Black holes


Sounds simple, a hole that is black. But what does that mean? It means a region of spacetime where gravity is so strong that nothing can escape from it. This meaning has come about from the theory of general relativity, predicting that a sufficiently compact mass can deform space time to form the black hole. There are so many things not to understand in these sentences, so where to actually start to describe black holes in normal people terms? NASA explains it as a ‘space where gravity pulls so much that even light cannot get out’. 

However, black holes aren’t even necessarily black. Quasars, which are the objects at the centre of distant galaxies, are likely to outshine the rest of their host galaxy combined - through radiation generated when the black hole is feasting on new material – meaning there is light in the black hole. The term feasting sounds quite active and scary. 

Although the description exists, implying that black holes exist, they cannot be seen by people – that leads to doubt of their existence. Very strong looking at space telescopes can apparently find them, but it seems that even then its potentially an illusion that they exist, with their presence being only in terms of effects on surrounding stars and gases – so what’s not there, rather than what is. They can vary in size from a single atom to supermassive, which have an equivalent mass of more than one million suns. Scientists think the smallest black holes formed when the universe began, and larger black holes formed at the same time their galaxy formed. So they’re pretty old if they exist. 

 Why do we need to know about black holes? What impact do they have on life on earth? Scientists seem to imply that they will not impact on Earth in the short term. The definition of short term here is at least four billion years from now – when Andromeda Galaxy is predicted to collide with Earth. Supermassive black holes don’t move and lie in the centre of galaxies, including Andromeda. Earth’s solar system is in stable orbit round a supermassive black hole which lies at the centre of the Milky Way, a mere 25000 light years away. Another thing that could happen is that a stellar black hole may collide with Earth – however, with radii of around 300 kilometres, the chances of a direct with Earth would be miniscule. 

 These are pretty low probability risks, although very high impact, and it’s great that scientists are able to predict what may happen in billions of years, and I’m sure that the robots that are alive then will appreciate the research that has been done now. 

So they’re out there, or maybe they’re not, they’re black or maybe they’re very light. They may destroy earth, or they may not, it depends. And if they do, then we wouldn’t know anyway as we’ll all be long dead.

Comments

  1. JeanieOctober 26, 2020 at 5:37 PM

    Thank you! Good to know we are safe for now..... Probably!

    ReplyDelete

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