Most of what we know about the universe comes from our analysis of electromagnetic radiation (i.e. light)
Light is like a wave
Electronic wave and magnetic wave oscillate together
Black hole in center of galaxy = 1 million times the mass of the sun
The Sun = a basic unit of measurement
ergs = g*cm^2 / second^2
Solar luminosity = 3.8 * 10^33 ergs/s
Mass: 2 * 10^30 kg
Age of universe: 13.7 billion years
Speed of light = 3 * 10^8 m/s
parsec = 3.26 light years
Special Relativity
2 main components:
* The laws of physics ar ehte same in any inertial frame
* The speed of light is the same for all observers in an inertial frame
Spacetime is 4-dimensional
A frame in which unaccelerated objects move in straight lines is an inertial frame
A globally inertial frame is a frame that covers all spacetime
Addition of speeds
Walking 5 mph, Bus 30mph, difference 25mph
Rocket 100,000km/s, Light 300,000km/s
Difference appears differently because the observers involved see spacetime differently
Time dilation: the time lapse between 2 events changes from one observer to another; it is dependent on the relative speed of the observers
Lorentz contraction - the dimensions of an object as measured by one observer may be smaller than that of another observer
This also has implications for how gravity works
Newtonian gravity: F = G (m1 m2)/r^2
General Relativity: mass-energy causes spacetime to curve
Objects, including light, follow the shortest path in curved spacetime
Gravity = curvature of spacetime
Clocks more slowly the closer they are to a gravitational mass
Sun's gravity would bend light coming from background stars
Time slows near any massive body. Slows down even near Earth. [albeit in very small amounts - 4 parts in 10 billion]
The angular momentum of a rotating body drags space into a tornado-like whirl around it. (small whirl
Will see object differently if a mass is on the way. This is called a "gravitational lens".
When the gravitational lens is perfectly aligned with the background object, the background object is modified into an Einstein Ring
Black holes - so much mass in such a small space that the spacetime warp is extreme
Nothing can escape, not even light
Detect black holes by their gravitational effect on nearby object
Stars, specially those near Galactic Center, are detected orbiting it
Supermassive black holes probably exist at the centers of most galaxies
Called galactic nuclei
Could have come about or become larger during galactic mergers
Collision of two black holes is the most violent event in the universe
* Produces wild vibrations of warped spacetime
Black holes related to their host galaxies: "chicken & egg" problem
* galaxy formation far enough back in time that we can't really tell
* Hypothesis: growing together
What happens in a black hole, stays on a black hole. This is how black holes build mass.
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