MILANKOVITCH CYCLES AND GLACIATION

Milankovitch Cycles and Glaciation

The episodic nature of the Earth’s glacial and interglacial periods within the present Ice Age (the last couple of million years) have been caused primarily by cyclical changes in the Earth’s circumnavigation of the Sun. Variations in the Earth’s eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles for Milutin Milankovitch, the Serbian astronomer and mathematician who is generally credited with calculating their magnitude. Taken in unison, variations in these three cycles creates alterations in the seasonality of solar radiation reaching the Earth’s surface. These times of increased or decreased solar radiation directly influence the Earth’s climate system, thus impacting the advance and retreat of Earth’s glaciers.

It is of primary importance to explain that climate change, and subsequent periods of glaciation, resulting from the following three variables is not due to the total amount of solar energy reaching Earth. The three Milankovitch Cycles impact the seasonality and location of solar energy around the Earth, thus impacting contrasts between the seasons.

Eccentricity

The first of the three Milankovitch Cycles is the Earth’s eccentricity. Eccentricity is, simply, the shape of the Earth’s orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years. These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun’s short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth’s surface in different seasons.

Today a difference of only about 3 percent occurs between aphelion (farthest point) and perihelion (closest point). This 3 percent difference in distance means that Earth experiences a 6 percent increase in received solar energy in January than in July. This 6 percent range of variability is not always the case, however. When the Earth’s orbit is most elliptical the amount of solar energy received at the perihelion would be in the range of 20 to 30 percent more than at aphelion. Most certainly these continually altering amounts of received solar energy around the globe result in prominent changes in the Earth’s climate and glacial regimes. At present the orbital eccentricity is nearly at the minimum of its cycle.

Axial Tilt

Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth’s axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth’s axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees.

Today the Earth’s axial tilt is about 23.5 degrees, which largely accounts for our seasons. Because of the periodic variations of this angle the severity of the Earth’s seasons changes. With less axial tilt the Sun’s solar radiation is more evenly distributed between winter and summer. However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.

One hypothesis for Earth’s reaction to a smaller degree of axial tilt is that it would promote the growth of ice sheets. This response would be due to a warmer winter, in which warmer air would be able to hold more moisture, and subsequently produce a greater amount of snowfall. In addition, summer temperatures would be cooler, resulting in less melting of the winter’s accumulation. At present, axial tilt is in the middle of its range.

Precession

The third and final of the Milankovitch Cycles is Earth’s precession. Precession is the Earth’s slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of 23,000 years.

Due to this wobble a climatically significant alteration must take place. When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively. This means that the Northern Hemisphere will experience winter when the Earth is furthest from the Sun and summer when the Earth is closest to the Sun. This coincidence will result in greater seasonal contrasts. At present, the Earth is at perihelion very close to the winter solstice.

CHARTING MILKY WAY

Charting the Milky Way from the inside out

Using WISE, researchers have discovered more than 400 dust-shrouded nurseries of stars that have helped them trace the shape of our galaxy’s spiral arms.
By NASA  |  Published: Friday, June 05, 2015
RELATED TOPICS: MILKY WAY | SPIRAL GALAXIES
Shape of Milky Way Galaxy
This artist’s concept depicts the most up-to-date information about the shape of our own Milky Way Galaxy. We live around a star, our Sun, located about two-thirds of the way out from the center.
NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
Imagine trying to create a map of your house while confined to only the living room. You might peek through the doors into other rooms or look for light spilling in through the windows. But, in the end, the walls and lack of visibility would largely prevent you from seeing the big picture.

The job of mapping our Milky Way Galaxy from planet Earth, situated about two-thirds of the way out from the galaxy’s center, is similarly difficult. Clouds of dust permeate the Milky Way, blocking our view of the galaxy’s stars. Today, researchers have a suitable map of our galaxy’s spiral structure, but, like early explorers charting new territory, they continue to patiently and meticulously fill in the blanks.

