Spacetime question

[sengsational]

I'm also thinking additional dimensions ... I think the math of string theory needs 11. I'm less mystified by heat conduction

[Fermion]

Well, if you go back to the generally excepted premise that in the big bang, everything started from essentially nothing, expanding into the giant universe we have today, then things like time travel and paradox really don't seem so far out there.

[Car-Guy]

I can wrap my mind around the big bang (and the concept of the big crunch) but the idea of a never ending universe "stretches" my limits.

[Qs Laptop]

This is my kind of discussion. I've got a lot of "what if" questions about time travel and paradoxes. Let's get started...

Let's say I'm a JFK assassination historian. I've written several academic papers, a couple of textbooks, and have been on lecture tours. A time traveler from the future goes back in time to 1963 and prevents the assassination of JFK. What happens to my life's work? What happens to my memory of JFK's death and aftermath? What about the millions (billions?) of other people with the same memories of JFK dying on November 22, 1963? What about all the history books, newspapers, news reels, etc. that recorded the assassination? >Poof< They're gone?

[Car-Guy]

^^^
While I'd love to know the truth about the JFK assassination, (among other things) I don't believe that time travel is possible now nor will it ever be. Other than we are always moving forward in time.. But that's me...

[mystang52]

Quote:

Originally Posted by Qs Laptop This is my kind of discussion. I've got a lot of "what if" questions about time travel and paradoxes. Let's get started... Let's say I'm a JFK assassination historian. I've written several academic papers, a couple of textbooks, and have been on lecture tours. A time traveler from the future goes back in time to 1963 and prevents the assassination of JFK. What happens to my life's work? What happens to my memory of JFK's death and aftermath? What about the millions (billions?) of other people with the same memories of JFK dying on November 22, 1963? What about all the history books, newspapers, news reels, etc. that recorded the assassination? >Poof< They're gone?

Hence the time travel paradox. My vote is if a time traveler could stop the assassination, then you'd have a different vocation since the assassination never happened. Doc Brown understood this:

https://www.youtube.com/watch?v=kWwcG1izaN0

[Qs Laptop]

Quote:

Originally Posted by mystang52 Hence the time travel paradox. My vote is if a time traveler could stop the assassination, then you'd have a different vocation since the assassination never happened. Doc Brown understood this:

Yes, that's a variation on the many worlds interpretation. Whenever there is a time travel event the universe creates an alternate timeline so as to avoid paradoxes.

[CaptTom]

Here's a cool way to look at it:

Imagine you're a photon. You get created in a star 100 million light years from Earth. You travel the 100 million light years in what, to an outside observer, would appear to be 100 million years. You land on a photo receptor in a telescope on Earth.

To you (the photon) you made the trip in an instant. You were created in the star the same moment you crashed into the photo receptor.

If you can wrap your mind around that, you can understand time dilation based on relative speed.

[corn18]

I keep thinking about the dark energy/matter issue we are trying to solve right now. What if we looked at it as dark gravity instead? We should be able to plot the impact of dark gravity and then come up with a formula to account for it. I need to find a theoretical physicist to help me with the math.

[Out-to-Lunch]

Quote:

Originally Posted by corn18 I keep thinking about the dark energy/matter issue we are trying to solve right now. What if we looked at it as dark gravity instead? We should be able to plot the impact of dark gravity and then come up with a formula to account for it. I need to find a theoretical physicist to help me with the math.

What is your rationale for distinguishing "energy/matter" from "gravity"? Matter gravitates. Energy gravitates. What are you seeking to disambiguate?

[corn18]

I think the dark gravity is coming from a fifth dimension we cannot observe. If we could accurately map the influence of dark gravity within the observable space time, we could develop an equation to account for the dark matter in the 5th dimension. Then find a way to observe it vs just tracking its influence.

Ultimately I postulate that the black hole, aka singularity, might be a connection point between space time and the 5th dimension. Would help explain a lot of whacky stuff that we currently try to explain away.

[ncbill]

Quote:

Originally Posted by corn18 I keep thinking about the dark energy/matter issue we are trying to solve right now. What if we looked at it as dark gravity instead? We should be able to plot the impact of dark gravity and then come up with a formula to account for it. I need to find a theoretical physicist to help me with the math.

IMHO, "dark matter" is simply something plugged in to make the math work.

AFAIK, there have been no experiments that actually prove its existence as matter.

It's probably because we know so little about how gravity works on a quantum scale...so "dark gravity" may well be a better way to interpret it.