • Once they had used x-ray observations to determine the clusters' luminosities, they cross-checked

  • the numbers using another method that relies on the rate we assume the universe is uniformly

  • expanding.

  • When they compared the two values, they found two areas of the night sky where the numbers

  • didn't match up.

  • In these regions, the clusters were as much as 30% brighter or dimmer than predicted,

  • meaning they were closer or farther away than they should be if the universe were isotropic.

  • That would throw a serious wrench into our understanding of the cosmos.

  • Why would the cosmic microwave background be so smooth when the recent universe isn't?

  • Would this mean the laws of physics are different in certain areas?

  • Is it possible dark energy affects some regions more strongly than others?

  • It's hard enough finding an explanation for dark energy when it behaves uniformly.

  • These are the questions an anisotropic universe would raise, and their answers may be unknowable.

  • But one possibility suggested by one study doesn't overturn all of our assumptions about

  • isotropy.

  • These researchers are looking to explain the findings in ways that gel with the cosmological

  • principle.

  • One explanation is some clusters could be caught in a “bulk flowwhere even more

  • massive clusters farther away drag them off.

  • Or there's the possibility that the data the conclusions are based on are just plain

  • wrong.

  • One astronomer pointed out that one region the researchers deemed particularly lopsided

  • is also near an area where the Milky Way's gas and dust are thickest.

  • It's possible that's absorbing x-rays and throwing off the luminosity calculations.

  • But the researchers do take the effect of the Milky Way into account.

  • Even if their results were due to an absorption effect, it would mean some new kind of super-dust

  • was scrambling the emissions (which gives me serious Golden Compass vibes).

  • The researchers intend to follow up with infrared observations to take another

  • stab at determining the clusters' luminosities.

  • Maybe their future results will show that their assumptions based on x-rays were off

  • and the universe is the same in all directions.

  • Then again, maybe their results will change everything we know about the history and shape

  • of the cosmos.

  • If ever a topic needed more research, this is it.

  • One instrument that will help map out the dark energy of the universe and answer this

  • riddle is ESA's Euclid telescope.

  • Amanda has a Countdown To Launch episode on that here.

  • Be sure to subscribe, thanks for watching, and I'll see you next time on Seeker!

In 1929, astronomer Edwin Hubble noticed that almost all galaxies had a red shift to their

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What if the Universe Was Lopsided?

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    Summer posted on 2020/08/12
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