Wednesday, July 17, 2024

Why humanity is a cosmic tale of despair and hope

On the scale of the Universe, humanity isn’t even a speck.

This vertically oriented logarithmic map of the Universe spans nearly 20 orders of magnitude, taking us from planet Earth to the edge of the visible Universe. Each large “mark” on the right side’s scale bar corresponds to an increase in distance scales by a factor of 10.

Credit: Pablo Carlos Budassi

We’re each just a tiny, minuscule fraction of our own planet: Earth.

Apollo 8 astronauts were the first humans to reach great enough distances from our planet to be able to view the entire Earth at once. Here, the closest (left) and farthest (right) images of the Earth are shown as acquired with the same Hasselblad camera. Except for the three humans on board at the moment, all of humanity is confined to the pale, blue dot on the right.

Credit: NASA/Apollo 8/Johnson Space Center

It would take nearly an Avogadro’s number of humans to equal Earth’s mass.

ideal night sy conditions

Under ideal dark sky conditions, the unaided human eye can see up to 6000 stars at once, and up to 9000 stars total if they could see the full sky at once, unblocked by the Earth itself. Compared to the Earth, at ~6 septillion kilograms, all 8+ billion humans, combined, are barely a drop in the bucket of planet Earth’s total mass.

Credit: callisto / Adobe Stock

Earth is just one modest planet orbiting our Sun: one of ~400 billion stars within the Milky Way.

star metallicity throughout the Milky Way

This color-coded map shows the heavy element abundances of more than 6 million stars within the Milky Way. Stars in red, orange, and yellow are all rich enough in heavy elements that they should have planets; green and cyan-coded stars should only rarely have planets, and stars coded blue or violet should have absolutely no planets at all around them. Note that the central plane of the galactic disk, extending all the way into the galactic core, has the potential for habitable, rocky planets. This map shows fewer than 0.01% of the stars within our galaxy.

Credit: ESA/Gaia/DPAC; CC BY-SA 3.0 IGO

Our Milky Way is second to Andromeda within our Local Group of galaxies.

Our Local Group of galaxies is dominated by Andromeda and the Milky Way, but there’s no denying that Andromeda is the biggest, the Milky Way is #2, Triangulum is #3, and the LMC is #4. At just 165,000 light-years away, it’s by far the closest among the top 10+ galaxies to our own, and as such it takes up the largest angular span on the sky of all galaxies outside the Milky Way. There are over 100 galaxies within the Local Group, but Andromeda and the Milky Way contain most of the stars, as well as most of the mass.

Credit: Andrew Z. Colvin/Wikimedia Commons

Beyond the Local Group, much larger, richer, more massive groups and clusters of galaxies abound.

An image of El Gordo, a massive galaxy cluster captured by Hubble

This 2014 composite Hubble image of the colliding galaxy cluster, El Gordo, showcases the most massive galaxy cluster ever discovered from the first half of our cosmic history. Known officially as ACT-CLJ0102-4915, it is the largest, hottest, and X-ray brightest galaxy cluster ever discovered in the distant Universe, containing many thousands of times the mass of the Local Group.

Credit: ESA/Hubble & NASA, RELICS

Altogether, trillions of galaxies are strewn throughout the observable, expanding Universe.

regions of the universe

In a Universe that comes to be dominated by dark energy, there are four regions: one where everything within it is reachable, communicable and observable, one where everything is observable but unreachable and incommunicable, one where things will someday be observable but aren’t today, and one where things will never be observable. The labeled numbers correspond to our consensus cosmology as of 2024, with boundaries of 18 billion light-years, 46 billion light-years, and 61 billion light-years separating the four regions. On scales of ~10 billion light-years and larger, the Universe is almost perfectly uniform.

Credit: Andrew Z. Colvin/Wikimedia Commons; annotations: E. Siegel

Owing to dark energy, news of humanity’s greatest exploits will never reach practically all of them.

A diagram of the solar system illustrates the heliosphere, detailing the termination shock, heliopause, and bow shock, along with the paths of Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2. This visual representation underscores key aspects of fundamental science in our cosmic neighborhood.

This 1997 artwork shows the planets of the Solar System and the relative trajectories of the first four spacecraft on a course to exit the Solar System. In 1998, Voyager 1 overtook Pioneer 10, and in 2012, it passed the heliopause and entered interstellar space. Voyager 2 entered interstellar space in 2018 and recently surpassed Pioneer 10’s distance in 2023; therefore we strongly suspect that Pioneer 10 is in interstellar space as well, but it is no longer functional, so we cannot make the critical measurements necessary to make such a determination.

Credit: NASA

And yet, from a different perspective, we truly are remarkable.

