Posts Tagged ‘time’

by Steve Nadis

In January 1916, Karl Schwarzschild, a German physicist who was stationed as a soldier on the eastern front, produced the first exact solution to the equations of general relativity, Albert Einstein’s radical, two-month-old theory of gravity. General relativity portrayed gravity not as an attractive force, as it had long been understood, but rather as the effect of curved space and time. Schwarzschild’s solution revealed the curvature of space-time around a stationary ball of matter.

Curiously, Schwarzschild noticed that if this matter were confined within a small enough radius, there would be a point of infinite curvature and density — a “singularity” — at the center.

Infinities cropping up in physics are usually cause for alarm, and neither Einstein, upon learning of the soldier’s result, nor Schwarzschild himself believed that such objects really exist. But starting in the 1970s, evidence mounted that the universe contains droves of these entities — dubbed “black holes” because their gravity is so strong that nothing going into them, not even light, can come out. The nature of the singularities inside black holes has been a mystery ever since.

Recently, a team of researchers affiliated with Harvard University’s Black Hole Initiative (BHI) made significant progress on this puzzle. Paul Chesler, Ramesh Narayan and Erik Curiel probed the interiors of theoretical black holes that resemble those studied by astronomers, seeking to determine what kind of singularity is found inside. A singularity is not a place where quantities really become infinite, but “a place where general relativity breaks down,” Chesler explained. At such a point, general relativity is thought to give way to a more exact, as yet unknown, quantum-scale description of gravity. But there are three different ways in which Einstein’s theory can go haywire, leading to three different kinds of possible singularities. “Knowing when and where general relativity breaks down is useful in knowing what theory [of quantum gravity] lies beyond it,” Chesler said.

The BHI group built on a major advance achieved in 1963, when the mathematician Roy Kerr solved Einstein’s equations for a spinning black hole — a more realistic situation than the one Schwarzschild took on since practically everything in the universe rotates. This problem was harder than Schwarzschild’s, because rotating objects have bulges in the center and therefore lack spherical symmetry. Kerr’s solution unambiguously described the region outside a spinning black hole, but not its interior.

Kerr’s black hole was still somewhat unrealistic, as it occupied a space devoid of matter. This, the BHI researchers realized, had the effect of making the solution unstable; the addition of even a single particle could drastically change the black hole’s interior space-time geometry. In an attempt to make their model more realistic and more stable, they sprinkled matter of a special kind called an “elementary scalar field” in and around their theoretical black hole. And whereas the original Kerr solution concerned an “eternal” black hole that has always been there, the black holes in their analysis formed from gravitational collapse, like the ones that abound in the cosmos.

First, Chesler, Narayan and Curiel tested their methodology on a charged, non-spinning, spherical black hole formed from the gravitational collapse of matter in an elementary scalar field. They detailed their findings in a paper posted on the scientific preprint site arxiv.org in February. Next, Chesler tackled the more complicated equations pertaining to a similarly formed rotating black hole, reporting his solo results three months later.

Their analyses showed that both types of black holes contain two distinct kinds of singularities. A black hole is encased within a sphere called an event horizon: Once matter or light crosses this invisible boundary and enters the black hole, it cannot escape. Inside the event horizon, charged stationary and rotating black holes are known to have a second spherical surface of no return, called the inner horizon. Chesler and his colleagues found that for the black holes they studied, a “null” singularity inevitably forms at the inner horizon, a finding consistent with prior results. Matter and radiation can pass through this kind of singularity for most of the black hole’s lifetime, Chesler explained, but as time goes on the space-time curvature grows exponentially, “becoming infinite at infinitely late times.”

The physicists most wanted to find out whether their quasi-realistic black holes have a central singularity — a fact that had only been established for certain for simple Schwarzschild black holes. And if there is a central singularity, they wanted to determine whether it is “spacelike” or “timelike.” These terms derive from the fact that once a particle approaches a spacelike singularity, it is not possible to evolve the equations of general relativity forward in time; evolution is only allowed along the space direction. Conversely, a particle approaching a timelike singularity will not inexorably be drawn inside; it still has a possible future and can therefore move forward in time, although its position in space is fixed. Outside observers cannot see spacelike singularities because light waves always move into them and never come out. Light waves can come out of timelike singularities, however, making them visible to outsiders.

