What happened after the lights came on in the universe?

An experiment to explore the aftermath of cosmic dawn, when stars and galaxies first lit up the universe, has received nearly $10 million in funding from the National Science Foundation to expand its detector array in South Africa.

The experiment, an international collaboration called the Hydrogen Epoch of Reionization Array, or HERA, currently has 19 14-meter (42-foot) radio dishes aimed at the southern sky near Carnarvon, South Africa, and will soon up that to 37. The $9.5 million in new funding will allow the array to expand to 240 radio dishes by 2018.

Led by the University of California, Berkeley, HERA will explore the billion-year period after hydrogen gas collapsed into the first stars, perhaps 100 million years after the Big Bang, through the ignition of stars and galaxies throughout the universe. These first brilliant objects flooded the universe with ultraviolet light that split or ionized all the hydrogen atoms between galaxies into protons and electrons to create the universe we see today.

"The first galaxies lit up and started ionizing bubbles of gas around them, and soon these bubbles started percolating and intersecting and making bigger and bigger bubbles," said Aaron Parsons, a UC Berkeley associate professor of astronomy and principal investigator for HERA. "Eventually, they all intersected and you got this über bubble, leaving the universe as we observe it today: Between galaxies the gas is essentially all ionized."

That's the theory, anyway. HERA hopes for the first time to observe this key cosmic milestone and then map the evolution of reionization to about 1 billion years after the Big Bang.

"We have leaned a ton about the cosmology of our universe from studies of the cosmic microwave background, but those experiments are observing just the thin shell of light that was emitted from a bunch of protons and electrons that finally combined into neutral hydrogen 380,000 years after the Big Bang," he said. "We know from these experiments that the universe started out neutral, and we know that it ended ionized, and we are trying to map out how it transitioned between those two."

"Before the cosmic dawn, the universe glowed from the cosmic microwave background radiation, but there weren't stars lighting up the universe," said David DeBoer, a research astronomer in UC Berkeley's Radio Astronomy Laboratory. "At some point the neutral hydrogen seeded the stars and black holes and galaxies that relit the universe and led to the epoch of reionization."

The HERA array, which could eventually expand to 350 telescopes, consists of radio dishes staring fixedly upwards, measuring radiation originally emitted at a wavelength of 21 centimeters – the hyperfine transition in the hydrogen atom – that has been red-shifted by a factor of 10 or more since it was emitted some 13 billion years ago. The researchers hope to detect the boundaries between bubbles of ionized hydrogen – invisible to HERA – and the surrounding neutral or atomic hydrogen.

Chinese Space Station

Three Words: Chinese. Space. Station.

China just put another small space station into orbit—and by the 2020s they may replace the International Space Station. But private companies are the future of space exploration.

China has just launched its second small Tiangong space station into orbit, more or less catching up to what the United States’ and Russia’s own space programs achieved starting in the 1970s.
Riding atop a Long March rocket, the 34-foot-long, 10-ton Tiangong-2 blasted off from the Jiuquan Satellite Launch Center in northwest China on Sept. 15, aiming for an orbit 240 miles over Earth’s surface.
While Beijing’s effort to establish a long-term human presence in orbit is impressive on a political level, on a technological level it’s decades behind the curve. In the United States and elsewhere, private companies are poised to establish a long-term presence in space that doesn’t depend on big, government-run orbital structures.
“China is currently doing nothing in space that the U.S. hasn’t done already, much sooner, and often with a much higher level of technological sophistication,” Joan Johnson-Freese, a professor at the U.S. Naval War College and a space expert, told The Daily Beast.
In the race to build orbital habitations, Russia actually beat the United States by a few years when it launched the first of several Salyut stations beginning in 1971. America’s first space station was Skylab, which lasted six years starting in 1973. Today Russia and the United States work together on the International Space Station, which began operation in 1998 and has expanded to include dozens of modules capable of supporting six crew in total, year-round.
Compared to the International Space Station, the single-module Tiangong stations are tiny.
The plan is for a pair of Chinese astronauts to visit Tiangong-2 in October and stay for a month or so—an improvement over the Tiangong-1 station, which managed to support two crew for just eight days in 2012 and 12 days in 2013.
Tiangong-1, China’s first space station, launched in 2011 and decommissioned back in March amid rumors of a technical malfunction. Chances are the older station will plummet back to Earth sometime in 2017 as its orbit decays.
Like its predecessor, Tiangong-2 is supposed to last just a few years. Its replacement could be a third Tiangong station that, like Tiangong-1 and -2, will be temporary. The Chinese space agency is planning to loft a fourth and much larger station in 2020 or later. Assuming the project succeeds, the fourth craft could become the basis of a large, long-lasting space station similar in scale to the International Space Station.
But don’t hold your breath. “The Chinese have quite a bit more work to do before they are ready to start assembling their space station,” Gregory Kulacki, a space expert with the Union of Concerned Scientists, told The Daily Beast. “It is possible they could complete that work by 2020, but my guess is that they will need more time.”


