Archive for the ‘Astronomy’ Category

An infinite and timeless universe measured with an accuracy of 1%!

January 10, 2014

A new paper has been capturing some headlines. It is all completely beyond me and while the Abstract – written presumably in English – may be perfectly intelligible for an astronomer or a physicist, it is totally incomprehensible for me. But some of the quotations in the accompanying press release – which were picked up and reported widely in the mainstream media (here and here for example) – sounded strangely illogical.

from the Press Release

  • Today the Baryon Oscillation Spectroscopic Survey (BOSS) Collaboration announced that BOSS has measured the scale of the universe to an accuracy of one percent.
  • “One-percent accuracy in the scale of the universe is the most precise such measurement ever made,” says BOSS’s principal investigator, David Schlegel, a member of the Physics Division of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). 
  • … the BOSS results suggest that dark energy is a cosmological constant whose strength does not vary in space or time. 
  • …. the BOSS analysis “also provides one of the best-ever determinations of the curvature of space. The answer is, it’s not curved much.”
  • “One of the reasons we care is that a flat universe has implications for whether the universe is infinite,” says Schlegel.
  • … “That means – while we can’t say with certainty that it will never come to an end – it’s likely the universe extends forever in space and will go on forever in time. Our results are consistent with an infinite universe.”
  • … By 380,000 years after the big bang, however, the temperature of the expanding mixture had cooled enough for light to escape, suffusing the newly transparent universe with intense radiation, which in the 13.4 billion years since has continued to cool to today’s faint but pervasive cosmic microwave background.
  • … BOSS collaborator Beth Reid of Berkeley Lab translates the two-dimensional sky coordinates of galaxies, plus their redshifts, into 3-D maps of the density of galaxies in space. “It’s from fluctuations in the density of galaxies in the volume we’re looking at that we extract the BAO standard ruler,” she says.
  • …. The universe’s expansion history has been measured with unprecedented accuracy during the very stretch of ancient time, over six billion years in the past, when expansion had stopped slowing and acceleration began. …

At this point I gave up.

My knowledge of physics and astronomy is sadly lacking and I cannot be reconciled to a universe which is

  • an expanding universe, where
  • the expansion is accelerating, and where
  • the university is infinite, and
  • timeless, and 
  • has been “measured” to an accuracy of 1%

1% of an infinite universe ought to be infinity in my boggled mind!  Is the “ruler” expanding as well? And did time exist before the Big Bang? And if the universe is “timeless”, is time just an artificial construct? And can infinity expand without having a larger infinity?

Oh well! I’m afraid I cannot picture this universe – but I am only an engineer.

Lauren Anderson et al, The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in the Data Release 10 and 11 galaxy samplesMonthly Notices of the Royal Astronomical Society, 2014.

Abstract: We present a one per cent measurement of the cosmic distance scale from the detections of the baryon acoustic oscillations in the clustering of galaxies from the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III (SDSS-III). Our results come from the Data Release 11 (DR11) sample, containing nearly one million galaxies and covering approximately 8500 square degrees and the redshift range 0.2the baryon acoustic oscillation (BAO) feature. The acoustic features are detected at a significance of over 7σ in both the correlation function and power spectrum. Fitting for the position of the acoustic features measures the distance relative to the sound horizon at the drag epoch, rd, which has a value of rd,fid=149.28Mpc in our fiducial cosmology. We find DV=(1264±25Mpc)(rd/rd,fid) at z=0.32 and DV=(2056±20Mpc)(rd/rd,fid) at z=0.57. At 1.0 per cent, this latter measure is the most precise distance constraint ever obtained from a galaxy survey. Separating the clustering along and transverse to the line-of-sight yields measurements at z=0.57 of DA=(1421±20Mpc)(rd/rd,fid) and H=(96.8±3.4km/s/Mpc)(rd,fid/rd). Our measurements of the distance scale are in good agreement with previous BAO measurements and with the predictions from cosmic microwave background data for a spatially flat cold dark matter model with a cosmological constant.

