Hari Lahir Jagat Raya (How Old Our Universe? )
By:
Arip Nurahman
Department of Physics
Faculty of Sciences and Mathematics, Indonesia University of Education
and
Follower Open Course Ware at Massachusetts Institute of Technology
Cambridge, USA
Department of Physics
http://web.mit.edu/physics/
http://ocw.mit.edu/OcwWeb/Physics/index.htm
&
Aeronautics and Astronautics Engineering
http://web.mit.edu/aeroastro/www/
http://ocw.mit.edu/OcwWeb/Aeronautics-and-Astronautics/index.htm
Arip Nurahman
Department of Physics
Faculty of Sciences and Mathematics, Indonesia University of Education
and
Follower Open Course Ware at Massachusetts Institute of Technology
Cambridge, USA
Department of Physics
http://web.mit.edu/physics/
http://ocw.mit.edu/OcwWeb/Physics/index.htm
&
Aeronautics and Astronautics Engineering
http://web.mit.edu/aeroastro/www/
http://ocw.mit.edu/OcwWeb/Aeronautics-and-Astronautics/index.htm
"Ketika riwayat sang kala ditentukan maka terpancarlah cahaya penciptaan menerobos ruang berdimensi 0 tercabik oleh kekuatan tunggal yang menggenggam Alam Raya, telah lahir suatu sonata kehidupan yang akan diarungi oleh berbagai karya agung Sang Pencipta."
-(H2O)-
Introduction-(H2O)-
Ada pertanyaan yang sangat 'menggoda' tentang alam semesta, yaitu: berapa usia jagat raya saat ini.? Menggoda karena jawaban pertanyaan ini tidak mudah, padahal pertanyaan ini telah ada sejak menusia ada. Kalaupun ada jawaban, tentu akan bertentangan dengan jawaban yang telah tersedia pada Kitab-Kitab Suci, tapi kalaulah kita tahu hari kapan, jam berapa, dimana? Kita pasti bisa memperingati hari kelahirannya yang agung, dan mengucap segenap rasa kasih kepada Sang Arsitek ulung Jagat Raya.
Namun, ada baiknya kita berjalan pada ilmu pengetahuan saja karena ini memang telaah kita. Perbedaan jawaban ilmu pengetahuan dengan jawaban agama marilah kita pandang sebagai salah satu bukti bahwa jagat raya ini masih berproses. Dalam berproses inilah terjadi perbedaan-perbedaan yang makin lama makin sedikit hingga pada suatu saat kelak tidak ada lagi perbedaan antara jawaban ilmu pengetahuan dan jawaban agama. Jawaban ilmu pengetahuan dan jawaban agama sama-sama menunjukkan suatu kebenaran. Kebenaran itu berasal dari Yang Mahabenar. Yang Mahabenar hanya satu. "The One and Only"
Contents
Contents
Kembali ke pertanyaan semula, yakni: berapa usia jagat raya saat ini?. Banyak cara yang dapat ditempuh para ahli untuk menjawab pertanyaan ini. Pada umumnya dapat dikelompokkan menjadi dua jenis, secara kimiawi dan secara fisik. Secara kimiawi pada umumnya didasarkan sifat-sifat radioaktivitas. Unsur radioaktif akan meluruh menjadi unsur lain. Dengan cara menghitung bagian yang telah meluruh dapat diperkirakan waktu yang diperlukan untuk meluruh semua. Unsur-unsur tertua pada batuan bumi, meteor atau benda-benda langit lainnya diamati. Secara umum diperoleh umur alam semesta ini berkisar antara 11-20 milyar tahun. Pengukuran-pengukuran paling sering menghasilkan nilai untara 13-15 milyar tahun.
Dengan menggunakan alat yang disebut spektrometer berkas cahaya dapat diuraikan menjadi seperti pelangi yang menyebar dari warna merah hingga warna biru/ungu. Spektrum-spektrum yang dihasilkan dari cahaya bintang di langit ini oleh para ilmuwan diperlakukan sebagai semacam sidik jari bintang. Karena, tiap bintang mengahsilkan spektrum yang khas.
