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interstellaryeller
2008-Oct-26, 09:01 AM
Do we live in a 3 dimentional universe or a 4 dimenional universe ? The reason I ask this question is because everything changes, children grow to be adults, machinery gets old and breaks down, Even every atom in the universe will decay back to nothing. The universe is truly infinite and mankind will never explore it all. Because it is infinite. What i am trying to say is could time be considered a 4th dimention?

formulaterp
2008-Oct-26, 10:00 AM
How do the number of dimensions play into that? Perhaps you can clarify your question?

cosmocrazy
2008-Oct-26, 10:08 AM
Do we live in a 3 dimensional universe or a 4 dimensional? The reason I ask this question is because everything changes, children grow to be adults, machinery gets old and breaks down, Even every atom in the universe will decay back to nothing. The universe is truly infinite and mankind will never explore it all. Because it is infinite.

Hi, and welcome to the forum.

To answer your first question simply the current consensus is that we exist in 3 dimensions of space and 1 of time. But Einstein postulated that time and space are entwined to form space-time. Other than this there are many theories of extra dimensions but as yet not proven to exist.

Your last statement is not entirely correct, in that there is no hard evidence to prove that the universe is finite or infinite. Entropy is not evidence to suggest either way, but shows that in this current cycle/time-line of our universe matter seems to eventually revert back to its simplest form(that we are aware of) given enough time. But we also have to consider what happens to energy and matter falling into a black hole or "big-bang singularity" when discussing such subjects.
There are plenty of folks on this forum who will happily go into detail about what you ask if you require it. :)

mugaliens
2008-Oct-26, 10:10 AM
There are three spatial dimensions, and one temporal dimension. This satisfies Newtonian space. When you start delving into symmetry, things get *somewhat* more complicated.

astromark
2008-Oct-26, 10:19 AM
'Interstellaryeller' It might not actually be infinite.
Atoms do not decay to nothing.
They were never nothing.., so the 'back' is wrong to.
But I do agree with the point that nothing stays the same.
Dimensional; Three spacial being length breadth and depth. With time added to give a reference to a timing of events. Four dimensions.

interstellaryeller
2008-Oct-26, 10:31 AM
I was watching a documentory on the subject of space/time they talked about theories and formulas. And they also mentioned it would take all the energy this world could produce for 1 year to launch a 16 pound bowling ball at the speed of light, out in space. I was awled by this. these programs start my imagination boiling. Thanks for the answer and have a great day.:):):)

cosmocrazy
2008-Oct-26, 10:41 AM
I was watching a documentary's on the subject of space/time they talked about theories and formulas. And they also mentioned it would take all the energy this world could produce for 1 year to launch a 16 pound bowling ball at the speed of light, out in space. I was awled by this. these programs start my imagination boiling. Thanks for the answer and have a great day.:):):)

Yes these documentary's have a way to get your imagination going! But again this is not quite correct. It is theoretically impossible to accelerate any mass "to the speed of light" only very close to it, 99.999..% of C, and so on. :)

interstellaryeller
2008-Oct-26, 10:44 AM
'Interstellaryeller' It might not actually be infinite.
Atoms do not decay to nothing.
They were never nothing.., so the 'back' is wrong to.
But I do agree with the point that nothing stays the same.
Dimensional; Three spacial being length breadth and depth. With time added to give a reference to a timing of events. Four dimensions. Well then how far do they decay? Because the half life of uranium is lead. And if time is eternal then in theory shouldnt every atom eventually decay? thanks for your time.

thorkil2
2008-Oct-26, 12:48 PM
Decay of Uranium is not decay in the sense that you are thinking. Certain isotopes of Uranium are unstable and will decay (with lead as the final product), but that is not decay to nothing, and your statement that the "half-life is lead" is incorrect. Some Uranium isotopes will decay to eventually become lead, but not all. Some are stable. In any event, the decay is simply a change in form. There are theories which postulate Neutron decay, but the time frames are so huge as to be meaningless. We would have worse things to worry about long before that happens.

thorkil2
2008-Oct-26, 12:52 PM
Sorry, meant to clarify half life....The half life of an unstable isotope is the time it takes for half of it to decay to either an intermediate or stable form. So the half life of Uranium 238 would be the time it takes for half of the Uranium atoms to decay to another form; the time is the same for half of the remainder, then half of that remainder, etc.

mugaliens
2008-Oct-26, 02:48 PM
I was watching a documentory on the subject of space/time they talked about theories and formulas. And they also mentioned it would take all the energy this world could produce for 1 year to launch a 16 pound bowling ball at the speed of light, out in space. I was awled by this. these programs start my imagination boiling. Thanks for the answer and have a great day.:):):)

All the energy in the entire universe, even if added to all the mass of the universe, if converted to energy, would not be sufficient to cause an electron, much less a bowling ball, to reach the speed of light.

mugaliens
2008-Oct-26, 02:55 PM
Well then how far do they decay? Because the half life of uranium is lead. And if time is eternal then in theory shouldnt every atom eventually decay? thanks for your time.

The half-life of U-238 is 4.468x109 years (about 4.5 Billion years). Half-lifes are measured in terms of time, not the elements into which an element radioactively decays. U-238 decays via alpha radiation, through the 18-member uranium natural decay series, into lead-206. U-235 decays through a 15-member series into lead-207.