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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
PS: I don't reply to ACs.
70 sextillion? Or did I miscount 000's?
Over a million (i.e., billion, trillion ... )
those number-words are ambiguous; British and I
think other Euro usage starts going up by multiples
of 10 ^ 6 instead of Americano 10 ^ 3. I say 7e22.
IANAPhysicist, but I'm pretty sure I can answer some of your questions. It has been theorized that the speed of light has changed in the past, and therefore can continue to change. However, if light used to be slower, then matter could still not travel faster than the slower speed, following all the current known laws. As far as I can tell, if the universe's expansion were to accelerate past the speed of light, then the force of gravity would be unable to slow it back down. Sadly, with regards to the initial question of how we can see light from the beginning of the universe, I unfortunately have no idea.
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
The universe expands by growing empty space everywhere, not just at its edges. This is why you measure the Hubble constant as speed per distance, (ie. kilometers per second per Megaparsec). If you want to compare c (speed of light) to H0 (Hubble constant) you'll have to agree on over which distance you're going to compare them. If you make the distance (the Megaparsecs) big enough; H0 will always win.
Better yet, lets get some "real" info about this:
Now you know.If the universe contains an Avogadro's number of stars then the universe has exactly 1 Ug (universe gram) of mass. Where the universe atomic mass unit is one star; 10^33 or 10^34 grams as we know them. :P
Remember, the visible universe is growing by a lightyear every year as light is just hitting us from very distant stars. :)
Not quite, remember the universe started from a central point with the big bang including those very distant stars. Also nothing can travel faster than the speed of light therefore we theoretically could see the entire universe given a strong enough telescope though much of what we see at the distant edge will be very young (it's still possible that there are stars currently outside the current radius of what we can see if they're expanding at almost the speed of light but we can watch them or their ancestors drift out there and they won't pop up).
Unless of course the big bang opened massive worm holes and sprouted up universes all over the place, then the light from them could be meeting us eventually and just pop out of nowhere...
I stole this Sig
That's Quintillion I say.
l lion
Million
Billion
Trillion
Quadrillion
Quniti
Septillion
Sextillion (boys and girls like this one)
Octillion
Nonillion
I'd go on a Vegan diet but the delivery time from Vega is too long. --brownkitty