Silent as the night: Why radio astronomy doesn’t listen to the sky

Within the 1997 film “Contact,” Ellie Arroway is a younger radio astronomer performed by Jodie Foster. Ellie’s on a mission to find alien life, and in a single well-known scene filmed on the Very Giant Array, she sits on the fringe of the observatory, listening to the radio sounds of the sky with antenna dishes within the background.

It is a great cinematic second highlighting Ellie’s lonely seek for fact and has turn out to be so iconic that many guests to the VLA take “that shot” of themselves sporting headphones in entrance of a radio dish. However as superbly poetic because the scene is, it’s Hollywood magic, not exhausting science. The radio signals from Ellie’s headphones and laptop would intervene with the observatory’s delicate tools and radio astronomers do not hearken to the sky.

The concept radio astronomers hearken to celestial objects is probably the most important false impression in radio astronomy. And to a point it is comprehensible. Folks hearken to the radio on a regular basis, so absolutely radio astronomers should do the identical. However the sounds we hear on the radio aren’t the sounds of radio itself. They’re transformed from electrical alerts. Sound waves require a medium resembling air to journey via, and since space is basically a vacuum, sounds cannot journey via space. If astronomers did hearken to the sky, all they might hear is silence.

Radio is a type of mild. It is identical to seen mild, however with a for much longer wavelength. Whereas seen mild has a wavelength on the dimensions of atoms, radio mild has wavelengths starting from in regards to the thickness of a pencil result in greater than the size of a bus.

As a result of radio wavelengths are on the human scale, the expertise of radio astronomy is commonly very totally different from that of optical astronomy. There are broad similarities. Each optical and radio astronomy use reflective surfaces to focus mild onto a detector or receiver, which then converts the sunshine right into a digital sign. Astronomers can then use this digital sign to create astronomical photos. However as a result of radio wavelengths are a lot longer than visible wavelengths, we now have to attain this feat in numerous methods.

One key issue is the scale of the reflector. Typically, the bigger your reflector or mirror, the extra mild you may focus and the sharper and brighter your picture. Because of this the most effective optical telescopes have mirrors a number of meters in diameter. However the dimension of your reflector should scale to that of your wavelength. Since radio waves are hundreds of instances longer than seen waves, a radio telescope mirror would have to be bigger than Manhattan. That is not one thing we are able to construct, so as an alternative, we create arrays of smaller dishes. Every antenna dish acts like a chunk of a bigger mirror. Astronomers can then simulate a city-wide dish by combining knowledge from the array of smaller dishes.

One other issue is that radio mild is commonly a lot fainter than visible light, and there are lots of issues that create radio mild. Which means that radio telescopes have to be shielded from on a regular basis objects resembling cell telephones and laptop tools that emit radio mild. The antenna receivers should even be extraordinarily chilly. Objects at room temperature emit numerous faint radio mild which may have an effect on the accuracy of observational knowledge, so the receivers and different electronics of a radio telescope should be supercooled to transform radio mild right into a digital sign.

After all, as soon as astronomers have their knowledge, they will at all times convert that knowledge into sound. That is most famously executed with pulsars, the place the electrical bursts of power from a neutron star are transformed to audible pops. Astronomers have additionally transformed phenomena such because the turbulent aurora of Jupiter, or the wail of a distant nebula. These sounds may give us an emotional connection to the cosmos, however identical to the scene from “Contact,” they’re merely a poetic interpretation of the radio mild we seize.