Berdasarkan prinsip efek Doppler, pergeseran posisi spektrum dari seberkas cahaya yang dipancarkan oleh sebuah bintang digunakan untuk memperkirakan arah gerak dan kecepatannya saat itu. Jika spektrum yang terjadi bergeser mendekati warna merah maka bitang tersebut bergerak menjauhi bumi dan sebaliknya jika bergeser ke arah biru, bintang yang bersangkutan sedang mendekati bumi.
Pergeseran posisi spektrum ini mencerminkan pergeseran frekuensi dan tentunya pergeseran panjang gelombang dari posisi yang baku. Fraksi selisih panjang gelombang yang tergeser dan panjang gelombang yang baku menyatakan perbandingan kecepatannya relatif terhadap kecepatan cahaya. Fraksi ini digunakan untuk menetapkan kecepatan gerak bintang relatif terhadap tata surya kita, berarti juga relatif terhadap bumi.
Dengan perkakas yang lain, misalnya paralax, kita dapat memperkiran jarak bintang terhadap kita. Jarak itu, karena sangat panjang maka dinyatakan dalam tahun cahaya. Satu tahun cahaya adalah jarak yang ditempuh oleh seberkas cahaya setelah merambat selama satu tahun. Satu tahun cahaya itu sama dengan 9,5 x 10 pangkat 15 meter.
Dengan mengukur kecepatan gerak relatif terhadap tata surya kita dan jaraknya terhadap tata surya kita beberapa bintang dapatlah diperkirakan usia alam semesta ini. Lihat Gambar utama. Titik-titik itu merupakan representasi beberapa bintang yang diamati. Usia alam semesta ditetapkan sebagai berikut. Kita tarik sepenggal garis lurus vertikal ke atas melalui titik 1.0 pada sumbu X (kecepatan bintang) hingga memotong garis lurus (g) yang melewati titik-titik representasi bintang-bintang. Kemudian ditarik penggal garis lurus mendatar ke kiri hingga memotong sumbu Y (Jarak bintang). Titik potong itu menunjukkan usia alam semesta. Sekitar 16 milyar tahun.
Mencermati umur alam semesta yang telah mencapai puluhan milyar tahun itu, maka terasa bahwa umur kita (rata-rata sekitar 60 tahun) sangat pendek sekali. Apa lagi kalau kita bandingkan dengan waktu hidup yang abadi. Kita sangatlah kecil. Umur kita sangatlah pendek. Namun demikian, betapa pun pendeknya usia kita, kita sebagai manusia seorang demi seorang tetap unik. Tidak ada duanya di dunia ini. Karena itu, tentu Sang Pemilik Alam Semesta mempunyai penugasan khusus bagi kita masing-masing. Sudahkah Anda mempunyai jawaban tentang apa tugas Anda di dunia ini? Silahkan mencarinya di antara bintang-bintang di angkasa raya. Di sana ada jawabnya. Semoga berhasil!.
"Kalaulah hari ini hari lahir jagat raya dimana sang kala mulai berdetak maka selamat dan selamat (Happy Brith Universe)semoga keindahan alam semesta selalu terpacar ke segala arah penjuru Cosmos."
English Version
The age of the Universe has been a subject of religious, mythological and scientific importance. On the scientific side, Sir Isaac Newton's guess for the age of the Universe was only a few thousand years. Einstein, the developer of the General Theory of Relativity, preferred to believe that the Universe was ageless and eternal. However, in 1929, observational evidence proved his fantasy was not to be fulfilled by Nature.
n order to understand this evidence, let's think about how a train sounds to a person standing on the platform. An arriving train makes a noise that starts low and gets higher pitched as the train approaches the listener, sounding like oooooohEEEEEEEE. A departing train makes a noise that gets lower pitched as the train goes away from the listener, sounding like EEEEEEEEoooooooh. This change in the sound of the pitch of the train noise depending on whether it is arriving or departing the listener is called the Doppler shift.
