What is the most rarest substance or material in outerspace?
488000
I doubt we know it yet.  We know of a limited number of stable atoms that can be found in our solar system, and a few that have been made by man, though many of the nam made ones are not stable.  Most of the heavier atoms were created during several Supernova explosions.  It is reasonable to suspect that a planet system that formed from the debris left from extremely massive Supernova, the energy from those explosions may have created some exotic element we are not even aware of yet.  Perhaps such element exist on Earth, but in such tiny amounts that we are not even aware they are there yet.
432870
"Scientists using NASA's Rossi X-ray Timing Explorer have estimated the depth of the crust on a neutron star, the densest object known in the universe. The crust, they say, is close to a mile deep and so tightly packed that a teaspoon of this material would weigh about 10 million tons on Earth."\n\nhttp://spaceflightnow.com/news/n0604/24starquake/
630601
There is some gas out there, but it's very sparse:\n\nhttp://hypertextbook.com/facts/2000/DaWeiCai.shtml\n\nThe interstellar medium is mainly made of lone hydrogen atoms. They do not even exist as pairs as they do on earth. I mentioned before that space is filled with hydrogen atoms. The actual density of hydrogen as it exist in interstellar space is on the average of about 1 atom per cubic centimeter. In the extremes, as low as 0.1 atom per cubic centimeter has been found in the space between the spiral arms and as high as 1000 atoms per cubic centimeter are known to exist near the galactic core.
149051
nitrogen, probably helium and hydrogen too.
697479
Mostly hydrogen. There is a little bit of helium and heavier elements in there as well.
1116812
The paper cited below says "It is the rarest element with an amount of only 550 g. in the entire earth's crust,"\n\nThat's a little more than 18 atoms.
928062
Well you can use spectroscopy to find out the composition of distant objects in space.  IE if a star emits light near (usually a slight red shift from distant objects) the emission lines of helium or mercury you could conclude that those elements are present.\n\nMike
496612
Some of it floats in space; much of it orbits Earth. You can find it on the surfaces of Venus and Mars and twenty tons of it is actually parked on the Moon! Some call it space trash, others refer to it as space junk or space debris. All three terms identify the same items -- man-made objects remaining in space though they no longer serve any useful purpose. Mankind¹s journey into space began in 1957 when the Soviet Union launched Sputnik, the first artificial satellite. Since that time more than 4,000 satellites have been launched into orbit. With so much traffic travelling into space, is it any wonder that a little trash has been left behind?
33705
Can be a sample of gas inside a glass cell in a physics lab at the University of Sussex or it can be Triton, a moon of the distant planet Neptune some 2,800 million miles away!
728938
the rarest of the platinum group (PGM) is iridium\nhttp://en.wikipedia.org/wiki/Iridium\nhttp://www.platinuminfo.net/pgm_ir.html\nhttp://www.platinuminfo.net/pgm.html\n\nplatinum\nhttp://www.blanchardonline.com/blanchard_products/bullion_platinum.php
514337
It has been estimated that 100,000 tonnes of extraterrestrial material reach the Earth's surface every year. It can be anything from fine dust to metallic masses weighing many tonnes.\nExtraterrestrial material that falls towards the Earth is classified by size. The majority of this material is in the form of tiny particles called micrometeorites. They fall continuously, and arrive unnoticed.
674610
Yes, Plasma is the 4th state of matter.\n\nIt *IS* found on Earth, and it is used in myriad applications.\n\nIt *IS* found in nature - [Plasma is] the most common form of matter, comprising more than 99% of the visible universe!!
819769
Read Angels and Demons. Although the antimatter making technique is totally impractical, it just might be possible to store the stuff in a hand-grenade sized container. Magnetic suspension has already been done, although it would make a large hand grenade with current technology.\nhttp://www.levitron.com/\n\nA truly perfect vacuum really is impossible, but a near-perfect vacuum could be done. Just as long as you eliminate all the gas molecules floating around, you should be safe enough. http://www.physlink.com/Education/AskExperts/ae290.cfm
705988
My gut agrees with you, but I wouldn't jump to any conclusions. A sobering (and excellent) read is Rare Earth by Ward and Brownlee. One is an astronomer, the other a geologist. They make a convincing case that sentient life elsewhere in the universe is probably quite rare. At a minimum, they make minced meat out of the Drake Equation. Still, with so many possibilities ...\n\nThe other thing to remember is that first and possibly second generation of post-Big Bang stars could never have supported planets with life of any kind. It took billions of years before stars produced sufficient quantities of heavy elements that are essential for life.\n\nand, all those stars and all those galaxies don't exist simultaneously. As we look farther out into space, we are more and more likely looking at objects that no longer exist.\n\nso, having said all that, we must consider this. a) sentient beings are probably quite rare - whether you accept Ward and Brownlee's extreme argument or not. b) that life could only have existed for, say, the last 8 or 9 billion years of the universe's existence. c) the distances to other stars in our galaxy are vast, but the distances *between* the galaxies are mind boggling vast (there's a reason that even in Star Trek, with it's fantasy warp drive, the story lines are all confined to our own galaxy).\n\nJust food for thought.
494685
You must not be a native English speaker. I think what you are asking is:\n\n1. Is outer space empty besides planets and stars...?\n2. How and when did the universe come into existence?\n\nNo; space is not empty it is filled with gas and dust(known as the "interstellar medium"). The density of the ISM varies widely between a few to hundreds of molecules per cubic meter. Even intergalactic space is not empty. It also contains traces of gas and dust. Latest estimates are 15 billion years for the age of the universe
494271
There was one that had 969. I was the last one to answer it. The question was, "What is the rarest substance on earth?"
1088527
Statistically it is very likely there is. There are many many billions of galaxies with billions of planets.\nThere are also some organisms found on meteors, but that’s not sure those came from the outer space.