# The Naked Scientists Forum

### Author Topic: Is spacetime real?  (Read 1794 times)

#### PmbPhy

• Neilep Level Member
• Posts: 2760
• Thanked: 38 times
##### Re: Is spacetime real?
« Reply #25 on: 27/09/2016 02:21:36 »
Quote from: mxplxxx
Given we can't seem to go forwards or backwards in Spacetime, how likely is it that Spacetime is real?
I'll try to explain this in another way, i.e. the way that I should have explained it from the very start. First of all it's apparent to me that the problem that you have understanding this is that you don't appear to really know what spacetime is. To resolve that misunderstanding please see how I explained spacetime in the webpage that I created for this purpose.
See: http://www.newenglandphysics.org/physics_world/sr/spacetime.htm

So basically spacetime itself is a mathematical object which was created/defined in order to describe nature. Basically it's a manifold, which is a fancy way of saying that its a set. Its just a set with certain properties. The set is in a one-to-one correspondence  with the world. Each element of the spacetime manifold is defined as an event which, simply put, is a place and time. E.g. A particular point in Boston at 11:31pm. That's an event. So to claim that spacetime isn't real one first has to define the term "real" and then determine of the things that we use to describe nature, such as numbers, are "real." Is the number one "real"? I say yes. Is the complex number i =sqrt(-1) "real"? I say yes here as well.

But seriously. Who cares if it falls under the category of the things we choose to label as "real"?  Not most physicists, that's something I'm sure of. So do yourself a favor and stop worrying about things that don't matter such as how to categorize things. Your time is better spent learning relativity from start to finish. Do that and you'll learn the answers to all of your questions.

Unfortunately there's a very unhelpful trend in this forum which consists of worrying and questioning thjngs like special relativity by people who haven't even read a good textbook on the subject from cover to cover. I find that to be a very sad state of affairs. :(

#### mxplxxx

• Full Member
• Posts: 91
• Thanked: 2 times
##### Re: Is spacetime real?
« Reply #26 on: 27/09/2016 14:42:56 »
It would be interesting to compare the workings of Spacetime to those of an analogue computer and quantum theory to that of a digital computer. There seem to be lots of similarities. This thought also has possible relevance for wave-particle duality. In a funny way, time does not exist in Spacetime seeing as all possible states of the universe exist in Spacetime (not sure of this) and moving from one state to another gives the impression of time. On the other hand time seems to be basic to quantum theory as in particle frequency, radioactive decay etc..

Can Spacetime described a galaxy as an abstraction of smaller structure like solar systems?  Pretty sure quantum theory can (e.g. a molecule is an abstraction of elementary particles).

Finally, the possible reason bosons move at the speed of light is that their purpose doesn't need state. They are force carriers.  At the speed of light time, and therefore state, doesn't exist. State implies time and this is likely why fermions exist in time. Fermions handle complex events that happen over time.
« Last Edit: 27/09/2016 23:57:41 by mxplxxx »

#### jeffreyH

• Global Moderator
• Neilep Level Member
• Posts: 3765
• Thanked: 46 times
• The graviton sucks
##### Re: Is spacetime real?
« Reply #27 on: 28/09/2016 08:51:28 »
Just to clear up any misunderstanding. Spatial dimensions are a subset of the set of dimensions. An array, or matrix, can have any number of dimensions labelled by indexes. If this is not understood then misconceptions arise.

#### puppypower

• Hero Member
• Posts: 535
• Thanked: 40 times
##### Re: Is spacetime real?
« Reply #28 on: 28/09/2016 11:50:38 »
One way to address space-time, is to stop time, so time is not longer a variable in our observation. With time stopped we can still observe mass, charge, distance and position. We can also observe motion bur, which gives the impression of motion, with time stopped.

Motion blur is the only affect, of the above, that shows an interconnection between time and distance; time stopped. Motion blur is where two references are the not the same; shutter speed and motion speed.

The Heisenberg Uncertainty Principle could be correlated to motion blur, since an electron; action speed, is in a different reference than the lab; shutter speed, due to relativistic speed of the electron and the non-relativistic lab. Space-time appears in motion blur, blurring the distinction between  momentum (mass, distance and time) and position. This is also what motion blue does.

In the motion blur image below, we can tell the position of the running back in the center, but not his momentum. On the other hand, we can tell there is momentum in the defenders in the foreground, but there is uncertainty in their position. However, we can't determine both position and momentum of everyone.

#### geordief

• Jr. Member
• Posts: 28
• Thanked: 1 times
##### Re: Is spacetime real?
« Reply #29 on: 28/09/2016 12:04:24 »
Just to clear up any misunderstanding. Spatial dimensions are a subset of the set of dimensions. An array, or matrix, can have any number of dimensions labelled by indexes. If this is not understood then misconceptions arise.
I have noted that  the  s^2 =x^2 +y" +z^2 -ct^2 is the only definition of an "interval" in the real world  which is the same when calculated from any  frame of reference.

Can it be  shown(mathematically proven)  that there cannot be others? (I am not talking of polar co-ordinates which  presumably boil down to the  same thing )

If one uses more dimensions  as I understand  is done (String Theory?)  does this interval still hold up to this invariant scrutiny?

Is it possible  hypothetically to replace the {+,+,+,-] functions with any other kind of relationship so long as this  interval is maintained (I have nothing in mind ;)   )

#### chiralSPO

• Global Moderator
• Neilep Level Member
• Posts: 1830
• Thanked: 137 times
##### Re: Is spacetime real?
« Reply #30 on: 28/09/2016 12:48:03 »
I have cleaned this thread up, and moved the clutter regarding whether or not time is a dimension to a new thread in the subforum "That CAN'T be true" members may feel free to carry on that discussion there, or continue to discuss the original question here.

#### The Naked Scientists Forum

##### Re: Is spacetime real?
« Reply #30 on: 28/09/2016 12:48:03 »