In any event, it’s possible the Chinese could have a large, sustainable space station up and running by the time International Space Station finally reaches the end of the line in the mid- to late 2020s. At that point, prolonging the International Space Station’s useful life would take a sizable injection of expensive new technology requiring significant political will. With NASA’s budgets flattening and U.S.-Russian relations at a low point, the space station could begin to look like a pricey liability in Washington and Moscow.
And that’s where China holds an advantage. Sure, the Tiangong stations are small and somewhat archaic—and the larger station they’re meant to support will merely duplicate what the International Space Station achieved in 1998. What’s impressive is that Beijing has managed to plug away steadily at its space stations, year after year, calmly weathering economic crises and political turnover.
Such stability is vital for space programs costing tens or hundreds of billions of dollars and requiring years or even decades of research and development. And in space the Chinese Communist Party has proved remarkably stable. “As many members of the Chinese space community have told me, China is not in a hurry,” Kulacki explained. “They are not racing anyone, and safety is a higher priority than meeting an arbitrary deadline.”
Indeed, the enduring domestic political support for China’s space stations could prove more important than the stations themselves for China’s future as a space power. By contrast, the United States—and, to a lesser extent, other spacefaring countries—is virtually assuming that political will for its own space program will collapse, and private companies such as SpaceX, Blue Origin, and Virgin Galactic will fill the vacuum.
There’s even a company building space stations. In April, Las Vegas space startup Bigelow Aerospace announced an ambitious plan to build at least two inflatable space stations and lob them into orbit starting in 2020. The B330 stations—each featuring its own power, life-support systems, and maneuvering thrusters arranged around a central metal frame—could function as space hotels, orbital factories, and zero-gravity research labs.


CEO Robert Bigelow said he wants to attach the first B330 to the International Space Station in order to expand the station’s volume by as much as a third and, perhaps, help extend its usefulness beyond its planned mid-2020s decommissioning date. “We are hoping we can get the permissions necessary from NASA to say, ‘Yes, let’s attach it,’” Bigelow said.
But even if NASA says no, Bigelow said he will continue developing his inflatable stations. There’s plenty of incentive to do so. Asteroid- and moon-mining—and the associated orbital manufacturing—could mean hefty profits for any company willing to make a big investment in space technology andassume a significant financial risk.
“The new space players such as Bigelow, SpaceX, and Virgin Galactic are the future,” Johnson-Freese told The Daily Beast. “The new space players aren’t reliant on political will. They operate on business plans, a much sounder practice and one that will eventually ‘normalize’ space as an area of industrial and geographic development.”
While China tinkers with old school, government-funded orbital stations, the United States—via private enterprise—is laying the foundation for a whole new approach to space exploration.

China’s atomic clock

China’s atomic clock in space will stay accurate for a billion years

China’s new space laboratory has an atomic clock which, Chinese engineers say, is more accurate than the best timepiece operated by America’s National Institute of Standards and Technology.

The device, called Cacs, or Cold Atomic Clock in Space, was launched this weak along with other instruments of the Tiangong-2, China’s second orbital lab. According to the South China Morning Post, it will slow down by only one second in a billion years. In comparison, the NIST-F2 atomic clock, which serves as the United States’ primary time and frequency standard, loses a second every 300 million years.
“It is the world’s first cold atomic clock to operate in space... it will have military and civilian applications,” said Professor Xu Zhen from the Shanghai Institute of Optics and Fine Mechanics, who was involved in the Cacs project.
An atomic clock uses vibrations of atoms to measure time, which are very consistent as long as the atoms are held at constant temperature. In fact, since 1967 the definition of second has been “9,192,631,770 vibrations of a cesium-133 atom.”
In a cold atomic clock, the atoms are cooled down with a laser to decrease the effect of atom movement on the measurements. Cacs goes even further and eliminates the pull of Earth’s gravity by being based in orbit.
Chinese engineers had to miniaturize their device so that it could be sent into space. It can fit in a car trunk, while the NIST-F2, along with all its support equipment, is about the size of a room.
Cacs was launched before the European Space Agency could place their atomic clock, the Pharao, in orbit, which is scheduled to be launched next year. The US abandoned a similar project due to budgetary cuts.
Unlike Pharao, which uses the traditional design with cesium atoms, the Chinese clock uses rubidium atoms. Developers say the element offers better performance in terms of accuracy and reliability.
Cacs is not the most accurate timepiece in the world. German researchers at Physikalisch-Technische Bundesanstalt have built an experimental atomic clock, which uses ytterbium ions and is two orders of magnitude more accurate than regular cesium clocks. The device, however, is used only for demonstration purposes, while Cacs is meant for practical applications.
The Chinese plan to improve their BeiDou Navigation Satellite System with synchronization signals from the new orbital atomic clock.

