Category: SCIENCE

If it weren’t for the intricate rules of quantum physics, we wouldn’t have formed neutral atoms “only” ~380,000 years after the Big Bang.

In order for you to exist, a lot of things had to happen beforehand. Planet Earth needed to come into existence, complete with the organic ingredients from which life could arise. In order to have those ingredients, we need for many previous generations of stars to have lived-and-died, recycling the elements formed within them back into the interstellar medium. For those stars to live, large quantities of neutral, molecular gas had to collect in one place, collapsing under its own gravity to fragment and form stars in the first place. But in order to make those stars — even the very first stars — we first need the Universe to create stable, neutral atoms.

In a Universe that begins with a hot Big Bang, this isn’t necessarily so easy! A few minutes after the hot Big Bang, our Universe was filled with protons and a small but important population of more complex light atomic nuclei, an equal number of electrons to the total number of protons, a large number of neutrinos that don’t interact with any of them, and about 1.4 billion photons for every proton-or-neutron present. (There’s also dark matter…

There’s an old saying that “what you see is what you get.” When it comes to the Universe, however, there’s often more to the full story.

Amazing sights abound all across the Universe.

But these ten examples are very different from what their appearances indicate.

10.) Apparently “merging” galaxy NGC 105.

The “smaller” galaxy, PGC 212515, is 100+ million light-years separated from NGC 105.

9.) “Globular cluster” NGC 411.

The fact that our Universe’s expansion is accelerating implies that dark energy exists. But could it be even weirder than we’ve imagined?

Our Universe, as we understood it, underwent a radical change at the end of the 20th century. We had long assumed — consistent with the evidence we had, mind you — that our Universe was taking part a great cosmic race that begun back at the start of the hot Big Bang. On the one hand, the Universe was born rapidly expanding, but on the other hand, the force of gravity worked to slow the expansion down and pull things back together. For most of the 20th century, the big question for cosmology was, “which impulse will win out in the end: gravitation or expansion?” Then, in 1998, we got our shocking answer: it will expand forever, but that’s because there’s a new type of energy that we didn’t expect, dark energy.

In the time since, we’ve ruled out alternative explanations and measured dark energy’s properties very well, but many questions still remain. In particular, despite all the ways that our knowledge of cosmology has changed in the 21st century, we still don’t know what dark energy is, or what its properties truly are. Could it be even stranger than most of us…

With stars, gas, and dark matter, galaxies come in a great array of sizes. This new one, Ursa Major III/UNIONS 1, is the smallest by far.

When it comes to the galaxies in the Universe, most of us think about the Milky Way and galaxies similar to it. After all, it is our galactic home, containing hundreds of billions of stars and spanning more than 100,000 light-years across. It’s an interesting fact that galaxies comparable in size to the Milky Way (as well as larger ones) hold the majority of stars present within the Universe today, but that they only represent about ~1% of all galaxies, overall. The majority of galaxies present in the Universe are:

• small,
• low in mass,
• contain very few numbers of stars, overall,
• but are dominated largely by dark matter.

Most of the galaxies in the Universe, because they’re small and contain very few stars within them, are also exceedingly difficult to detect: they’re also ultra-faint galaxies. It takes wide, deep surveys to reveal them at all, and even once they’re imaged, the stars within them need to be measured individually to determine that they’re all at the same distance, and that they’re all…

Just 10 years ago, humanity had never directly detected a single gravitational wave. We’re closing in on 300 now, with so much more to come!

It might seem hard to fathom, but it hasn’t even been ten full years since advanced LIGO, the gravitational wave observatories that brought us our very first successful direct detection, turned on for the very first time. In the time since, it’s been joined by the Virgo and KAGRA detectors, and humanity is currently closing in on 300 confirmed gravitational wave detection events. What was an unconfirmed prediction of Einstein’s General Relativity for a full century has now become one of the fastest-growing fields in all of astronomy and astrophysics.

For centuries, vaccines have been the top life-saving, expert medical intervention known to humans. How can individuals make the right call?