The Doppler shift
The Doppler shift
. The Doppler shift happens with light as well as with sound. A source of light that is approaching the viewer will seem to the viewer to have a higher frequency than a source of light that is receding from that viewer. In 1929, observations of distant galaxies showed that the light from those galaxies behaved as if they were going away from us. If all the distant galaxies are all receding from us on the average, that means that the Universe as a whole could be expanding. It could be blowing up like a balloon.
. If the Universe is expanding, then what did it expand from?
. This is what tells us that the Universe probably does have a finite age, it probably is not eternal and ageless as Einstein wanted to believe.
. But then, okay, how old is the Universe?
. We know from studies of radioactivity of the Earth and Sun that our solar system probably formed about 4.5 billions years ago, which means that the Universe must be at least twice that old, because before our solar system formed, our Milky Way galaxy had to form, and that probably took several billions years by itself.
. It would be reasonable to guess that the Universe is at least twice as old as our Sun and Earth. However, we can't do radioactive dating on distant stars and galaxies. The best we can do is balance a lot of different measurements of the brightness and distance of stars and the red shifting of their light to come up with some ballpark figure. The oldest star clusters whose age we can estimate are about 12 to 15 billions years old.
. So it seems safe to estimate that the age of the Universe is at least 15 billion years old, but probably not more than 20 billion years old.
. This matter is far from being settled by astrophysicists and cosmologists, so stay tuned. There could be radical new developments in the future.
. If the Universe is expanding, then what did it expand from?
. This is what tells us that the Universe probably does have a finite age, it probably is not eternal and ageless as Einstein wanted to believe.
. But then, okay, how old is the Universe?
. We know from studies of radioactivity of the Earth and Sun that our solar system probably formed about 4.5 billions years ago, which means that the Universe must be at least twice that old, because before our solar system formed, our Milky Way galaxy had to form, and that probably took several billions years by itself.
. It would be reasonable to guess that the Universe is at least twice as old as our Sun and Earth. However, we can't do radioactive dating on distant stars and galaxies. The best we can do is balance a lot of different measurements of the brightness and distance of stars and the red shifting of their light to come up with some ballpark figure. The oldest star clusters whose age we can estimate are about 12 to 15 billions years old.
. So it seems safe to estimate that the age of the Universe is at least 15 billion years old, but probably not more than 20 billion years old.
. This matter is far from being settled by astrophysicists and cosmologists, so stay tuned. There could be radical new developments in the future.
There are at least 3 ways that the age of the Universe can be estimated. I will describe
* The age of the chemical elements.
* The age of the oldest star clusters.
* The age of the oldest white dwarf stars.
The age of the Universe can also be estimated from a cosmological model based on the Hubble constant and the densities of matter and dark energy. This model-based age is currently 13.7 +/- 0.2 Gyr. But this Web page will only deal with actual age measurements, not estimates from cosmological models. The actual age measurements are consistent with the model-based age which increases our confidence in the Big Bang model.
* The age of the chemical elements.
* The age of the oldest star clusters.
* The age of the oldest white dwarf stars.
The age of the Universe can also be estimated from a cosmological model based on the Hubble constant and the densities of matter and dark energy. This model-based age is currently 13.7 +/- 0.2 Gyr. But this Web page will only deal with actual age measurements, not estimates from cosmological models. The actual age measurements are consistent with the model-based age which increases our confidence in the Big Bang model.
