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Oldleggrunt t1_j64gezu wrote

i think the theoretical answer is YES. We also have physicists who firmly believe that time travel is not just possible, but is in fact now a matter of engineering. Keep a skeptical eye on the nay-sayers. Keep an optimistic eye on those who are trying. At 14, the future is yours. Take it and run!


MatsThyWit t1_j64lxd1 wrote

>i think the theoretical answer is YES. We also have physicists who firmly believe that time travel is not just possible, but is in fact now a matter of engineering. Keep a skeptical eye on the nay-sayers. Keep an optimistic eye on those who are trying. At 14, the future is yours. Take it and run!

I prefer to keep a skeptical eye on those who are trying as well as an optimistic eye on those who say nay.


a4mula t1_j64fgxu wrote

Sending information faster than light, would create a situation in which causality could be broken.

But these are very particular words that mean very particular things.

Is a signal information? Only if it passes novel information. Entanglement does not.


KingOfTNT10 OP t1_j64fsd2 wrote

Just a signal 1 bit signal


a4mula t1_j64g7d2 wrote

A 1 bit signal cannot posses information. You'd require a minimum of 2 bits. 1 bit is just a straight line, no breaks.

You need at least two states, on and off. 1 and 0. Line and Gap. So a minimum of two bits.

Entanglement doersn't pass new information. It only passes information that's embedded into the system at the time of interaction, even if it's unknown.

It's like a quarter. You cannot tell if you will flip heads or tails. But the moment you do, you instantly know what you didn't flip.

Nothing new is created, no new information.


total_alk t1_j64j384 wrote

1 bit is information. 1 bit, by definition, has two states. For example, the presence or absence of a photon can convey the answer to yes/no questions.


a4mula t1_j64k1pr wrote

1 bit is a single register of representation. You can have a million 0s, or a million 1s, but you cannot combine them in any way.

That's just a point, incapable of possessing information.

1-bit can never be information. Information is defined as the change of states. Not a state itself, and a 1-bit cannot change.


has no meaning.


has no meaning.

00 = 0

01 = 1

That's information.

edit: Hey dumdums.... I get this is space and not philosophy of computation. But it's not a hard concept to grasp.

If you've got a single light switch. I can represent it as on or off. But by itself, it cannot represent information. On and Off is not information, it's data.

It's only a combination of ons and offs that qualify. And the moment you introduce something like iteration. Flipping the light switch on and off over time?

You introduce a new register. A new bit. It's no longer 1d data. Now it's 1d data over time. This is two dimensional. 1 bit of data, 1 bit of iteration. 2d. 2 bit, minimum for information passing.


rdwulfe t1_j64l9yl wrote

A bit, by definition, is the possibility of a 0 or a 1.

Now, the problemHehe is you're sending a 0 or 1 with no context.


a4mula t1_j64lxmx wrote

A bit, is a storage space for a representation. By the nature of dimensions, a single dimension, be it of physical space or data can never represent change. It's an isolated spot. In order to represent change (information) you have to have a second dimension. An x, and a y.

2-bits is the minimum state for information.


KamikazeArchon t1_j64ltj9 wrote

Information is not "defined as the change of states." That's simply not true.

Maybe that's what you understand it as, but it's not a standard scientific definition in any field.


a4mula t1_j64mklw wrote

Information theory? I don't know about you, but that's the one I'd go to if I were looking first.


KamikazeArchon t1_j64ms9j wrote

That is not how it's defined in information theory.


a4mula t1_j64n039 wrote

>In information theory, the information content, self-information, surprisal, or Shannon information is a basic quantity derived from the probability of a particular event occurring from a random variable.

That's the definition. Want me to show you where the change is a required part of it?


KamikazeArchon t1_j64n8jo wrote

Change is not a requirement of that. Are you under the impression that "event" means "change"?


a4mula t1_j64noee wrote

>Derive - base a concept on a logical extension or modification of (another concept).

In order to derive you must alter the original data. It must change. That is the fundamental aspect of information.

It can change. If it cannot change, it's just data. Not information.


VulpesIncendium t1_j64hp66 wrote

With our current understanding of physics, such a thing is literally impossible.

But as a thought experiment, let's say some alien civilization has figured out how to send a signal faster than the speed of light. What would that look like to us? I think it would appear as though a signal blinked into existence, with no discernable origin point. Depending on just how much faster they could send the signal, and how far it travelled, it would probably look like it appeared ahead of an observable planet, like where the planet will eventually end up many years in the future.


Deep_BrownEyes t1_j64oldi wrote

Wouldn't it appear to travel backwards? The signal appears out of nowhere as it is received and slowly traces backwards to its origin


AirierWitch1066 t1_j66buzv wrote

This supposes that the signal must be “sent.”

Orson Scott Card in Ender’s Game came up with an Ansible which worked via two entangled particles - you could spin one and the other would spin the same no matter how far away it was.

