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70,000,000,000,000,000,000,000 Stars Out There
ChopsMIDI writes "Ever wanted to wish upon a star? Well, you have 70,000 million million million to choose from. That's the total number of stars in the known universe, according to a study by Australian astronomers. It's also about 10 times as many stars as grains of sand on all the world's beaches and deserts."
Ahh yes, but the space-time window in which we're viewing is very, very, very, very, very, very (get the picture?) recent and equally narrow.
:)
If you're into this subject, I suggest reading "Hyperspace" by Michio Kaku. Good book, and he's got at least a chapter on the statistical analysis of the existance of life in the Universe. Very good book all around
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I bought Hyperspace used and it is indeed a very thought provoking reading. There are probably some newer theories that aren't discussed in the book, but it's still pretty decent popular science. One thing I didn't like about it is in some parts the author seems to try to aggressively imply that there is proof that God doesn't exist, when of course, such proof is currently impossible to obtain using current methods and technology, as is proof that God does exist.
It's quite similar to what SCO is trying to do. Some scientists and others apparently believed that if they say it loud enough long enough, eventually it will be accepted as truth. Guess what: in large part, it worked. In reality, there cannot be a proof for everyone that God does or does not exist. The only way to find out is to look for yourself.
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That's almost spooky... Avogadro's number is approximately 600 sextillion.
:)
What if it turns out that, after taking into account all the dark matter, the universe contains Avogadro's number of "large objects"? (stars, planets, whatever)
Could the universe turn out to be nothing more than one mole of stars?
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I find it interesting that they determined an estimate of the total mass of all the matter in the Universe before they figured out how many stars there are. You'd think they'd come up with the number of stars first, and then base the mass estimate on that.
You are right in thinking that intuitively, this would be the way to work it. (I know that it would be if I were approaching it, but then these guys are probably smarter than me.) The interesting thing is that as part of the work Einstein did, there was a mathematical shortcut which allows us to calculate the total mass of the objects in the universe based on their collective gravitational effects.
It works like this:
1) The universe has a certain amount of objects, each of which have mass.
2) We know that any object that has mass will have a gravitational effect on all others (in the amount of the inverse of the square of the distance between them).
3) We can calculate with reasonable certainty (with infinite sequences - similar to the Fibonacci spiral, etc.) what the total effect of all the gravity would be in the universe based on any arbitrary amount of mass that exists in the universe.
4) We can tell how much of an effect the total gravitational force is by measuring the effects of gravity on galaxies, namely how fast the galaxies are moving, whether they are moving away from or towards one another (on a large scale), and whether the galaxies farther out are moving more slowly or faster than the ones close by.
5) We know what effect (through the math again) a certain amount of mass (x) would have on the universe as a whole. To be more specific, we know that if the equation with (x) works out to be greater than 1 (i.e., f(x)>1, which was sort of arbitrarily chosen, but bear with me here), the universe will eventually pull itself back together and gravity will cause it to end in a big crunch the opposite of the big bang. If (x) makes the equation *exactly* 1, (i.e., f(x)=1), the universe will reach a point of equilibrium and remain stable for eternity. If the value of (x) makes f(x)Interestingly enough, physicists cannot seem to figure out where more than 10% of the matter they think *should* exists is! Based on the empirical evidence, they know that the value should be something like f(x)=.99999999999999999 or something very close to, but ultimately smaller than, 1. In order to make this equation work, they know they need a certain value for (x). But they can't seem to figure out what more than 10% of (x) is - galaxies, stars, black holes, etc. can only account for a small amount of the overall mass needed to make the universe behave how it does (there is a technical reason for this conclusion, but I don't understand it well enough to explain it here).
The other 90% is something physicists call "dark matter", because they haven't been able to see it yet. They're not even sure it exists - the formula may need to be refined somewhat. Einstein discovered this anomaly when he first devised this theory and the math behind it. So he added a "fudge factor" to his equation which helped it all come out in the end. He gave it a spiffy name to make it sound legit - it's called the Cosmological Constant. Before he died, he called the creation of the CC his biggest mistake, but physicists have been absolutely unable to shake it yet, because they still don't know why there's such a big discrepancy between the matter they know about and the matter they need to make the equation perfect. It's one of the great mysteries of physics still.
As for your second question, "if that light has been traveling that whole time toward us, how did we get here first?", think about this: if you are travelling away from someone at the speed of light, and there is one light second between you when you emit a photon, it will take one second for that photon to reach the other perso