Dark Matter — "Alternative Gravity" Team Responds

An anonymous reader writes, "Following previous results, an international team of astronomers answers, defending the case for a modification of the theory of gravity. This article presents an alternative to dark matter and states constraints on the neutrino mass. In short, dark matter is still not a necessity, provided that neutrinos weigh 2eV. This is allowed by what we currently know and should be tested in the KATRIN experiment in 2009."

Comments

So We Must Wait.

[Mikkeles]

Basically, then, until the mass of the neutrino has been tested, dark matter or alternate gravity are just speculations with the arguments being:

is too!
is not!
is too!

...

It's the Ether

[Fysiks Wurks]

Dark Matter is the 21st century's ether.

Re:It's the Ether

[dmatos]

To the scientific understanding at the time, there was evidence of the aether. It had been observed that light exhibited wave-like characteristics, and could, in fact, be understood as a wave. At that time, all waves were known to travel through a medium. There were no waves that could travel without one. There was no other medium in the vacuum of space, so it was decided that there must be an aether.

A perfectly valid scientific theory, as it was also falsifiable - as demonstrated by Michelson and Morley. When it was falsified, it required a major change in how the scientific communtiy thought about light. It is entirely possible that we'll see something similar with dark matter. Sure, an unobserved WIMP could explain things like the rotation of galaxies at their current rates. But, what happens when we get out there and don't find any? What then? Well, maybe it will require a major change in how we think about gravity. Maybe there's an entirely new force out there, that's weak enough that we can't see it on terrestrial or even solar scales. Who knows?

Re:Anti-dark-matter scientists are like ID scienti

[FhnuZoag]

Enh.

Neutrinos *do* have mass, and this fact is accepted by pretty much all physicists. The argument for this comes from discovery that they change states over the course of their lives, which means that they experience time, which means that they cannot travel at the speed of light, which means they must have a small mass. (This explains the apparently deficiency of solar neutrinos which was a problem in the 70s) Pinning down the exact value of this mass is more troublesome, though - for now, we know only that it's small, but positive.

What more puzzles me about this statement is that neutrinos have generally been counted as *part* of dark matter - in particular, they are proposed to constitute some of those so-called Weakly Interacting Massive Particles (WIMPs) which is one of two possible models for dark matter. I don't see how changing the details of these particles would change how neccessary they are, unless these guys are trying a bait and switch by redefining dark matter to be unneccessary. (Which would be a very dirty trick.)

Re:Anti-dark-matter scientists are like ID scienti

[vondo]

I think I'd regret responding to the complete misunderstanding of forces and neutrinos in the body of your post. That would take pages.

Let me just respond to your title. That is completely wrong as well. Now, I think the alternative gravity guys are probably wrong and at this point I think they are stretching their theories to their limits. Dark matter is the "easiest" explanation. But, what they are doing is science. They are coming up with an alternate theory that makes predictions and testing them. The are countering circumstantial evidence for DM with another theory. They are not picking just one small thing, saying "Well that can't be true because of [insert some non-science babble like you just posted] so clearly God created everything." in contradiction to vast bodies of scientific evidence. And the alternative gravity people are publishing in peer-reviewed journals.

ID can't say any of those things. While the motivations may be similar (not wanting to give up on old ways of thinking about things) the methodology is completely different.

Re:Useful research

[Daniel Dvorkin]

Attention, parent poster and everyone who agrees with him: please immediately cease enjoying benefits of government-funded science. That means logging off /., getting rid of your computer -- in fact, not owning any personal electrical devices whatsoever -- refusing any medical diagnostic procedure developed after the invention of X-rays, and generally living life ca. 1900.

For those who say, "that's technology, not science!" I will note that the examples I gave were based largely on previously abstract, largely government-funded scientific research whose applications were not immediately obvious, but which have since transformed the way we live. If you don't understand the research, that's fine; you don't have to in order to take advantage of it. But just because you don't give a shit about the way things work doesn't mean that you get to stand in the way of people who do, and whose work will benefit you and your children's lives, no matter how little you deserve it.

Re:why would matter be dark

[RsG]

Quoth wikipedia right back at you:
http://en.wikipedia.org/wiki/Light_sail

The spacecraft deploys a large membrane mirror which reflects light from the Sun or some other source. The radiation pressure on the mirror provides a minuscule amount of thrust by reflecting photons.

There, see? He was right about solar sails.

You were thinking of a magnetic sail:
http://en.wikipedia.org/wiki/Magnetic_sail

Which is something completely different. Magnetic sails do use solar wind; solar sails use sunlight. Big big difference between the two.

Re:why would matter be dark

[Jhan]

Photons lack mass but (since they move at 1,0 c) they do have momentum. This is wat makes solar sails work.

Nope. Quoth wikipedia: A solar wind is a...

Except that solar sails do not depend on "solar wind", ie. particles. The main thrust (when above a certain distance form the sun at least) is delivered by massless photons, ie. light. Hence the more correct term "light sail".