In the last hundred years there has been great progress in all fields of science. One of the areas where progress has been particularly impressive is the field of astronomy and astrophysics (the physics of the universe)
** Explanation for the illustration
By Prof. Yoram Kirsh, Department of Natural and Life Sciences, The Open University. Prof. Kirsch lectured on the subject at the annual conference of the Israeli Astronomical Society held yesterday, Friday, at the Open University in Ra'anana.
The data processing can be described in the following way. The sky is divided into squares with a certain angular width (eg 10) and the difference between the average temperature in each square and the average temperature of the background radiation as a whole is calculated. Then the average of these differences is calculated. When you repeatedly change the size of the squares and repeat the calculation, you get the graph in the figure. The vertical axis in the graph is the average temperature difference (?T) in units of 1 divided by 100,000 degrees Kelvin. On the horizontal axis appears the parameter l related to the size of the squares. (1800 divided by l is the angular width of the squares, which appears on the upper scale). The circles in the graph are the results of MAP measurements and some ground experiments. The continuous line shows the theoretical calculation of ?T, which corresponds to the measurement results.
In the last hundred years there has been great progress in all fields of science. One of the areas where progress has been particularly impressive is the field of astronomy and astrophysics (the physics of the universe). It is hard to believe how little our astronomical knowledge was less than a century ago. For example, until 1924 astronomers thought that the Milky Way galaxy was the entire universe. This hypothesis was disproved in 1924 by the American astronomer Edwin Hubble, who studied nebula-like celestial bodies at the Mount Wilson Observatory in southern California. Using the observatory's 2.5 meter diameter telescope, Hubble proved that these nebulae are outside our galaxy, and are galaxies in their own right.
In the years 1925 - 1929, Hubble made another discovery: the galaxies in the universe are moving away from each other, and there is a direct relationship between the distance of the galaxy from us and its speed. It can be concluded that about 14 billion years ago all the matter in the universe was concentrated in one small area. According to the accepted theory today, the universe was then created in a kind of tremendous explosion known as the "Big Bang".
The cosmic background radiationThe best proof of the big bang is the "cosmic background radiation" that was discovered in 1965. It was discovered by two physicists from the Bell company, Arno Penzias (Penzias) and Robert Wilson (Wilson), who were testing a new radio antenna for satellite communication. They discovered that the antenna picks up constant "noise" of electromagnetic radiation in the microwave field. This radiation arrived with the same intensity from all directions in the sky and it turned out that it behaves like radiation emitted by a body at a temperature of about three degrees above absolute zero. (Radiation whose characteristics match the radiation emitted by hot bodies is called by physicists "black body radiation"). It was found out that this is radiation that has survived in the universe since the big bang, and gradually cooled due to the expansion of the universe.
According to the theory there should have been small differences between the temperatures of the radiation in different regions of the universe. The reason for this is that the temperature of the background radiation is a kind of "photograph" of the universe when it was about 400 thousand years old. In order for stars and galaxies to form, there had to be slight density differences in the young universe. The denser places attracted the material around them, and thus concentrations of material were formed from which the stars, galaxies and galaxy clusters we see today grew over time. A calculation showed that the temperature differences should be of the order of one in a hundred thousand.
Most researchers believed that there was no chance of discovering such small differences. But there was one "crazy talker" who thought otherwise. It was Dr. George Smoot, (Smoot) from Berkeley, who from 1970 was engaged in measurements of the background radiation with the help of instruments flown in airplanes and balloons. Smoot initiated a study to discover the non-uniformity in the background radiation. The planning began in the mid-seventies and the research was successfully completed in 1992, when a research satellite named COBE (cosmic background explorer), designed by Smoot and his team, did discover differences of the order of one in a hundred thousand in the radiation temperature at different points in the sky. The results provided a renewed and impressive verification of the Big Bang and were widely acclaimed. Smoot wrote a fascinating book about this called Wrinkles in Time (published in Hebrew by Maariv Library).
Following Kobi's findings, astrophysicists began to theoretically test how different parameters, such as the age of the universe and the amount of matter in the universe, affect the fluctuations in the background radiation. The tests showed that it is possible to extract important information from these fluctuations, if they are measured with more accurate devices than Kobe's. The map of the background radiation provided by Kobi allowed the researchers to compare the average temperature between areas with a diameter of seven degrees of arc or more (the complete circle has 360 degrees). This can be compared to a passport photo measuring 5 cm, which consists of squares measuring 5 mm in black, white and shades of gray. We may be able to identify who is photographed in the photo, but it is doubtful whether its quality will be sufficient for a passport or ID card.
NASA, which helped build Kobe and flew it into space, began planning a new research satellite to measure the background radiation. The satellite was called MAP (acronym for Microwave Anisotropy Probe. Later it was called WMAP in memory of David Wilkinson [Wilkinson] who was one of the initiators of MAP). The separation capability in MAP measurements reached a fifth of a degree. MAP was successfully launched in June 2001 and the astrophysicist community eagerly awaited the results.
