RSS iconTwitter iconFacebook icon

The Trek BBS title image

The Trek BBS statistics

Threads: 141,556
Posts: 5,513,858
Members: 25,146
Currently online: 589
Newest member: TM2-Megatron

TrekToday headlines

Two New Starships Collection Ships
By: T'Bonz on Dec 26

Captain Kirk’s Boldest Missions
By: T'Bonz on Dec 25

Trek Paper Clips
By: T'Bonz on Dec 24

Sargent Passes
By: T'Bonz on Dec 23

QMx Trek Insignia Badges
By: T'Bonz on Dec 23

And The New Director Of Star Trek 3 Is…
By: T'Bonz on Dec 23

TV Alert: Pine On Tonight Show
By: T'Bonz on Dec 22

Retro Review: The Emperor’s New Cloak
By: Michelle on Dec 20

Star Trek Opera
By: T'Bonz on Dec 19

New Abrams Project
By: T'Bonz on Dec 18


Welcome! The Trek BBS is the number one place to chat about Star Trek with like-minded fans. Please login to see our full range of forums as well as the ability to send and receive private messages, track your favourite topics and of course join in the discussions.

If you are a new visitor, join us for free. If you are an existing member please login below. Note: for members who joined under our old messageboard system, please login with your display name not your login name.


Go Back   The Trek BBS > Entertainment & Interests > Science and Technology

Science and Technology "Somewhere, something incredible is waiting to be known." - Carl Sagan.

Reply
 
Thread Tools
Old April 2 2010, 11:28 AM   #1
SamuraiBlue
Lieutenant Commander
 
Location: Land of the rising sun
Concerning Dark matter

I was going through an article concerning dark matter consisting approx.30% of total mass within our space. I also read that candidates for dark matters are sub-atomic particles that do not interact with other matter so we are not able to study this particle except for it's gravitational effect due to it's mass.
One of the reason why dark matter has postulated in the first place was the to explain orbital velocities of galaxies in clusters.

My question is, IF dark matter is a sub-atomic particle then it should not be localized within space due to entropy, then should it not show gravitational effect to our own solar system?
SamuraiBlue is offline   Reply With Quote
Old April 2 2010, 01:15 PM   #2
Shaw
Commodore
 
Shaw's Avatar
 
Location: Twin Cities
Re: Concerning Dark matter

I guess the answer is that it does.

One of the early measurements that brought about the concept of dark matter was that stars within the galactic disk of galaxies were not moving at the speeds one would have expected if the stars were just orbiting the galactic center. The gravitational effect of some dark matter seemed the most likely solution.

Beyond that, what effect were you thinking there should be? And are you saying that particles with mass wouldn't be effected by gravity?

I mean think about it... a subatomic particle that doesn't interact with any other particles could pass through the earth as if it wasn't even there (considering that most of what we consider solid matter is actually empty space).

If we could magically hold one of these particles at a couple meters above the ground and then let it go, it would fall through the earth and eventually pop up on the other side and then fall back again... and could do that for years without hitting anything. By not having any other interactions short of a direct hit on another subatomic particle, most solid matter becomes empty space. And other than it's gravitational effect, the earth would seem like it wasn't even there to one of these particles.



Note: I'm not saying that I subscribe to the current theories of Dark Matter, but if it is cause by such a particle, this is why it would be hard to find.
Shaw is offline   Reply With Quote
Old April 2 2010, 01:35 PM   #3
SamuraiBlue
Lieutenant Commander
 
Location: Land of the rising sun
Re: Concerning Dark matter

Shaw wrote: View Post
I guess the answer is that it does.

One of the early measurements that brought about the concept of dark matter was that stars within the galactic disk of galaxies were not moving at the speeds one would have expected if the stars were just orbiting the galactic center. The gravitational effect of some dark matter seemed the most likely solution.

Beyond that, what effect were you thinking there should be? And are you saying that particles with mass wouldn't be effected by gravity?

I mean think about it... a subatomic particle that doesn't interact with any other particles could pass through the earth as if it wasn't even there (considering that most of what we consider solid matter is actually empty space).

If we could magically hold one of these particles at a couple meters above the ground and then let it go, it would fall through the earth and eventually pop up on the other side and then fall back again... and could do that for years without hitting anything. By not having any other interactions short of a direct hit on another subatomic particle, most solid matter becomes empty space. And other than it's gravitational effect, the earth would seem like it wasn't even there to one of these particles.
I don't think so since according to Newton's law of universal gravitation, planets will pull the particles towards the center, larger the mass more particle it would capture within it's gravitational well resulting to change of mass through passage of time which should result to change of orbit which we have not observed.
SamuraiBlue is offline   Reply With Quote
Old April 2 2010, 02:38 PM   #4
Shaw
Commodore
 
Shaw's Avatar
 
Location: Twin Cities
Re: Concerning Dark matter

How would a planet, star or other large body capture one of these particles? If they don't hit anything, then the best you can hope for is a change in their direction. The hypothetical I gave required the particles to start with zero initial momentum relative to the earth... but without that, the best you could hope for is that they might alter their path a little. It would require something very massive (neutron star scale) to capture one of these particles.

And when we are talking about such small effects with no other forces beyond gravity, initial momentum and the exceptionally rare collision, it would take very large gravitational systems (like galaxies and galactic clusters) to capture these in any measurable amount where their combined gravitational effects would come into play.

But in the end this isn't an argument... you asked, I told, you are free to disregard. The physics is pretty straight forward, so even though I don't subscribe to the theory of these particles, there is nothing wrong with the mechanics (even using Newton's laws) of the theory.
Shaw is offline   Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 01:25 AM.

Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
FireFox 2+ or Internet Explorer 7+ highly recommended.