The Age of the Elements
The age of the chemical elements can be estimated using radioactive decay to determine how old a given mixture of atoms is. The most definite ages that can be determined this way are ages since the solidification of rock samples. When a rock solidifies, the chemical elements often get separated into different crystalline grains in the rock. For example, sodium and calcium are both common elements, but their chemical behaviours are quite different, so one usually finds sodium and calcium in different grains in a differentiated rock. Rubidium and strontium are heavier elements that behave chemically much like sodium and calcium. Thus rubidium and strontium are usually found in different grains in a rock. But Rb-87 decays into Sr-87 with a half-life of 47 billion years. And there is another isotope of strontium, Sr-86, which is not produced by any rubidium decay. The isotope Sr-87 is called radiogenic, because it can be produced by radioactive decay, while Sr-86 is non-radiogenic. The Sr-86 is used to determine what fraction of the Sr-87 was produced by radioactive decay. This is done by plotting the Sr-87/Sr-86 ratio versus the Rb-87/Sr-86 ratio. When a rock is first formed, the different grains have a wide range of Rb-87/Sr-86 ratios, but the Sr-87/Sr-86 ratio is the same in all grains because the chemical processes leading to differentiated grains do not separate isotopes. After the rock has been solid for several billion years, a fraction of the Rb-87 will have decayed into Sr-87. Then the Sr-87/Sr-86 ratio will be larger in grains with a large Rb-87/Sr-86 ratio. Do a linear fit of
Sr-87/Sr-86 = a + b*(Rb-87/Sr-86)
and then the slope term is given by
b = 2x - 1
with x being the number of half-lives that the rock has been solid. See the talk.origins isochrone FAQ for more on radioactive dating.
When applied to rocks on the surface of the Earth, the oldest rocks are about 3.8 billion years old. When applied to meteorites, the oldest are 4.56 billion years old. This very well determined age is the age of the Solar System. See the talk.origins age of the Earth FAQ for more on the age of the solar system.
When applied to a mixed together and evolving system like the gas in the Milky Way, no great precision is possible. One problem is that there is no chemical separation into grains of different crystals, so the absolute values of the isotope ratios have to be used instead of the slopes of a linear fit. This requires that we know precisely how much of each isotope was originally present, so an accurate model for element production is needed. One isotope pair that has been used is rhenium and osmium: in particular Re-187 which decays into Os-187 with a half-life of 40 billion years. It looks like 15% of the original Re-187 has decayed, which leads to an age of 8-11 billion years. But this is just the mean formation age of the stuff in the Solar System, and no rhenium or osmium has been made for the last 4.56 billion years. Thus to use this age to determine the age of the Universe, a model of when the elements were made is needed. If all the elements were made in a burst soon after the Big Bang, then the age of the Universe would be to = 8-11 billion years. But if the elements are made continuously at a constant rate, then the mean age of stuff in the Solar System is
(to + tSS)/2 = 8-11 Gyr
which we can solve for the age of the Universe giving
to = 11.5-17.5 Gyr
238U and 232Th are both radioactive with half-lives of 4.468 and 14.05 Gyrs, but the uranium is underabundant in the Solar System compared to the expected production ratio in supernovae. This is not surprising since the 238U has a shorter half-life, and the magnitude of the difference gives an estimate for the age of the Universe. Dauphas (2005, Nature, 435, 1203) combines the Solar System 238U:232Th ratio with the ratio observed in very old, metal poor stars to solve simultaneous equations for both the production ratio and the age of the Universe, obtaining 14.5+2.8-2.2 Gyr.
Radioactive Dating of an Old Star
(to + tSS)/2 = 8-11 Gyr
which we can solve for the age of the Universe giving
to = 11.5-17.5 Gyr
238U and 232Th are both radioactive with half-lives of 4.468 and 14.05 Gyrs, but the uranium is underabundant in the Solar System compared to the expected production ratio in supernovae. This is not surprising since the 238U has a shorter half-life, and the magnitude of the difference gives an estimate for the age of the Universe. Dauphas (2005, Nature, 435, 1203) combines the Solar System 238U:232Th ratio with the ratio observed in very old, metal poor stars to solve simultaneous equations for both the production ratio and the age of the Universe, obtaining 14.5+2.8-2.2 Gyr.
