How many of us can truly say that we really got the thing wewanted in life? When I learned about the discovery of the firstgravitationally lensed quasar, I shared a fascination with manyastronomers, because it showed a simple beauty and complexity ofthe universe, and because we all wondered what tool for furtherinvestigation it would prove to be. Within months we heard thatthe two images of a distant quasar seen did not arrive at thesame time, meaning that there was a time delay between thearrival of the two images. and measurement of this time delaywould provide powerfully important information about thestructure of the universe. I immediately set out to measure thistime delay in fierce compeetition with several other researchgroups, and was the first to succeed in 1985. But although myresult was first confirmed in 1988 by another research group, itwas questioned by a famous astronomer in 1991 and I was beingshunned and ridiculed at research forums around the world.Finally the error of their result was recognized in 1996-97, andit is known that my original
determination of 1986 was and is correct.
So did I get what I wanted in life? Not really, because duringthe period of doubt I knew I was right and continued theinvestigation with better data, and found the answer to an evenbigger question: what is the nature and origin of the darkmatter? And so just as the world was acknowledging the success ofmy time delay determination, I was publishing a paper describingthe detection and nature of dark matter. Today that work iscontroversial but preliminary reports confirm the accuracy of mydata though the interpretation is still being checked. Am Isatisfied?
No, because now I am reaching farther still to understand thegrowth of structure in the universe, with a fluid dynamicsexpert. We are trying to understand why the universe has brokenitself 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 yetpublished) will I be happy? Probably not, because this discoveryraises even more questions. Maybe I really never wanteddiscovery; maybe I really just wanted controversey. But I don'tthink so. I don't think it takes a scientist to have ever morequestions. I think it is just human, and I present to you RudySchild, the human being.
Other windows will present the many objects of fascination inmy life. Below is a description of the meaning and significanceof my time delay discovery. In time I plan to write a moredetailed historical account; some might prefer that I don't.
A beautiful result of the Einstein General Theory ofRelativity is that the mass of any object can bend light, and ina few cases this is a large enough effect to be seen. The bestprospects are for a distant quasar acting like a light beacon,for a round galaxy between us and the quasar attracts the lightaround it, and we see not the quasars point image, but a smallring. But the foreground galaxy has to be exactly in the line ofsight to the quasar, which never happens, so in the more generalcase we see not a ring around the lens galaxy, but two pointimages, one on each side of the lens. About 50 examples of thisare now known, and are called multiple image gravitationallenses.
Before the first of these was found by Dennis Walsh in 1979,Sjur Refsdal noticed that the equations that described themultiple images and their relationship to the lens galaxy becameclosed if the time delay between the arrival of the two imagescould be measured. Thus it would be possible to measure the imageseparations and lens galaxy position, and the redshift distancesto the lens and quasar and from the time delay measurement wewould determine the distance of the quasar and lens in miles.From this miles distance and redshift distance we would determinethe expansion rate and age of the universe. Other methods tomeasure this, especially by Alan Sandage and Gustav Tammann, werecontroversial because in their methods the corrections for pastevolution of all their standard astronomical sources might comeinto play in ways too complex to understand. Our method wassimple and elegant, and independent of all the other measurementsbeing championed by others.
Because quasars all twinkle slightly, with brightness changesof a few percent occurring in a month, my method was to observethe pattern of brightness fluctuations in the first arrivingnorthern (A) image, and then look for the same pattern to arrivein the second arriving (B) image. Then the time between arrivalsof the twinkling pattern is the time delay. Many others tried todo the same thing, but the twinkling would need to be measuredfor years to recognize the patterns. By 1985 I had recognized thepatterns and with student Brian Cholfin I published the nowfamous paper that says that the pattern repeats itself in thesecond arriving image after 1.1 years.
With this time delay and the mathematical models describingthe lens positions and the gravitational fields, it has beenpossible to say that the universe is expanding at the rate of 64km/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 isbeing checked for more multiple image gravitational lenses, asmore time delays are now being measured.
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