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Could this be the next great comet? To be sure, these words have been said lots of times before. In a clockwork sky, how comets will perform is always the great wildcard. Comets from Kohoutek to ISON have failed to live up to expectations, while others like W3 Lovejoy took us all by surprise. But a discovery this past weekend has message boards abuzz, as an incoming sungrazer could put on a show right around Halloween.

Anatomy of a Sungrazer

The discovery comes to us from the prolific Asteroid Terrestrial-impact Last Alert System (ATLAS), which first spotted the comet on the night of September 27th. The initial designation of the comet was A11bP7I. The comet now has an official designation: C/2024 S1 ATLAS. This was announced on October 1st, in the International Astronomical Union’s Central Bureau for Astronomical Telegram’s message 5453.

The orbit of Comet C/2024 S1 ATLAS. Credit: NASA/JPL.

The highly eccentric hyperbolic orbit of the comet suggests it’s a member of the Kreutz family group of sungrazer comets. Most of these comets are doomed for destruction at perihelion, but there have been a few exceptions over the years. Those sungrazers that have survived have gone on to become great comets.

Could C/2024 S1 ATLAS do the same?

Comet Caveats

Now, a few caveats are in order. Astronomers found S1 ATLAS at +12th magnitude, 1.094 Astronomical Units (AU) from the Sun. It could well be the case that it simply had an outburst right when it was first spotted, and could in fact be smaller and less energetic than it seems. What we need are more observations over the next few weeks.

Comet C/2024 ATLAS imaged shortly after discovery. Credit: Michael Jaeger.

“It’s early days, so I think the prudent approach is to moderate our expectations and then be ‘pleasantly surprised’ later,” astronomer Karl Battams (U.S. Naval Research Laboratory) told Universe Today. “That said, there’s clearly the potential for this to be a very exciting comet. The best analog we have is comet Lovejoy in 2011, which was discovered just a couple of weeks from perihelion, versus this one which is nearly a month away.”

Comet S1 ATLAS imaged on September 28th. Credit: Filipp Romanov.

The comet reaches perihelion on October 28th, 0.0082 AU from the Sun. That’s 762,600 miles from solar center, just 330,600 miles from the surface of the Sun. The solar radius is about 432,000 miles. As always seems to be the case, southern hemisphere observers will get a better view of the comet leading up to perihelion in mid-October as it approaches the Sun through the constellation Hydra. The comet will be visible low to the east at dawn, and ‘could’ break +6th magnitude in the final week of October. The comet passes 0.306 AU from the Earth on October 23rd after which, things could start to get interesting.

Prospects for Sungrazer A1 ATLAS

As of writing this, best estimates for peak magnitudes for comet S1 ATLAS top out at -7—think a bright daytime comet, but very close to the Sun—though -1st magnitude or so is probably more conservative.

Northern hemisphere viewers might get best views of the comet low to the east at dawn after perihelion… if it survives.

Looking low to the east at dawn on Halloween morning. Credit: Starry Night.

“This Kreutz-group comet won’t pass quite as close to the Sun as W3 Lovejoy, so it’s not unreasonable to guess that it will aid its survival potential.” Says Battams. “Assuming so, it might be briefly visible to northern hemisphere observers very low in the early morning (in) southeast skies after perihelion, but it would require good viewing circumstances (a clear, low horizon)… and won’t hang around there for long.”

A simulation of Comet A1 ATLAS in SOHO’s field of view. Credit: Starry Night.

The comet enters the Solar Heliospheric Observatory (SOHO’s) LASCO C2/C3 field of view on October 26th, and exits on the 29th. It’s strange to think: prior to SOHO’s launch in 1995, astronomers knew of less than a handful of sungrazer comets. Now, thanks to the mission, we know of 5,065 sungrazing comets and counting.

New sticky: I rarely tweet these days, mainly b/c most of the fun people have left. ? But I still pop in from time-to-time, and will post about exciting comet or Sun stuff.
As always, any images/data I post are from 100% public sources, and all opinions are solely mine. pic.twitter.com/OeQRia2ppU

— Karl Battams (@SungrazerComets) October 2, 2024

Classic Sungrazers of Yore

2011’s sungrazer W3 Lovejoy survived a passage just 87,000 miles from the surface of the Sun… Comet ISON, however, did not survive a 0.001244 AU, 116,000 mile surface pass at perihelion on U.S. Thanksgiving Day 2013.