Radioactive Dating of an Old Star
A very interesting paper by Cowan et al. (1997, ApJ, 480, 246) discusses the thorium abundance in an old halo star. Normally it is not possible to measure the abundance of radioactive isotopes in other stars because the lines are too weak. But in CS 22892-052 the thorium lines can be seen because the iron lines are very weak. The Th/Eu (Europium) ratio in this star is 0.219 compared to 0.369 in the Solar System now. Thorium decays with a half-life of 14.05 Gyr, so the Solar System formed with Th/Eu = 24.6/14.05*0.369 = 0.463. If CS 22892-052 formed with the same Th/Eu ratio it is then 15.2 +/- 3.5 Gyr old. It is actually probably slightly older because some of the thorium that would have gone into the Solar System decayed before the Sun formed, and this correction depends on the nucleosynthesis history of the Milky Way. Nonetheless, this is still an interesting measure of the age of the oldest stars that is independent of the main-sequence lifetime method.
A later paper by Cowan et al. (1999, ApJ, 521, 194) gives 15.6 +/- 4.6 Gyr for the age based on two stars: CS 22892-052 and HD 115444.
A another star, CS 31082-001, shows an age of 12.5 +/- 3 Gyr based on the decay of U-238 [Cayrel, et al. 2001, Nature, 409, 691-692]. Wanajo et al. refine the predicted U/Th production ratio and get 14.1 +/- 2.5 Gyr for the age of this star.
The Age of the Oldest Star Clusters
The Age of the Oldest Star Clusters
When stars are burning hydrogen to helium in their cores, they fall on a single curve in the luminosity-temperature plot known as the H-R diagram after its inventors, Hertzsprung and Russell. This track is known as the main sequence, since most stars are found there. Since the luminosity of a star varies like M3 or M4, the lifetime of a star on the main sequence varies like t=const*M/L=k/L0.7. Thus if you measure the luminosity of the most luminous star on the main sequence, you get an upper limit for the age of the cluster:
Age <> 11.5 Gyr.
Hansen et al. have used the HST to measure the ages of white dwarfs in the globular cluster M4, obtaining 12.7 +/- 0.7 Gyr. In 2004 Hansen et al. updated their analysis to give an age for M4 of 12.1 +/- 0.9 Gyr, which is very consistent with the age of globular clusters from the main sequence turnoff. Allowing allowing for the time between the Big Bang and the formation of globular clusters (and its uncertainty) implies an age for the Universe of 12.8 +/- 1.1 Gyr.
Until recently, astronomers estimated that the Big Bang occurred between 12 and 14 billion years ago. To put this in perspective, the Solar System is thought to be 4.5 billion years old and humans have existed as a species for a few million years. Astronomers estimate the age of the universe in two ways: 1) by looking for the oldest stars; and 2) by measuring the rate of expansion of the universe and extrapolating back to the Big Bang; just as crime detectives can trace the origin of a bullet from the holes in a wall.
Older Than the Oldest Stars?
Older Than the Oldest Stars?
Astronomers can place a lower limit to the age of the universe by studying globular clusters. Globular clusters are a dense collection of roughly a million stars. Stellar densities near the center of the globular cluster are enormous. If we lived near the center of one, there would be several hundred thousand stars closer to us than Proxima Centauri, the star nearest to the Sun.
The life cycle of a star depends upon its mass. High mass stars are much brighter than low mass stars, thus they rapidly burn through their supply of hydrogen fuel. A star like the Sun has enough fuel in its core to burn at its current brightness for approximately 9 billion years. A star that is twice as massive as the Sun will burn through its fuel supply in only 800 million years. A 10 solar mass star, a star that is 10 times more massive than the Sun, burns nearly a thousand times brighter and has only a 20 million year fuel supply. Conversely, a star that is half as massive as the Sun burns slowly enough for its fuel to last more than 20 billion years.
All of the stars in a globular cluster formed at roughly the same time, thus they can serve as cosmic clocks. If a globular cluster is more than 20 million years old, then all of its hydrogen burning stars will be less massive than 10 solar masses. This implies that no individual hydrogen burning star will be more than 1000 times brighter than the Sun. If a globular cluster is more than 2 billion years old, then there will be no hydrogen-burning star more massive than 2 solar masses.
