Gravity and Dark Matter

Transcript

yep y so it I find it all the questions in physics seem in some way to go back to to gravity and it's funny how these uh particles um they adhere to gravity the force of gravity but not the other fundamental forces what makes gravity such an interesting and and difficult um aspect of of the physical universe so what's different about gravity is um what causes a Gra gravitational field is basically mass and energy and everything has mass and energy or certainly energy um including Dark Matter dark matter has mass and it has energy so it will create a a a gravitational field so the universality and also there's no anti-gravity so you can't screen gravity so you know the electromagnetic force is much much stronger than gravity um but there are positive charges and negative charges and uh when they get together they screen each other and you have a neut you know so there's no negative gravity there's no there's no anti-gravity so there's no there's no anti- particle to the Gravitron so to speak well uh not so much the graviton but but say say the proton say well say an electron and its anti particle the positron they both still have they both still a positive gravity exactly they both have a positive gravity so gravity is always attractive and uh and um you can't screen it and it's Universal it couples to all forms of energy uh that's why gravity um uh is important for large scale physics like cosmology because it can't be screened it's a very very weak Force it's the weakest of the four forces of nature that we've so far discovered many times weaker than than uh than the others and uh but it's it's very long ranged and and uh and it build builds up as you get more and more mass and energy the gravitational field keeps getting bigger and bigger and bigger and because it couples to everything you do have the potential through gravity to find other things like dark matter so the fact that it is linked to everything make makes it good for observation I suppose it does it it makes it good for um I guess discovering uh new types of particles at least if they're around in great numbers right if they're around in minute quantities then gravity is way too weak uh to to find them but this dark dark matter by the way there's five times as much of it in terms of mass per unit volume as there is ordinary matter am I right to say it it makes up approximately 27% of the entire universe that we know so yeah the the ratio of um ordinary matter to dark matter is about 1 to 5 mhm and then uh but then most of the uh energy density in the universe today is in this dark energy this this cosmological concept and and it's it's only I don't know 30% or of the universe that is in the form of matter and most of that is dark matter so you know ordinary atoms is is just like four or 5% of the it's so pretty much everything not not so long ago yeah so you know you know we can say that we really don't understand 95% of the energy that's in the universe which is which is you know you can say well that's bad but find that exciting it gives us something to do