How many of us can truly say that we really got the thing we
wanted in life? When I learned about the discovery of the first
gravitationally lensed quasar, I shared a fascination with many
astronomers, because it showed a simple beauty and complexity of
the universe, and because we all wondered what tool for further
investigation it would prove to be. Within months we heard that
the two images of a distant quasar seen did not arrive at the
same time, meaning that there was a time delay between the
arrival of the two images. and measurement of this time delay
would provide powerfully important information about the
structure of the universe. I immediately set out to measure this
time delay in fierce compeetition with several other research
groups, and was the first to succeed in 1985. But although my
result was first confirmed in 1988 by another research group, it
was questioned by a famous astronomer in 1991 and I was being
shunned and ridiculed at research forums around the world.
Finally the error of their result was recognized in 1996-97, and
it is known that my original
determination of 1986 was and is correct.
So did I get what I wanted in life? Not really, because during the period of doubt I knew I was right and continued the investigation with better data, and found the answer to an even bigger question: what is the nature and origin of the dark matter? And so just as the world was acknowledging the success of my time delay determination, I was publishing a paper describing the detection and nature of dark matter. Today that work is controversial but preliminary reports confirm the accuracy of my data though the interpretation is still being checked. Am I satisfied?
No, because now I am reaching farther still to understand the growth of structure in the universe, with a fluid dynamics expert. We are trying to understand why the universe has broken itself down into galaxies in their clusters, stars, and people. Why is the universe not just a uniform sea of gas?
So if we have succeeded (our paper is written but not yet published) will I be happy? Probably not, because this discovery raises even more questions. Maybe I really never wanted discovery; maybe I really just wanted controversey. But I don't think so. I don't think it takes a scientist to have ever more questions. I think it is just human, and I present to you Rudy Schild, the human being.
Other windows will present the many objects of fascination in my life. Below is a description of the meaning and significance of my time delay discovery. In time I plan to write a more detailed historical account; some might prefer that I don't.
A beautiful result of the Einstein General Theory of Relativity is that the mass of any object can bend light, and in a few cases this is a large enough effect to be seen. The best prospects are for a distant quasar acting like a light beacon, for a round galaxy between us and the quasar attracts the light around it, and we see not the quasars point image, but a small ring. But the foreground galaxy has to be exactly in the line of sight to the quasar, which never happens, so in the more general case we see not a ring around the lens galaxy, but two point images, one on each side of the lens. About 50 examples of this are now known, and are called multiple image gravitational lenses.
Before the first of these was found by Dennis Walsh in 1979, Sjur Refsdal noticed that the equations that described the multiple images and their relationship to the lens galaxy became closed if the time delay between the arrival of the two images could be measured. Thus it would be possible to measure the image separations and lens galaxy position, and the redshift distances to the lens and quasar and from the time delay measurement we would determine the distance of the quasar and lens in miles. From this miles distance and redshift distance we would determine the expansion rate and age of the universe. Other methods to measure this, especially by Alan Sandage and Gustav Tammann, were controversial because in their methods the corrections for past evolution of all their standard astronomical sources might come into play in ways too complex to understand. Our method was simple and elegant, and independent of all the other measurements being championed by others.
Because quasars all twinkle slightly, with brightness changes of a few percent occurring in a month, my method was to observe the pattern of brightness fluctuations in the first arriving northern (A) image, and then look for the same pattern to arrive in the second arriving (B) image. Then the time between arrivals of the twinkling pattern is the time delay. Many others tried to do the same thing, but the twinkling would need to be measured for years to recognize the patterns. By 1985 I had recognized the patterns and with student Brian Cholfin I published the now famous paper that says that the pattern repeats itself in the second arriving image after 1.1 years.
With this time delay and the mathematical models describing the lens positions and the gravitational fields, it has been possible to say that the universe is expanding at the rate of 64 km/sec/Kpc, and that this expansion started 12 billion years ago. This is close to the values championed by Sandage and Tammann, and it is generally accepted that the method works well, and is being checked for more multiple image gravitational lenses, as more time delays are now being measured.
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