- sujung09 sujung09 Feb 25, 2009


Contents
Black Holes
Albert Einstein
A. What is in Einstein's head?
B. Ether, Luminiferous Aether
C. Special Relativity
D. General Relativity
E. Black Hole
Q&As

What's the name of this mighty hole in our universe?
What's the name of this song(supermassive ooooo oooo) sung by Muse?

It's a Black Hole.

Q. What is a Black Hole?
A. It is the thing exists somewhere in the universe that sucks all the things around it.

Q. Who found it?
A. ..Who knows?

Well, that is the answer for non-physics taking people.
In physics, we want a little more clearly stated answer.
So here we go...


Black Hole


BH2.jpg
©ESA/NASA

Its existence was predicted by Einstein and Schwarzschild's theories, orginally called by the name 'Frozen Stars,' in the 1930s.
Then John Wheeler started calling it 'Black Hole' from 1967.

What is a Black Hole?

According to the 50 Physics Ideas You Really Need to Know by Joanne Baker,
it is a pit that is so deep and steep that anything that comes close enough to it falls straight in and cannot return.

'A-ha! ...I do not understand it.'

If you can understand the statement, you do not have to read any further. Yay!
If you cannot understand the statement, spend little time with Mr. Einstein.

Why? Because the Black hole models and explanations we have now is based on Einstein's relativity theories developed by Karl Schwarzchild.
It is rather necessary to know Einstein to understand what the Black Hole is.

A. What is in Einstein's head?

Albert_Einstein.jpg
Arthur Sasse, © Bettmann/CORBIS

The famous childhood story of A. Einstein is his answer for the 'what's 1+1?'
What is it? 2!!!
Einstein did not answer 2. He said one. Why? We know the answer.
One water drop plus another water drop is still one. That was his reasoning.

...who would think of water when you look at the numbers?

I mean when you see math problems, you do not bother to think of numbers as 30 trees, x lands, total of 150 trees, how many lands we have?

However, Einstein did.


Why am I talking about this?
A little warning that Einstein will mess up your brain a bit,
because his brain works in an extraordinary way. Let's get into his brain to understand his theories.

We are living in the 3-D world, 3 dimensional world (line, shape, and volume - space)

But, are we?

What about time? Aren't we living with 'time' ?
Do you ever not cared about 'time' during your life?
It's time go to school, time to eat, time to sleep, so on and on.

We are not living in the 3-D world, we are living in 4-D world.
4-D world where space and time exists.
This world of four dimensions is where Einstein lived, and where we are living now.

From now on, you will think in his way - counting not only space but also time.
Ready?

B. Ether, Luminiferous Aether

It is well-known that outer Earth atmosphere has no atoms at all.
However, the light travels through the space and reaches the Earth.
How? There is no atom at all.

So people in the early age thought that there is a special particle, named 'Ether', that enables lights to travel through.
Yet, it would be in fixed position in the space.
aether.png

The experiment by Albert Michelson and Edward Morley, resulting unchanged speed of light no matter what, proved the ether did not exist in 1887.

C. Special Relativity
In 1905, the fixed speed of light puzzled Einstein and lead him to devise the Theory of Spcial Relativity.

His theory assumed that the speed of light is a constant value, appears same for any observer no matter how fast they are moving.
Therefore if the speed of light does not change, something else must be changed - distance or time or both.
b/c

eq.jpg
Orting Physics 2009


Einstein expected 'time' to slow down.
Also, he assumed everything is relative to each other - no stationary frames but inertial frames;
and the laws of physics are same in each inertial frame.

D. General Relativity

After developing the Special Relativity, Einstein developed another theory, General Relativity.

This is where you need to think like Einstein, think of a four dimensional world (space-time), or metric world.

The best way to understand General Relativity is to imagine the universe as a rubber sheet.

ah.jpg
Orting Physics 2009
Then weighted masses like cue balls, which represent each planet, placed upon the the rubber sheet.
What would it do to the sheet? The ball will stretch the rubber sheet downward, depressing the space-time around it

What would happen if smaller ball comes around the depressed area?
It will roll down toward the bigger ball.

If the smaller ball's speed matches with the bigger ball's dip, the small ball will keep circling around the bigger ball.
Just like moon circles around the Earth!

The depressed area around the ball represents the effected area of gravity of a planet.
The edge of the area is called "Event Horizon".

The gravity of a planet does not only effect the mass attained objects around, it also affects the light goes around to it.
It would deflect if it passes around the heavy mass like Sun.
This proved to be right in 1919 by astronomers, and named as a 'gravitational lensing' because it mimics the lens shape.

E. Black holes

The Black holes are extremely heavy-massed things in the space-time sheet that stretches the sheet super deep.
Like this:

A.jpg

It's so deep that even light, time, or space cannot resist against its gravity.


Q&As: black_hole.gif

"If everything around the Black Hole gets pulled into it, how do we know the light has been pulled into?
we wouldn't have an evidence."

In the book, Joanner Baker gives two answers for the question.
One, The way of Black hole pulling other objects toward it.
Two, the big glow gas gives off as it falls into the Black Hole.


"What if there is something faster the speed of light?"

This is where the equstion [ E = mc² ] can be used.
The mass of an object infinitely increases as the speed of the object becomes closer to the speed of light.
This mass would disable the object to reach the exact speed of light, therefore nothing can exceed
the speed of the light.
(the mass of the light is exception because light is made out of photons which are mass-less)