Recently, researchers have turned to a new mapping method that takes advantage of data from NASA’s Wide-field Infrared Survey Explorer (WISE). Using WISE, the research team has discovered more than 400 dust-shrouded nurseries of stars, which trace the shape of our galaxy’s spiral arms. Seven of these “embedded star clusters” are described in a new study.

“The Sun’s location within the dust-obscured galactic disk is a complicating factor to observe the galactic structure,” said Denilso Camargo from the Federal University of Rio Grande do Sul in Brazil.

The results support the four-arm model of our galaxy’s spiral structure. For the last few years, various methods of charting the Milky Way have largely led to a picture of four spiral arms. The arms are where most stars in the galaxy are born. They are stuffed with gas and dust, the ingredients of stars. Two of the arms, called Perseus and Scutum-Centaurus, seem to be more prominent and jam-packed with stars, while the Sagittarius and Outer arms have as much gas as the other two arms but not as many stars.

Astronomers using data from NASA’s Wide-field Infrared Survey Explorer (WISE) are helping to trace the shape of our Milky Way Galaxy’s spiral arms. This illustration shows where WISE data revealed clusters of young stars shrouded in dust, called embedded clusters, which are known to reside in spiral arms.
The new WISE study finds embedded star clusters in the Perseus, Sagittarius, and Outer arms. Data from the Two Micron All Sky Survey (2MASS), a ground-based predecessor of WISE from NASA, the National Science Foundation, and the University of Massachusetts, Amherst, helped narrow down the distances to the clusters and pinpoint their location.
milky way
Embedded star clusters are a powerful tool for visualizing the whereabouts of spiral arms because the clusters are young and their stars haven’t yet drifted away and out of the arms. Stars begin their lives in the dense gas-rich neighborhoods of spiral arms, but they migrate away over time. These embedded star clusters complement other techniques for mapping our galaxy, such as those used by radio telescopes, which detect the dense gas clouds in spiral arms.

“Spiral arms are like traffic jams in that the gas and stars crowd together and move more slowly in the arms. As material passes through the dense spiral arms, it is compressed and this triggers more star formation,” said Camargo.

WISE is ideal for finding the embedded star clusters because its infrared vision can cut through the dust that fills the galaxy and shrouds the clusters. What’s more, WISE scanned the whole sky, so it was able to perform a thorough survey of the shape of our Milky Way. NASA’s Spitzer Space Telescope also uses infrared images to map the Milky Way’s territory. Spitzer looks along specific lines of sight and counts stars. The spiral arms will have the densest star populations.

 

MilkyWay

EVREN’IN BOYUTLARI

 

Evren Gerçekten Ne Kadar Büyük? 

 

Gezegenlerden galaksilere bilinen evrenin 30 harikası

 

Evren’de mesafelerin astronomik olduğunu söylersek abartmış olmayız. 

Ancak bilinen evrenin en ilginç yanlarından biri bazı galaksilerin bizden milyarlarca ışık yılı uzakta olması değil. 

Asıl ilginç yanı, Evren’de büyüklüklerin göreli olması.

Örneğin Güneş Sistemi’nin çapı nedir? 

Bu soruyu “Neye göre?” sorusunu eklemeden cevaplamak imkansız. 

Çünkü Güneş Sistemi’nin 4 farklı boyu var ve büyüklüğü de hangi kriteri baz aldığınıza göre değişiyor.

Evren’in 30 harikasını anlatan yazımızın sonunda bu sorunun da yanıtını bulacaksınız.

Öte yandan, Evren’deki en büyük gökcisimleri aynı zamanda Evren’deki en kütleli cisimler olmak zorunda değil. 

Nitekim bazı galaksilerin merkezindeki süper kütleli kara delikler bilinen en büyük yıldızların yanında ufak kalıyor.

Ayrıca Evren’in en parlak yıldızları aynı zamanda en büyük yıldızları olmak zorunda değil.

İşte Evren’in 30 harikasını anlatan yeni yazımızda cüce gezegenlerden kara deliklere

ve Dünya’dan uzak galaksilere uzanarak bu tür sıra dışı sorulara cevap arıyoruz. 