This probably isn’t actually possible, but I think in our hypotheticals it’s fair to consider a form of communication in which the information doesn’t travel faster than light, because it doesn’t travel at all, it simply exists at both ends.


VulpesIncendium t1_j66s76g wrote

I actually thought about mentioning this, since it's the same exact sci-fi technology they use in the Mass Effect game series to explain instantaneous communication across the galaxy. It's an interesting idea, but I just dismissed it as impossible sci-fi magic. But, who knows? Maybe one day it could be the basis for some real world technology.


psilosimian t1_j64j367 wrote

If those aliens sent a light speed signal, they would have to wait 4 years to watch us recieve it in the "past". If the signal were faster than light, let's say instantaneous, they would simply see us recieve the message immediately rather than having to wait the 4 year travel time. So I think the answer is no, the message would not travel back in time

Edit: I forgot about the travel time for light from earth to the telescope. The instant message would be viewed arriving in the aliens 4 year old archived footage but still never traveled back in time. It does break causality though


Plus_Cartoonist_3060 t1_j64k5il wrote

So far as we know, nothing can travel faster than the speed of light. However, a relatively new discovery/concept is called "Quantum Entanglement" in which two or more particles can become connected seemingly regardless of the space between them. In such a case, information could theoretically be transmitted instantaneously


KamikazeArchon t1_j64m4g9 wrote

Quantum entanglement does not allow for the transmission of information, according to all experiments we've run.


Plus_Cartoonist_3060 t1_j64mmjq wrote

If you have two atoms in quantum entanglement, and you change the spin of one atom, the other atom will change it's spin to be opposite. Isn't this the essence of transmitting information?


KamikazeArchon t1_j64n3gf wrote

It would be if it were true. It's not. That's not what entanglement means. If you change the spin of one, nothing will happen to the other. Changing spin breaks entanglement.


Plus_Cartoonist_3060 t1_j653ciz wrote

Interesting I always thought it was true! Do you mind providing a source?


p4ort t1_j658mu0 wrote

I don’t think you understand QE.

Say I entangle 2 particles and send particle 2 an arbitrarily far distance away. Particle 1 is the one I measure, and I find out it’s spinning clockwise. I now instantly know that particle 2 is spinning counterclockwise. Until the person with particle 2 measures it they do not know it is spinning counterclockwise.

No information is transmitted, the interesting thing is being able to measure a particle that is not local to me.

If you were able to measure the particle AND alert your companion what the spin was instantly then you would have FTL information transfer.


p4ort t1_j658315 wrote

No, information can not theoretically be transmitted instantaneously with quantum entanglement.


PandaEven3982 t1_j64k9r5 wrote

Yup. That's why it's also called the speed of information . When you look at the night sky, you are looking into a mosaic of past events that happened anywhere from 4 years ago to millions of years ago. Or at least looking at extrasolar stuff. Even sunlight here on earth is 8 minutes old. :-)


shawnwasim t1_j64knym wrote

You cant exceed the speed of light. Even if you have near zero mass, the amount of energy required to get close to the speed of light goes to infinite.


Murky_Examination144 t1_j64l1ta wrote

Anything, be it a physical ship or an electromagnetic signal - radio, arriving faster than light would break causality, as it would be travelling back in time.

Someone that explains this quite well is Prof David Kipping. Watch this video:

It took me a couple of tries to understand the setup of the charts, but after that, it is obvious there would be a problem. Give it a try. You won't be dissapointed.


space-ModTeam t1_j64mqk5 wrote

Hello u/KingOfTNT10, your submission "Sending a signal faster than light is time travel?" has been removed from r/space because:

  • Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.


boombotser t1_j64n2q1 wrote

You would remove it right when I open the thread


Galapgosian t1_j64ou5l wrote

Information transfer is bound by the speed of light. There is no theoretical possibility of going faster. Your experience of a light beam is going to be the same regardless of it’s speed. You will see it when it strikes your eye.

Time travel can only occur relativistically. The faster a mass moves, the slower time elapses for it.


dantodd t1_j64pyzi wrote

What an awesome and insightful question.

Yes, and no.

Let's make a few assumptions. First. Let's assume that both planets are aware of each other and have tech's assumed at each other. Second let's assume that the communication is instantaneous to take out the math issues. Third, only one planet can transmit the messages but the other can recurve them. Finally, assume I'm a random stranger on the Internet and I don't have a PhD in physics.

Both planets are looking at each other and they are seeing photons that bounced off the other planet 4 years in the past. (i.e. they are 4 light years apart) If one planet transmits this instantaneous signal the planet that received the signal will see it as coming from the future because it was transmitted 4 years before the images they are recording on their telescope. So, if they could see the transmitter being built they might see it still under construction for four years after they get the first transmissions.

