China's school-bus-size Tiangong-1 modular space station is expected to fall to Earth in a fiery blaze on or around Easter Sunday.

The US government is tracking the orbit of Tiangong-1 and about 23,000 other human-made objects larger than a softball. These satellites and chunks of debris zip around the planet at more than 17,500 mph — roughly 10 times the speed of a bullet.

However, there are millions of smaller pieces of space junk orbiting Earth, too.

"There's lots of smaller stuff we can see but can't put an orbit, a track on it," Jesse Gossner, an orbital-mechanics engineer who teaches at the US Air Force's Advanced Space Operations School, told Business Insider.

As companies and government agencies launch more spacecraft, concerns are growing about the likelihood of a "Kessler syndrome" event: a cascading series of orbital collisions that may curtail human access to space for hundreds of years.

Here's who is keeping tracking of space junk, how satellite collisions are avoided, and what is being done to prevent disaster on the final frontier.

SEE ALSO: A spacecraft graveyard exists in the middle of the ocean — here's what's down there

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Thousands of launches since the dawn of the Space Race have led to a growing field of space debris. Most space junk is found in two zones: low-Earth orbit, which is about 250 miles up, and geostationary orbit, about 22,300 miles up.

In addition to 23,000 objects the size of a softball or larger — like rocket stages, satellites, and even old spacesuits — there are more than 650,000 objects that are softball-to-fingernail-size.

Another 170 million bits of debris as small as a pencil tip may also exist — including things like explosive bolts and paint flecks.

Source: ESA

Countless pieces of tiny debris were added to orbit in 2007, when China intentionally smashed one of its old satellites with a "kill vehicle." Then in 2009, an old Russian satellite and US satellite collided, adding even more dangerous junk.

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• The funeral for British physicist Stephen Hawking was held on Saturday in Cambridge. 
• Hawking died at the age of 76 on March 14 after living for decades with a degenerative disease.  
• Hawking's ashes will be interred at Westminster Abbey in June, among some of the greatest scientists in history, Isaac Newton and Charles Darwin.
• The ceremony included space-themed music composed specially for Hawking called "Beyond the Night Sky," and his coffin was topped with white "Universe" lilies and white "Polar Star" roses. 

CAMBRIDGE, England (Reuters) - Well-wishers filled the streets of Cambridge on Saturday for the funeral of British physicist Stephen Hawking, hailed by another leading scientist as "an imprisoned mind roaming the cosmos".

Hawking, crippled since a young man by a degenerative disease, beat the odds stacked against him to became the most celebrated scientist of his era. His work ranged from the origins of the universe itself, through time travel and probing black holes in space.

He achieved international renown after the publication of "“A Brief History of Time" in 1988.

His coffin was topped with white "Universe" lilies and white "Polar Star" roses and carried by pallbearers from the University of Cambridge, where he worked. It was greeted by a large crowd outside the church who clapped as it was carried in.

The 76-year-old scientist was mourned by his children Robert, Lucy and Timothy, joined by guests including playwright Alan Bennett, businessman Elon Musk and model Lily Cole.

Eddie Redmayne, the actor who played Professor Hawking in the 2014 film "The Theory of Everything" was one of the readers in the ceremony and Felicity Jones, who played his wife, Jane Hawking in the film also attended the service.

The ceremony included space-themed music composed specially for Hawking called "Beyond the Night Sky", inspired by a poem and quotes from "A Brief History of Time" and whistling and "shh" sounds based on recordings of space.

Astronomer Royal Martin Rees, a personal friend, read from Plato's Apology 40, "The Death of Socrates", which talks of the search for knowledge persisting after death.

Confined to a wheelchair for most of his life after being diagnosed with Motor Neurone Disease when he was 21, Hawking's towering intellect and sheer persistence struck a chord with ordinary people, Rees said in an appreciation published earlier this month.

"Why did he become such a 'cult figure'? The concept of an imprisoned mind roaming the cosmos plainly grabbed people's imagination," he said.

"His name will live in the annals of science; millions have had their cosmic horizons widened by his best-selling books; and even more, around the world, have been inspired by a unique example of achievement against all the odds – a manifestation of amazing will-power and determination."

Hawking's ashes will be interred at Westminster Abbey in June, among some of the greatest scientists in history, Isaac Newton and Charles Darwin.

Writing by Elisabeth O'Leary; Editing by Stephen Powell.

SEE ALSO: Stephen Hawking was my real-life Time Lord: Remembering the genius who inspired countless humans on this rock drifting through space

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• Neutron stars that crash together in space forge valuable metals like silver, gold, and platinum.
• Some heavy periodic elements may be created almost exclusively by such cosmic crashes.
• Europium, one of the least-common elements in the universe, is a candidate and is used in TVs, lasers, and plastics.
• A neutron-star collision discovered through gravitational waves made about 1-5 Earths' worth of the europium, according to a new study.

In October 2017, astrophysicists announced a remarkable discovery: The first-ever detection of two dead stars smashing together.

The collision created gravitational waves, or ripples in spacetime, which were "heard" by the LIGO experiment. But the event — unlike merging black holes— threw off gobs of neutrons (essentially super-heavy-element barf).

This material almost immediately decayed into lighter elements, leading to a bright, radioactive "kilonova" astronomers could see some 85 million to 160 million light-years away from Earth. Light from the energetic breakdown of this material suggest that it led to the unimaginably valuable formation of about 50 Earth masses' worth of silver, 100 Earth masses of gold, and 500 Earth masses of platinum.

Researchers who've pored over the data since last year now think the collision also made 1-5 Earth masses of a very rare element called europium, according to a recent study in The Astrophysical Journal. (They also dialed back the gold-formation estimate to 3-13 Earth masses worth.)

The study could mean that neutron-star collisions are responsible for forging most of the europium and gold we find on Earth, not to mention other key elements.

What europium is and how it's made

Europium is element number 63 on the Periodic Table, and it's a somewhat hard, silvery metal that reacts with oxygen and water — so it's never found in pure form. When it is pure, it's stored in inert gases (e.g. argon) to prevent it from oxidizing and tarnishing.

