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How many atoms are in the observable universe? –



All matter in the universe — no matter how big, small, young or old — is made up of atoms

Each of these building blocks consists of a positively charged nucleus, made up of protons and neutrons, and negatively charged orbiting electrons. The number of protons, neutrons and electrons an atom has determines which element it belongs to on the periodic table and influences how it reacts with other atoms around it. Everything you see around you is just a configuration of different atoms interacting with one another in unique ways.

So, if everything is made of atoms, do we know how many atoms are in the universe?

Related: Why does outer space look black?

To start out “small,” there are around 7 octillion, or 7×10^27 (7 followed by 27 zeros), atoms in an average human body, according to The Guardian. Given this vast sum of atoms in one person alone, you might think it would be impossible to determine how many atoms are in the entire universe. And you’d be right: Because we have no idea how large the entire universe really is, we can’t find out how many atoms are within it. 

However, it is possible to work out roughly how many atoms are in the observable universe — the part of the universe that we can see and study — using some cosmological assumptions and a bit of math.

The observable universe

The universe was created during the Big Bang 13.8 billion years ago. As it exploded into existence, from a single point of infinite mass and temperature, the universe began expanding outward and hasn’t stopped since. 

Because the universe is 13.8 billion years old and the observable universe stretches as far away from us as light can travel in the time since the universe was born, you might assume that the observable universe stretches only 13.8 billion light-years in every direction. But because the universe is constantly expanding, this isn’t the case. When we observe a distant galaxy or star, what we are really seeing is where it was when it first emitted the light. But by the time the light reaches us, the galaxy or star is much farther away than it was when we saw it. Using cosmic microwave background radiation, we can work out how fast the universe is expanding, and because that rate is constant — which is currently scientists’ best guess (although some scientists think it may be slowing down) — that means that the observable universe actually stretches 46 billion light-years in all directions, according to Live Science’s sister site

But knowing how big the observable universe is doesn’t tell us everything we know about how many atoms are in it. We also need to know how much matter, or stuff, is in it.

Notice how the universe has expanded since the Big Bang happened 13.8 billion years ago.  (Image credit: Shutterstock)

Cosmic assumptions

Matter is not the only thing in the universe, however. In fact, it makes up only about 5% of the universe, according to NASA. The rest consists of dark energy and dark matter, but because they are not made up of atoms, we don’t need to worry about them for this mystery. 

Related: What happens in intergalactic space?

According to Einstein’s famous E=mc^2 equation, energy and mass, or matter, are interchangeable, so it is possible for matter to be created from or transformed into energy. But on the cosmic scale of the universe, we can assume that the amount of matter created and uncreated cancel each other out. This means matter is finite, so there are the same number of atoms in the observable universe as there always have been, according to Scientific American. This is important because our picture of the observable universe is not a single snapshot in time.

According to our observations of the known universe, the physical laws that govern it are the same everywhere. Combined with the assumption that the expansion of the universe is constant, this means that, on a large scale, matter is uniformly distributed throughout the cosmos — a concept known as the cosmological principle. In other words, there are no regions of the universe that have more matter than others. This idea allows scientists to accurately estimate the number of stars and galaxies in the observable universe, which is useful because most atoms are found within stars.

Simplifying the equation

Knowing the observable universe’s size and that matter is equally and finitely distributed across it makes it a lot easier to calculate the number of atoms. However, there are a few more assumptions we have to make before we break out the calculator.

First, we must assume that all atoms are contained within stars, even though they aren’t. Unfortunately, we have a much less accurate idea of how many planets, moons and space rocks there are in the observable universe compared with stars, which means it is harder to add them into the equation. But because the vast majority of atoms in the universe are contained within stars, we can get a good approximation of the number of atoms in the universe by figuring out how many atoms there are in stars and ignoring everything else.

Second, we must assume that all atoms in the universe are hydrogen atoms, even though they aren’t. Hydrogen atoms account for around 90% of the total atoms in the universe, according to Los Alamos National Laboratory, and an even higher percentage of the atoms in stars, which we are focusing on. As you will see shortly, it also makes the calculations a lot simpler.

Doing the math

Now, it’s finally time to do the math. 

To work out the number of atoms in the observable universe, we need to know its mass, which means we have to find out how many stars there are. There are around 10^11 to 10^12 galaxies in the observable universe, and each galaxy contains between 10^11 and 10^12 stars, according to the European Space Agency. This gives us somewhere between 10^22 and 10^24 stars. For the purposes of this calculation, we can say that there are 10^23 stars in the observable universe. Of course, this is just a best guess; galaxies can range in size and number of stars, but because we can’t count them individually, this will have to do for now.

