It’s well known that cats will always land on their feet when dropped. According to this clip, those cat-like reflexes are completely lost in a weightless environment.

Along with cats, the Airmen fly pigeons in a weightless state, and some of them wound up flying upside down.

The 1947 video was part of the US Air Force’s aerospace-medical-research lab’s bioastronautics research in Dayton, Ohio.

Watch the full 13-minute video here, which includes pretty nifty slow-motion ejection-seat footage (not using cats).

SEE ALSO: The 25 most ruthless leaders of all time

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NOW WATCH: Here's Why Cats Love Boxes So Much

The crew of NASA's Apollo 10 mission in May 1969 set the groundwork for showing that Apollo 11's moon landing would be possible. They flew around the moon and practiced separating and descending the lunar module to better understand potential issues.

But — in information that wasn't made public for decades — they heard some mysterious sounds in the process, an eerie whistling that they couldn't understand and weren't sure how to report.

As lunar-module pilot Eugene Cernan asks John Young, the command-module pilot: "That music even sounds outer-spacey, doesn't it? You hear that? That whistling sound?"

That text from the transcript of their discussion was released in 2008.

Now, NASA has declassified the actual audio from the mission, which made its way into an episode of the Science Channel show "NASA's Unexplained Files." It's tough to distinguish the show's sound effects from recorded audio, but if you skip to 2:16 here you can catch some of the whistling:

Here's part two of the promo for the show:

So the question is, why — when cut off from communication with Earth — would the crew in different modules capture a mysterious audio transmission?

In the transcript, you can see that the astronauts weren't sure whether they should say anything. If NASA thought that they were unstable, then there was a real risk they'd be grounded after the mission, and they had no explanation for what they heard.

Decades later, the Cassini spacecraft captured similar mysterious transmissions from Saturn — but there we have a better explanation. When charged particles move through the magnetic environment around Saturn, they're distorted in ways that cause those odd sounds.

But as planetary scientist Kevin Grazier explains on the show promo, that explanation doesn't work for the moon, which doesn't have an atmosphere or magnetic field.

So what was it?

NASA's explanation is straightforward. The radios on the command and lunar modules were interfering with each other, causing a strange sound to appear, like when you hold a cellphone near a speaker.

On the show promo, however, astronaut Al Worden isn't so sure, and arguing that there must have been something causing the noise, saying that "logic tells me that if there was something recorded on there, then there's something there."

But as CNN notes, Apollo 11 pilot Michael Collins reported hearing similar interference noises on that mission when the lunar module detached from the command module, something he'd been warned would happen by NASA radio technicians.

And when Apollo 11's lunar module landed, the mysterious noises stopped.

The full transcript of the mission is below:

AS10_LMApollo 10 Onboard Voice Transcription-Lunar Module

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NOW WATCH: 40 years ago, NASA sent a message to aliens — here's what it says

On Friday, the spaceflight company Virgin Galactic unveiled a new spaceplane.

VSS Unity is the flashy new sibling of the VSS Enterprise, which was destroyed in a fatal accident in 2014.

The company hopes to one day carry tourists into suborbital space.

Unity is not much different from its predecessor, but one of the ship's key improvements is designed to prevent another disaster like the November 2014 accident that killed pilot Michael Alsbury. At the time, the National Transportation Safety Board concluded that Alsbury deployed a feathering reentry system too early and that Virgin Galactic hadn't planned ahead for such human errors.

The new spaceplane has safeguards in place to make sure that doesn't happen again, and the company is emphasizing a renewed commitment to careful testing.

The spaceplane has safeguards in place to make sure that doesn't happen again, and the company is emphasizing a renewed commitment to careful testing.

The new spaceplane suggests that Virgin Galactic is not out of the private spaceflight game just yet. And it still has at least one willing customer:

READ MORE: NASA's Curiosity Mars rover is snapping pictures of something unlike anything it has encountered before

SEE ALSO: This $14-billion machine is set to usher in a new era of nuclear fusion power

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NOW WATCH: Watch Jeff Bezos' spaceflight company make history with a monumental rocket landing

The world's leading futurist Ray Kurzweil isn't shocked by much. Except for this one thing.

