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| The Universe is Watching Each of Us |
Have you ever wondered if there is someone out there watching us? Not just a divine being or a higher power, but a real, physical observer from another world? The idea may sound like science fiction, but it is not impossible. In fact, some scientists have suggested that we may be able to detect such cosmic watchers, or even communicate with them, by using the same tools that we use to explore the universe.
The Expanding Universe
One of the most amazing discoveries of modern astronomy is that the universe is expanding. This means that the distances between galaxies and other objects are increasing over time, as space itself stretches. The expansion of the universe was first observed by Edwin Hubble in 1929, when he measured the redshifts of distant galaxies. Redshift is the phenomenon of light waves being stretched as they travel through expanding space, making them appear redder than they actually are. The more distant a galaxy is, the more redshifted its light is, and the faster it appears to be moving away from us.
The expansion of the universe is not only a historical fact, but also an ongoing process. We can actually watch the universe expand in real time, if we are patient enough. By comparing the redshifts of distant objects over decades or centuries, we can measure how their recession speeds change over time. This would allow us to see how the expansion rate of the universe evolves, and test our theories of cosmology.
However, measuring such tiny changes in redshift is extremely challenging, even with the most advanced telescopes. Allan Sandage realized this in 1962, when he tried to detect the evolution of the expansion rate using distant galaxies. He concluded that it would be impossible to do so with the technology available at that time.
A New Approach
In 1998, Avi Loeb proposed a new approach for measuring the evolution of the expansion rate using objects that are much closer to us than galaxies: asteroids and comets. These small bodies orbit around the sun and occasionally pass close to Earth, making them easier to observe and track. Loeb suggested that by measuring the Doppler shifts of radio signals bounced off these objects, we could detect how their orbital speeds change over time due to the expansion of space.
Loeb calculated that this effect would be detectable within a decade or two, using existing or planned radio telescopes. He also pointed out that this method could be used to communicate with extraterrestrial civilizations that may be watching us from nearby stars. If we transmit radio signals towards these stars, and they bounce them back to us with a delay, we could exchange messages with them using the expansion of space as a common reference frame.
The Universe is Watching Us
Loeb’s idea may sound far-fetched, but it is not without merit. In fact, some recent studies have shown that there may be thousands of stars within our galaxy that have a direct view of Earth and its biosphere. These stars could potentially host planets with intelligent life forms that are aware of our existence and activity.
For example, in 2020, Lisa Kaltenegger and Jackie Faherty identified more than 2,000 stars within 300 light-years from Earth that have been aligned with our planet at some point in the past 5,000 years or will be in the next 5,000 years. These stars could have seen Earth transit across the sun’s disk, revealing its size, shape and atmosphere. Some of these stars may even have planets with their own transits that we could detect with future telescopes.
Another study by Abraham Loeb and Amir Siraj in 2021 estimated that there may be more than 30 interstellar objects like 'Oumuamua passing through our solar system every year. These objects could be natural or artificial probes sent by alien civilizations to explore our neighborhood. If we can intercept and examine these objects, we may find clues about their origin and purpose.
The universe is watching each of us, whether we like it or not. We are not alone in this vast cosmos, and we may have cosmic neighbors that are curious about us. We should not be afraid of this possibility, but embrace it as an opportunity to learn more about ourselves and our place in the universe. By using our scientific tools and imagination, we may be able to establish contact with these watchers, and share our knowledge and culture with them. The universe is not only expanding, but also connecting.
