What is the substance of space-time?
414515
spacetime is a medium inside which all matter and energy exist (i.e substances)   .  there is no substance to spacetime... substances exist IN spacetime.  spacetime is just a word. it exists but it is not for us visualize or touch or feel or do anything with.  you can call it whatever you want - the holder of things that are not spacetime themselves.  you dont need to see things for them to exist. they exist to give form to your understanding.   your mind can always form new questions by arranging letters into different configurations.  dont let it distract you.   it is like the question of what is outside spacetime ?   we can call it hyperspacetime.  it is defined as that which contains spacetime.  you cannot ask what is the substance of spacetime.  it is almost as meaningless a question as asking what does the sky taste like ?
366338
Since hydrogen atom is considered the basic of matter formation.\nThe space-time curvature is the same both inside and outside the hydrogen atom.
251659
Space is a 'fundamental' property of nature, which is a fancy way of saying that there is nothing more basic than Space as a medium of measurement.  Space is defined only as a relative porportion of distance when you compare at least two, very real, objects.  In this sense, space is not exactly nothing.\n\nAs a matter of fact, space as we now understand it, is filled completely with a very low level of energy called 'background radiation' which is most definitely something, even if it is very, very spread out.\n\nOne seemingly very odd property of Space is that it apparently is growing very fast, faster than the speed of light even, especially where it is the least 'filled up' with stuff.
192822
something to do with the curved space-time continuum
200022
Friedman Solved Einstein's field equation asuming the abscence of mass and he still came out with a description of energy in the Universe.\nWhat exists in the Univerves is Power in the Structure of Space. Relativity theory calls it space- time.Whether we call it Aether or Time -Space ,Its still the same Animal.\nThe can only be so and only if the Universe has restrains. your question was one of the most interesting ones.
453550
It is an incorrect concept that space is full of nothing.  There are dust particles and gas molecules in space.  The solar wind from our sun is always blowing particles into space.  There is also a galactic wind that is blowing particles out into space as well.\n\nSpace is as close as we can get to natural vacuum, or nothingness but it still has a density of one atom per cubic meter.
1061932
Matter is anything that occupies space. Matter is not alive so therefore cannot die.
723768
according to string theory \nthere r 4 dimensions\n3-space,1-time \n[11 of course which can't be perceived normally]\nthe dimension of space - time is variable in string theory , in the sense that we have to solve the string equations to determine it\nit's too difficult because of the great complexity of the theory\nif the ans comes out to be 4 then we'd have revealed one of the most abiding and mysterious facts since the dawn of civilization
92597
Okay. Everything that has mass has gravity. You and I have our own innate gravity. So does your pencil, your computer, the air you breathe. \n\nIf you think of space-time (see Einstein) as the surface of a huge trampoline on which everything sits, then mass sits on top of that trampoline. But if you put a bowling ball on a trampoline, it puckers the surface and smaller things are drawn towards it, and it is drawn towards the smaller thing, if only a little bit. Similarly, if you roll a marble around the bowling ball, it will circle many times before it finally crashes into the bowling ball. (That how orbiting works.)\n\nThis is simplified, of course, but it helps to understand the concepts. If you are interested in the subject, I would recommend reading Billions and Billions by Carl Sagan.\n\nGood Luck!
1133445
If Einstein is correct, then space/time is FLAT. The thing that distorts it is MASS, objects have Mass, in space time this is GRAVITATIONAL mass, so if you try to think of space as a rubber sheet, drop a weight, ( a planet, a star) onto this and it will distort, this distortion is the GRAVITATIONAL PULL of any Massive Object. Even things as small as atoms exert a gravitational pull.
256332
Time and space is distorted everywhere by everything. That is not a wild statement it is the truth. matter, any matter or energy, by its nature distorts space and time at a predictable magnitude.
514555
Space consists of nothing!\n\nSpace is mostly empty, with a spattering of matter in the form of galaxies, which are drifting further and further away from each other as time moves in the +ve direction.\n\nMatter and energy are mutually convertible.\n\nTime is the fourth dimension, and an important function of entropy or the running down of things.\n\nAs time moves in the +ve direction i.e. forward, entropy increases, things get run down and the energy dissipates over the expanding universe, as does matter, that means that as time goes by, the average density of the universe as we know it reduces, the matter-energy per unit area also reduces.\n\nAs time moves backward, entropy reduces, the space reduces to a point and matter and anti-matter coalesce to nothingness.\n\nst
35446
a black hole is an area of space-time with a gravitational field so intense that its escape velocity is equal to or exceeds the speed of light.
396914
Outer space is not nothing. Even without the presence of matter, it is teeming with quantum foam, particle-antiparticle pairs, space, and time. For all we know, spacetime may not exist outside our universe."\nAlso, the universe may not be bounded. The only way to "exit" may be to find a "fourth direction". Ie., think of a point in an unbounded plane. The only way for the point to exit its universe is to somehow find the "third direction".
415660
time is .....an imaginary dimension in space... \n time is .....gold ...\n time is .....precious...\n time is .....gooooood\n time ..................mmmmmmmm \n excuse me ..time to go have meselfe another drink hehehe
674188
well, spacetime does not seem to end, and nothing is "holding up" spacetime.\n\nthe universe is not infinite. the universe is finite yet has no edge and no center. it may be something like the two dimensional surface of a sphere. nothing inside or outside the sphere exists for the two dimensional surface.\n\nalso, i have something for you to think about. the radius of observable universe is about 46 billion lightyears, yet the universe is 13.7 billion years old.
621370
What is air?  It is a mixture of gases, trapped in the gravity of the Earth, that form an envelope around our planet.  It is a mixture of nitrogen (~78%), oxygen (~21%), and the rest small amounts of carbon dioxide, water vapor, argon, neon, carbon monoxide, and traces of other gases.\n\nIf there were no nuclei present, there would be no matter present, and that is the definition of a vacuum.