Kurzweil — one of the world's leading minds on artificial intelligence, technology and futurism — has a strategy on how to prolong his own life until science figures out how to make us immortal.

The futurist is also the author of five national best-selling books, including "The Singularity is Near" and "How to Create a Mind." 

Produced by Will Wei. Edited by Christine Nguyen.

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In honor of tonight's "snow moon"— the second full moon of the year— the United States Postal Service (USPS) has just released the newest member of its international forever stamps global fleet: A real image of our glowing satellite, crater-pocked detail and all.

The stamp, which the USPS released Monday, features a photograph taken by Beth Swanson of Fort Lauderdale, Fla. Each one will cost $1.20 and get a one-ounce letter to any country in the world, just as long as First-Class Mail International service is available there.

This is a fitting image, considering the moon is visible from, you know, all across the globe.

And if you're wondering why it's called a "snow moon," it doesn't have anything to do with the temperature up there (although the moon does get super cold). It's actually related to the temperature here on Earth.

Each full moon name dates back to the early Native Americans, when they named full moons to keep track of time. They named February's full moon "snow moon" because, well, the month tends to get super snowy.

A full moon happens roughly once a month, when the moon, Earth, and the sun are fully aligned — with Earth in between. This fully illuminates the moon's surface, allowing its entire face to be visible from our planet.

More space stamps on the way

If you're worried that this will be the only new USPS postage to nerd out over science, don't.

In December 2015, they announced that they will be gearing up to honor NASA's historic flyby of Pluto with a new set of postage stamps, among a flotilla of other space-themed postage.

The stamps revisit a series release in the early 1990s. Back then, the USPS issued a set of stamps commemorating the planets in our solar system and the year we visited them. Pluto was the only stamp labeled "not yet explored."

That changed when NASA's New Horizons spacecraft flew past Pluto in July, 2015. Even though Pluto isn't classified as a planet anymore, the USPS has designed a stamp declaring it "Explored!"

"Since the early 1990s the old, ‘Pluto Not Explored’ stamp served as a rallying cry for many who wanted to mount this historic mission of space exploration," New Horizons lead scientists Alan Stern said in a press release. "Now that NASA’s New Horizons has accomplished that goal, it’s a wonderful feeling to see these new stamps join others commemorating first explorations of the planets."

The stamps will be dedicated between May and June at the World Stamp Show in New York, after which they'll be ready for purchase, according to the USPS.

The USPS will also dedicate a series with updated images of all the planets in our solar system. The full planet discs are shown in enhanced color:

And in one more win for nerds, USPS will also honor the 50th anniversary of the premiere of the TV show "Star Trek" with a set of stamps.

The stamps seem especially fitting since Leonard Nimoy, the actor who played the iconic role of Spock in the series, died in 2015.

You don't even have to be a "Trekkie" to appreciate them (though it helps if you are):

There's no word yet on exactly when the "Star Trek" stamps will go on sale, but the design suggests it will be sometime next year. Luckily, you can buy the new moon stamps starting today.

Kelly Dickerson contributed to this post.

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NOW WATCH: 40 years ago, NASA sent a message to aliens — here's what it says

Founder and CEO Richard Branson unveiled the second generation Virgin Galactic space plane. It will fly lucky passengers up to space for 4 minutes of zero-gravity fun. Stephen Hawking had the honor of naming it "Virgin Spaceship Unity."

Produced by Emmanuel Ocbazghi. Original reporting by Jessica Orwig.

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A prime SpaceX competitor— United Launch Alliance (ULA) — might be banned from flying one of its most important rockets, which could spell ruin for the company.

Right now, the US Government is determining whether importing Russian-made RD-180 rocket engines — which power ULA's Atlas V rockets — violates sanctions against Russia.

The US first imposed these sanctions on dozens of Russian officials after Russia seized Crimea in 2014, SpaceNews reported.