Siz de bu Pazar farklı bir şey yapın ve Evren’in harikaları arasından size en ilginç geleni seçin.

 

1. Burası Dünya!

Burada yaşıyoruz.

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2. Burası da Güneş Sistemi ve kırmızı oklar

Dünya’nın konumunu gösteriyor.

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3. Resimde Dünya-Ay uzaklığını gerçek ölçekli olarak görüyorsunuz.

Yakın görünüyor değil mi?

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4. Hiç de değil:

Dünya-Ay arasına Güneş Sistemi’ndeki bütün gezegenleri sığdırabilirsiniz (Jüpiter dahil)!

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5. Jüpiter’in büyüklüğü dedik de Jüpiter’in

Büyük Kırmızı Lekesinin güneyindeki şu küçük yeşil benek var ya,

ha işte o Kuzey Amerika.

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6. Satürn, Jüpiter’den sonra Güneş Sistemi’ndeki en büyük gezegen.

Bakın Satürn’ün halkalarına yan yana kaç Dünya sığıyor. :)

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7. Dünya’nın Satürn gibi halkaları olsaydı (aynı büyüklükte)

yerden işte böyle görünürdü.

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8. Rosetta uzay sondası geçen yıl 67/p kuyrukluyıldızına Filai sondasını indirdi.

İşte o kuyrukluyıldızla Los Angeles’ın karşılaştırması.

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9. Oysa Güneş,

Güneş Sistemi’ndeki en büyük gökcismi ve bu mahallede kimse Güneş’in yanına yaklaşamaz.

Güneş’in çapı Dünya’nın 109 katı ve yaklaşık 1 milyon 400 km.

Yüzölçümü ise Dünya’nın 12 bin katı.

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10. Ay’dan Dünya’nın görünümü (gündoğumu değil de yerdoğumu diyebilirsiniz).

Çocuklarınız Ay’a yerleşirse hem Güneş’in hem Dünya’nın doğuşunu izleyecekler.

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11. Mars’tan Dünya’nın görünümü.

Yaklaşık 78 milyon km uzaktan küçük bir nokta.

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12. Satürn’ün halkalarının arkasından Dünya’nın görünümü

(resmin altındaki beyaz ok ve mavi nokta).

Dünya resimde 1 milyar 284 milyon km uzakta.

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13. Cüce gezegen Plüton’dan bakınca Güneş (5,8 milyar km uzakta).

Bu temsili resim ama oranlar doğru.

Ancak ne kadar küçük olsa da Güneş,

Plüton göğünde dolunaydan 450 kat parlaktır.

p3ukhnpdav8d4pwflmir

14. Bu arada standart güneş püskürmeleriyle

(uzaya fırlayan sıcak gazlar)

Dünya’yı karşılaştıralım.

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15. Güneş’e bir de Mars’tan bakalım mı?

228 milyon km uzakta.

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16. Uzaydaki yıldızları nispeten yakından ve uzaktan gösteren şu iki resme bakın.

Carl Sagan, Evren’deki yıldızların sayısı kum tanelerinden fazla demişti.

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17. Dünya ile karşılaştırınca dev gibi görünen

Güneş’in aslında küçük bir sarı cüce olduğunu biliyor muydunuz?

Örneğin VY Canis Majoris bilinen Evren’in en büyük yıldızı ve çapı Güneş’in 1440 katı.

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18. Çapını söyledik ama hacim olarak VY Canis Majoris Güneş’ten 1 milyar kat büyük,

yani içine 1 milyar Güneş sığar.

Şöyle söyleyelim,

Samanyolu Galaksisi’nde irili ufaklı 100 milyar ila 400 milyar yıldız var.

Güneş’le karşılaştırmak için videoyu tıklayın:

19. Elbette bütün bunlar yüzlerce milyar yıldız barındıran galaksimizle karşılaştırılamaz. Galaksimizin büyüklüğünü bir örnek vererek gösterelim:

Güneş’i alyuvar boyuna indirgeseydik (kırmızı kan hücreleri)

Samanyolu Galaksisi ABD kadar büyük olurdu.

