Solutions to the Twin Paradox are STILL Wrong

Are "solutions" to the twin paradox STILL leaving you confused and skeptical? In our follow-up to "Why Solutions to the Twin Paradox are Wrong" we dive deeper into popular YouTube videos, examining spacetime diagrams, the Lorentz Transformations, and other tools that are often incorrectly used to resolve the paradox.

Feel free to leave any questions or thoughts in the comments below!

Full Twin Paradox Playlist:

Link to "Why Solutions to the Twin Paradox are Wrong":

Link to "Can You Feel Force?"

[גיאאברהם-וג]

You misunderstood relativity, SR relies on:
1. all *INERTIAL* frames of reference are equally valid
2. speed of light is constant
Einstein never claimed that the same laws apply for an accelerating body.
But I can see the confusion; intuitively, why you can say that acceleration is absolute is because for example, if you take a mass and give it speed it'll keep that same speed when you stop acting on it. if you accelerate a mass and stop acting on it it'll stop accelerating according to the lab.
in the video you can't switch to the other diagram because it's accelerating. I don't understand if you think that physics states that acceleration is not absolute, or you're aware that you made it up

[simonwatson]

Acceleration is not relative. You can't simply pretend you're being accelerated because you can see someone else strapped to a rocket. Once you get that wrong, all your subsequent conclusions are wrong.

[DanielNeedles]

When you accelerate in a car or plane away from a location and you accelerate back toward the original location at the turnaround point and finally deaccelerate at the end of the trip, in each case, you feel a constant pressure against your chest. Conversely, the person on the ground waiting for you to make the journey feels none of these 3 cases. That is the difference and can be directly measured and experienced. That constant pressure demonstrates you are curving your worldline into the space dimension in the direction of travel and back again to the original direction.

You can try to work around this by having the car on an aircraft carrier and the aircraft carrier accelerating in the opposite direction in exact sync with the car to keep the car stationary. If you ran this experiment, the person in the car besides at the gear change points, would feel no constant pressure against their chest.

You could create a similar situation but make it so the motion of the aircraft carrier relative to the whole is not observable, but in that case, what is relative is the immediate change of velocity relative to your immediate past self. This is different from other forms of velocity and acceleration. In fact, right now sitting or laying there, you are rotating with the Earth at 1, 000 miles per hour, around the sun 18.5 miles per second, around the galaxy 140 miles per second, toward the great attractor 370 miles per second but you feel none of it. You feel stationary in space and are moving only in time. That actually hints at the answer and where the weirdness comes from. We only move in time, not space.

If we did, our thoughts would be able to separate from our minds but that doesn't happen. Special relativity happens when you accelerate in a direction in 4D space and that direction becomes part of your timeline (aka worldline.) But the size of the observer doesn't change, so as your experience incorporates a dimension in space as your timeline it necessarily extends your timeline out when observed from your previous self trajectory through 4D space. However, the experience inside the "rectangle" is always a "square" and instead if you could look at your past self you would see the same relative changes - shrinkage in the direction of travel and elongation of time (i.e. slowing of the clock for those who didn't accelerate but were in your same frame of reference.)

A second part of we only move in time is that though we experience time as a fluid thing, space is static. The subjective experience of time is defined as a spot in space with low entropy in the beginning and higher entropy at the end. Because it is experienced, effectively that section of space is "played" to create the subjective experience such that we cannot observe this section of space. This is what makes time and space complex to one another (as math is a description, not an explanation and the use of complex numbers allows us to describe how subjective experience hides our path through 4D space which we experience as time.) This is not a new idea and dates back to Zeno's arrow with the Greeks or the concept of Maya in Hindu texts.

Finally, you can replace the aircraft carrier accelerating with a gravity well and use that, as what is happening with geosynchronous orbit, where the astronauts are in free fall but end up orbiting. Again, the feeling of free fall is consistent with the space curvature, combating the curved orbit, resulting in a constant state of free fall.