If the government finds that violation is in play, space company ULA will be unable to purchase new engines with which to launch its Atlas V rockets.

The Atlas V is one of four launch vehicles the ULA uses to carry out missions for government and commercial companies. And it's one of their most popular — ULA's last 11 missions were all conducted on Atlas V rockets.

The only problem is that the main rocket stage runs on Russian RD-180 engines, which are made by the Russian company called NPO Energomash.

And Energomash is run by numerous sanctioned Russia officials, including Deputy Prime Minister Dmitry Rogozin.

"These folks are on the sanctions list, and if the Department of the Treasury comes back and says there's a problem with that relationship, then we have to work with the Congress and others to determine a way ahead," Samuel Greaves, who heads the US Air Force's Space and Missile Systems Center, told Reuters.

The US Air Force stands to lose a lot if RD-180 engine imports are banned because ULA is currently only one of two space companies the Air Force has certified to conduct important national security launches.

The other company is SpaceX.

If ULA loses the launch capability of its Atlas V rockets, it will be more difficult for the company to compete against SpaceX for national security launch contracts — a main source of business for the company.

The evaluations were performed last week in time for a deadline set for this week by Senate Armed Services Committee Chairman John McCain. Therefore, we could know soon whether the Atlas V is grounded, or not.

READ MORE: The US Air Force is threatening to cancel its annual $800 million contract with one of SpaceX's biggest competitors and give Elon Musk an edge on a lucrative space market

SEE ALSO: 9 ways Elon Musk has already upended the spaceflight industry

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NOW WATCH: Here's Elon Musk back in 2011, explaining how ridiculously hard it would be for SpaceX to land its first reusable rocket

Business Insider Science is looking for a paid editorial intern!

Interns at Business Insider aren't sent on coffee runs or forced to spend their days filing or making copies.

Instead, they are an integral part of our team. Many of our current writers and editors started as interns. 

As a BI intern, you'll spend your time doing meaningful, important work: researching, pitching, writing, and even breaking science news. We want people who can find their own stories, pitch them, and write quickly, cleanly, and intelligently.

Our style is smart, conversational, exciting, and geared toward non-scientists. Careful attention to detail and an ability to be efficient in a quick-turnaround environment are both skills that are absolutely required for this job. We also prize agility in and enthusiasm for tackling wildly different topics — from the latest fitness trends to the growing problem of climate change to new research in space and psychology.

Our aim is to help readers engage with the world around them in as many smart, creative ways as possible. Science is everywhere.

This position is at our Flatiron headquarters in New York City. Internships run for six months and interns are encouraged to work up to 40 hours a week.

Consider applying if:

• You have awesome writing and copy editing skills.
• You can translate complicated studies, decrypt complex developments, and make science and health exciting for a general audience.
• You're constantly coming up with new story ideas.
• You're ready to take one subject or piece of news, research, and tackle it from multiple angles.
• You always have something to add to the conversation when it comes to trending news.
• You thrive in a fast-paced, collaborative setting.

Apply here with a resume, clips, and a cover letter telling us what makes you passionate about science reporting.

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NOW WATCH: People doing backflips on a two-inch wide strap is a real sport called slacklining

On Monday, SpaceX completed an important pre-launch test with one of its Falcon 9 rockets, setting the stage for an exciting launch out of Florida's Cape Canaveral Air Force Station this Wednesday.

The launch window — a carefully calibrated time when the rocket can safely launch into space — will open at 6:46 p.m. and last through 8:23 p.m. ET Wednesday evening, NASA Spaceflight reported.

SpaceX's main mission will be to launch the 11,750-pound SES-9 communications satellite into orbit over Asia, but the more dramatic, secondary goal will be what happens about 10 minutes after lift-off.

That's when the main, first stage of the Falcon 9 will fly itself back to Earth and attempt to land on a floating ocean platform called "Of Course I Still Love You." (In case you were wondering, the text is in honor of a starship in sci-fi author Iain M. Banks' "The Player of Games.")