The element is used to make some red lasers, electronic parts, and the red phosphors of cathode-ray-style television sets. (One estimate suggests there's 0.5-1 gram of europium in every CRT screen.) Its ability to react to ultraviolet light also makes it an anti-counterfeit measure in euro paper currency.

Europium is also seeing newfound use in ultra-bright-red LEDs and — if the technology pans out — could lead to a stable quantum hard drive.

Researchers suspected europium was formed by colliding neutron stars, but couldn't be sure how much until one was detected. Another explanation is that cataclysmic explosions of stars, called supernovas, form most europium and other elements heavier than nitrogen.

A bit of nuclear alchemy called the rapid process or r-process is what drives the creation of such heavy elements.

The r-process goes something like this: As neutron stars move toward each other, a tiny bit of their material gets shot into space at incredible speeds. Those neutrons are very hot and crowded, so they smash together while moving outward, forming giant atomic cores.

Because very big atoms are highly unstable, they almost immediately break apart and decay into smaller atoms — stuff like platinum, gold, silver, and europium.

Fortunately, we don't need a spaceship to find this stuff created by neutron stars — it's here on Earth. Countless smash-ups over the millennia spread around enough of these exotic metals that when our planet formed, they were baked right into its crust.

"The rate of these neutron star mergers in our galaxy is about one every 100,000 years. On human time scales, that's a long time," Duncan Brown, an astronomer at Syracuse University who's a member of the LIGO research collaboration, previously told Business Insider. "But on galactic time scales, when you're creating stars and solar systems, that's not that much time."

What's still uncertain is how much colliding neutron stars might contribute to europium. If LIGO finds more and more colliding neutron stars over the years, it's likely those events — not supernovas — are where the most valuable materials on the planet come from.

SEE ALSO: Scientists cracked one of Einstein's greatest mysteries — now a bizarre new form of astronomy is emerging

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NOW WATCH: Scientists won the Nobel Prize for detecting gravitational waves — here's why that matters

Albert Einstein died on this day 63 years ago, but he remains one of the greatest minds of the 20th century. His contributions to human knowledge are unparalleled.

The physicist conducted groundbreaking research on how our universe functions, formulated the Theory of Relativity, and predicted the existence of gravitational waves a century before we observed them.

Einstein wasn't just brilliant, he was deep: a scientist-philosopher who knew just how to describe the human condition. That genius, combined with the human highs and lows Einstein witnessed during his lifetime, made for a perspective on life that's yet to be matched.

We've compiled a list of Einstein's 15 best quotes, which teach us about the mind, learning, and that crazy thing called life.

Sean Kane contributed to an earlier version of this story. 

SEE ALSO: How Einstein became a suspected spy in a clip from the new TV show 'Genius'

On the passing of time

On being happy

On education

• Russian President Vladimir Putin recently said Russia was developing a nuclear-powered torpedo that could detonate a "massive"nuclear weapon.
• Such a device might create a 300-foot tsunami if exploded in the right location and could rain long-lasting radioactive fallout on a coastal target.
• Experts have described the hypothetical weapon as a "doomsday" device, saying it could spread unprecedented and long-lived radioactive fallout.
• But one researcher said such a weapon would be "stupid," as it'd greatly limit its damage compared with an airburst.

During Russian President Vladimir Putin's address to the Federal Assembly on March 1, he described a plethora of nuclear weapons he said Russia was developing.

One of these proposed weapons, an autonomous submarine, stood out among the depictions of falling warheads and nuclear-powered cruise missiles.

According to a Kremlin translation (PDF) of Putin's remarks, he said the autonomous drone would quietly travel to "great depths," move faster than a submarine or boat, "have hardly any vulnerabilities for the enemy to exploit," and "carry massive nuclear ordnance."

"It is really fantastic, he said, adding: "There is simply nothing in the world capable of withstanding them."

He also said Russia finished testing a nuclear-powered engine for the drones in December.

"Unmanned underwater vehicles can carry either conventional or nuclear warheads, which enables them to engage various targets, including aircraft groups, coastal fortifications, and infrastructure," he said.

Putin did not refer to the device by name in his speech, but it appears to be the Oceanic Multipurpose System Status-6, also known as Kanyon or Putin's "doomsday" machine.

The Russian government reportedly leaked a diagram of such a weapon in 2015 that suggested it would carry a 50-megaton nuclear bomb about as powerful as Tsar Bomba, the largest nuclear device ever detonated.

Nuclear physicists say such a weapon could cause a local tsunami, though they question its purpose and effectiveness, given the far more terrible destruction that nukes can inflict when detonated aboveground.

Why Putin's 'doomsday' device could be terrifying

A nuclear weapon detonated below the ocean's surface could cause great devastation.

The US's underwater nuclear tests of the 1940s and '50s, including operations Crossroads Baker and Hardtack I Wahoo, demonstrated why.

These underwater fireballs were roughly as energetic as the bombs dropped on Hiroshima or Nagasaki in August 1945. In the tests, they burst through the surface, ejecting pillars of seawater more than a mile high while rippling out powerful shockwaves.

Some warships staged near the explosions were vaporized. Others were tossed like toys in a bathtub and sank, while a few sustained cracked hulls and crippled engines. Notably, the explosions roughly doubled the height of waves to nearby islands, flooding inland areas.

"A well-placed nuclear weapon of yield in the range 20 MT to 50 MT near a sea coast could certainly couple enough energy to equal the 2011 tsunami, and perhaps much more," Rex Richardson, a physicist who researches nuclear weapons, told Business Insider, referring to the Tohoku earthquake and tsunami that killed more than 15,000 people in Japan.

"Taking advantage of the rising-sea-floor amplification effect, tsunami waves reaching 100 meters in height"— about 330 feet — "are possible," Richardson said.

Richardson and other experts have also pointed out that a near-shore blast from this type of weapon could suck up tons of ocean sediment, irradiate it, and rain it upon nearby areas — generating catastrophic radioactive fallout.

