The most astounding fact about the universe

Back in 2008, Time Magazine interviewed Neil de Grasse Tyson, and asked him, “What is the most astounding fact you can share with us about the Universe?” His answer was indeed a very good, true, and astounding fact about the Universe: that all the complex atoms that make up everything we know owe their origins to ancient, exploded stars, dating back billions of years. It’s a great fact, and it’s definitely on the short list of the most remarkable things we’ve learned about the Universe.

But if I were to choose the single most astounding fact about the Universe, I’d want you to consider something else: something far more fundamental and profound. Consider that the Universe — with everything in it the way it is — didn’t have to be this way. It didn’t have to even be close.

We could have had a Universe without trees, without mountains, without our skies and without oceans. We could have had a Universe without planets like Earth, or planets at all. We could have even had a Universe where nothing that we know of — no particles, forces or interactions — exists as it does right now.

Yet despite the endless possibilities for what could have been, this is the Universe we have. Our Universe exists the way it is, with all the particles, forces, interactions, structures, and the unique history of how it all came to be. The way it all turned out, no doubt, is absolutely wondrous. Just here, in our own little corner of the Universe, we find ourselves in a forgotten, nondescript little group of galaxies no more or less special than any of the billions out there.

But while our planet, our galaxy and our place in the Universe might not be special or privileged in any fundamental way, the Universe itself, compared to all the ways it could have been, is something very special. It manifests itself on every scale we can conceive of looking at. We can look all the way down to the smallest scales, to the internal structure of matter, down to molecules, atoms, and the most fundamental subatomic particles ever discovered.

Image credit: E. Siegel, from his new book, Beyond The Galaxy.

We can look out, not just to the stars and galaxies, but all the way across the Universe, to quasars, intergalactic clouds of gas, even back to the cosmic microwave background and the very first neutral atoms our Universe had ever seen. We can look at all of that, and everything in between.

And yet, for absolutely everything we look at, there is one fact that stands out as the most astounding. The entire Universe,

• on all scales,
• in all places,
• and at all times,

obeys the same fundamental laws of nature.

From the weakest, lowest-frequency photon of light to the largest galaxy ever assembled, from the unstable atoms of Uranium decaying in the Earth’s core to the neutral hydrogen atoms forming for the first time 46 billion light years away, the laws that everything in this Universe obeys are the same.
Gravitation, electromagnetism, and the strong and weak nuclear forces are the same wherever and whenever you go. The particles that exist (and can exist) and their properties are the same. The rules that govern the entire system are the same. All of it, at all energies, at all times, at all places, are underwritten by the same laws of nature.

Image credit: NASA, ESA, the ACS Science Team and N. Benitez et al.

This is the most remarkable thing of all. Imagine what things would be like if this weren’t true. Imagine an existence where nature behaves randomly and unpredictably, where gravity turns on-and-off on a whim, where the Sun could simply stop burning its fuel for no apparent reason, where the atoms that form you could spontaneously cease to hold together.
A Universe like this would truly be frightening, because it could never be understood. The things you learn here and now might not be true later, or even five feet away. But the Universe isn’t like this at all.

Image credit: U.S. DOE, NSF, CPEP and LBNL, retrieved from http://physics.gla.ac.uk/.

The Universe is a place where the forms that the matter and energy occupying it can change, where the spacetime itself that we all exist in can change, but the fundamental laws — that everything is subject to — are constant.
Because what that means is that we can observe the Universe, experiment with the Universe, assemble and disassemble the things we find in it, and learn about the Universe itself.

Only if the fundamental laws of the Universe are the same everywhere and at all times can we learn what they actually are today. Only if those laws are applicable everywhere and at all times can we use that knowledge to figure out what the Universe — and everything in it — was doing in the past, and what it will be doing in the future.
In other words, it is this one fact, this most astounding fact, that allows us to do science, and to learn something meaningful, at all. It’s why any form of science even exists, and why it’s actually a useful tool for learning about this Universe. When you put it all together, it means the most astounding fact about the Universe is this: that it exists in such a way that it can be understood at all.

This post first appeared at Forbes and then at 3tags.org

Source: 3tags.org

What does our universe look like on a large scale?

Multiple studies have found that galaxies make up an astonishingly low portion of the volume of our universe, and that the vast majority of the universe consists of massive voids of dark matter and dark energy. Now, a new simulation has seemingly confirmed this conception of the universe, and as a bonus, has discovered that the “missing matter” of the nearby universe may be hiding within these voids.

