1 00:00:00,012 --> 00:00:04,632 So, constraints from Big Bang nucleosynthesis from type 1A super novae 2 00:00:04,632 --> 00:00:09,662 surveys from the cosmic background and from many other sources have been put 3 00:00:09,662 --> 00:00:14,886 together into this best fit that tells us the parameters of our universe, which I 4 00:00:14,886 --> 00:00:18,016 used as input for my description of the history. 5 00:00:18,016 --> 00:00:21,833 So, let's see how these parameters are put together. 6 00:00:21,833 --> 00:00:29,117 what we see here is a plot of matter density today versus cosmological dark 7 00:00:29,117 --> 00:00:34,679 energy density today. the line here is the line diagonal where 8 00:00:34,679 --> 00:00:40,700 the sum of the two densities is one. Remember, that's total energy density one 9 00:00:40,700 --> 00:00:46,580 that corresponds to flat universes. Above it, we have positively curved universes, 10 00:00:46,580 --> 00:00:53,608 below it negatively curved universes. And these concentric curves are, are curves 11 00:00:53,608 --> 00:01:00,499 of within which, outside of which you can exclude being with increasing certainty 12 00:01:00,499 --> 00:01:06,154 based on various measurements. So, for example, the Super Nova survey, 13 00:01:06,154 --> 00:01:12,262 remember, was measuring the deceleration parameter, if you remember, that 14 00:01:12,262 --> 00:01:19,557 corresponded to rho plus 3p/c^2 which ended up being half of the density of 15 00:01:19,557 --> 00:01:25,542 dust plus the density of radiation, which is irrelevant, minus the density of dark 16 00:01:25,542 --> 00:01:28,937 energy. And so, that's the slope of this graph. 17 00:01:28,937 --> 00:01:35,107 We get a very good measurement of this quantity in this direction, but we get a 18 00:01:35,107 --> 00:01:38,307 less of a sensitivity to the sum of this plus that. 19 00:01:38,307 --> 00:01:44,400 Because if you increase the matter density and also increase the dark energy 20 00:01:44,400 --> 00:01:47,675 density, the deceleration parameter doesn't change much. 21 00:01:47,675 --> 00:01:51,746 So, the supernovae give us a good constraint in this direction but now much 22 00:01:51,746 --> 00:01:55,035 in this direction. On the other hand, the cosmic microwave 23 00:01:55,035 --> 00:01:59,203 background data is pretty much sensitive to the total density. Remember, we 24 00:01:59,203 --> 00:02:03,382 measure the flatness of the universe, it lays us pretty much on this line. 25 00:02:03,382 --> 00:02:08,629 Happily, these two are crossed and so between them they produce a very good 26 00:02:08,629 --> 00:02:13,544 prediction. this is additional data sensitive mostly 27 00:02:13,544 --> 00:02:19,497 to the density of dust because this has to do with looking at the galactic 28 00:02:19,497 --> 00:02:25,503 distribution and corelations in distances and that's similar to the way we studied 29 00:02:25,503 --> 00:02:30,087 the acoustic sound waves in the primordial plasma. And again, this is 30 00:02:30,087 --> 00:02:35,672 supposed to track the wavelengths and fluctuations in the dark matter density. 31 00:02:35,672 --> 00:02:39,329 And so this gives us a third and consistent constraint. 32 00:02:39,329 --> 00:02:44,149 There are many other observations that go into the pot when making our best 33 00:02:44,149 --> 00:02:48,672 estimate, but you see that we have both consistent and rather precise 34 00:02:48,672 --> 00:02:53,417 determination of the parameters of our universe, and you see that we predicted 35 00:02:53,417 --> 00:02:58,342 arc energy of about 0.75 of the critical density and a matter density of about 36 00:02:58,342 --> 00:03:03,296 0.25 of the critical density, of which, remember, we have restrictions, let's 37 00:03:03,296 --> 00:03:07,654 say, at most 5% is visible matter, so the rest are baryonic matter. 38 00:03:07,654 --> 00:03:12,445 That's from among other things, baryogenesis and also the details of the 39 00:03:12,445 --> 00:03:16,701 cosmic microwave background. So, we predict that the rest is dark and 40 00:03:16,701 --> 00:03:19,472 we do know exactly what our universe is made of. 41 00:03:19,472 --> 00:03:20,751 That's quite exciting.