GR100

All over the world people are celebrating 100 years of General Relativity (yes! Einstein proposed the theory 100 years ago and we have been using its applications ever since!) and Imperial was one of them. This Monday Imperial College held a lecture to celebrate this huge milestone. PhD students of Professor Hawking were speakers at the event and Stephen Hawking himself was meant to be there but unfortunately fell ill and was unable to come. Nonetheless, the talk went on with Hawking there in spirit.

Following on from this Imperial College wanted to find out what we (the public) thought would happen if we were sucked into a black hole. A cute Einstein badge was up for grabs and I just had to submit my thoughts so I could get one!

Here is my answer to the question which was, of course, aided with the knowledge I have gained so far in my physics degree at Imperial. Enjoy!

Before we answer the question what would happen if you were sucked into a black hole, let’s begin with the question what is a black hole?

Einstein has taught us that gravity can be considered as warped space-time. The denser an object the more warped space time is around the object. A black hole is an extreme case of warped space time - so extreme, that at the most warped part it is a singularity! A black hole is produced by an extremely heavy star that has run out of fuel and collapsed in on itself. 

A good analogy of this is if you consider a bowling ball on your mattress - the mattress would sink inwards and near the bowling bowl you would see more sinking. Now, imagine that the bowling ball didn’t change in size but changed in density and became really, really, REALLY dense, then, you’d see a lot of sinking in! if you had a marble it would sink straight into the hole but physics inside a black hole or near it is a little strange…

At the outer boundary of a black hole is the EVENT HORIZON - if you pass this point there is NO RETURN. The event horizon is full of streams of hot particles that radiate back into the Universe due to quantum effects, this radiation bears the name of it’s discoverer: Hawking radiation. Additionally, at this point the gravitational force precisely counteracts the light’s effort to escape the black hole.

So, now go back to the question of what will happen if you were to get sucked by a black hole?

Let’s consider a friend watching you far from the black hole - she/he sees you get ‘spaghettified’. The gravitational field strength at your feet is stronger than that at your head so you get stretched! You also appear to move in slow motion the closer you get to the event horizon. At the event horizon, your friend sees you ‘frozen in time’ and you stay there motionless and stretched until you get reduced to ash because of the Hawking radiation.

But what about if we consider it from your point of view what would happen? Nothing.. just nothing. No spaghettification (except if the black hole were small). This is because you are in free fall and so feel no gravity. You cannot escape the black hole as this would involve travelling backwards in time but time only goes forwards. 

All in all, getting sucked in by black hole is more entertaining for your friend that it is for you.

Within minutes after posting it on Twitter I received a tweet from @imperialspark informing me of my winnings! I was so happy - cannot wait to receive my badge (selfies will be posted here in due course). 

Why not send your thoughts on Twitter (@ImperialCollege) or Facebook (Imperial College London) and win a badge too!