Another Sunday, another week — but why?

November 3, 2013

The seven-day week must go down as being one of the most “unnatural” yet persistent creations of man. It is very practical of course, but why do we have it?

There are no discernible periodicities that we have been able to find outside ourselves which take 7 days. There are no periodicities within ourselves either that are 7 days or multiples of 7 days.  There are no celestial or astronomical cycles in tune with 7 days. There are no movements of the sun or the moon or the stars that give rise to a 7-day period. There are no weather or climate phenomena that repeat with a 7-day period. There are no human behavioural patterns that dance to a 7-day tune. There are no living things that have a 7-day life cycle. (There is a branch of pseudoscience which claims that living cells may be associated with a weekly or a half-weekly cycle – a circaseptan or a circasemiseptan rythm – but this is still in the realms of fantasy).

It would seem logical that our ancestors must have first noted the daily cycle long before they were even recognisable as human.  As humans they probably then noted the lunar cycle of about 29 days and the yearly cycle of about 365 days. Our distant ancestors would also have noted that the period of the yearly cycle was a little more than 12 lunar cycles. By about 35,000 years ago we have evidence that the lunar cycle was known and was being tracked. This evidence is in the form of a tally stick with 29 marks – the Lebombo bone.

The development of beliefs in gods of light and separate gods of darkness is not so difficult to understand. The gods of winds and fires and mountains and rivers are equally understandable. The fact that the lunar cycle was rather badly synchronised with the annual solar cycle could well have led to the concept of sun-gods and moon-goddesses, each with their own areas of influence.  (In fact, considering the imperfection of the design of the universe which is manifested in the lack of synchronisation between the various celestial cycles, it is difficult to understand how a concept of a single all-powerful creator ever arose. Why would such a poor design be the product of an all-powerful creator? Surely he could have managed the simple 3-body problem to synchronise the various rotations of the earth, the moon and the Sun?)

The invention of the seven-day week can best be dated to be at least 5,000 years ago to the time of the Babylonians. It was certainly long before the Old Testament came to be written to fit with the 7-day week which had already been invented and established. The story goes that

the seven-day week was actually invented by the Assyrians, or by Sargon I (King of Akkad at around 2350 B.C.), passed on to the Babylonians, who then passed it on to the Jews during their captivity in Babylon around 600 B.C.  The ancient Romans used the eight-day week, but after the adoption of the Julian calendar in the time of Agustus, the seven-day week came into use in the Roman world. For a while, both the seven and eight day weeks coexisted in the Roman world, but by the time Constantine decided to Christianize the Roman world (around A.D. 321) the eight-day weekly cycle had fallen out of use in favor of the more popular seven-day week.

The idea that the 7-days originates from a division of the lunar cycle into 4 seems improbable. The lunar cycle (synodic period) is 29.5305882 days long. Three weeks of 10 days each or five 6 day weeks would fit better. That the annual cycle of 365.2425 days comes to dominate is not so surprising. Our calendar months are now attuned to the annual cycle and have no direct connection to the lunar cycle. But it is our 7 – day weeks which remain fixed. We adjust the length of our months and have exactly 365 days for each of our  normal years. We then add an extra day every 4 years  but omit 3 such extra days in every 400 years to cover the error. We make our adjustments by adding a day to the month of February for the identified leap years but we do not mess with the 7 days of the week.

It is far more likely that the 7 days comes from the seven celestial objects visible to the naked eye from earth and probably known to man some 5,000 to 10,000 years ago. They were familiar with the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn by then. Naturally each was a god in his own heaven and had to have a day dedicated just to him/her/it. The same 7 celestial objects are used for the days of the week not only in the Greek/Roman Western tradition, but also in Indian astrology. The Chinese /East Asian tradition uses the Sun, Moon, Fire, Water, Wood, Gold and Earth to name the seven days of the week. But this must have come after the 7 day week had already been established elsewhere. (For example, to name up to 10 days they could just have chosen to add days named for the Air, Beasts, Birds ….). Some languages use a numbering system and some use a mixture of all of the above. Rationalists and philosophers and dreamers have tried to shift to 5 and 6, and 8 and 10 day weeks but none of these efforts has managed to challenge the practicality or to dislodge the dominance of the seven-day week.