The oldest globular clusters contain only stars less massive than 0.7 solar masses. These low mass stars are much dimmer than the Sun. This observation suggests that the oldest globular clusters are between 11 and 18 billion years old. The uncertainty in this estimate is due to the difficulty in determining the exact distance to a globular cluster (hence, an uncertainty in the brightness (and mass) of the stars in the cluster). Another source of uncertainty in this estimate lies in our ignorance of some of the finer details of stellar evolution. Presumably, the universe itself is at least as old as the oldest globular clusters that reside in it.
Extrapolating Back to the Big Bang
An alternative approach to estimating is the age of the universe is to measure the “Hubble constant”. The Hubble constant is a measure of the current expansion rate of the universe. Cosmologists use this measurement to extrapolate back to the Big Bang. This extrapolation depends on the history of the expansion rate which in turn depends on the current density of the universe and on the composition of the universe.
If the universe is flat and composed mostly of matter, then the age of the universe is
2/(3 Ho)
where Ho is the value of the Hubble constant.
If the universe has a very low density of matter, then its extrapolated age is larger:
1/Ho
If the universe contains a form of matter similar to the cosmological constant, then the inferred age can be even larger.
Many astronomers are working hard to measure the Hubble constant using a variety of different techniques. Until recently, the best estimates ranged from 65 km/sec/Megaparsec to 80 km/sec/Megaparsec, with the best value being about 72 km/sec/Megaparsec. In more familiar units, astronomers believe that 1/Ho is between 12 and 14 billion years.
An Age Crisis?
If we compare the two age determinations, there is a potential crisis. If the universe is flat, and dominated by ordinary or dark matter, the age of the universe as inferred from the Hubble constant would be about 9 billion years. The age of the universe would be shorter than the age of oldest stars. This contradiction implies that either 1) our measurement of the Hubble constant is incorrect, 2) the Big Bang theory is incorrect or 3) that we need a form of matter like a cosmological constant that implies an older age for a given observed expansion rate.
The life cycle of a star depends upon its mass. High mass stars are much brighter than low mass stars, thus they rapidly burn through their supply of hydrogen fuel. A star like the Sun has enough fuel in its core to burn at its current brightness for approximately 9 billion years. A star that is twice as massive as the Sun will burn through its fuel supply in only 800 million years. A 10 solar mass star, a star that is 10 times more massive than the Sun, burns nearly a thousand times brighter and has only a 20 million year fuel supply. Conversely, a star that is half as massive as the Sun burns slowly enough for its fuel to last more than 20 billion years.
All of the stars in a globular cluster formed at roughly the same time, thus they can serve as cosmic clocks. If a globular cluster is more than 20 million years old, then all of its hydrogen burning stars will be less massive than 10 solar masses. This implies that no individual hydrogen burning star will be more than 1000 times brighter than the Sun. If a globular cluster is more than 2 billion years old, then there will be no hydrogen-burning star more massive than 2 solar masses.
The oldest globular clusters contain only stars less massive than 0.7 solar masses. These low mass stars are much dimmer than the Sun. This observation suggests that the oldest globular clusters are between 11 and 18 billion years old. The uncertainty in this estimate is due to the difficulty in determining the exact distance to a globular cluster (hence, an uncertainty in the brightness (and mass) of the stars in the cluster). Another source of uncertainty in this estimate lies in our ignorance of some of the finer details of stellar evolution. Presumably, the universe itself is at least as old as the oldest globular clusters that reside in it.
Extrapolating Back to the Big Bang
An alternative approach to estimating is the age of the universe is to measure the “Hubble constant”. The Hubble constant is a measure of the current expansion rate of the universe. Cosmologists use this measurement to extrapolate back to the Big Bang. This extrapolation depends on the history of the expansion rate which in turn depends on the current density of the universe and on the composition of the universe.
If the universe is flat and composed mostly of matter, then the age of the universe is
2/(3 Ho)
where Ho is the value of the Hubble constant.