Long-time comet watchers will remember sungrazer Ikeya-Seki, which survived a 280,000 mile pass (just a little over the Earth-Moon distance) from the surface of the Sun. That comet went on to dazzle observers in 1965.

Comet Ikeya-Seki. Credit: James W. Young/TMO/JPL/NASA.

“What I will say is that I am very excited at the ‘prospect,’ and will be watching the evolution of this extremely closely over the next couple of weeks.” says Battams. “I think by mid-October we’ll be able to state some facts with a lot more certainty.”

It seems like good comets always come in pairs…remember Hale-Bopp and Hyakutake in the late 90s? We (finally) caught sight of comet C/2023 A3 Tsuchinshan-ATLAS this morning from here in Bristol, Tennessee, looking like a fuzzy ‘star’ with a short tail in the brightening twilight low to the east, peeking out between pine trees.

We’re cautious for now when it comes to S1 ATLAS. But remember: comets never read predictions… and S1 ATLAS could well surprise us.

The post Could a New Sungrazer Comet Put on a Show at the End of October? appeared first on Universe Today.

We’ve known the Universe is expanding for a long time. The first solid paper demonstrating cosmic expansion was published by Edwin Hubble in 1929, based on observations made by Vesto Slipher, Milton Humason, and Henrietta Leavitt. Because of this, the rate of cosmic expansion is known as the Hubble constant, or Hubble parameter, H0. From this parameter, you can calculate things such as the age of the Universe since the Big Bang, so knowing the value of H0 is central to our understanding of modern cosmology.

Early on, the measured value of the Hubble parameter varied widely. Hubble’s initial value was on the order of 500 (km/s)/Mpc. By the 1960s, the value settled down to between 50 and 90 (km/s)/Mpc, where it stayed for most of the 20th century. It was difficult to get more precise because our methods of calculating it were limited. All of these were based on the cosmic distance ladder, which uses a series of observations to calculate ever greater cosmic distances, each building on the previous method. But in the past few decades we got pretty good at it, and the Hubble value seemed to settle around 70 (km/s)/Mpc. After that, things started to get…problematic.

With satellites such as WMAP and Planck we started to get high-resolution maps of the cosmic microwave background. From fluctuations in this background we have a new way to measure H0 and get a value of 67 – 68 (km/s)/Mpc. At the same time, observations of distant supernovae and the cosmic distance ladder pin down the value to 73 – 75 (km/s)/Mpc. Both methods are quite precise, and yet they entirely disagree. This disagreement is now known as the Hubble tension problem, and it is the most bothersome mystery in cosmology.

Hubble tension between methods. Credit: Wikipedia user Primefac

We aren’t sure what causes the Hubble tension. It might mean that one or more of our observation methods are fundamentally flawed, or it might mean there is something about dark energy and cosmic expansion that we really don’t understand. But astronomers generally agree that one way to address this mystery is to look for ways to measure H0 that are independent of both the cosmic background and the cosmic distance ladder. One such method involves gravitational lensing.

Gravitational lensing occurs because gravity warps space, meaning that the path of light can be deflected by the presence of a large mass. So, for example, if a distant galaxy happens to be behind a closer galaxy from our vantage point, we see a gravitationally distorted view of the distant galaxy or even multiple images of the galaxy. The interesting thing about the multiple image effect is that the light from each image travels a different path around the closer galaxy, each with a different distance. Since the speed of light is finite this means each image gives us a view of the galaxy at different times in history.

This doesn’t matter much for galaxies, but for supernovae it means gravitational lensing can let us observe the same supernova multiple times. By calculating the path of each supernova image we can determine the relative distance of each path, and by timing the appearance of each image we can determine the actual distance. This gives us a measurement that is independent of the cosmic distance ladder, giving us a new way to measure the Hubble parameter. This method has been used a couple of times, but the uncertainties of their Hubble values weren’t small enough to address the Hubble tension. However, a new study using this method is precise enough.

The study is based on JWST images of a Type Ia supernova named SN H0pe. It is one of the most distant supernovae ever observed, and thanks to the less-distant galaxy cluster G165, the team captured three lensed images of SN H0pe. With their timing, observed brightness, and calculated paths, the team calculated H0 to be 70 – 83 (km/s)/Mpc. This still has a higher uncertainty than other methods, but it agrees with the usual distance ladder method. It also clearly disagrees with the cosmic microwave background method.

