Bad science and Black holes

There is a trait that anyone who has studied a science based degree will pick up during their study, and it will always surface while watching tv programmes or in particular films. Some will be quite proud of this trait, whilst others may think of it as more of a curse.  I am of course talking about the ability to pick up on bad science, whether you want to or not!

There have been many times when I’ve been enjoying watching a film, when all of a sudden the main character will try and say something clever or suggest a clever idea to save the day etc, and I without hesitation my mind would go, ‘that’s wrong!’ Sometimes I’m quite proud that I know better, but other times I wish I didn’t as it just distracts me from enjoying the rest of the film.

As example, I will take the film ‘Signs’. If you haven’t seen it then be warned as there are spoilers ahead. The basic plot is that we follow Mel Gibson and his family through an alien invasion, which begins with crop circles, sightings on the tv and eventually finishes with a face to face finale when it is revealed that the big bad aliens weakness is……….  Water! That’s right, a substance that makes up 70% of the Earth’s surface seriously harms and eventually kills the invading aliens. Which begs the question, which of the aliens was stupid enough to suggest invading another planet without checking how much water was there first? And let’s not forget that it rains a lot on the Earth!

PoisonAlien <—-This alien’s not a keen swimmer

There are many more examples of bad science in tv and films, like the Dark Knight Rises (a  4 megaton bomb explodes not far outside the city and no one is incinerated or even harmed from the fallout….really?), but the reason I bring bad science up is actually because of the ’Go Compare’ advert.

go-compare-black-hole

We’ve all had the unfortunate experience of seeing them, and the many celebrities they take down with them, with the latest one starring Steven Hawking as he creates a black hole in the middle of the street that sucks in the opera singer, before disappearing once more. Now obviously creating a black hole outside your house is impossible, and that is not what I want to highlight, however the fact that the opera singer is physically sucked into the black hole is a common misunderstanding about black holes.

That fact is, you can technically orbit a black hole without falling into it. Every object has something called a Schwarzchild radius, which is the minimum radius an object, such as a star or planet, would have to be compressed into before it becomes a black hole. It is also the radius at which the escape velocity from the object is equal to the speed of light. Put simply, if you are inside this radius then you would have to travel at a speed greater than the speed of light to escape, and since that is impossible then not even light can escape, hence the name ‘Black Hole’.

So as long as you do not travel within this Schwarzchild radius, you can orbit a black hole, however you would still need to have a space craft capable of breaking the black holes gravity to move away again.

You may be wondering if the Earth could turn into a black hole, which it can, but only if it is compressed into the size of a grape. If that did happen then the Moon would continue to orbit around, though it would look as if it was orbiting nothing as the only thing that is left behind from  black hole is the objects gravitational field.

So next time you see the ’Go Compare’ advert I hope you think ‘That is not scientifically correct’. Of course, it’s not as if a black hole appearing in the middle off the street made you think that anyway!!!

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