In space, no one can hear you scream.. right?

On 29th June, The Naked Scientists and engineers at Brunel University, London, launched a balloon into space. They say that in space, no-one can hear you scream, but we wanted to test that for ourselves. So, after months of testing, we attached a loudspeaker and a microphone to a helium balloon and sent it up to one hundred and twenty thousand feet. Chris Smith explained the story...

Chris - Well the idea of this is to send a balloon to the edge of space, and the reason for doing that is that we want to test the theory that in space no one can hear you scream. The rig has been built by Dave Ansell...

Dave - So there's a square based pyramid made out of dowling, held together with cable ties. From this is suspended on springs a loudspeaker at the square end, and a little bit further down, a little tiny microphone in a lump of brass to try and give it a bit more mass.

Chris - So they are hanging in space but supported by the springs and the elastic. They’re not connected to each other, they can see each other, but there's no way for the vibrations to travel out of one and into the other. The rig’s been built by Dave Ansell and the software has been written by Omar Gad...

Omar - The biggest challenge for me was getting the device small enough and getting a power source that can power all of this.

克里斯-这个东西有一百twenty thousand feet - it would easily go over the top of Mount Everest - so we need to make sure that whatever we do, we can cope with low pressure and low temperature. We bought a cheap speaker off the internet, and then we went bought a microphone that cost about £8. And pretty quickly realised that an £8 microphone was not going to cut it because it was rubbish, so we went bought an £80 microphone and that was much better.

Omar - And so I recorded myself screaming. That was recorded with the mic, and now we're going to play what the mic recorded.

Chris - So it's playing the audio of the screams and it's also recording the audio and we're also recording other things like temperature, pressure. There is also a satellite transponder on it, because we need to track this thing and we need to know where it's going because we’ve got to go and retrieve it, and we have no way of controlling where it comes down apart from watching the weather and following it.

Omar - That noise is coming from the receiver, and the receiver is receiving data from the transmitter. So that noise is actually ones and zeros being sent across the air. And then on here you actually start to see here look, it says temperature and it will then give you the temperature, altitude, latitude and longitude.

Chris - The weather for this is critical. When something is going on a four hour flight, all the time its up in the air it subject to wind, but it's pretty windy up there regardless. So it's definitely going to travel across the country. So we may have to do a bit of driving to catch up with this thing. If the wind suddenly changes direction and turns west then the whole lot’s going to go in the ocean and we’re going to lose everything. I'm dead excited about this. I don't think anyone’s done it quite the way we are trying to do this before so this is quite cool. It's a first. Do you know, it's been really good fun.

Chris - Right, well it's Saturday, 29 June. We've just got in the car and we have to go to the West Country to launch the balloon because the prevailing wind direction is towards the east, so this balloon should go down somewhere over Birmingham-ish. I'm optimistic. Buoyant.

Chris - Yes, so now we’ve finally arrived. We’re here in this field.

Omar - It is my birthday, yes. I am launching a balloon into space on my birthday.

Chris - We've got a very large cylinder of helium which is what we're going to put into the balloon...

Three, two, one, go...

Konstantinos - I'm Dr Konstantinos Banitsas from Brunel University. This is a project that has a thousand things that can go wrong and only in one scenario you can actually retrieve it. Everything has to work right.

Chris - We've got the device we've built which is in a big polystyrene box which the balloon is going to carry up to a hundred and twenty thousand feet.

Omar - We're going to have two mobile phones in there and a Gopro to actually take videos. So we’re going to put those in last. We have to be absolutely sure that everything is secure because we can't tell how crazy the weather might get up there.

Konstantinos - Stop, stop, stop, stop, stop!

Omar - Yeah, we’re ready. We’re ready to launch now..

Crowd - Ten, nine, eight, seven, six, five, four, three, two, one, lift off.

Konstantinos - Yes, yes! That's perfect.

Omar - 1047 metres, after probably about five minutes? I’m now going to run the prediction now that we’ve launched it to see exactly where it’s going to end up. Okay. It's going to land in a place called New Cross near Wolverhampton. One team should now get going and we will probably clear up and chase after it.

Tim - Well I’m Tim Pilgrim at Brunel University, and I’m the press officer that originally helped Omar get in contact with Chris to set up this whole thing. So we've now reached the outskirts of Birmingham and we’ve just received some exciting news that the balloon has started to come back down again, so we've obviously reached peak. Fingers crossed, we should be at the landing site before the balloon gets there…

Tim - Oh, it’s already landed?

Omar - It’s in a field right next to a river.

Tim - Oh, fantastic.

Omar - You guys are probably going to be the first ones there.

Tim - Cheers!

Omar - Bye.

Tim - Oh, that’s exciting.

Omar - Yes! We got it!

Tim - Where is it?

Konstantinos - We found it! Exactly where we were supposed to find it. This is the best case scenario: it just lands in a field somewhere. No danger at all. And it's here!

Omar - Here it is, the payload. In the middle of a field. We actually lost telemetry. Had it not been for the Find My Phone app, this is actually how we found the device.

Chris - Well, we did it. We have succeeded. We actually got our device up to the edge of space and we got it back again, and we’ve got all the data. What did we find? Well, if we look at two screams, here’s the first one: this one was recorded at the ground…

Children! Come and clean your room!

克里斯-…and you compare that with this, which was recorded at 33km up just before the balloon popped where the pressure is 10 millibar, so only about one one-hundredth of the pressure at the Earth’s surface…

Children! Come and clean your room!

克里斯-…你能听到这两个dramatically different, the second - where the air is very thin - is really quiet. So the logical conclusion is, were we to have carried on going up even further, the air would have continued to get even thinner; we would eventually have reached a point where there would be so few air molecules bashing into the microphone, it would barely move and you wouldn’t be able to hear it. Case closed. But we have made a special page on our website with all of the raw data and the recordings, as well as other measurements we made, and you can go and take a look at that. Interestingly we’ve got the profile of the carbon dioxide levels as we go up, and we think on our graph you can see the effects of the M4 motorway and the city of Bristol just upwind of where we were taking off. If you want to go and have a look at it, it’s nakedscientists.com/balloon.