Sophie, Chicago asked:
Is it possible to make a phone call from a black hole?
We put this question to Andrew Pontzen, research fellow at the Kavli Institute for Cosmology:
Andrew - The short answer is no, but maybe you could receive a text message. So let me take a step back and try to explain. Basically, when you make a mobile phone call the device that youíre holding in your hand is using radio waves to send your voice to the person at the other end of the call. Radio waves are just a certain form of light - we canít see it directly but we receive it using antennae in our mobile phones and other devices. Because itís a form of light, just like any other light, it canít get out of a black hole. So you cannot send your voice out of the black hole, thereís no way for you to have a conversation. On the other hand, light can certainly get into a black hole and in the same way radio waves can get into a black hole. So if you were to adapt your mobile phone so it could just receive text messages without having to communicate to the network, then you could actually receive a text message from your mum just before you died at the centre of the black hole.
Diana - Lovely! so no-one can hear you scream from a black hole but you could pick up a text telling you to pick some potatoes the next time you go shopping. That answer was given by Andrew Pontzen and you can hear more from him answering your science questions and keeping us up to date with space site news on our Naked Astronomy podcast available from thenakedscientists.com/astronomy.
Your mobile phone won't work because the radio frequency signal will never escape from the black hole.
If anyone needs a black hole to test this theory you are welcome to come round my house; this is the worst phone black hole I've ever experienced. If I flatten my face against my dining room window I can just about get my mobile to sustain a conversation; other than that it's a non-starter...! chris, Thu, 11th Feb 2010
We have a similar problem. Our mobiles don't work at all in our house. I think it's great, because we don't waste any minutes!
Of course it is they are calling in and out of Hatti Doubting Thomas, Mon, 15th Feb 2010
I don't understand this comment, could you clarify for me please? BRValsler, Mon, 15th Feb 2010
that was iether a very bad joke or a stupid industrialists, paranoia on getting the upper hand. are you saying that, there is a company who divert calles through hatti have there company "there" just so you can make cheep calls, i can see how the ploy would work but not the morals geo driver, Tue, 16th Feb 2010
What's Hatti? Is this it http://en.wikipedia.org/wiki/Hattie_Jacques Geezer, Tue, 16th Feb 2010
I think that the answer to the original question is yes, provided that your home is in the same black hole that you are. Bored chemist, Tue, 16th Feb 2010
Hey folks... new member.
Added to that, given how dense matter will be in a Black Hole, how fast would sound / vibrations travel? Similarly, how rapidly would sound be conducted through a neutron star?
Hi, I thought I could expand on my original answer given some of the further questions asked here.