B Are time loops possible?

I haven't been on here in a while and have forgotten a lot of my physics knowledge, which is annoying.

I just want to know, are time loops possible? Like the ones that appear in movies where a character relives a period of time. Is this allowed by the laws of physics? I know it's not really a physics question but this stuff is important to me, if someone with knowledge of physics is able to explain it. Thanks.
 

Mister T

Science Advisor
Gold Member
2,122
569
Do a google search for closed timelike curves.

Note that the worldline of a person is a timelike curve, so if it were close it's hard for me to make sense of the concept of time.
 

Ibix

Science Advisor
Insights Author
4,593
2,951
No.

Mathematically, we can describe "loops" in spacetime where you can pass the same event twice, but that doesn't operate like Groundhog Day. Every other time you went round the loop would be present every time. And all the potential for paradox that implies lead Novikov to propose his consistency principle, which boils down to "you can't change anything".

Furthermore, although we can describe such structures mathematically, the conditions necessary for them to actually exist are impossible as far as we know (negative energy densities and the like).
 
No.

Mathematically, we can describe "loops" in spacetime where you can pass the same event twice, but that doesn't operate like Groundhog Day. Every other time you went round the loop would be present every time. And all the potential for paradox that implies lead Novikov to propose his consistency principle, which boils down to "you can't change anything".

Furthermore, although we can describe such structures mathematically, the conditions necessary for them to actually exist are impossible as far as we know (negative energy densities and the like).
Interesting. So, what's really happening in the movie Groundhog Day? Is it anything of physics or just magic?
 

Ibix

Science Advisor
Insights Author
4,593
2,951
Interesting. So, what's really happening in the movie Groundhog Day? Is it anything of physics or just magic?
Magic. I have trouble imagining a physical model that could measure Bill Murray's character development and stop the loop when he had done enough to get the girl.
 
Fun movie, zero physics content.
Ok, I understand, but I know this sounds crazy, but my friend keeps insisting he lived a day multiple times like the movie Groundhog Day. Why would he say that?
 

Nugatory

Mentor
11,830
4,363
Your question was answered in post #3 above.

The thread is closed.
 

Want to reply to this thread?

"Are time loops possible?" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top