The aliens are silent because they're dead

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Witness
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Re: The aliens are silent because they're dead

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To accelerate some mass to near-relativistic speed you'll also need energy, roughly as much as the mass itself (E = mc2). Then that again to brake. So the spaceship would need to start with enormous reserves of matter + antimatter, convert that with ~ 100 % efficiency, shield the crew (or computer) from the radiation, bleed the residual heat away, and a drive without propellant (the famed "photon drive"?).

No way. :(
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Re: The aliens are silent because they're dead

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Abdul Alhazred wrote:Note: Within your own inertial frame of reference there is no increase in mass.
Then how come I keep gaining weight?
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Re: The aliens are silent because they're dead

Post by Abdul Alhazred »

shemp wrote:
Abdul Alhazred wrote:Note: Within your own inertial frame of reference there is no increase in mass.
Then how come I keep gaining weight?
Facing the wrong direction on the escalator again?

It's the Coriolis forces + something about being big boned. :mrgreen:
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Re: The aliens are silent because they're dead

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gnome wrote:Well damn. Tell Amber she won't be able to quit early that night after all.

Seriously though, I just found a loophole in relativity--surely some plain Newtonian hurdle like micrometeors won't prove an insurmountable obstacle.

Thank god we invented the... whatever... that keeps those from damaging the ship. Maybe something mounted on the front that deflects them. A dish of some kind.
Nominally, according to lots of Sci-fi anyway, you'd want a huge electromagnetic field projecting out the front of the spaceship to "funnel in" all the Hydrogen atoms in the forward path of your ship and use that as fuel for your fusion generator.

There are between 0.1 to 1.0 atoms/cm2 in our local area (and ~1000 near the galactic core). It is a [not quite] trivial calculation to establish just how big/strong that field would have to be at any given speed to provide enough fuel to continue acceleration. https://hypertextbook.com/facts/2000/DaWeiCai.shtml

Maybe the pretend electromagnetic field that powers the pretend fusion generator on the pretend spaceship can also deflect the decidedly real spacedust.
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Re: The aliens are silent because they're dead

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Well there you go then!

Musk can start selling tickets.
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Re: The aliens are silent because they're dead

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Additional information:
Fermi famously asked: 'Where is everybody?' Probably dead, says renewed Drake equation
The Register
...

A team led by physicist Claudio Grimaldi of the Federal Polytechnical School of Lausanne in Switzerland – including Dr Drake himself – has suggested an update to the equation to take into account the time a civilisation might broadcast electromagnetic radiation that could be detected by Earthlings.

By considering the time between when a civilisation begins broadcasting to when that civilisation stops, the team is able to theorise a bubble expanding outwards at the speed of light.

The shell of the bubble is of a constant thickness, based on how long the civilisation endured.

For civilisations that blew themselves to bits after only a few hundred years, the thickness of this shell will be vanishingly small, making detection by Search for Extraterrestrial Intelligence (SETI) initiatives highly unlikely.

The paper suggests that civilisations that survive for 100,000 years or more will leave a shell thick enough to be spotted by SETI.

Anything less than that and the volume of the electromagnetic waves will be smaller than the galaxy, limiting detectability.

...
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Re: The aliens are silent because they're dead

Post by Rob Lister »

Anaxagoras wrote: Mon Feb 19, 2018 2:15 am
Rob Lister wrote:
gnome wrote:Someone may need to do some actual math here, but I think there's a sort of relativistic loophole for stubborn interstellar travelers.

Let's talk about a 10,000 year journey to another star. At sufficient acceleration (and my understanding is these effects occur even with reasonable acceleration rates such as 1g), the time it takes seems shorter to the people on board. So (and I'm pulling it out of my ass here) let's say it only took 10 years from the POV of the crew. You could get out there, take a week for sightseeing and alien hookers, and then return only 20 years later by your time. However, it would be 20,000 years later Earth time when you arrived.

