Up, down, round and round

I recall seeing a comic strip a while back making fun of one of the features of Star Trek that doesn't seem ridiculous until you think about it a little.  Have you noticed that whenever two starships are near each other -- whether it's the Enterprise and other Federation ships, or they're being threatened by the Romulans or Klingons or whatnot -- the ships are almost always oriented the same way?  The only time this is not the case is when the showrunner wanted to make it clear that the other ship was disabled and drifting.  Then it was shown at some odd angle relative to the Enterprise.  In the comic strip, it showed what it would look like if all the ships were at random orientations -- how ridiculous it appeared -- but really, isn't that what you'd expect?  In the Star Trek universe, each ship is supposed to come with its own artificial gravity, so within any ship, up is "toward the ceiling" and down is "toward the floor."  It wouldn't need to line up with any other ship's artificial gravity, so except for an occasional coincidence, they should all be at various angles.

In space, there's no preferred direction, no "up" or "down."  You always have to describe position relative to something else -- to the axis of the Earth's rotation, or the plane of the Solar System, or the plane of revolution of the Milky Way.  But even those aren't some kind of universal orientation; as I described in a recent post, the universe is largely isotropic (the same in every direction).  Just like the starships in Star Trek, there shouldn't be any preferred directionality.

Well, that's what we thought.

A new paper this week in the journal Monthly Notices of the Royal Astronomical Society describes a set of data from the James Webb Space Telescope that is absolutely astonishing.  Here's how the authors describe it:

JWST provides a view of the Universe never seen before, and specifically fine details of galaxies in deep space.  JWST Advanced Deep Extragalactic Survey (JADES) is a deep field survey, providing unprecedentedly detailed view of galaxies in the early Universe.  The field is also in relatively close proximity to the Galactic pole.  Analysis of spiral galaxies by their direction of rotation in JADES shows that the number of galaxies in that field that rotate in the opposite direction relative to the Milky Way galaxy is ∼50 per cent higher than the number of galaxies that rotate in the same direction relative to the Milky Way.  The analysis is done using a computer-aided quantitative method, but the difference is so extreme that it can be noticed and inspected even by the unaided human eye.  These observations are in excellent agreement with deep fields taken at around the same footprint by Hubble Space Telescope and JWST.

This adds a whole new twist (*rimshot*) to the horizon problem and the isotropy of the universe as a whole.  Not only do we have the issue that causally-disconnected regions of the cosmic microwave background radiation, that are too far apart to have ever influenced each other (something I describe more fully in the above-linked post), are way more similar in temperature than you'd expect -- now we have to figure out how causally-disconnected galaxies on opposite sides of the universe could possibly have ended up with correlated rotational axes.

The authors admit it's possible that this measurement is due to something about the Milky Way's own rotation that we're not compensating for in the data, but there's a more out-there explanation that the paper's authors are seriously considering.

"It is not clear what causes this to happen," said study co-author Lior Shamir, of Kansas State University, in an interview with Independent.  "[But] one explanation is that the universe was born rotating.  That explanation agrees with theories such as black hole cosmology, which postulates that the entire universe is the interior of a black hole."

Black holes are defined by three properties -- mass, electric charge, and... angular momentum.  That we're inside a rotating black hole would explain the anomaly JWST just observed.  Since -- at least as far as our current understanding goes -- anything inside a black hole's event horizon is forever inaccessible, perhaps this means that event horizons are boundaries between universes.  As bizarre as that sounds, there is nothing about what we know of the laws of physics and cosmology that rules that out.  Which would mean that...

... black holes are bigger on the inside.

The Doctor tried to tell us.

Of course, the more prosaic explanation -- that the data were somehow influenced by our own motion through space -- has yet to be decisively ruled out.  I can't help but feel, though, that if the authors thought that was likely, they (or their reviewers) would have suggested waiting and re-analyzing before publishing in a prestigious journal like MNRAS.  The greater likelihood is that this is a real signal, and if so, it's mighty odd.

As far as what it would mean if we found out we are inside a black hole, well -- I'm hardly qualified to weigh in.  It probably wouldn't affect our day-to-day life any.  After all, it's not like we were going to find a way out of the universe anyhow, much as recent events here on Earth have made many of us wish we could.  All I can say is stay alert for further developments, and keep looking up.