Of these two types, a spacelike singularity may be preferable to physicists because general relativity only breaks down at the point of singularity itself. For a timelike singularity, the theory falters everywhere around that point. A physicist has no way of predicting, for instance, whether radiation will emerge from a timelike singularity and what its intensity or amplitude might be.

The group found that for both types of black holes they examined, there is indeed a central singularity, and it is always spacelike. That was assumed to be the case by many, if not most, astrophysicists who held an opinion, Chesler noted, “but it was not known for certain.”

The physicist Amos Ori, a black hole expert at the Technion in Haifa, Israel, said of Chesler’s new paper, “To the best of my knowledge, this is the first time that such a direct derivation has been given for the occurrence of a spacelike singularity inside spinning black holes.”

Gaurav Khanna, a physicist at the University of Massachusetts, Dartmouth, who also investigates black hole singularities, called the BHI team’s studies “great progress — a quantum leap beyond previous efforts in this area.”

While Chesler and his collaborators have strengthened the case that astrophysical black holes have spacelike singularities at their cores, they haven’t proved it yet. Their next step is to make more realistic calculations that go beyond elementary scalar fields and incorporate messier forms of matter and radiation.

Chesler stressed that the singularities that appear in black hole calculations should disappear when physicists craft a quantum theory of gravity that can handle the extreme conditions found at those points. According to Chesler, the act of pushing Einstein’s theory to its limits and seeing exactly how it fails “can guide you in constructing the next theory.”

https://www.quantamagazine.org/black-hole-singularities-are-as-inescapable-as-expected-20191202/?utm_source=Nature+Briefing&utm_campaign=6cddda34dd-briefing-dy-20191206&utm_medium=email&utm_term=0_c9dfd39373-6cddda34dd-44039353

by Morgan McFall-Johnsen

The NASA scientist Jessie Christiansen made a video that traces our solar system’s movement through the Milky Way as dinosaurs emerged, went extinct, and were replaced by mammals on Earth.

Our sun orbits the galaxy’s center, so many dinosaurs roamed the Earth while the planet was on the other side of the Milky Way.

Our solar system’s orbit keeps us just the right distance from the galaxy’s chaotic center for life to exist.

When dinosaurs ruled the Earth, the planet was on a completely different side of the galaxy.

A new animation by the NASA scientist Jessie Christiansen shows just how long the dinosaurs’ reign lasted — and how short the era of humans has been in comparison — by tracing our solar system’s movement through the Milky Way.

Our sun orbits the galaxy’s center, completing its rotation every 250 million years or so. So Christiansen’s animation shows that the last time our solar system was at its current point in the galaxy, the Triassic period was in full swing and dinosaurs were just emerging. Many of the most iconic dinosaurs roamed the Earth when the planet was in a very different part of the Milky Way.

Christiansen got the idea to illustrate this history when she was leading a stargazing party at the California Institute of Technology in Pasadena. Attendees were astonished when she mentioned that our solar system was across the galaxy when dinosaurs roamed.

“That was the first time I realized that those time scales — archaeological, fossil-record time scales and astronomical time scales — actually kind of match along together,” Christiansen told Business Insider. “Then I had this idea that I could map out dinosaur evolution through the galaxy’s rotation.”

Christiansen said it took her about four hours to make the film using timed animations in PowerPoint. She also noted a couple of minor corrections to the text in her video: Plesiosaurs are not dinosaurs, and we complete a galactic orbit every 250 million years, not 200 million years.

‘A spiral through space’

But galactic movement is more complicated than the video shows. The other stars and planetary systems in the galaxy are also moving, at different speeds and in different orbits. The inner portions spin faster than the outer regions.

What’s more, the galaxy itself is moving through space, slowly approaching the nearby Andromeda galaxy.

“The animation kind of makes it seem like we’ve come back to the same spot, but in reality the whole galaxy has moved a very long way,” Christiansen said. “It’s more like we’re doing a spiral through space. As the whole galaxy’s moving and we’re rotating around the center, it kind of creates this spiral.”

So in the solar system’s rotation around the galactic center, we’re not returning to a fixed point. The neighborhood is different from the last time we were here.

Earth, however, is not drastically different; it still supports complex life. That’s partially thanks to the path of our sun’s galactic orbit.

“Our solar system doesn’t travel to the center of the galaxy and then back again,” Christiansen said. “We always stay about this distance away.”

