How Can Space Travel Faster Than The Speed Of Light?

Image Credit: ESA/Hubble & NASA, Acknowledgement: Flickr user Det58

Cosmologists are intellectual time travelers. Looking back over billions of years, these scientists are able to trace the evolution of our Universe in astonishing detail. 13.8 billion years ago, the Big Bang occurred. Fractions of a second later, the fledgling Universe expanded exponentially during an incredibly brief period of time called inflation. Over the ensuing eons, our cosmos has grown to such an enormous size that we can no longer see the other side of it.

But how can this be? If light’s velocity marks a cosmic speed limit, how can there possibly be regions of spacetime whose photons are forever out of our reach? And even if there are, how do we know that they exist at all?

The Expanding Universe

Like everything else in physics, our Universe strives to exist in the lowest possible energy state possible. But around 10^-36 seconds after the Big Bang, inflationary cosmologists believe that the cosmos found itself resting instead at a “false vacuum energy” – a low-point that wasn’t really a low-point. Seeking the true nadir of vacuum energy, over a minute fraction of a moment, the Universe is thought to have ballooned by a factor of 10⁵⁰.

Since that time, our Universe has continued to expand, but at a much slower pace. We see evidence of this expansion in the light from distant objects. As photons emitted by a star or galaxy propagate across the Universe, the stretching of space causes them to lose energy. Once the photons reach us, their wavelengths have been redshifted in accordance with the distance they have traveled.

Two sources of redshift: Doppler and cosmological expansion; modeled after Koupelis & Kuhn. Bottom: Detectors catch the light that is emitted by a central star. This light is stretched, or redshifted, as space expands in between. Credit: Brews Ohare.

This is why cosmologists speak of redshift as a function of distance in both space and time. The light from these distant objects has been traveling for so long that, when we finally see it, we are seeing the objects as they were billions of years ago.

The Hubble Volume

Redshifted light allows us to see objects like galaxies as they existed in the distant past; but we cannot see allevents that occurred in our Universe during its history. Because our cosmos is expanding, the light from some objects is simply too far away for us ever to see.

The physics of that boundary rely, in part, on a chunk of surrounding spacetime called the Hubble volume. Here on Earth, we define the Hubble volume by measuring something called the Hubble parameter (H₀), a value that relates the apparent recession speed of distant objects to their redshift. It was first calculated in 1929, when Edwin Hubble discovered that faraway galaxies appeared to be moving away from us at a rate that was proportional to the redshift of their light.

Fit of redshift velocities to Hubble’s law. Credit: Brews Ohare

Dividing the speed of light by H₀, we get the Hubble volume. This spherical bubble encloses a region where all objects move away from a central observer at speeds less than the speed of light. Correspondingly, all objects outside of the Hubble volume move away from the center faster than the speed of light.

Yes, “faster than the speed of light.” How is this possible?

The Magic of Relativity

The answer has to do with the difference between special relativity and general relativity. Special relativity requires what is called an “inertial reference frame” – more simply, a backdrop. According to this theory, the speed of light is the same when compared in all inertial reference frames. Whether an observer is sitting still on a park bench on planet Earth or zooming past Neptune in a futuristic high-velocity rocket ship, the speed of light is always the same. A photon always travels away from the observer at 300,000,000 meters per second, and he or she will never catch up.

General relativity, however, describes the fabric of spacetime itself. In this theory, there is no inertial reference frame. Spacetime is not expanding with respect to anything outside of itself, so the the speed of light as a limit on its velocity doesn’t apply. Yes, galaxies outside of our Hubble sphere are receding from us faster than the speed of light. But the galaxies themselves aren’t breaking any cosmic speed limits. To an observer within one of those galaxies, nothing violates special relativity at all. It is the space in between us and those galaxies that is rapidly proliferating and stretching exponentially.

The Observable Universe

Now for the next bombshell: The Hubble volume is not the same thing as the observable Universe.

To understand this, consider that as the Universe gets older, distant light has more time to reach our detectors here on Earth. We can see objects that have accelerated beyond our current Hubble volume because the light we see today was emitted when they were within it.

Strictly speaking, our observable Universe coincides with something called the particle horizon. The particle horizon marks the distance to the farthest light that we can possibly see at this moment in time – photons that have had enough time to either remain within, or catch up to, our gently expanding Hubble sphere.

And just what is this distance? A little more than 46 billion light years in every direction – giving our observable Universe a diameter of approximately 93 billion light years, or more than 500 billion trillion miles.

