Black
Holes FAQ
Answers Page
1.
What is a black hole?
A black hole is a region of space whose gravity
is so strong that it acts like a giant vacuum cleaner in space. Anything that
gets too close gets sucked in. When it hits the center, the singularity, it disappears
forever. The gravity in black holes is SO strong that it tugs at space and
time, slowing down time and stretching out space. Not even light, the fastest
thing in the universe, can escape from a black hole.
Click
here to go to the section entitled "What is a Black Hole?"
2.
Wouldn't a black hole up everything in the universe?
No. The boundary
of a black hole is called the "event horizon," and it has a limited
extent. The gravity of a black hole is the same as a normal object, except that
it's usually a lot because most black holes are very dense. As long as you're
outside the event horizon, you can avoid getting sucked in. If you're inside the
event horizon, however, you're doomed.
3.
How are black holes created?
For most of their lives, stars remain the
same size because they have a balance of forces: heat made by burning fuel pushes
the star out, and the effect of gravity pulls it in. After billions of years,
when the star has used up all of its fuel, it collapses under its own weight.
Two scientists, Oppenheimer and Snyder, proved that if the start has more than
3.2 times the mass of the Sun (known as 3.2 solar masses), there is nothing to
stop it from collapsing into a black hole.
Click here
to go to the section entitled "The History of Black Holes"
4.
Can only stars become black holes, or could planets and other things become black
holes? If not, why is this?
Technically, anything can form a black hole,
whether it be a star, a planet, or a human being! In order for something to become
a black hole, it has to be compressed so that it's smaller than its Schwarzschild
radius. The Schwarzschild radius is a distance from the center of a star or another
object where math goes crazy (once an object become a black hole, the Schwarzschild
radius can be called its "event horizon." At this distance, space
becomes infinite, and time disappears. Mathematicians call this "singular"
(this is where the word "singularity" came from). Most of the time,
this Schwarzschild radius is much smaller than the object. The Schwarzschild radius
of the Sun is three kilometers. The formula for finding something's Schwarzschild
radius is as follows:
R* = 1.48×10-27
M
where R* is the Schwarzschild
radius in meters and M is the mass of the object in kilograms.
(NOTE: 1.48×10-27
is using scientific notation, and really means 0.00000000000000000000000000148.
What I did is this: to turn 1.48×10-27
into a normal number, I moved the decimal point in 1.48
27 places to the left, because the exponent, or power of ten (-27)
is a negative number. If it were a positive number (like 27), then
you would move the decimal point in 1.48 27
places to the right. Scientific notation is a lot shorter way to express it!)
Realistically, however, only stars naturally form black holes, and only stars that have more than 3.2 times the mass of our Sun. Only through some strange supernatural or alien force could you or me become a black hole, because we just don't have enough mass.
5.
How do we know that black holes exist?
Until recently, black holes were
just theories and speculations. However, on February 27, 1994, the Hubble Space
Telescope discovered what seemingly had to be a black hole. There wasn't
any other explanation for it. Other black hole candidates had been found before,
but none that couldn't be explained otherwise, as was the case with this 3-billion-solar-mass
black hole at the center of M87.
Click here to go to
the section entitled "Black Holes Proven by Hubble Telescope"
6.
Are we in any danger of falling into a black hole?
No. Although it is
believed there is a supermassive black hole at the center of our galaxy, we are
on the outside of our galaxy, on one of the spiral arms, quite far from the massive
monster.
7.
Could the Sun become a black hole?
No, the Sun could not become
a black hole naturally (by the forces of gravity at the end of its life).
8. I've heard
rumors that there is a black hole near Pluto. Is this true?
No. Scientist
have not detected any black hole in the vicinity of Pluto. These are just
rumors. (Personally, I haven't heard them, but Steven has.)
9.
Who made up the term "black hole"? When?
The American scientist
John Archibald Wheeler was the one who coined the term, in 1979. Before that they
were sometimes called "frozen stars."
10.
Is a black hole really "black"?
Not according to the British
scientist Professor Stephen Hawking. He believes this radiation can come from
"virtual particles," particles that are created out of nothing, thereby
defying the laws of physics. As pairs, they can then collide with one another
and be destroyed back into empty space. Normally, we would therefore never even
see these particles before they disappear. If a pair of these particles popped
up at the edge of a black hole, one could be sucked in while the other escaped
as a newly created particle coming from the black hole. This is known as "Hawking
radiation."
Click here to go to the section entitled
"Black Holes Ain't So Black!"
11. Is a black
hole a bottomless pit (or "hole") in space?
No. The term "black
hole" is really a misnomer because a black hole is actually a 3-dimensional
object. A black hole is really a black sphere. And no, it is not bottomless. There
are limits to how far the edge of a black hole stretches.
12.
What happens if I jump into a black hole?
If an astronaut were going
in a black hole, it would be a one-way trip. Long before the astronaut event arrived
at the edge of the black hole, the difference between the forces acting on his
head and the forces acting on his feet would stretch him like toffy. Finally,
the astronaut would meet his death when he hit the singularity at the center of
the black hole, as his atoms compress to infinite density and zero volume, becoming
part of the singularity.
Click here to go to the section
entitled "Exploring a Black Hole"
13.
Does a black hole ever fill up?
A black hole never literally fills up.
However, a black hole's life ends eventually as a result of matter pouring in.
As a result of losing energy and mass through Hawking radiation, Professor Hawking
suggests that there would come a point when the black hole no longer has enough
mass to completely curve the space around it, therefore ceasing to be a black
hole. Hawking predicts that the black hole might then explode with a force of
millions of hydrogen bombs!
Click here to go to the
section entitled "Black Holes Ain't So Black!"
14.
How big are black holes?
This depends on how large or small the object
was that the black hole formed from.
15.
Do black holes live forever?
According to Professor Hawking, no. He says
that as a result of losing energy and mass through Hawking radiation, there would
come a point when the black hole no longer has enough mass to completely curve
the space around it, therefore ceasing to be a black hole. Hawking predicts that
the black hole might then explode with a force of millions of hydrogen bombs!
16.
Can we make a black hole in a laboratory?
Not yet, although you can read
about this in the magnificently written novel Earth
by David Brin.
We encourage you to send in questions to add to this section.
We'll do our best to answer them. Just send an e-mail to blackholes@ben.freehosting.net.
