What if we were visited by aliens?

[DanMRaymond]

What if beings from some far end of space were to visit the Earth? What would the Christian response be?

[thomasdixon]

That's still a long time traveling through an awful lot of empty space. Energy is never free and the faster you go the more you need.

When you are traveling through a vacuum, there is no resistance holding you back, slowing you down.
You can use the grab of gravity to change your direction and speed while not expending any energy of your own.
The Cassini spacecraft did not use fuel to change its path yet it traveled millions of miles and changed its direction many times.
Cassini Spacecraft Flight Path (theplanetstoday.com)
https://solarsystem.nasa.gov/resources/ ... rajectory/

[benchwarmer]

Since there are billions of stars out there and planets much liker ours circling many of those suns the odds that there is no life out there is near “zero”; most likely there is life out there.

And I believe that with the tyranny of distance and the limitations of light speed, we will never encounter any of that life.

Given enough time those vast distances are pretty much irrelevant. Even at half of light speed you could circle the galaxy twice in a million years, and it's entirely plausible that advanced civilizations could have developed hundreds of millions of years ago.

That's still a long time traveling through an awful lot of empty space. Energy is never free and the faster you go the more you need. There are just too many things that have to line up right and the probability drops to almost zero in my book.

Given what we know, I'm with you. However, we don't know what we don't know

We do know that gravity can curve space/time. If somehow some advanced civilization has discovered a useable way to curve space in such a way as to travel great linear distances in a short amount of time, then the linear distance may not be a problem anymore. Just wild guessing and musings of course.

Clearly there is 'something' routinely busting US military airspace at will and the US government has now admitted they have no clue what it is. Some of these UAPs appear to be breaking our understanding of physics. None of this means we have actually been visited, but it sure fun to think about "well, what if we have/are?".

[thomasdixon]

Clearly there is 'something' routinely busting US military airspace at will and the US government has now admitted they have no clue what it is. Some of these UAPs appear to be breaking our understanding of physics. None of this means we have actually been visited, but it sure fun to think about "well, what if we have/are?".

America, China and others have sent out “probes” to photograph and listen to noises coming from somewhere. Knowing this it stands to reason that others use probes as well.
What our Airforce and others may have seen are foreign “probes”, just looking and recording.

A space probe, or simply probe, is a robotic spacecraft that doesn't orbit the Earth, but instead explores farther into outer space. A space probe may approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; or enter interstellar space. Wikipedia

https://en.wikipedia.org/wiki/Space_probe
(:-

[DrNoGods]

[Replying to thomasdixon in post #52]

The Cassini spacecraft did not use fuel to change its path yet it traveled millions of miles and changed its direction many times.
Cassini Spacecraft Flight Path (theplanetstoday.com)

Yes, but gravity assists like this still don't allow any controllable velocity increases that approach significant fractions of the speed of light. The New Horizons (Pluto) probe got to about 40,000 MPH this way, and both Voyagers move at about that speed (a little under), but after 43 years the most distant Voyager is only 21 light hours from Earth (14.2 billion miles, or 0.000585 of the distance to the closest star to Earth):

https://voyager.jpl.nasa.gov/mission/status/

It is a balancing act to get close enough to the planet with the correct spacecraft velocity to pick up more speed as well as the desired trajectory change, and not get too close to be sucked into the planet (especially if it is a big one like Jupiter). There is a limit to how much speed increase is possible this way.

We do accelerate things on Earth to 0.99999999 of the speed of light, but these are protons whose rest mass is miniscule, and the energy input to get a bunch of protons going that speed is over 13 TeV at the Large Hadron Collider:

https://en.wikipedia.org/wiki/Large_Hadron_Collider

It just takes a tremendous amount of energy to get to even 1% of the speed of light for something like a spacecraft big enough to hold instrumentation (electronics, optics, or anything like a person). It is a challenge we are far away from reaching. But maybe there are civilizations out there who have done it ... we simply do not know, and if they have they apparently have no interest in contacting us Earthlings via any method we understand (if they happened to even find our tiny dot of a planet in the first place and decide it was of interest for some reason).

[DrNoGods]

[Replying to JoeyKnothead in post #49]

You've never had the pretty thing throw her a skillet at ya.

Not a skillet, but she does have other options. She's an astronomer so would probably opt for one of her portable telescopes which could do just as much damage.

[Tcg]

That's still a long time traveling through an awful lot of empty space. Energy is never free and the faster you go the more you need.

When you are traveling through a vacuum, there is no resistance holding you back, slowing you down.
You can use the grab of gravity to change your direction and speed while not expending any energy of your own.
The Cassini spacecraft did not use fuel to change its path yet it traveled millions of miles and changed its direction many times.
Cassini Spacecraft Flight Path (theplanetstoday.com)
https://solarsystem.nasa.gov/resources/ ... rajectory/

The Nuclear Heart of Cassini

When the pioneering NASA spacecraft met its end in Saturn’s upper atmosphere the morning of Sept. 15, 2017 (Earth Received Time), burning up in a fireball of silicon and metal, the last components to disintegrate were some of its most essential: pods of exceedingly rare and vital nuclear fuel that made the mission possible.

Those components were the iridium-clad pellets of plutonium-238 developed by the Department of Energy decades ago. Contained within three cylindrical power sources called radioisotope thermoelectric generators (RTG), they produced the heat and electricity that kept Cassini on track and responsive throughout its long journey.

https://www.energy.gov/articles/nuclear-heart-cassini

<bolding mine>

Gravity was used to increase Cassini's velocity, but as can be seen from the quote above it had a fuel system of it's own.


