Slashdot Mirror
90% of the Universe Found Hiding In Plain View
The Bad Astronomer writes "As much as 90% of previously hidden galaxies in the distant Universe have been found by astronomers using the Very Large Telescope in Chile. Previous surveys had looked for distant (10 billion light years away) galaxies by searching in a wavelength of ultraviolet light emitted by hydrogen atoms — distant young galaxies should be blasting out this light, but very few were detected. The problem is that the ultraviolet light never gets out of the galaxies, so we never see them. In this new study, astronomers searched a different wavelength emitted by hydrogen, and voila, ten times as many galaxies could be seen, meaning 90% of them had been missed before."
...and this isn't the conclusion that I immediately jumped to - the discovery of dark matter. It's merely the discovery of the visible matter that they though should always be there.
Does this account for any missing mass and/or dark matter?
FTFA: "...this has nothing to do with dark matter."
From TFA:
"I'll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists ... locally, in nearby galaxies and clusters of galaxies, too. This new result doesn't affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can't possibly affect nearby galaxies, so they don't account for dark matter."
Absolutely wrong. TFA even states this means nothing for dark matter, we knew that these galaxies were out there, we just hadn't spotted them yet. Besides, we've seen dark matter much closer to home. When galaxies collide, the gas pressure stops the regular matter, while the dark matter keeps moving along at the same speed. The dark matter has mass, so it creates a gravatic lens. We have seen these lenses, with no visible matter to create them, when galaxies collide.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
Make sure everyone's vote counts: Verified Voting
Dark matter isn't just matter that isn't lit up (that was one of the original theories, but has since fallen to the wayside), it is matter that is fundamentally different and doesn't appear to interact with regular matter at all, except gravitationally.
it is matter that is fundamentally different and doesn't appear to interact with regular matter at all, except gravitationally.
More specifically, it doesn't appear to interact electromagnetically. Which just happens to exclude all of our direct detection methods (i.e. telescopes).
One candidate for dark matter is the neutralino, which is predicted by Supersymetric Theory and is basically a neutrino but heavier, and like a neutrino interacts through the Weak Interaction which allowed us to find neutrinos, and maybe even actual dark matter.
The enemies of Democracy are
The next record-breaking one they're building is the Extremely Large Telescope. Seriously.
I knew about the fudge factor we needed to get the equations to work - I didn't know we have actually seen something like that.
It was never a "fudge factor" to make the equation of gravity "work". It was a prediction of the already extremely well-working equation. Not "Oh noes gravity is broken, we need 'dark matter' to fix it." Rather "Huh, gravity implies there is a mass here that we can't see with our electromagnetic detection devices".
Think of it this way. You're walking around a room blindfolded with a cane that has a pressure sensor on the end that uses a voice synthesizer to tell you the readings. You notice that all along a large flat plane the pressure sensor detects pressure equal to that with which you push. Newton's 3rd Law tells you that for this to happen, something must be pushing back with equal force. Something like a wall.
Now, do you say that the wall is a fudge to make Newton's 3rd Law work?
Or do you say that Newton's 3rd Law implies that there is a wall there?
I mean you might as well say that the existence of the Sun is a fudge to make electromagnetic and gravitational equations work.
I'm not trying to rag on you or anything (I mean you said 'thank you' for evidence after all), just trying to clear up a misconception that I think has lead to a lot of unnecessary skepticism of dark matter.
The enemies of Democracy are
Actually it's the Overwhelmingly Large Telescope.
The Tao of math: The numbers you can count are not the real numbers.
There's a big fat gap between what the calculations say the rate of galaxy formation should be, and what it is actually observed to be. This new observation accounts for 90% of that rate.
Slashdot: news for Apple. Stuff that Apple.
No, I meant quantum leap as in literally a quantum leap.
An electron dropping from orbital L3 to L2 instead of L2 to L1 is exactly what sends out photons of a more detectable temperature.
I’ll note: this has nothing to do with dark matter. As it happens, 90% of the matter in the Universe is in a form that emits no light, but affects other matter through gravity. We know it exists, and you can find out why here. We know it exists locally, in nearby galaxies and clusters of galaxies, too. This new result doesn’t affect that, since the now un-hidden galaxies are very far away, like many billions of light years away. They can’t possibly affect nearby galaxies, so they don’t account for dark matter.
This will change the ratio of luminous matter:dark matter but not eliminate dark matter entirely.
Not that you said that it would necessarily get rid of dark matter, but it was a conclusion that suggested itself from the summary's wording.
It is imprecise to say physicists indicate there should be much more mass in the universe. What they say is that there is mass missing in every galaxy which implies it is missing from the universe but only on a galaxy by galaxy basis. Dark matter is necessary to explain why galaxies form. In other words the "missing" matter is in each and every galaxy. Discovering more galaxies doesn't affect that issue.
When I was a physics major in the dark ages they were just beginning to notice that computer simulations based on observed stellar quantities and masses had the annoying property of never resulting in galaxies. In subsequent years it was computed that the needed mass for galaxy formation wasn't off by a little but actually by a huge factor.
Eventually some observations of gravitational lensing have provided more evidence that there was huge amounts of mass measured in this indirect fashion that was simply not seen by exhaustive charting of the observed stars.