Leaderboard

"Perhaps we can communicate with the aliens if they are aware of the EM spectrum." "We can develop the technology to capture what we need from space along the way to another system" "We can figure out new ways to communicate with alien cultures." "Aliens probably think differently." It's been a long time since I spoke any Hydrox. It's an older form of Oreo, where the middle is stressed before either end is considered.

This is how I think humans can best adapt to outer space. What you need for survival is just water-ice. If you can find a large supply of ice on an asteroid of maybe 100 miles in diameter, you can start building your space station there. You can also get a centrifuge rotating at one g gravity for crew quarters. How many g's of gravity would the workers experience working on a 100 mile diameter asteroid? If a 10 mile diameter asteroid has about ONE NANO G. Then a 100 mile diameter asteroid would have about 10 to 20 NANO G's? Anyhow it is so low a gravity that very massive volumes of ice could be moved and processed with minimal amounts of energy. You excavate the ice using laser cutters then the ice is transported to a nearby processing station that melts the water out of the rock and from the water you get oxygen for air, and hydrogen for fuel. You can start using the hydrogen fuel to power the cutting lasers and excavation. And the workers have air and water. You can fabricate ice panels for building. As you dig into the asteroid you can start building your space station INSIDE the asteroid where you dug out the ice, and you will be sheltered from cosmic rays and micro-meteors. We can use asteroids as gas stations and as stepping stones to other stars. Who cares about the Moon and Mars?

Most likely, recasting the equations in this way does not add any value.

OK, fair point. I should have read it more carefully. However there's still a difference. An army of people have been trying very hard to find problems with GR- and they have not. (Not yet, if you insist) They have made measurements to lots of significant figures and GR seems to work. So, to the best of our (current) knowledge, GR gives the right answer. So, (to the best of our current understanding )anything that disagrees with GR by more than the tiny experimental uncertainty is wrong. So either those early papers agree, or they disagree by some tiny discrepancy, or they are wrong. In which case the answer to the OP's question is "they are subsumed (if they are right) or superseded (if they are wrong) or the difference is so small that we can't measure it"

https://phys.org/news/2018-08-oort-clouds-stars-visible-cosmic.html https://en.wikipedia.org/wiki/Interstellar_object http://www-ssg.sr.unh.edu/ism/what1.html A cursory look only found listings of objects like oumuamua and or gas and dust but I have recently seen estimates of smaller ice and rock objects occuring in interstellar space, enough to be useful but I can't find them right now. I am unable to be online for long due to heath problems. I'll continue to look for the specifics at later date or with draw my claim your call... You do realise you are quoting an average of gas not objects right? And the oort cloud extends almost a light year away from the sun at least? "your own little world" would be many miles long and miles wide, rotate for internal gravity and house thousands of people. The asteroids would be the construction materials along with trojan asteroids, kuiper belt objects and or oort cloud objects. I'm not saying it would be easy but the task is well within the realm of possibility. Engineering studies were done decades ago.

There is a simple solution for that. Time. Really? We haven't gone back to the moon because it is too far away? Well thought out and presented argument. Circular logic. I agree, it is probably pointless to discuss this with you.

https://www.princeton.edu/news/2019/07/10/princeton-scientists-spot-two-supermassive-black-holes-collision-course-each-other Princeton scientists spot two supermassive black holes on collision course with each other by the Office of Communications July 10, 2019 11:13 a.m. "Astronomers have discovered a distant pair of titanic black holes on a collision course. Each black hole’s mass is more than 800 million times that of our sun. As the two gradually draw closer together in a death spiral, they will begin sending gravitational waves rippling through space-time. Those cosmic ripples will join the as-yet-undetected background noise of gravitational waves from other supermassive black holes. Even before the destined collision, the gravitational waves emanating from the supermassive black hole pair will dwarf those previously detected from the mergers of much smaller black holes and neutron stars." - more at link reference : https://iopscience.iop.org/article/10.3847/2041-8213/ab2a14