Earth Vulnerable to Major Asteroid Strike

Earth Vulnerable to Major Asteroid Strike, White House Science Chief Says

Artist's concept of an asteroid striking Earth.

Credit: NASA/Don Davis

The world is still vulnerable to a potentially catastrophic asteroid strike, according to President Barack Obama's chief science adviser.

NASA has made substantial progress in finding the asteroids that pose the biggest threat to Earth, but there's still a lot of work to do, said John Holdren, director of the White House's Office of Science and Technology Policy.

"We are not fully prepared, but we are on a trajectory to get much more so," Holdren said today (Sept. 14) at NASA's Goddard Space Flight Center, during a discussion of the agency's planned Asteroid Redirect Mission (ARM). [Images: Potentially Dangerous Asteroids]

Holdren cited the February 2013 meteor explosion over the Russian city of Chelyabinsk and the 1908 Tunguska airburst as reasons to take the asteroid threat seriously.

The Chelyabinsk strike, which injured about 1,200 people, was caused by an object that is thought to be about 65 feet (20 meters) wide. The Tunguska event was much more powerful; a space rock perhaps 130 feet wide (40 m) exploded over a mostly unpopulated region of Siberia, flattening 800 square miles (2,070 square kilometers) of forest. Both strikes caught the world completely by surprise.

"We know that this does happen," Holdren said.

Strikes such as the Chelyabinsk impact are thought to happen once every hundred years, he added, while Tunguska is regarded as a once-in-1,000-years event.

But, Holdren said, "if we are going to be as capable a civilization as our technology allows, we need to be prepared for even those rare events, because they could do a lot of damage to the Earth."

"This is a hazard that, 65 million years ago, the dinosaurs succumbed to," he added. "We have to be smarter than the dinosaurs."

ARM can help educate us, Holdren said. In late 2021, NASA aims to launch a robotic probe toward a near-Earth asteroid; the current target is a 1,300-foot-wide (400 m) rock called 2008 EV5, but that’s not set in stone, agency officials said.

After it arrives at the asteroid, the spacecraft will pluck a boulder off its surface and then fly along with the space rock for a while, investigating the potential of a deflection strategy known as the "enhanced gravity tractor." (The standard gravity-tractor method calls for nudging a potentially hazardous asteroid off course over the course of years or decades, using the subtle gravitational tug of a tag-along robotic probe; this effect will be "enhanced" by the addition of the boulder's mass.)

The probe will then head back toward Earth, eventually placing the boulder in orbit around the moon. Astronauts aboard NASA's Orion space capsule will visit the purloined rock in the mid-2020s, agency officials have said.

The $1.25 billion ARM mission should help researchers learn more about asteroids and the resources they possess; demonstrate many of the technologies needed to get astronauts to Mars (which NASA aims to do before the end of the 2030s); help the agency practice human operations in deep space; and hone some of the skills that will be needed to deflect a potentially dangerous asteroid one day, Holdren said.

"The asteroid-retrieval mission makes sense in about five different ways," he said.

While smaller asteroids can do great damage on a local scale, experts think that space rocks must be at least 0.6 miles (1 km) wide or so to threaten human civilization. NASA scientists estimate that they have found at least 90 percent of these mountain-size, near-Earth asteroids, and none of them pose a threat for the foreseeable future.

Gravity tractors aren't the only possible defense against incoming asteroids. For example, dangerous space rocks could also be knocked off course by "kinetic impactors" (a series of spacecraft that slam into them). Some researchers have also proposed destroying asteroids with nuclear bombs; this is usually regarded as a last-resort strategy, to be used with space rocks that are discovered too late to deflect via gravity tractors and/or kinetic impactors.

