{"id":7906,"date":"2026-08-22T17:40:12","date_gmt":"2026-08-23T00:40:12","guid":{"rendered":"https:\/\/cosmologyscience.com\/cosblog\/?p=7906"},"modified":"2026-08-25T19:29:47","modified_gmt":"2026-08-26T02:29:47","slug":"how-do-we-measure-cosmological-distances","status":"publish","type":"post","link":"https:\/\/cosmologyscience.com\/cosblog\/how-do-we-measure-cosmological-distances\/","title":{"rendered":"How do we Measure Cosmological Distances ?"},"content":{"rendered":"

How do we Measure Cosmological Distances ?<\/strong><\/p>\n

(c) Copyright 2026 David j Dilworth<\/p>\n

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Redshift – showing how Emission Lines Move after “light” crosses our Universe<\/strong><\/p><\/div>\n

The most credible method we use to measure the farthest distances<\/strong><\/em> in cosmology is called Redshift.<\/strong><\/a><\/p>\n

Redshift is the movement of spectral lines in a graph from cool to warmer colors; from Blue to Red. It represents the “warming” of light as it transits our non-so-local universe.<\/p>\n

But the photons don’t really warm up. They actually cool in their transit of cosmological distances. The light (electromagnetic radiation) loses energy.<\/strong> Thus arose the term “Tired-Light.<\/a><\/strong>”<\/p>\n

Redshift occurs when spectral-lines (emission or absorption lines) of light or other electromagnetic radiation from astrophysical objects (typically galaxies) shows up in longer wavelengths than normal (compared to those in a laboratory experiment). This is likely a result of energy loss.<\/p>\n

All the light and other electromagnetic radiation from a given source are redshifted about the same amount. So we have to measure the absolute wavelength of the spectral-lines to discern how far they’ve moved.<\/p>\n

Redshift is the primary measuring “stick” used to estimate cosmological distances. Spectral-line Redshift is measured several ways, in several wavelength bands (but surprisingly rarely in the visible light range<\/strong>), has a huge variance<\/strong> that is not widely discussed, and is apparently caused by several independent phenomena.<\/p>\n

Blueshift<\/a><\/strong> is the reverse – when spectral lines move towards shorter wavelengths apparently meaning an increase in radiation energy. Blueshift has been observed in radiation emitted by stars and galaxies. There are quite a few (at least 600, possibly almost 7,000) generally nearby galaxies exhibiting Blueshift.<\/p>\n

To credibly verify redshift we start by measuring distances to closer objects, then climb up the “Distance ladder” until we reach redshift distances.<\/p>\n

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Cosmology Distance Measuring Methods<\/strong><\/p><\/div>\n

The closest astronomical measuring sticks we use are Radar Ranging and Parallax<\/a>.<\/strong><\/p>\n

Parallax uses trigonometry to see how much a star moves when photographed extremely precisely against its background star-field. We take a picture in January and another in July. Then compare how much movement occurred between the two. We do it again next year, to see if the star has measureably moved. Then we take the angle of change, and using trigonometry we get an amazingly good estimate of its distance.<\/p>\n

Next method, we move out to Cepheid Variable<\/strong><\/a> stars. They have a specific brightness variation directly related to their pulsation periods<\/span>. By measuring their brightness, it gives us a good estimate of their distance. Dimmer pulses = farther away.<\/p>\n

And so on.<\/p>\n

Some people would have you believe they can measure galaxy distance “Precisely” using a complex, tortured set of reasoning based on a likely fiction called Microwave “Background.” Not really. Parallax, the most accurate and closest distance measurement, is only reliable out to about 10% variability. The farther the object, the bigger the uncertainty and variability.<\/p>\n

Did you know there are two kinds of Redshift?<\/strong><\/p>\n

1) The primary Spectral-Line Redshift<\/strong> method uses prisms to spread out the distant galaxy photons into a rainbow spectrograph. That’s the reliable one. It is sometimes called “long slit spectroscopy.”<\/p>\n

It measures how far the Hydrogen 21 centimeter line (1420.4 MHz) moves from its laboratory location in a spectrum.<\/strong> It has been found at frequencies from 200 MHz to about 15 MHz from observations here on Earth.<\/p>\n

Neutral hydrogen atoms emit radiation at an exquisitely precise frequency: 1420.40 MHz.<\/strong> Astronomers call it the hydrogen line. We fairly safely assume this occurs identically everywhere across our universe.<\/p>\n

2) Photometry<\/strong> is the other Redshift method. It just uses color, not a spectrograph or measuring spectral-line wavelengths. Simply, Red galaxies are farther than white or blue galaxies. This method is not nearly as credible. Quite a bit less. But its tons faster and cheaper than the Rainbow spectrum method.<\/p>\n

The Sloan Digital Sky Survey<\/a> mainly used the second method to measure more than 4 million galaxies and a billion objects.<\/strong><\/p>\n

Contrast that with the spectral line method where a single Spectral-Line Redshift<\/strong> measurement can take a good astronomer at least 20 minutes. Measuring a distant galaxy can take an hour or more.<\/strong><\/a><\/p>\n

Importance:<\/strong><\/p>\n

The interpretation of Redshift as Universe “expansion” is the primary support for Big Bang models.<\/p>\n

It is important to recognize that Redshift measuring distance is one of the few things in Cosmology that has little dispute.<\/strong><\/p>\n

However, using that same Redshift to mean Universe Expansion<\/a><\/strong> – is highly controversial.<\/p>\n

# # #<\/p>\n

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How do we Measure Cosmological Distances ? (c) Copyright 2026 David j Dilworth The most credible method we use to measure the farthest distances in cosmology is called Redshift. Redshift is the movement of spectral lines in a graph from … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":0,"footnotes":"","_links_to":"","_links_to_target":""},"categories":[13],"tags":[],"class_list":["post-7906","post","type-post","status-publish","format-standard","hentry","category-basic-science"],"_links":{"self":[{"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/posts\/7906","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/comments?post=7906"}],"version-history":[{"count":20,"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/posts\/7906\/revisions"}],"predecessor-version":[{"id":7929,"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/posts\/7906\/revisions\/7929"}],"wp:attachment":[{"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/media?parent=7906"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/categories?post=7906"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cosmologyscience.com\/cosblog\/wp-json\/wp\/v2\/tags?post=7906"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}