Is time travel possible?

pinback · Post by **pinback** » Fri Mar 19, 2021 7:29 am

Let's decide it once and for all!

If I missed an obvious answer, let me know and I'll add it.

Ice Cream Jonsey · Post by **Ice Cream Jonsey** » Fri Mar 19, 2021 9:27 am

It will be possible. We will figure out how. We haven't figure it out yet so that is why nobody from the future has been here. I AM CORRECT

AArdvark · Post by **AArdvark** » Fri Mar 19, 2021 1:00 pm

what a funny co inky dink, my newest story touches on this very topic. it's also interesting to see the amount of anti-timers we have here

Flack · Post by **Flack** » Fri Mar 19, 2021 2:27 pm

I was the only person who voted "it's already happened." Astronauts who have spent extended times in low gravity and high speeds have experienced time passing more slowly than we experience here on earth. Astronauts stationed aboard the ISS experience (admittedly minor) time dilation. These are small examples, but we know how it works; now all we need to do is crank up the examples. Speed and gravity both slow down time, so it's just a matter of how high we can raise those two variables in a human's life time (right now, 100 years on the ISS will get you about 1 second back in time).

AArdvark · Post by **AArdvark** » Fri Mar 19, 2021 2:34 pm

I want to be Marty McFly!

Jizaboz · Post by **Jizaboz** » Fri Mar 19, 2021 9:43 pm

Flack wrote: Fri Mar 19, 2021 2:27 pm I was the only person who voted "it's already happened." Astronauts who have spent extended times in low gravity and high speeds have experienced time passing more slowly than we experience here on earth. Astronauts stationed aboard the ISS experience (admittedly minor) time dilation. These are small examples, but we know how it works; now all we need to do is crank up the examples. Speed and gravity both slow down time, so it's just a matter of how high we can raise those two variables in a human's life time (right now, 100 years on the ISS will get you about 1 second back in time).

Right! Gravitational time dilation was proven with atomic clocks in the early 70s too. Time and space are relative, so when you talk about time traveling you are actually talking about traveling through "space-time".

AArdvark · Post by **AArdvark** » Sat Mar 20, 2021 2:56 am

I want to go back and eat, grandma

RealNC · Post by **RealNC** » Sat Mar 20, 2021 3:05 am

I feel like time doesn't exist, so no.

But even if it exists, I struggle to find a way to get past the most obvious philosophical hurdle: If you travel back in time, then how did you get there if the time where you performed the time travel hasn't arrived yet? If I travel from 10am to 9am, then me having traveled to 9am depends on me doing a time travel at 10am, but 10am hasn't happened yet so I didn't perform the time travel yet, so how can I even exist at 9am?

RealNC · Post by **RealNC** » Sat Mar 20, 2021 3:13 am

Jizaboz wrote: Fri Mar 19, 2021 9:43 pmRight! Gravitational time dilation was proven with atomic clocks in the early 70s too.

An interesting tidbit here (in case you didn't know already) is that time dilation is not caused by gravity. It's actually the reverse. The time differential is what causes gravity.

Ice Cream Jonsey · Post by **Ice Cream Jonsey** » Sat Mar 20, 2021 5:33 am

I thought gravity was simply one of the fundamental forces of the universe, and the matter that causes the Sun to interact with MakeMake or whatever is as of yet unobserved.

RealNC · Post by **RealNC** » Sat Mar 20, 2021 8:14 am

Ice Cream Jonsey wrote: Sat Mar 20, 2021 5:33 am I thought gravity was simply one of the fundamental forces of the universe, and the matter that causes the Sun to interact with MakeMake or whatever is as of yet unobserved.

The jury is still out on whether or not gravity is a fundamental force. And I'm not sure what "fundamental force" even means. The strong nuclear force for example is said to be fundamental, yet it has a cause (exchange of mesons.)

Is there an actual definition of "fundamental force?"

AArdvark · Post by **AArdvark** » Sat Mar 20, 2021 8:40 am

Like electromagnetism, that's fundamental

Tdarcos · Post by **Tdarcos** » Sat Mar 20, 2021 9:14 am

pinback wrote: Fri Mar 19, 2021 7:29 am Let's decide it once and for all!

If I missed an obvious answer, let me know and I'll add it.

"Forward Only"

Tdarcos · Post by **Tdarcos** » Sat Mar 20, 2021 9:18 am

AArdvark wrote: Fri Mar 19, 2021 1:00 pm what a funny co inky dink, my newest story touches on this very topic. it's also interesting to see the amount of anti-timers we have here

Yes, it was interesting. I read your time travel story two years before you wrote it.

AArdvark · Post by **AArdvark** » Sat Mar 20, 2021 9:38 am

Hurrrr! It's not a time travel story. And if you really did read it you would have been all passive-agressive and condescending like you were with the last one I wrote.