China to launch second space laboratory

China to launch second space laboratory: report

China is pouring billions into its space programme and working to catch up with the US and Europe

China will launch its second space lab on Thursday, official media said Wednesday, as the Communist country works towards setting up its own space station, among several ambitious goals.

The Tiangong-2, or Heavenly Palace-2, will be sent into orbit from the Jiuquan Satellite Launch Centre in the Gobi desert, the official news agency Xinhua reported.
Engineers had begun injecting propellant into the Long March-2F rocket that would carry it aloft, it cited Wu Ping, deputy director of China's manned space engineering office, as saying.
Once it is in place the Shenzhou-11 mission will take two astronauts to the facility, where they will stay for 30 days, she added.
China is pouring billions into its space programme and working to catch up with the US and Europe.
It announced in April it aims to send a spacecraft "around 2020" to orbit Mars, land and deploy a rover to explore the surface.
Beijing sees the military-run programme as symbolising the country's progress and a marker of its rising global stature.
The nation's first lunar rover was launched in late 2013, and while it was beset by mechanical troubles it far outlived its expected lifespan, finally shutting down only last month.
But for the most part China has so far replicated activities that the US and Soviet Union pioneered decades ago.
It intends to build a Chinese space station, and eventually put one of its citizens on the surface of the moon.
China's first space lab, Tiangong-1, was launched in September 2011 and ended transmissions in March this year, when it had "comprehensively fulfilled its historical mission", Xinhua quoted Wu as saying.
It is expected to fall back to Earth in the second half of next year, she added

moon's birth

Moon's Birth May Have Vaporized Most of Earth, Study Shows

This artist's conception shows the giant impact that created Earth's moon. New research suggests the impact was powerful enough to vaporize a large portion of the young Earth.

Credit: Dana Berry/SwRI

The massive collision that created the moon may have vaporized most of the early Earth, according to a new analysis of samples collected during the Apollo moon missions.In the early days of planet formation, a grazing collision between the newborn Earth and a Mars-size rock named Theia (named after the mother of the moon in Greek myth) may have led to the birth of the moon, according to a prevailing hypothesis. Debris from the impact later coalesced into the moon. This "giant-impact hypothesis" seemed to explain many details about Earth and the moon, such as the large size of the moon compared with Earth and the rotation rates of the two bodies. But in the last 15 years, evidence has arisen that has challenged scientists to alter the details of this hypothesis. [How the Moon Evolved: A Timeline in Images]

Forming the moon

The moon is Earth's nearest 

neighbor, but its origins date 

back to a violent birth billions

 of years ago. See how the

 moon was made in this 

Space.com infographic.

Credit: By Karl Tate, Infographics Artist

In 2001, scientists began discovering that terrestrial and lunar rocks had a lot in common: the two bodies possess many of the same chemical isotopes. (Isotopes of an element have different numbers of neutrons from each other. These subvarieties are identified by different numbers; for example, potassium-39 or potassium-40). Isotopes can act as geologic fingerprints, because prior work has suggested that planetary bodies that formed in different parts of the solar system generally have different isotopic compositions. These discoveries threw the giant-impact hypothesis into crisis because previous computer simulations of the collision predicted that 60 to 80 percent of the material that coalesced into the moon came from Theia rather than Earth. The likelihood that Theia happened to have virtually the same isotopic composition as Earth seemed extremely unlikely.At first, scientists thought more precise isotopic analyses might help resolve this "isotopic crisis." However, more accurate measurements of oxygen isotopes reported in 2016 only helped confirm this problem, said study lead author Kun Wang, a geochemist now at Washington University in St. Louis.
"Now we need to rethink the ideas that we had about the giant impact," Wang told Space.com. New ideasNew models of the giant impact seek to explain how the moon could have formed from mostly the same material that makes up the Earth, rather than mostly from Theia.
"There are many new models — everyone is trying to come up with one — but two have been very influential," Wang said in a statement. [How the Moon Formed: 5 Wild Lunar Theories]

A diagram showing two recent models for how 

the moon formed from a collision between

 the early Earth and another massive body. 

One model (top) allows for an exchange

 of material between the Earth and the

 moon through a silicate atmosphere, 

while the other model creates a more

 thoroughly mixed sphere of a supercritical 

fluid (bottom). Each of these models

 leads to a different prediction for

 potassium isotope ratios in lunar 

and terrestrial rocks (right).