Over the last five years or so, simulations of the universe that take into account all known aspects of cosmology–the expansion of the universe, the gravitational pull of matter, the motion of cosmic gas, the formation of stars, planets, galaxies, etc–have revealed that the universe resembles a gigantic spiderweb, in which galaxies compose the filaments that are thinly stretched around huge, dark, empty voids. As a result, galaxies make up approximately 50% of the universe’s total mass, but only .2% of the total volume.

Now, a new study by a team from the Institute of Astro- and Particle Physics at the University of Innsbruck, with the help of Illustris, which claims to be the “most ambitious computer simulation of our Universe yet performed,” claims that their simulation confirms the theory of the “cosmic web.” The large-scale simulation modeled physical processes starting with the initial conditions of the young universe (300,000 years after the Big Bang) all the way to the present, spanning over 13.8 billion years of cosmic evolution. The simulation created tens of thousands of galaxy in high detail, many of which align with real galaxies we have observed in the universe thus far.
In the simulation, the universe is represented as a giant cube consisting of intricate webs of thin galaxy filaments, which spans 350 light years on each side and is 12 million years old.

The simulation may have also provided an answer to the long-running “missing matter” mystery. Observations of our cosmic microwave background demonstrate that approximately one-sixth of the total matter in the universe is “ordinary” matter, while the rest is dark matter. We have a rough estimate of the total mass of our universe based on the movement of distant objects in relation to the Sun, but the observable stars, planets, and other ordinary matter objects only account for approximately 50% of that calculated mass. Some of that “missing matter” has been found in the filamentary structures that surround galaxies and provide scaffolding for the “cosmic web,” but there’s still a significant amount of matter than is unaccounted for. According to this study, a large portion of that matter may be hiding in those massive voids between galaxies.

“As much as 30% of the Universe’s observable matter could be hiding in enormous cosmic voids, where it is too sparse for scientists to observe,” the researchers wrote in their paper, published today in Nature.

The simulation showed that the culprit for the missing matter may be supermassive black holes. When matter falls into black holes, it is converted into energy, which is transferred to the surrounding gas. This leads to a violent emission of matter from supermassive black holes that send the matter thousands of light years past our galaxy, where it likely languishes within these huge empty spaces.

“[This] simulation, one of the most sophisticated ever run, suggests that the black holes at the centre of every galaxy are helping to send matter into the loneliest places in the universe,” said team leader Dr. Markus Haider.

Source: 3tags.org

Can two galaxies move away from each other faster than the speed of light? 

The short, and possibly surprising, answer to this question is yes.

The Hubble constant is the measure of how fast the Universe is expanding today and its value has been measured to be 70 km/s per Megaparsec (a parsec is just a unit of distance equal to about 3.26 light-years, and a Megaparsec is a million parsecs). This means that on average, for every Megaparsec two galaxies are separated by, they are moving away from each other by 70 km/s. Therefore, to be moving away from each other at the speed of light, two galaxies would need to be separated by a distance of about 4,300 billion parsecs. This is smaller than the radius of the observable Universe, therefore not only are there galaxies in the Universe that are moving away from us faster than light, but we can still see them!

This raises two additional questions:

1. If another galaxy is moving away from us faster than light, how can we still see it?
2. Isn't it a violation of the theory of relativity to have two things moving apart faster than the speed of light?

The answer to the first of these questions is that the light the distant galaxy is emitting today will never reach us, so we will never know what it looks like today. This is because today it is moving away from us faster than light, so the light it emits doesn't travel fast enough to ever reach us. However, the light that it emitted billions of years ago, when the Universe was smaller (remember it has been expanding all along) and when that galaxy wasn't receding from the Milky Way as fast, is what we are seeing today. In other words, we are seeing that galaxy as it was billions of years ago.
The second question is an interesting one that confuses many people. The theory of relativity does indeed state that nothing can travel faster than light, however this refers to motion in the traditional sense, meaning you can't launch a spaceship and travel through space faster than light. The two galaxies we've been discussing are not travelling through space, it is the space between them that is expanding. Or put in another way, they are stationary and all the space around them is being stretched out. This is why it doesn't violate the theory of relativity, because it is not motion in the traditional sense.

Source:curious.astro.cornell.edu

3 Earth-sized planets found orbiting a near ultra-cool dwarf star

Three Earth-sized planets are thought to have surface temperatures which would allow liquid water, making them potentially hospitable to life.

Three distant worlds that orbit a feeble star in the constellation of Aquarius are the most likely places discovered so far to find life beyond the solar system, astronomers say.