And now the whole world lives and marches – socially, culturally, politically – to the inexorable beat of the 7-day week.

Just because some long-forgotten astrologer/astronomer decided that he would dedicate each day to one of his seven known celestial gods (and he only had seven)! Even if he (unlikely to have been a “she”) worshipped an Earth-goddess, she must have been considered inferior to the celestial gods. Otherwise we would have had an 8-day week! 

An alien race could be excused for concluding that humans must have evolved from once having seven fingers on each limb. Or that we once had seven limbs and have lost 3. Or that humans have an innate circaseptan rythm requiring extra rest and sleep every 7 days. Or that humans have a physiological need to go binge drinking on the sixth day and need the seventh day to recover!

But if the 7-day week is a Divine creation then the aliens will also have a 7-day week and will not be in the least surprised.

The number seven does have a few special properties:

Not forgetting the Seven Wonders of the Ancient World. But they only came after the seven day week had been invented and introduced.

 

400m asteroid (2013 TV135) could collide with Earth on 26th August 2032

October 18, 2013

Not quite another doomsday prediction but the Russian Vice Premier Dmitry Rogozin was moved to tweet about the threat to blow up the Earth.

Ria Novosti: 

Ukrainian astronomers have discovered a large asteroid that could hit Earth in 2032, though the impact risk is minimal, according to current estimates.

The 410-meter-wide (1,350-foot) minor planet, which has been named 2013 TV135, was first discovered last weekend by the Crimean Astrophysical Observatory in southern Ukraine, according to the International Astronomer Union’s Minor Planet Center.

As of Thursday, the discovery had been confirmed by five more astronomy groups, including in Italy, Spain, the UK and Russia’s Siberian republic of Buryatia, the center said on its website.

The asteroid has been classified as potentially hazardous, a formal tag given to celestial bodies whose orbits bring them closer than 7.5 million km from Earth’s orbit. The minimal distance between the orbits of 2013 TV135 and Earth is currently put at 1.7 million km.

However, it also has a 1 in 63,000 chance of colliding with Earth on August 26, 2032, according to available estimates.

“Here’s a super-task for our space industry,” Russian Deputy Prime Minister Dmitry Rogozin, who has lobbied for Russia to develop asteroid defense systems, said of the asteroid on Twitter on Thursday.

The 2013 TV135 has been given a 1 out of 10 rating on the Torino Scale, which estimates asteroid impact hazards. Only one other asteroid currently has the same rating, with collision risks for all others being “effectively zero,” according to NASA’s Near Earth Object Program.

The 2013 TV135 colliding with Earth would create an explosion estimated to be equivalent to 2,500 megatons of TNT – 50 times greater than the biggest nuclear bomb ever detonated.

Asteroids due to pass close to Earth in the next 200 years are shown in this graphic:

Asteroids That Buzz Planet Earth

Asteroids which will come closest to the Earth in the next 200 years

 

Pluto is a planet with moons after all

July 4, 2013

I grew up in a solar system which had nine planets.

And then poor Pluto was stripped of the honour of being a planet and we had only eight.

But then the “dwarf planets” were defined and Pluto joined this group of 5.

… the International Astronomical Union (IAU) defines a dwarf planet as a celestial body in direct orbit of the Sun that is massive enough for its shape to be controlled by gravitation, but that unlike a planet has not cleared its orbital region of other objects.

The IAU currently recognizes five dwarf planets in the Solar System: Ceres, Pluto, Haumea, Makemake, and Eris.

It is suspected that another hundred or so known objects in the Solar System are dwarf planets.