SpaceX will be broadcasting the event live via LiveStream, provided here. Read on to learn why landing on an ocean platform is so important.

Not all missions are created equal

Wednesday's rocket landing attempt will be SpaceX's fourth try, but the company stated that it doesn't expect a high probability of success. Check out some of its earlier attempts below:

However, if the landing sticks, it will be the first time the company will have successfully landed one of its first stage Falcon 9 rockets on a floating platform.

While SpaceX has already proven it can land its rockets — a feat the company achieved for the first time at its Landing Zone 1 site at Cape Canaveral last December — landing on a floating platform in the ocean is technically more challenging than touching down on land, like December's achievement.

That's because not every mission to space is the same:

Some missions transport cargo into higher orbits above Earth's surface than others. The higher the orbit, the faster the rocket has to travel, and the more fuel it costs the rocket after take-off.

Appropriately, the missions with the highest orbits are called high velocity missions.

Because they use more fuel after take-off, that also means means less fuel for a reusable rocket's trip back to Earth. Ocean platforms offer a closer landing site for these high velocity missions that cost more fuel.

If SpaceX can land its first stage Falcon 9 on ocean platforms, it will prove that the company can readily retrieve rockets from the most difficult, fuel-exhausting missions — the high velocity missions. And if it can retrieve rockets from the most difficult missions, then it can retrieve rockets from any future space mission.

Ultimately, the idea behind these rocket landings — whether on land or drone ship — is to eventually make rockets reusable, like airplanes. This could drastically reduce the cost of spaceflight by up to a factor of 100 and get SpaceX, along with the rest of humanity, on track for a new era — one that's potentially moving toward becoming a multiplanetary species.

DON'T MISS: The US government is evaluating sanctions against Russia that could destroy SpaceX's biggest competitor

LEARN MORE: Elon Musk's rocket landing could make space travel costs cheaper than a penthouse in NYC

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NOW WATCH: Watch never-before-seen footage of SpaceX's monumental rocket landing

Despite how far we've come in space exploration, one thing still holding us back from interstellar travel is our slow spacecraft.

While we're able to propel particles to close to the speed of light in the lab, we're struggling to even accelerate spacecraft to beyond 3 percent of that. With our current technology, it's estimated it'll take humans around five months to reach Mars.

But NASA scientist Philip Lubin is working on a system where lasers propel spacecraft with giant sails to the Red Planet in as little as three days.

Much like Bill Nye's much-hyped solar sail, this 'photonic propulsion' system relies on the momentum of photons - particles of light - to move forward. But instead of photons from the Sun's rays, Lubin's design would be given a push by giant Earth-based lasers.

It sounds pretty far-fetched, but in a video for NASA 360, Lubin explains that the technology is very much readily available, and that the system could easily be scaled up.

"There are recent advances that take this from science fiction to science reality," Lubin explains."There is no known reason why we can not do this."

But let's step back for a second and investigate how the system works. Right now, when we launch spacecraft, the thrust comes from burning a chemical, such as rocket fuel. Not only does this fuel source weigh down spacecraft, it's also an incredibly inefficient system when compared to electromagnetic acceleration, which is the use of light or other electromagnetic radiation to accelerate objects.

"Electromagnetic acceleration is only limited by the speed of light while chemical systems are limited to the energy of chemical processes,"writes Lubin in a paper on the technology.

But while electromagnetic acceleration in the lab is relatively straightforward, it requires a lot of complicated and expensive equipment - such as the ring of superconducting magnets that make up the Large Hadron Collider - and hasn't been easy to scale up to the size required for space travel.

One candidate propulsion system, known as the 'impossible' EM Drive, has received a whole lot of attention for allegedly achieving electromagnetic acceleration, but NASA scientists still haven't been able to figure out how it works, or prove that it wasn't an experimental anomaly. 

Photonic propulsion, on the other hand, works in theory, regardless of the scale, making it a more viable candidate.

So how do photons work to propel something as big as a spacecraft? Despite not having any mass, particles of light have both energy and momentum, and when they reflect off an object, that momentum is transferred into a little push. With a large, reflective sail, it's possible to generate enough momentum to gradually accelerate a spacecraft.