Despite H0pe, the Hubble tension is very real. If anything, this new result makes the issue even more troublesome. There is something about cosmic expansion we don’t understand, and it’s now clear that better observations will not solve this mystery on their own.

Reference: Pascale, Massimo, et al. “SN H0pe: The First Measurement of H0 from a Multiply-Imaged Type Ia Supernova, Discovered by JWST.” arXiv preprint arXiv:2403.18902 (2024).

The post Gravitational Lens Confirms the Hubble Tension appeared first on Universe Today.

The first 18 satellites of a planned Chinese mega constellation are brighter than all but 500 stars in the sky, raising fears of a huge impact on astronomy

Mathematicians have developed a recipe for upgrading quantum computers to simulate complex quantum systems, such as molecules. Their discovery brings us closer to being able to predict how new drugs will behave within our bodies and has the potential to revolutionize pharmaceutical development.

Increasingly complex applications such as artificial intelligence require ever more powerful and power-hungry computers to run. Optical computing is a proposed solution to increase speed and power efficiency but has yet to be realized due to constraints and drawbacks. A new design architecture, called diffraction casting, seeks to address these shortcomings. It introduces some concepts to the field of optical computing that might make it more appealing for implementation in next-generation computing devices.

Increasingly complex applications such as artificial intelligence require ever more powerful and power-hungry computers to run. Optical computing is a proposed solution to increase speed and power efficiency but has yet to be realized due to constraints and drawbacks. A new design architecture, called diffraction casting, seeks to address these shortcomings. It introduces some concepts to the field of optical computing that might make it more appealing for implementation in next-generation computing devices.

Deposits of ice in lunar dust and rock (regolith) are more extensive than previously thought, according to a new analysis of data from NASA's LRO (Lunar Reconnaissance Orbiter) mission. Ice would be a valuable resource for future lunar expeditions. Water could be used for radiation protection and supporting human explorers, or broken into its hydrogen and oxygen components to make rocket fuel, energy, and breathable air.

Physicists have succeeded in coupling two Andreev qubits coherently over a macroscopic distance for the first time. They achieved this with the help of microwave photons generated in a narrow superconducting resonator. The results lay the foundation for the use of coupled Andreev qubits in quantum communication and quantum computing.

Physicists have succeeded in coupling two Andreev qubits coherently over a macroscopic distance for the first time. They achieved this with the help of microwave photons generated in a narrow superconducting resonator. The results lay the foundation for the use of coupled Andreev qubits in quantum communication and quantum computing.

A chip-based 'tractor beam' can trap and manipulate biological particles using a tightly focused beam of light emitted from a silicon-photonics chip. The device could help biologists and clinicians study DNA, classify cells, and investigate the mechanisms of disease.

A chip-based 'tractor beam' can trap and manipulate biological particles using a tightly focused beam of light emitted from a silicon-photonics chip. The device could help biologists and clinicians study DNA, classify cells, and investigate the mechanisms of disease.

A new study has demonstrated a new, non-invasive imaging technique can accurately detect clear-cell renal cell carcinoma, the most common form of kidney cancer.

A monkey that performed poorly on vision tests did much better after having a stem cell transplant to patch up holes in its retina

As I mentioned this morning, the BearCam at Brooks Falls in Katmai National Park in Alaska is a wonder to behold: it’s full of grizzly bears (also known as the North American brown bear) standing in the water—both above and below the falls—trying to grab salmon as the fish struggle over the falls to the mating area.

There are tussles for position among the bears, growling, and lots of failed attempts to catch salmon. (There are several BearCams, and the view changes from time to time.) Nevertheless, each bear gets up to 20 salmon per day, packing on the pounds for winter hibernation. You can vote for the bear that’s gotten the fattest over at the Fat Bear Contest site. Meanwhile, click on the live BearCam below to see the action. I’ve enclosed a screenshot, and just click on it to go to the BearCam.

Some day I must make it there; it’s on my bucket list.

