People in Puerto Rico were able to hear electrophonic sounds from the SpaceX Starship as it passed overhead on November 19, 2024.
SpaceX Starship spacecraft emits electrophonic sounds
After a successful launch on November 19, 2024, the Starship Flight 6 test mission from Starbase in southern Texas headed toward the Caribbean, then to South Africa, before ending its mission in the Indian Ocean.
About 12 minutes after launch, people in Puerto Rico took videos of the eye-catching flyby. But there was a surprise: Many observers reported that they were able to hear a low-frequency rumble while Starship was visible.
Not too loud, but detectable. In fact, observers across the Caribbean island reported the same sound.
In some videos, skywatchers commented: “I can hear the rocket,” while other observers confirmed they could also clearly hear sounds from Starship.
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Hearing spacecraft from the ground
When you look at high-flying aircraft, the sound usually seems to come from the area of the sky where the object was a few moments ago. The sound lags, because sound travels slower than the photons of light that let us see the aircraft. The same is true for lightning and thunder. We see the flash before we hear the rumble, unless the lightning is quite close by.
But with Starship, there was no delay in the low-frequency sound: Observers felt the rumble coming from the same direction of the rocket, which, in theory, should not occur because light travels faster than sound. In this case, you are looking at an object that is moving at speeds between 15,000 and 17,500 miles per hour.
So, how is this possible? The answer is electrophonic sounds.
What are electrophonic sounds?
Electrophonic sounds occur when electromagnetic energy – or waves from light and heat – interact with the ionosphere, and the waves propagate through the atmosphere at the speed of light.
This strange audible effect was first used to explain how some rare meteors can produce a hiss or low-frequency sound that can be heard in real time or with no delay, as you are seeing a meteor.
When these fast-moving waves reach Earth’s surface, objects such as trees, structures or nearby walls behave like passive speakers or acoustic reflectors, allowing observers to hear the low-frequency sounds. Studies show that even long hair, hats and sunglasses can improve someone’s ability to hear these low-frequency sounds.
On January 27, 2000, the Molniya 1-67 satellite reentered the atmosphere over western Australia, and research confirmed electrophonic sound reports, which means the audible effect is not exclusive to meteors.
Meanwhile, Starship appears to be the first rocket that can also produce the curious, real-time sound effect.
The rocket passed over a meteor camera in Puerto Rico (and thus passed by its centrally located microphone). You can slightly hear the low-frequency sounds or rumble starting around 06:12:36 on this video. (According to the time stamp at upper right.)
Bottom line: The powerful SpaceX Starship rocket emitted electrophonic sounds that observers in Puerto Rico heard as it passed overhead on November 19, 2024.
Read more: Eyewitnesses saw fiery Starship reentry over Caribbean
The post SpaceX Starship spacecraft emits electrophonic sounds first appeared on EarthSky.
from EarthSky https://ift.tt/8z427yu
People in Puerto Rico were able to hear electrophonic sounds from the SpaceX Starship as it passed overhead on November 19, 2024.
SpaceX Starship spacecraft emits electrophonic sounds
After a successful launch on November 19, 2024, the Starship Flight 6 test mission from Starbase in southern Texas headed toward the Caribbean, then to South Africa, before ending its mission in the Indian Ocean.
About 12 minutes after launch, people in Puerto Rico took videos of the eye-catching flyby. But there was a surprise: Many observers reported that they were able to hear a low-frequency rumble while Starship was visible.
Not too loud, but detectable. In fact, observers across the Caribbean island reported the same sound.
In some videos, skywatchers commented: “I can hear the rocket,” while other observers confirmed they could also clearly hear sounds from Starship.
The 2025 EarthSky lunar calendar makes a great gift. Get yours today!
Hearing spacecraft from the ground
When you look at high-flying aircraft, the sound usually seems to come from the area of the sky where the object was a few moments ago. The sound lags, because sound travels slower than the photons of light that let us see the aircraft. The same is true for lightning and thunder. We see the flash before we hear the rumble, unless the lightning is quite close by.
But with Starship, there was no delay in the low-frequency sound: Observers felt the rumble coming from the same direction of the rocket, which, in theory, should not occur because light travels faster than sound. In this case, you are looking at an object that is moving at speeds between 15,000 and 17,500 miles per hour.
So, how is this possible? The answer is electrophonic sounds.
What are electrophonic sounds?
Electrophonic sounds occur when electromagnetic energy – or waves from light and heat – interact with the ionosphere, and the waves propagate through the atmosphere at the speed of light.
This strange audible effect was first used to explain how some rare meteors can produce a hiss or low-frequency sound that can be heard in real time or with no delay, as you are seeing a meteor.
When these fast-moving waves reach Earth’s surface, objects such as trees, structures or nearby walls behave like passive speakers or acoustic reflectors, allowing observers to hear the low-frequency sounds. Studies show that even long hair, hats and sunglasses can improve someone’s ability to hear these low-frequency sounds.
On January 27, 2000, the Molniya 1-67 satellite reentered the atmosphere over western Australia, and research confirmed electrophonic sound reports, which means the audible effect is not exclusive to meteors.
Meanwhile, Starship appears to be the first rocket that can also produce the curious, real-time sound effect.
The rocket passed over a meteor camera in Puerto Rico (and thus passed by its centrally located microphone). You can slightly hear the low-frequency sounds or rumble starting around 06:12:36 on this video. (According to the time stamp at upper right.)
Bottom line: The powerful SpaceX Starship rocket emitted electrophonic sounds that observers in Puerto Rico heard as it passed overhead on November 19, 2024.
Read more: Eyewitnesses saw fiery Starship reentry over Caribbean
The post SpaceX Starship spacecraft emits electrophonic sounds first appeared on EarthSky.
from EarthSky https://ift.tt/8z427yu
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