While Lubin and his team haven't yet tried out their system, their calculations show that photonic propulsion could get a 100-kg robotic craft to Mars in just three days. 

A larger craft, like the kind humans might travel in, would take around a month to get there - one-fifth of the time it would take the Space Launch System (SLS), the world's most powerful rocket currently being developed to take us to Mars.

Lubin also explains that in the 10 minutes it will take to get the SLS into orbit, photonic propulsion could propel a spacecraft to an unheard-of 30 percent the speed of light - and it would also use a similar amount of chemical energy (50 to 100 gigawatts) to do so.

But the real benefit of photonic propulsion comes over longer distances, where the spacecraft has more time to speed up, and could eventually take us outside our Solar System and to neighbouring stars.

To be clear, the system isn't designed to send humans across interstellar distances - first of all, robots are far better equipped for that mission, and secondly, we'd be far too heavy. Instead, Lubin proposes wafer-thin spacecraft that can get close to the speed of light.

But sending our own artificial intelligence to these distant solar systems - especially ones that potentially harbour habitable planets - would still be huge.

"The human factor of exploring the nearest stars and exoplanets would be a profound voyage for humanity, one whose non-scientific implications would be enormous,"writes Lubin. "It is time to begin this inevitable journey beyond our home."

Lubin and his team last year received a proof-of-concept grant from NASA to show that photonic propulsion could be used for space travel, so we should start seeing some real-life results soon. Let's hope that the reality lives up to the hype, because we're pretty excited.

Find out more in the NASA 360 video:

SEE ALSO: 8 charts reveal mind-boggling numbers about the monster rocket NASA is building to shuttle astronauts to Mars

CHECK OUT: 3 brilliant scientists are favored to win the most prestigious physics prize of all time — but there's a big problem

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NOW WATCH: This is NASA's most powerful rocket in history—and it's going to Mars

Back in 2012, a NASA engineer with a red, white and blue mohawk won over the internet. He became a meme, received marriage proposals from strangers on Twitter, and even got a shout-out from President Barack Obama. At the time, he was working on the Mars Curiosity project, but what has he been up to since then? We chatted with Bobak Ferdowsi to find out what it's like to be a viral star and what part of space he's focused on now.

Produced by Chris Snyder

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Veteran NASA astronaut Ron Garan just signed on to be the chief pilot for an Arizona-based space company named World View. Which means he may be flying the first paying customers up to near space in a balloon.

World View is currently launching research and weather payloads to the stratosphere, but it is also working on sending up a space tourist.

"Ever since my first journey to space, I've felt a call to action to help spread a unique perspective of our home, this place we call Earth," Garan said in a statement.

While with NASA, Garan spent more than 178 days in orbit and flew on the Space Shuttle and Russian Soyuz spacecraft.

Tech Insider's Julia Calderone previously wrote about World View, which is working on plans to bring six passengers and two crew about 20 miles up in a fully-pressurized capsule attached to a custom balloon. Paying "voyagers," as the company calls them, can book their seat for $75,000.

Twenty miles is not quite the edge of space (generally thought to be 62 miles up), but it's still about three times higher than cruising altitude — enough to see the darkness of space and Earth's curvature.

Right now, the company says it's focused on things like forest fire detection, and gathering data to model weather and climate, since its balloons can be used like a satellite orbiting the planet — or maintain a hover over a single location for many months.

But with the private space race taking off, we may be close to seeing a non-astronaut headed into space again.

World View has said it wanted to get humans up by the end of 2016. So far, only the Virginia-based Space Adventures has launched non-astronauts into space, using Russian equipment to take them to the International Space Station.

"I am thrilled to join a team that embraces the same entrepreneurial spirit that launched the aviation industry and understands that true innovation is not just doing something that already exists better, but doing something completely new that revolutionizes or creates industries," Garan said.