The earth sized planets are all thought to have regions where surface temperatures fall within the Goldilocks zone and are neither too hot nor too cold for water to run freely, making them at least potentially hospitable to life.

Belgian astronomers found the planets using the Transiting Planets and Planetesimals Small Telescope (Trappist) at the La Silla Observatory in Chile’s Atacama desert. The planets revealed themselves through the periodic dimming that occurred as they passed in front of their parent star, an ultracool dwarf that lies only 40 light years away.
Known formally as 2MASS J23062928-0502285, but helpfully dubbed Trappist-1, the star is not much larger than Jupiter and emits a fraction of the sun’s radiation. The star is too faint to see in the night sky with the naked eye, or even through a large amateur telescope.
Observations from the Trappist telescope taken from September to December last year, and follow-up measurements from larger instruments, revealed three small planets orbiting very close to the star, at 1%, 1.5% and about 3% of the distance that Earth lies from the sun. A year on the innermost planet passes in only 1.5 Earth days, and in 2.4 Earth days on the second. The orbit of the third planet is less certain, with a year passing in 4.5 to 73 Earth days, according to a report in the journal Nature.
“Because the star is so faint, all of these planets have temperatures that are similar to those on Earth. They could have liquid water on the surfaces, and on Earth life is critically dependent on water. We don’t know, but maybe there could be life there,” said Michaël Gillon who led the research at the University of Liege.
The planets are thought to be tidally-locked to their star, meaning one half is in permanent daytime, and the other in constant darkness. If the planets have atmospheres, the alien air would even out the temperature difference across the hemispheres. At the hottest spots, the temperature would reach about 100 Celsius on the innermost planet, 70 Celsius on the second, and perhaps 30Celsius on the outermost world.
“These are the first temperate Earth-sized planets found outside the solar system, and the first we can study in detail,” said Gillon. “That makes them extremely promising targets for us.” The composition of the planets is not yet known, but the sizes mean they must be solid. “They could be iron-rich like Mercury, or mostly silicate rocks, or extremely icy, like the moons of Jupiter,” said Gillon.
Plans have already been drawn up to study the planets in greater detail. With the Hubble space telescope, the astronomers hope to learn whether the worlds have their own atmospheres. But future instruments will be needed to find out much more about the planets. If they do have atmospheres, then analysing the molecular constituents for water, carbon dioxide and ozone could reveal evidence for life.

Those measurements will be possible from two forthcoming observatories, the European Extremely Large Telescope, which is under construction in the Atacama desert, and the James Webb Space Telescope, Nasa’s new infrared observatory, which is due to launch in 2018. Once they are in operation, astronomers can begin the search for biological activity on the planets. “That’s a giant step in the search for life in the universe,” said Julien de Wit, a co-author on the study at MIT.

Source:theguardian

The biggest question about the beginning of the universe

Our Universe is expanding, getting less dense and cooling today, teaching us that it was hotter and denser in the distant past. If we extrapolate backwards in time, we can reach epochs where:

• gravitation hadn’t yet had time to collapse matter into clusters, galaxies or even stars,
• the temperature of the Universe was too hot to form neutral atoms, ionizing them immediately,
• particles were so energetic that even atomic nuclei were unstable, being immediately split apart into individual protons and neutrons,
• and even to where the energy density was so high that matter/antimatter pairs were spontaneously created from pure energy.

You might think we could go all the way back even farther, to the very birth of space and time themselves. That was, in fact, the original idea of the Big Bang, but thanks to some spectacular observations, we know that isn’t quite how our Universe began.

Above is the earliest known “baby picture” of our Universe. When the Universe finally did cool enough to stably form neutral atoms, all the radiation from the earliest times could suddenly travel through space, in a straight line, without being absorbed, re-emitted or scattered off of a free, charged particle. This radiation then had its wavelength stretched by the expansion of the Universe, where it can now be found at microwave frequencies: the Cosmic Microwave Background (CMB), or the leftover glow from the Big Bang. When we look at the fluctuations in it — or the slight imperfections from a perfectly uniform temperature at various locations across the sky — we can use what we know about physics and astrophysics to teach us a number of very important things.