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20. Bu arada Dünya’nın Samanyolu’ndaki konumunu da gösterelim (temsili).

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21. Bu da kuşbakışı görünüşü.

Samanyolu’nun merkezine yaklaşık 30 bin ışık yılı uzaktayız.

  9.460.800.000.000 X 30.000.000 = ?

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22. Öte yandan Samanyolu da diğer galaksilerin yanında cüce kalıyor.

Örneğin 1,04 milyar ışık yılı uzaktaki IC 1011 ile karşılaştırırsak.

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23. Büyük düşünelim.

Bu resim Hubble uzay teleskopu tarafından çekildi ve içinde binlerce galaksi var.

Evet, o noktaların çoğu yıldız değil,

her biri yüz milyarlarca yıldız içeren birer galaksi.

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24. Evren’deki uzaklıklar gerçekten astronomik.

Bu da UDF 423 galaksisi. Galaksinin ışığı bize 7,7 milyar yılda ulaştı,

ama Evren’in genişlemesi yüzünden bu galaksi bize şu anda 10 milyar ışık yılı uzakta.

Işık hızının sınırlı olması yüzünden Evren’de uzaklara bakmak,

aslında geçmişe bakmak demek.

Örneğin o mesafede Evren’in 5,9 milyar yaşındaki halini görüyoruz, bugünkü halini değil.

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25. Bu arada 23 numaradaki binlerce galaksiyi içeren resmi hatırladınız mı?

O resim aslında gece göğünün küçücük bir parçası!

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26. Bir de süper kütleli kara delikler var.

Bunlar galaksilerin merkezinde bulunuyor ve her biri Güneş Sistemi kadar büyük.

Resimdeki NGC 1277 galaksisinin merkezindeki dev kara delik.

Mavi halkanın genişliği 9 milyar km (Neptün’ün yörüngesi).

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27. Evren’de en önemli şey büyüklük değil.

Örneğin bu gördüğünüz sadece 12 km çapındaki süper yoğun bir nötron yıldızı.

Boyu küçük ama o kadarcık hacme 3 Güneş kitlesi sıkışmış.

Resimde New York’un üzerinde.

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28. Gerçi bu küçük şey Dünya’ya Ay kadar yaklaşsaydı

güçlü yerçekimi ile gezegenimizi parçalayıp yutardı.

Bu arada resimdeki sarılar aslında milyon derece sıcaklığındaki

gaz akımları ve atom bombası gibi X-ışınları yayıyor,

yani aktif nötron yıldızı ışığı altında güneşlenmeyin olur mu?

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29. Bu da Evren’in ne kadar büyük olduğunu gösteren bir bilgisayar simülasyonu.

Resmin genişliği 350 milyon ışık yılı ve resimdeki küçük noktalar yıldız değil.

Bunların her biri büyük birer galaksi ve büyük sarı

yuvarlakların içinde de binlerce galaksi var.

Evet,

Evren’e uzaydan bakınca galaksilerin uzayı örümcek ağı gibi sardığını görüyoruz.

30. Oort Bulutu: Güneş Sistemi’nin gerçek sınırı.

Oort Bulutu Güneş’in kütleçekim alanının gökcisimlerini

Güneş’e doğru çektiği son nokta ve Güneş’i uzaktan küre şeklinde saran trilyonlarca kuyrukluyıldızdan oluşuyor.

Voyager 1 sondası Oort Bulutu’na 300 yıl sonra girecek ve buluttan çıkması 7000 yıl alacak.

Bu açıdan da Güneş Sistemi’ni daha terk etmedi sayılır.

Gerçekten de Güneş Sistemi’ni ışık hızına yaklaşmadan makul sürede terk etmek imkansız.

Oort Bulutu’nun dış sınırı 2 ışık yılı uzakta (belki 3,25 ışık yılı).

