Astronomers Discover The Largest Structure In The Universe

An international team of astronomers, led by academics from the University of Central Lancashire (UCLan), has found the largest known structure in the universe. 

The large quasar group (LQG) is so large that it would take a vehicle travelling at the speed of light some 4 billion years to cross it. 

The team publish their results in the journal Monthly Notices of the Royal Astronomical Society.

Quasars are the nuclei of galaxies from the early days of the universe that undergo brief periods of extremely high brightness that make them visible across huge distances. These periods are 'brief' in astrophysics terms but actually last 10-100 million years.

Since 1982 it has been known that quasars tend to group together in clumps or 'structures' of surprisingly large sizes, forming large quasar groups or LQGs.

The coloured background indicates the peaks and troughs in the occurrence of quasars at the distance of the LQG. Darker colours indicate more quasars, lighter colours indicate fewer quasars. The LQG is clearly seen as a long chain of peaks indicated by black circles. (The red crosses mark the positions of quasars in a different and smaller LQG). The horizontal and vertical axes represent right ascension and declination, the celestial equivalent of longitude and latitude. The map covers around 29.4 by 24 degrees on the sky, indicating the huge scale of the newly discovered structure. Credit: R. G. Clowes / UCLan

The team, led by Dr Roger Clowes from UCLan's Jeremiah Horrocks Institute, has identified the LQG which is so significant in size it also challenges the Cosmological Principle: the assumption that the universe, when viewed at a sufficiently large scale, looks the same no matter where you are observing it from.

The modern theory of cosmology is based on the work of Albert Einstein, and depends on the assumption of the Cosmological Principle. The Principle is assumed but has never been demonstrated observationally 'beyond reasonable doubt'.

To give some sense of scale, our galaxy, the Milky Way, is separated from its nearest neighbour, the Andromeda Galaxy, by about 0.75 Megaparsecs (Mpc) or 2.5 million light-years.

Whole clusters of galaxies can be 2-3 Mpc across but LQGs can be 200 Mpc or more across. Based on the Cosmological Principle and the modern theory of cosmology, calculations suggest that astrophysicists should not be able to find a structure larger than 370 Mpc.

Dr Clowes' newly discovered LQG however has a typical dimension of 500 Mpc. But because it is elongated, its longest dimension is 1200 Mpc (or 4 billion light years) - some 1600 times larger than the distance from the Milky Way to Andromeda.

Dr Clowes said:

"While it is difficult to fathom the scale of this LQG, we can say quite definitely it is the largest structure ever seen in the entire universe. This is hugely exciting – not least because it runs counter to our current understanding of the scale of the universe.

"Even travelling at the speed of light, it would take 4 billion years to cross. This is significant not just because of its size but also because it challenges the Cosmological Principle, which has been widely accepted since Einstein. Our team has been looking at similar cases which add further weight to this challenge and we will be continuing to investigate these fascinating phenomena."

Via: "The Royal Astronomical Society"

NASA Starts Work On Real Star Trek Warp Drive

"Perhaps a Star Trek experience within our lifetime is not such a remote possibility." These are the words of Dr. Harold "Sonny" White, the Advanced Propulsion Theme Lead for the NASA Engineering Directorate. Dr. White and his colleagues don't just believe a real life warp drive is theoretically possible; they've already started the work to create one.

Searching For Warp Bubbles

The answer lies precisely in those laws of physics. Dr. White and other physicists have found loopholes in some mathematical equations—loopholes that indicate that warping the space-time fabric is indeed possible.

Working at NASA Eagleworks—a skunkworks operation deep at NASA's Johnson Space Center—Dr. White's team is trying to find proof of those loopholes. They have "initiated an interferometer test bed that will try to generate and detect a microscopic instance of a little warp bubble" using an instrument called the White-Juday Warp Field Interferometer.

It may sound like a small thing now, but the implications of the research huge. In his own words:

Although this is just a tiny instance of the phenomena, it will be existence proof for the idea of perturbing space time-a "Chicago pile" moment, as it were. Recall that December of 1942 saw the first demonstration of a controlled nuclear reaction that generated a whopping half watt. This existence proof was followed by the activation of a ~ four megawatt reactor in November of 1943. Existence proof for the practical application of a scientific idea can be a tipping point for technology development.

By creating one of these warp bubbles, the spaceship's engine will compress the space ahead and expand the space behind, moving it to another place without actually moving, and carrying none of the adverse effects of other travel methods. According to Dr. White, "by harnessing the physics of cosmic inflation, future spaceships crafted to satisfy the laws of these mathematical equations may actually be able to get somewhere unthinkably fast—and without adverse effects."

He says that, if everything is confirmed in these practical experiments, we would be able to create an engine that will get us to Alpha Centauri "in two weeks as measured by clocks here on Earth." The time will be the same in the spaceship and on Earth, he claims, and there will not be "tidal forces inside the bubble, no undue issues, and the proper acceleration is zero. When you turn the field on, everybody doesn't go slamming against the bulkhead, which would be a very short and sad trip."