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NOW WATCH: 40 years ago, NASA sent a message to aliens — here's what it says

So much of humanity’s astronomical research is based around the notion of finding something like us out there – whether that’s looking for environments that could sustain life, ranking planets in terms of their potential habitability, or comparing distant worlds to our own.

But what if – statistically speaking – the odds are stacked against us finding another planet even remotely like Earth?

That’s the thinking behind a new study by an international team of researchers, which has taken what we know about the exoplanets that lie outside our Solar System and fed the data into a computer model.

Their resulting calculations, designed to simulate how galaxies and planets have formed over some 13.8 billion years, produces a "cosmic inventory" of terrestrial planets – and one in which Earth very much looks to be unique.

"It’s kind of mind-boggling that we’re actually at a point where we can begin to do this," one of the researchers, Andrew Benson from the Carnegie Observatories in California, told Shannon Hall at Scientific American.

That said, the researchers acknowledge that their predictions on the spatial and temporal distribution of terrestrial planets in both the local and distant Universe is subject to a range of errors. Especially given how little we know about exoplanets – having only discovered about 2,000 of an estimated 700 quintillion or so.

"It’s certainly the case that there are a lot of uncertainties in a calculation like this,"said Benson. "Our knowledge of all of these pieces is imperfect."

But why is Earth so special? The researchers don’t know, but according to their calculations, our home is something of an anomaly, not resembling the vast majority of other planets in the Milky Way and outside it, which they say are older, larger, and unlikely to sustain life.

Given the incredibly small data set used – even 2,000 exoplanets can be considered a tiny sample to base projections from, given the vast number of potential worlds out there in the Universe – there’s no way we can know for sure, but the researchers describe Earth’s formation and position as an improbable event of chance.

"[W]e would have to accept that we ended up where we are because of an unlikely lottery draw,"the authors write in their paper, which is to be published in The Astronomical Journal. "But maybe there is more to the lottery than we have hitherto realized?"

With these kinds of massive and highly hypothetical calculations, what might refine the predictions could be further discoveries about the composition and position of more exoplanets. Until that time, as the researchers admit, their findings may need to be taken with a grain of salt.

"Whenever you find something that sticks out," one of the team, Erik Zackrisson from Uppsala University, told Scientific American, "that means that either we are the result of a very improbable lottery draw or we don’t understand how the lottery works."

SEE ALSO: These are the 4 likeliest places we'll find alien life

CHECK OUT: NASA's Curiosity Mars rover is snapping pictures of something unlike anything it has encountered before

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NOW WATCH: 40 years ago, NASA sent a message to aliens — here's what it says

This is a CubeSat. 

It's a satellite that weighs only about 3 pounds, and it's revolutionizing the way we can collect data about the Earth. 

Partly because they're so small, CubeSats only cost about $100,000 — cheap in comparison to the minimum $50 million it usually costs to launch a satellite into space.

Source: Quora

NASA's CubeSats Initiative has encouraged students, from elementary school to college, to launch their own satellites. The agency's Space Grant Program has paid for most of the ones students have made.

Source: NASA

In many cases, students have designed and built the CubeSats themselves.

On March 1, American astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko will return to Earth after spending a year aboard the International Space Station, in orbit 240 miles above Earth.

Mr. Kelly is the first American to stay in space for so long.

Kelly and Mr. Kornienko are the first humans to do so since 1999, when Russian cosmonaut Sergei Avdeyev last spent a year in microgravity aboard the Russian space station Mir, according to NASA.

The all-time record belongs to cosmonaut Valeri Polyakov, who spent 437 days on Mir from 1994-1995.

Though Kelly has been firing off tweets about the things he’ll miss most about space (sensational views of Earth, for one), he will probably be happy to plant his feet firmly on Earth and experience the grounding effects of gravity for a change.

But some aspects of his return may not be easy, his predeccsors have pointed out. 

"You've got this little bit of paranoia that you won't to be able to stand up when you walk home," Doug Wheelock, a NASA astronaut who spent 178 days in space over the course of two missions, told ABC News in June 2015.

