Mysteries of the Universe : Distances are VERY difficult to determine in Astronomy.

Every method has weaknesses and flaws. And there is also the error bar underestimation problem. Every published measurement contains error bars and estimates, yet history has show that the errors are almost always underestimated.

There is no such thing as distance measurement in Astronomy outside of parallax. Distance estimates are often crude and contradictory. This is not a failing on the part of astronomers or their equipment, but rather the fundamental difficulty of the problem.

Estimates should be taken as accurate only when several groups using different methods come up with compatible values.

This is true of many astronomical estimates. For example, there is a big dispute today on the value of the Hubble Constant. There are two different values which exclude each other by their claimed error bars. Somebody is wrong in an essential way.

Remember, the Universe is colossal and very old and we are little bugs on a tiny rock with very short lifetimes. These problems will take centuries or even millennia to resolve.

DFM