Airbrush

"...something 12 light years away moves at the speed of light, etc." I think you mean that something over 13 Billion ly away is expanding away from us at over light speed. Merged post follows: Consecutive posts merged"The 12 lightyears distance would not be growing at the rate c, but would be growing at the rate of 30 million times the speed of light." You have got to be kidding right?

A few months ago I saw a wonderful short video clip, posted here somewhere by Martin, of a nobel winner explaining the structure of the universe to a design school. I think he said the very early universe, at about the Planck Time was smaller than a proton. Did he mean that only the visible universe would have been that small? Or do they no longer give a hint at the size of the singularity of the universe, very, very shortly after the Big Bang?

Certainly 10%C is not a modest speed. Thanks for calculating how long it takes at 1 G. Wow, great story about antigravity for masses moving near light speed. Does that also create a "tractor-beam" like effect that sweeps the path in front of the speeding spacecraft to remove objects that could destroy it? Even a grain of sand impacting at such speed would be disaster. However, I decline traveling thru space that fast. People are not meant for interstellar space travel. Just send probes that can sense everything around so well, the controllers at home will feel like they are THERE.

Oh well I didn't realize that maintaining one G acceleration would get you going so fast so quickly. How long would it take to reach a modest 10%C, which I heard is quite possible in the near future, at a constant one G acceleration? I don't know how to do that math.

Yes, if the starship gets near light speed it will become so massive that it will take more and more energy to maintain a constant one G acceleration. But on trips to the nearest stars, it would be possible to reach maybe a modest 10%C and then turn around and deccelerate the second half of the voyage there. It will take many years anyhow. I would never volunteer for the mission, because it will probably be a one-way trip and space is a dangerous place. They would have to make the trip there a lot of fun to interest anyone qualified. Maybe virtual reality games to keep the space travelors occupied. They will never see Earth again.

If a spaceship from Earth could accelerate at exactly one G on its' way to the nearest stars, that would give the crew exactly the gravity they need to stay healthy over the long term. You can get up to very high speed this way, before you know it. Then half way to the destination, the spacecraft turns around 180 degrees and begins deccelerating at exactly one G until they reach the destination. That will solve the problem of zero gravity during long starship voyages!

Good reference. Right, you are referring to the CMB radiation that is the furthest we can possibly detect, by any available means, because before 13.667 Billion years ago the unverse was still opaque. After that it cooled down and the dark age began that lasted until the first stars and galaxies formed about (what?) one Billion years later? I think I recall the dark age could have ended 200 Million years after the dark age began? I think it is not light at that distance but only a feeble glow near absolute zero. The first light came after the dark age when the first stars ignited. Those stars are about 30 Billion LY away now, and the cosmic background is 50% further at 45 Billion LY away. Merged post follows: Consecutive posts merged We see such distant objects because the light, or temperature reading, left that object or area of space in time for us to see it, and that happens to be limited by the age of the universe and the age of those first stars or areas of gas and dust in space.

We are not 13.7 Billion LY from the origin of the universe. The furthest we can "see" is the CMB (cosmic microwave background) radiation which is now about 45 Billion LY away, or about 50% further from us that the most distant visible galaxy, quasar, or gamma ray burst (GRB), which are now about 30 Billion LY away with a red-shift of about 8 (or 8.2 for that recent GRB). Sorry I don't understand the remainder of your question. Anyone else?

That's a good question Raul. Until Martin or someone else answers, I will take a feeble stab at it. Suppose that light we see now originated from a position 1.4 Billion LY away from us. We are only seeing it now because we never had the capability of seeing that far into space until now. Correct me if I am wrong, but I think if we could go back in time a few Billion years and set up our modern telescopes that can see the object, we would see it back then also, just not as red-shifted as we see it now.

"Where are they?" Assuming that ETI (extraterrestrial intelligence) is wide-spread thoughout our galaxy, maybe SOME of the UFOs are ETs. A civilization that is so advanced that they have found us and can travel here, then they are also so advanced that they know we cannot prove they are here if they are minimally careful to not be caught. They may have advanced sensory capabilities that can alert them when humans are near or they can cause cameras to only take blurred images, and hard evidence never falls into our hands. They could even mount effective dis-information campaigns to keep us chasing shadows, bogus UFOs, while the real ones remain undetectable. If they have been here for thousands of years it was easy for them to evade us up until recently. Now it is becoming more difficult and challenging for them to remain unverified by us.

I propose there is no paradox. The term "Fermi Paradox" was coined at a time scientists assumed there were a lot of ETs in our neighborhood. They all watched Star Trek! Perhaps there are so FEW that they are effectively isolated for a long time to come, maybe indefinitely.

Carl Sagan was instrumental in getting our position in space engraved in Voyager, so that ETs can find us someday. Recently I heard Michio Kaku suggest that may not be wise. Considering the possibility that ETs could adversely impact us, or eat us or destroy us and take Earth, maybe we should consider not leaking our TV programs to outer space?