Credit: Kun Wang

The original giant-impact model suggested that a relatively low-energy collision melted part of Earth and the whole of Theia, flinging some of the molten debris outward. One relatively new model, proposed in 2007, starts with a low-energy impact just like the original model, but adds an atmosphere of silicate vapor around Earth and the disk of debris that ends up forming the moon. This model suggests that this vapor shroud helps Earth and the disk exchange material before the moon emerges from the debris.

One drawback of this low-energy impact model is that it would take a long time to exchange material through an atmosphere, Wang said. This scenario would make it difficult to achieve the mix of material seen in terrestrial and lunar rocks, he said.

Another model, proposed in 2015, suggests that a high-energy impact created the moon, one so violent that it vaporized Theia as well as most of Earth, including the young planet's mantle region (the layer just above the core). This dense vapor then formed an atmosphere that filled a space more than 500 times bigger than today's Earth. Much of this material would fall back onto the Earth as it cooled, but in addition, some of the debris formed the moon.

In this high-energy model, the atmosphere would behave like a "supercritical fluid," without a distinct separation between liquids and gases. Material could mix thoroughly in such an atmosphere, which could help explain the identical isotopic compositions of Earth and the moon, Wang said.

To see which model might best explain how the moon formed, Wang and his colleague Stein Jacobsen at Harvard University focused on potassium isotope data from terrestrial rocks and lunar samples gathered during the Apollo missions. Potassium is volatile, or easy to evaporate, and previous research suggested that analyzing potassium isotopes could shed light on the conditions during the event that formed the moon.

The scientists analyzed seven moon rocks collected during the Apollo 11, 12, 14 and 16 missions. They compared their potassium isotope ratios with those of eight rocks representative of Earth's mantle.

The researchers developed a method to analyze potassium isotopes with a level of precision 10 times better than the best previous technique. Potassium has three stable isotopes, but only two of them, potassium-39 and potassium-41, are abundant enough to be measured with sufficient precision for this research.

The scientists discovered that lunar rocks were richer by about 0.4 parts per thousand compared with Earth rocks when it came to potassium-41, the heavier stable isotope of potassium.

These findings support the high-energy impact model, which predicted that lunar rocks would possess more of the heavier isotope than terrestrial rocks. In contrast, the low-energy impact model suggested that lunar rocks would contain less of the heavier isotope.

The best explanation for how the heavier isotope came to dominate was that the moon condensed in a cloud with a pressure of more than 10 bar, or about 10 times the atmospheric pressure on Earth at sea level.

"I'm kind of surprised that the new model fits the data the best," Wang said. Still, "we had no expectation which model we were going to support," he said.

Future research should conduct follow-up studies to test these new findings. "We're definitely hoping more people will follow up and try to confirm our results," Wang said.

Wang and Jacobsen detailed their findings online Sept. 12 in the journal Nature.

Exoplanets

How Space Scientists Turn Exoplanets Into Places We Can ‘See’

Artist’s impression showing the plant Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. 

DO A GOOGLE image search for “exoplanet.” You’ll find awesome stuff: golden worlds like almond cookies, outsized maroon crags, marbly surfaces, hyperclose suns, clouds obscuring unfamiliar continents.

On August 24, astronomers got a new planet to make pictures of: one orbiting the nearest star to our solar system, Proxima Centauri. The planet, Proxima b, orbits closely enough that its water might not be frozen (if it has water) and far enough away that it may not have baked off (maybe). The European Space Agency shared a surface view of a suns-set on Proxima b, with three stars near the horizon illuminating jutting rocks, rounded rocks, arcing rocks, and possibly some fog in the foreground.

Of course, scientists don’t actually know what any exoplanets look like. But imagining how they might be—in a standing-right-there sense—is central to scientists’ perceptions of and interest in them, according to Lisa Messeri, a space anthropologist at the University of Virginia. And people feltso passionate about Proxima b (which is not Earth-like) because its proximity makes it more real. It is a place people could imagine being.

Messeri studies how scientists effect the transformation from random planet to real place. In her new book, Placing Outer Space, she maps that mental shift among scientists at the Mars Desert Research Station, at a Silicon Valley NASA center, at a mountaintop observatory in Chile, and in an MIT exoplanet group.

Messeri immersed herself in that latter cohort during her third year as a doctoral student at MIT , when she met professor Sara Seager. Seager is a celebrity scientist now, profiled by the likes of Cosmo. But back when she met Messeri, around 2009, she was mostly a rock star among scientists. Seager took Messeri into her research group for nine months, letting her orbit, observe, ask questions.

