Parallax Technique?

Question

This is a question form my textbook. How do we describe the parallax technique for measuring the distance to the stars.

Can someone help me out? I don't know a lot about the parallax technique

Answer 1

Parallax is the displacement of two objects in relation to each other when you change your point of view, and it depends on the distance to those objects. By measuring this displacement, astronomers can measure how far those stars are.

Answer 2

The parallax technique calculates distance by examining the difference between two images of the same object taken from different locations.  The is the exact same way your eyes see in 3-D.  If you hold your finger out in fron of you and look thru one eye and then the other, you will see your finger move in relation to the background.  The more an object's location  appears to offset when viewed from another location, the closer the object is.

The first accurate measurements of the distance to the moon were taken by examing two pictures of the moon (and the stars behind it) from different locations on the Earth.

The parallax technique also works to determine the distance to nearby stars, by examining photographs taken while the Earth is on opposite sides of the sun.  Since the photos are taken from almost 200 million miles apart, the closer stars show a parallax shift in relation to the much more distant stars.

Answer 3

Ah, I see that someone already answered by quoting Wikipedia. But that's no fun; I will try to answer from memory at the risk of making a fool of myself! :-)

You see, by observing something at two different places then using simple trigonometry, you can estimate a distance. That's what seafarers did in the pre-GPS days and they called it a running fix because the same object (e.g. a lighthouse) was observed twice at two different places and different time.

You can do that in order to e.g. estimate the distance to the moon. But you can't for things like stars and galaxies; they are much too far away and the parallax angle much too small to be measurable.

From an historical point of view, the problem must certainly have been to observe say the moon's elevation over the horizon at the same longitude and at the same time.

Because until the creation of the marine chronometer by John Harrison in the late 18th century, there was no accurate way to measure longitude and time. Longitude actually being a time angle compared to a place of reference: the Greenwich prime meridian.