The United States used to be a very different place not so long ago. When a new child was born and was first taken to the doctor, the doctor would talk the parents through a schedule of expected care for the first few months and years of the newborn’s life. That expected care included, importantly a schedule for vaccines: a series of inoculations, given at pre-set times in a child’s development, that would protect them against diseases that had ravaged humanity for generations prior. This included protections against diseases such as:

• polio,
• smallpox,
• measles,
• rubella,
• mumps,
• diphtheria,
• pertussis (whooping cough),
• tetanus,
• hepatitis,
• typhoid,
• rabies,
• cholera,
• cervical cancer,
• bacterial meningitis,

Since 1998, we’ve known our Universe isn’t just expanding, but the expansion is accelerating. Could the Big Bang itself be the reason why?

Ever since the late 1990s, astrophysics has had a big puzzle to reckon with: one that still remains unsolved. When we try to solve Einstein’s field equations for General Relativity as they apply to our actual Universe — our Universe that, on large scales, is both isotropic, or the same in all directions, and homogeneous, or the same in all locations — we find that there’s a specific relationship between two things:

• the rate of the expansion of space, as well as how that rate changes over time,
• and the full suite of “stuff” that’s present within the Universe: matter, radiation, and any and all other forms of energy.

It was only in the late 1990s that we finally measured the expansion rate, and its change over time, well enough to conclude what type of “stuff” was present in the Universe, and what we found was shocking. While about ~30% of the Universe could be in the form of matter, the majority of it, around ~70%, was neither consistent with matter nor radiation. It needed to behave very differently: as a new form of energy.

For millennia, diamonds were the hardest known material, but they only rank at #7 on the current list. Can you guess which material is #1?

Carbon is one of the most fascinating elements in all of nature, with chemical and physical properties unlike any other element. With just six protons in its nucleus, it’s the lightest abundant element capable of forming a slew of complex bonds. All known forms of life are carbon-based, as its atomic properties enable it to link with up to four other atoms at a time, from the simplest such structure possible (methane) to incredibly rich molecules containing trillions of atoms or more. The possible geometries of those bonds also enable carbon to self-assemble, particularly under high pressures, into a stable crystal lattice.

If the conditions are just right, with impurity-free carbon and the needed pressures and temperatures, carbon atoms can form a solid, ultra-hard structure known as a diamond. Although diamonds are commonly known as “the hardest material in the world,” there are actually six materials that are harder. Diamonds are still one of the hardest naturally occurring (and, perhaps surprisingly, quite abundant) materials on Earth, and yet these six materials all have diamonds…

There are limits to where physics makes meaningful predictions: beyond the Planck length, time, or energy. Here’s why we can’t go further.

At all times and locations, the laws of physics endure.

Our Universe contains the Standard Model particles, plus whatever dark matter and dark energy are.

They interact via the four fundamental forces: gravity, electromagnetism, plus the two nuclear forces.

Extensions potentially exist: grand unification, string theory, supersymmetry, a “fifth force,” etc.

All stars shine due to an internal source of energy. Usually, it’s nuclear fusion: converting mass into energy. What makes them most bright?

Deep inside every star in the Universe, an incredible process occurs: the nuclear fusion of light elements and isotopes into heavier ones. Because heavier elements (at least, up to iron) have slightly lower rest masses than the sum of the light elements masses that fuse into them, the act of nuclear fusion in stars releases energy via Einstein’s most famous equation: E = mc². That energy powers the stars and causes them to shine, and as stars run out of a particular type of fuel in their cores, they evolve into the next stage of their lives until they run out of fuel entirely.

At least, that’s the conventional story you’ve likely heard. But it turns out that the tale I just related, although simplified, contains a number of common misconceptions that are present even among professional astronomers. I got the motivation to look a little deeper and clear some of these up after being prompted by a question from our reader Greg Hallock, who wrote to ask:

“I would like to know:
-how much mass typical stars convert to energy (relative to their total mass),
-[at] what points…