Ice Cream Jonsey · Post by **Ice Cream Jonsey** » Sat Mar 20, 2021 11:32 am

RealNC wrote: Sat Mar 20, 2021 8:14 am
Ice Cream Jonsey wrote: Sat Mar 20, 2021 5:33 am I thought gravity was simply one of the fundamental forces of the universe, and the matter that causes the Sun to interact with MakeMake or whatever is as of yet unobserved.
The jury is still out on whether or not gravity is a fundamental force. And I'm not sure what "fundamental force" even means. The strong nuclear force for example is said to be fundamental, yet it has a cause (exchange of mesons.)

Is there an actual definition of "fundamental force?"

I don't know either. But I do know there is a member of our crew who is an expert at finding definitions of things. Commander.......... You're on!!!

Tdarcos · Post by **Tdarcos** » Sat Mar 20, 2021 2:54 pm

Ice Cream Jonsey wrote: Sat Mar 20, 2021 5:33 am I thought gravity was simply one of the fundamental forces of the universe, and the matter that causes the Sun to interact with MakeMake or whatever is as of yet unobserved.
RealNC wrote: Sat Mar 20, 2021 8:14 am The jury is still out on whether or not gravity is a fundamental force. And I'm not sure what "fundamental force" even means. The strong nuclear force for example is said to be fundamental, yet it has a cause (exchange of mesons.)
Is there an actual definition of "fundamental force?"
I don't know either. But I do know there is a member of our crew who is an expert at finding definitions of things. Commander.......... You're on!!!

Consensus seems to agree there are four fundamental forces in the universe, in order of strength from strongest to weakest, are: Strong Nuclear, Electromagnetic, Weak Nuclear, and gravitational.

But this listing does not say that much, because the strength of the Strong Nuclear Force is 6x10E38 times stronger than the force of gravity. Even Encyclopedia Britannica agrees gravity is one of the four fundamental forces (non-fundamental means the force is composed of one or more of the four fundamental forces, the way every substance consists of molecules, and all molecules consist of one or more atomic substances).

Also, the names can be deceptive. While the strong force is trillions of trillions times more powerful than the force of gravity, its range is only about 10E-30 meters, or the width of a proton (one of the three components of an atom) whereas electromagnetism and gravity travel like light (which is based on electromagnetic force), forever, or until they are stopped by something.

Any object having mass emits gravity, directly proportional to its size. A marble will put out a lot weaker gravitational waves than a human body, which is essentially nothing compared to a planet, which is dwarfed by that emitted by a sun.

Ice Cream Jonsey · Post by **Ice Cream Jonsey** » Sat Mar 20, 2021 3:26 pm

Weak Nuclear really sounds like the Ringo of the forces there. I bet I could stick 'im.

Jizaboz · Post by **Jizaboz** » Sat Mar 20, 2021 8:37 pm

Tdarcos wrote: Sat Mar 20, 2021 9:14 am
pinback wrote: Fri Mar 19, 2021 7:29 am Let's decide it once and for all!

If I missed an obvious answer, let me know and I'll add it.
"Forward Only"

I was also going to comment on this as well. It is my belief after thinking about it and reading over the years is that yes, if in fact you had a reference frame (a Tardis to help visualize) that was capable of reaching speeds or manipulating time-space in order to travel back and forth through time (remember: time itself is relative. It is not a static thing related to distance) then you would only be able to view the past. What we call the physical past is a constant. It is in read-only mode.

However, you do have to travel to see it. Or do you? If your reference frame is anyone standing on earth that wants to see the future in outer space, simply look to distant stars in the night sky. The light which you see from many of those stars is many, many years. You are observing a star in the past, not the present. Again, time and space are relative to one another.

RealNC · Post by **RealNC** » Sun Mar 21, 2021 3:14 am

Jizaboz wrote: Sat Mar 20, 2021 8:37 pm However, you do have to travel to see it. Or do you? If your reference frame is anyone standing on earth that wants to see the future in outer space, simply look to distant stars in the night sky. The light which you see from many of those stars is many, many years. You are observing a star in the past, not the present. Again, time and space are relative to one another.

Another interesting tidbit:

The speed of light itself has actually never been measured. Only light's round trip time has. That is, the time it takes light to travel from A to B seems Immeasurable. But you can measure the time it takes light to travel from A to B and then back to A.

In Einstein's paper from 1905 when he proposed the theory of relativity, he mentioned this. He just assumes that the universe does not have any kind of directionality to it. However, even if there was a preferred direction and the speed of light was different when traveling from A to B than B to A, this has no effect whatsoever in observed physics. Everything works out exactly the same as long as the overall round trip time is the same. For example, if light travels at the speed of c/2 when going from A to B, and at infinite speed when going from B to A, nothing would change in known physics.

For example, when you look up at the starts, we just assume the light took a certain amount of time to reach us. But, even if what we see took zero time to reach us and we're getting a live view, if the speed at which Earth's light would need to reach those stars is half our assumed speed of light, then nothing changes.

There have been many proposals for experiments over the years for measuring the actual speed of light, but they all ended up being flawed in exactly the same way: what they really measure is the round trip time, just in less obvious ways. The true speed of light seems to be fundamentally immeasurable. Since Einstein stipulated that we should just forget about it and simply assume a fixed speed of light, that's what science has adopted.

A bit more information about it: https://phys.org/news/2021-01-there-no- ... asure.html