One of the things we can learn is that our Universe is made up of about 5% normal (atomic) matter, 27% dark matter and 68% dark energy. But no less important is this: we learn that these imperfections were initially the same on all scales, and are of such a small magnitude that the Universe couldn’t have achieved an arbitrarily high temperature in the distant past. Instead, there must have been a phase before the Universe was hot, dense and matter-and-radiation filled that set it all up. Originally conceived by Alan Guth in 1979, this phase — known today as cosmic inflation — solves a number of major problems with the Universe: stretching it flat, giving it the same temperature everywhere, eliminating high-energy relics and defects (like magnetic monopoles) from the Universe, and providing a mechanism to generate those much-needed fluctuations.

The fluctuations are remarkable in particular, because two distinct types of them — density (scalar) fluctuations and gravitational wave (tensor) fluctuations — were both predicted by inflation before the evidence for either one existed. As of today, we’ve not only directly observed the scalar ones and have strict limits on the tensor ones, but we’ve measured what the spectrum of these initial fluctuations were, which tells us something about the various types of inflation that could have occurred. In general, you can visualize inflation as a ball rolling down any type of hill you can imagine, into a valley.

In order to have enough inflation to reproduce the Universe that we see, we need for the ball to roll slowly enough down that hill so that the Universe can be stretched flat, made the same temperature everywhere and to have those quantum fluctuations (that create the density fluctuations) get stretched across the Universe. In order to determine which model of inflation is the one our Universe has — in other words, what the shape of that “hill” actually looks like — there are two things that help us out:

1. The fluctuations can be more important on small scales or on large ones, and by measuring the full spectrum of them, we can know what the slope of that hill was when inflation came to an end.
2. If we can measure the gravitational wave fluctuations and compare them to the density fluctuations, we can reconstruct how the slope was changing when inflation ended.

In other words, we can “cook up” any model for inflation that we like, but only some of them will give us the right values — that match our Universe — for these two different types of fluctuations.

Thanks to the Planck spacecraft, we now have very tight restrictions on the density fluctuations, disfavoring many of the simplest models. As superior (polarization) data from projects like Planck, BICEP, POLARBEAR and others continues to come in, hope that we’ll either detect the gravitational wave signatures or set stronger limits than ever before rises even higher. People have argued for a long time that cosmic inflation has too many solutions, but the better we get at making these measurements, the more hope we have that the number of solutions will eventually be reduced to one unique one.
The Universe has a great story to tell us about its origin, to the limits of what we can conceivably measure. The better we get at actually making those measurements, the better we can understand how it all got its start. Cosmic inflation is almost definitely the answer to what happened before the Big Bang. But what was cosmic inflation like? We’re closer than ever to actually coming up with the answer.

Sources:3tags.org; startswithabang

Image credits: NASA; E. Siegel

Drake's Equation used to find out "Are we alone in the universe?"

In 1961, astrophysicist Frank Drake developed an equation to estimate the number of advanced civilizations likely to exist in the Milky Way galaxy. The Drake equation (top row) has proven to be a durable framework for research, and space technology has advanced scientists’ knowledge of several variables. But it is impossible to do anything more than guess at variables such as L, the probably longevity of other advanced civilizations. In new research, Adam Frank and Woodruff Sullivan offer a new equation (bottom row) to address a slightly different question: What is the number of advanced civilizations likely to have developed over the history of the observable universe? Frank and Sullivan’s equation draws on Drake’s, but eliminates the need for L. CREDIT University of Rochester