The feed begins when it gets light in Alaska; at other times they show “highlights”:

A computer simulation suggests that some collisions between exotic, hypothetical stars would make space-time ripple with detectable waves

A traditional yogurt-making practice from south-eastern Europe uses live ants as a starter, with the insects providing the bacteria and acid needed to initiate fermentation

Bill Ackman is the billionaire hedge-fund manager who not only publicized the drop of donations to Harvard because of its purported antisemitism, but also helped bring down President Claudine Gay. But he’s also a double Harvard alum; as Wikipedia notes:

In 1988, he received a Bachelor of Arts degree magna cum laude in social studies from Harvard College. His thesis was titled “Scaling the Ivy Wall: The Jewish and Asian American Experience in Harvard Admissions”.  In 1992, he received a Master of Business Administration degree from Harvard Business School.

But Ackman’s not a rapacious piker. Wikipedia adds this:

Ackman is a signatory of The Giving Pledge, committing himself to give away at least 50% of his wealth by the end of his life to charitable causes.  He has given to charitable causes such as the Center for Jewish History, where he spearheaded a successful effort to retire $30 million in debt, personally contributing $6.8 million.  The donation, along with those of Bruce Berkowitz, founder of Fairholme Capital Management, and Joseph Steinberg, president of Leucadia National, were the three largest individual gifts the center has ever received.  Ackman’s foundation donated $1.1 million to the Innocence Project in New York City and Centurion Ministries in Princeton, New Jersey.

Apparently Ackman gave an invited talk about the Harvard Corporation, couched in financial jargon. Here’s the tweet with the slides. I’ll highlight some of them, which are pretty damning for Harvard.

Jim Grant asked me to give a talk on “@Harvard Corporation, Buy, Sell or Hold.” I complied.

The slides:https://t.co/dNWFlb2RSu

— Bill Ackman (@BillAckman) October 1, 2024

There are 49 slides, and they pretty much encompass his thesis, which is that Harvard has become a business aimed not at providing a quality education to students, but to enriching the Corporation, and its mission has changed from promoting learning to pushing a “progressive” ideology.  In the process, it’s become woke and bloated with administrators.  But Ackman does seem some glimmers of hope on the horizon.

Here are some slides that support that thesis. First, a financial summary and the avowed mission of the College.

Here are some figures taken over the last 20 years:

Yet look at this administrative bloat! Why do they neeed so many administrators (in 20 years the administration has grown by 42% while student enrollment has grown by 0.3% and faculty by 0.5%:

And the cost of going to Schmarvard has doubled, “far outpacing inflation”. The cost of living over this period has increased only 61%. The tuition and fees this year are about $83,000 per annum, so a four-year education costs over a third of a million bucks.

Yet Harvard’s endowment has also more than doubled over this period, and is now 51 BILLION dollars. Ackman’s conclusion:

Here are three of Ackman’s plaints (he’s a registered Democrat but appears to support Trump). I can’t verify the first one (Ackman’s figures are likely accurate), but we all know about the second.  As for the slide just below, Harvard is probably LESS liberal than other schools, but we know that the dearth of conservative viewpoints (just 3% of faculty) is a general issue. Whether you consider that a problem, and if so, how to remedy it—these are matters for debate.

Last year Harvard was last in FIRE’s free-speech ranking, now it’s sixth from last:

Grade inflation is something I abhor, but it seems unstoppable; it’s part of the Alice in Wonderland view that “all must have prizes,” and a sign of the devaluing of merit. It cannot be that students have gotten so much smarter in 20 years! No, grading has gotten easier.

He then shows a series of slides explaining what has happened to Harvard.  This is the summary: it’s become woke and its mission has become woker, conforming to the ideology of the day rather than seeking truth and knowledge.  You can find the new mission statement below:

The latest mission statement, showing the emphasis on diversity, and it doesn’t mean intellectual diversity. The emphasis is on social diversity, coming from “different walks of life,” and having “different identities.” These differences, asserts Schmarvard, will perforce YIELD “intellectual transformation.”

There follows a series of slides showing that while the “demand” of students for education in economics and computer science has grown modestly (as well as the number of faculty in these areas and the number of degrees conferred), the faculty in “studies” departments has grown much faster.  But the number of degrees conferred in “studies” has decreased sharply.. Ackman concludes that Harvard is allocating its resources according to an ideological, diversity-centered platform.

He supports this by giving an analysis of the words used in Harvard’s course catalogue, presumably reflecting its curriculum:

Truth is mentioned much less often than Gender or “oppression”.