And we now have at least 13 known planets. Pluto is not only a dwarf planet it also has at least 5 moons and the last 2 have just been named. The 5 are Charon, Styx, Nix, Kerberos and Hydra.

Pluto and its moons: IAU

IAU: 

The International Astronomical Union (IAU) is announcing that the names Kerberos and Styx have officially been recognised for the fourth and fifth moons of Pluto, which were discovered in 2011 and 2012. The names were submitted to the IAU by the leader of the team responsible for the discovery, who had called for the help of the general public in an open contest that attracted a substantial number of participants.

The IAU is pleased to announce that today it has officially recognised the names Kerberos and Styx for the fourth and fifth moons of Pluto respectively (formerly known as P4 and P5). These names were backed by voters in a recently held popular contest, aimed at allowing the public to suggest names for the two recently discovered moons of the most famous dwarf planet in the Solar System.

The new moons were discovered in 2011 and 2012, during observations of the Pluto system made with the NASA/ESA Hubble Space Telescope Wide Field Camera 3, and increasing the number of known Pluto moons to five. Kerberos lies between the orbits of Nix and Hydra, two bigger moons discovered by Hubble in 2005, and Styx lies between Charon, the innermost and biggest moon, and Nix. Both have circular orbits assumed to be in the plane of the other satellites in the system. Kerberos has an estimated diameter of 13 to 34 kilometres, and Styx is thought to be irregular in shape and is 10 to 25 kilometres across.

 

 

Comet C/2013 A1 (Siding Spring) could impact Mars on 19th October 2014

March 21, 2013

Comet Shoemaker–Levy 9  broke apart and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects.

The collision provided new information about Jupiter and highlighted its role in reducing space debris in the inner Solar System.

But a much closer event could be in the offing for next year. A newly discovered comet has been found to have an orbit which takes it extraordinarily close to Mars in October 2014 and the possibility of an impact is 1 in 600. The size of the comet is still uncertain but some estimates are of the nucleus being 50 km in diameter. An impact crater on Mars – if an impact occurs – could then be about 500 km in diameter.

C/2013 A1 (Siding Spring) is a comet originating from the Oort cloud and was only discovered in January this year by Robert H. McNaught at Siding Spring Observatory in Australia,  using a 0.5-meter  Schmidt telescope. By looking at observations made before the comet was identified as a comet on 3rd January, NASA states “Pre-discovery observations located in the archives have extended the observation interval back to Oct. 4, 2012”.

NASA/JPL Near-Earth Object Program Office 
March 5, 2013

On Oct. 19, 2014, Comet 2013 A1 (Siding Spring) will pass extraordinarily close to Mars, almost certainly within 300,000 km of the planet and possibly much closer. Our current best estimate has it passing about 50,000 km from the surface of Mars. This is about 2.5 times the distance of Mars’ outermost satellite Deimos or less than twice the Earth close approach distance of 2012 DA14 on February 15, 2013. Since the observation span available for orbit determination is still relatively short, the current orbit is quite uncertain and the nominal close approach distance will change as additional observations are included in future orbit estimates. Currently, Mars lies directly within the range of possible paths for the comet and we can’t exclude the possibility that the comet might impact Mars. Our current estimate for the impact probability is less than one in six hundred and we expect that future observations will allow us to completely rule out a Mars impact.

This computer graphic depicts the orbit of comet 2013 A1 (Siding Spring) through the inner solar system. Image credit: NASA/JPL-Caltech

This computer graphic depicts the orbit of comet 2013 A1 (Siding Spring) through the inner solar system. Image credit: NASA/JPL-Caltech

Although the current heliocentric orbit is hyperbolic (i.e., eccentricity greater than one), the orbit is elliptic when expressed in the frame of the solar system’s barycenter. After more than a million year journey, this comet is arriving from our solar system’s distant Oort cloud. It could be complete with the volatile gases that short period comets often lack due to their frequent returns to the sun’s neighborhood.

