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We here at SciShow like to start things off with a "Boom" for yet another season! Hank talks about the mystery behind the "Space Roar" and why it is we can't really hear it.

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Sources:
http://www.howstuffworks.com/humans-hear-in-space.htm
http://io9.com/5986849/what-is-space-roar
http://physicsdatabase.com/2013/03/16/the-great-unsolved-problems-in-physics-the-space-roar/
http://www.space.com/6293-mystery-roar-faraway-space-detected.html
http://prezi.com/78dbpnjnazkn/space-roar/ - clips of space sounds
http://www.spacetoday.org/Questions/StarlightAge.html
http://www.nasa.gov/centers/goddard/news/topstory/2009/arcade_balloon.html
http://www.howitworksdaily.com/science/why-do-radio-waves-travel-at-the-speed-of-light-and-not-sound/
http://www.nature.com/news/kepler-s-surprise-the-sounds-of-the-stars-1.9724
http://www.popularmechanics.com/how-to/blog/what-created-these-mystery-radio-waves-from-another-galaxy-15657576
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
This is the third year of SciShow! We're still bringing you all the exciting content that we can find but with this new look - and an accurate lunar lander in our opening. Thanks for helping us with that, and thanks for watching SciShow.

(SciShow opening plays.)

In 2006, NASA tethered its latest fancy, teched-out toy to a giant balloon and sent it nearly 37 kilometers up into the tippy-top of the atmosphere. The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission - jauntily nicknamed ARCADE - was launched to listen for faint radio signals and heat traces issued from distant, early 13 billion-year-old stars and galaxies far far away and free from earth's own atmosphere and interference. And it found something totally bizarre and unexpected - a super strong, blaring radio signal described by researchers as a "boom."

It was six times stronger than anyone predicted, more intense than all of the other sources of radio in the whole universe. It's like they expected to hear Hank Green talking in normal Hank Green-discusses-science tone of voice BUT INSTEAD THEY GOT THIISSS!

After examining the noise some more, researchers determined that the radio emissions were not from the far away internal vibrations of early stars or the turbulent interference of our own galaxy's space dust and gas. In fact not even a chorus of all the stars in the all the galaxies put together could equal the intensity of this mysterious roar blaring in the background of space. It came to be known as the "space roar." And while we know what it isn't - we still don't know what is is.

So far ARCADE has only looked at about 7% of the sky. But even within this fraction of space the roar is widespread. We know it's out there, but we don't know where it's coming from.

Now you may be wondering what I mean by noise here, because obviously I don't mean it literally. If space were roaring at us probably astronauts would have noticed by now.

Sound as we know it moves in mechanical waves which are basically disturbances that pass through a physical medium like air or water or your upstairs neighbor's wooden floor which happens to be your ceiling.

You may have heard that in space, no one can hear you scream.
That's because space is mostly a vacuum so there is no physical medium for sound to move through, at least not very efficiently. But radio waves don't have that restrictions. They are electromagnetic waves caused by radiation they are not mechanical.

Light and heat are other types of electromagnetic radiation that can move through space. You might be familiar with the work of that menacing day-star that beams its radiation down upon you for an average of 12 hours each day - as an example.

So those radio waves are not actual sounds. We just receive their signals and then our equipment translated the vibrations that we can hear.

Radio waves are electromagnetic waves just like light and thus they travel at the speed of light. But we can hear radio waves from farther away than we can see light. In this way a distant twinkling star emitting radio waves through its internal vibrations is pretty similar to our own sun emitting visible light. But if you were to hop on the Enterprise and travel far far away from Earth you might only be able to register our sun as radio waves rather than light.

Lots of objects in space emit detectable radio waves. Search Google for sounds of planets and stars and galaxies and quasars and you'll find that they can sound really creepy actually, like a hiss or a wailing, the perfect soundtrack to a terrifying alien movie.

So while radio signals from other galaxies have been detected before, they were nothing like this space roar, which is so loud that it's seriously limiting our ability to detect signals from the earliest stars which, of course, was ARCADE's original mission.

As NASA guru, Alan Kogut said "There is something new and interesting going on in the universe."

Not knowing is exciting! But it is also annoying! I hate not knowing! I also love it.

Thank you for watching this episode of SciShow. And an extra special thanks to our Subbable subscribers. What's this? In my pocket? Oh, well it's a SciShow pocket protector! Which you can get at subbable.com. If you have any questions or comments or ideas for us we're on Facebook and Twitter and down in the comments below and if you want to keep getting smarter with us here at SciShow you can got to youtube.com/scishow and subscribe.

(SciShow end screen plays.)