Ackman does note that the interim President (Garber will be there for three more years) has done some good things:

From all of this, and assessing Harvard as an “investment” (possibly aimed at potential donors), Ackman regards the College as a “hold”:

I largely agree with Ackman about Harvard, though the problems he singles out, like grade inflation and an ideological bent, also plague other schools. But Ackman, like me, went to Harvard, and we share a sentimentality about the place that lingers (I had a terrific time and got a terrific education in its grad school).  So here’s his reply when someone questions him about why, given all these problems, Harvard is a “hold” rather than a “sell”:

 

So I am sentimental.

— Bill Ackman (@BillAckman) October 2, 2024

The epilepsy medication sodium valproate is linked to developmental problems in fetuses, but lab studies may now have found a way to prevent this

This is my second post on the subject of why “the speed of light (in empty space)”, more accurately referred to as “the cosmic speed limit”, is so fast. This speed, denoted c, is about 186,000 miles (300,000 km) per second, which does indeed seem quick.

But as I pointed out in my first post on this subject, this isn’t really the right question, because it implicitly views humans as centrally important and asks why the cosmos as strange. That’s backward. We should instead ask why we ourselves are so slow. Not only does this honor the cosmos properly, making it clear that it is humans that are the oddballs here, this way of asking the question leads us to the answer.

And the answer is this: ordinary atomic material, from which we are made, is fragile. If a living creature were to move (relative to the objects around it) at speeds anywhere close to c, it couldn’t possibly survive its first slip and fall, or its first absent-minded collision with a door frame.

Today I’ll use a principled argument, founded on basic particle physics and its implications for atomic physics, to show that any living creature made from atoms will inevitably view the cosmic speed limit as extremely fast compared to the speeds that it ordinarily experiences.

In the next post I’ll try to go further, and suggest that we must travel at even slower speeds. However, doing so becomes increasingly difficult. We potentially have to get into details of materials, of chemistry, of biology real and imagined, and of the specifics of the Earth. Once we enter this territory, the issues become complex, the logic and conclusions may be debatable, and I’m no longer expert enough to be sure I know what I’m doing. Perhaps readers can help me with that stage when we get to it.

By contrast, the logic presented here today is straightforward and impossible to evade. Along the way it will also teach us why nuclear weapons are so terrifying — why the energy hidden inside atomic nuclei is so much larger than the energies we encounter in our daily activities.

There are a lot of elements to the reasoning, so what I’ll give here is an overall sketch. But you’ll find many more details in the hyperlinks to other pages, some on this website and some beyond.

All Atomic Creatures Will View “c” As Fast

The argument is based on two simple observations about atoms, which I’ll combine in two ways to derive facts about energy and speed. All numbers given below will be very approximate, because we don’t need precision to draw the general conclusion, and trying to be more precise would make the argument longer without making it clearer. (See chapter 6.1 of my book for a discussion of physicists’ “rules of precision”.)

1. The Electromagnetic Force Makes Atoms’ Outer Electrons Slow

The electromagnetic force is a moderately weak force by particle physics standards (despite being much stronger than gravity). It has only about 1% of the strength of what we’d consider a reasonably strong force. As a direct result, the electron in a hydrogen atom moves around the atom at a speed v that is far below c — approximately 1% of c. (See also this article and this article.)

The electrons on the very outer edge of any atom (the “valence electrons”) are affected by an attractive electric force from the positively charged nucleus, but are also repelled by the electric force from all the inner electrons, which have negative charge. The net effect is that positive charge of the nucleus is substantially shielded by the negative charge of the electrons, and the resulting force on the valence electrons is not dramatically different from that found in a hydrogen atom. As a result, these valence electrons are somewhat similar to the one electron in hydrogen, and so they too move around at about 1% of c, typically a bit slower. (This “1%” is very imprecise, but it’s never as small as 0.1%.)

Thus for any atom, the outer electrons have

Here the “~” sign means “is very roughly equal to,” indicating purposeful imprecision. From this we can estimate the typical energy required to disrupt the atom — the “first ionization energy“. That energy is the combination of

• the valence electron’s motion energy 1/2 mv2 and
• the “binding energy” that holds that electron to the atom.