30 protoplanetary disks, or proplyds, as imaged by Hubble in the Orion Nebula. Hubble is a brilliant resource for identifying these disk signatures in the optical, but has little power to probe the internal features of these disks, even from its location in space. Radio telescopes like ALMA, as well as infrared observatories like the VLT and JWST, are far superior at that aspect of measuring these details. Planets largely arise from protoplanetary disks, but different mechanisms might be responsible for different planetary formation scenarios at various distances from the parent star.

Credit: NASA/ESA and L. Ricci (ESO)

We inhabit a rocky world, formed from ancient stellar ashes.

An artistic representation of possible first life in the form of organic molecules near a cosmic object with a stellar background.

This conceptual image shows meteoroids delivering all five of the nucleobases found in life processes to ancient Earth. All the nucleobases used in life processes, A, C, G, T, and U, have now been found in meteorites, along with more than 80 species of amino acids as well: far more than the 22 that are known to be used in life processes here on Earth. Similar processes no doubt happened in stellar systems all throughout most galaxies over the course of cosmic history, bringing the raw ingredients for life to all sorts of young worlds.

Credit: NASA Goddard/CI Lab/Dan Gallagher

For some ~4 billion years, continents and oceans have persisted on Earth’s surface.

hydrothermal field

This aerial view of Grand Prismatic Spring in Yellowstone National Park is one of the most iconic hydrothermal features on land in the world. The colors are due to the various organisms living under these extreme conditions, and depend on the amount of sunlight that reaches the various parts of the springs. Hydrothermal fields like this are some of the best candidate locations for life to have first arisen on a young Earth, and may be home to abundant life on a variety of exoplanets.

Credit: Jim Peaco/National Parks Service

Life emerged early on Earth, surviving and thriving ever since.


This tunneling electron microscope image shows a few specimens of the cyanobacterium species Prochlorococcus marinus. Each one of these organisms is only about half a micron in size, but all together, cyanobacteria are largely responsible for the creation of Earth’s oxygen: both initially and largely even during the present day. Like all bacteria, their lifetime is much, much shorter than the lifetime of a human, and while cyanobacteria are relatively primitive organisms, they “only” date back to no earlier than 2.7 billion years ago, whereas life on Earth goes back more than a billion years, at least, farther than this.

Credit: Luke Thompson from Chisholm Lab and Nikki Watson from Whitehead, MIT

Multicelluarity, sexual reproduction, complexity, and high levels of differentiation eventually arose.

A translucent sea creature, showcasing the complex beauty of life on Earth, with a chain of bead-like structures against a black background.

A fascinating class of organisms known as siphonophores is itself a collection of small animals working together to form a larger colonial organism. These lifeforms straddle the boundary between a multicellular organism and a colonial organism. The ability of single life forms to combine features such as multicellularity, complexity, and high levels of differentiation have led to the explosive diversity of life that has abounded on Earth for the past ~500 million years.

Credit: Kevin Raskoff, Cal State Monterey; Crisco 1492/Wikimedia Commons

Within ourselves, an organ powers “thought” like no other: the human brain.

Illustration of various primate skulls, including human, showing comparative anatomy when humans arose.

This drawing shows a variety of human, monkey, and ape skulls from a variety of extant species. The older apes have smaller cranial capacities and smaller brains than humans, but stronger jaws, on average, by far. In order for large brains to develop, the jawbones needed to weaken: a loss-of-function adaptation. Modern humans have the greatest encephalization quotient of all known animals, followed by dolphins and then, more distantly, chimpanzees and some birds.

Credit: schinz de Visser, 1845/public domain

After 13.8 billion years, civilized humans finally comprehend our Universe.

This colorful view of the Pillars of Creation leverages a large suite of JWST data, showcasing the tenuous and transient nature of these neutral gas features. Stars form within nebulae such as this, but once the gas evaporates, all they can do is burn through their fuel until they die.

Credit: NASA, ESA, CSA, STScI; Processing: Joseph DePasquale (STScI), Alyssa Pagan (STScI), Anton M. Koekemoer (STScI)

Humanity’s imagination, creativity, and intelligence remains unmatched.

This museum exhibit showcases Deep Blue: the computer that first defeated a reigning world chess champion in a chess match, defeating Garry Kasparov. Since Ruslan Ponomariov defeated Fritz in 2005, no human has defeated a top performing computer in a game of classical chess.

Credit: Pedro Villavicencio/flickr

Perhaps, someday, we’ll sufficiently appreciate our achievements.

An image of a circuit board

Although many claim that the advent of quantum computing will lead to a speed-up in computations across-the-board as compared to classical computers, this is wildly unlikely to be the case. Instead, the best computers will be hybrids: capable of leveraging the quantum portion for applications where Quantum Advantage can be achieved, but resorting to classical computing techniques for all other (i.e., most) applications.

Credit: fotogurmespb/Adobe Stock

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words.

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