Can a Single Particle Move in an Empty Universe?

In summary, if there were only a single elementary particle in the entire universe, it would have constant movement which is undetectable and indistinguishable from being stationary.
  • #1
CaptDude
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Question: If there were only a single elementary particle in the entire universe - could it move, and if so, how would its movement be measured?
 
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  • #2
CaptDude said:
Question: If there were only a single elementary particle in the entire universe - could it move, and if so, how would its movement be measured?
The only reference frame to measure any movement would be its own, in which by definition it cannot move.

Garth
 
  • #3
CaptDude said:
Question: If there were only a single elementary particle in the entire universe - could it move, and if so, how would its movement be measured?
Well, any constant motion would be undetectable. But if it were possible for the particle to accelerate, that could (probably) be detected, because if this particle had electric charge, acceleration would cause it to radiate. A change in the acceleration would cause it to emit gravitational waves.

That said, if there wasn't some other particle around, there'd be nothing to cause it to accelerate (or change its acceleration), so it'd just have constant motion which is undetectable and indistinguishable from being stationary.
 
  • #4
CaptDude said:
If there were only a single elementary particle in the entire universe - could it move, and if so, how would its movement be measured?

If there is only a single elementary particle in the universe, what measuring device would be used to measure its movement?
 
  • #5
lol it takes physics to do physics!
 
  • #6
PeterDonis said:
If there is only a single elementary particle in the universe, what measuring device would be used to measure its movement?

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Well, since my post says it is a "thought experiment" I'm sure you could think of something....
 
  • #7
CaptDude said:
since my post says it is a "thought experiment" I'm sure you could think of something

No, I can't. That's why I asked the question. It's your thought experiment. If you can't think of something either, what does that tell you?
 
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  • #8
PeterDonis said:
If there is only a single elementary particle in the universe, what measuring device would be used to measure its movement?

CaptDude said:
New
Well, since my post says it is a "thought experiment" I'm sure you could think of something....

While thought experiments do allow for highly impractical parameters ("...imagine I flew my starship to the centre of the sun"), those parameters have to be ones that aren't directly relevant to the thought experiment.

In your scenario, the concept of measuring movement is directly relevant: movement is not an absolute - it must be relative to something (Einstein taught us that) - requiring at least two particles.

So, I guess you have answered your own question.
 
  • #9
DaveC426913 said:
While thought experiments do allow for highly impractical parameters ("...imagine I flew my starship to the centre of the sun"), those parameters have to be ones that aren't directly relevant to the thought experiment.

In your scenario, the concept of measuring movement is directly relevant: movement is not an absolute - it must be relative to something (Einstein taught us that) - requiring at least two particles.

So, I guess you have answered your own question.

Thank you for your CONSTRUCTIVE comment. I see your point and thank you for taking the time to write something that is informative.
 
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FAQ: Can a Single Particle Move in an Empty Universe?

1. What is a thought experiment on movement?

A thought experiment on movement is a hypothetical scenario that is created in the mind to explore the concept of movement and its effects. It is a mental exercise that allows scientists to think through complex ideas and theories without the need for physical experimentation.

2. How are thought experiments on movement useful in scientific research?

Thought experiments on movement are useful in scientific research because they allow scientists to test and refine their theories without the need for costly and time-consuming physical experiments. They also help scientists to think critically and creatively about different scenarios and potential outcomes.

3. Can thought experiments on movement lead to new scientific discoveries?

Yes, thought experiments on movement can lead to new scientific discoveries. By exploring hypothetical scenarios and considering all possible outcomes, scientists may discover new insights and connections that they may not have thought of otherwise.

4. Are thought experiments on movement considered valid forms of scientific evidence?

Thought experiments on movement are not considered valid forms of scientific evidence on their own. However, they can be used to support or refute existing theories and hypotheses. Physical experimentation is still necessary to validate the findings of thought experiments.

5. How do thought experiments on movement differ from real-life experiments?

Thought experiments on movement differ from real-life experiments in that they are conducted entirely in the mind and do not require any physical materials or equipment. They also allow for the exploration of extreme or impossible scenarios that may not be possible to test in real life.

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