The motion energy and binding energy are similar in size. (This is always true for any force that decreases as 1/(distance-squared), including electric and gravitational forces.) As a result, the first ionization energy is close to the valence electron’s motion energy 1/2 mv2. Just as for a hydrogen atom, this energy is always about 1/10000th, or 0.01%, of the internal E=mc2 energy of an electron. In math terms, the fact that v/c ~ 0.01 for a typical valence electron implies that the ionization energy divided by the electron’s internal energy is roughly

Let me just emphasize again that I’m not being precise because precision isn’t needed for this argument.

Aside: Those of you who know a little quantum physics know that v isn’t really defined for an electron, because it’s a wavicle, not a particle, and that electrons don’t really go around their nuclei in orbits, despite the picture of an atom that’s so often drawn. I’m using Bohr’s cartoon of an atom here, which is enough to get the right estimates for what is going on. But we could do things correctly, and avoid ever writing “v,” by just using the ionization energy all the way through the argument. We’d get the same answer in the end.

2. The Strong Nuclear Force Gives Atoms a Big Mass

An atom has a nucleus at its center, consisting of between 1 and about 300 protons and neutrons. The strong nuclear force forms the protons and neutrons by tightly trapping quarks, anti-quarks and gluons. It then subsequently binds protons and neutrons, somewhat more loosely, into nuclei.

The most common materials, which are forged in the early universe and in ordinary stars, run mainly from hydrogen (1 electron and 1 proton) to iron (26 electrons, 26 protons, and typically 30 neutrons). Since neither hydrogen nor helium is suitable on their own for making life forms, as their chemistry is too simple, it’s reasonable to define a “typical atom” as one with roughly 10 or so protons and neutrons in its nucleus. (Carbon usually has 12, oxygen 16, etc.)

Now we need to take note of three different and unrelated aspects of particle physics.

• The strong nuclear force becomes extremely strong at a distance D that is about 1/100000th of an atom’s diameter. This sets the size of protons and neutrons, and assures they have almost the same mass Mp. That mass, about equal to the mass of a single hydrogen atom, is related to D by the formula Mp ~ h/(cD), where c is the cosmic speed limit and h is Planck’s constant, the mascot of quantum physics.
• The value <H> of the Higgs field corresponds to a mass about 250 times larger than that of a proton,
• The interaction of the Higgs field with electrons is tiny, and characterized by a number called “ye” which is about 1/400000.

Combining the last two tells us the electron’s mass, m ~ ye<H>, is very small compared to the majority of known elementary particles.

Taking all three facts together (which are independent as far as we know [none of them can yet be predicted from first principles]), it turns out that

(More precisely, the proton’s mass is nearly that of 1836 electrons, and the neutron’s 1838; but 2000 is close enough for our current purposes.)

Therefore, for a typical atom with mass M ~ 10 Mp , the ratio of the atom’s mass to the electron’s mass m, which is also the ratio of the energy stored inside that atom to the energy stored inside a single electron, is

Again, this all follows from known facts about subatomic particles. It isn’t something that anyone can explain from scratch, but for our purposes, it’s enough to know that it is true. Let’s see what the consequences are.

3. Atoms with Slow Electrons and a Large Mass are Fragile

Combining sections 1. and 2., let’s compare amount of energy that it takes to pull an outer electron off a typical atom (its first ionization energy), which is approximately equal to the motion-energy 1/2 mv2 of the electron, to the energy Mc2 stored inside that atom:

• 
  
  

Thus the amount of energy needed to disrupt an atom is a minuscule fraction of the energy that it carries inside it. Atoms are very fragile indeed!

This now explains why the energies of ordinary life must be so small compared to the energy stored in objects, and why nuclear weapons can draw on so much more energy than we are used to. If the energy per atom involved in ordinary activities, such as catching a ball or jumping up and down, were any more than a tiny fraction of the energy stored inside an atom, many of our atoms would lose one or more electrons right away, instantly ruining our biochemistry and destroying our internal structure. We can only survive because the energy of ordinary life is tiny compared to what the cosmos considers normal.

