What is a black hole?
First, let's test your knowledge. Do you think a black hole is:
(a) One of these:     ?
(b) Something in space that you can travel through to distant universes?
(c) Something with massive gravity where even light can't escape?
(d) Something in your house that sucks your socks into an inescapable vortex never to be seen again?

Well, they're all 'sort of' correct. OK....(b) is highly dubious but we love Dr Who and need a bit of futuristic make-believe in our lives!

Basically, a black hole looks a bit like a hole. We know that they have so much gravity (a force which pulls surrounding matter into it) that even light can't escape it...hence, they look black (actually invisible) as they don't reflect or emit light.

How do they get all this gravity? Gotta love physics...here's the answer. A black hole forms from a star.  Gravity depends on two things:
(1) The mass of the object, and (2) How far away you are from the object

At this point, we'd better explain that mass isn't the same as size. Formula:  Mass = density x volume   
Volume is the 'space' an object takes-up. Density is how much matter or 'stuff' is in that space. Mass is similar to weight.
                                



                                 Both these objects probably have about the same mass. 
                           Gobstopper

MASSIVE sea sponge                                                       

Oops, back to black holes....here's a couple of diagrams that will help explain why black holes have such strong gravity.
   

 


__Distance to object____________
Remember, mass & distance decide gravity. 
Stars have to be around X 20 the size of our sun to become black holes.                  








_______________Distance to object______________________________

This is the black hole produced from the above star collapsing.  It's now tiny but has the same mass. An object can now get much closer to its centre. Therefore, gravitational force is greatly increased.                       

Now, to save us rambling on, here's a BRILLIANT site we've found which tells you loads about black holes AND has some cool experiments you can do online like 'what happens if I drop a clock in a black hole' etc. Click HERE and be taken to explore the Hubble site.

Black holes can't suck our planet into them as there isn't one close enough and our sun can never be a black hole as it's not big enough. A lot of people got scared on September 10, 2008 as that was the day they fired-up the Hadron Collider at CERN. People thought it would create a black hole which would suck our planet in. That's because people don't understand science enough and listened to some of the media scare stories. But did you know we are surrounded by black holes?

Some scientists now believe there may be tiny black holes whizzing through our planet on a daily basis, but so small that their gravity can't pull anything in, but rather they are useful to hold things in our orbit. It's thought this effect is similar to how electrons orbit a nucleus.   


This follows research from the Russian Academy of Sciences in Moscow which suggests that black holes could contain areas where time and space exist, hiding advance civilisations which exist without being seen from the outside. Maybe it's a dalek empire rebuilding it's forces before invading Earth...or not.

Either way, we reckon it provides a pretty solid explanation for where all our socks go!



 










Thanks to: badastronomer.com & Hubble for info on black holes