What is the cosmic web?
When you zoom far enough out, our universe has a very unusual structure.
- Composed of massive filaments of galaxies separated by giant voids, the cosmic web is the name astronomers give to the structure of our universe.
- Why does our universe have this peculiar, web-like structure?
- The answer lies in processes that took place in the first few hundred thousands years after the Big Bang.
Looking up at the night sky, it seems as though the stars and galaxies are spread out in a more or less random fashion. This, however, isn't really the case. The universe isn't a random jumble of objects; it has a structure composed of galaxies and gas. Cosmologists call this structure the cosmic web.
The cosmic web is composed of interconnecting filaments of clustered galaxies and gases stretched out across the universe and separated by giant voids. The largest of these filaments that we have found to date is the Hercules–Corona Borealis Great Wall, which is a staggering 10 billion light years long and contains several billion galaxies. As for the voids, the largest is the Keenan, Barger, and Cowie (KBC) void, which has a diameter of 2 billion light years. Within a segment of the spherical KBC void lies the Milky Way galaxy and our planet.
Altogether, these features give the universe a foamy appearance. However, once you zoom out far enough, this pattern disappears, and the universe appears to be a homogeneous chunk of galaxies. Astronomers have a delightful name for this sudden homogeneity — the End of Greatness. At smaller scales, however, we can see that the universe does indeed have a rather magnificent structure. This begs the question: How did this structure come to be?
It starts with a bang
Space itself has fluctuating energy levels. Incredibly small pairs of particles and anti-particles are spontaneously coming into existence and annihilating each other. This "boiling" of space was happening in the early universe as well. Normally, these particle pairs destroy each other, but the rapid expansion of the early universe prevented that from happening. As space expanded, so too did these fluctuations, causing discrepancies in the density of the universe.
A visualization of quantum fluctuations.
Because matter attracts matter through gravity, these discrepancies explain why matter clumped together in some places and not others. But this doesn't fully explain the structure of the cosmic web. After the inflationary period (roughly, 10-32 seconds after the Big Bang), the universe was full of primordial plasma clumping together due to the aforementioned discrepancies. As this matter clumped together, it created pressure that counteracted gravity, creating ripples akin to a sound wave in the matter of the universe. Physicists call these ripples baryon acoustic oscillations.
Simply put, these ripples are the product of regular matter and dark matter. Dark matter only interacts with other things through gravity, so the pressure that causes these ripples doesn't affect it — it stays at the center of ripple, not moving. Regular matter, however, is pushed out. A little under 400,000 years after the Big Bang, the universe has cooled enough such that the pressure pushing the matter out is released through a process called photon decoupling.
An artist's illustration of the rings formed by baryon acoustic oscillations.
Zosia Rostomian, Lawrence Berkeley National Laboratory
As a result, the matter is locked into place. Some regular matter finds its way back to the center of the ripple due to the gravitational attraction of the dark matter. The result is a bullseye: Matter in the middle and matter in a ring around the middle. Because of this, physicists know that you're more likely to find a galaxy 500 million light years away from another galaxy than you are to find one 400 or 600 million light years away. Simply put, galaxies tend to be found at the outer rings of these cosmic bullseyes.
Altogether, these processes produced the gigantic web of stuff that compose our universe. Of course, there are many other processes that go into producing the cosmic web, but these fall outside the scope of this article. For those of you interested in observing what this structure would look like, you're in luck: astronomer Bruno Coutinho and colleagues developed an interactive, 3D visualization of the universe's structure, which you can access here.
The Cosmic Web, or: What does the universe look like at a VERY large scale?The Millennium Simulation featured in this clip was run in 2005 by the Virgo Consortium, an international group of astrophysicists from Germany, the United K...
To create wiser adults, add empathy to the school curriculum.
- Stories are at the heart of learning, writes Cleary Vaughan-Lee, Executive Director for the Global Oneness Project. They have always challenged us to think beyond ourselves, expanding our experience and revealing deep truths.
- Vaughan-Lee explains 6 ways that storytelling can foster empathy and deliver powerful learning experiences.
- Global Oneness Project is a free library of stories—containing short documentaries, photo essays, and essays—that each contain a companion lesson plan and learning activities for students so they can expand their experience of the world.
Philosophers like to present their works as if everything before it was wrong. Sometimes, they even say they have ended the need for more philosophy. So, what happens when somebody realizes they were mistaken?
