December 3, 2008
The New Cosmology
David N. Spergel
Department of Astrophysical Sciences, Princeton
Minutes of the 11th Meeting of the 67th Year
President Hansen gaveled the 11th meeting of our 67th year to order promptly at 10:15 AM. There were 97 members present.
Don Edwards led the invocation.
Tom Fulmer read the minutes of the preceding meeting, which were accepted without rancor.
Scott McVay introduced his guest, his wife.
Robert Miller introduced his visitor, Alice Whipple, widow of the late Old Guard member General Bill Whipple.
Bill Bonini announced new arrangements for member parking in Lot 21.
Scott McVay introduced our speaker at this meeting, Professor David N. Spergel, Chairman of the Astrophysics Department of Princeton. Professor Spergel is a graduate of Princeton, Oxford and Harvard. He was a MacArthur fellow and was named one of America’s foremost scientists by Time in 2001. In 2003 a paper of his was the most cited by Astronomers. In 2007 he was elected to the National Academy of Science.
Professor Spergel’s talk was entitled: The New Cosmology.
Professor Spergel took us on a dazzling and challenging trip forward through the last 25 years of progress in Cosmology, and backwards 13.6 billion years in the history of the Universe. The cosmologist, he said, is like an archeologist or historian, reconstructing the past from observations in the present. Observations made of distant objects in the sky are of necessity views of those objects as they were some time in the past, for the speed of light is finite. For example it takes 8 minutes for light from the sun to get to us, thus we see the sun as it was 8 minutes ago. For the cosmologists a typical time instead of 8 minutes would be a billion years or so. This means we can actually see what the Universe looked like billions of years ago provided we can see things far enough away.
In 1964, at AT&T’s Bell Labs in northern New Jersey, Arno Penzias, and Robert Wilson were looking at the sky, not in the range of visual frequencies, but in the far higher microwave range, and they found radiation coming from every direction they looked. Their observations were consistent with the consequences of an incomprehensibly violent explosion billions of years ago, i.e., a Hot Big Bang. Wilkinson and Dicke at Princeton helped clarify their findings, and the age of radio astronomy burgeoned. Subsequent experiments to examine this Cosmic Microwave Background were undertaken in 1989 by the COBE satellite, and then in 2001 the WMAP (Wilkinson Microwave Anisotropy Probe), a Princeton led project, was launched. Data from these satellites along with observations from the 142 megapixel digital Sloan camera have answered many of the questions astrophysicists, cosmologists and ordinary folk ask, and allowed the establishment of a so-called “Standard Model” of the Universe, (which apparently will celebrate its 13.6 billionth birthday next March).
One of the questions a cosmologist asks about the Universe is: What is its shape? Is the sum of the angles of a triangle greater than 180 degrees, as on the surface of the earth, less than 180 as on the surface of a saddle, or exactly180 as on a flat plane? Each of these cases predicts a different end to the Universe. In the first case, Gravitational energy exceeds Kinetic Energy and the Universe will eventually fall in on itself, in the second case Gravitational Energy is insufficient to keep the Universe together and it expands forever. The third case is the boundary between eternal expansion and collapse. Einstein thought the Universe was static and when he plugged that information into General Relativity he found he must conclude that the Universe is expanding or contracting. He thought that this contradicted observations and so introduced a constant to correct the formulae. When Hubble discovered in 1929 that in fact the Universe did seem to be expanding, since distant galaxies were receding faster than nearby ones, Einstein admitted a mistake. It turns out in fact Einstein was not really wrong. Information from the satellites indicates The Universe is very close to flat, and a constant is indeed needed!
Data from the WMAP allows the construction of a map of the temperature in the Universe about 300,000 years after the Big Bang. We were shown images of these amazing maps and were told that the data they contained demonstrated remarkable agreement with the hypothesis of a “Hot Big Bang” followed by rapid “Inflation.” For example if there were slight fluctuations in the initial distribution of material then that would lead to sound (pressure) waves which would propagate in the early Universe and lead to ripples in the MWB. This predicted effect was observed, along with a number of others, all consistent with the hypothesis of a Hot Big Bang followed by rapid inflation. In addition, the new Standard Model’s description of the Universe at 300,000 years of age can be extrapolated forward and the resulting clustering of galaxies compared with observations from the Sloan digital camera. When this was done there was excellent agreement. In short the new Standard Model of the early Universe, with only 5 parameters, is in agreement with all the observations we have been able to make.
There are still many mysteries remaining; for example it has been necessary to posit both matter we cannot see and energy we cannot directly detect. This dark matter and dark energy are receiving attention by cosmologists, particle physicists, philosophers, and serious cranks. Also troubling is an embarrassing inconsistency in this domain between quantum theory and general relativity.
However, with this new, exciting, and extensive knowledge of the early Universe we seem now to be in a position to understand better what it is we don’t understand.
