Alain Connes: " **a noncommutative algebra creates its own intrinsic time** ". First of all, as Yemon Choi commented, this quote of Alain Connes is a slogan, not a theorem. " There are NC algebras creating their own intrinsic time " would be more correct, and more precisely: *Theorem*: a *von Neumann* algebra *of type $\rm III$* creates its own intrinsic time *up to inner automorphism*. Anyway, from a noncommutative (associative) algebra $\mathcal{A}$ (with a countable base $\mathcal{b}$) on the field $\mathbb{C}$ , we can generate a von Neumann algebra as follows: let $H = l^2(\mathcal{b})$ be the Hilbert space generated by $\mathcal{b}$, then $\mathcal{A}$ admits a faithful representation $\rho$ on $H$ by left multiplication (the regular representation). *If* $\forall a \in \mathcal{A}, \ \rho(a)$ is bounded, then $\mathcal{M} = (\rho(\mathcal{A}) \cup \rho(\mathcal{A})^*)''$ is the von Neumann algebra generated by $\mathcal{A}$ (*else*, by the [polar decomposition][1], $\rho(a) = u. \vert \rho(a) \vert$ with $u$ a partial isometry, and $\mathcal{M}$ is the von Neumann algebra generated by these partial isometries). Note that $a \to a^*$ is the involution and $\mathcal{E}''= (\mathcal{E}')'$, is the bicommutant of $\mathcal{E} \subset B(H)$ the algebra of bounded operators. A von Neumann algebra $\mathcal{M}$ is a factor iff its center is trivial: $\mathcal{M} \cap \mathcal{M}' = \mathbb{C}$. Every von Neumann algebra $\mathcal{M}$ decomposes as a direct integral of factors (Murray - von Neumann). There are three types of factors: a factor is type $\rm I$ *if* it admits projections with a finite dim. range; *else* it is type $\rm II$ *if* it admits no projection equivalent to an own subprojection; *else* it is type $\rm III$ (and we can prove that all the projections are equivalent). *Modular theory* : Let $\mathcal{M}\subset B(H)$ be a von Neumann algebra. Let $\Omega \in H$ be a *cyclic* and *separating* vector (i.e., $\mathcal{M}.\Omega$ and $\mathcal{M}'.\Omega$ are dense in $H$). Let $S : H \to H$ be the closure of the anti-linear map $a\Omega \to a^{*}\Omega$, it admits a polar decomposition $S = J\Delta^{1/2}$, with $J$ anti-linear unitary and $\Delta$ positive. $JMJ = \mathcal{M}'$, $\Delta^{it} \mathcal{M}\Delta^{-it} = \mathcal{M}$ and $\sigma_{\Omega}^{t}(a) = \Delta^{it} a \Delta^{-it}$ gives the modular action of $\mathbb{R}$ on $\mathcal{M}$. *NC Radon-Nikodym theorem*: Let $\Omega'$ be another vacuum vector, then there exists a Radon-Nikodym map $u_{t} \in \mathcal{U} ( \mathcal{M})$, define such that $u_{t+s} = u_{t} \sigma_{t}^{\Omega'} (u_{s})$ and $\sigma_{t}^{\Omega'} (x) = u_{t} \sigma_{t}^{\Omega}(x) u^{\star}_{t}$. Then, modulo $Inn(\mathcal{M})$, $\sigma_{t}^{\Omega} $ is independent of the choice of $\Omega$, ie, there exist an intrinsic $\delta : \mathbb{R} \to Out (\mathcal{M})$ with $Out (\mathcal{M}) = Aut(\mathcal{M})/Inn(\mathcal{M})$. What Alain Connes calls **the own intrinsic time**, is precisely $\delta$. On type $\rm I$ or $\rm II$ the modular action is inner, and so $\delta$ trivial. It's non-trivial for the type $\rm III$. *Remark*: the type $\rm III$ factors exist, moreover, in some sense, most of the factors are type $\rm III$. *Advertising*: There will have a [Master Class in Modular Theory][2] by [Serban Stratila][3] and [Masamichi Takesaki][4], at Chennai (India) from 24 Nov. to 04 Dec. 2014. [1]: http://en.wikipedia.org/wiki/Polar_decomposition [2]: http://www.imsc.res.in/~sunder/smpost.pdf [3]: http://www.humboldt-club.infim.ro/public_html/MEMBERS/PAGES/stratila.htm [4]: http://en.wikipedia.org/wiki/Masamichi_Takesaki