Image credit: Htwins

(A quick note: the particle horizon is not the same thing as the cosmological event horizon. The particle horizon encompasses all the events in the past that we can currently see. The cosmological event horizon, on the other hand, defines a distance within which a future observer will be able to see the then-ancient light our little corner of spacetime is emitting today.

In other words, the particle horizon deals with the distance to past objects whose ancient light that we can see today; the cosmological event horizon deals with the distance that our present-day light that will be able to travel as faraway regions of the Universe accelerate away from us.)

Dark Energy

Thanks to the expansion of the Universe, there are regions of the cosmos that we will never see, even if we could wait an infinite amount of time for their light to reach us. But what about those areas just beyond the reaches of our present-day Hubble volume? If that sphere is also expanding, will we ever be able to see those boundary objects?

This depends on which region is expanding faster – the Hubble volume or the parts of the Universe just outside of it. And the answer to that question depends on two things: 1) whether H₀ is increasing or decreasing, and 2) whether the Universe is accelerating or decelerating. These two rates are intimately related, but they are not the same.

In fact, cosmologists believe that we are actually living at a time when H₀ is decreasing; but because of dark energy, the velocity of the Universe’s expansion is increasing.

That may sound counter-intuitive, but as long as H₀ decreases at a slower rate than that at which the Universe’s expansion velocity is increasing, the overall movement of galaxies away from us still occurs at an accelerated pace. And at this moment in time, cosmologists believe that the Universe’s expansion will outpace the more modest growth of the Hubble volume.

So even though our Hubble volume is expanding, the influence of dark energy appears to provide a hard limit to the ever-increasing observable Universe.

Our Earthly Limitations

Cosmologists seem to have a good handle on deep questions like what our observable Universe will someday look like and how the expansion of the cosmos will change. But ultimately, scientists can only theorize the answers to questions about the future based on their present-day understanding of the Universe. Cosmological timescales are so unimaginably long that it is impossible to say much of anything concrete about how the Universe will behave in the future. Today’s models fit the current data remarkably well, but the truth is that none of us will live long enough to see whether the predictions truly match all of the outcomes.

Disappointing? Sure. But totally worth the effort to help our puny brains consider such mind-bloggling science – a reality that, as usual, is just plain stranger than fiction.

as Posted on February 21, 2015 by FQtQ Contributor in Physics onhttp://www.fromquarkstoquasars.com/

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New Contact Lens Comes With Tiny Telescope, Letting You To Zoom In & Out With A Wink

Swiss researchers are developing contact lenses that contain tiny telescopes to boost vision and zoom in and out with the wink of an eye. Credit: Eric Tremblay and Joe Ford / EPFL.

We generally take our vision for granted, which is rather surprising, considering that there are hundreds of millions of people in the world who have vision problems—some 285 million people worldwide. Although a majority of these issues can be attributed to insufficient access to basic medical care, even those with access to modern medicine face a number of illnesses and disorders. Indeed, the number of people in the United States suffering from various ocular disorders is quite alarming, and the outlook for most of us is a rather bleak.

According to the American Academy of Ophthalmology, nearly 22 million Americans who are over age 40 have cataracts (the most common cause of vision loss in adults). By the time that they reach 80, more than half of all Americans will have cataracts. On top of this, more than 2 million people living in the United States who are over 50 have age-related muscular degeneration. Another  4.4 million Americans over 40 have  diabetic retinopathy…the list of ocular disorders goes on and on.

However, new hope could be on the horizon.

Swiss researchers are in the process of developing contact lenses that contain tiny telescopes. But before you get any fancy ideas, no, these will not allow you to spy on your neighbor, cheat on a math test, or peer into the icy reaches of the outer solar system (though who knows, perhaps the devices will have such capabilities someday). But for now, the devices offer a boost  to vision and can allow individuals to zoom in on an object more than 2.8 times, which is more than enough for many people with vision issues. Oh, and it lets you do it all with the wink of an eye.

Yes, you read that correctly. The new contact lens contains an extremely thin, reflective telescope that is activated by winking. And amazingly, it is just 1.55 millimeter-thick.

Of course, some may be a bit concerned by this technology. What if you sneeze, what if you get dust in your eye? Won’t the device start zooming in and out sporadically? The engineers behind the product say that this shouldn’t be a concern. The lenses come with something called “smart glasses.” These are supposed to be sophisticated enough to respond to the wearer’s winks, but not their blinks i.e., the device should be able to differentiate between the two.

