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Grandpa -  

My question is entirely that of curiosity.  I was watching an episode of star trek the other day when I had a thought. My question is pertaining to Einstein's special theory of relativity in an absolute vacuum.  Consider the following: an object in space, in a complete vacuum without any boundaries or reference points.  Essentially an empty universe.  Let's say that the object was moving at a certain velocity, any velocity, doesn't matter what it is.  Velocity by definition is, distance traveled per unit time.  Now without any reference points distance cannot be calculated and conversely neither can velocity. So the thought came to me.  Is there such a thing as velocity in a complete vacuum?  Since velocity is relative it cannot be calculated in a vacuum, so it can therefore be assumed that velocity does not exist in a vacuum (my entire question in dependant on the preceding postulate).  Einstein's special theory of relativity states that matter cannot travel at or beyond the speed of light. So, my question is, can the special theory of relativity be applied to such a scenario, where velocity cannot be measured or even exist for that matter?

Thank you for you time in reading my email. I hope that I didn't burden you with an ignorant question, since I'm only 18 years old and am not exactly "well versed" in any of Einstein's theories cosmology, or whatever field of physics this question may be related to.

Jake Marar


Sent from AllExperts.com at 24 Aug 2000

Note: Grandpa is also a listed expert for physics at this site - Some examples come from there.


Jake -

Very good thinking process.  From thinking like this, many new things come.

There is much that travels in essentially a complete vacuum.  Most of matter is empty space.  The electrons associated with an atom or molecule travel within a vacuum.  Your question is not about vacuum, but about an empty universe, except for the one object under consideration.  Wherever you are considering it from, we may regard it to have a velocity with respect to that place.  If you must consider this object without existing yourself, you have an interesting mind experiment.  You are, of course, imagining the impossible, and this puts us in a place where we cannot know the answers.  The thought process is nonetheless a very good exercise.  As I do the mind experiment, I think:

"This object could not have a velocity.  This object would be the universe.  The universe is 'all that is,' and this imagined object is 'all that is.'  There could be no 'space' outside this object.  Now I will imagine that I am the object.  Where can I travel to?  There is no place to go.  On what road may I travel?  There is no road.  I am the universe; I cannot travel to non-existent places taking non-existent routes.  Now if I could wiggle my fingers, then I could consider their velocity relative to other parts of me, but now I am not a single object; now I am many objects, and that was not the question.  I can imagine that object splitting into two objects and separating at some velocity.  Then I would have linear velocity relative to the other object.  I still could not have rotational motion of one object about the other, though I could have rotation of either object about its own axis, because I could see that motion relative to the other object.  With three objects, I could have two of them rotating about one another and observe that from the third object." 

Space is a concept, which comes about due to the existence of "stuff," for the space to be between.  Space is not a thing; it is nothing, (no thing), except a mind-made concept.  The concept of "love" between two people is like this; it can exist only if the two people exist.  The problem that makes "space" seem more material to us, is that we imagine it to have "dimensions."  Those dimensions exist only because there is "stuff" to measure the distance between.  We have a psychological need to assign dimensions to concepts (that are not things) we want to understand.  A child tries to assign dimensions to love by holding his hands wide apart and declaring, "I love you this much."

Great scientists, including Albert Einstein, considered at great length the issue of space as either "nothing," or as an "ether."  Science is still not completely agreed on this issue.  Your question, using your phrase "complete vacuum," must be considering space as not consisting of an "ether," but consisting of exactly nothing.  If there were an "ether," then we could consider your object's travel "through" that ether at some "velocity" relative to that ether.   

We are used to thinking of "places" as things.  I could show you an empty table and ask you, "How much space is there between the two oranges?"  You would answer, "What two oranges?"  But if I put two oranges on the table about three feet apart and then asked the same question, you would answer, "About three feet."  Those same three feet were there without the oranges, but no "space" between oranges was recognized.  We can all see that "area" of the table, but that's because we may associate the "space" with all kinds of other things - the edges of the table, for example, ourselves or the carpet and other things in the room.

You're right that velocity only exists with reference to something.  We are traveling about a thousand miles per hour rotating with the Earth.  Many thousands of miles per hour around the Sun, and much faster than that as we travel with the Sun around the galaxy - and I suppose again even faster than that as we travel with our Milky Way around the universe.

If we buy the big bang concept of the beginning (or this particular beginning) - then we have at the outset, your proposition.  A point with nothing else around it.  That one point contains all the energy/mass that will become the entire universe.  Since it is our regard that nothing else exists outside that point, I've often wondered - "Is there space (empty) outside that point?"  I think, with the assumption of the big bang, that the answer has to be no.  There is not only nothing out there, but no space for anything either.  There is no "out there."  The one point is the only "place" that exists.

I am not a big proponent of the big bang - and the second law (of thermodynamics) bothers me.

I'm going to attach an essay I wrote years ago - for your possible interest.  I cannot answer your question with more than hints.  What you are doing is common in physics.  We call them "mind experiments."  I think I remember a word (which I cannot find in the dictionary) "gedankin."  I think it's the German word Einstein used, meaning roughly, "mind experiment."  There are many things we cannot test with "real" experiments, and so we use gedankins to consider these things.


- Grandpa

Essay: Ultimate Entropy

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