The weird and wonderful world of black holes

instellarI recently watched Interstellar for the second time – I don’t know if you’ve seen it, but in my opinion it is possibly the best sci-fi film ever (or at least number two after 2001 space odyssey). It follows the epic journey of a group of scientists and explorers who travel through a space anomaly in order to find a new planet for humankind. The earth is being ravaged by dust storms caused by climate change, everyone is dying, you get the gist. On their travels through space, the crew encounters a black hole, named ‘Gargantua’. One of the spectacular things about Interstellar, aside from the fantastic plot and terrific acting, is that all of the video footage of the black hole was created using scientifically accurate simulations, some of which took weeks to run. Granted, it was edited a bit to fit more with the image of the film, but what you see is our closest interpretation to what a black hole actually looks like. Inspired by the science behind the film, I thought I’d do a little digging into the nature of black holes, what is possibly going on inside them and look into some cool things that happen when you get up close and personal with the universe’s most unforgiving phenomena.

black-hole-1 black-hole-2

So you’re probably wondering: what exactly is a black hole? Well, a black hole is defined as a region of space which has an escape velocity greater than the speed of light. This is essentially how fast  you’d need to travel to escape an object’s gravitational pull. To put this into perspective, Earth’s escape speed is about eleven kilometres per second, whereas to get out of a black hole you’d need a speed greater than three hundred thousand kilometres per second, which is the speed light travels at. In this universe, nothing with mass travels faster than light, so if you fall inside the event horizon, or edge, of a black hole, you’re not coming out. An interesting thing to note is that around the event horizon, so called Hawking radiation is actually ejected back out into space. This is essentially just a shower of very energetic particles, and if you waited long enough, the black hole would eventually disappear because of this.

interstellar-movie-gargantua-black-hole-image

These beasts are so huge, with gravitational pulls so strong, that they can actually bend time and space. Back in 1916, Albert Einstein set out the rules of time and space in his paper on general relativity. The gist of general relativity is that time and space are connected, and they can be warped by gravity. Because of relativity, if you were near a black hole, or travelling very close to the speed of light, your clock would run differently to someone’s back on earth. In Interstellar, this meant that the crew didn’t age much but everyone else on Earth agedcurved-space faster.

Black holes weren’t always here though – although there is commonly a supermassive black hole at the centre of most galaxies, and a lot of smaller ones within. The smaller ones were born in the remnants of dying stars, specifically stars with a mass greater than about eight solar masses – that is, the mass of our own star. As for supermassive black holes, astrophysicists are still working on that one. They could have formed from giant stellar clouds spinning and then collapsing onto a point, or by another process entirely unheard of yet.

A strange quality of black holes is that they give rise to an unusual paradox, called the ‘black hole information loss paradox’. One of the fundamental laws of physics is that the information of a system is always conserved – yet when something is engulfed by a black hole, that information is destroyed. Fortunately, Stephen Hawking has already solved this one. Earlier this year he provided a solution which says that the information is preserved in a ‘2D holographic imprint’ above the event horizon of the black hole. So if we take a second to imagine this, if you saw your friend fall into a black hole, they might just appear to hover over the edge for all eternity, but in reality they would have already experienced a very unpleasant death (or been transported to an alternate reality). Because anything that falls in doesn’t come out (at least in the form it began as), we can never see inside a black hole, which is either cool or extremely annoying, depending on whether you’re a science fiction writer or an astrophysicist.

But what blackholewould actually happen if you happened to fall inside? Say for a second you decide to jump in, whilst your friend watches from your hypothetical spaceship. At first they would see you move further and further away, getting redder with time due to light being stretched out (this is redshift happening). At the edge your companion would see you hover over the edge, unmoving, and eventually burn up fire and brimstone. Whereas from your point of view, you would just continue to sail happily downwards towards oblivion. As you move deeper into the black hole, space and time get curved until you hit the centre, which is infinitely curved, and this is what is known as the singularity. Inside, time and space would actually swap, and time would be dragging you towards the centre, not space, and therefore you could never escape because you cannot go back in time. As for what happens at the centre, we can only speculate. In reality it’s unlikely that you’ll ever get near a black hole, so for now you can put aside your hopes of throwing your tutorial work over the event horizon, and perhaps just chuck it off the pier instead.

References

 

https://www.newscientist.com/round-up/instant-expert-general-relativity/

https://en.wikipedia.org/wiki/Escape_velocity

https://en.wikipedia.org/wiki/Stellar_black_hole

https://profmattstrassler.com/articles-and-posts/relativity-space-astronomy-and-cosmology/black-holes/black-hole-information-paradox-an-introduction/

http://astronomy.swin.edu.au/cosmos/S/Supermassive+Black+Hole

Image 1: IMDB (http://www.imdb.com/title/tt0816692/mediaviewer/rm1874904064)

Images 2 and 3: New Scientist (https://www.newscientist.com/article/dn26966-interstellars-true-black-hole-too-confusing/)

Image 4: http://www.space.com/32723-colliding-black-holes-sing-different-songs.html

Image 5: http://wapsec.com/wp-content/uploads/2014/02/now-with-spin.jpg

Image 6: https://en.wikipedia.org/wiki/File:BlackHole.jpg

 

 

 

 

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