Scratch Number of Galaxies... again

[Jimmy Higgins]

So, science is based on a number of things. In astronomy, most of it is based on what we see on Earth. The trouble is, the planet Earth is close to the Sun, so to speak. Which means that space... isn't as dark as it could be. This creates a problem when trying to estimate the number of galaxies in the universe (when we have little else to do). For a while, the number was estimated around 200 billion. Then around 2016, a modified study was performed in order to try and determine a more accurate number, and that estimate popped a whole magnitude. Sadly, that was still, a number that was based on very close proximity to Earth.

However, New Horizons which took the incredible images of Pluto, is far far from the sun, meaning it is darker. So some math and we get an approximated 4 trillion galaxies. Turns out there is more light to see in the deep when there is less ambient sunlight.

Everything else is a tad bit more complicated and something lpetrich can handle.

So you can put that number to memory before it crashes and burns like the others.

 

[skepticalbip]

There are 5,354,291,757,652 galaxies in the observable universe, at least by my last count last Wednesday. The problem is that I can't count the ones that are beyond the observable universe and I can't estimate their number because I can't figure out how big that beyond volume is or even if it is quantifiable.

 

[rousseau]

Somewhere out there some beautiful alien life is bickering about their version of the minimum wage and refusing to wear masks right now.

 

[Trausti]

 

[OLDMAN]

Yeah, that's a lot of galaxies....so where is everyone?

 

[Politesse]

Yeah, that's a lot of galaxies....so where is everyone?

Most of them are very far away; our ability to "see" anything in them is limited, as well as billions of years out of date.

 

[blastula]

I'm still sticking with there being 100 billion stars in the Milky Way and 100 billion galaxies in the universe, it's much easier to remember.

 

[Swammerdami]

Sheezh. 4 Trillion galaxies to choose from, and I end up here? What are the odds?

I'm still sticking with there being 100 billion stars in the Milky Way and 100 billion galaxies in the universe, it's much easier to remember.

Last I checked there were supposed to be one septillion stars in the observable universe, easy to remember. But here they go changing the numbers again.

 

[Jimmy Higgins]

I'm still sticking with there being 100 billion stars in the Milky Way and 100 billion galaxies in the universe, it's much easier to remember.

If there was life in just one in a million galaxies, and intelligent life in just one of a million of those galaxies there would be literally 4 civilizations in the entire universe.

 

[Cheerful Charlie]

Yeah, that's a lot of galaxies....so where is everyone?

They are out there. Someplace. A few of them at least. This means that the dream of faster than light travel is not possible.

 

[Politesse]

Yeah, that's a lot of galaxies....so where is everyone?

They are out there. Someplace. A few of them at least. This means that the dream of faster than light travel is not possible.

How so? Just because someone has a means of faster-than-light travel doesn't mean it is necessarily easy, cheap, or menaningful for them to transit between galaxies on a regular basis. Why would you? How would you even know which galaxies to explore in search of neighbors? We don't have any means of knowing what is presently going on in any of these galaxies at present.

 

[Swammerdami]

There's probably other life somewhere, near one of the septillion stars. But is there intelligent life in the universe?

Odds may not be good, at least for land-based life. We've thoroughly explored one planet ostensibly well-suited to advanced life, but found no trace of intelligent life except for a few species of playful ocean-based octop{uses,odes,i}.

 

[GenesisNemesis]

Yeah, that's a lot of galaxies....so where is everyone?

Separated across the vast distances of space.

 

[Jimmy Higgins]

Yeah, that's a lot of galaxies....so where is everyone?

Separated across the vast distances of space.

...and time. A civilization that existed a million years ago (heck 10,000 years!), isn't going to be contacting us any time soon. We know there have to be hundreds of thousands to billions of planets with some level of life. I wonder how many planets with intelligent life are close to other planets of intelligent life (~10 Light years). I wonder if planets or solar systems that can have intelligent life inhabit in them need a buffer, ie the stuff happening around it that effects the solar systems in a not so subtle way which provides the relative stability needed for intelligent life to evolve. Or even within the solar system. Such as, without Jupiter acting as a vacuum cleaner for asteroids, could Earth have had intelligent life?

 

[rousseau]

It's interesting that many people are fascinated about alien life in the universe, but not at all interested in the life that's happening right in front of them. If you've ever wanted to know what other intelligent life is like, look no further than yourself. And what's more, we're alive in a very short window where the internet exists and we're able to learn basically anything.

If intelligent life does or has existed elsewhere, it's probably somewhere along the trajectory of development we've seen on Earth.

 

[4321lynx]

Charlie, Jimmy, and OLDMAN,

To cheer you up skim through this: https://apod.nasa.gov/debate/debate100th.html

BUT, if you haven't already heard it, listen to the whole presentation by Martin Rees. Yes it's over an hour, but not a dull minute in it. Jill Tarter's Overview is great for beginners.

 

[bilby]

There's probably other life somewhere, near one of the septillion stars. But is there intelligent life in the universe?