"Los Angeles or San Diego would be particularly vulnerable to fallout due to the prevailing onshore winds," Richardson said, adding that he lives in San Diego.

The problem with blowing up nukes underwater

Greg Spriggs, a nuclear-weapons physicist at Lawrence Livermore National Laboratory, said a 50-megaton weapon "could possibly induce a tsunami" and hit a shoreline with the energy equivalent to a 650-kiloton blast.

But he said it "would be a stupid waste of a perfectly good nuclear weapon."

That's because Spriggs believes it's unlikely that even the most powerful nuclear bombs could unleash a significant tsunami after detonating underwater.

"The energy in a large nuclear weapon is but a drop in the bucket compared to the energy of a [naturally] occurring tsunami," Spriggs previously told Business Insider. "So any tsunami created by a nuclear weapon couldn't be very large."

For example, the 2011 tsunami in Japan released about 9.3 million megatons of TNT energy. That's hundreds of millions of times as much as the bomb dropped on Hiroshima in 1945 and roughly 163,000 times as much as the Soviet Union's test of Tsar Bomba on October 30, 1961.

Plus, Spriggs said, the energy of a blast wouldn't all be directed toward shore — it would radiate outward in all directions, so most of it "would be wasted going back out to sea."

A detonation several miles from a coastline would deposit only about 1% of its energy as waves hitting the shore. That scenario may be more likely than an attack closer to the shore, assuming US systems could detect an incoming Status-6 torpedo.

But even if such a weapon were on the doorstep of a coastal city or base, its purpose would be questionable, Spriggs said.

"This would produce a fraction of the damage the same 50 MT weapon could do if it were detonated above a large city," Spriggs said. "If there is some country out there that is angry enough at the United States to use a nuclear weapon against us, why would they opt to reduce the amount of damage they impose in an attack?"

Is the doomsday weapon real?

Putin fell short of confirming the existence of Status-6, though he did say the December tests of its power unit "enabled us to begin developing a new type of strategic weapon" to carry a huge nuclear bomb.

The Trump administration even addressed the possible existence of the weapon in its most recent nuclear posture review.

In a 2015 article in Foreign Policy, Jeffrey Lewis, an expert on nuclear policy at the Middlebury Institute of International Studies, dubbed the weapon "Putin's doomsday machine."

He wrote that there was speculation that the underwater weapon might be "salted," or surrounded with metals like cobalt, which would dramatically extend fatal radiation levels from fallout— possibly for years or even decades — since the burst of neutrons emitted in a nuclear blast could transform those metals into long-lived, highly radioactive chemicals sprinkled all over.

"What sort of sick bastards dream up this kind of weapon?" Lewis wrote, noting that such salted weapons were featured in the 1964 science-fiction Cold War parody film"Dr. Strangelove."

To Lewis, it doesn't necessarily matter whether Status-6 is real or a psychological bluff designed to prevent the US from attacking Russia or its allies.

"Simply announcing to the world that you find this to be a reasonable approach to deterrence should be enough to mark you out as a dangerous creep," he said.

SEE ALSO: People are stockpiling iodine pills to guard against nuclear fallout — but they won't stop 99.8% of radioactive exposure

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NOW WATCH: Here's how easy it is for the US president to launch a nuclear weapon

• Stephen Hawking's final paper was just published in the Journal of High Energy Physics.
• The paper predicts there are not infinite parallel universes in the multiverse, but instead a limited number.
• These universes would have laws of physics like our own, the paper says.
• It also explains how we might be able to see proof of this theory and find evidence for parallel universes by finding gravitational waves.

Ten days before he died, theoretical physicist Stephen Hawking submitted a final paper for publication.

That paper — titled "A smooth exit from eternal inflation?" — has now been published in the Journal of High Energy Physics. In it, Hawking and coauthor Thomas Hertog lay out a theory on the origin of the universe that might settle a few lingering questions.

One popular understanding of the Big Bang suggests that our universe is one in a "multiverse" of infinite parallel universes. The paper posits that the other universes out there follow the same laws of physics that exist in our universe.

This makes the number of possible universes much more manageable and testable, since it's no longer an effort to understand infinite universes that could have different underlying rules of physics and chemistry.

"We are not down to a single, unique universe, but our findings imply a significant reduction of the multiverse, to a much smaller range of possible universes," Hawking said in a statement last fall.

The paper also implies that it might be possible to test this theory. Physicists could look for evidence of other universes using tools designed to measure ripples in spacetime — also known as primordial gravitational waves — that would have been generated by the universe's initial expansion from the Big Bang.

Inflation that never stops

Hawking helped develop the theory that led to the idea of infinite parallel universes.

That concept relies on something known as "eternal inflation." The thinking, in essence, is that after the Big Bang, the universe — or all the universes — started to expand, but that process never stopped in some places. Our universe, by that logic, is just one pocket where that exponential inflation stopped and stars and galaxies formed. (Our universe is still expanding, but not in that rapid way.)

"The usual theory of eternal inflation predicts that globally our universe is like an infinite fractal, with a mosaic of different pocket universes, separated by an inflating ocean," Hawking said in an interview last fall, according to the University of Cambridge.

"The local laws of physics and chemistry can differ from one pocket universe to another, which together would form a multiverse. But I have never been a fan of the multiverse. If the scale of different universes in the multiverse is large or infinite, the theory can’t be tested."

Hertog told Cambridge that the physics that would account for infinite parallel universes break down when applied to the theory of eternal inflation.

A boundary to eternal inflation

Hawking and Hertog's new paper relies on string theory, a branch of physics that tries to reconcile quantum physics with gravity and Einstein's theory of relativity. They came up with a new idea of eternal inflation that relies on a boundary at the beginning of time.

"When we trace the evolution of our universe backwards in time, at some point we arrive at the threshold of eternal inflation, where our familiar notion of time ceases to have any meaning," Hertog told Cambridge.

Starting from that boundary, the new theory predicts a finite structure of universes emerging from the Big Bang.