In other words, even as our solar system travels through the Milky Way, it doesn’t approach the inhospitable center, where life probably wouldn’t survive.

“There’s a lot of stars, it’s dynamically unstable, there’s a lot of radiation,” Christiansen said. “Our solar system certainly doesn’t pass through that.”

That’s a huge part of why dinosaurs, mammals, or any other form of life can exist on Earth.

https://www.businessinsider.com/video-nasa-scientist-dinosaurs-milky-way-2019-10

For about a century now, scientists have theorized that the metals in our Universe are the result of stellar nucleosynthesis. This theory states that after the first stars formed, heat and pressure in their interiors led to the creation of heavier elements like silicon and iron. These elements not only enriched future generations of stars (“metallicity”), but also provided the material from which the planets formed.

More recent work has suggested that some of the heaviest elements could actually be the result of binary stars merging. In fact, a recent study by two astrophysicists found that a collision which took place between two neutron stars billions of years ago produced a considerable amount of some of Earth’s heaviest elements. These include gold, platinum and uranium, which then became part of the material from which Earth formed.

The research was conducted by Prof. Szabolcs Márka from Columbia University and Prof. Imre Bartos of the University of Florida. Their findings were published in a study titled “Nearby Neutron-Star Mergers Explain Actinide Abundance in the Early Solar System”, which recently appeared in the May issue of the scientific journal Nature.


An artist’s conception of two neutron stars, moments before they collide. Credit: NASA

According to the scientific consensus, asteroids and comets are composed of material left over from the formation of the Solar System. When bits of these come to Earth in the form of meteorites, they carry traces of radioactive isotopes whose decay is used to determine when the asteroids were created. The study of these space rocks can also shed light on what materials existed in our Solar System billions of years ago.

For the sake of their study, Bartos and Márka ran numerical simulations of the Milky Way and compared the results to the composition of meteorites that were retrieved on Earth. What they found was that a single neutron-star collision could have occurred within our cosmic neighborhood – ~1,000 light years from our Solar System – roughly 4.65 billion years ago.

At the time, our Solar System was still a massive cloud of dust and gas that would soon undergo gravitational collapse at its center, thus giving birth to our Sun. Roughly 100 million years later, the Earth and other Solar Planets would form from the proto-planetary debris disk that fell into orbit around our young Sun.

This single cosmic event, they estimate, gave birth to elements that would become part of this disk – and which now make up roughly 0.3% of the Earth’s heaviest elements. Most of these are in the form on iodine, an element which is essential to biological processes. In this respect, this event may have played a role in the emergence of life here in the Solar System as well.

To put this event in perspective, consider that the Milky Way galaxy is an estimated 100,000 light years in diameter. This collision and the resulting explosion, therefore, took place roughly 1/100th the distance away. In fact, the research team indicated that if a similar event happened at the same distance today, the resulting radiation would outshine every star in the sky.

What is especially interesting about this study is the way it provides insight into an event that was both unique and highly consequential in the history and formation of Earth and our Solar System. “It sheds bright light on the processes involved in the origin and composition of our Solar System, and will initiate a new type of quest within disciplines, such as chemistry, biology and geology, to solve the cosmic puzzle,” Bartos summarized.

And as Márka indicated, it also addresses some of the deeper questions scientists have about the origins of life as we know it:

“Our results address a fundamental quest of humanity: Where did we come from and where are we going? It is very difficult to describe the tremendous emotions we felt when we realized what we had found and what it means for the future as we search for an explanation of our place in the universe.”

It also reaffirms what Carl Sagan famously said: “We are a way for the universe to know itself. Some part of our being knows this is where we came from. We long to return. And we can, because the cosmos is also within us… The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff.”

https://www.universetoday.com/142157/the-earths-gold-came-from-two-neutron-stars-that-collided-billions-of-years-ago-1/

By Stephanie Pappas

The Big Bang is commonly thought of as the start of it all: About 13.8 billion years ago, the observable universe went boom and expanded into being.

But what were things like before the Big Bang?

Short answer: We don’t know. Long answer: It could have been a lot of things, each mind-bending in its own way.

The first thing to understand is what the Big Bang actually was.

“The Big Bang is a moment in time, not a point in space,” said Sean Carroll, a theoretical physicist at the California Institute of Technology and author of “The Big Picture: On the Origins of Life, Meaning and the Universe Itself” (Dutton, 2016).