4. Fragile Atoms Can’t Survive Fast Collisions

A head-on collision between two typical atoms with mass M, each with speed V, will involve energy 1/2 MV2 for each atom. If this collision energy is comparable to or exceeds the energy needed to disrupt either atom, which is about 1/2 mv2 (where as before m is the mass of an electron and v is the speed of a valence electron in the atom) then at least one of the atoms will probably lose an electron. So to avoid this, it must be that

• 
  
  

where in the second line I used the result from section 3. Taking the square root of this line, we find

Thus atoms cannot survive intact in any collision whose relative speed is comparable to or faster than 0.00005 c — about 10 miles (15 km) per second. In any collision of ordinary objects at such a speed, the collisions of their individual atoms will lead to widespread atomic disruption, leaving the objects seriously damaged.

Aside: as noted, I have been imprecise all throughout this argument. The true maximum speed for the survival of typical atomic materials may be somewhat slower than 0.00005 c — but not too much so. Perhaps a reader can suggest a more precise estimate?

5. Life (and Anything Else) Made From Atoms Must Move Gingerly

Therefore, for living creatures to avoid injuring themselves irreparably at the atomic level every time they stub their toe or accidentally bump in to one another, they must travel slowly. Relative to objects in their environment, they dare not travel faster than 10 miles (15 km) per second at all times — much less than a 1/10000th of the cosmic speed limit.

And therefore, when they first discover the existence of c, they will all, without exception, express surprise and amazement at how fast it is — more than 10000 times faster than the motions of their ordinary existence.

Humans and Tardigrades

Now, of course, you and I are restricted to much slower speeds than 10 miles (15 km) per second! Even a collision at 10 feet (3 meters) per second, about 7 miles (11 km) per hour, will hurt a lot, and speeds ten times that would surely be fatal. For us, c isn’t just 10,000 faster than what we’re used to — it’s about 100,000,000 times faster than jogging speed!

So clearly this argument gives an overestimate of how fast we can go. There must be additional issues that force us to move even more slowly than the speeds that would disrupt atoms. This is true, but those constraints are much more complicated. That’s why I decided to begin with this relatively simple and very general argument.

What’s good about this argument is that it applies to all atomic objects. It restricts not only natural life on Earth but all imaginable atomic life anywhere — even artificial life that we or some other species might potentially create.

Many organisms are far stronger than we are, tardigrades most famously among them. (Note that tardigrades are small, but not microscopic.) We’ve been making robotic machines for quite some time that can survive and thrive in environments that would kill us instantly. Current technology can already create simple artificial life forms.

Nevertheless, no matter how good our technology, and no matter how intricate the unconscious process of evolution, we will never encounter or construct complex objects that can remain intact in environments where relative speeds are as high as 1/10000th of c, unless

• they remain forever isolated in deep space, where collisions with any large objects are extremely unlikely, and collisions with atoms are infrequent enough that the resulting surface damage is manageable [which is why our spacecraft, not to mention asteroids and planets, are able to travel safely much faster than Earthly objects do], or
• we someday find a building block stronger than atoms from which a robot or artificial life form can be built [but given what we know about the universe so far, this may forever remain science fiction.]

Here’s an interesting and relevant piece of information: it has been shown that frozen tardigrades can survive collisions with sand at tremendously higher speeds than we humans can handle, but only up to about 0.6 miles (0.9 km) per second — about 1/300000th of c. (This makes it challenging for them to travel successfully between planets and moons across the solar system, where typical relative speeds of large objects and meteors are in the 10 km/second range.) On the one hand, this shows that at least some life forms can survive much more rapid collisions than we can. On the other, they have limitations that are consistent with today’s reasoning.

Could one could create a intelligent creature of a larger size that could match the durability of a tardigrade? That is perhaps doubtful, but we can discuss that after the next post.

Slow is Better

Thus by combining basic knowledge concerning our universe —

• the moderate weakness of the electromagnetic force,
• the great strength and trapping ability of the strong nuclear force,
• the substantial value of the Higgs field,
• the tiny interaction of the Higgs field with electrons,
• the nature of typical atomic nuclei, and
• the behavior of valence electrons in typical atoms —

we learn that any object made from atoms cannot endure collisions at speeds anywhere close to c. And now we know the reason why the cosmic speed limit seems so fast — and why nuclear weapons seem so violent.

The reason is simple: in this universe, only the slow survive.

It is now generally accepted that 66 million years ago a large asteroid smacked into the Earth, causing the large Chicxulub crater off the coast of Mexico. This was a catastrophic event, affecting the entire globe. Fire rained down causing forest fires across much of the globe, while ash and debris blocked out the sun. A tsunami washed over North America – one site in North Dakota contains fossils from the day the asteroid hit, including fish with embedded asteroid debris. About 75% of species went extinct as a result, including all non-avian dinosaurs.