Will be missing these sands too, but looking forward to sandy beaches up close. #EarthArt#Africa#YearInSpacepic.twitter.com/u7Ro6MdP1B

— Scott Kelly (@StationCDRKelly) February 22, 2016

"You feel the physiological changes when you get to space, and you are beginning to feel that your body and brain think you don't need your legs anymore," he said.

When Mr. Avdeyev returned to Earth from Mir in 1999, he was brought out from the spacecraft on a stretcher, The Guardian reported, as he was too weak to walk or even to sit up in a chair. It took a year for his body to readjust to full Earth gravity.

NASA expects Kelly to have a recovery period, but his recovery is precisely what scientists want to study.

After spending so much time in so little gravity, and in high radiation, researchers suspect that Kelly’s bones could be weaker, and his motor skills and vision impaired. But Kelly, like all ISS astronauts, exercises daily and has strategies for dealing with the effects of microgravity. 

“We would be happy to see no difference in a six-month mission versus a year-long mission,” said John Charles, chief scientist of the NASA Human Research Program. “But we do anticipate changes."

Understanding how the body changes after one-year mission to space is instrumental to future human space missions, particularly long ones to Mars.

By comparing Kelly’s condition post-space with that of his Earth-based, identical twin brother – retired astronaut Mark Kelly – scientists will for the first time be able to more clearly see the effects that space has on physical and psychological well-being.

“The mission will continue even after Scott returns,” said Dr. Charles. “The post-flight data are as important as the inflight data to help us learn how to send humans safely to Mars and return them safely to Earth,” he said.

But there is more to Kelly’s homecoming than physical adjustment and scientific experiments.

He will have also missed the simple pleasures of life that the ISS doesn’t offer. Kelly might crave his favorite food, or at least something that doesn’t come out of a plastic baggie. And fresh air is another luxury that doesn't exist aboard the ISS.

"Your sense of smell and taste are dulled in space," Mr. Wheelock told ABC.  “I craved the aroma of leaves and grass and flowers and trees … When you get back to Earth they are literally intoxicating," he said.

Despite some of the drawbacks of space travel, there will be at least one benefit to Kelly: he will return a fraction of a second younger than his identical twin, thanks to the effects of time dilation, a principle of Einstein’s theory of special relativity which stipulates that under conditions of great speed time moves more slowly.

According to Universe Today, after six months on the ISS, an astronaut has aged less than people on Earth by about 0.007 seconds.

SEE ALSO: 14 horrible things that could happen if we colonize Mars

CHECK OUT: NASA scientists take to Reddit to issue a dire warning

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NOW WATCH: Sea levels are rising at the fastest rate in 2,800 years — here’s what Earth will look like if all the ice melts

SpaceX is going to try and make history again.

On Thursday, February 25, the company will launch its 229-foot-tall Falcon 9 rocket from Cape Canaveral, Fla.

Shortly after launch (and setting loose a new satellite into orbit), the first and biggest part of the rocket will fall back to Earth.

But instead of becoming junk at the bottom of the ocean, the rocket stage will try to land itself on an autonomous drone ship in the Atlantic Ocean.

SpaceX has said it doesn't think this will work, but success has the potential to change spaceflight as we know it.

Here's how it might play out, and what it might mean for the future of the human race.

Kelly Dickerson contributed to this report.

Right now we rely on rockets to launch things like satellites and supplies for the International Space Station into space.

But just one rocket costs over $60 million, and you can only use it once. Amazon founder and space entrepreneur Jeff Bezos has compared it to using a 747 to fly across the country once and then throwing the plane away.

Source

That's why Elon Musk's SpaceX and Bezos' rocket company Blue Origin are trying to develop reusable rockets.

Paris  - US astronomers announced last month they may have found a ninth planet beyond Neptune, but conceded they had no idea where on an estimated 10,000-20,000-year orbit it might be.

On Tuesday, a French science quartet said they have narrowed the search area.

By studying data from NASA's Cassini spacecraft orbiting Saturn, the seventh planet from the Sun, they could exclude two zones, the team wrote in the journal Astronomy and Astrophysics.