So, scrap the image of a tiny speck of dense matter suddenly exploding outward into a void. For one thing, the universe at the Big Bang may not have been particularly small, Carroll said. Sure, everything in the observable universe today — a sphere with a diameter of about 93 billion light-years containing at least 2 trillion galaxies — was crammed into a space less than a centimeter across. But there could be plenty outside of the observable universe that Earthlings can’t see because it’s physically impossible for the light to have traveled that far in 13.8 billion years.
Thus, it’s possible that the universe at the Big Bang was teeny-tiny or infinitely large, Carroll said, because there’s no way to look back in time at the stuff we can’t even see today. All we really know is that it was very, very dense and that it very quickly got less dense.

As a corollary, there really isn’t anything outside the universe, because the universe is, by definition, everything. So, at the Big Bang, everything was denser and hotter than it is now, but there was no more an “outside” of it than there is today. As tempting as it is to take a godlike view and imagine you could stand in a void and look at the scrunched-up baby universe right before the Big Bang, that would be impossible, Carroll said. The universe didn’t expand into space; space itself expanded.

“No matter where you are in the universe, if you trace yourself back 14 billion years, you come to this point where it was extremely hot, dense and rapidly expanding,” he said.

No one knows exactly what was happening in the universe until 1 second after the Big Bang, when the universe cooled off enough for protons and neutrons to collide and stick together. Many scientists do think that the universe went through a process of exponential expansion called inflation during that first second. This would have smoothed out the fabric of space-time and could explain why matter is so evenly distributed in the universe today.

Before the bang

It’s possible that before the Big Bang, the universe was an infinite stretch of an ultrahot, dense material, persisting in a steady state until, for some reason, the Big Bang occured. This extra-dense universe may have been governed by quantum mechanics, the physics of the extremely small scale, Carroll said. The Big Bang, then, would have represented the moment that classical physics took over as the major driver of the universe’s evolution.

For Stephen Hawking, this moment was all that mattered: Before the Big Bang, he said, events are unmeasurable, and thus undefined. Hawking called this the no-boundary proposal: Time and space, he said, are finite, but they don’t have any boundaries or starting or ending points, the same way that the planet Earth is finite but has no edge.

“Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory and say that time began at the Big Bang,” he said in an interview on the National Geographic show “StarTalk” in 2018.

Or perhaps there was something else before the Big Bang that’s worth pondering. One idea is that the Big Bang isn’t the beginning of time, but rather that it was a moment of symmetry. In this idea, prior to the Big Bang, there was another universe, identical to this one but with entropy increasing toward the past instead of toward the future.

Increasing entropy, or increasing disorder in a system, is essentially the arrow of time, Carroll said, so in this mirror universe, time would run opposite to time in the modern universe and our universe would be in the past. Proponents of this theory also suggest that other properties of the universe would be flip-flopped in this mirror universe. For example, physicist David Sloan wrote in the University of Oxford Science Blog, asymmetries in molecules and ions (called chiralities) would be in opposite orientations to what they are in our universe.

A related theory holds that the Big Bang wasn’t the beginning of everything, but rather a moment in time when the universe switched from a period of contraction to a period of expansion. This “Big Bounce” notion suggests that there could be infinite Big Bangs as the universe expands, contracts and expands again. The problem with these ideas, Carroll said, is that there’s no explanation for why or how an expanding universe would contract and return to a low-entropy state.

Carroll and his colleague Jennifer Chen have their own pre-Big Bang vision. In 2004, the physicists suggested that perhaps the universe as we know it is the offspring of a parent universe from which a bit of space-time has ripped off.

It’s like a radioactive nucleus decaying, Carroll said: When a nucleus decays, it spits out an alpha or beta particle. The parent universe could do the same thing, except instead of particles, it spits out baby universes, perhaps infinitely. “It’s just a quantum fluctuation that lets it happen,” Carroll said. These baby universes are “literally parallel universes,” Carroll said, and don’t interact with or influence one another.

If that all sounds rather trippy, it is — because scientists don’t yet have a way to peer back to even the instant of the Big Bang, much less what came before it. There’s room to explore, though, Carroll said. The detection of gravitational waves from powerful galactic collisions in 2015 opens the possibility that these waves could be used to solve fundamental mysteries about the universes’ expansion in that first crucial second.

