I found this article very refreshing. Typically, I am very skeptical of flying saucers, etc. But this guy seems to have credentials.
Before he started the whole alien spaceship thing last year, the chairman of Harvard University's astronomy department was known for public lectures on modesty. Personal modesty, which Avi Loeb said he learned growing up on a farm. And what Loeb calls "cosmic modesty" — the idea that it's arrogant to assume we are alone in the universe, or even a particularly special species.
What you can’t call Loeb is a crank. When astronomers in Hawaii stumbled across the first known interstellar object in late 2017 — a blip of light moving so fast past the sun that it could only have come from another star — Loeb had three decades of Ivy League professorship and hundreds of astronomical publications on his résumé, mostly to do with the nature of black holes and early galaxies and other subjects far from any tabloid shelf.
So now he is famous, styling himself as a truth-teller and risk-taker in an age of overly conservative, quiescent scientists.
“The mainstream approach [is] you can sort of drink your coffee in the morning and expect what you will find later on. It’s a stable lifestyle, but for me it resembles more the lifestyle of a business person rather than scientists,” he says.
Loeb bases his hypothesis on the unusual acceleration Oumuamua underwent after its close approach to the sun. He considers it consistent with the behaviour of a lightsail, a theoretical method for interstellar travel. A lightsail is an ultra thin sheet that reflects light from a star or high power laser, gaining momentum to escape its solar system of origin. However, if a high power alien laser was used, it should have been traveling at some decent fraction of the speed of light unless it failed early in its journey. Also, it may turn out to be a measurement error, like those faster than light measurements a few years back. There is also another hypothesis that it is an ultralight conglomeration of comet dust.
ReplyDeleteI just finished a book by Stephen Hawking, I believe his last popular writing, called "Brief Answers to the Big Questions". He talks about the possibility of our using lightsails to reach out to other star systems. He finds that much more feasible than sending humans across the galaxy. Here's a passage:
ReplyDelete"The speed at which we can send a rocket is governed my two things, the speed of the exhaust and the fraction of its mass that the rocket loses as it accelerates. The exhaust speed of chemical rockets, like the ones we have used so far, is about three kilometres per second. By jettisoning 30 per cent of their mass, they can achieve as spped of about half a kilometre per second and then slow down again. According to NASA, it would take as little as 260 days to reach Mars, give or take ten days, with some NASA scientists predicting as little as 130 days . But it would take 3 million years to get to the nearest star system. To go faster would require a much higher exhaust speed than chemical rockets can provide, that of light itself. A powerful beam of light from the rear could drive the spaceship forward. Nuclear fusion could provide 1 percent of the spaceship's mass energy, which would accelerate it to a tenth of the speed of light. Beyond that, we would need either matter-antimatter anhilation or some completely new form of energy. In fact, the distance to Alpha Centauri [closest star to the sun, I think - jp] is so great that to reach it in a human lifetime a spacecraft would have to carry fuel with roughly the mass of all the stars in the galaxy ..."
Hawking then goes on to describe a new venture he entered into with entrepreneur Yuri Milner, called Breakthrough Starshot, to provide a better way:
"It is a proof-of-concept mission and works on three concepts: miniaturised spacecraft, light propulsion and phase-locked lasers. The Star Chip, a full functional space probe reduced to a few centimeters in size, will be attached to a light sail. Made from metamaterials, the light sail weighs no more than a few grams. It is envisaged that a thousand Star Chips and light sails, the nanocraft, will be sent into orbit. On the ground, an array of lasers at the kilometre scale will combine into a single, very powerful light beam. The mean is fired through the atmosphere, striking the sails in space with tens of gigawatts of power.
"The idea behind this innovation is that the nanocraft ride on the light beam much as Einstein dreamed about riding a light beam at the age of sixteen. Not quite to the speed of light, but to a fifth of it, or 100 million miles an hour. Such a system could reach Mars in less than an hour, reach Pluto in days, pass Voyager in under a week and reach Alpha Centauri in just over twenty years. ..."
The whole book is highly readable, and left me with an appreciation that Hawking not only was a great scientist and heroic in working through his disability, but he was also a great humanist. He described himself as an optimist but there are many aspects of human life on our planet that filled him with pessimism about the future of humankind. This passage I've quoted here is from a chapter entitled, "Should we Colonise Space?"
I'm presenting this passage to illustrate that Loeb didn't invent his theory out of whole cloth; the idea of a space-sailing-vessel from another star system apparently has been talked about in the physics community for some time.
Just to add a thought of my own: the odds of the Pentagon, or the Russians or the Chinese, weaponizing Hawking's powerful beam of light concept is roughly 100%, except they wouldn't use it to send sailing vessels to other galaxies; they'd mount it on satellites and point them at one another's cities.
Jim, lasers work by exploiting what's called a population inversion in a material. Normally, there are more electrons orbiting atoms at lower energy levels than higher. That means that a photon can pump an electron from lower to higher level, and be absorbed by the atom. The material will absorb light. If you hit the material with a pulse of light or an electric arc, you can end up with more electrons in higher than lower levels. This is a population inversion. A funny thing happens now. A photon hitting an atom released two photons, like a chain reaction. You line up two mirrors with the energized medium between and the beam builds up. Light amplification by stimulated emission of radiation, laser. I have wondered for a while if some of the energy in the coronasphere surrounding the sun could be harnessed this way, using mirrors in space tens of kilometers in size with the coronasphere in between. If the conditions in the coronasphere are correct, a laser of unbelievable power would result, possibly terawatts. We could send spacecraft to other stars. We could vaporize earth killing asteroids and comets. And yes, we could vaporize cities. Best we give the keys to living saints.
DeleteSeen on Facebook: "Dear earth people, please stop sending out directions to your home and naked pictures of yourselves. It's creepy."
ReplyDeleteHaha. Good one.
DeleteSpeculation like that almost makes me want to stick around. But then there is the possibility of six more years of... Call Hospice!
ReplyDeleteI'm not holding my breath for ET. My motivation to stick around is to tell the climate change deniers "I told you so". The last thing they hear as they're washed away in a 10,000 year flood or blown away in a CAT 6 hypercane. Oh yeah. I'll hang around for that.
DeleteLet's see, Stanley, I suppose it will be the third 10,000 year flood in the past five years.
DeleteYeah, Tom, we seem to be getting that a lot lately.
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