If this theory is proved true, it would suggest that other universes like our own could have emerged at that point. And there could even be primordial gravitational waves that match the inflation of the universe. But this new model is still far from proven, and physicists will need more data and a better understanding of string theory before that's possible.

The existing instruments used to look for gravitational waves are probably not sensitive enough to find evidence of this theory, according to Hertog. But planned future instruments like the European space-based LISA gravitational wave observatory might be.

If we can detect that evidence, we'll better understand how our universe and its laws came into being after the Big Bang — and we might know more about whatever other universes are out there.

SEE ALSO: 15 of the most remarkable and memorable things Stephen Hawking ever said

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There is something gravely wrong with the ultimate fate of the Death Star, a moon-size weapon in the "Star Wars" movies, and physicists think you should know about it.

The Death Star meets its final doom in "Return of the Jedi," the epic conclusion to the original "Star Wars" saga.

The colossal ship is orbiting the forested Sanctuary moon of the planet Endor and, after it's blown up, the Rebel Alliance and its hairy Ewok friends party in the trees. Everyone and everything is hunky-dory.

But ask a physicist — or a dozen, as we've done — what happens when you detonate a giant metal sphere above a lush green world. The answer is downright chilling.

"The Ewoks are dead. All of them," said one researcher and self-professed "Star Wars" fan, who wrote a white paper in 2015 that supported his conclusion.

Each scientist who responded to our emails quibbled over the exact details, yet a strong consensus emerged in support of a popular fan theory: The "Endor Holocaust" is inevitable, and that would be a threat to the plausibility of any future movies (galactic bankruptcy be damned).

Here's why.

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The "Endor Holocaust" fan theory dates back to 1997, when it first appeared on a website called TheForce.net. Curtis Saxton, an astrophysicist and "Star Wars" super-fan, wrote it as part of a technical series that analyzes the movies frame-by-frame with scientific rigor.

Source: TheForce.net

Saxon's 10,000-word essay about the Endor holocaust claims that the doom of Endor and the cuddly, warmongering Ewoks who live there "is an inevitable consequence of observable facts."

The rebels' attack on the Death Star turns it into fine metallic bits, Saxton argues. The debris then rains down on Endor, burns up into a toxic sooty fallout, and sparks global firestorms.

But many of Saxton's various measurements are open to interpretation, since depictions of the Death Star, Endor, and other details are inconsistent from one scene to the next.

Source: TheForce.net

Every two years, the National Science Foundation is required to tell the president how the US is doing in regard to science and engineering.

"As economies worldwide grow increasingly knowledge-intensive and interdependent, capacity for innovation becomes ever more critical," the NSF says in its latest report, titled "Science & Engineering Indicators 2018."

The news is OK, but not great. Americans are increasingly interested in environmental issues, the report says, and relative to previous years, they're expressing more concern about climate change and humanity's role in it. They also trust scientists more than roles in any other institution aside from the military.

But the US lags behind dozens of countries in the rate of awarding bachelor's and advanced degrees in science, technology, math, or engineering.

The American public also isn't doing much better on 10 simple questions the NSF asks to test the public's understanding of science.

Scroll down to see the questions the NSF asked for the latest report, see how many answers you can get right, and then compare how 11 countries who asked the same science questions performed. 

Kelly Dickerson contributed to this post.

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Question 1:

The correct answer...

Scientists estimate that Earth's core is more than 10,000 degrees Fahrenheit — nearly the temperature found on the surface of the Sun.

How the US and other nations did:

After a long work day, most of us happily collapse into a couch and binge-watch our favorite show.

But Linden Gledhill, a Philadelphia-based pharmaceutical biochemist, retreats to his basement lab. There, he builds custom gear so that he can record the beautiful, complex, and sometimes very weird intersection of science, art, and nature.

For example, Gledhill hacked an old hard drive into a camera shutter 10 times faster than anything in a store. He's also rigged up a machine to create snowflakes on demand and patented a super-resolution photography rig.

Gledhill uploads his experimental photos and video to Flickr, and art directors and producers take notice — not only because he's creative, but also because he's good. He's earned commissions for TV commercials and music videos, and most recently, high-tech prints of his photos were donned by fashion models.

For the past couple of years, Gledhill has been playing with a tiny dish of liquid that sits on a speaker. Called a cymascope, it's designed to create and tune repeating patterns of waves, like those formed in wine by rubbing the rim of a crystal glass to make it vibrate or "sing." These cyclical ripples, also called cymatics, travel far faster than human eyes can see, so he uses ultra-high-frame-rate cameras slow them down and record their secrets.

"It allows you to see the individual vibration states throughout the cycle. That's pretty cool. Typically you don't get to see that," Gledhill told Business Insider. "Typically what you see is a fixed pattern or a changing pattern based on the frequencies you play through the liquid."

Here's a look at some of Gledhill's newest experimental and hallucinatory imagery.

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Gledhill started experimenting with standard macro-photography camera gear. He took images of a roughly one-inch-wide, quarter-inch-deep dish of water vibrated by a speaker.

The camera peers down on the dish through a an LED light ring, which evenly illuminates the liquid in the dish. (In this case, malt whiskey.) The light ring is visible in a reflection at the center of this image.

Here's a photo of Gledhill's cymascope rig at his home.

• Having your shower curtain stick to you can be a pesky nuisance.
• The reason behind this annoying phenomenon is the "Bernoulli Effect".
• The physics behind this effect also explains, in part, how airplanes stay airborne.

What these temperatures call for is a nice, refreshing shower — if only it weren't for that pesky shower curtain closing in and clinging to you the moment you hop in and switch on the water. Why does this happen?

The answer to that question lies in physics.

"Since a shower curtain is large yet light, it reacts to a small vacuum created in the shower cabin," Ohle Claussen of the Max Planck Institute for Dynamics and Self-Organisation explained to Business Insider. At least two physical effects cause this when you shower.

The vacuum sucks the curtain into the shower cubicle.

You can easily create a similar vacuum yourself by taking a thin piece of paper or a receipt and holding it to your lower lip. If you blow hard now, the note will not be pressed down, but will raise. Andreas Baumer of Business Insider tried it, as you can see in the above photo.

