If an alien were to look at Earth, many human technologies – from cell towers to fluorescent light bulbs – could be a beacon signifying the presence of life.
We are two astronomers who work on the search for extraterrestrial intelligence – or SETI. In our research, we try to characterize and detect signs of technology originating from beyond Earth. These are called technosignatures.
While scanning the sky for a TV broadcast of some extraterrestrial Olympics may sound straightforward, searching for signs of distant, advanced civilizations is a much more nuanced and difficult task than it might seem.
Saying ‘hello’ with radios and lasers
The modern scientific search for extraterrestrial intelligence began in 1959 when astronomers Giuseppe Cocconi and Philip Morrison showed that radio transmissions from Earth could be detected by radio telescopes at interstellar distances.
The same year, Frank Drake, launched the first SETI search, Project Ozma, by pointing a large radio telescope a two nearby Sun-like stars to see if he could detect any radio signals coming from them. Following the invention of the laser in 1960, astronomers showed that visible light could also be detected from distant planets.
These first, foundational attempts to detect radio or laser signals from another civilization were all looking for focused, powerful signals that would have been intentionally sent to the solar system and meant to be found.
Given the technological limitations of the 1960s, astronomers did not give serious thought to searching for broadcast signals – like television and radio broadcasts on Earth – that would leak into space.
But a beam of a radio signal, with all of its power focused towards Earth, could be detectable from much farther away – just picture the difference between a laser and a weak light bulb.
The search for intentional radio and laser signals is still one of the most popular SETI strategies today. However, this approach assumes that extraterrestrial civilizations want to communicate with other technologically advanced life.
Humans very rarely send targeted signals into space, and some scholars argue that intelligent species may purposefully avoid broadcasting out their locations. This search for signals that no one may be sending is called the SETI Paradox.
Leaking radio waves
Though humans don’t transmit many intentional signals out to the cosmos, many technologies people use today produce a lot of radio transmissions that leak into space. Some of these signals would be detectable if they came from a nearby star.
The worldwide network of television towers constantly emits signals in many directions that leak into space and can accumulate into a detectable, though relatively faint, radio signal.
Research is ongoing as to whether current emissions from cell towers in the radio frequency on Earth would be detectable using today’s telescopes, but the upcoming Square Kilometer Array radio telescope will be able to detect even fainter radio signals with 50 times the sensitivity of current radio telescope arrays.
Not all human-made signals are so unfocused, though. Astronomers and space agencies use beams of radio waves to communicate with satellites and space craft in the solar system. Some researchers also use radio waves for radar to study asteroids.
In both of these cases, the radio signals are more focused and pointed out into space. Any extraterrestrial civilization that happened to be in the line of sight of these beams could likely detect these unambiguously artificial signals.
Aside from finding an actual alien spacecraft, radio waves are the most common technosignatures featured in sci-fi movies and books. But they are not the only signals that could be out there.
In 1960, astronomer Freeman Dyson theorized that, since stars are by far the most powerful energy source in any planetary system, a technologically advanced civilization might collect a significant portion of the star’s light as energy with what would essentially be a massive solar panel. Many astronomers call these megastructures, and there are a few ways to detect them.
After using the energy in the captured light, the technology of an advanced society would re-emit some of the energy as heat. Astronomers have shown that this heat could be detectable as extra infrared radiation coming from a star system.
Another possible way to find a megastructure would be to measure its dimming effect on a star. Specifically, large artificial satellites orbiting a star would periodically block some of its light.
This would appear as dips in the star’s apparent brightness over time. Astronomers could detect this effect similarly to how distant planets are discovered today.
A whole lot of pollution
Another technosignature that astronomers have thought about is pollution.
Chemical pollutants – like nitrogen dioxide and chlorofluorocarbons on Earth are almost exclusively produced by human industry. It is possible to detect these molecules in the atmospheres of exoplanets with the same method the James Webb Space Telescope is using to search distant planets for signs of biology.
If astronomers find a planet with an atmosphere filled with chemicals that can only be produced by technology, it may be a sign of life.
Finally, artificial light or heat from cities and industry could also be detectable with large optical and infrared telescopes, as would a large number of satellites orbiting a planet. But a civilization would need to produce far more heat, light and satellites than Earth does to be detectable across the vastness of space using technology humans currently possess.
Which signal is best?
No astronomer has ever found a confirmed technosignature, so it’s hard to say what will be the first sign of alien civilizations.
While many astronomers have thought a lot about what might make for a good signal, ultimately, nobody knows what extraterrestrial technology might look like and what signals are out there in the Universe.
Some astronomers support a generalized SETI approach which searches for anything in space that current scientific knowledge cannot naturally explain. Some, like us, continue to search for both intentional and unintentional technosignatures.
The bottom line is that there are many avenues for detecting distant life. Since no one knows what approach is likely to succeed first, there is still a lot of exciting work left to do.
