Wobbly Distance Ladder
Credit: George Rieke.
Steward Observatory, University of Arizona.
After a cartoon by Wojtek Kozak.
Undoubtedly we will continue to see improvements in many techniques involved in the Cosmic Distance Ladder. And new techniques are being investigated.
In the close range, measurements by the GAIA spacecraft are making major contributions to the accuracy and range of the method of parallax. In the medium range better observation techniques improve the standard candle of Cepheid variable stars and further afield the value and accuracy of Hubble’s parameter is likely to improve.
However some “standard” candles may turn out not to be so standard after all. The problems of calibration between the various distance measurement techniques will continue to form a large obstacle, because of the lack of distance indicators that work on overlapping distances.
Measuring accurate distances remains one of the biggest technical problems in astronomy.