To the planet transmitting the signal they would get feedback via light speed communications or actual light images in only 4 years rather than the anticipated 8 with communications limited by the speed of light. I think this would look like time dilation rather than time travel to the planet transmitting.

It is not dissimilar to shooting something at long range. If you are the shooter you hear the gun fire and then see the target get hit. If you are standing near the target you see the target react to getting hit long before you hear the gun shot. So, which order you perceive things happening depends on where you are. Of course we are used to the difference in asked between sounds and light so it seems natural but it takes a bit more to shift ourc thinking you you're question


Kay_0zz t1_j64q31q wrote

If you change a q-bit its pair also changes instantly no matter where it is in the universe. How does it know? That's information being exchanged faster than the speed of light. Particle physics and quantum mechanics have rules we don't know or understand yet.


wjbc t1_j64fakw wrote

There's no such thing. The speed of light is an absolute limit. There's no such thing as time travel, either.

That said, even ordinary light from another star is from the past. If it's 4 light years away it's for years in the past. If it's 100 million light years away it's 100 million years in the past. (Actually, since the universe is expanding, the light we see now is from when the star was 100 million light years away, 100 million years ago -- but at present it would be much farther than that.)

What's not possible is for the light to arrive here any faster than the speed of light, so that we see what's happening now, or more recently than the number of light years between us and that star when the light starts traveling towards us.


LincolnsVengeance t1_j64ggp9 wrote

That's completely not true. There are hypotheses about traveling faster than light and sending signals instantaneously that conform with the laws of physics as we know them, we just don't have the technology to confirm these hypotheses and most likely won't for a very long time. You're also wrong about time travel. Technically speaking, you're time traveling at relativistic speeds due to the effects of time dilation. If you're traveling fast enough, you're time traveling simply because you're experiencing time exponentially slower than people on earth. If you're going to talk in absolutes, I'd encourage you to at least read about what you're going to be talking about first.


Varsect t1_j64j95p wrote

>That's completely not true.

It's not true nor false. You can't conclude one until practical tests have been made.


LincolnsVengeance t1_j64k68m wrote

The statement "there is no such thing" is unequivocally false whether or not you agree with what I said in the rest of my comment. There is such a thing, look up the Alcubierre Drive hypothesis.


Varsect t1_j64kxi2 wrote

What about the Alcubierre Warp Drive?


LincolnsVengeance t1_j64lnju wrote

>It's not true nor false. You can't conclude one until practical tests have been made.

The hypothesis exists therefore there are scientists who at least believe in the possibility that FTL travel is possible. It's also not scientifically impossible, the laws of physics don't forbid it as such. The reason I brought up the Alcubierre Warp Drive is because the person I was commenting to originally made an absolute statement that was wrong. There is a hypothesis therefore it is a thing that exists even if it's not practical theory yet.


Varsect t1_j64njgc wrote

Ok, you've won

>The hypothesis exists therefore there are scientists who at least believe in the possibility that FTL travel is possible

I've always wondered how FTL would help outside of the local group with an expanding universe.


LincolnsVengeance t1_j64o6u3 wrote

You could in theory travel to other stars in our star cluster and explore or even live there if you could find a habitable enough planet. That's so far in the future that it really has no practical application other than as an aspiration and inspiration for those doing the work required to eventual get there. There is the other problem of even at twice the speed of light it would still take 2 years to reach Alpha Centauri.


Varsect t1_j64ox1f wrote

I mean like, that's localized to the Milky Way and the local group. For extra local group travel, it'd basically be impossible.


LincolnsVengeance t1_j64pe2o wrote

I didn't realize you were referring to that kind of scale. I can't imagine it would mean much seeing as the outer edges of the universe are already expanding away from us faster than light


Varsect t1_j64qg42 wrote

Yeah. The fantasy of leaving the local group is basically not realistic and by the time we do learn to do so most of the observable universe will be concentrated almost solely on the edges of the Virgo cluster around Laniakea.


srandrews t1_j64j42g wrote

Your point on time and relativity is a good one. But that should not be called time travel. People colloquially use "time travel" to denote an event that breaks causality. You are probably thinking about nonlocality and entanglement. Those do not transfer information or material in a superluminal manner.

I appreciate your distinction between hypothesis and theory. For at least the sake of our current societal ills, a hypothesis should not be taken as a truth until it becomes a scientifically accepted theory.


LincolnsVengeance t1_j64l20d wrote

I was attempting to keep it less technical because of the nature of the OP's question. I was never arguing that causality breaking time travel is possible. I was just refuting the other commentors absolute statements that there is no such thing. Maybe I had to be creative with my meaning when I say time travel but it's nothing my physics professor wouldn't have done.


KingOfTNT10 OP t1_j64fm6i wrote

Not saying that it exist or will ever exist, but if there was a type of signal that could do it, what would happen?


wjbc t1_j64hegv wrote

Well, since it's an imaginary signal, you can invent what happens.