Ultimately, the winking trigger should allow individuals to seamlessly switch back and forth between normal and magnified vision. Moreover, the products can actually track eye movement. This will make the contacts easier to use, as individuals do not need to tilt their head in order to see different objects by looking through different portions of the lens (which is a great advancement from previous models and current devices).

The prototype was unveiled by Eric Tremblay from the Ecole Polytechnique Federale de Lausanne in Switzerland at the American Association for the Advancement of Science (AAAS) on Friday (Feb. 13, 2015).

Although AMD, and many similar issues, do not generally result in total vision loss, these conditions often make it difficult to preform everyday tasks and function effectively in society. According to the National Eye Institute, “AMD can interfere with simple everyday activities, such as the ability to see faces, drive, read, write, or do close work, such as cooking or fixing things around the house.” Part of the reason that this device is so effective is because, not only is it capable of magnifying objects 2.8 times, it removes much of the “clunkiness” of current options.

“It’s very important and hard to strike a balance between function and the social costs of wearing any kind of bulky visual device. There is a strong need for something more integrated, and a contact lens is an attractive direction,” Tremblay asserts.

Tremblay says that this device could bring some much needed relief to people suffering from various vision issues; however, he simultaneously cautions that the technology is still in its early stages: “We think these lenses hold a lot of promise for low vision and age-related macular degeneration…at this point this is still research, but we are hopeful it will eventually become a real option for people with AMD.”

Interestingly enough, these little devices didn’t start out as a medical device. At least, not really. The contacts were funded by the Pentagon, and they were meant to serve as a form of bionic vision for soldiers. But as is true of many other technological deices that were initially created for the military, they could bring new hope to millions of ordinary citizens.

Posted on February 17, 2015 by Jolene Creighton in News, Technology

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Scientists Just Discovered Nature’s Strongest Material (known to man)

Microscopic image of limped teeth. Via University of Portsmouth

We use nature as a guide for producing a lot of different technologies. We watch birds fly, and we dream of ways that we can soar across the skies with wing-like structures. We turn to the ocean, we see the way that fish glide through the waters, and then we use these principles to develop fins for our feet, allowing us to travel through the sea at increased speeds. Now, we may be turning to a new part of nature in order to develop ways to create stronger materials. Where will we be looking? Apparently, at the teeth of tiny snail-like creatures.

In a study that will be coming out this month from the Journal of the Royal Society Interface, British researchers announce that they have discovered the strongest natural material known to man. It was found in the teeth of shelled, aquatic creatures that are known as limpets. Ultimately, the teeth take the place of the previous strongest biological material on Earth—spider silk.

Lead author Asa Barber said that this new find could help us adapt the material into technologies to build better planes, boats, dental fillings, and a host of other devices. Since this is the strongest known “natural” material, some may think that the material that makes up the teeth are only strong when compared to other natural materials. However, they also beat many of our more impressive man-made materials. For example, the teeth surpass Kevlar, which is a synthetic fiber that we use to make bulletproof vests and puncture-proof tires.

To give you a better understanding of just how strong this material is, it  can be compared to a strand of spaghetti that is able to hold up more than 3,300 pounds (1,300 kg).

In order to test the strength of this material, Barber looked at the teeth fibers for tensile strength (tensile strength is the amount of force that a material can withstand without breaking). To do this, he attached each end of the fiber to a lever and pulled on the sample with an atomic force microscope. He found that the material had a strength of 5 gigapascals, which is a staggering five times the strength of most spider silks (which, as was mentioned, was the previous contender for the strongest known material).

The teeth are composed of very thin fibers that contain a hard mineral called “goethite.” Limpets use them to scrape food off of rocks, and the key to their strength is their size. They are so small they must be examined with a microscope. and are just 1/100th the diameter of a human hair. The ultra-thin filaments are so little that they are able to avoid the holes and defects that we commonly find in larger materials.

Although they are very small, they can be put together in order to make larger materials that are similarly flawless—they do no weaken like most materials when constructed in such a manner.

“Generally a big structure has lots of flaws and can break more easily than a smaller structure, which has fewer flaws and is stronger,” Barber said in a university press release. “The problem is that most structures have to be fairly big so they’re weaker than we would like. Limpet teeth break this rule as their strength is the same no matter what the size.”

Barber asserts that we should continue to look to nature, as we never know what new resources we may find there: “All the things we observe around us, such as trees, the shells of sea creatures and the limpet teeth studied in this work, have evolved to be effective at what they do. Nature is a wonderful source of inspiration for structures that have excellent mechanical properties.”

as posted on http://www.fromquarkstoquasars.com/

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