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Bonus:

Uzaydaki yerimizi daha iyi anlamak için resimdeki

Ooort Bulutu’nun eşliğinde Güneş Sistemi’yle ilgili şu büyüklükleri verelim:

İstanbul’un genişliği: 150 km

Türkiye’nin genişliği: 1660 km

Dünya’nın çapı: ~12 bin km

Ay’ın uzaklığı: Ortalama 384 bin km

Dünya’nın Güneş’e uzaklığı: ~150 milyon km (1 astronomik birim – AU)

Gezegenlere göre Güneş Sistemi’nin çapı: 9,09 milyar km

Güneş rüzgarının sırınıa göre Güneş Sistemi’nin çapı: 180 milyar km (Voyager 1 sondası burada)

Güneş’e en uzak cüce gezegen Sedna’ya göre Güneş Sistemi’nin çapı: 287,46 milyar km

Oort Bulutu’na göre Güneş Sistemi’nin çapı: 15 trilyon km, 100 bin AU, yani 2 ışık yılı!

Bize en yakın yıldızın uzaklığı: 4,3 ışık yılı.

Samanyolu Galaksisi’nin çapı: 150 bin ışık yılı

En yakın galaksi Andromeda: 2,2 milyon ışık yılı uzakta.

Evren’de bilinen en büyük yapının uzunluğu:

600 milyon ışık yılı.

Gözlemlenebilir Evren’in çapı:

93 milyar ışık yılı

(yani teorik olarak görebileceğimiz en uzak galaksi yaklaşık 47 milyar ışık yılı uzakta).

**

Işık hızı, ışığın ve tüm diğer elektromanyetik dalgaların boşluktaki hızı olup 299.792.458 metre/saniyedir (yaklaşık 1.079.252.850 km/saat). Daha kolay hatırlamak için  kitaplarda genellikle 300.000 kilometre/saniye şeklinde ifade edilir. 

Işığın hızı saatte 1.080.000.000 km/saat, günde 26.000.000.000 km/gün,

yılda ise 9.460.800.000.000 km/yıl

olarak verilebilir.

 

 

GRAVITATIONAL WAVES

Riding Gravity Waves to the Big Bang and Beyond

Once again, Einstein’s theory of relativity is confirmed by scientists. Next stop: Creation.

The Laser Interferometer Gravitational-wave Observatory near Livingston, La. ENLARGE
The Laser Interferometer Gravitational-wave Observatory near Livingston, La. PHOTO: REUTERS
By

MICHIO KAKU

Feb. 12, 2016 6:16 p.m. ET

Champagne bottles were uncorked in physics labs around the world this week when a team of scientists announced they had finally achieved a long cherished dream, detecting the elusive gravity waves predicted by Albert Einstein 100 years ago. This remarkable discovery, which confirmed the last major prediction of Einstein’s theory of general relativity and opens up a whole new way to explore the universe, will almost certainly merit a Nobel Prize in Physics.

In 1916 Einstein himself didn’t believe these faint gravity waves could be detected in his lifetime. A century later, the devices that finally detected them are so enormous that they can be seen from outer space. The two Laser Interferometer Gravitational-wave Observatories, or LIGO detectors, one in Washington state and the other in Louisiana, operate like massive horizontal antennas allowing scientists to detect the gravitational waves.

On Thursday, in an article in Physical Review Letters with more than 1,000 authors, the LIGO scientists revealed that on Sept. 14 they had detected the collision of two black holes in deep space more than a billion light years away but it then took five months to analyze and confirm the results. The black holes were about 36 and 29 times the mass of the sun, and the colossal shock wave caused by their merging into an even larger black hole sent violent ripples of gravity hurling throughout the universe.

Each LIGO detector consists of two pipes, each 2.5 miles long, creating the shape of an L. Each pipe contains a laser beam of light bouncing between perfectly positioned mirrors. If a gravity wave from outer space hits the L, it causes a tiny disturbance, which is then measured by analyzing how the two laser beams interact. As an added treat, the LIGO scientists have converted the gravity waves they detected to sound waves so one can hear the ripples in space-time that Einstein predicted.

