When they say that the age of the Universe is about 13.7 billion years, they are giving the age in cosmic time, is that right?. There's this other thing called conformal time which I don't understand. What would be the age of the Universe measured in conformal time?
What is the relationship between redshift and conformal time ?   For example in a paper i found:   taking $z_e = 3234 $ at the time of radiaton-matter equality yields the conformal time $\frac{\eta_e}{\eta_0} = 0.007$ and taking $z_E=0.39$ at matter-$\Lambda$ equality yields $\frac{\eta_E}{\eta_0}=0.894$ and setting redshift at decoupling $z_d=1089$ yields $\frac{\eta_d}{\eta_0} = 0.0195$  where $\eta_0$ is the present decoupling time.  Further some cosmological parameters are given as :  $\Omega_r = 8.36 \times 10^{-5}, \Omega_m = \Omega_b + \Omega_{dm} = 0.044 +0.226, \Omega_\Lambda = 0.73,  H_0=0.72$  Now how can i calculate all those $\eta_e, \eta_E, \eta_d, \eta_0$ from given redshift values and/or above parameters ? I searched whole of my text books trying to find an explicit relation for conformal time $\eta$ but all i got was $ \mathrm{d}t=a(t)\mathrm{d}\eta$. Any help would be very helpful.
Network-wide Help Center bug How to add a vertical line to a plot I went to the doctor's I saw the sentence like     Donald Trump to run for president next month.   in the newspaper on the internet.  But I don't know why we have to use to instead of will.  Is there any rule I don't know?  Can anyone tell me the reason why we should use to in the news? Currently, a user does not get any notification when a trivial edit (less than 6 characters, by a user who has the ) is made on one of his/her posts. As in .  Even though the user is trust-worthy (owing to the rep of the user), wouldn't it be nice for the OP to get a notification whenever an edit is made, even trivial? Can regular expressions be used to match nested patterns? Why does triply periodic univariate function not exist? A univariate function $f$ is periodic with period $p_1,\ldots,p_k$ if   $$f(z) = f(z + \sum_{i=1}^k n_i \cdot p_i)$$   for all complex $z$ and integers $n_i$. Elliptic function is an example of doubly periodic function.  that a triply periodic univariate function cannot exist, but why? Can't we follow the construction of elliptic functions that uses Schwarz-Christoffel formula to map upper-plane onto a triangle, and use the reflection principle to create a lattice which corresponds to three periods?     Which step fails to hold when we mimic the construction of an elliptic function to create a triply period meromorphic univariate function?   Sorry if the question is stupid. I do not have an access to the original proof that a triply periodic function cannot exist, either. So references are welcome! How to update a pull request from forked repo? Invoking JavaScript code in an iframe from the parent page Basically, I have an iframe embedded in a page and the iframe has some  routines I need to invoke from the parent page.  Now the opposite is quite simple as you only need to call parent.functionName(), but unfortunately, I need exactly the opposite of that.  Please note that my problem is not changing the source  of the iframe, but invoking a function defined in the iframe. Simulation of interacting particles What's the best option to display Unicode text (hebrew, etc.) in VB6 I have some customers who want to use our speech therapy software in Hebrew.  The programs are in VB6. The best option I'm aware of are:   use the Forms 2.0 controls from MS Office, but you can't distribute them.    $899   $499   Any other options? Is there any way to make a method with more than one instance? If I take a loss when I sell my car, can I claim a capital loss deduction on my income tax return? If you activated a free upgrade to Windows 10 or bought and activated   Windows 10 from the Microsoft Store, you have a digital license for   your device. This means you can reinstall the same edition of Windows   10 that your device has a digital license for without entering a   product key. During reinstallation, if you’re asked to enter a product   key, you can skip this step. Windows 10 will automatically activate   online after the installation is complete.   source:   Does MS digital license 'fingerprint' hardware information  during the free upgrade / activation and store it (at Microsoft) , so that the next re-install queries MS for the fingerprint and activates Windows 10?  Thought the disk drive may change, I expect that none of the other fingerprinted hardware will change. coloring the page numbers in the table of contents What Do the Gringotts Goblins Do With Muggle Money? ‘But you’re Muggles!’ said Mr Weasley delightedly. ‘We must have a drink! What’s that you’ve got there? Oh, you’re changing Muggle money. Molly, look!’ He pointed excitedly at the ten-pound notes in Mr Granger’s hand.   Chamber of Secrets - page 47 - UK Hardcover - chapter 4, Flourish and Blotts   So Gringotts exchanges Muggle money for Wizarding money. What do the Goblins do with the Muggle money after the exchange has been made? Is it possible they keep a stash of Muggle money on hand for reverse exchange purposes, or do they surreptitiously feed the money back into the Muggle economy?  What do Goblins do with Muggle money? Impose strict time-limit for questions on Hot Network Questions list What should be the default title case for non-technical questions? As an example, this question is titled using sentence case. I've been going to lots of different meta sites (especially this one), and I think the needle bent on my oh-me-oh-my-my-ocd-oh-meter.  Can we please standardize on using either:   Sentence case Title Case AP Style Title Case   ... and then we can look at just converting titles automatically? This would be a switch, of course, but I'd only imagine turning it off on sites where program code or symbols might be present in titles. Or, it could just become part of editing guidelines.    Additionally, is this a horrible idea?   To see the differences between them, you can put any arbitrary title into  (we have no affiliation with them, it's just a tool I sometimes recommend to people).  We would also eventually adopt this for static routes, but I'm mostly talking about questions. How can I run a command after boot? I would like to run the simple shell command echo 1 &gt; /proc/sys/kernel/sysrq at each boot, to enable the sysrq keys. When in boot should this be done, and where should I put a script to do it? Where can I ask questions regarding Electronics?