Whatever direction that actually is.

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Cloud collision

Contrary to what the medieval church wanted you to believe, the Earth is in constant motion.

They went to enormous lengths to stand by the principle that we're the center of the universe, motionless, while everything revolves around us in perfect circles.  Arrogant attitude, that.  Also wildly wrong.  Not only is the apparent motion of the stars at night caused by our own rotation, the stars aren't in quite the same positions at a given time one night as compared to the next because we're revolving around the Sun.

Then along came Kepler, and showed that even the "perfect circles" part was wrong; the planets and their moons orbit in ellipses, not circles, some of them quite eccentric (the mathematicians' word for the degree to which an ellipse deviates from a circle).

It's even worse than that.  The Earth's axis precesses, wobbling like a spinning top, drawing out a circle in the sky once every twenty-six thousand years.  So Polaris, hasn't always been the pole star, and at some point won't be any longer.  This fact was discovered by the Greek astronomer Hipparchus, but although the aforementioned church fathers loved the Greek philosophers -- they were especially fond of Aristotle -- they were also excellent at ignoring evidence that challenged their own worldviews, so Hipparchus's studies of axial precession were brushed aside.  The thirteenth century Persian polymath Nasir al-Din al-Tusi studied astronomical records and came up with a value very close to our currently accepted precession rate, but the church fathers didn't much listen to the Muslims, either, so it wasn't until eighteenth century French mathematician Jean le Rond d'Alembert said, "No, really, guys, this precession thing is real" that people in the western world started to accept it.

The path of apparent precession of the pole star. The bright star at the bottom is Vega, which was the pole star twelve thousand years ago (and will be again in fourteen thousand years). [Image licensed under the Creative Commons Tauʻolunga, Precession N, CC BY-SA 2.5]

But even that's not the end of it, because the Sun (and the rest of the Solar System) are in the edge of one of the spiral arms of the Milky Way, and are traveling at about 230 kilometers per second in orbit around the galactic core.  This is a good clip -- it's only a bit under a thousandth of the speed of light -- but even so, the galaxy is so enormous it will take about 225,000,000 years to complete one orbit.  Put another way, the last time the Solar System was in this spot was the early Triassic Period -- right at the beginning of the "Age of Dinosaurs."

It's this last motion that's what brings the topic up today, because a team led by Boston University astronomer Merav Opher has just found that the motion of the Sun and planets around the galactic center swept it through two successive clouds of cold gas and dust, hitting one about seven million years ago and another a little over two million years ago.  The clouds, which from our current perspective are in the constellation of Lynx, provided enough resistance that the heliosphere -- the region of space dominated by the outward pressure of material thrown off by the Sun -- shrank to the point that the planets were exposed to the dust of the interstellar medium.  This caused a spike of supernova-generated isotopes like iron-60 and plutonium-244 in cosmic dust trapped in sediments and ice layers here on Earth.

Opher's team found this cosmic dust in every place of those ages they looked.  It was the fingerprint of a collision -- between the Solar System and a pair of clouds.

It's an open question what effect that had on the Earth.  The collisions happened just as our hominid ancestors were moving their way out of the African savanna, so any additional flux of cosmic rays from being outside the heliopause didn't seem to do us any harm.  But it's a cool reminder that although we feel like the Earth is solid and unmoving beneath our feet, it's actually being spun around the universe like a little kid on the Tilt-o-Whirl.

But finally, there's even another layer on top of all the above, because the Milky Way and the entire Local Group are moving toward something called the "Great Attractor" at six hundred kilometers per second, over twice as fast as the Solar System's orbital velocity around the galactic center.  Presumably this is because of some sort of gravitational effect, but what sucks is that although we know the general direction where the Great Attractor is located, we don't even know what's there because it's directly on the opposite side of the center of our own galaxy.  In other words, we can't see where we're headed because the Milky Way is in the way.  

What it's in the way of remains to be seen.

So yeah.  The medieval church fathers were kind of spectacularly wrong.  The more we've learned, the weirder the universe gets, and the farther from the center of anything we appear to be.  It's better this way, though, because it gives us constant reminders of how grand and magnificent the universe is -- even if the inevitable consequence is a reminder of how tiny we are by comparison.

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