There was only one problem with all this: where does the energy come from? While we knew that warp drives were theoretically possible, physicists have always argued that they would require a ball of exotic matter the size of Jupiter to power it. Clearly, that was not practical. But thankfully, Dr. White has found a solution that changes the game completely.

The Eagleworks team has discovered that the energy requirements are much lower than previously thought. If they optimize the warp bubble thickness and "oscillate its intensity to reduce the stiffness of space time," they would be able to reduce the amount of fuel to manageable amount: instead of a Jupiter-sized ball of exotic matter, you will only need 500 kilograms to "send a 10-meter bubble (32.8 feet) at an effective velocity of 10c."

Ten c! That's ten times the speed of light, people (remember, the ship itself would not go faster than the speed of light. But effectively it will seem like it does).

That means that we would be able to visit Gliese 581g—a planet similar to Earth 20 light years away from our planet—in two years. Two years is nothing. It took Magellan three years to circumnavigate around our home planet—from August 1519 to September 1522. A four year roundtrip to see a planet like Earth is completely doable. And there are even closer destinations where we can send robots or astronauts.

The important thing is that there is now a door open to a different kind of exploration. That, like Dr. White says, "perhaps a Star Trek experience within our lifetime is not such a remote possibility." We may be witnessing the very beginning of a new age of space exploration, one that would finally take us from our pale blue dot back to where we belong.

Via: "Gizmodo"

How The Speed Of Light Was Measured In 1676

In 1676, the Danish astronomer Ole Roemer (1644–1710) became the first person to measure the speed of light. Until that time, scientists assumed that the speed of light was either too fast to measure or infinite. The dominant view, vigorously argued by the French philosopher Descartes, favored an infinite speed.

Roemer, working at the Paris Observatory, was not looking for the speed of light when he found it. Instead, he was compiling extensive observations of the orbit of Io, the innermost of the four big satellites of Jupiter discovered by Galileo in 1610. By timing the eclipses of Io by Jupiter, Roemer hoped to determine a more accurate value for the satellite’s orbital period. Such observations had a practical importance in the seventeenth century. 

Galileo himself had suggested that tables of the orbital motion of Jupiter’s satellites would provide a kind of “clock” in the sky. Navigators and mapmakers anywhere in the world might use this clock to read the absolute time (the standard time at a place of known longitude, like the Paris Observatory). 

Then, by determining the local solar time, they could calculate their longitude from the time difference. This method of finding longitude eventually turned out to be impractical and was abandoned after the development of accurate seagoing timepieces. But the Io eclipse data unexpectedly solved another important scientific problem—the speed of light.

The orbital period of Io is now known to be 1.769 Earth days. The satellite is eclipsed by Jupiter once every orbit, as seen from the Earth. By timing these eclipses over many years, Roemer noticed something peculiar. The time interval between successive eclipses became steadily shorter as the Earth in its orbit moved toward Jupiter and became steadily longer as the Earth moved away from Jupiter. These differences accumulated. From his data, Roemer estimated that when the Earth was nearest to Jupiter (at E1), eclipses of Io would occur about eleven minutes earlier than predicted based on the average orbital period over many years. And 6.5 months later, when the Earth was farthest from Jupiter (at E2), the eclipses would occur about eleven minutes later than predicted.

Roemer measured the speed of light by timing eclipses of Jupiter's moon Io. In this figure, S is the Sun, E1 is the Earth when closest to Jupiter (J1) and E2 is the Earth about six months later, on the opposite side of the Sun from Jupiter (J2). When the Earth is at E2, the light from the Jupiter system has to travel an extra distance represented by the diameter of the Earth's orbit. This causes a delay in the timing of the eclipses. Roemer measured the delay and, knowing approximately the diameter of the Earth's orbit, made the first good estimate of the speed of light. Illustration by Diana Kline.

Roemer knew that the true orbital period of Io could have nothing to do with the relative positions of the Earth and Jupiter. In a brilliant insight, he realized that the time difference must be due to the finite speed of light. That is, light from the Jupiter system has to travel farther to reach the Earth when the two planets are on opposite sides of the Sun than when they are closer together. Romer estimated that light required twenty-two minutes to cross the diameter of the Earth’s orbit. The speed of light could then be found by dividing the diameter of the Earth’s orbit by the time difference.

The Dutch scientist Christiaan Huygens, who first did the arithmetic, found a value for the speed of light equivalent to 131,000 miles per second. The correct value is 186,000 miles per second. The difference was due to errors in Roemer’s estimate for the maximum time delay (the correct value is 16.7, not 22 minutes), and also to an imprecise knowledge of the Earth’s orbital diameter. More important than the exact answer, however, was the fact that Roemer’s data provided the first quantitative estimate for the speed of light, and it was in the right ballpark.

Roemer returned to Denmark in 1681, where he pursued a distinguished career in both science and government. He designed and built the most accurate astronomical instruments of his time and made extensive observations. He later served as mayor and prefect of police of Copenhagen and ultimately as head of the State Council. Roemer is remembered today of course not for his high political office but for being the first person to measure the speed of light.

Via: "AMNH"

Above Image: USS Atalanta - Warp Speed

By Vatorx