Dark matter

-


In the energy of the universe, dark matter makes up about 25%, a quarter of the universe.

Antimatter doesn't seem to exist in the current universe.


If we look at the solar system, all the planets revolve around the sun. But it's velocity is fixed by the distance from the sun. It goes down, like one over square root of the distance. Each planet is moving at a pretty high speed around the sun. As we go farther and father away from the source of gravity. Because the gravity gets weaker by inverse square root, its reverse revolution velocity should become slower. So that's what we see in this situation. In the solar system.


But if we look at the scale of the galaxy, and this is our own galaxy. Our solar system is away from the center by 28,000 light years away. It doesn't seem to be the case. Our solar system is moving actually very fast, much faster than the entire source of gravity coming from the stars combined would support us. So something else beyond the stars exists in our own galaxy. That is pulling us inside the Milky Way Galaxy. So if we actually tried to measure this as a function of distance from the center of the galaxy, this is our solar system.We're moving at a speed of about 220 kilometers per second. But if even if you go to farther and farther away outskirts of our Milky Way Galaxy, the rotation speed doesn't seem to go down at all. And that's strange, right?


From Newton is that if the, the center of the gravity and the source of the gravity is centralized in some way. Then as you go farther and farther away from the source of gravity, we should be slowing down. But clearly things are not slowing down towards the outskirts of the galaxy, so there must be a lot more mass. That would actually keep coming in as you go farther and farther out and that's what we call the dark matter of intergalactic halo.


So even when we go to the places of the galaxy where we don't see any star at all. Then rotation speed doesn't seem to go down, so that's where we have good evidence on the existence of dark matter.

Comments

Post a Comment

Popular posts from this blog

The Friedmann equation.

-
This is the basic equation of cosmology, and its solution tells how universe will evolve on large scales. We can derive it using Newtonian approximation, if we accept two results from General Relativity: First, there is, so called, Birkhoff's ,theorem, which says that, for a spherically symmetric system, the force due to gravity at some radius is determined only   by the mass interior to this radius. And also, the energy contributes to gravitational mass density. So we need to add them up together. Imagine a sphere with a mean density of row, radius of R, acceleration to a particle in surface, which is the second derivative of the radius, is given by formula.                 Ȑ = - 4 л G ϱ R                          3 Now, if the density changes, it c...
Read more

Higgs Boson and its importance

-
Image
The Higgs boson particle can be argued as one of the most phenomenal discoveries in this 21st century. A particle which was previously theorized to exist, Mr. Peter Higgs proposed this idea that universe has Higgs Boson stuck everywhere that was already like 50 years ago but scientifically discovered in March 14 2013. The search for this particle was inspired by some fundamental questions in particle physics; such as why certain particles have mass when the symmetries controlling their interactions should be massless.  For more than 40years, scientists have searched and experimented to uncover this elusive phenomenon and the particle which may have induced mass in these molecules. This prolonged and frustrating search would lend the name 'Goddamn particle' to the Higgs Boson particle which is now shortened and called the 'God particle' after its discovery. The Higgs Boson particle is named after Peter Higgs, one of the 6 scientists who hypothesized the exi...
Read more

Creating Domain Network

-
Steps to create Domain Controller:( server) 1. Install server Operating system   2.Set IP address for domain controller. Give same IP address in preferred DNS server. 3.Install DNS (Domain Name System)    Go to Control Panel / Add or Remove Programs / Add or Remove windows components / Open networking services and select DNS / Click on OK / Next  (CD is needed for the purpose of installation ) 4. Install Active Directory  Go to run. Type domain controller promotion   In welcome screen click Next  Click on domain controller for a new domain  Click on domain in a new forest  Give the new domain name  Give the net bios domain name  Click on Next  Shared system volume:Next  Select on the Install and configure the DNS server on this computer / Next  Choose option permission compatible only with windows 2000 Click on Next  Finish the Restart   
Read more