How much matter does the universe contain?

A single look at the night sky will reveal there's far more nothing than something out there. The tiny specks of light are stars, made of something, and the vast oceans of blackness surrounding them are nothing. The universe contains gigantic amounts of void, but how much, I wonder. To visualise this, I decided to picture all the matter in the universe clumped together. Not super-tightly, like in a neutron star, but still put together closely so that the density is 1 kilogram per litre: the density of water. The main reason I chose this density is, of course, that it makes it very easy to calculate. So if we pack all matter in the universe together like this, is the result larger or smaller than a single galaxy?


Before I answer this question, I should point out I will give large numbers first in the scientific notation, then give their name according to the long scale. I'm using the long scale because it's more sensible and because it's the scale I grew up with using. But for people who are more keen on the short scale (the one generally used in English-speaking countries) I will put the short scale name of large numbers in parentheses. A second thing I should point out is that I'll be using all the matter in the observable universe, not the entire universe.

First of all, we have to find out the total mass of matter in the universe. Wikipedia gives several estimates of the mass of the universe. I will be using the calculated mass based on the critical density, 1.53×10⁵³ kg, as it seems to be the best corresponding to our observations of the universe. Basing the mass of the universe on stars alone is silly due to the presence of dark matter, and assuming a steady state-universe requires the pretty big assumption that our universe is a steady-state universe.

So, since we assumed the density of water for our clump of all matter, that means it's 1.53×10⁵³ litres in volume. 153 octilliard (153 septendecillion) litres is unimaginably huge, so we'll have to use bigger units to make this more imaginable. Let's start with converting to cubic metres. Thanks to space being three-dimensional, a cubic metre contains not ten, but a thousand litres. So that means this clump of matter is  1.53×10⁵⁰, 153 octillion (153 sexdecillion) cubic metres in volume.

We can get closer to imaginable numbers by converting to cubic kilometres. Similarly to how a cubic metre contains a thousand litres, a cubic kilometre contains a milliard (billion) cubic metres. That means our clump of all matter is 1.53×10⁴¹, 153 sextilliard (153 duodecillion) cubic kilometres.

To get closer to home, we'll convert to cubic megametres. The megametre is a pretty rarely used unit, but it's equal to a thousand kilometres. The clump of matter has a volume of 1.53×10³², 153 quintillion (153 nonillion) cubic megametres.

To take another step, I'll now convert to cubic gigametres. A gigametre is a million kilometres, a bit more than a journey to the moon and back. We divide by a milliard (billion) and get 1.53×10²³,153 trilliard (153 sextillion) cubic gigametres.

We're still not using imaginable numbers, so we convert to cubic terametres. A terametre is a milliard (billion) kilometres, 1.5 times the distance from here to Jupiter. The clump of matter is 1.53×10¹⁴,153 billion (153 trillion) terametres. Hey, that's approaching numbers we use (on occasion) in our daily lives.

But let's take another step and convert to petametres, one billion (trillion) kilometres. I would like to give an example of how big this is, but there are few meaningful distances close to a petametre. It's 220 times the distance from here to Neptune, or a fiftieth of the distance from here to the nearest star (aside from the Sun). All the matter in the universe taken together is, if my calculations are right, 1.53×10⁵, 153000 cubic petametres.

While a hundred-and-fifty-thousand is quite a low number, we can use cubic lightyears instead. A lightyear is approximately ten petametres. Actually, it's 9,5 petametres, but considering how rough our estimate of the universe's mass was I think we can get away with rounding it to ten, thus putting a thousand cubic petametres in a cubic lightyear. One final calculation, and we get 153 cubic lightyears. A cuboid of five by five by a little over six lightyears. That's all the matter in the universe. Not only would it fit inside a single galaxy, if its centre was at the Sun's position it wouldn't even reach the nearest star. That's all the matter in the universe, everything else is void.

But where is all this void exactly? You might think the gigantic gaps between galaxies are where it is, but these are actually relatively small. The Milky Way is a hundred thousand lightyears across, though only ten thousand lightyeard thick, and the nearest big galaxy is at two million lightyears, only twenty times the Milky Way's own diameter. If we count dwarf galaxies the nearest other galaxy is much closer even. If you imagined the big galaxies as coins, they would be less than a metre apart.

The real distances that are responsible for all this void are the distances between stars. When I tried to give an example of the size of a petametre and failed we already saw there is a huge gap between distances within a solar system and distances between stars. Our Sun is 1.4 million kilometres across, but the nearest other star is more than four lightyears away. If we imagine the Sun as a grape in the centre of Amsterdam, the nearest starsystem consists of two grapes and a grain of pepper located near Brussels. And that's a good comparison for interstellar distances: a piece of fruit in every European capital. Those distances are mainly responsible for the huge amounts of void in the universe.

Winter solstice

Winter solstice just passed (At 23:38 UTC, to be precise). That means the Earth has just passed the point in its orbit where the North Pole is pointing farthest away from the Sun, and as such it's the longest night on the northern hemisphere (And of course 21 and 22 December are logically this year's shortest days, with the Sun lowest on the sky thanks to that). From now on, the Sun will be getting higher and higher in the sky and the days will get longer and the nights shorter.

Yet, strangely, winter has officially only just started. I think it's kind of weird that the season we generally identify will cold and snow and the sort is actually the season where the Sun is climbing higher. This kind of weird placement of the seasons also means most of March is in the winter, even though the weather frequently can get very warm in March. If I had designed the seasons, I wouldn't have had them go from solstice to equinox or equinox to solstice, but I would have had the solstices and equinoces in the middle of each season: Winter would be from 6 November to 6 February, Spring would be from 6 February to 6 May, Summer from 6 May to 6 August, and Autumn from 6 August to 6 November. Like that, the seasons would follow the weather and the position of the Sun much better than the system we use now.

Anyway, spare a thought for the poor people living on the tropic of capricorn who now have the Sun shine from straight above them. Must be awfully warm, and frankly I greatly prefer the cold and snow we are experiencing over here.

The Vatican feels offended

http://www.rte.ie/news/2010/1211/abuse.html
Apparently the Vatican felt offended by the investigations into the child abuse that came to light last year. Are they fucking kidding? They swore the victims to secrecy and transferred the rapists to protect them from the law, and they have the nerve to be offended by a investigation?
Personally, I feel offended too, but by the fact that every civilised country on the planet didn't immediately break up and outlaw the catholic church, as that is exactly what would have happened if it had been a secular organisation (say an orphanage or a school) that covered up for their members who had raped children placed in their care.
Now, someone might say "Well, closing down the catholic church would be going against freedom of religion." No, it wouldn't, as no one would be forced to renounce their catholicism (that would be a very nasty thing, indeed), it's just the organisation I'm talking about.
Let us also not forget that this was hardly the first misdeed the church committed. There's their denial of condoms protecting against AIDS (To anyone who thinks that, there is a real easy way to test this: the HIV virus is about 500 times the size of an oxygen molecule. If you're right, that means oxygen could easily move through a condom. Please pull a condom over your head and see what happens.), which contributes to the immense spread of AIDS in Africa. There's their continuing discrimination against women and homosexuals, their condemning of contraceptives, contributing to overpopulation and poverty, their remaining silent during the Holocaust, and of course there's older crimes like the Crusades, Inquisition, and suppression of early science.