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bluecap
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Are there variations of dark matter concentration on Earth based on months or seasons of the year?
phinds said:Hard to say since no dark matter has ever been detected directly and the density in our solar system is very low even by the standards of dark matter. As I recall, the general estimate is that in the entire solar system there is enough dark matter to make up the mass equivalent of a modest sized asteroid.
No, it's spread out. Even if it fell into the sun, it would just pass through and go out the other sidebluecap said:The sun is the most massive object in the solar system and the most gravity.. does it mean all the dark matter has gravitated into the sun?
phinds said:No, it's spread out. Even if it fell into the sun, it would just pass through and go out the other side
bluecap said:You mean the sun gravity is not enough to attract any dark matter even those with stronger coupling to matter of our universe?
Drakkith said:No, he means that dark matter falls into the Sun and passes right through, emerging on the other side with the same speed that it started with. This is because the speed it gains falling into the Sun is then given back up as it moves further out of the Sun's gravity well. Imagine a pendulum. Lift it up and then drop it and the pendulum first accelerates downwards, gaining speed until it reaches the bottom before decelerating as it begins to swing upwards. If it weren't for friction and air resistance, the pendulum would oscillate forever, moving back and forth to the same height on each upswing. Dark matter would do the same thing except that it is already likely moving too fast to be captured into any sort of orbit or oscillatory motion by the Sun. It still accelerates while falling towards the Sun and decelerates while moving away, but this results in zero net change in speed.
Sun doesn't move through dark matter. Dark matter moves through sun. No tail.snorkack said:Does Sun leave a tail moving through dark matter?
snorkack said:Does Sun leave a tail moving through dark matter?
phinds said:Sun doesn't move through dark matter. Dark matter moves through sun. No tail.
Does not follow.mfb said:Dark matter didn't form a rotating disk like the regular matter. It is more like a big cloud of gas with dark matter particles moving around randomly. The Sun moves through this cloud, but as the particle motion is random and nearly uniform before, it is random and nearly uniform afterwards as well.
Everything that has a mass interacts with gravity.bluecap said:do all kinds of dark matter interact with gravity? Is there no dark matter that doesn't interact with gravity?
Stavros Kiri said:Everything that has a mass interacts with gravity.
All dark matter particles are massive, as far as I know (WIMPs). And gravity and weak interaction are the only interactions via which dark matter interacts.bluecap said:is there no dark matter that has no mass that doesn't interact with gravity? yet say it only interacts with matter...
or are there no dark matter that interacts with matter yet doesn't have any mass nor gravity?
Yesbluecap said:do all kinds of dark matter interact with gravity?
Nobluecap said:Is there no dark matter that doesn't interact with gravity?
Nobluecap said:is there no dark matter that has no mass that doesn't interact with gravity? yet say it only interacts with matter...
Nobluecap said:or are there no dark matter that interacts with matter yet doesn't have any mass nor gravity?
Stavros Kiri said:All dark matter particles are massive, as far as I know (WIMPs). And gravity and weak interaction are the only interactions via which dark matter interacts.
So now let's take again your questions, one by one:
(Answers: as far as I know, and based on what I stated in these two posts of mine)
1.
Yes
2.
No
(but your question is not syntactically correct [it has two negations])
3.
No
(again, the first part of the question is not syntactically correct)
4.
No
(but again no need of the first "no" in your question)
Not the definition. Dark matter gets its name from the fact that it is not seen (thus doesn't interact electromagnetically), but still has a mass to interact gravitationally. You can kind of call that as the definition. (For more see e.g. https://en.m.wikipedia.org/wiki/Dark_matter)bluecap said:So the definition of dark matter is it has mass and interacts with gravity...
If as "no mass" you mean zero mass all the time ... , then no there is no such a thing.bluecap said:If there is a substance that interacts with matter but has no mass and doesn't interact with gravity.. then what is this substance called? And what laws of physics makes it not possible to exist?
Stavros Kiri said:All dark matter particles are massive, as far as I know (WIMPs). And gravity and weak interaction are the only interactions via which dark matter interacts.
So now let's take again your questions, one by one:
(Answers: as far as I know, and based on what I stated in these two posts of mine)
1.
Yes
2.
No
(but your question is not syntactically correct [it has two negations])
3.
No
(again, the first part of the question is not syntactically correct)
4.
No
(but again no need of the first "no" in your question)
bluecap said:Are there certain species of dark matter where it has no mass at rest and only has relativistic mass if it is accelerated to near speed.
bluecap said:Or based on your last message where only gauge bosons have no mass... Are there gauge bosons which have no mass and can stay at rest and only have mass if it is accelerated to near light speed?
I don't think so. All WIMPs are supposed to be massive particles, and 'massive' means they have a non-zero rest mass. But (theoretically) what you're asking could be at least a legitimate question, but not within the standard model type of DM theory (e.g. WIMPs).bluecap said:Are there certain species of dark matter where it has no mass at rest and only has relativistic mass if it is accelerated to near speed.
No!bluecap said:Or based on your last message where only gauge bosons have no mass... Are there gauge bosons which have no mass and can stay at rest and only have mass if it is accelerated to near light speed?
Having a massless particle that can stay at rest is no particle at all [IMO]. (what kind of part of matter would that be?)bluecap said:If not possible. What symmetry or laws of physics disallow such particle or gauge bosons or whatever?
For the same reason light can't (answered above).bluecap said:And btw. why can't gauge bosons stay at rest?
None! I think it's not a matter of gauge symmetry but rather relevance to a fundamental principle and law of physics. For one thing, if what you say happened, Lorentz Invariance and Special Relativity would be violated! ...bluecap said:What gauge symmetry group can make gauge bosons stay at rest?
bluecap said:what do you make of this (can you find any flaw?):
This would violate special relativity, unless "near speed" means the speed of light. But massless particles would not clump together like dark matter does.bluecap said:Are there certain species of dark matter where it has no mass at rest and only has relativistic mass if it is accelerated to near speed.
I'm not a dark matter expert, but as far as I can see, all the phase space for their assumed WIMP mass and cross section has been ruled out by orders of magnitude since that publication was published, mainly by PICO-60, PandaX-II and CDMS-lite. Here is a recent study.bluecap said:Going back to the question whether the sun can capture dark matter.. two astrophysicists have been studying this.. who else? what do you make of this (can you find any flaw?):
Does "dark energy" behave like massless particles would (like photons or gravitons, but not interacting with matter) or in yet another manner?mfb said:This would violate special relativity, unless "near speed" means the speed of light. But massless particles would not clump together like dark matter does.
What does that mean?snorkack said:If universe were charged
Like masses attract. Like charges repel. What are expected consequences if universe had unbalanced electric charge, either positive or negative?mfb said:What does that mean?
All known matter and fields slow down the acceleration.
bluecap said:is there no dark matter that has no mass that doesn't interact with gravity? yet say it only interacts with matter...
or are there no dark matter that interacts with matter yet doesn't have any mass nor gravity?
bluecap said:So the definition of dark matter is it has mass and interacts with gravity...
If there is a substance that interacts with matter but has no mass and doesn't interact with gravity.. then what is this substance called? And what laws of physics makes it not possible to exist?