Posts Tagged ‘Astronomy’

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.

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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.

 

Habitable exoplanet Gleise 581g may not exist

October 13, 2010

 

Artist's impression of the planetary system ar...

Gleise 581 system: Image via Wikipedia

 

An earlier post reported on the finding of a potentially habitable exoplanet.

But the planet may not exist:

Yesterday at an exoplanet meeting in Turin, Italy, Switzerland-based astronomers announced that they could find no trace of the prized planet in their observations of the same planetary system.

All the excitement has been over the subtlest of wiggles in the motion of the star Gliese 581 that lies just 20 light-years from the sun in the direction of the constellation Libra. A consortium of institutions led by the Observatory of Geneva in Switzerland had already discovered four planets circling Gliese 581 by sorting out the subtle motions of the star that are induced by the gravitational tugs of any orbiting planets.

On 29 September, a U.S.-based team led by astronomer Steven Vogt of the University of California, Santa Cruz, announced that it had discovered a fifth planet. The American team used a combined set of observations: One 11-year-long set consisted of 122 measurements made by the team, while the other set was 4.3 years long and consisted of 119 measurements published by the consortium.

Designated Gliese 581g, the new planet has at least three times the mass of Earth—large enough to hold on to a watery atmosphere—and orbits at a distance from its star that would allow any water to remain liquid. That would make 581g a happy home for life as we know it.

But at this week’s Astrophysics of Planetary Systems meeting, astronomer Francesco Pepe of the Geneva Observatory and the Swiss group reported that he and his colleagues could find no reliable sign of a fifth planet in Gliese 581’s habitable zone. They used only their own observations, but they expanded their published data set from what the U.S. group included in its analysis to a length of 6.5 years and 180 measurements. “We do not see any evidence for a fifth planet … as announced by Vogt et al.,” Pepe wrote Science in an e-mail from the meeting. On the other hand, “we can’t prove there is no fifth planet.” No one yet has the required precision in their observations to prove the absence of such a small exoplanet, he notes.

“Gliese 581g”: Habitable planet found?

September 30, 2010
Habitable zone-he

Image via Wikipedia: Habitable zone

From just a week ago “Two researchers have used the pace of past exoplanet finds to predict that the first habitable Earth-like planet could turn up in May 2011″.

A pessimistic forecast perhaps because astronomers may have found the most Earth-like alien planet to date, and it’s located only a short distance away, cosmically speaking. The team says that the planet’s proximity to its sun, coupled with the ease with which it was detected, suggests that the galaxy could be teeming with habitable worlds.

Science reports that:

Gliese 581g looks like a game-changer. Detected from the minuscule amount of gravitational influence it exerts on its star, the planet lives a mere 20 light-years away in the constellation Libra. Gliese 581g is the sixth world discovered around its sun—and the fourth most distant. Yet its orbit brings it closer to its parent star than Mercury is to our sun. Still, it’s squarely within the habitable zone, because the planet’s star, which is a type known as a red dwarf, contains only about 30% of the sun’s mass and shines with only about 1% of its brightness, the researchers will report in an upcoming issue of the Astrophysical Journal.

Read the article:

http://news.sciencemag.org/sciencenow/2010/09/astronomers-find-most-earth-like.html

Habitable planet to be discovered in May 2011?

September 22, 2010

The only thing certain about forecasts is that they are more often wrong than right – and I exclude forecasts made entirely on known science or “laws” of nature where the level of uncertainty is insignificant (e.g. the sun will rise tomorrow). Nevertheless “Future History” which is a study of how forecasts evolve and how accurate they have been is a most powerful tool when making judgements about directions to follow and actions to be taken. In management “Future History” methodology is, I think, one of the most powerful tools for the development of corporate strategies and action plans.

The New Scientist reports that :

“Two researchers have used the pace of past exoplanet finds to predict that the first habitable Earth-like planet could turn up in May 2011”.

In 1965, Intel co-founder Gordon Moore observed that the number of transistors that fit on a chip doubles about once every two years – a trend now known as Moore’s law. Samuel Arbesman of Harvard Medical School in Boston wants to see if scientometrics – the statistical study of science itself – can similarly be used to not only study past progress but also to make predictions.

He and Greg Laughlin of the University of California, Santa Cruz, are testing the idea with exoplanets. Over the past 15 years or so, the pace of planet discoveries has been accelerating, with some 490 planets now known. “It is actually somewhat similar to Moore’s law of exponential growth,” Arbesman says.

To predict when astronomers might find the first planet similar in size to Earth that also orbits far enough from its star to boast liquid water, the team scoured the discovery records of 370 exoplanets.

They focused on two basic properties needed for habitability: a planet’s mass and its surface temperature. They used these two factors to assign each planet a ‘habitability metric’ ranging from 0 to 1, where 0 was uninhabitable and 1 is close to Earth’s twin.

A rough estimate of each planet’s habitability was then plotted against the date of its discovery. Using different subsets of the 370 planets, the researchers made curves from the individual points and extrapolated the curves to find when a planet would be found with a habitability of 1. They then analysed the range of discovery dates to determine which would be most probable.

Habitable planets: http://t2.gstatic.com/images

Their calculations suggest there is a 50 per cent chance that the first habitable exo-Earth will be found by May 2011, a 75 per cent chance it will be found by 2020, and a 95 per cent chance it will be found by 2264.

In fact, exoplanet researchers have made forecasts of the future informally, plotting the mass of planets against the date of discovery to see how the field is progressing. “We’ve done that for many years at conferences,” says Eric Ford of the University of Florida in Gainesville. “The new aspect of this paper is putting an uncertainty on those predictions and unfortunately the uncertainty is quite large.”

One source of uncertainty is how factors like changes in funding and the development of new techniques and technology can alter the pace of discovery. “Like the stock market, past returns are no guarantee of future performance,” Ford says.

“There are always these complex factors of how science is actually done,” Arbesman agrees. But he says the forecasting technique could still prove useful, even if these factors are not accounted for directly. In part, that is because new technologies tend to take a while to ramp up, so they may not lead to sharp jumps in the number of discoveries made.

Previously, Arbesman has quantified how the ease of discovering new mammalian species, chemical elements, and asteroids affects the rate of their discovery. New species and asteroids are more difficult to find the smaller they are, and indeed larger ones are found first. For chemical elements, the opposite is true, since the bigger they are, the rarer and more unstable they tend to be.


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