Have I got that right?
That's true
To achieve your 1000:1 dilation, you'll need a relative velocity 99.99% c.
Even slightly less, like 299700 km/s gets you only a 40:1 dilation. http://keisan.casio.com/exec/system/1224059993

It would [only] take you 12 months of constant acceleration at your 1 G to reach that speed. http://www.smartconversion.com/unit_cal ... lator.aspx

But ...

Somewhere around 1 month into your mission you're traveling at about 1/10th c. You're starting to notice something funny is going on. There's a funny smell. It's you! Those micrometeoroids that normally just pit the spaceship like a sandblaster at 10 k/s are now hitting you at 30,000 k/s, and of course going right through.

The moral of the story is: Meatbags ain't going nowhere. https://arxiv.org/pdf/1503.05845v1.pdf
I think there's also a corresponding mass increase such that if time dilation is 2:1, for example, your mass has effectively doubled, and at 40:1 your mass is 40 times heavier. (This is what I'm relying on.) Thus, the closer you approach to C, the more energy you need to get additional acceleration. I do wonder if some kind of electromagnetic field around the ship could deflect those micrometeoroids?
Maybe, but it's worth pointing out that the micrometeoroids are also 40 times more massive. Unprotected, I think you'd be little more than goo in an hour or so.

WTF, why the necro-bump, you ask?

Related topic
Scientists Have Surprisingly Specific Answer on Alien Life

Study estimates 36 alien civilizations exist in our galaxy capable of communicating with us

(Newser) – Asked the meaning of life, the supercomputer in the Hitchhiker's Guide to the Galaxy came up with a very specific answer: 42. Tasked with a different Big Question—how many intelligent alien civilizations exist in our galaxy—real-life scientists have gotten just as specific: 36. That's the estimate from a team of researchers out of the University of Nottingham in England, reports the Guardian. The estimate is based on a big assumption: that life elsewhere in the Milky Way would form in generally the same way as it did on Earth. Starting from that premise, researchers crunched data on existing stars, exoplanets, conditions, etc., and came up with a range of four to 211, with 36 being the most likely number, according to the study in the Astrophysical Journal.

"The classic method for estimating the number of intelligent civilizations relies on making guesses of values relating to life, whereby opinions about such matters vary quite substantially," says co-author Tom Westby. He's referring to the long-standing Drake equation, which results in not-so-helpful estimates ranging from zero to billions, per a news release. "Our new study simplifies these assumptions using new data, giving us a solid estimate of the number of civilizations in our galaxy." Alas, the study figures the nearest one to be 17,000 light-years away, making communication a little difficult. Researchers estimate our own civilization would have to last more than 6,000 years before any two-way communication could take place. A weak point of the study? That original assumption that Earth is a handy model, a skeptical scientist tells Live Science. (Read more discoveries stories.)
https://www.newser.com/story/292298/sci ... -life.html

I don't understand the 6000year number.
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Re: The aliens are silent because they're dead

Post by Abdul Alhazred »

Hmm.

From 4004 BC to AD 2020 is just over 6000 years.

Our students of creationism will get the 4004 BC reference. :)
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Re: The aliens are silent because they're dead

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17,000 light years is pretty damn far and obviously it means that any kind of communication would take 17,000 years. Each way. Thus 34,000 years to send a message and get a reply, minimum.

But I also doubt their model. Maybe 6,000 is if the number of civilizations is on the high end of the range.
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Re: The aliens are silent because they're dead

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There's no reason to assume that another planet like earth would produce a technological civilization like our own. It took life on earth billions of years to produce a single intelligent technological species. I bet that life is fairly common but that intelligent life is rare. And certainly not an inevitable result of evolution. Cockroaches are probably better adapted than we are for long term sustainability.
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Re: The aliens are silent because they're dead

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I bet a cockroach thinks it pretty fucking smart.

As far as communication goes, just detecting it is one form, I suppose. Being able to analyze the atmosphere will tell us if there is life, or recent intelligent life if there are fluorocarbons and the like.