What he experienced is called the Bernoulli effect, which is part of the reason why airplanes can fly. It was the mathematician Daniel Bernoulli who noted that, in a space where the flow velocity is higher than in its surrounding environment, the air pressure there is always lower compared with its surroundings.

So if you blow over the paper strip, the speed of the air there is higher than under the paper, because the air below is, at most, moving only very slightly. This reduces the pressure of the air above the paper, creating a vacuum that sucks the sheet upwards. Your "over-friendly" shower curtain can also be attributed to this phenomenon.

Air from outside flows in and a pressure drop occurs

"When air enters the area of higher flow velocity, it must be accelerated in order to adapt to this velocity," Claussen explained. "In fluid mechanics, such an acceleration is combined with a pressure drop as the driving force. The additional kinetic energy the air particles receive is as a result of the fact that the higher air pressure in the area of slow flow works on these air particles when they reach the area of faster flow".

So pressure and speed are always connected where air flow is involved. The place of highest speed is also always the place of lowest pressure. "So if your shower head emits water at high speed in the shower cabin, the air in the cabin is carried away," says Claussen. "Consequently, air must flow in from the outside and be accelerated, resulting in a drop in pressure."

David Schmidt, a scientist from Massachusetts, highlighted a second cause for the negative pressure, using a computer that simulated the movement of water droplets. It showed that splitting water droplets in the lower part of the shower create a vortex that also contributes to negative air pressure.

So how do you stop your shower curtain sticking to you?

This effect is almost as great as the Bernoulli effect, according to Claussen. And the discovery was only made in 2001. This shows how small the occurring forces are but as the shower curtain is simultaneously large and light, it can be carried away by even the slightest dip in pressure.

The closer the air brings the curtain to the person in the shower, the more the Bernoulli effect is enhanced: "The same amount of air must now flow through a smaller gap and must therefore flow even faster in that small area. This increases the negative pressure at the point of approach until contact occurs.

The real question is: what can you do to put a stop to your overly affectionate shower curtain's embrace? Try attaching some weights to the curtain's base, inserting a lead tape through the hem, sticking the curtain to the tub with water or avoiding pulling it across so it's taut when you shower!

SEE ALSO: Your blood is actually never blue — here's why it's always red

Join the conversation about this story »

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Inhaling helium and talking like Daffy Duck is a classic party trick. But not many know how helium works. Helium is much lighter than air, so sound waves move much faster through the gas. This amplifies the higher frequencies in your voice. The gas sulfur hexafluoride works in the opposite way. The following is a transcript of the video.

It’s a classic party trick- suck down a balloon and you’ll sound like Daffy Duck every time. But helium isn’t the only gas that’ll change the way you talk. So what’s going on here?

Your voice is as unique as your fingerprint. Janice didn’t inhale a balloon full of helium. That’s just her “normal” voice. So, let's take a look at how that's even possible. The sound of your voice starts in your voice box, or larynx. It’s a two-inch piece of cartilage at the top of your throat. In the box are two stretchy strands of tissue, your vocal cords. Which vibrate against each other at a specific frequency when you talk.

Women generally have thinner, shorter, tighter vocal cords than men. So, their vocal cords vibrate faster which generates a higher pitched voice. That sound is called the fundamental frequency of your voice. On its own it just sounds like a simple buzzing. But when it reaches your vocal tract, the sound waves start bouncing around. Those reflections interfere with each other. Which creates a mix of other frequencies, that you can detect with a spectrogram. So even though your voice starts out as one frequency, it ends up as a mix of multiple ones.

And that's where helium comes into play. Helium is lighter than air. Which means sound moves faster through helium than through air – nearly 3 times faster, in fact. So the sound waves bounce around faster in your vocal tract, which amplifies the higher frequencies in your voice. It's sort of like how speeding up your voice makes it sound higher.

But hold on a sec. These people aren't inhaling helium. They're sucking down sulfur hexafluoride, which is six times heavier than air. So sound waves move slower through it, which amplifies the lower frequencies in your voice. But here's the fascinating thing. The pitch of your voice hasn't changed when you inhale either gas, because your vocal cords move at the same rate no matter what gas you're breathing. So your fundamental frequency stays, well fundamental.

Regardless of whether you want to sound like Daffy Duck or James Earl Jones, keep in mind that inhaling anything but air can be dangerous. Especially when the gas is denser than air, because it will sink to the bottom of your lungs. And you may have to get it out like this. What questions do you have about the human body? Let us know in the comments and thanks for watching.

Join the conversation about this story »

• A total lunar eclipse, or blood moon, will happen overnight on July 27.
• The eclipse will be colored orange-red due to sunlight passing through Earth's atmosphere and bouncing off the moon.
• The eclipse is slated to last nearly 1 hour 43 minutes — the longest in about a century.
• North America won't see the eclipse, since the moon will be below the horizon, but anyone can watch via a live video webcast.

Huge swaths of Earth are in for a special astronomical treat in late July: the longest total lunar eclipse in roughly 100 years.

During the evening of July 27 and into the early morning of July 28, Earth will pass between the sun and the moon to cast a shadow on our 4.5-billion-year-old satellite.

Earth's shadow isn't a dull gray, though.

It ranges from orange to an eerie blood-red hue if you're right in the middle, which is precisely where the moon will be this time around.

Here's that works.

How a total lunar eclipse colors the moon red

A total lunar eclipse and a total solar eclipse are similar, if not the reverse of one another, but their appearances are significantly different.

During a solar eclipse, the moon passes between Earth and the sun to cast its shadow on our planet. The shadow is colorless because the moon has no atmosphere to scatter or refract any sunlight.

Earth, of course, is a different story.

Our planet's nitrogen-rich atmosphere takes white sunlight, a mix of all colors of the spectrum, and scatters around the blue colors. This makes the sky appear blue during the day and the sun yellow.

Around sunset and sunrise, the light reaching our eyes has been more throughly scattered, so much that blues are nearly absent. This makes the sun and its light appear more orange or even red.