Odds may not be good, at least for land-based life. We've thoroughly explored one planet ostensibly well-suited to advanced life, but found no trace of intelligent life except for a few species of playful ocean-based octop{uses,odes,i}.

...and cetaceans, corvids, great apes, parrots, etc., etc., ...

 

[SLD]

There's probably other life somewhere, near one of the septillion stars. But is there intelligent life in the universe?

Odds may not be good, at least for land-based life. We've thoroughly explored one planet ostensibly well-suited to advanced life, but found no trace of intelligent life except for a few species of playful ocean-based octop{uses,odes,i}.

One of the problems with developing intelligent life is it probably can develop on only a few stars and takes Billions of years. Just in our Galaxy, (the only place we can even hope to find it) the estimate of stars is 400 billion, but about 86% of those are red dwarfs. While those are long lasting, their habitable zone is actually too close, resulting in any planet likely to be tidally locked, or at a minimum impacted by flares. Red dwarfs are often flaring. Larger stars at least k or g size are needed. Ideally G2 as we are. These aren’t likely to exceed 40 billion scattered in the galactic plane. But remember that half of all stars are multiple systems, which are not gravitationally stable for planets to last long times. Then there’s an issue of location. Star clusters raise the risk of Supernova killing off all life every few million years.

Finally there’s the length of time it takes for intelligent life to evolve. For earth’s first four billion years it was inhospitable for the development of intelligent life. 40 billion divided by 4 billion gives 10 at any particular time period. Ten advanced civilizations scattered throughout our galaxy of 185,000 light years, means we’re not likely to find one within almost 30,000 light years from us. That’s going to be way too far away to spot at all. We’re not likely to detect such a civilization’s EM emissions. Heck I’m not sure we could detect EM emissions From Alpha Centauri at 4 light years from us.

 

[bilby]

There's probably other life somewhere, near one of the septillion stars. But is there intelligent life in the universe?

Odds may not be good, at least for land-based life. We've thoroughly explored one planet ostensibly well-suited to advanced life, but found no trace of intelligent life except for a few species of playful ocean-based octop{uses,odes,i}.

One of the problems with developing intelligent life is it probably can develop on only a few stars and takes Billions of years. Just in our Galaxy, (the only place we can even hope to find it) the estimate of stars is 400 billion, but about 86% of those are red dwarfs. While those are long lasting, their habitable zone is actually too close, resulting in any planet likely to be tidally locked, or at a minimum impacted by flares. Red dwarfs are often flaring. Larger stars at least k or g size are needed. Ideally G2 as we are. These aren’t likely to exceed 40 billion scattered in the galactic plane. But remember that half of all stars are multiple systems, which are not gravitationally stable for planets to last long times. Then there’s an issue of location. Star clusters raise the risk of Supernova killing off all life every few million years.

Finally there’s the length of time it takes for intelligent life to evolve. For earth’s first four billion years it was inhospitable for the development of intelligent life. 40 billion divided by 4 billion gives 10 at any particular time period. Ten advanced civilizations scattered throughout our galaxy of 185,000 light years, means we’re not likely to find one within almost 30,000 light years from us. That’s going to be way too far away to spot at all. We’re not likely to detect such a civilization’s EM emissions. Heck I’m not sure we could detect EM emissions From Alpha Centauri at 4 light years from us.

True. And the time window is narrow. We have only been transmitting and receiving radio signals for a century, and already the strongest emissions have largely been curtailed, as we move to more efficient systems that radiate little or no signal into deep space.

A duplicate Earth at a distance of about 50ly would be very hard to detect, despite the fact that their Cold War DEW radar signals (the most powerful signals routinely broadcast into space for more than a few hours at a time) would just now be reaching us.

A duplicate Earth at 100ly wouldn't be broadcasting anything that we could detect at all, as their radio signals wouldn't have reached us yet. A more advanced Earth at that distance might well have stopped broadcasting much radio noise long ago, and have switched entirely to directional and/or wired communications, that would be very hard to spot unless specifically intended to target our system.

 

[Bomb#20]

... Ideally G2 as we are. These aren’t likely to exceed 40 billion scattered in the galactic plane. ...
Finally there’s the length of time it takes for intelligent life to evolve. For earth’s first four billion years it was inhospitable for the development of intelligent life. 40 billion divided by 4 billion gives 10 at any particular time period. Ten advanced civilizations scattered throughout our galaxy of 185,000 light years, means we’re not likely to find one within almost 30,000 light years from us. That’s going to be way too far away to spot at all. We’re not likely to detect such a civilization’s EM emissions. Heck I’m not sure we could detect EM emissions From Alpha Centauri at 4 light years from us.

Why are you dividing 40 billion by 4 billion? To do that presumes there's something important about our 1-year time unit.

What would make dimensional sense is to say "For earth’s first four billion years it was inhospitable for the development of intelligent life; so it was hospitable for .6/4.6 billion years = 13% of the time; so estimate only 13% of G2 stars are hospitable; that's 5 billion at any particular time period." With those numbers, we're likely to find another G2 star that can support intelligent life within 20 light years.