Their work confirmed that a ninth planet might exist in the far reaches of our Solar System, co-author Jacques Laskar of the Paris Observatory told AFP, "but not just anywhere".

Based on mathematical modeling, the French scientists calculated what influence a ninth planet — traveling along the orbit postulated by the Americans — would have on the movement of other planets as it passed nearby.

They then looked at how the known planets actually behaved.

The postulated planet is thought to circle the Sun in a lopsided, highly elongated, oval loop.

At its most distant from the Sun, the planet would be too far too away for any effect on other planets to ever be detectable, thus limiting astronomers to a searchable zone representing only about half of the total orbit.

Now Laskar and his team have reduced the search area by 50 percent by eliminating two zones in which they say the modeling does not match reality.

"We have cut the work in half," he told AFP.

Last month, astronomers Konstantin Batygin and Mike Brown predicted the existence of what they dubbed Planet Nine, about 10 times more massive than Earth.

Its existence was predicted with mathematical modelling and computer simulations, and was said to exactly explain the strange clumping behavior of a group of dwarf planets in the Kuiper Belt, a field of icy objects and debris beyond Neptune.

Laskar and his team said the search field can be further narrowed if Cassini, due to finish its mission next year, is extended to 2020.

Astronomers expect it would take years to find Planet Nine, if it exists at all.

It would take a very large telescope to spot the planet at that distance, and with no clear idea of where on its very large orbit it is.

Many other planets have been predicted through modelling over the years, mostly wrongly.

In one famous case the science was right — the discovery of Neptune, first predicted from its gravitational pull on Uranus. 

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Earlier this month, on Feb. 6, a giant fireball came screaming through Earth's atmosphere. But the chances that anyone actually saw it are few to none.

This fireball likely exploded with the energy equivalent to 13,000 tons of TNT, but it did so over the Atlantic Ocean more than 600 miles away from the nearest inhabited region.

So, if no one saw or heard this enormous explosion — which, to date, is the largest since the Chelyabinsk meteor rampaged over Russia in 2013 — why are we so sure that it happened?

NASA was the first to publicly report the event, and you might think they would be the most likely to have made the discovery, but no. Even with all of its satellites and a program dedicated to spotting potentially harmful meteors, asteroids, and comets, NASA didn't actually detect the space rock, before or after it entered Earth's atmosphere.

According to Phil Plait— an astronomer and science writer for Slate — NASA was tipped off by another branch of the US government, possibly the military.

The government isn't necessarily interested in space rocks, but when those rocks make an unexpected and relatively large boom anywhere in the world, it tends to spark interest.

While the government isn't about to divulge how it saw this explosion, which was practically invisible to everyone else, Plait offered up a few ideas in his post:

"I can think of three ways to detect a big fireball in this case: Satellite observations, which would image them directly; seismic monitors, which can detect the explosion as the sound wave from the blast moves through the ground; and atmospheric microphones, which can detect the long-wavelength infrasound from an event. This may have been detected by any combination of these (though since it was over the open ocean, seismic monitors seen unlikely)."

With some back-of-the-envelope calculations, Plait estimated that the meteor was no larger than 23 feet across, before it entered Earth's atmosphere.

If the fireball had plunged toward a city instead of the Atlantic, Plait said it would have rattled some windows but, overall, left little to no damage in its wake.

Still, it's slightly unsettling to know that our technology isn't quite ready to spot these large fireballs ahead of time and provide a proper warning — even if it is just to say "Look up!"

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John Glenn described this training exercise as "the weirdest" he'd ever done. Glenn was part of the Mercury Seven, seven astronauts chosen by NASA after President Dwight Eisenhower insisted that all astronauts be test pilots. 

Produced by Emmanuel Ocbazghi. Original reporting by Jessica Orwig.

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A total of 86 rockets, satellites, and shuttles blasted off from launch pads around the world last year. Cape Canaveral Air Force Station was one of the most prolific, but it wasn't number one.

Produced by Zach Wasser

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