Sometimes philosophers are wrong and admitting that you could be wrong is a big part of being a real philosopher. While most philosophers make minor adjustments to their arguments to correct for mistakes, others make large shifts in their thinking. Here, we have four philosophers who went back on what they said earlier in often radical ways.
Numerous U.S. Presidents invoked the Insurrection Act to to quell race and labor riots.
- U.S. Presidents have invoked the Insurrection Act on numerous occasions.
- The controversial law gives the President some power to bring in troops to police the American people.
- The Act has been used mainly to restore order following race and labor riots.
It looks like a busy hurricane season ahead. Probably.
- Before the hurricane season even started in 2020, Arthur and Bertha had already blown through, and Cristobal may be brewing right now.
- Weather forecasters see signs of a rough season ahead, with just a couple of reasons why maybe not.
- Where's an El Niño when you need one?
Welcome to Hurricane Season 2020. 2020, of course, scoffs at this calendric event much as it has everything else that's normal — meteorologists have already used up the year's A and B storm names before we even got here. And while early storms don't necessarily mean a bruising season ahead, forecasters expect an active season this year. Maybe storms will blow away the murder hornets and 13-year locusts we had planned.
NOAA expects a busy season
According to NOAA's Climate Prediction Center, an agency of the National Weather Service, there's a 60 percent chance that we're embarking upon a season with more storms than normal. There does, however, remain a 30 percent it'll be normal. Better than usual? Unlikely: Just a 10 percent chance.
Where a normal hurricane season has an average of 12 named storms, 6 of which become hurricanes and 3 of which are major hurricanes, the Climate Prediction Center reckons we're on track for 13 to 29 storms, 6 to 10 of which will become hurricanes, and 3 to 6 of these will be category 3, 4, or 5, packing winds of 111 mph or higher.
What has forecasters concerned are two factors in particular.
This year's El Niño ("Little Boy") looks to be more of a La Niña ("Little Girl"). The two conditions are part of what's called the El Niño-Southern Oscillation (ENSO) cycle, which describes temperature fluctuations between the ocean and atmosphere in the east-central Equatorial Pacific. With an El Niño, waters in the Pacific are unusually warm, whereas a La Niña means unusually cool waters. NOAA says that an El Niño can suppress hurricane formation in the Atlantic, and this year that mitigating effect is unlikely to be present.
Second, current conditions in the Atlantic and Caribbean suggest a fertile hurricane environment:
- The ocean there is warmer than usual.
- There's reduced vertical wind shear.
- Atlantic tropical trade winds are weak.
- There have been strong West African monsoons this year.
Here's NOAA's video laying out their forecast:
ArsTechnica spoke to hurricane scientist Phil Klotzbach, who agrees generally with NOAA, saying, "All in all, signs are certainly pointing towards an active season." Still, he notes a couple of signals that contradict that worrying outlook.
First off, Klotzbach notes that the surest sign of a rough hurricane season is when its earliest storms form in the deep tropics south of 25°N and east of the Lesser Antilles. "When you get storm formations here prior to June 1, it's typically a harbinger of an extremely active season." Fortunately, this year's hurricanes Arthur and Bertha, as well as the maybe-imminent Cristobal, formed outside this region. So there's that.
Second, Klotzbach notes that the correlation between early storm activity and a season's number of storms and intensities, is actually slightly negative. So while statistical connections aren't strongly predictive, there's at least some reason to think these early storms may augur an easy season ahead.
Image source: NOAA
Batten down the hatches early
If 2020's taught us anything, it's how to juggle multiple crises at once, and layering an active hurricane season on top of SARS-CoV-2 — not to mention everything else — poses a special challenge. Warns Treasury Secretary Wilbur Ross, "As Americans focus their attention on a safe and healthy reopening of our country, it remains critically important that we also remember to make the necessary preparations for the upcoming hurricane season." If, as many medical experts expect, we're forced back into quarantine by additional coronavirus waves, the oceanic waves slamming against our shores will best be met by storm preparations put in place in a less last-minute fashion than usual.
Ross adds, "Just as in years past, NOAA experts will stay ahead of developing hurricanes and tropical storms and provide the forecasts and warnings we depend on to stay safe."
Let's hope this, at least, can be counted on in this crazy year.
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