Автор: How about . RIGHT NOW! I’ll use a shorthand for t = now by placing a zero subscript on quantities; that turns H(t) into H0, which iliar to you.
The latest vital occurrence is an important well worth, in case one to determine they from inside the grams per cc otherwise kg for each meter cubed or atoms for each and every cubic meter, it always seems to encompass a large bad exponent. For comfort, cosmologists have a tendency to talk about the matter occurrence in the a member cosas para saber al salir con un barbudo of family means:
. although end is quite obvious: it isn’t nearby the important really worth. That means that whether your market is as simple as we now have thought, it does develop permanently.
Yardseasuring brand new development of size factor
Ok, therefore we have a very good qualitative perception for the future of our very own (very simplified) universe; will we ensure it is alot more quantitative? We understand how quickly new world try growing here and today, so we have some steps of your own thickness of amount; it means we must be able to compute the near future rate off expansion and you may measurements of the fresh market, right?
Right. Let’s come back to a young particular brand new «opportunity equation» for a fork out of number regarding consistent market.
New thickness away from matter does change over the years, while the measure basis really does change in the long run . although total quantity of count in shell does not change with time.
Better, there it is: a good differential picture with the level basis and its particular basic derivative. We realize the worth of the dimensions foundation today, in addition to worthy of on price of alter now, thus, in theory, we must be able to compute the worth of this new measure foundation when it comes to random time in the near future or the earlier. Yes, we would perhaps not know exactly what the worth of the continual on the right-hand front side are, however, we could figure out the end result per of selection.
k > 0 In this situation, this new shell regarding number will ultimately stop increasing and you will collapse on alone. Writing the clear answer in analytic form isn’t so very hard in the event the i choose an excellent parametric method.
k = 0 In this situation, the newest layer off amount can’t ever stop increasing, however it tend to asymptotically strategy no speed.
k < 0 In this case, the shell of matter expands forever and does not approach zero speed. Again, a parametric solution is not hard to write:
Below is a graph showing the evolution of the scale factor as a function of time for three choices of ?M. On the horizontal axis is time, but the units aren’t seconds or years or gigayears; instead, they are in «Hubble time» units. One «Hubble time» is simply the reciprocal of the current value of the Hubble parameter. For rough purposes, one call say that one Hubble time is about 10 Gyr, for the current universe in which we live.
Regardless if for each universe provides an extremely additional measure factor in this new much future, it’s just not easy to identify him or her in both new near upcoming, or — more critical — throughout the close earlier in the day.
Including redshift into mix
So, we have a method to define the scale basis just like the an excellent reason for big date. That’s great, however it cannot really assist observational astronomers. Whenever we grab photo and spectra regarding distant stuff, do not rating a timestamp telling us in the event the light was emitted. However, we Do get one piece of data and this confides in us something equal to date: the new redshift z.
The redshift is oftentimes conveyed with regards to the produced and you will noticed wavelengths off white, nevertheless can just as well be printed in regards to the scale items at the time of emission and you may observance.