Authors: Macy Huston, PhD Candidate in Astronomy and Astrophysics, Penn State and Jason Wright, Professor of Astronomy and Astrophysics, Penn State
“Alien bases” may be hiding off the coast of Alaska, researchers say
An organization of civilian volunteers dedicated to the study of
unidentified flying objects (UFOs) has issued a statement based on
decades of studying eyewitness reports. According to Mutual UFO Network,
“alien bases” may be hiding off the coast of Alaska, reports the-sun.com.
say the deep waters in this region may hold something surprising. After
analyzing reports from the ship’s crew from 1945, they hypothesized
that alien objects could be lurking underwater, off the coast of the
Alleged sightings of alien spacecraft nearly 80 years ago
have become a key point in research. Members of the organization believe
that UFOs move over water and may have “bases.”
allege crew members on a U.S. Army transporter ship sailing past Island
Adak saw a massive UFO sized 150 to 200 feet emerge from the water.
Although these reports are nowhere to be found, UFO enthusiasts believe
the unidentified flying vehicles likely were used to commute to
different supposed alien bases hiding in the deep waters.
the “secret reports” of the sailors aren’t available, investigators
have taken it upon themselves to unravel the mystery surrounding the
unidentified flying objects and they believe the ocean has alien bases
that humans aren’t aware of.
Enthusiasts claim that UFOs may be
using “underwater networks” or wormholes as superhighways to travel
between points in the universe. UFO researcher Johnny Enoch added that
such objects could serve as a vehicle for aliens.
There are also
theories that other places on Earth could serve as bases for alien life.
A mountain in Seoul, South Korea is believed to be hiding a UFO,
according to Dr. Steven Greer.
An episode of the series “The
Alaska Triangle” features satellite imagery that claims to show one of
the “alien bases” in the Pacific Ocean off the coast of California.
another researcher featured in the program showed markings from the sea
bed that she claimed could have been roadways for aliens.
the mysteries of the ocean remain unsolved, researchers continue their
search, trying to unravel the mystery of what may be hiding in the
depths of the waters off the coast of Alaska.
Enormous City-Size Comet Racing Towards Earth Grows ‘Devil Horns’ After Massive Eruption
A volcanic comet the size of a mid-sized US city has
violently exploded for the second time in four months as it continues
racing toward the earth. And following the massive eruption, the cloud
of ice and gas sprouted what looked like a pair of gigantic devil horns.
The city-sized comet, named 12P/Pons-Brooks, is a cryovolcanic — or
cold volcano — comet. It has a solid nucleus, with an estimated diameter
of 18.6 miles, and is filled with a mix of ice, dust and gas known as
cryomagma. The nucleus is surrounded by a fuzzy cloud of gas called a
coma, which leaks out of the comet’s interior.
When solar radiation heats the comet’s insides, the pressure builds up
and the comet violently explodes, ejaculating its ice-cold innards into
space through seeping cracks in the nucleus’s shell.
Live Science report:
On Oct. 5, astronomers detected a large outburst from 12P, after the
comet became dozens of times brighter due to the extra light reflecting
from its expanded coma, according to the British Astronomical Association (BAA), which has been closely monitoring the comet
Over the next few days, the comet’s coma expanded further and developed its “peculiar horns,” Spaceweather.com
reported. Some experts joked that the irregular shape of the coma also
makes the comet look like a science fiction spaceship, such as the
Millennium Falcon from Star Wars.
The unusual shape of the comet’s coma is likely due to an irregularity in the shape of 12P’s nucleus, Richard Miles, a BAA astronomer, told Live Science after the comet’s previous eruption.
The outflowing gas is likely being partially obstructed by a notch
sticking out on the nucleus, Miles said. As the gas continues to expand
away from the comet, the irregularity in the coma’s shape becomes more
defined and noticeable, he added.
12P is currently hurtling toward the inner solar system, where it
will be slingshotted around the sun on its highly elliptical 71-year
orbit around our home star — similar to the green comet Nishimura, which
pulled off a near-identical maneuver on Sept. 17.
12P will reach its closest point to Earth on April 21, 2024, when it
may become visible to the naked eye before being catapulted back toward
the outer solar system. It will not return until 2095.
This is the second time 12P has sprouted its horns this year. On July
20, astronomers witnessed the comet blow its top for the first time in
69 years (mainly due to its outbursts being less frequent and harder to
spot during the rest of its orbit). On that occasion, 12P’s coma grew to
around 143,000 miles (230,000 km), which is around 7,000 times wider
than the comet’s nucleus.
It is unclear how large the coma grew during the most recent
eruption, but there are signs the outburst was “twice as intense” as the
previous one, the BAA noted. By now, the coma has likely shrunk back to
near its normal size.
As 12P continues to race toward the sun, there is a high probability
that we will witness several more major eruptions. It is possible that
those eruptions will be even bigger than the most recent one as the
comet soaks up more solar radiation, according to Spaceweather.com.
But 12P is not the only volcanic comet that astronomers are currently
monitoring: 29P/Schwassmann-Wachmann (29P) — the most volatile volcanic
comet in the solar system — has also had several noticeable eruptions
in the last year.
In December 2022, 29P experienced its largest eruption in around 12 years, which sprayed around 1 million tons of cryomagma into space. And in April this year, for the first time ever, scientists accurately predicted one of 29P’s eruptions before it actually happened, thanks to a slight increase in the comet’s brightness in the lead-up to the icy explosion.
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