For a time there has been an alternate theory that intense vulcanism at the Deccan Traps near modern-day India is what did-in the dinosaurs, or at least set them up for the final coup de grace of the asteroid. I think the evidence strongly favors the asteroid hypothesis, and this is the way scientific opinion has been moving. Although the debate is by no means over, a majority of scientists now accept the asteroid hypothesis.

But there is also a wrinkle to the impact theory – perhaps there was more than one asteroid impact. I wrote in 2010 about this question, mentioning several other candidate craters that seem to date to around the same time. Now we have a new candidate for a second KT impact – the Nadir crater off the coast of West Africa.

Geologists first published about the Nadir crater in 2022, discussing it as a candidate crater. They wrote at the time:

“Our stratigraphic framework suggests that the crater formed at or near the Cretaceous-Paleogene boundary (~66 million years ago), approximately the same age as the Chicxulub impact crater. We hypothesize that this formed as part of a closely timed impact cluster or by breakup of a common parent asteroid.”

Now they have published a follow up study, having been given access to private seismic data that allows for a detailed 3D analysis of the crater site. This is important because of how scientists identify impact craters. The gold standard is to identify physical evidence of impact, such as shock crystals. There are telltale minerals that can only be formed by the intense sudden power of an impact, or that form when debris is thrown into the high atmosphere while molten and then rains back down. These are conclusive signs of an impact. But there are many somewhat circular structures in the world, and often they may be prematurely declared a crater without solid evidence. So geologists are cautious and skeptical.

For the Nadir crater, which is on the sea floor, we do not have physical evidence. The initial study showed that it has a candidate circular structure, but this was not enough evidence to convince the scientific community. The detailed new analysis, however, is more compelling. First the scientists find that it does have a complete circular structure consistent with an impact basin. Even more significant, however, is that they have documented a “central uplift”, which is a characteristic sign of an impact crater. When asteroids hit they cause a depression and liquify the underlying rock. This causes a shockwave which rebounds, causing the molten rock to uplift in the center of the crater, leaving behind an uplift. This means that a circular basin with an uplift in the exact middle is a signature of an impact. This is solid and convincing evidence, even without the physical evidence of impact crystals. They write:

“Our new study published in Communications Earth & Environment 3 presents this new, state-of-the-art 3D data, revealing the architecture of the crater in exceptional detail and confirms (beyond reasonable doubt!) an impact origin for the crater. This is the first time that an impact structure has ever been imaged fully with high-resolution seismic data like this and it is a real treasure trove of information to help us to reconstruct how this crater formed and evolved.”

Sounds pretty convincing. But this leaves the questions they raised in their study two years ago – did this asteroid hit at the exact same time as the Chicxulub asteroid? If not, how far apart were they? If they did hit at the same time, were they originally part of the same asteroid? Given that there are other candidate craters that date to the same period of time, perhaps the asteroid broke up into multiple pieces that all struck the Earth at the same time.

If these asteroids were not originally part of the same asteroid, then what are the other possibilities? It is possible, although statistically unlikely, that there were simply different independent major impacts within a short time of each other. There is nothing to keep this from happening, and given the history of life on Earth perhaps it’s not that surprising, but it would be a statistical fluke.

The other possibility is that, even if they were different asteroids, perhaps there was some astronomical event that caused multiple chunks of rock and ice to swarm into the inner solar system. This would have caused a temporary period of relatively high bombardment. Perhaps a rogue planet swung by our solar system, scattering material from the Kuiper belt, some of which found its way to Earth.

The authors propose to drill into this structure, to get that physical evidence that would be so helpful. Not only would this confirm its impact status, but we may be able to tell if the chunk of rock that caused the Nadir crater has the same mineral signature as the Chicxulub asteroid. I suspect we could also tell their relative timing. Perhaps we could see the iridium layer from the Chicxulub impact, and see how that relates to the Nadir impact.

We may be able to answer – were the dinosaurs just really unlucky, or was the Chicxulub impact event more devastating than we even realized? Either way I look forward to more scientific investigation of the Nadir crater.

The post Nadir Crater – A Double Tap for Dinosaurs? first appeared on NeuroLogica Blog.