Tcg

[benchwarmer]

America, China and others have sent out “probes” to photograph and listen to noises coming from somewhere. Knowing this it stands to reason that others use probes as well.
What our Airforce and others may have seen are foreign “probes”, just looking and recording.

That is certainly possible. The trouble is, some of these 'probes' are exhibiting behavior that does not seem to jive with modern physics.

I wonder which is actually scarier to the military:

1) A foreign adversary having technology so far advanced it can occupy your airspace with impunity.

2) An extraterrestrial civilization flying probes wherever they like.

My guess is (1) gives them nightmares, (2) is annoying, but as long as they are not shooting at us, who cares.

[Mithrae]

[Replying to Mithrae in post #43]

Half the speed of light is still about 335 million miles per hour (MPH), and the amount of energy required to get something to that speed that having a mass of only 1 kg is about 1.4e16 Joules (eg. 4.4 million watts expended continuously for 100 years).

The fastest thing us humans have put into space to date is the Parker solar probe which will max out at about 690,000 km/hr (430,000 MPH), which is only 0.063% of the speed of light. At that speed it would take about 6,700 years just to get to the closest star to Earth (4.2 light years away), and 41 million years to get to the center of our own galaxy, and another roughly 80 million to get to the other side of our galaxy.

There may be some civilizations out there waaaayyy more advanced than we are that have developed some kind of fantastic energy source and propulsion systems completely foreign to us, but the energy required to accelerate just a 1 kg mass to "even half of light speed" is tremendous. I would argue that the distances are not irrelevant even with hundreds of millions of years of time, because of the giant hurdle of getting something of realistic mass for an investigative probe to a significant fraction of the speed of light.

Of course regarding our current technology, you're right. We'd need generation ships or a few more decades' advances in cryogenics to contemplate interstellar transit.

690,000km/hr? Hah! But then... a hundred years ago the fastest we could manage was about 200km/hr. I'm not up to speed on all this stuff but you say that even in terms of space probes, this Parker probe is over ten times faster than the Voyager probes, just a few decades later. So I'm a little sceptical of suggestions that a civilization with hundreds or even thousands of years' further development won't continue to improve on that. It seems reasonable (though far from certain) to assume that light speed will always remain a hard limit - that even if physically possible in theory, wormholes, warp drives or the like will always be technicologically impossible - but supposing that a modest fraction of light speed will always be unattainable seems like a stretch. Even at a measly 1% of light speed it'd take a mere ten million years for a species to expand throughout the galaxy, barely a blip in the span of many of earth's 'living fossil' species.

The problem isn't distance, simply time; and hence by implication the frequency, longevity and expansion tendencies of advanced civilizations, all of which are unknowns (though we can speculate a little on the latter two).



As to the effect on Christianity if we were visited? Some particularly parochial branches aside, I'm not sure it'd make much difference. The bible is pretty explicit about the supposed existence of at least some heavenly beings, both benign and hostile. It wouldn't take much reinterpretation for most Christians to work it all in.

[DrNoGods]

[Replying to Mithrae in post #59]

690,000km/hr? Hah! But then... a hundred years ago the fastest we could manage was about 200km/hr. I'm not up to speed on all this stuff but you say that even in terms of space probes, this Parker probe is over ten times faster than the Voyager probes, just a few decades later. So I'm a little sceptical of suggestions that a civilization with hundreds or even thousands of years' further development won't continue to improve on that.

I expect we'll continue to improve on that going forward ourselves, but it is a nonlinear process as far as the energy required to get each additional km/hr. The faster you go, the more incremental energy is required to gain each extra km/hr, which means more fuel and the added weight of that, etc. The Parker probe gets it huge max velocity via 7 gravity assists around Venus over a 7 year period, along with the trememdous gravitational pull of the sun (which represents 99.86% of the total mass in our solar system). This "yo-yo" effect would not be feasible for a lone spacecraft travelling to some distant galaxy, or even to Alpha Centauri, but might could be used as a "slingshot" boost to get started.

If there is life out there somewhere we have no idea what capabilities it may have. If the most probable form of life is microbial life of some sort, then it may take millions or billions of years for them to even get to the point of multicellular organisms (as it did on Earth), much less the ability to build space craft. In any case, if there is intelligent life out there we've yet to detect it, and it has yet to contact us via some method we understand. So it is pure speculation as to what capabilities such life may have, if any, for interstellar travel.

... but supposing that a modest fraction of light speed will always be unattainable seems like a stretch. Even at a measly 1% of light speed it'd take a mere ten million years for a species to expand throughout the galaxy, barely a blip in the span of many of earth's 'living fossil' species.

I didn't suggest this would "always be unattainable", just that the only advanced civilization we know about (us) is nowhere near getting there and we can't assume the existence of any advanced civilizations with even our level of capability (poor as it may be compared to Star Trek).

The problem isn't distance, simply time; and hence by implication the frequency, longevity and expansion tendencies of advanced civilizations, all of which are unknowns (though we can speculate a little on the latter two).

But distance and time are directly related when it comes to getting from point A to point B (x = vt). If we ever encounter an advanced civilization besides our own, hopefully they are friendly and will let us continue to exist on our little planet (if we don't ruin it before they get here) unable to travel even to our nearest star.

[thomasdixon]

When the human race decides to leave our planet, we will do it by way of a spaceship “arc”. It will be self-sustaining with all the needs humans need to survive.
The arc will glide most of the way and use gravity to sling it in different directions.
Entire generations will live, die and their offspring will carry on for multiple generations. The concept of earth will only be found in history books while new books will cover the journey into tomorrow.
Or so it seems to me
(:-

arc2.png