What is the 'static noise' on Radio or TV when it is untuned?

Question

If you untune your radio you get a noise like a box of rice crispies being shaken about. The same if you untune your television.

What is this? Why isn't it just silent? Where is the noise coming from?

Answer 1

Best Answer - Chosen by Asker

Believe it or not, a small pecentage of it is the reverberations from the big bang .
For more about this read on(from the web):

In 1965, Arno Penzias and Robert Wilson published a scientific study which proved that a radio signal with a wavelength of 7.3 cm was being emitted uniformly throughout all parts of the sky. This signal became known as cosmic microwave background radiation. Penzias and Wilson won the Nobel Prize in physics in 1978 for their findings. It is believed that this cosmic static is comprised of photons of energy that are still cooling 15 billion years after the Big Bang. If you turn a television to a channel with no station, you will see this static and given the level of intelligence of most TV programs, this static is about the only thing worth watching.

The Big Bang is the theory about the creation of the universe. This idea holds that some cataclysmic event caused all energy and space to be formed at once. Energy and space was fine, but no matter could exist because after such an explosion, the universe was still too hot. Over the course of time, the universe began to cool enough so that neutrons and electrons could attach to each other and form atoms which then became matter. Matter eventually would become planets and then atmospheres and then plants and then dinosaurs and mammals and then people and then Baywatch.

However, before all this, along with the particles of atoms (neutrons and electrons), particles of light (photons) where also formed. These photons, still hot from the Big Bang, could never fully interact with the atoms and are still cooling even now. This residual heat is still present in the world today and because television can pick up stray electromagnetic waves, a TV set can show the residual radiation of the universe. TV static is anywhere from 1/3 to 1/4 background radiation.

How is it possible that a television set can actually show cooling photons? Well, lets look a little closer at how the modern television works.

In 1925, Philo Farnsworth perfected a system he called "image dissection" which formed the backbone of modern television. Farnsworth's original dissector would break down an image into 150 lines and then scan it 30 times per second. The transmittable image he produced was much cleaner and clearer than anything researchers had done until that point. Ironically, the image Farnsworth chose to send of his new invention was the dollar sign symbol.

This image scanning technique, called interlacing, is how the TV shows movement. Small red, green and blue dots of light, called pixels, are painted on the TV screen 30 times per second. This tri-beam of color is produced by an "electron gun" which actually shoots colors onto the screen and then into your eyeball. Most modern TVs usually have around 525 lines, which means that since each line is painted in color 30 times a second, then the electron gun paints 15,750 lines per second. This is why images seem to move smoothly around the screen.

When the television shows static it is showing the ever-present background radation, so the electron gun is shooting colors at the screen in a random order.

When you are watching TV, you are watching static. The TV signal is not perfect, there are always small random electrons that go astray when the images are shot onto the screen. Digital television has improved on the problem, but you will always be exposed to the random fuzz in a normally fluid signal. You may not see it, but the background radiation is always there. So the static is always there.

Watching static on TV will give you a headache, so watching TV programs will give you a headache. Television is often referred to as "mindless entertainment." This has got to be true, because if you try and engage your brain, it's liable to start hurting

Asker's Rating:

Asker's Comment:

Very concise and interesting

Answer 2

The first answer is essentially correct. I would just add that the noise you hear when your radio is "untuned" is called white noise and it is in fact receiving spurious radio frequencies upon which nothing is being broadcast and therefor the "signal to noise ratio" is very poor and all you hear is the white noise.

Answer 3

thermal noise generated in the radio or tv.

thermal noise in our atmosphere.

cosmic noise. some of it is comic background radiation from the big band.

Answer 4

In the old TVs and Radios (not digital or cable), the TV snow and accompanying hiss is the sound of Microwave Background Radiation left over from the Big Bang.

May 13, 1965 -- Day we "heard" the Big Bang

By the second half of the 20th century, the Big Bang concept was alive and well, but it got a considerable boost in 1965, when two young radio astronomers stumbled across its afterglow.

In that year, Arno Penzias and Robert Wilson, of Bell Laboratories, discovered a source of irremovable static in a sensitive microwave antenna in Holmdel, New Jersey. Try as they might to get rid of possible sources of the noise -- and going so far as to scrape off the droppings from a nearby set of roosting pigeons -- it persisted from season to season.

Meanwhile, Robert Dicke and David Wilkinson at nearby Princeton University were haplessly trying to build an antenna to detect this very noise.

Finally, the four minds met, and Dicke and his group told an astonished Penzias and Wilson what the noise was: the microwave background of radiation that exists as a remnant of the Big Bang.

On May 13, Penzias and Wilson submitted their findings to the Astrophysical Journal and, though they didn't speculate much about the source of the noise in their paper, they were awarded the Nobel Prize for the discovery 13 years later.

Since then, the Cosmic Microwave Background, as it has become known, has been measured with great precision. In fact, you've probably observed it -- albeit unwittingly. The static "snow" that used to show up on TV screens after stations went off the air in the pre-cable era was made up of microwave background photons, some of which had their origin in the Big Bang.

Answer 5

Mark is right! Its radioactive waste.

Answer 6

It's Cosmic Microwave Background Radiation. Our best evidence for the Big Bang.
http://www.astro.ubc.ca/people/scott/cmb…

It's the "first light" that over time and distance has stretched out from gamma to radio (which includes microwave) wavelengths. And it's coming from everywhere around us.

The radiation itself is silent but our TVs and Radios pick it up (since that is what they're designed to do) and turn it into sound for us.

Answer 7

The noise is the random broadcasting of radio signals from other planets in outer space trying to contact us here on Earth. Trouble is we have so much microwave radiation of our own so the signals are not picked up and understood. One way to get round this and discover the meaning of the signals is to sit with your head against the screen and try to tune your Brain to the messages.

Answer 8

When the signal is low snow comes on the TV and static on the radio.
It's signal to noise ratio.

Answer 9

Because when the radio wave comes, some are not picked up and cannot make a perfect signal so itt cannot make it a perfect sound.

Answer 10

radio waves are just light waves (outside the visible spectrum). These frequencies occur naturally. Since your radio is designed to pick up radio frequencies, it's going to pick up the natural ones as well as the artificial ones.