Comments on: Darker Matter

By: Brian Koberlein

Brian Koberlein — Sat, 08 Dec 2018 16:12:10 +0000

The effects of gas, dust and plasma on light are measurably different than the effects of gravity, and they don’t create this kind of lensing effect.

By: Chiara

Chiara — Sat, 08 Dec 2018 13:43:39 +0000

Brian, the photos are wonderful. Given that dark matter is observed with gravitational lensing, how does one know that the lensing is not due to a thin gas or dust cloud between the galaxy and us? It seems that everybody is sure that the dark matter is near the galaxy. How does one know that so precisely, when looking at the lensing effect?

By: Brian Koberlein

Brian Koberlein — Thu, 01 Jun 2017 21:16:38 +0000

No, he doesn’t. Basically you’re arguing that the application of a certain phenomenon toward human technology is the only true knowledge, which isn’t so. For example, we’ve been baking bread and brewing beer for millennia, simply as a matter of following a set of instructions without any real understanding of the underlying mechanism. True, that is some level of understanding, but not a deep one. With the development of germ theory and a modern understanding of yeast we do know the underlying mechanism. Our understanding is now much deeper. On the other hand, we know how the Earth orbits the Sun, and we know in principle how its orbit could be changed, but we don’t have the power to change Earth’s orbit. You can have power without understanding, and understanding without power. Dark matter is in the latter category. We understand it. We can confirm its effect on light and other matter, but we cannot control it. That’s not a cop out, that’s science.

By: George Butiri

George Butiri — Thu, 01 Jun 2017 17:20:57 +0000

Well, ovidius has a point though. Is dark matter not like plato’s shadows? All we see is shadows, but somehow we can’t replicate those shadows. With radio waves, we’ve been able to control that energy to create radios, tvs, walkie talkies, baby monitors, cell phones, CB radios… the list is very long. Infra-red, ultra-violet, x-rays, gamma rays, and even electrons… we’ve been able to empirically predict and use to our benefit, able to mold the universe to our will… What have we been able to do with Dark Matter? How is it tangible in our every day lives? All of the other things that have been discovered are much, much more tangible, and therefore, more real. Dark Matter seems to be like the sun setting. We only see that it sets, but haven’t figured out yet that our planet is round and it actually spins on its axis, giving the illusion of a sun rise and a sun set. Gravity is the same way. We’ve been using it since the day we rolled a rock down a hill, built aqueducts, etc. But, we’re still not able to explain the energy that displays it. But, we’ve been using it. I remember reading once about how Dark Matter was simply used to explain things that we couldn’t otherwise. Doesn’t sound like sound theory to me. Sounds like a cop-out. As ovidius has said, we can roll a ball down a ramp and see gravity, warm up water in a microwave… but somehow, with dark matter, there’s no evident data.

By: Brian Koberlein

Brian Koberlein — Thu, 19 Nov 2015 22:45:56 +0000

I did a series of posts a while back on the evidence for dark matter. To answer your question "can we actually record" dark matter, the answer is yes. We do it much the same way we create radio images. Radio antennas just detect radio waves from a particular direction. By gathering a whole bunch of measurements of an object we can map the object to produce an image. We can do the same for dark matter. Look at the gravitational lensing over a region of sky and we can map dark matter. You might argue that it's still "based on theory", but that's true of everything, including what we see with our own eyes. What our eyes detect is used to create a model of what we see. Dark matter is indeed very real.

By: ovidius naso

ovidius naso — Thu, 19 Nov 2015 20:11:46 +0000

I am a layman, not a scientist, and I am not critical of Dark Matter as a theory, but I do find myself a little perplexed by the “it is as real as infrared radiation” claim in this article. I would love to understand the data for Dark Matter more.

This article says that I “can’t see infrared” and that’s similar to how I can’t see dark matter. But that’s not really true at all. Forgetting the fact that I can feel infrared (because the same is not true of ultraviolet) I can actually see infrared – just not with my eyeball. As the writer pointed out, we can all see infrared with the right equipment. A solider can see infrared and shoot someone. It is not visible to the human eye, but it is otherwise “directly visible”.

Dark matter, as far as I understand it, is only visible by the effects the occur in it’s (theorized?) presence. Am I wrong about this? Is there a device or experiment that can actually record/see dark matter like a camera can see infrared, or ultraviolet, or radio waves for that matter?

By: Jean Tate

Jean Tate — Thu, 24 Sep 2015 13:07:17 +0000

“20+ parameters”? Would you mind saying where you got that from?

“the only theory that predicts dark matter”? I didn’t know that! I thought DM is just a parameter in standard cosmological models. Again, may I ask you for a source?

“new science …”? Really? What new science is that, may I ask?

By: T

Thu, 24 Sep 2015 05:22:50 +0000

Care to explain the 20+ parameters (and counting) that have needed to be added onto the big bang theory, the only theory that predicts dark matter? New science is slowly showing it’s more likely that there is no singularity. Keep up with the times.

By: Brian Koberlein

Brian Koberlein — Sat, 04 Jul 2015 13:53:14 +0000

Orbits in 1/r gravity aren’t stable, so that can’t be the solution.

By: Iori Fujita

Iori Fujita — Sat, 04 Jul 2015 12:28:04 +0000

I think the gravity works two (+ time) dimensionally in the galaxy scale. Then the gravitational force depends not on (1/r^2) but (1/r), so the galaxy rotation curve becomes naturally flat.

By: JimV

JimV — Tue, 31 Mar 2015 13:31:08 +0000

I think the standard answer (I am not an expert) is that charge is what causes normal matter to stick together and dark matter particles have neutral charge, like neutrons (but of course free neutrons have a very short half-life so DM is not neutrons).

By: Amir

Amir — Mon, 30 Mar 2015 13:07:45 +0000

I’m not sure I understand this post.

Why do the stars in two galaxies clump in the middle after the galaxies collide?
If the clumping is caused (almost) only by gravitational interaction, the dark matter halos should clump approximately the same way.
So is the the leading theory that the clumping is caused largely by friction and star formation, with the slowed-down parts pulling the the faster stars?

If so, then this estimate of self-interaction among the dark matter only applies to the part of it that is gaseous.
What if a large part of dark matter in rock-like form, made from non-baryonic molecules held together by an unknown dark-matter-only attractive force? Wouldn’t this give the same final dark mass distribution as the model of gas with low cross-ratio?

Thanks,
Amir