Deciphering the secrets of creation
The measurements lasted a whole year when MAP orbited the Sun and was constantly 1.5 million km from Earth. Each piece of sky was sampled several thousand times, at five frequencies in the microwave field. The results were published in February 2003 (about two weeks after the Columbia disaster in which seven astronauts perished, including Ilan Ramon). MAP's results exceeded all expectations. Together with the results of ground instruments and instruments launched in balloons, they confirmed the Big Bang theory and yielded very accurate values of various parameters related to the evolution of the universe. For example, it was found that the age of the universe is 13.7 billion years, with an accuracy of one percent (previous estimates spoke of 13-15 billion years).
The results provided confirmation for a modern version of the big bang theory called the expanding universe theory. According to this theory, proposed in 1981 by Ellen Guth from the USA, at a very early stage of the universe's development there was a brief period of very rapid expansion known as "inflation". During this period the universe doubled its size repeatedly, about a hundred times. Then it continued to spread at a much slower rate.
Goth's theory answers the troubling question: Where did the initial energy from which the matter and radiation in the universe came from? According to the bulge model, most of the matter and radiation was created during the bulge, through physical processes that we are able to understand and analyze. (In contrast, according to the standard model of the Big Bang, all the matter and radiation that fills the universe today suddenly appeared out of nowhere).
It can be said that the inflation model to some extent removes the veil of mystery over the act of creation.
How much matter is there in the universe?We can estimate with great precision the mass of the Earth, the mass of each of the planets, the mass of the Sun, and also the mass of more distant stars, but is it possible to estimate the total mass of the universe, or the density of matter in the universe? This question is important because the amount of matter and energy in the universe determines whether it will continue to expand forever, or whether the forces of gravity will cause the expansion to slow down and the universe will begin to contract. The limiting value is called "critical density". If the density of matter and energy in the universe is less than the critical density, the expansion of the universe will continue forever. If it is above the critical density, the expansion will reverse direction at some point, and eventually all the matter in the universe will again be accumulated in a very small area.
MAP's findings solved the puzzle. It follows from them that the density of matter and energy in the universe is equal to the critical density, with a possible error of less than one percent. Only about four percent of this density is made of the material from which the atoms are built. 23 percent is a mysterious substance whose nature still requires clarification, known as dark matter. Another 73 percent is mysterious energy, which is somewhat similar to the energy that drove the expansion of the universe during the inflationary period. This energy was named dark energy. Is dark energy indeed a remnant of that primordial energy, or a new phenomenon that did not exist in the early universe? We still don't know the answer. Let's hope she finds it in the future.
* On the summer solstice: The Open University held a symposium on astronomy and space exploration
The Open University held a symposium on astronomy and space exploration on the occasion of the 100th anniversary of the publication of Albert Einstein's article on the theory of relativity (June, 1905) and as part of the events of the International Year of Physics.
The lectures on the seminar presented the updated and modern astronomical knowledge based on the latest observations from spaceships and telescopes on Earth.
Prof. Yoram Kirsh from the Department of Natural and Life Sciences at the Open University will speak on the day of the seminar about the discoveries of the COBE and WMAP spacecraft and the way in which physics describes the creation of the world. Prof. Elia Leibovitz from the School of Physics and Astronomy at Tel Aviv University, told about the most massive explosion in the universe, of stars known as "gamma radiation bursts"; Yigal Fattal from the Israeli Astronomical Society and the Open University explained what solar and white eclipses are and in particular will present the total solar eclipse that will occur near Israel in March 2006; Finally, Dr. Yoav Yair, from the Department of Natural and Life Sciences at the Open University, presented innovations and discoveries in the study of the planets Mars, Saturn and other bodies in the solar system.
Abstract of a lecture on June 21.6.05, XNUMX) * [Note: The abstract has already been published in "Adafar", in the Open University Town]
* The article was published for the first time on the Hedaan website on 22.6.2005/XNUMX/XNUMX
9 תגובות
1. Compressions:
The protons and neutrons that make up the nucleus are made up of quarks. The quarks as well as the electrons are point particles. Apparently - there is no barrier to compression.
It is important to remember that in sufficiently small dimensions (a considerable number of orders of magnitude below the size of the nucleon) - there is a necessity for quantum gravity/string - and out of caution it would be appropriate to stop speculation in these dimensions.
2. The expansion of the universe:
Indeed, in principle there is no way to directly check how the galaxies at the edge of the visible universe are moving at this moment.
Cosmology poses an epistemological challenge to the scientists since they are unable to perform laboratory experiments in which starting conditions are chosen and ending conditions are compared to predicted results. The universe only presents us with the conditions of the end.
An important element in science in general, and in cosmology on the difficulty that has just been identified - in particular: is the cross-referencing of evidence from independent sources.
The measurement of the rate of receding of the distant galaxies was indeed the only evidence of the acceleration phenomenon in the years 1998-2003, and was indeed received with skepticism.
In 2003, with the WMAP and SDSS results, independent and convincing supporting evidence was added.