What is interesting in every example is how acceleration is felt. Acceleration, changing velocity in time, is felt in each case as a velocity, a constant pressure resisting your acceleration. This hints at the fact we are really a velocity in spacetime, traveling in time. If not we should feel an ever-increasing pressure against our chest when accelerating relative to our past self.

If you walk thought the math from this perspective, it does add up. We move only in time which means acceleration causes us to change space travel into our timeline as at a constant velocity we always feel at rest. And since we move in time but space is static, the use of "i" is needed to compensate for our experience as "I" There is a lot more to this though as it also points to subjective experience relating to the structure of 4D space, rather than being substance based, a philosophy we inherited from the Greeks.

[peterdamen]

Clearly the narrator has no clue what he's talking about. Acceleration is the only solution to the problem. And acceleration is definitely NOT relative. Quite the opposite, whereas velocity is (mostly) relative, acceleration is not. It's actually quite simple as you understand it (which the narrator obviously doesn't).

[WeAreShowboat]

9:16 You’re ignoring the fact that Albert’s coordinate clocks (imagine them distributed through space and riding with him) would no longer be synchronized in his new frame after he turned around.

This seems like an easy way to distinguish instrumentally who changed their inertial reference frame and coordinate system. Alice’s clocks would always be synchronized so her calculation is more correct. With Albert he’d have to decide how to resynchronize his clocks which is basically cheating. If you change your clocks mid race, you don’t get to declare yourself the winner.

[Jim-tvtk]

This is so very wrong. I was subscribed but there are too many nonsense videos

[AntiCitizenX]

I'm very sorry, my friend, but this is objectively wrong. Twin B does NOT have the right to say that others are accelerating while he remains still. That is 100% false.

[deinauge]

When you talk about paradoxes in relativity, you should use relativity. And in relativity there are so called inertial frames. Lorentz transformation give you the possibility to transform coordinates between inertial frames.
If you just drop "inertial", you are not working in relativity! And that's where all your confusion comes from.

[drewolbrich]

It's true that special relativity and the twin paradox are hard to explain well, and I appreciate that, but this video is so fundamentally wrong I feel like I'm being trolled.

The big error is what when the two symmetrical spacetime diagrams are shown for the Earth and space twin, the Earth twin's spacetime diagram is not showing a single inertial frame. It's showing two inertial frames, one for the space twin's outbound journey, and one for the space twin's inbound journey, and it's mixing these together into a single spacetime diagram as if they were a single inertial frame.

You can't do that. That's not a spacetime diagram. It's nonsense. It's a misunderstanding of what a spacetime diagram represents.

At 8:45 in the video, the The Earth twin spacetime diagram on the left side of the symmetry diagram is hot garbage.

I recommend reading about the version of the twin paradox that has 3 twins and involves no acceleration at all. It's a much more satisfying explanation, and does a lot to address the confusion around acceleration that this video gets caught up on.

[chadjones]

Unfortunately this is fundamentally flawed and therefore wrong.

The twin paradox only exists if there is no violation of the equivalence principle.

Or in other words there's no difference in saying person A is still and B is traveling at a constant speed or person B is still and A is traveling at a constant speed. If that's the case, then equivalence principle holds and there is a paradox.

Unfortunately the creator of the video made a fundamental mistake in thinking the equivalence principle could apply to acceleration.

Unfortunately it's just not true. Think of it this way. Imagine A and B are both in separate rocket ships, but only B fires rockets to accelerate.

Now imagine these astronauts are hovering just above the self destruct button. Only one of them is going to blow up and it's the one who rams into the button. Since A didn't fire rockets and the ship and the astronaut are moving at the same speed, that'll never happen. Conversely, since B fired rockets, the ship accelerates but the astronaut does not initially because he's not in contact with anything until he hits the button and blows up the ship.

To say that both accelerate makes no sense because there would have to be some "magic" force to cause astronaut A to hit his button and there just isn't one.