The lecture was followed by a number of interesting questions. Professor Spergel awarded a signed copy of one of his papers to Cyril Franks for his question, which the professor adjudged to be the best.
Respectfully submitted,
Lee Neuwirth
Don Edwards led the invocation.
Tom Fulmer read the minutes of the preceding meeting, which were accepted without rancor.
Scott McVay introduced his guest, his wife.
Robert Miller introduced his visitor, Alice Whipple, widow of the late Old Guard member General Bill Whipple.
Bill Bonini announced new arrangements for member parking in Lot 21.
Scott McVay introduced our speaker at this meeting, Professor David N. Spergel, Chairman of the Astrophysics Department of Princeton. Professor Spergel is a graduate of Princeton, Oxford and Harvard. He was a MacArthur fellow and was named one of America’s foremost scientists by Time in 2001. In 2003 a paper of his was the most cited by Astronomers. In 2007 he was elected to the National Academy of Science.
Professor Spergel’s talk was entitled: The New Cosmology.
Professor Spergel took us on a dazzling and challenging trip forward through the last 25 years of progress in Cosmology, and backwards 13.6 billion years in the history of the Universe. The cosmologist, he said, is like an archeologist or historian, reconstructing the past from observations in the present. Observations made of distant objects in the sky are of necessity views of those objects as they were some time in the past, for the speed of light is finite. For example it takes 8 minutes for light from the sun to get to us, thus we see the sun as it was 8 minutes ago. For the cosmologists a typical time instead of 8 minutes would be a billion years or so. This means we can actually see what the Universe looked like billions of years ago provided we can see things far enough away.
In 1964, at AT&T’s Bell Labs in northern New Jersey, Arno Penzias, and Robert Wilson were looking at the sky, not in the range of visual frequencies, but in the far higher microwave range, and they found radiation coming from every direction they looked. Their observations were consistent with the consequences of an incomprehensibly violent explosion billions of years ago, i.e., a Hot Big Bang. Wilkinson and Dicke at Princeton helped clarify their findings, and the age of radio astronomy burgeoned. Subsequent experiments to examine this Cosmic Microwave Background were undertaken in 1989 by the COBE satellite, and then in 2001 the WMAP (Wilkinson Microwave Anisotropy Probe), a Princeton led project, was launched. Data from these satellites along with observations from the 142 megapixel digital Sloan camera have answered many of the questions astrophysicists, cosmologists and ordinary folk ask, and allowed the establishment of a so-called “Standard Model” of the Universe, (which apparently will celebrate its 13.6 billionth birthday next March).
One of the questions a cosmologist asks about the Universe is: What is its shape? Is the sum of the angles of a triangle greater than 180 degrees, as on the surface of the earth, less than 180 as on the surface of a saddle, or exactly180 as on a flat plane? Each of these cases predicts a different end to the Universe. In the first case, Gravitational energy exceeds Kinetic Energy and the Universe will eventually fall in on itself, in the second case Gravitational Energy is insufficient to keep the Universe together and it expands forever. The third case is the boundary between eternal expansion and collapse. Einstein thought the Universe was static and when he plugged that information into General Relativity he found he must conclude that the Universe is expanding or contracting. He thought that this contradicted observations and so introduced a constant to correct the formulae. When Hubble discovered in 1929 that in fact the Universe did seem to be expanding, since distant galaxies were receding faster than nearby ones, Einstein admitted a mistake. It turns out in fact Einstein was not really wrong. Information from the satellites indicates The Universe is very close to flat, and a constant is indeed needed!
Data from the WMAP allows the construction of a map of the temperature in the Universe about 300,000 years after the Big Bang. We were shown images of these amazing maps and were told that the data they contained demonstrated remarkable agreement with the hypothesis of a “Hot Big Bang” followed by rapid “Inflation.” For example if there were slight fluctuations in the initial distribution of material then that would lead to sound (pressure) waves which would propagate in the early Universe and lead to ripples in the MWB. This predicted effect was observed, along with a number of others, all consistent with the hypothesis of a Hot Big Bang followed by rapid inflation. In addition, the new Standard Model’s description of the Universe at 300,000 years of age can be extrapolated forward and the resulting clustering of galaxies compared with observations from the Sloan digital camera. When this was done there was excellent agreement. In short the new Standard Model of the early Universe, with only 5 parameters, is in agreement with all the observations we have been able to make.
There are still many mysteries remaining; for example it has been necessary to posit both matter we cannot see and energy we cannot directly detect. This dark matter and dark energy are receiving attention by cosmologists, particle physicists, philosophers, and serious cranks. Also troubling is an embarrassing inconsistency in this domain between quantum theory and general relativity.
However, with this new, exciting, and extensive knowledge of the early Universe we seem now to be in a position to understand better what it is we don’t understand.
The lecture was followed by a number of interesting questions. Professor Spergel awarded a signed copy of one of his papers to Cyril Franks for his question, which the professor adjudged to be the best.
Respectfully submitted,
Lee Neuwirth