If the universe has a very low density of matter, then its extrapolated age is larger:
1/Ho
If the universe contains a form of matter similar to the cosmological constant, then the inferred age can be even larger.
Many astronomers are working hard to measure the Hubble constant using a variety of different techniques. Until recently, the best estimates ranged from 65 km/sec/Megaparsec to 80 km/sec/Megaparsec, with the best value being about 72 km/sec/Megaparsec. In more familiar units, astronomers believe that 1/Ho is between 12 and 14 billion years.
An Age Crisis?
If we compare the two age determinations, there is a potential crisis. If the universe is flat, and dominated by ordinary or dark matter, the age of the universe as inferred from the Hubble constant would be about 9 billion years. The age of the universe would be shorter than the age of oldest stars. This contradiction implies that either 1) our measurement of the Hubble constant is incorrect, 2) the Big Bang theory is incorrect or 3) that we need a form of matter like a cosmological constant that implies an older age for a given observed expansion rate.
Some astronomers believe that this crisis will pass as soon as measurements improve. If the astronomers who have measured the smaller values of the Hubble constant are correct, and if the smaller estimates of globular cluster ages are also correct, then all is well for the Big Bang theory, even without a cosmological constant.
WMAP Can Measure the Age of the Universe
Measurements by the WMAP satellite can help resolve this crisis. If current ideas about the origin of large-scale structure are correct, then the detailed structure of the cosmic microwave background fluctuations will depend on the current density of the universe, the composition of the universe and its expansion rate. WMAP has been able to determine these parameters with an accuracy of better than 5%. Thus, we can estimate the expansion age of the universe to better than 5%. When we combine the WMAP data with complimentary observations from other CMB experiments (ACBAR and CBI), we are able to determine an age for the universe closer to an accuracy of 1%.
The expansion age measured by WMAP is larger than the oldest globular clusters, so the Big Bang theory has passed an important test. If the expansion age measured by WMAP had been smaller than the oldest globular clusters, then there would have been something fundamentally wrong about either the Big Bang theory or the theory of stellar evolution. Either way, astronomers would have needed to rethink many of their cherished ideas. But our current estimate of age fits well with what we know from other kinds of measurements: the Universe is about 13.7 billion years old!
Closing
Memang banyak sekali pendapat berbeda mengenai usia jagat raya itu, tapi yang terpenting adalah:"read in the name of lord who was created" karena ujung dari pencarian adalah Dia di Atas Segalanya.
sumber:
http:// astrophysicblogs.blogspot.com,
Pontianak post
Another Source in Book and The Internet Web-Site .
WMAP Can Measure the Age of the Universe
Measurements by the WMAP satellite can help resolve this crisis. If current ideas about the origin of large-scale structure are correct, then the detailed structure of the cosmic microwave background fluctuations will depend on the current density of the universe, the composition of the universe and its expansion rate. WMAP has been able to determine these parameters with an accuracy of better than 5%. Thus, we can estimate the expansion age of the universe to better than 5%. When we combine the WMAP data with complimentary observations from other CMB experiments (ACBAR and CBI), we are able to determine an age for the universe closer to an accuracy of 1%.
The expansion age measured by WMAP is larger than the oldest globular clusters, so the Big Bang theory has passed an important test. If the expansion age measured by WMAP had been smaller than the oldest globular clusters, then there would have been something fundamentally wrong about either the Big Bang theory or the theory of stellar evolution. Either way, astronomers would have needed to rethink many of their cherished ideas. But our current estimate of age fits well with what we know from other kinds of measurements: the Universe is about 13.7 billion years old!
Closing
Memang banyak sekali pendapat berbeda mengenai usia jagat raya itu, tapi yang terpenting adalah:"read in the name of lord who was created" karena ujung dari pencarian adalah Dia di Atas Segalanya.
sumber:
http:// astrophysicblogs.blogspot.com,
Pontianak post
Another Source in Book and The Internet Web-Site .
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