Yes, scientists have detected a background “hum” of gravitational waves pervading the universe, a constant, pervasive vibration caused by the collisions and mergers of massive objects like supermassive black holes. While this cosmic hum is inaudible to human ears, it serves as a deep, low-frequency sound of the cosmos, offering a new way to study its large-scale structure and the evolution of galaxies and black holes.
What is the hum?
It is the collective sound of low-frequency gravitational waves, which are ripples in the fabric of spacetime.
These waves are created by cataclysmic events such as pairs of supermassive black holes spiraling and merging together.
How was it detected?
Scientists used arrays of pulsars—rapidly rotating neutron stars—as giant, cosmic antennas.
By observing the tiny, minute delays in the arrival of pulses from these pulsars over many years, astronomers detected inconsistencies in the timing that indicated the presence of gravitational waves.
What does the hum tell us?
The detection of this background hum provides a new "window" for studying the universe.
It offers new clues about how galaxies evolve and how supermassive black holes form and merge.
Why can't we hear it?
The frequencies of these gravitational waves are far too low to be heard by the human ear.
Sensitive instruments are required to detect these subtle vibrations in space and time.
Is there really a universal hum?
Does the earth hum too?
Yes. Heard as a low, rumbling, or droning sound, similar to a truck or engine idling, only 2% of the population report hearing it.
What could it be?
Environmental and geological sources:
Ocean waves: In 2015, French scientists proposed that ocean waves colliding with continental shelves could cause the Earth to vibrate, creating a low hum.
Seismic activity: Natural seismic activity, including volcanic eruptions and microseisms, can produce low-frequency vibrations.
Atmospheric resonance: Electrical charges from lightning strikes have been proposed as a source of atmospheric resonance.
Physiological and internal factors:
Hyperacusis: This condition, an oversensitivity to certain frequencies, could make individuals more aware of innocuous background noises that most people filter out.
Spontaneous otoacoustic emissions (SOAE): Some people's ears naturally produce faint sounds, which could be confused with an external hum.
There is no evidence to support that extraterrestrials are producing the hum, that remains in the realm of speculation and conspiracy theory.
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