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PetTastic
2015-Oct-13, 09:59 PM
How fast are we thought to be travelling relative to local dark matter?
Is the speed thought to be constant throughout the year?

Is the local DM orbiting the sun with the Earth?
Is DM thought to be orbiting the galaxy with the sun?

I was just reading some old articles that suggest that even if detectors could not find any direct hits from DM particles, billions of glancing blows should be detectable from energy an momentum imparted.

John Mendenhall
2015-Oct-14, 12:05 AM
Why would dark matter, which is defined as not interacting with ordinary matter, conveniently interact with ordinary matter for glancing blows?

malaidas
2015-Oct-14, 12:14 AM
I thought it was only em it didn't interact with.

Noclevername
2015-Oct-14, 12:40 AM
DM interacts with baryonic matter very weakly via gravity. It's not easy to detect, however, otherwise we'd have identified its particles by now.

antoniseb
2015-Oct-14, 01:32 AM
How fast are we thought to be travelling relative to local dark matter?
Is the speed thought to be constant throughout the year?

Is the local DM orbiting the sun with the Earth?
Is DM thought to be orbiting the galaxy with the sun?

I was just reading some old articles that suggest that even if detectors could not find any direct hits from DM particles, billions of glancing blows should be detectable from energy an momentum imparted.

The Dark Matter they are trying to detect is probably moving about 100 to 500 km/sec relative to us. Each particle is orbiting the center of the galaxy, probably in highly elliptical orbits and not toed to the plane of the galaxy. Also not necessarily in the same direction as our orbit, so we could in some cases be going face on into them, and in some case orbiting with them, but not getting any one particular velocity.

borman
2015-Oct-14, 02:08 AM
A couple experimenters have found the lower bound on DM waves to be around 65c while the upper bound may be a Carrollian deformation. Usually brane tension sets wave speed.

John Mendenhall
2015-Oct-14, 03:34 AM
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The Dark Matter they are trying to detect is probably moving about 100 to 500 km/sec relative to us. Each particle is orbiting the center of the galaxy, probably in highly elliptical orbits and not toed to the plane of the galaxy. Also not necessarily in the same direction as our orbit, so we could in some cases be going face on into them, and in some case orbiting with them, but not getting any one particular velocity.

Hmm. Hmm. Does ordinary matter in a big elliptical galaxy follow the same pattern?

Jens
2015-Oct-14, 04:21 AM
I thought it was only em it didn't interact with.

It wouldn't interact through the strong force either. I think whether it interacts through the weak force or not is a question.

PetTastic
2015-Oct-14, 08:42 AM
The Dark Matter they are trying to detect is probably moving about 100 to 500 km/sec relative to us. Each particle is orbiting the center of the galaxy, probably in highly elliptical orbits and not toed to the plane of the galaxy. Also not necessarily in the same direction as our orbit, so we could in some cases be going face on into them, and in some case orbiting with them, but not getting any one particular velocity.

Ok, thanks

Modelling it that way gives quite a wide range of velocities.
DM orbiting the galaxy in a high orbit the wrong way, hitting us at its closest approach to the centre of the galaxy could be going 1300 km/s+.
High speed intergalactic DM?
Min velocity for DM orbiting galaxy with sun 42 km/s. (hitting us from any direction as it loops around the sun)
Would DM orbiting the sun have to be orbiting the same way as Jupiter/planets because of gravitational interaction?

antoniseb
2015-Oct-14, 11:31 AM
... High speed intergalactic DM?
Min velocity for DM orbiting galaxy with sun 42 km/s. (hitting us from any direction as it loops around the sun)
Would DM orbiting the sun have to be orbiting the same way as Jupiter/planets because of gravitational interaction?
High speed intergalactic dark matter is possible, but that would be hot dark matter, and not explain rotation speeds or cluster lensing, so it is not the majority of dark matter.
Dark matter orbiting the Sun can't really be a high volume thing since planetary orbits and space probes have placed some very low upper limits on how much of that there can be, but there is no reason it should have settled into the plane of the ecliptic.