On average, a star weighs around 2.2×10^32 pounds (10^32 kilograms), according to Science ABC, which means that the mass of the universe is around 2.2×10^55 pounds (10^55 kilograms). Now that we know the mass, or amount of matter, we need to see how many atoms fit into it. On average, each gram of matter has around 10^24 protons, according to Fermilab, a national laboratory for particle physics in Illinois. That means it is the same as the number of hydrogen atoms, because each hydrogen atom has only one proton (hence why we made the earlier assumption about hydrogen atoms). 

This gives us 10^82 atoms in the observable universe. To put that into context, that is 100,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000 atoms. 

This number is only a rough guess, based on a number of approximations and assumptions. But given our current understanding of the observable universe, it is unlikely to be too far off the mark. 

Originally published on Live Science.

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NASA spots double crater on Moon caused by mystery rocket crash – ZDNet



A rocket body impacted the Moon on March 4, 2022, creating a double crater.

Image: NASA/Goddard/Arizona State University

Astronomers have finally identified the impact site of a mystery rocket that curiously created two craters on the dark side of the Moon. 

The rocket part hit the Moon on March 4, but astronomers only reported the discovery of the impact site last week. There’s now an eastern crater on the Moon about 18 meters in diameter (19.5 yards) that’s superimposed on a western crater measuring 16 meters in diameter (17.5 yards). 


According to NASA, the double crater may indicate that the rocket body had large masses at each end. So far, no other rocket crashes on the Moon have created double craters, even though Apollo SIV-B craters were larger. 

SEE: NASA’s Mars helicopter has a problem. This clever software trick could fix it

Neither NASA nor any other astronomers have been able to confirm which nation or company’s rocket it was. 

“Typically a spent rocket has mass concentrated at the motor end; the rest of the rocket stage mainly consists of an empty fuel tank,” said Mark Robinson, a professor in the School of Earth and Space Exploration at Arizona State University, in a NASA press release. 

“Since the origin of the rocket body remains uncertain, the double nature of the crater may indicate its identity.” 

Robinson is also the principal investigator for the NASA Lunar Reconnaissance Orbiter Camera and a new NASA lunar-imaging experiment called ShadowCam. 

Per the New York Times, there was speculation in January that the rocket part was the second stage of a SpaceX Falcon 9 that was launched in 2015 on behalf of the National Oceanic and Atmospheric Administration for its “DSCOVR” Deep Space Climate Observatory project. But that was later ruled out.  

Bill Gray, the developer of Project Pluto astronomical software, first spotted the rocket in January and was tracking it as it approached the Moon. 

SEE: NASA delays its Psyche asteroid mission

He’d posited in January, as reported by Ars Technica, that it was the Falcon 9 part, but a NASA engineer said the launch trajectory didn’t fit with the orbit of the rocket. 

Gray later concluded the likely candidate was a Long March 3C rocket launched from China in 2014. 

But China’s Ministry of Foreign Affairs claimed in a statement on February 21 that “the upper stage of the rocket related to the Chang’e-5 mission entered into Earth’s atmosphere and completely burned up”. 

Gray disagrees with China’s assessment and thinks it got “two different, but similarly named, lunar missions mixed up”.  

He also argues some official agency like the US Space Force, or potentially some international agency, should be tracking space junk in far-away space, not just objects like astroids in lower orbit.  

“Many more spacecraft are now going into high orbits, and some of them will be taking crews to the moon. Such junk will no longer be merely an annoyance to a small group of astronomers,” wrote Gray on his Project Pluto blog.

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G2V Optics soars on aerospace opportunities – Taproot Edmonton



G2V Optics has sent solar simulators to NASA to help test a spacecraft that aims to solve Earth’s growing space-junk problem. It’s the latest success in the Edmonton-based company’s evolution toward using its “Engineered Sunlight” technology to help aerospace organizations know what to expect from the sun once they get their devices into orbit.

“It’s a huge project, and … a fantastic feather in the cap of everybody in our team who worked on it,” G2V Optics CEO Ryan Tucker told Taproot. “And I think an awesome thing for Edmonton and our technology.”

