Rotating Question Curious About Astronomy? Ask an Astronomer

What makes up most of the Universe?

For a long time, astronomers thought that almost all of the Universe was made of regular matter (called "baryonic matter". It is the same kind of matter that makes up everything on earth and all the stars (protons, neutrons and electrons)). However, they have now found out that this baryonic matter was only a small fraction of the matter in the Universe.

By measuring the motion of galaxies, and of stars inside galaxies, astronomers have been able to determine that there exists also some matter that we cannot see. They know that because even though they cannot see it, they measure the effects of their gravity on these stars and planets. This is what we called "dark matter".

There is also something that makes up most of the Universe and that we refer to as "dark energy". The nature of this dark energy is completely unknown, but we know it behaves quite differently from regular matter. It is believed it has an opposite effect to gravity pushing everything apart and thus contributing to the expansion of the Universe.

Very recent observations of the Cosmic Microwave Background have revealed the relative fractions of each of these components. The best estimates now say that the Universe is made of 4% regular baryonic matter, 23% dark matter and 73% dark energy.

Contents of the Universe according to WMAP
Credit: WMAP

February 2003, Amelie Saintonge (more by Amelie Saintonge) (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=468
This page has been accessed 58753 times since February 18, 2003.
Last modified: February 13, 2004 11:47:58 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)