During the close Mars approach, the comet will likely achieve a total visual magnitude of zero or brighter as seen from Mars-based assets. The attached illustration shows the comet’s approximate, apparent visual magnitude and its solar elongation angle as a function of time as seen from Mars. Because the comet’s apparent magnitude is so uncertain, the brightness curve was cut off at apparent visual magnitude zero. However, the comet may get brighter than magnitude zero as seen from Mars. From Earth, the comet will not likely reach naked eye brightness but it could brighten to visual magnitude 8 as seen from the southern hemisphere in mid-September 2014.

This illustration, prepared by Jon Giorgini, shows the apparent total visual magnitude and solar elongation angle as seen from the center of Mars

This illustration, prepared by Jon Giorgini, shows the apparent total visual magnitude and solar elongation angle as seen from the center of Mars image NASA

Chelyabinsk Meteoroid tracked back to the Apollo asteroid group

February 26, 2013

Astronomers at the University of Antioquia, Medellin in Colombia have back-tracked the trajectory of the Chelyabinsk meteoroid and have concluded that it was from the Apollo asteroid group which regularly intersect with Earth’s orbit. The Apollo group contains at least 5,000 asteroids and more than 240 of these are over 1 km in size. The largest known Apollo asteroid is 1866 Sisyphus, with a diameter of about 10 km.

The Chelyabinsk meteoroid crossed from northeast to southwest on February 15th at an angle of 20 degrees above the horizontal at a speed of about 18 km/s. It is estimated to have been about 17-m in size with an estimated mass of between 7,000 and 10,000 tonnes. It exploded at 03:20:26 GMT over 55° 10′ N, 61° 25′ E at an altitude of 15 to 20 kilometers (9.3 to 12.4 miles) with a force of 500 kilotons – the equivalent of 30 Hiroshima atomic bombs.

The astronomers have published their findings:

A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid

by Jorge I. Zuluaga, Ignacio Ferrin

http://arxiv.org/abs/1302.5377 (abstract)

complete paper (pdf)

Reconstructing the orbit

The Chelyabinsk Meteor Friday 15th Feb. 2013: image from http://www.sott.net

BBC:…. Astronomers have traced the origin of a meteor that injured about 1,000 people after breaking up over central Russia earlier this month.

Using amateur video footage, they were able to plot the meteor’s trajectory through Earth’s atmosphere and then reconstruct its orbit around the Sun. Using the footage and the location of an impact into Lake Chebarkul, Jorge Zuluaga and Ignacio Ferrin, from the University of Antioquia in Medellin were able to use simple trigonometry to calculate the height, speed and position of the rock as it fell to Earth.

To reconstruct the meteor’s original orbit around the Sun, they used six different properties of its trajectory through Earth’s atmosphere. Most of these are related to the point at which the meteor becomes bright enough to cast a noticeable shadow in the videos.

…. The results suggest the meteor belongs to a well known family of space rocks – known as the Apollo asteroids – that cross Earth’s orbit.

Of about 9,700 near-Earth asteroids discovered so far, about 5,200 are thought to be Apollos. Asteroids are divided into different groups such as Apollo, Aten, or Amor, based on the type of orbit they have.

MIT Technology Review: 

“According to our estimations, the Chelyabinski meteor started to brighten up when it was between 32 and 47 km up in the atmosphere,” say Zuluaga and Ferrin, who estimate the velocity at between 13 km/s and 19 km/s relative to Earth.

They then calculated the likely orbit by plugging these figures into a piece of software developed by the US Naval Observatory called NOVAS, the Naval Observatory Vector Astrometry. This allowed them to include the gravitational influence on the rock of the Moon and the 8 major gravitational bodies in the Solar System.

 

Cosmological Principle may not hold

January 13, 2013

A new paper describes the discovery of the largest known Large Quasar Group – with a longest dimension of some 1200 Megaparsecs and a typical dimension of about 500 Mpc. (One parsec is about 3.3 light years). This LQG is thus some 1600 times longer than the distance between the Milky Way Galaxy and the Andromeda Galaxy. The research team – led by Dr Roger Clowes from UCLan’s Jeremiah Horrocks Institute – has identified the LQG which is so significant in size that it also challenges the Cosmological Principle. As Dr. Clowes remarks:

“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.”