G2V Optics has received US$822,100 in contracts from NASA since 2021. This project, the culmination of a two-year procurement process, is for the testing of OSAM-1, a spacecraft that is scheduled to be launched in 2026 to service Landsat 7, a satellite that is past its prime. If OSAM-1 can successfully dock with Landsat 7 and refuel it, then NASA will be a step closer to increasing the life expectancy of satellites, even those that were not designed to be serviced in orbit, and decrease the number of out-of-commission craft at risk of smashing into each other around our planet.

This is not the first foray into the space business for G2V Optics. In addition to a previous contract with NASA laboratories, the company has been working with the Centre nationale d’études spatiales (CNES) in France to enable the testing of technology involved in the 2024 Martian Moons eXploration (MMX) mission, in which a rover will land on Phobos and fly by Deimos.

“We don’t put anything into space. But we’re creating all the photons to make sure that everything works when they send it there,” Tucker said, noting that it’s fun to have a preview of the space research going on. “We kind of get to peek behind the curtain of these really interesting and exciting space exploration missions before they become public.”

Space is not where G2V Optics started when it was founded in 2015. After founder and CTO Michael Taschuk first developed the company’s light-emitting diode technology at the National Institute for Nanotechnology at the University of Alberta, its first applications tended to be in food production, specifically to maximize the efficacy of vertical farming.

“From a technical perspective, (we) did remarkable things,” Tucker said. “We were able to grow 30% more biomass with the same amount of energy and improve what was possible by using the complexity of our technology. But we realized that we were too early for that market … it’s such a nascent industry that’s dealing with its own challenges around scaling.”

At the same time, solar cell researchers and aerospace companies were ready for what G2V makes.

“We all of a sudden started working in this sector, with this more complex requirement, that was a perfect fit for what we had developed,” Tucker said. “That’s the traction that you’re looking for, right? Your job as a startup is to find that fit. And it wasn’t exactly where we thought it was. But we were, I like to think, smart enough to listen to it and to chase it when we found it.”

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NASA rocket launches to test new orbit for moon missions – CBC News



NASA wants to experiment with a new orbit around the moon that it hopes to use in the coming years to once again land astronauts on the lunar surface.

So it is sending up a test satellite from New Zealand. The initial stages of the launch went according to plan late Tuesday, with the rocket carrying the satellite reaching space.

If the rest of the mission is successful, the CAPSTONE CubeSat satellite — only about the size of a microwave oven — will be the first to take the new path around the moon and will send back vital information for at least six months.

Technically, the new orbit is called a near-rectilinear halo orbit. It’s a stretched-out egg shape with one end passing close to the moon and the other far from it.

Imagine stretching a rubber band back from your thumb. Your thumb would represent the moon and the rubber band the flight path.

“It will have equilibrium. Poise. Balance,” NASA wrote on its website. “This pathfinding CubeSat will practically be able to kick back and rest in a gravitational sweet spot in space — where the pull of gravity from Earth and the Moon interact to allow for a nearly-stable orbit.”

Eventually, NASA plans to put a space station called Gateway into the orbital path, from which astronauts can descend to the moon’s surface as part of its Artemis program.

Group effort

For the satellite mission, NASA teamed up with two commercial companies. California-based Rocket Lab launched the rocket carrying the satellite, which in turn is owned and operated by Colorado-based Advanced Space.

The mission came together relatively quickly and cheaply for NASA, with the total mission cost put at $32.7 million.

Getting the 25-kilogram satellite into orbit will take more than four months and be done in three stages.

First, Rocket Lab’s small Electron rocket launched from New Zealand’s Mahia Peninsula. Just nine minutes later, the second stage called Photon separated and went into orbit around Earth. Over the next five days, Photon’s engines are scheduled to fire periodically to raise its orbit further and further from Earth.

Six days after the launch, Photon’s engines will fire a final time, allowing it to escape Earth’s orbit and head for the moon.

Photon will then release the satellite, which has its own small propulsion system but which won’t use much energy as it cruises toward the moon over four months, with a few planned trajectory course corrections along the way.

“Perfect Electron launch!” Rocket Lab founder Peter Beck tweeted Tuesday. “Lunar photon is in Low Earth Orbit.”

Rocket Lab spokesperson Morgan Bailey said it was the most ambitious and complex mission it has undertaken so far and comes after more than two years of work with NASA and Advanced Space. She said it will be the first time Rocket Lab has tested its HyperCurie engine that will be used to power Photon.

“Certainly lots of hard problems to solve along the way, but we’ve ticked them off one by one, and made it to launch day,” Bailey said.

Bailey said one of the advantages of the orbit is that, theoretically, a space station should be able to maintain continuous communication with Earth because it will avoid being eclipsed by the moon.

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