Roughly 240,000 miles away at the moon, the Earth would look quite stunning as the same air, like a big lens, refracts that tinged light toward the full moon.

"If you were standing on the moon's surface during a lunar eclipse, you would see the sun setting and rising behind the Earth,"David Diner, a planetary scientist at NASA's Jet Propulsion Laboratory, wrote in a blog post. "You'd observe the refracted and scattered solar rays as they pass through the atmosphere surrounding our planet."

This is why lunar eclipses are orange-red: All of that colored light is focused on the moon in a cone-shaped shadow called the umbra.

The moon is also covered in ultra-fine, glass-like rock dust called regolith, which has a special property called "backscatter." This bounces a lot of light back the same way it came from, in this case toward Earth (Backscattering also explains why full moons are far brighter than during other lunar phase.)

So, when we're looking at the moon during a total lunar eclipse, we're seeing Earth's refracted sunset-sunrise light being bounced right back at us.

The red color is never quite the same from one lunar eclipse to the next due to natural and human activities that affect Earth's atmosphere.

"Pollution and dust in the lower atmosphere tends to subdue the color of the rising or setting sun, whereas fine smoke particles or tiny aerosols lofted to high altitudes during a major volcanic eruption can deepen the color to an intense shade of red," Diner said.

This total lunar eclipse will also happen during what's called a "micro" moon, or the opposite of a super moon. This happens because the moon's orbit isn't perfectly circular, so it appears larger at times and smaller at others during its roughly 29-day-long orbit around Earth. (In this case it will look a bit smaller.)

Where and when to see the total lunar eclipse

North America will be out of luck this year, since the moon will be below the horizon. You can still watch on a live webcast, though, if you're located there.

But if the weather cooperates, most of eastern Africa, the Middle East, and central Asia should see the full and total lunar eclipse. Scientists in Antarctica should also have a great view.

Europe, eastern Asia, Australia, Indonesia, and other regions will enjoy a partial lunar eclipse, where the moon passes partly through Earth's shadow.

The partial eclipse begins when the moon first touches the penumbra or outer shadow of Earth. According to NASA, that should happen at 17:14 Universal Time on July 27.

The total eclipse — when the moon is fully inside the red-hued umbra of Earth — starts at 19:30 UT and ends at 21:13 UT. That's a full 1 hour 43 minutes, which is just four minutes shy of the longest total lunar eclipse possible, according to EarthSky.

The partial eclipse will resume immediately afterward, as the moon passes out of Earth's shadow, and the whole event will be over at 23:28 UT (early on July 28, depending on where you live).

SEE ALSO: Solar eclipse die-hards use this clever trick to see totality longer than anyone else

DON'T MISS: What a 'Beaver Moon' actually means

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NOW WATCH: This NASA animation shows what this month's stunning lunar eclipse would look like on the moon

Stephen Hawking has died peacefully at home at the age of 76.

The world-renowned physicist was told he would only have two years to live when diagnosed motor neuron disease, a rare form of ALS, aged 21.

Some 55 years later, it is safe to say he defied the odds and helped transform the way scientists view black holes and the universe.

As well his contribution to science, Hawking was a philosopher of sorts, a powerful political voice, and had a good line in acerbic wit.

These 15 quotes show Hawking's approach to science and to life in general — and take you inside the mind of a genius.

SEE ALSO: Renowned physicist Stephen Hawking has died at age 76

On disability

"My advice to other disabled people would be, concentrate on things your disability doesn’t prevent you doing well, and don't regret the things it interferes with. Don’t be disabled in spirit, as well as physically."

[The New York Times, 2011]

On priorities

"My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all."

["Stephen Hawking's Universe," 1985]

On free will

"I have noticed that even people who claim everything is predetermined and that we can do nothing to change it, look before they cross the road."

["Black Holes and Baby Universes and Other Essays," 1994] 

Stephen Hawking was a theoretical physicist who pioneered new understandings of black holes, the universe, and how much one person can achieve.

Hawking died early in the morning on March 14, 2018 — Pi Day and Albert Einstein's birthday.

In passing, he left behind an incredible legacy, especially as a person who struggled with ALS, a neurodegenerative disease that confined him to a wheelchair for the vast majority of his life.

Though Hawking's life has filled many books and a feature-length film, we've summarized some of the most memorable and notable moments in the graphical timeline below.

Remembering Stephen Hawking:

• Stephen Hawking has died at 76 — here are some of the most remarkable and memorable things he ever said
• These 15 photos show how Stephen Hawking defied his disability and lived an incredible life 
• Stephen Hawking was only expected to live a few years after being diagnosed with ALS at age 21 — here's what the disease is
• Stephen Hawking died on a day that is cosmically connected to Albert Einstein and Pi
• The man who helped Stephen Hawking achieve his lifelong dream of experiencing zero gravity remembers what it was like to watch the acclaimed physicist break free of his wheelchair
• Stephen Hawking was rumored to run over the toes of people he didn't like with his wheelchair
• Stephen Hawking had a 'sense of humor as vast as the universe': unique tributes flood in for esteemed scientist

Join the conversation about this story »

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• Stephen Hawking died in his home in Cambridge at age 76 on March 14, 2018.
• The physicist pioneered new ways of understanding black holes and the universe.
• His popular-science books — especially "A Brief History of Time" — may persist as some of his greatest achievements.

Stephen Hawking, who's known for his explorations of time and discovering that black holes can evaporate, died Wednesday at age 76 in his home in Cambridge.

I was lucky enough to see him speak in person twice, but I first got acquainted with the British physicist during a long Boy Scout trip to the middle of nowhere, Ohio.

Hawking, of course, wasn't riding on our body-odor-filled bus. Instead, I saw his image on a paperback copy of his 1988 book, "A Brief History of Time: From the Big Bang to Black Holes". In the photo, the bespectacled author sat in a wheelchair in front of a star field.

I don't recall why a friend handed me the book. But that introduction to Hawking's writing influenced the arc of my life, and undoubtedly that of millions of other people.