https://phys.org/news/2019-07-exoplanets-gravitational.html In a recent paper in Nature Astronomy, researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam and from the French Alternative Energies and Atomic Energy Commission (CEA) in Saclay, Paris suggest how the planned space-based gravitational-wave observatory LISA can detect exoplanets orbiting white dwarf binaries everywhere in the Milky Way and in the nearby Magellanic Clouds. This new method will overcome certain limitations of current electromagnetic detection techniques and might allow LISA to detect planets down to 50 Earth masses. In the past two decades, the knowledge of exoplanets has grown significantly, and more than 4000 planets orbiting a large variety of stars have been discovered. Up to now, the techniques used to find and characterize these systems are based on electromagnetic radiation and are limited to the solar neighborhood and some parts of the galaxy. In a recent paper published in Nature Astronomy, Dr. Nicola Tamanini, researcher at the AEI in Potsdam and his colleague Dr. Camilla Danielski, researcher at the CEA/Saclay (Paris) show how these limitations may be overcome by gravitational-wave astronomy. "We propose a method which uses gravitational waves to find exoplanets that orbit binary white dwarf stars," says Nicola Tamanini. White dwarfs are very old and small remnants of stars once similar to the sun. "LISA will measure gravitational waves from thousands of white dwarf binaries. When a planet is orbiting such a pair of white dwarfs, the observed gravitational-wave pattern will look different compared to the one of a binary without a planet. This characteristic change in the gravitational waveforms will enable us to discover exoplanets." more at link..... the paper: https://www.nature.com/articles/s41550-019-0807-y The gravitational-wave detection of exoplanets orbiting white dwarf binaries using LISA Abstract: So far, around 4,000 exoplanets have been discovered orbiting a large variety of stars. Owing to the sensitivity limits of the currently used detection techniques, these planets populate zones restricted either to the solar neighbourhood or towards the galactic bulge. This selection problem prevents us from unveiling the true galactic planetary population and is not set to change for the next two decades. Here, we present a detection method that overcomes this issue and that will allow us to detect massive exoplanets using gravitational-wave astronomy. We show that the Laser Interferometer Space Antenna (LISA) mission can characterize new circumbinary exoplanets orbiting white dwarf binaries everywhere in our Galaxy—a population of exoplanets so far completely unprobed—as well as detecting extragalactic bound exoplanets in the Magellanic Clouds. Such a method is not limited by stellar activity and, in extremely favourable cases, will allow LISA to detect planets down to 50 Earth masses.

You can use emission or absorption spectroscopy if the source is emitting light (e.g. a star, which is incandescent), but for a cold, dark object that's a much harder proposition.

I have lost track of current star estimates. I believe they keep increasing. Milky Way estimated at 400 billion? Galaxies estimated at 2 trillion (observable universe)? The enormous quantities sure imply, to me anyway, that we are not alone. Elapaed time sure does shake things up. As hinted at, in this thread, the chance of overlapping simultaneously appears remote. So many could have come and gone...reference, "Great Filter". On another note. Space voids always fascinated me. Why so empty? Possible advanced civilization harvesting stars via antimatter? Such things I ponder:(

Ok, lets look at atomic decay. I don't know, lets choose alpha decay. We don't know when the nucleus will next produce an emission and decay, though statistically over time we can predict how much emission it will produce over time. So we say the time of next emission is random but is that because of our limited knowledge and/or detection apparatus? @studiot If I wanted to choose 1 object at random from a set of objects, my definition of randomness is that nothing in the universe can predict which choice that would be. That is my layman's definition. Another query i have is how time plays a role in randomness. For example if an atomic nucleus decays at time t. If we "rewound" time and passed through time t again, would that nucleus decay at exactly the same time? If so, then it event was always deterministic, and not random, despite being seemingly random to us. A truly random emission would be time independent. Going back to my example of choosing 1 object at random.... then replaying that random choice process through time would produce either the same or a different result, but still unpredictable nevertherless. PS. I thought bell theorem's only disproves local hidden variables?

Yes this is a respectable argument. It is generally offered in terms of the current best estimate of the age of the universe (about 14 billion years) and how long it has taken for humans to develop to the point of asking this question (less than a million years). So many civilisations could have come and gone in that time.

At the risk of seeming smug, have a look at my post-count and status as a resident expert then think about why I asked the why it goes dark at night and why I linked it to a steady state universe/ You are answering the wrong question. Why does it go dark: ever?