The most farthest exoplanet so far discovered is SWEEPS J175902.67−291153.5, at 27,710 light years.(wiki)
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Re: The aliens are silent because they're dead

Post by Abdul Alhazred »

Anaxagoras wrote: Wed Jun 17, 2020 2:25 pm Cockroaches are probably better adapted than we are for long term sustainability.
Ergo we're all alone, but in our explorations some cockroaches will inevitably hitch a ride.
They will find brand new chums waiting for them in every corner of the universe. :)
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Re: The aliens are silent because they're dead

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Unfortunately being able to fill in more of the variables in Drake's Equation than thirty years ago doesn't make us any more confident of the major unknowns still present. For anything involving the development of life, we still have a sample size of one.
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Re: The aliens are silent because they're dead

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Intead of approaching the question in such an abstract way, what if we look for nearby stars that look similar to our own sun?

What's the closest one? How far away are the closest 10, the closest 100?

Stars within say .85-1.1 solar masses not in binary system?
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Re: The aliens are silent because they're dead

Post by Abdul Alhazred »

Tau Ceti is the closest star that is of the same type as our sun.

No major planets but a helluva big asteroid belt. Perfect for colonization by Belters, if we had any Belters and a way to get there. :)
Larry Niven fans will know about Belters. Rough hewn folks perfect for space westerns. 8)

I seem to recall I science fiction story in Galaxy Magazine (1950s or early 1960s -- I inherited my father's collection) where humanity has been spreading around the the outer rim of the Milky Way for thousands of years. At the time of the story, finally finally finally a spacefaring alien species is discovered. The socko ending is it was humanity coming the other way around. :coolspecs:
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Re: The aliens are silent because they're dead

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To meet in ritual combat, so as to decide whether the Path of Now and Forever, or the Eternal Doctrine, is supreme.

Wait, that's Star Control universe.
"If fighting is sure to result in victory, then you must fight! Sun Tzu said that, and I'd say he knows a little bit more about fighting than you do, pal, because he invented it, and then he perfected it so that no living man could best him in the ring of honor. Then, he used his fight money to buy two of every animal on earth, and then he herded them onto a boat, and then he beat the crap out of every single one. And from that day forward any time a bunch of animals are together in one place it's called a zoo! (Beat) Unless it's a farm!"
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Re: The aliens are silent because they're dead

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gnome wrote: Thu Jun 18, 2020 4:07 pm To meet in ritual combat, so as to decide whether the Path of Now and Forever, or the Eternal Doctrine, is supreme.

Wait, that's Star Control universe.
Also Cap'n Kirk + Gorn (who we now know is Lurch). :)
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Re: The aliens are silent because they're dead

Post by Abdul Alhazred »

OK back to reality.

Telescope finds no signs of alien technology in 10 million star systems
Space Daily
A radio telescope in outback Western Australia has completed the deepest and broadest search at low frequencies for alien technologies, scanning a patch of sky known to include at least 10 million stars.

Astronomers used the Murchison Widefield Array (MWA) telescope to explore hundreds of times more broadly than any previous search for extraterrestrial life.

The study, published in Publications of the Astronomical Society of Australia, observed the sky around the Vela constellation. But in this part of the universe at least, it appears other civilisations are elusive, if they exist.

The research was conducted by CSIRO astronomer Dr. Chenoa Tremblay and Professor Steven Tingay, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR).

Dr. Tremblay said the telescope was searching for powerful radio emissions at frequencies similar to FM radio frequencies, that could indicate the presence of an intelligent source.

...
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Re: The aliens are silent because they're dead

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I always assumed that any signal received would need to be aimed at us and at a huge power level.

Fid looks out window just to make sure the Overlords haven't arrived thus rendering 2020 truly sucks.
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Re: The aliens are silent because they're dead

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Not surprised. It's like Fid says, even if they were there somewhere among the 10 million stars surveyed, I don't think it's likely that even an array of powerful radio telescopes would actually be able to pick up any signals from them.
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