The totality of the evidence is not consistent with a universe that has begun or will begin to shrink.
Locally (and in the order of magnitude of the universe, millions of light years is a local phenomenon) it is certainly possible that the forces of attraction between concentrations of matter will "win" and we will see phenomena like the approach of Andromeda.
2. More universes
Unlike the discussions in the context of the expansion of the universe, the programming of the existence of additional "universes" is not currently supported by experimental results.
At the same time, there are speculative models within which there may certainly be additional universes, and perhaps even ones with different laws of physics.
A few comments and questions at the end. Thanks to whoever can answer
Scientific and elegant answers. Thanks.
1. Matter is made up of atoms and their parts (protons, neutrons and electrons) and sub-particles.
No matter how big the space between the particles, i.e. the emptiness, even if we assume that the "internuclear space" is large
At a trillion times the volume of the particles themselves, it's still hard to understand
that the compression of the universe at the beginning of the bang was such that all the matter in the universe was concentrated in such a small point.
Is there no limit to the degree of compression of the material?
Can anyone explain?
2. The accepted opinion today is that the galaxies run "out"
from each other, and the further they are, the greater their escape speed. Right ? Well, when we see a galaxy that is a billion or 10 billion light years away from us, we understand that a billion or 10 billion years ago (respectively) this was their speed. How can we know what their speed is today? the mother
It is not possible that some time ago their speed slowed down and maybe today
Has the universe reversed its motion and is in a state of collapse? Especially if you take into account that the Andromeda galaxy is far from us
"Only" about 2 million light years actually approaching us?
3. First they thought that the earth was the center of the universe, then the sun
She is the center, after all there are billions of suns in the single galaxy
And finally we discovered that there are billions more galaxies arranged in clusters and superclusters. (As the telescopes become more sophisticated, we discover more distant galaxies).
The question is whether it is not possible that there are thousands or billions more
Universes that we are still not able to see with our means today??
Leo - now there is something that explains the acceleration of the expansion of the universe - see an article from December 25 about the repulsive force of the vacuum.
Every theory will end up being invalidated by a new theory that will also be invalidated by a new theory that will also be invalidated by a new theory and all and all forever and ever
The examples below describe the ideas of ancient sages regarding the issues of the universe:
The philosopher Thales, who lived about 600 years BC, believed that the earth is flat, a kind of island surrounded by an endless sea; His student, Anascimander, claimed that the earth is shaped like a cylinder, surrounded by a sphere full of stars.
A little after him, Pythagoras stated that the earth is a sphere, surrounded by 7 crystal balls, and inside them are the sun, the moon, the planets and the fixed stars.
Ptolemy (Ptolemaus Claudius) in the second century AD, decided that the earth is in the center of the universe, and around it the heavenly bodies, in the following order: the moon, Mercury, Venus, the sun, Mars, Jupiter and Saturn, and beyond the orbit of Saturn were fixed the stars of the Sabbath.
Aristarchus of Samos, from the 3rd century, who claimed that the earth revolves around the sun, as we know today; His innovative concept, which was contrary to what was accepted at the time, was ridiculed and canceled altogether, and Ptolemy's assertion was not only unshaken - it survived for about 1500 years.
After the teachings of Copernicus were adopted, corrections began such as those of Kepler, who claimed (his claim was verified as we know) that the movement of the planets around the sun is elliptical and not circular; Also, after the development of telescopes from Galileo's time, it was determined that there is only one galaxy, which contains all the stars that can be seen in the sky.
Cosmology developed as a science, after the introduction of Albert Einstein's theory of relativity, and with the discovery of the redshift by Edwin Hubble, which concluded that the universe was expanding, and the discovery of the cosmic background radiation by Panzias and Wilson in 1964, the Big Bang theory was strengthened.
In summary: the clear characteristic of all the above-mentioned theories of the universe, including the big bang theory with all the corrections and reinforcements that were developed in order to finally confirm it
(Reminder: Kepler also made, through his three laws, important and revolutionary corrections for his time.), captives, and limiting themselves in the basic definition formulated:
1 . The universe is all there is, and there is nothing outside of it. The edge of the universe is the edge of space. He is one, and everything is within Him.
2. As the universes of the aforementioned teachings expanded, so did man's abilities in all the different fields of science.
3. The difficulty existing in our times, to expand the universe beyond 13 billion light years; These enormous dimensions, it is difficult to delineate them in the description of barely a microscopic point, when comparing their size, to infinity; This difficulty is strengthened as for example, in light of the additional difficulty, to understand how a person in size, in relation to the size of an ant, is not even that kind of size.
To Benjamin, I don't know what the formula is but I know what the result is. 42.
I discovered a formula that will change the world forever!!!!!!!!!
Things are not so simple regarding the expansion of the universe. In recent years it has become clear that the receding galaxies actually accelerate instead of slowing down or moving at a constant speed. There is still no satisfactory explanation for the phenomenon that is accepted by astrophysicists.