On October 19, 2017, astronomers at the University of Hawaii spotted a strange object travelling through our solar system, which they later described as "a red and extremely elongated asteroid." It was the first interstellar object to be detected within our solar system; the scientists named it 'Oumuamua, the Hawaiian word for a scout or messenger. The following October, Avi Loeb, the chair of Harvard's astronomy department, co-wrote a paper (with a Harvard postdoctoral fellow, Shmuel Bialy) that examined 'Oumuamua's "peculiar acceleration" and suggested that the object "may be a fully operational probe sent intentionally to Earth's vicinity by an alien civilization." Loeb has long been interested in the search for extraterrestrial life, and he recently made further headlines by suggesting that we might communicate with the civilization that sent the probe.
Isaac Chotiner of The New Yorker has interviewed Loeb, who was frustrated that scientists saw 'Oumuamua too late in its journey to photograph the object. "My motivation for writing the paper is to alert the community to pay a lot more attention to the next visitor," he told Chotiner. An excerpt from the interview: The New Yorker: Your explanation of why 'Oumuamua might be an interstellar probe may be hard for laypeople to understand. Why might this be the case, beyond the fact that lots of things are possible?
Loeb: There is a Scientific American article I wrote where I summarized six strange facts about 'Oumuamua. The first one is that we didn't expect this object to exist in the first place. We see the solar system and we can calculate at what rate it ejected rocks during its history. And if we assume all planetary systems around other stars are doing the same thing, we can figure out what the population of interstellar objects should be. That calculation results in a lot of possibilities, but the range is much less than needed to explain the discovery of 'Oumuamua.
There is another peculiar fact about this object. When you look at all the stars in the vicinity of the sun, they move relative to the sun, the sun moves relative to them, but only one in five hundred stars in that frame is moving as slow as 'Oumuamua. You would expect that most rocks would move roughly at the speed of the star they came from. If this object came from another star, that star would have to be very special.
[...]The New Yorker: Hold on. "'Not where is the lack of evidence so that I can fit in any hypothesis that I like?' " [Bailer-Jones, of the Max Planck Institute for Astronomy, in Heidelberg, Germany, has identified four possible home stars for 'Oumuamua, and was asked to respond to Loeb's light-sail theory by NBC.]
Loeb: Well, it's exactly the approach that I took. I approached this with a scientific mind, like I approach any other problem in astronomy or science that I work on. The point is that we follow the evidence, and the evidence in this particular case is that there are six peculiar facts. And one of these facts is that it deviated from an orbit shaped by gravity while not showing any of the telltale signs of cometary outgassing activity. So we don't see the gas around it, we don't see the cometary tail. It has an extreme shape that we have never seen before in either asteroids or comets. We know that we couldn't detect any heat from it and that it's much more shiny, by a factor of ten, than a typical asteroid or comet. All of these are facts. I am following the facts.
Last year, I wrote a paper about cosmology where there was an unusual result, which showed that perhaps the gas in the universe was much colder than we expected. And so we postulated that maybe dark matter has some property that makes the gas cooler. And nobody cares, nobody is worried about it, no one says it is not science. Everyone says that is mainstream -- to consider dark matter, a substance we have never seen. That's completely fine. It doesn't bother anyone.
But when you mention the possibility that there could be equipment out there that is coming from another civilization -- which, to my mind, is much less speculative, because we have already sent things into space -- then that is regarded as unscientific. But we didn't just invent this thing out of thin air. The reason we were driven to put in that sentence was because of the evidence, because of the facts. If someone else has a better explanation, they should write a paper about it rather than just saying what you said.
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