How Hawking helped change me with words

Like many tweens-going-on-teens in the 1990s, I was trying to fit in at school with limited success.

"A Brief History of Time" became a magical escape hatch. In reading it, I could leave behind probing questions about girls I liked, peer pressure to make a clown out of myself (which I excelled at), and chaotic and sometimes cruel social circles.

Instead, I could join Hawking on fantastical adventures to the edges of black holes and inside time-traveling spacecraft; shrink down to the infinitesimal scale of subatomic particles; and journey to the birth and eventual death of the universe. He was like a Time Lord from the show "Doctor Who," though he scurried about the universe via words instead of a phone booth.

The book — which had sold millions of copies even then — was dense, for sure. But to me it read like a riveting sci-fi tale and murder mystery rolled into one. And it was real. What Hawking wrote represented a digestible guide to the limits of human knowledge.

I had only a crude knowledge of mathematics, so I didn't understand half of what Hawking wrote, at least at first. Yet his prose was eminently readable. I read the book cover-to-cover, again and again, extracting new understanding each time.

"We find ourselves in a bewildering world. We want to make sense of what we see around us and to ask: What is the nature of the universe? What is our place in it and where did it and we come from? Why is it the way it is?" Hawking wrote.

His book not only helped answer those questions for my teenage self, but also instilled in me new curiosities, such as "Is there a theory of everything?" and "Will we ever detect evidence of multiple universes?"

More importantly, Hawking revealed to me how science was thought through and performed.

The things that once felt exciting and mysterious to me, like astrology, ghosts, and UFOs, suddenly seemed foolish. Why clamor for evidence of the occult when the greatest source of mystery in our existence — the universe itself — was at our fingertips?

Smitten by the ultimate

I eventually returned the book to my friend in a dog-eared and tattered state. But its wonder stuck with me.

Hawking — whose struggle with the neurological disease ALS left him increasingly unable to move his body — summoned the courage and resolve to turn his condition into a gift. He used it to formulate bold ideas, put them forth with careful and thoughtful writing, and develop an uncanny ability to make the exceedingly complex comprehensible (and at times hilariously entertaining).

His work helped me see the purpose and excitement of learning to do math and science. It's also why Hawking and "A Brief History of Time" are the first two things I think of when asked why I became a science writer.

The book was my first deep-dive exposure to the technically challenging, murky frontiers of human knowledge. It gave me the desire and the language to chase the ultimate in my career. Hawking's work is probably why I'm still smitten by absurdly complex topics like gravitational waves, black holes, nuclear physics, and space exploration. And it's why I spend my workdays striving to understand these frontiers and their profound, surprising relevance. (Have a gold or platinum ring? Thank a pair of colliding neutron stars.)

Hawking was not perfect by any means — no one is — and he had a lot of help in his enterprise. But now more than ever with his passing, I hope others will continue to find the boundless yet grounded curiosity he helped me discover at a young age.

I hope my work will, like Hawking's did for me, spur readers to look up at the night sky (preferably in the middle of nowhere) and see more than "just" moons, planets, stars, and galaxies. Hopefully they will find and understand the beauty and interconnectedness of the universe, how little we know about it, and just how much we have yet to learn as a young alien species stuck on a rock that's drifting through the void.

This story was originally published on March 14, 2018, at 5:49 p.m. ET.

Remembering Stephen Hawking:

• A brief history of Stephen Hawking's time on planet Earth in one chart
• Stephen Hawking has died at 76 — here are some of the most remarkable and memorable things he ever said
• These 15 photos show how Stephen Hawking defied his disability and lived an incredible life
• Stephen Hawking was only expected to live a few years after being diagnosed with ALS at age 21 — here's what the disease is
• Stephen Hawking died on a day that is cosmically connected to Albert Einstein and Pi
• The man who helped Stephen Hawking achieve his lifelong dream of experiencing zero gravity remembers what it was like to watch the acclaimed physicist break free of his wheelchair
• Stephen Hawking was rumored to run over the toes of people he didn't like with his wheelchair
• Stephen Hawking had a 'sense of humor as vast as the universe': unique tributes flood in for esteemed scientist

Join the conversation about this story »

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• Stephen Hawking died at age 76 on Wednesday.
• The world-renowned physicist worked on an Emmy Award-winning TV show called "Stephen Hawking's Favorite Places" before he passed away.
• In the show, Hawking flies around in a spaceship called the "S.S. Hawking" and explores his favorite cosmic mysteries.
• CuriosityStream released the final episode several weeks early and is streaming the three-part series for free for a limited time.

Stephen Hawking, who died today at age 76, was known for his work on the science of time travel and black holes.

The British physicist penned several bestselling books and even worked on an Emmy Award-winning documentary trilogy, called "Stephen Hawking's Favorite Places."

In the show, which is one of the last Hawking ever worked on, he flies around in a spaceship called the "S.S. Hawking" and explores deep scientific mysteries.

The show was created by CuriosityStream, and its description reads: "Mixing recollections from his childhood and family life that inspired his work as a scientist, he goes in search of the ultimate mystery: the theory of everything. Along the way, time travel and a precarious free fall to Venus, plus questions about aliens, God, and truth, offer unprecedented insight into this genius mind."

CuriosityStream planned to release the third and final episode, which in part dives into Hawking's fears about artificial intelligence, in mid-April.

But a representative for the company told Business Insider that, following the death of Hawking, its creators decided to release the last episode today.

Through March 23, Anyone can also watch the series for free for a limited time. It's normally packaged in a streaming subscription that costs between $2.99 and $11.99 per month.

You can find all of the "Stephen Hawking's Favorite Places" episodes at curiositystream.com/hawking.