[РайанКупер-эо]

Acceleration CAN NOT be relative. This would break the conservation of linear momentum law. Every action has equal and opposite reaction. Relative acceleration would break that. This paradox only proves that physics wouldn't work without conservation of linear momentum.

[F_viper_pilot]

I’m so glad I’m not the only one who watched most of these other videos and said “wait, what??…..that doesn’t answer the question.”

[lukasrafajpps]

There is too much unnecessary confusion about this paradox. Emmy and Albert don't have to agree to anything but all inertial observers in the universe would agree on who was the one accelerating and this is what breaks the symmetry of the twin paradox.

[musicalday]

One factor which seems to be not explained here is that there IS a NON RELATIVE difference between the twins. The twin who ventues forth in the spaceship feels inertial forces that the stay at home twin does not experience. Imagine we had a science fiction "ultra wave" radio whereby the twins could comminicate instantaneouly. The traveller blasts off and phones in saying "man this rocket is powerful! I'm feeling huge inertial force from my acceleration, I'll try not to black out okay?'" In my rocket ship frame of reference of course I'm seeing you and the earth accelerating away from me at the same huge rate. How are you handling the G forces are you well zipped into your G suit?." The stay at home replies "what G forces, the only G force I feel is gravity keeping me in my armchair." Ergo ... the two twins are NOT symmetrical with regards to acceleration forces. You can dicriminitate who is the traveller and who is the observer by comparing their experiences of acceleration. Have a think about it.

[vecter]

This entire video is wrong. Acceleration IS the answer, and here's why:

While velocity is relative, in SR, acceleration is ABSOLUTE. That means, in any reference frame, you can determine whether or not your frame is inertial WITHOUT REFERRING TO OTHER REFERENCE FRAMES. How? You simply build an accelerometer, or do something even simpler like letting go of an apple you're holding and seeing if it moves. Setting aside gravity (we're assuming a flat Minkowski spacetime), the apple you let go should not move if you let it go. If it does, then you are in a non-inertial frame. In other words, if there exist fictitious forces in your frame, then your frame is accelerating and thus non-inertial.

If, after conducting this experiment, you see that you are in a non-inertial frame, then you must use *DIFFERENT* equations in SR to account for this fact. If you do, then you will get the correct answer. So in our example, the twin on the Earth (again, IGNORING GRAVITY), will detect that they are in an inertial frame. The spaceship twin WILL detect that they are accelerating, so if he adjusts for this by using the correct equations of SR to account for this, then when he wraps back around to Earth, his math will match the Earth twin's math.

I'm shocked and disappointed. I thought that this channel was good, but now I'm unsubscribing since it confidently posts FALSE information as if it were true.

[brunocardin]

It's incorrect. Acceleration is in fact absolute.. it's equivalent to gravity, meaning that, just like the metric tensor, it's local.

[dannylad]

You seem to be of this mindset that we cant measure and compare 2 different accelerations because for some reason we can'tfell forces. But like, how does that explain the fact Nasa or whoever would have to use a certain grade of steel with a particular yield strength for the rocket ship for instance, so the stiffness of each member would have to be designed so that it can withstand the forces resulting from the acceleration it is subject to? Like we measure forces resulting from accelerations all the time from the stress vs strain relationships of materials such as steel.

[habouzhaboux]

No acceleration is not coordinative. Proper acceleration is a scalar all observers agree on.

[MrBendybruce]

I don't see how you can claim acceleration to be relative, when it exerts a fictitious force on the observer. So how can the twin at an inertial rest frame claim they are accelerating when they feel no force? I would really appreciate an answer to this question, because without it I simply cannot accept your assertion as it simply makes no sense to me.

[jameslam]

Acceleration of frames is relative and only mathematical, but objects move from one inertial frame to another inertial frame of different velocity require force and this is absolute.

When the twins start at the same place with zero relative velocity, they can both move away from each other and turn around, and then meet up somewhere not necessarily at the same point. They can compare with each other's acceleration and deduce who is older. The difference in the amount of acceleration is still the key to resolve the paradox. Right?