Are humans unique and alone in the vast universe? This question– summed up in the famous Drake equation — has for a half-century been one of the most intractable and uncertain in science.
But a new paper shows that the recent discoveries of exoplanets combined with a broader approach to the question makes it possible to assign a new empirically valid probability to whether any other advanced technological civilizations have ever existed.
And it shows that unless the odds of advanced life evolving on a habitable planet are astonishingly low, then human kind is not the universe’s first technological, or advanced, civilization.
The paper, to be published in Astrobiology, also shows for the first time just what “pessimism” or “optimism” mean when it comes to estimating the likelihood of advanced extraterrestrial life.
“The question of whether advanced civilizations exist elsewhere in the universe has always been vexed with three large uncertainties in the Drake equation,” said Adam Frank, professor of physics and astronomy at the University of Rochester and co-author of the paper. “We’ve known for a long time approximately how many stars exist. We didn’t know how many of those stars had planets that could potentially harbour life, how often life might evolve and lead to intelligent beings, and how long any civilizations might last before becoming extinct.”
“Thanks to NASA’s Kepler satellite and other searches, we now know that roughly one-fifth of stars have planets in “habitable zones,” where temperatures could support life as we know it. So one of the three big uncertainties has now been constrained.”
Frank said that the third big question–how long civilizations might survive–is still completely unknown. “The fact that humans have had rudimentary technology for roughly ten thousand years doesn’t really tell us if other societies would last that long or perhaps much longer,” he explained.
But Frank and his co-author, Woodruff Sullivan of the astronomy department and astrobiology program at the University of Washington, found they could eliminate that term altogether by simply expanding the question.
“Rather than asking how many civilizations may exist now, we ask ‘Are we the only technological species that has ever arisen?” said Sullivan. “This shifted focus eliminates the uncertainty of the civilization lifetime question and allows us to address what we call the ‘cosmic archaeological question’–how often in the history of the universe has life evolved to an advanced state?”
That still leaves huge uncertainties in calculating the probability for advanced life to evolve on habitable planets. It’s here that Frank and Sullivan flip the question around. Rather than guessing at the odds of advanced life developing, they calculate the odds against it occurring in order for humanity to be the only advanced civilization in the entire history of the observable universe. With that, Frank and Sullivan then calculated the line between a Universe where humanity has been the sole experiment in civilization and one where others have come before us.
“Of course, we have no idea how likely it is that an intelligent technological species will evolve on a given habitable planet,” says Frank. But using our method we can tell exactly how low that probability would have to be for us to be the ONLY civilization the Universe has produced. We call that the pessimism line. If the actual probability is greater than the pessimism line, then a technological species and civilization has likely happened before.”
Using this approach, Frank and Sullivan calculate how unlikely advanced life must be if there has never been another example among the universe’s ten billion trillion stars, or even among our own Milky Way galaxy’s hundred billion.
The result? By applying the new exoplanet data to the universe’s 2 x 10 to the 22nd power stars, Frank and Sullivan find that human civilization is likely to be unique in the cosmos only if the odds of a civilization developing on a habitable planet are less than about one in 10 billion trillion, or one part in 10 to the 22th power.
“One in 10 billion trillion is incredibly small,” says Frank. “To me, this implies that other intelligent, technology producing species very likely have evolved before us. Think of it this way. Before our result you’d be considered a pessimist if you imagined the probability of evolving a civilization on a habitable planet were, say, one in a trillion. But even that guess, one chance in a trillion, implies that what has happened here on Earth with humanity has in fact happened about a 10 billion other times over cosmic history!”
For smaller volumes the numbers are less extreme. For example, another technological species likely has evolved on a habitable planet in our own Milky Way galaxy if the odds against it are better than one chance in 60 billion.
But if those numbers seem to give ammunition to the “optimists” about the existence of alien civilizations, Sullivan points out that the full Drake equation–which calculates the odds that other civilizations are around today — may give solace to the pessimists.
“The universe is more than 13 billion years old,” said Sullivan. “That means that even if there have been a thousand civilizations in our own galaxy, if they live only as long as we have been around — roughly ten thousand years — then all of them are likely already extinct. And others won’t evolve until we are long gone. For us to have much chance of success in finding another “contemporary” active technological civilization, on average they must last much longer than our present lifetime.”
“Given the vast distances between stars and the fixed speed of light we might never really be able to have a conversation with another civilization anyway,” said Frank. “If they were 20,000 light years away then every exchange would take 40,000 years to go back and forth.”
But, as Frank and Sullivan point out, even if there aren’t other civilizations in our galaxy to communicate with now, the new result still has a profound scientific and philosophical importance. “From a fundamental perspective the question is ‘has it ever happened anywhere before?'” said Frank. Our result is the first time anyone has been able to set any empirical answer for that question and it is astonishingly likely that we are not the only time and place that an advance civilization has evolved.”
According to Frank and Sullivan their result has a practical application as well. As humanity faces its crisis in sustainability and climate change we can wonder if other civilization-building species on other planets have gone through a similar bottleneck and made it to the other side. As Frank puts it “We don’t even know if it’s possible to have a high-tech civilization that lasts more than a few centuries.” With Frank and Sullivan’s new result, scientists can begin using everything they know about planets and climate to begin modelling the interactions of an energy-intensive species with their home world knowing that a large sample of such cases has already existed in the cosmos. “Our results imply that our evolution has not been unique and has probably happened many times before. The other cases are likely to include many energy intensive civilizations dealing with their feedbacks onto their planets as their civilizations grow. That means we can begin exploring the problem using simulations to get a sense of what leads to long lived civilizations and what doesn’t.”
Frank and Sullivan’s argument hinges upon the recent discovery of how many planets exist and how many of those lie in what scientists call the “habitable zone” — planets in which liquid water, and therefore life, could exist. This allows Frank and Sullivan to define a number they call N_ast. Nast is the product of N*, the total number of stars; f_p, the fraction of those stars that form planets; and n_p, the average number of those planets in the habitable zones of their stars.
They then set out what they call the “Archaelogical-form” of the Drake equation, which defines A as the “number of technological species that have ever formed over the history of the observable Universe.”
Their equation, A=Nast*f_bt, describes A as the product of Nast – the number of habitable planets in a given volume of the Universe – multiplied by fbt – the likelihood of a technological species arising on one of these planets. The volume considered could be, for example, the entire Universe, or just our Galaxy.