Remembering Stephen Hawking:

• Stephen Hawking was my real-life Time Lord: Remembering the genius who inspired countless humans on this rock drifting through space
• A brief history of Stephen Hawking's time on planet Earth in one chart
• Stephen Hawking has died at 76 — here are some of the most remarkable and memorable things he ever said
• Stephen Hawking was only expected to live a few years after being diagnosed with ALS at age 21 — here's what the disease is
• Stephen Hawking died on a day that is cosmically connected to Albert Einstein and Pi
• Stephen Hawking had a 'sense of humor as vast as the universe': unique tributes flood in for esteemed scientist

Join the conversation about this story »

NOW WATCH: Stephen Hawking warned us about contacting aliens, but this astronomer says it's 'too late'

Stephen Hawking died early in the morning on March 14, 2018 — Pi Day and Albert Einstein's birthday— but left behind one of the most incredible legacies for a human being on Earth.

Hawking was a theoretical physicist who pioneered new understandings of black holes and the cosmos at large. What's more, he did so while struggling with a severe neurodegenerative disease that confined him to a wheelchair for the vast majority of his life.

The world-renowned scientist carefully contemplated and composed his thoughts with a special eye-tracking computer, and those words — many of them humorous— continue to inspire generations of people who were curious about how the universe works, where it came from, and where it may be headed.

Hawking supplied no shortage of remarkable insights about life, love, and science. Below, we've done our best to collect the most memorable things he said in his books, essays, interviews, TV show appearances, and more.

On coping with his disability:

On his life outlook:

On science and religion:

• Stephen Hawking is named as coauthor on a paper submitted March 4 — 10 days before he died.
• It sets out a way of testing whether other universes are real.
• Its mathematical theories could be tested with a deep-space probe.

Stephen Hawking submitted his final scientific paper just a week and a half before he died, and it lays the theoretical groundwork for discovering a parallel universe.

Hawking, who died Wednesday at 76, was coauthor to a mathematical paper that seeks proof of the "multiverse" theory, which posits the existence of many universes other than our own.

The paper, called "A Smooth Exit from Eternal Inflation," had its latest revisions approved March 4, 10 days before Hawking's death.

According to the Sunday Times newspaper, the paper is due to be published by an unnamed "leading journal" after a review is complete.

ArXiv.org, the Cornell University website that tracks scientific papers before they are published, has a record of the paper including the March 2018 update.

According to The Sunday Times, the paper sets out the mathematics necessary for a deep-space probe to collect evidence that might prove that other universes exist.

The highly theoretical work posits that evidence of the multiverse should be measurable in background radiation dating to the beginning of time. This in turn could be measured by a deep-space probe with the right sensors.

Thomas Hertog, a physics professor who coauthored the paper with Hawking, said the paper aimed "to transform the idea of a multiverse into a testable scientific framework."

Hertog, who works at KU Leuven University in Belgium, told The Sunday Times he met with Hawking in person to get final approval before submitting the paper.

The newspaper said that if such proof were ever found, it would make the scientists behind it likely candidates for a Nobel Prize.

However, since Nobel Prizes cannot be awarded posthumously, Hawking would be ineligible to receive it.

Join the conversation about this story »

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• The vernal or spring equinox of 2018 happens Tuesday, March 20.
• Earth's rotation does not cause equinoxes.
• Equinoxes occur when Earth's tilted axis is perpendicular to the sun's rays.
• During an equinox at Earth's equator, the sun appears almost directly overhead.

The year's spring equinox, also called the March or vernal equinox, falls on Tuesday at precisely 12:15 p.m. EDT.

To people who live in Earth's northern hemisphere, this astronomical event signals the arrival of spring, winter's end, and the increasingly warm and brighter days that come with the pending arrival of summer.

For those in the southern hemisphere, though, it's now the fall: The days are growing shorter, the weather is cooling off, and sunlight is growing dimmer as winter approaches.

What drives this all-important seasonal clock?

Technically, two things: Earth's tilted axis and the planet's orbit around the sun.

How the spring equinox works

The Earth orbits the sun once every 365 days and 6 hours. Our planet also rotates once per day around a tilted axis.

That tilt is about 23.5 degrees (for now) and bathes different parts of the world with various intensities of light over the course of a year. Meanwhile, the planet's rotation keeps the heating even, sort of like a 7,917-mile-wide rotisserie chicken made of rock and a little water.

The spring equinox occurs when the sun's warming rays line up perpendicular to Earth's axial tilt:

If you stand directly on the equator at noon in the Eastern Time time zone at noon, the sun will appear more or less directly overhead. Your shadow will also be at its absolute minimum.

The sun also sets and rises roughly 12 hours apart during the equinox.

But this moment won't last as the Earth makes its way around the sun at a speed of roughly 66,600 mph.

Our planet's orbit is elliptical and its center of gravity slightly offset from the sun, so the time it takes to cycle through the seasons isn't perfectly divvied up.

About 92 days and 19 hours after the spring equinox, the Earth will reach its summer solstice, or when the most direct rays of the sun reach their northernmost latitude, called the Northern Tropic (or Tropic of Cancer). Another 93 days and six hours later, the fall or autumnal equinox will occur.

Then it's another 89 days and 19 hours to the winter solstice — when the most direct sunlight strikes the Southern Tropic (or Tropic of Capricorn) — and another 89 days to get back to the spring equinox.

Some satellites fly around Earth in a geosynchronous orbit, which means they move fast enough to hover above one spot on the planet.

This creates a great opportunity to photograph the planet over the course of the year and see how the the angle of sun changes.

NASA's Goddard Space Flight Center created the animation below using geosynchronous satellite images taken over Africa, and it clearly shows the seasonal progression:

What about the egg-balancing trick?

That whole balance-an-egg-on-its-end-during-the-equinox business is a myth.

You can balance an egg any old time you want, thanks to very small pores in its shell.

Those pores create nearly invisible dimples in the shell upon which a (very, very) patient person can stand up the egg.

And don't look for any gravitational interplay between Earth and the sun to help you out; it's far too weak to make a noticeable difference.

This story was originally published on 6:19 p.m. EDT on March 19, 2018.

Correction: A previous version of this story misidentified the time of the 2018 vernal equinox by 10 minutes. It's 12:15 p.m. EDT, not 12:25 p.m. EDT.

SEE ALSO: 17 'facts' about space and Earth that you thought were true — but have been debunked by science

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