And if the Cosmological Principle does not hold it means that the fundamental constants of the known Universe may no longer be so fundamental or so constant.  The list of such constants is long but the most fundamental of these on which we build our understanding of the Universe – which we take as being  immutable – are the speed of light in a vacuum, the gravitational constant and the Planck constant. This opens up the possibility that the physical constants may take different values in different parts of the Universe. They may be a function of space and time. They may change over cosmological time – and of course this could mean that the passage of time itself is not uniform. So perhaps the “arrow of time” is really a “boomerang of time”? Or it could be that what starts out as an arrow may be morphing into a boomerang or something else as time progresses (or not). The concept of time – and not only the passage of time – may vary. What if the trajectory of time could loop on itself? or proceed in the form of a double spiral? Even if the Universe is still a non-static Universe – that itself makes a static Universe – Stasis – possible. The possibilities are legion – and not only for science fiction.

Stardate would no longer be uniform – but this could explain the variation between the different series of Star Trek!

Quasar - atists impression NASA-AFP

Quasar – artists impression NASA-AFP

A structure in the early universe at z ~ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology byRoger G. Clowes, Kathryn A. Harris, Srinivasan Raghunathan, Luis E. Campusano, Ilona K. Soechting, Matthew J. Graham, Monthly Notices of the Royal Astronomical Society, http://arxiv.org/abs/1211.6256

The 2012 Venus transit in 3 minutes

June 6, 2012

A time-lapse video of the transit of Venus on 5th/6th June 2012 as seen by NASA’s  Solar Dynamics Observatory.

From WUWT and reader Mike McMillan.

Visibility of the Venus transit today and tomorrow

June 5, 2012

WARNING!

Direct viewing of the Sun with the naked eye or through open telescopes or binoculars should be avoided. Indirect observation of a projected image is advised.

Transit times

Venus transit 5th-6th June 2012: image BBC

BBC: Venus transits occur four times in approximately 243 years; more precisely, they appear in pairs of events separated by about eight years and these pairs are separated by about 105 or 121 years. The reason for the long intervals lies in the fact that the orbits of Venus and Earth do not lie in the same plane and a transit can only occur if both planets and the Sun are situated exactly on one line.

This has happened only seven times in the telescopic age: in 1631, 1639, 1761, 1769, 1874, 1882 and 2004. Once the latest transit has passed, the next pair will not occur until 2117 and 2125. Most people alive today will probably be dead by then.

Supermoon today and a chance to observe the moon illusion

May 5, 2012

“supermoon” is the coincidence of a full moon (or a new moon) with the closest approach the Moon makes to the Earth on its elliptical orbit, or perigee, leading to the technical name for a supermoon of the perigee-syzygy of the Earth-Moon-Sun system. The association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events such as earthquakes and volcanic eruptions. However, the evidence of such a link is widely held to be unconvincing.

A supermoon will occur today, Saturday 5th May.

A “supermoon” typically happens once a year and at perigee it is 14 per cent larger than an average full moon, but not much larger than the full moons that precede and follow the supermoon. The closeness of the supermooon does cause higher tides but only about 2 or 3 cms higher than average levels.

Moon Illusion

The moon illusion refers to the moon seeming larger when it is near the horizon than when it is high in the sky. Some people judge it to be as much as twice as large, but the average estimate is 50% to 75% larger. But this is only an optical illusion.

Physical and cognitive explanations do not yet explain the illusion or why some people cannot observe it. The debate goes on.

The so-called “moon illusion” or “moon effect” has perplexed people since earliest historical times, at least as early as the 7th century BCE. It is described in early Greek and Chinese writings. Aristotle mentions it in 350 BCE.

No tidal waves or other catastrophic effects are expected.


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