Transcript of my chat with a student on DARK MATTER

Mani is online.

hi sir..gud aftrnun

hello

sir..hav u heard of dark matter?

ya

itz said dat its present evrywher in d universe...does it possess mass?

Not Everywhere, Darkmatter is matter which is not seen because they donot emit or reflect any detectable radiations or matter. Their presence is felt by gravity. Just like a blind find that things are there by feeling it. It possesses mass and that is how it is felt

bt its nt made of atoms..so hw can it b influencd by gravity??

Whatever be the elementary constituents, if there is matter there is gravity. Matter which cannot be detected, it may either be 100% absorbent or 100% transparent.

in either case, its presence is not "seen"

it constitutes about 90% of all substances in d universe..so it shud possibly b present everywer..even in our body..

If you find any discrepancy between your observed mass and felt mass (inertia) then there is a possibility

bt d felt mass cant b measured though..sir..so if dark matter is present..den the mass of every object is subjectd to vary..right?

darkmatter is not "seen" because of the absence of any radiation from it. It has gravity

 

yes..bt since it has mass..it wud add up to the mass of the matter in wich it is present..

By the way who said 90%? http://upload.wikimedia.org/wikipedia/commons/a/a5/080998_Universe_Content_240.jpg

It is not an easy task to explain everything via simple text chat. I recommend you go through the  following links to understand dark matter and dark energy better.

http://en.wikipedia.org/wiki/Dark_energy

http://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy/

http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/dark_energy.html

http://physicsworld.com/cws/article/print/19419

http://hubblesite.org/hubble_discoveries/dark_energy/