Theoretical physicists also have work to do, Carroll said, like making more-precise predictions about how quantum forces like quantum gravity might work.

“We don’t even know what we’re looking for,” Carroll said, “until we have a theory.”

https://www.livescience.com/65254-what-happened-before-big-big.html

time

by MIKE MCRAE

For around a century it’s been thought that particles don’t have defined properties until we nail them down with a measurement.

That kind of quantum madness opens up a whole world of counter-intuitive paradoxes. Take this one, for example – it’s possible for a single particle to experience two sequences of events at the same time, making it impossible to know which came first.

Physicists from the University of Queensland designed a race course for light that forced a single particle to traverse two pathways at once, making it impossible to say in which order it completed a pair of operations.

In boring old everyday life you could roll a single ball down a ramp and have it ring bell A and then ring bell B. Or, if you’d prefer, you could roll it down another ramp and have it ring B before A.

If you want to get fancy you could even set up a rig so one bell causes the other bell to ring.

None of this is mind blowing, since we’re used to events in the Universe having a set order, where one thing precedes another in such a way that we presume an order of causation.

But nothing is so simple when we accept that reality is a blur of possibility prior to it being measured.

To demonstrate this, the physicists created a physical equivalent of something called a quantum switch, where multiple operations occur while a particle is in a superposition of all its possible locations.

Keeping it simple, the team set up a pathway that split apart and converged again in an interferometer, with access to each fork dependent on the polarisation of the light entering it.

Light waves travelling down each fork in the pathway would then merge and interfere to create a distinctive pattern depending on its properties.

In this particular case, the two light waves were actually the same photon taking both paths at the same time.

Before being measured, a photon can be either vertically or horizontally polarised. Or, more precisely, it’s polarised both vertical and horizontal at the same time until a measurement confirms one over the other.

Since this undefined photon’s polarisation is both vertical and horizontal, it enters both pathways, with the vertically polarised version of the photon barrelling down one channel and the horizontally polarised version heading down the second.

Following the two paths, the team had the quantum equivalent of those bells we mentioned earlier – in the form of lenses that subtly changed the shape of the photon.

The horizontal polarisation would hit ‘bell’ A before striking B, while the vertical polarisation would strike ‘bell’ B, and then A.

An analysis of the interference pattern of the reunited photon revealed signs of this mess of possible sequences.

On one hand, it’s easy to imagine two separate light particles – one horizontally polarised, the other vertically polarised – passing each lens in separate orders.

That’s not what happened, though. This was a single photon with two possible histories, neither of which set in reality until they’re measured.

While the events A and B were independent in this quantum switch, they could be linked to affect one another. A could cause B, or B could cause A … all depending on which history you wanted after the event.

Putting aside daydreams of travelling back in time to undo that big mistake (what were you thinking?!), this does have one possible practical application in the emerging field of quantum communications.

Transmitting photons down a noisy channel could be disastrous for their quantum information, quickly making a mess of their precious superposition. Sending them down channels fitted with a quantum switch, however, could in principle give the quantum information an opportunity to get through.

A paper the team published on the pre-peer review website arxiv.org back in July shows how a quantum switch applied to two noisy channels can allow a superposition to survive.

Whatever weird clockwork is going on in reality’s basement, we won’t pretend to understand it. But the very fact physicists are able to craft it into new technology is truly mindblowing in itself.

This research was published in Physical Review Letters.

https://www.sciencealert.com/quantum-switch-causation-superposition-applied-technology

Stephen Hawking submitted the final version of his last scientific paper just two weeks before he died, and it lays the theoretical groundwork for discovering a parallel universe.

Hawking, who passed away on Wednesday aged 76, was co-author to a mathematical paper which 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 on March 4, ten 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, Cornell University website which tracks scientific papers before they are published, has a record of the paper including the March 2018 update.

According to The Sunday Times, the contents of the paper sets out the mathematics necessary for a deep-space probe to collect evidence which 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 on-board.

Thomas Hertog, a physics professor who co-authored 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.

https://www.sciencealert.com/stephen-hawking-submitted-a-paper-on-parallel-universes-just-before-he-died

Thanks to Kebmodee for bringing this to the It’s Interesting community.

By Jeffrey Bennett

It has been exactly 100 years since Albert Einstein presented his theory of general relativity to an audience of scientists on November 25, 1915. While virtually everyone has heard of Einstein and his theory, very few people have any idea of what the theory actually is.

