27th August 2007, 6:01 PM
I wonder where you might have read it. I hadn't heard anything like that myself. I have a hard time understanding where they would even get an idea of how much "unknown" there is in order to derive such a percentage. I mean some things you can actually get an idea, like ratios of things to other things. As it stands, since they seem to be seeing "back" far enough to get images of just as things are starting to form, it's likely we've seen the vast majority of it.
They did actually consider dark matter, but they ruled it out because dark matter, while it does not absorb, reflect, or radiate light (like everything else), can still alter it in one way, gravity. Gravitational distortion isn't present there, so they had to rule out a big clump of dark matter.
Hey, maybe that's what you read. It's true that by measuring gravitational distortion of light they've found massive amounts of dark matter floating all over the place in the universe, outnumbering so-called "normal" matter by a massive amount. Still, that still counts as "known universe" as scientists observed it, even if indirectly.
Suns don't do much bouncing... Unlike that model kit you have, stars aren't actually made of rubber :D. I kid, but really they measure the size of things with basically massive scale parallax (as in, measuring where things are relative to other things when on this side of earth's orbit and again a few seasons later on the other side). Also some other methods are out there. They can get a pretty good idea that way. In this case, they measured it by looking at "cold spots" in the cosmic background microwave radiation, and also noting that in the same spot in the sky where that radiation is colder, there also seems to be a total lack of infrared radiation. I'm not sure if they measured light in other wavelengths. I'd guess that's where confirmation with other observations come in.
They did actually consider dark matter, but they ruled it out because dark matter, while it does not absorb, reflect, or radiate light (like everything else), can still alter it in one way, gravity. Gravitational distortion isn't present there, so they had to rule out a big clump of dark matter.
Hey, maybe that's what you read. It's true that by measuring gravitational distortion of light they've found massive amounts of dark matter floating all over the place in the universe, outnumbering so-called "normal" matter by a massive amount. Still, that still counts as "known universe" as scientists observed it, even if indirectly.
Suns don't do much bouncing... Unlike that model kit you have, stars aren't actually made of rubber :D. I kid, but really they measure the size of things with basically massive scale parallax (as in, measuring where things are relative to other things when on this side of earth's orbit and again a few seasons later on the other side). Also some other methods are out there. They can get a pretty good idea that way. In this case, they measured it by looking at "cold spots" in the cosmic background microwave radiation, and also noting that in the same spot in the sky where that radiation is colder, there also seems to be a total lack of infrared radiation. I'm not sure if they measured light in other wavelengths. I'd guess that's where confirmation with other observations come in.
"On two occasions, I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able to rightly apprehend the kind of confusion of ideas that could provoke such a question." ~ Charles Babbage (1791-1871)