Editing Nature (section)

==Matter and energy==
[[File:Hydrogen Density Plots.png|thumb|The first few [[hydrogen atom]] [[Atomic orbital|electron orbitals]] shown as cross-sections with color-coded probability density]]
{{Main|Matter|Energy}}
The [[natural science]]s view matter as obeying certain [[scientific law |laws of nature]] which [[scientists]] seek to understand.<ref name="COPL">{{cite book|last=Feynman|first=Richard|title=The Character of Physical Law|publisher=Modern Library|date=1965|isbn=978-0-679-60127-2}}</ref>
Matter is commonly defined as the substance of which physical objects are composed. It constitutes the [[observable universe]]. The visible components of the universe are now believed to compose only 4.9 percent of the total mass. The remainder is believed to consist of 26.8 percent [[cold dark matter]] and 68.3 percent [[dark energy]].<ref name="planck_overview">{{cite journal |title=Planck 2013 results. I. Overview of products and scientific results – Table 9. |journal=[[Astronomy and Astrophysics]] |first1=P. A. R. |last1=Ade |first2=N. |last2=Aghanim |author2-link=Nabila Aghanim|first3=C. |last3=Armitage-Caplan |last4=et al. (Planck Collaboration) |date=March 22, 2013 |arxiv=1303.5062|bibcode = 2014A&A...571A...1P |doi=10.1051/0004-6361/201321529 |volume=571 |pages=A1|s2cid=218716838 }}</ref> The exact arrangement of these components is still unknown and is under intensive investigation by physicists.

The behaviour of matter and energy throughout the observable universe appears to follow well-defined [[physical law]]s. These laws have been employed to produce [[Physical cosmology|cosmological]] models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty [[physical constant]]s<ref>{{cite web|last = Taylor|first = Barry N.|date = 1971|url = http://www.physics.nist.gov/cuu/Constants/introduction.html|title = Introduction to the constants for nonexperts|publisher = National Institute of Standards and Technology|access-date = January 7, 2007|archive-url = https://web.archive.org/web/20070107012004/http://physics.nist.gov/cuu/Constants/introduction.html|archive-date = January 7, 2007|url-status = dead|df = mdy-all}}</ref> that appear to be static across the observable universe.<ref>{{cite journal|author=Varshalovich, D.A.|author2=Potekhin, A.Y.|author3=Ivanchik, A.V. |name-list-style=amp|title=Testing cosmological variability of fundamental constants|journal=AIP Conference Proceedings|date=2000|volume=506|page=503|arxiv=physics/0004062|doi=10.1063/1.1302777|bibcode=2000AIPC..506..503V|citeseerx=10.1.1.43.6877}}</ref> The values of these constants have been carefully measured, but the reason for their specific values remains a mystery.