The only way neutron star like density material could be found on Earth is to arrive here from outer space, and neutron stars cannot explode and throw pieces of themselves everywhere. Everything else crashes into a neutron star and is crushed to such density, but when neutron stars crash they merge with the energy shown by short gamma ray bursts.

Suppose a planet-sized object gets thrown at high speed away from a supernova. It would be slowed by gas and dust friction somewhat. It's path would be bent by nearby stars, but it would be going too fast to be captured in orbit around any star, unless it slowed down very much.

You are adding a couple of Billion years to the current estimates of the age of the universe. What does the age of the Earth have to do with it? It is not the oldest object, it is only the oldest VISIBLE object ever detected, and not thru visible light either, it is too red-shifted for that.

After the "Dark Ages" ended when the first stars ignited, about 400 Million years after the Big Bang (ATBB), there was a period of about 200 Million years until our recent GRB of 13 Billion years ATBB. Many generations of extremely massive stars could have been born and exploded in less than 10 Million years for each one. Each supernova would put pressure on local gas clouds causing new massive stars to rapidly form. Maybe the recent GRB was not first generation, but a decendant of many previous stars. If we see one GRB there could be thousands of others that were not alligned with Earth, so we would never see those. "Some studies estimate that the very first stars of the universe could have had a much larger mass, perhaps up to 1000 solar masses. Of course, the lifetime of these stars was exceedingly short, but they would have sowed the universe with heavy elements quite early."

This makes sense if the first stars formed about 400 Million years after the Big Bang. This would be among the first stars, a blue, hot supergiant that lived only tens or hundreds of Millions of years. It exploded 600 Million years after the Big Bang, then we saw it 13 Billion years later. Is there any way to know the size of a star that causes a GRB? Merged post follows: Consecutive posts merged I don't think I can ever get that thick-skinned balloon out of my head. Right after posting the above I turned on my radio and the first story on NPR was about this discovery! What a synchronicity.

http://www.astro.ucla.edu/~wright/CosmoCalc.html When I plug 8.2 into where z is supposed to go and click Flat, I get 30.016 Billion LY away currently.

Fascinating discovery! We were discussing most distant object (besides the CMB) which at that time was a gravitationally-lensed galaxy with a red shift of 7.6. But this beats that z = 8.2 means that thing is now over 30 Billion light years away. Could this GRB come from a galaxy, or a solitary Giant? It must have been a short-lived star. The only way we can see that far is by a GRB or gravity lens.

I agree. It is far more likely that a star collapse would be a little off center, and that little bit off-center is all it takes to whip the BH into a very high speed spin.

True that a BH rotating at near relativistic speeds, or I believe they stated a possible limit of 1,000 RPS? What percentage of BH are believed to be rotating at such high speed that they would bulge?

You are asking two questions. The first is essentially "Did the universe have freedom of choice about it's destiny, or was it predetermined at the moment of the Big Bang? I think it was predetermined, based on all pre-existing conditions. But maybe it is possible that during the course of the evolution of a universe, it could take different courses depending upon unforseeable events. Is anything possible? Sure, why not?

Even an object with smaller mass, such as our Moon, is massive enough to compact itself into a sphere. A black hole event horizon must be the most perfect sphere found in nature.

I may be wrong but I think there is a way to collect solar energy from solar cells to charge batteries that can send a pulse to the rockets of the gravity tractor. Kinetic impactors can be sent in numbers, so if one fails others can follow thru with the mission. There must be a way to blunt the impact so you don't break the asteroid into pieces, like a conventional or nuclear explosion just a second before impact, or the probe flattens out to splat against the asteroid. Or rather than a harpoon, a giant net is blasted around the front of the object and the probe swings around the other side attached by an elastic tether to pull on it. After the initial pull the probe will bounce back to the object which could be a problem, so the rebound impact could be avoided by cutting the probe loose after the pull. This would be tricky because the closing speed will be 10 to 20 miles per second. I'm trying to keep the technology as simple as possible. Of course, any of these methods should be tested in advance on non-threatening asteroids.

You make a good point Sherlock about the gravity tractor, which will be effective on lower mass objects. Its' task is so simple that it won't require much coaching from home. It just senses were the object is and adjusts it's distance automatically. It would have to fire its' rockets in small bursts, pointed at angles away from the object, so as not to push the object away by the propulsion system, and also rockets on the opposite side to stop it at the correct distance. It may require a few bursts per hour, or day, or week? over a period of years. What kind of propulsion system can handle that long-term schedule? For giant ones we need a more aggressive method or a combination of different methods. Merged post follows: Consecutive posts merged I just saw a program about this impact on History Channel and they said the mass that vaporized upon impact was about 300,000 tons.