source:wattsupwiththat.com

Seven greatest mysteries of the universe

We've made some incredible space discoveries in the last few years, like gravitational waves and liquid water on Mars.
But considering we've explored only a teeny-tiny corner of the universe, there's a lot of big questions we don't have answers for yet.
Here are some of the biggest unsolved mysteries about space.

1. What we can see makes up only 5% of the universe

Everything we can see makes up a piddling 5% of the universe. The other 95% is part dark energy and part dark matter.

If we can't actually see dark matter or dark energy, how do we know they're real? The bottom line is, we don't. Scientists think dark energy is the mysterious force that's causing the universe's rate of expansion to continue accelerating. However, dark energy could also be explained as just a big error in theory of gravity.

Dark matter is an invisible material that makes up the bulk of the matter in galaxies. Scientists think it exists because the gravitational force of galaxies is far too large to be explained by only the matter we can see. 

2. What is up with Mars?

Life may have once existed there, and it might even still exist there.
Mars used to hold vast oceans, and now there's evidence that liquid water still periodically flows on its surface.
Did this planet once hold life? And more importantly, does it hold life still? Scientists are pushing to send human explorers to Mars to find out.

3. Where do high-energy cosmic rays come from?

They are constantly crashing into Earth from outer space, but no one knows their origin.

Cosmic rays are streams of high-speed particles that fly through space and sometimes barrel into Earth. Where do they come from?

"The lowest energy cosmic rays arrive from the Sun in a stream of charged particles known as the solar wind, but pinning down the origin of the higher-energy particles is made difficult as they twist and turn in the magnetic fields of interstellar space," CERN explains.

4. What's the deal with "fast radio bursts"?

Sometimes, if an astronomer gets lucky, she can spot millisecond-long flashes of radio waves from space called "fast radio bursts" (FRBs). But just like with cosmic rays, astronomers don't know where FRBs come from.
Two recent papers have muddied the waters even more because they came to opposite conclusions about the origin of FRBs. One suggests FRBs come from the same source; the other says FRBs come from cataclysmic disasters that can't possibly repeat themselves.
The bottom line is we really don't know what causes them, and we need a better way to detect them if we want to find out.

5. Why is there more matter than antimatter?

We know that when a particle of matter and a particle of antimatter collide, they annihilate each other.
If there were an equal amount of matter and antimatter, our universe would be completely devoid of particles.
Based on what we know about cosmology, the Big Bang should have produced an equal amount of matter and antimatter. That means we would have been left with a particle-less universe. But for some reason, the Big Bang produced slightly more matter than antimatter. Something tipped the balance in matter's favor, but we have no idea what.
"One of the greatest challenges in physics is to figure out what happened to the antimatter, or why we see matter/antimatter asymmetry," CERN explains.

6. How did life on Earth get started?

It's one of the most fundamental questions of all time, and yet we don't have a scientific answer for it.
Some scientists think it was carried here on comets or asteroids. It's a good theory because we've found organic material on some them. Some even think that a piece of Mars could have landed on Earth and allowed life to get started.
Others think simple molecules caused chemical reactions to happen that eventually formed more complex molecules. Those molecules combined into things like RNA, one of the necessary ingredients for life. Then multicellular organisms evolved.

7. How will the universe end?

Astronomers estimate that in about 6 billion years, Earth will get vaporized by our dying sun. But what about the rest of the universe? 

There are a few grisly theories out there. Thermodynamics tells us that a heat death is possible, where everything in the universe becomes the same temperature. That means all the stars will fizzle out and all matter will decay. 

There's also the idea that the opposite of the Big Bang will happen. It's called the Big Crunch. If the universe keeps expanding and growing, eventually there will be too much gravity and all that gravitational force will cause everything to start contracting. 

The whole universe will shrink down into a dense, fiery inferno and we'll all get fried — putting an end to these mysteries altogether.

source: BusinessInsider