This is a shame, not only because there is a great public thirst for understanding of it, but also because relativity is important, for at least four major reasons.

General relativity provides our modern understanding of space, time and gravity — which means it’s crucial to almost everything we do in physics and astronomy. For example, you cannot understand black holes, the expansion of the universe or the Big Bang without first understanding the basic ideas of relativity. Though few people realize it, Einstein’s famous equation E = mc2 is actually part of the theory of relativity, which means that relativity also explains how the sun shines and how nuclear power works.

A second reason everyone should know about relativity lies in the way it changes our perception of reality. Relativity tells us that our ordinary perceptions of time and space are not universally valid. Instead, space and time are intertwined as four-dimensional space-time.

In our ordinary lives, we perceive only three dimensions—length, width and depth—and we assume that this perception reflects reality. However, in space-time, the four directions of possible motion are length, width, depth and time. (Note that time is not “the” fourth dimension; it is simply one of the four.)

Although we cannot picture all four dimensions of space-time at once, we can imagine what things would look like if we could. In addition to the three spatial dimensions of space-time that we ordinarily see, every object would be stretched out through time. Objects that we see as three-dimensional in our ordinary lives would appear as four-dimensional objects in space-time. If we could see in four dimensions, we could look through time just as easily as we look to our left or right. If we looked at a person, we could see every event in that person’s life. If we wondered what really happened during some historical event, we’d simply look to find the answer.

To see why this is so revolutionary, imagine that you met someone today who deeply believed that Earth is the center of the universe. You would probably feel sorry for this person, knowing that his or her entire world view is based on an idea disproven more than 400 years ago.

Now imagine that you met someone who still believed that time and space are independent and absolute — which, of course, describes almost everyone — even though we’ve known that’s not the case for a century now. Shouldn’t we feel equally sorry for all who hold this modern misconception?

It seems especially unfortunate once you realize that the ideas of relativity are not particularly difficult to understand. Indeed, I believe we could begin teaching relativity in elementary school in much the same way that we teach young children about the existence of atoms, even though few will ever study quantum mechanics.

My third reason for believing relativity is important lies in what Einstein’s discovery tells us about human potential. The science of relativity may seem disconnected from most other human endeavors, but I believe Einstein himself proved otherwise. Throughout his life, Einstein argued eloquently for human rights, human dignity and a world of peace and shared prosperity. His belief in underlying human goodness is all the more striking when you consider that he lived through both World Wars, that he was driven out of Germany by the rise of the Nazis, that he witnessed the Holocaust that wiped out more than six million of his fellow Jews, and that he saw his own discoveries put to use in atomic bombs.

No one can say for sure how he maintained his optimism in the face of such tragedies, but I see a connection to his discovery of relativity. Einstein surely recognized that a theory that so challenged our perceptions of reality might have been dismissed out of hand at other times in history, but that we now live in a time when, thanks to the process that we call science, the abundant evidence for relativity allowed for its acceptance.

This willingness to make judgments based on evidence shows that we are growing up as a species. We have not yet reached the point where we always show the same willingness in all our other endeavors, but the fact that we’ve done it for science suggests we have the potential.

Finally, on a philosophical level, relativity is profound. Only about a month before his death in 1955, Einstein wrote: “Death signifies nothing … the distinction between past, present and future is only a stubbornly persistent illusion.” As this suggests, relativity raises interesting questions about what the passage of time really means.

Because these are philosophical questions, they do not have definitive answers, and you will have to decide for yourself what these questions mean to you. But I believe that one thing is clear. Einstein showed that even though space and time can independently differ for different observers, the four-dimensional space-time reality is the same for everyone.

This implies that events in space-time have a permanence to them that cannot be taken away. Once an event occurs, in essence it becomes part of the fabric of our universe. Every human life is a series of events, and this means that when we put them all together, each of us is creating our own, indelible mark on the universe. Perhaps if everyone understood that, we might all be a little more careful to make sure that the mark we leave is one that we are proud of.

So there you have it. Relativity is necessary to comprehend the universe as we know it, it helps us understand the potential we all share when we put our brains to work for the common good, and if we all understood it we might treat each other a little more kindly.

http://www.cnn.com/2015/11/25/opinions/bennett-einstein-theory-of-relativity/index.html