Rotating Question Curious About Astronomy? Ask an Astronomer

What do "homogeneity" and "isotropy" mean?

Can you please give me the definitions of homogeneity and isotropy in astronomy terms?

This is a good question, because these concepts are a bit subtle. Homogeneous is defined as "the same in all locations" while isotropic means "the same in all directions." Imagine that the whole universe is an infinitely large field with one perfectly symmetrical hill, which you are seated atop. Look around: you see an isotropic universe, since the hill is equally green and equally steep in all directions. But the universe is not homogeneous: it has a hill!

These concepts are important because most modern cosmology is based on the "cosmological principle," the assumption that, on large scales, the universe is both homogeneous and isotropic. Studies of large-scale structure in the universe and analysis of the microwave background radiation help confirm that this assumption is justified.

March 2003, Kate Becker (more by Kate Becker) (Like this Answer)

Still Curious?

Get More 'Curious?' with Our New PODCAST:

Related questions:

More questions about Cosmology and the Big Bang: Previous | Next

How to ask a question:

If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.

Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist

URL: http://curious.astro.cornell.edu/question.php?number=508
This page has been accessed 30923 times since March 26, 2003.
Last modified: June 4, 2003 10:00:47 PM

Legal questions? See our copyright, disclaimer and privacy policy.
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.

Warning: Your browser is misbehaving! This page might look ugly. (Details)