“The first thing you notice when you’re really spending time with exoplanet astronomers is just how little data there actually was to model and play with,” says Messeri. That was especially true when her work began, before Kepler’s heyday. For Seager and her students, a “planet” emerged from just a few data points showing how a star’s brightness changed over time. A dip in the middle showed the star’s light dimming, suggesting an alien globe had passed in front of the star. Over time, Seager and her students learned to see a whole world in that upside-down-omega shape. “That line,” says Messeri, “becomes incredibly evocative.”

They could learn a planet’s radius, the length of its year, its distance from its star. They could infer fuzzy things about its composition, its temperature. They could start to picture the planet, almost as if joining the flat parts of that upside-down-omega at the top to make a circle.
Home Sweet Home

It’s easy enough to imagine an exoplanet—and imagine yourself on it, arm draped against your forehead to shield your eyes from the three suns—that’s “like Earth.” When a scientist finds an Earth-sized or Earth-mass planet, their wild imagination has familiar places to run: variations on the theme of “Earth.” It’s got some water, maybe some Truffula trees, some canyons grander than our planet’s. It’s great!

But what about all those planets very much not like Earth (a category also known as “most”)? “With alien and exotic exoplanets, it struck me as a real puzzle,” says Messeri. “Scientists still manage to take worlds that are zipping around their sun every four days, gas giants larger than Jupiter, planets with molten surfaces with only one side facing their sun and understand that this is what they’re like. And how did it get transformed into a world?”

Part of the key is in the language Messeri herself used in that last sentence: A four-day year is tiny only in reference to ours. She compares huge gas planets to smaller Jupiter. She says planets face and zip around their suns.

It’s all about bringing it back home. We have hot Jupiters, mini-Neptunes, super-Earths. All of these planet categories, by their very definitions, are not like Jupiter, not like Neptune, not like Earth. But to construct a place, scientists have to draw on the worlds within their own experience: and My Very Educated Mother Just Served Us Nine is all we’ve got.

In the book, Messeri cites a paper Seager’s group was writing about the planet GJ 1214b. They explicitly said the planet had no analogs within our solar system. And yet, “each time they tried to get away from solar system analogies, it became apparent that analogy was the only way out of the semantic gap.”

Astronomers have created these comparison terms to conceptualize planets, yes. But the terms also shape the way the astronomical community perceives their discoveries. Researchers must get the people who read their papers—including the reviewers who decide whether a paper gets published at all—to see the same interesting and extant world they see in the data. A little linguistic push in the right direction never hurts.

A NASA Goddard scientist, for instance, told Messeri about a colleague who had theorized a new kind of world: the “volatile-rich planet,” Earth-mass but smothered in liquid. A competitor had come up with the same idea around the same time. But he called them “ocean-planets” in his paper. That second guy—people paid attention to him. People can picture an ocean. They can’t call up a volatile. “You have to make the argument not just that this is a planet but that this is a place worth studying,” says Messeri.

In some ways, then, exoplanet science is world-building of the persuasive variety.
Earth’s Origins

And I’ve been doing it myself this whole piece. Even the word “worlds” is meant to make you think of these spheroids of solid, liquid, and gas in a certain way. I could relentlessly call them “exoplanets,” but that puts a telescope lens between you and them. I could stick to “planets,” which would connect them to the shapes in our solar system.

But “world”: That’s a thing you are (or some other species is) meant to exist on, a thing of the same sort that we exist on. Or, as Messeri wrote more eloquently, it “connotes an inextricable linking between Earth and humanity.”

Of course, we didn’t always think of our own planet as being like all the other ones. It was only after Voyager sent back the image of Earth as a Pale Blue Dot, after astronauts started going up regularly, and especially after they got social media accounts that humans conceived of Earth as a globe in space (and still, actually feeling that this is actually a planet shaped like a planet requires concentration).

Earth has always been a place to us. It’s always been our world. But it’s only recently become our planet.

Today, says Messeri, a new shift is taking place. The image of the Pale Blue Dot at first made humans feel speckish, alone, insignificant. But exoplanet astronomers spend their lives searching for other Pale Blue Dots. And their work has shown us that the universe is teeming with dots, be they quite as blue as ours or not.

And as astronomers gather the data that turns those dots into imaginable planets, the universe begins to feel more friendly and knowable, full of places we can picture.