Recent content by Arkalius

Yeah this is an interesting result that many people find baffling. You can actually reach any location within the observable universe within a human lifetime using 1g constant acceleration halfway there and deceleration on the other half. Of course, a lot of time will have passed at your origin...

But there always exists a frame of reference where a particular coordinate time is the proper time that a clock could measure. Just because we can mathematically come up with quantities of time that wasn't measured by a particular clock doesn't mean it couldn't have been. Ultimately I think...

As far as I'm aware, there are no physical laws that expressly forbid the existence of negative mass-energy. But, we've never observed it, and it's properties would be pretty weird. We have no reason right now to suspect such a thing actually does or could exist, but maybe we'll be surprised in...

Let's try it with some numbers. You have a rod that's 5 units long and is stationary in our current frame of reference. So, we have our left end of the rod at 0 and the right end at 5. We'll pick 0 for our time coordinate to make things easy. So we have two events we'll transform, (0, 0) and (0...

Actually, in the presented case of rapid deceleration from very fast to 0 (relative to Earth) cause the image of AC to shrink so as to make it appear further away (in addition to blue shifting)? In a spacetime diagram, I notice the distance the light has traveled as the ship arrives at Earth in...

Keep in mind anything in the "past" in this new frame of reference is how things look in this frame of reference. If you've just left Earth at t=0 in this frame, then the spacetime coordinates of events in the past in this frame don't represent what your own past was because you didn't...

Wikipedia articles on established science topics are generally of good quality and good places to start if you want to know more about a science topic, as long as it isn't too deep into a particular discipline.

For GPS it is. The effects balance out in a circular orbit at an altitude 50% of the radius of the central body relative to someone on the surface (assuming the special relativity effect of the surface rotation is negligible, as it is for Earth). That's kind of not true... I mean it would be...

Well, if you and Earth flew away from some point in opposite directions, both at 0.25c, then from your perspective Earth would only be moving away from you at about 0.47c because velocities don't add linearly in special relativity. But that's the primary idea behind the principle of relativity...

Because acceleration can be measured within a given reference frame without having to consider anything in motion relative to your frame. An accelerometer on the ship will tell you if its accelerating or not. Furthermore, a third, inertial observer will note the accelerating ship change its...

Is that yours? I love that tool, been using it for awhile. It's a great help when I'm having trouble visualizing a scenario. If you have any interest in updating it and are receptive to requests or ideas, I could send a few your way.

Its important to remember that, relative to yourself, you are always stationary. So, for you, time always flows normally. Only other things can be moving relative to you, and when they do, you will observe their clocks ticking more slowly (negligibly until they reach significant fractions of the...

No. Assuming the train has Born rigidity (it maintains its proper length in each momentary rest frame during its acceleration), then the clock at the front of the train will run faster than the clock at the back during the acceleration, and when acceleration ends, both clocks will again run at...

Relative to the original frame, the first part of the ship is flying at 0.6c, and the second part is flying away at 0.88c. Using the formula ##\frac {0.6 + 0.6} {1 + 0.6*0.6} \approx 0.88##. So, the first ship sees Earth flying away in one direction at 0.6c and the second ship flying in the...

The basic description of time dilation is that moving clocks tick more slowly. But motion is relative, so no clock can be said to be absolutely moving. If I'm in a ship flying away from you at some speed, for you, my clock is ticking more slowly. But for me, you're the one who's moving, so your...