All this has once again confirmed Einstein’s theory of general relativity, which he developed almost entirely on his own between 1907 and 1915. Einstein’s great insight was to realize that space-time is not empty, but more like a fabric that can bend and stretch and cause the path of objects to bend, giving us the illusion of gravitational force. But if the fabric of space-time can stretch, thought Einstein, why can’t it also create ripples?

Think of throwing a rock in a pond. Ripples will gradually radiate away from the splash and fill the surface of the pond. This is similar to what the LIGO scientists detected for the first time: Gravity waves rippling outward from the collision of two black holes a billion light years away.

The LIGO discovery also answers a question commonly asked about the sun. Many people have asked a deceptively simple question: If the sun were to suddenly disappear at this instant, how long would it take for us to notice? Newton thought gravity acted instantaneously, so the earth would instantly be hurled into space.

Einstein thought otherwise. If space is a fabric, then shock waves traveling along this fabric should take eight minutes to reach the earth, traveling at the speed of light. The LIGO breakthrough confirms Einstein’s hypothesis, and has profound cosmological implications. The next generation of gravity-wave detectors might be put into space, and might eventually be sensitive enough to detect the most revealing radiation of all, the radiation from the instant of Genesis. One can calculate that the next generation of space-based gravity wave detectors might eventually be sufficiently sensitive to detect gravity shock waves from the big bang.

If true this, in turn, would open up an entirely new chapter in astronomy. Each time a new wave was discovered, it changed human history. When Galileo used light waves to create his telescope four centuries ago, it profoundly altered our view of the universe and even shook the Catholic Church. Then, around the time of World War II, radio waves were harnessed to create radio telescopes capable of detecting quasars, colliding galaxies and even black holes.

Now we are witnessing the third great revolution in telescopes, the use of gravity waves to open a new chapter in astronomy. For the first time, waves from the very instant of creation might be observed, giving us “baby pictures” of the universe as it was born. High-school textbooks may have to be rewritten to incorporate the new discoveries coming from this third generation of telescopes.

This may also have philosophical implications. Right now the big-bang theory doesn’t tell us what banged, why it banged, and what caused it to bang. It only tells us that there was a bang. But if space-based gravity-wave detectors similar to LIGO’s detectors can measure the radiation emitted an instant after the big bang, then, using mathematics, one can run the equations backward to determine what set off the big bang in the first place, in effect answering the biggest question of all: What banged and why?

When Einstein postulated gravity waves a century ago, he not only opened up an entirely new chapter in astronomy, he also opened the door to answering the most important philosophical questions of all time, including the creation of the universe.

Mr. Kaku is a professor of theoretical physics at the City College of New York and the author of “The Future of the Mind: The Scientific Quest to Understand, Enhance, and Empower the Mind” (Doubleday, 2014).

TERRY HANCOCK’S “GAMMA CYGNI REGION MOSAIC”

TERRY

Gamma Cygni Region 6 Panel Mosaic

All data from this project has been acquired from my amateur backyard observatory in Fremont, Michigan during the last 2 seasons using a QHY11 Monochrome CCD/Takahashi E-180 with narrowband filters.

167 single images make up this 6 panel Mosaic of The Gamma Cygni Region in Hubble Pallete which is now covering 7.17 x 6.91 degrees of sky, original file size is 6998×6480 pixels. Total Integration Time 27.8 hours

Image details
Location: DownUnder Observatory, Fremont MI
Dates of Shoot: March 2014 through to July 2015 over 11 nights
H-Alpha 590 min, 59 x 10 min bin 1×1
OIII 540 min,54 x 10 min 1×1
SII 540 min, 54 x 10 min 1×1

Equipment
QHY11S monochrome CCD cooled to -20C
Takahashi E-180 F2.8 Astrograph
Paramount GT-1100S German Equatorial Mount
Image Acquisition Maxim DL
Stacking and Calibrating: CCDStack
Registration of images in CCDStack & Registar
Post Processing Photoshop CS5

The Gamma Cygni/Sadr Region, named after the central star Sadr/Gamma Cygni the central star of Cygnus’s Cross surrounded by diffuse emission and dark nebulae and part of the much larger Cygnus Molecular Cloud.