Unit 6 Cosmology

What is the Big Bang

Big Bang happened everywhere with near instantaneous results of
gravity, electromagnetic, weak nuclear, and strong nuclear forces

What are Black Holes?

• A black hole is a region in space where the pulling force of gravity is so strong that light is not able to escape

• The strong gravity occurs because matter has been pressed into a tiny space

• This compression can take place at the end of a star's life. Black holes are a result of dying stars that were born larger than 30 times the size of the Sun

• The term "black hole" was coined in 1967 by American astronomer John Wheeler, and the first one was discovered in 1971

What are Black Holes? continued

• Stellar black holes form when the center of a very massive star collapses in upon itself

• Result is a lot of matter in a small space

• There is not enough energy to act against gravity to stop it collapsing

• How it works: the more massive a star/object in space is, the more space-time bends

• The Schwarzschild radius is the size that a given object, with a given mass, should have in order for it to be a black hole. For instance, if we managed to concentrate
  all the mass of the Earth into a sphere of a radius of a few centimeters, then that object would be a black hole

• The larger the original mass, the larger the radius of the event horizon

Laws of Physics at work

• Laws of Physics as we know them break down greater than the speed of light. Not even light can escape a Black Hole

What would happen if you went down a Black Hole?

• The Milky Way has a Black Hole equivalent to 4 million solar masses.

• If you were to take a step into a black hole, your body would most closely resemble "toothpaste being extruded out of the tube. “

• You would age slower

  
  

How can we see a Black Hole if light cannot escape?

• The existence of black hole binary partners for ordinary stars can be inferred by the effect the holes have on the star’s orbit, or by radiation from in falling matter giving off X-rays

• Gravitational Lensing – as an object goes past a Black Hole the light from the object shows bending of the object’s motion as curved near due to the gravity field

What is Dark Energy?

• Dark energy can escape a black hole, no matter what size the black hole is and no matter how close the dark energy is to the center of the black hole

• This is because dark energy is not affected by gravity at all. Dark energy is what causes the universe to expand faster

• There is about 73% Dark Energy and 23% Dark Matter
  

Will Dark Energy cause the Universe to expand forever?

• Will Dark Energy cause the Universe to expand to the point of absolute zero Kelvin, thus nothing would cease to exist? Expansion means cooling and the Universe is only at 3 Kelvin now.

Will Dark Matter cause a Big Bang again?

No, dark matter will not cause another Big Bang, because dark matter is a passive, invisible substance that pulls things together with gravity