Aren't objects far away still moving away faster even with a constant expansion of space-time? Isn't the rate of expansion the speed at which two points at a defined distance move away from each other? If you take points at twice that distance, and per one unit of that distance the expansion...
Okay, that's very fascinating.
I will do exactly that. You have given me many impulses today, education on the types of reference frames, coordinate systems, especially comoving coordinates, Lorentz Transformations, four-vectors and invariant quantities.
I've learned, that most videos on the...
Alright, and time dilation and length contraction are not described for non-inertial references frames?
So in order to describe such a trip, you'd need to constantly construct global non-IRFs, and split them into other local IRFs, to get an answer?
But aren't they still embedded in the IRF? For example, the IRF of Earth includes all events that are inside its event horizon. You can say that objects that cross the event horizon are receding faster than c, due to the curvature of space. You can also say, that objects that cross the event...
Ah, that clears up a lot of things. I suppose, that accelerated frames are non-inertial frames. But that shows me, that I lack some understanding of those concepts, that seems essential to understanding the effects of time dilation and length contraction. Thank you, I will definitely read Sean...
Yes, I remember that, but I do not understand that concept, nor its implications. That was the one topic here, that I had the least understanding about. Do you have some keywords for me to read up about it?
I will now start with this, perhaps it's inside there...
Now, there's still the question of that, in relation to length contraction and time dilation.
Traveling at a speed of arbitrarily close to c, from the perspective of the travelers, they can pass billions of lightyears in a single second. Even though from the perspective of the Earth, that...
So that's very interesting: You yourself can get information about these distant galaxies of galaxy D. But it's a one-way trip. But still: Is that valid? Is it valid, that someone starting on Earth, by travelling, will be able to get information about galaxies beyond Earth's event horizon - even...
Thank you! That's it. I think, that was exactly the fallacy.
One thing I like to do is, stop the acceleration of the expansion rate of the universe. Because these statements still have to hold true, if the expansion rate remains constant.
Even if the expansion rate is constant, those distant...
Okay, I think I have to read more about coordinates, and I guess, the metric tensor, that I've heard a couple of times. If I understand how the coordinates are defined and manipulated by all these actions in the inertial reference frame of the traveler, I might understand the logical fallacy in...
I think, I understand this point now, thanks. But I don't yet understand the implication on my apparent paradox. With "distant galaxies", do you mean those galaxies that are still inside the Earth's horizon, or those that are outside the Earth's horizon?
I know. The Earth's inertial reference frame is not in any way more special than the traveler's inertial reference frame. That is, why it has to be impossible from the perspective of both of those inertial reference frames. I just find it much easier to see that, if I look at it from the...
The thing is, I know this. From the perspective of the inertial reference frame of the Earth, it is clear. I know about the cosmological event horizon, using light that has to travel from either the galaxies beyond the horizon, or from us to that point, it's clear to see how that is impossible...
Hello there!
I have a few questions that lead up to one significant problem that's been in my head for a long time. Many physics students will probably have had the same questions during their studies :biggrin:
The scenario is a spaceship, that travels away from Earth at 0.999...c 🚀. Due to...