The discussion focuses on the relativistic effects observed by an observer moving towards a neutron star, specifically regarding time dilation and the Doppler effect. The observer uses a NIST-F2 atomic clock and notes that the neutron star's surface rotates at 0.6c. As the observer approaches at a dilation factor of 10, the Doppler factor is calculated to be approximately 20, leading to an increased frequency of the neutron star's pulses. The conversation emphasizes the importance of understanding the relativistic Doppler effect and the distinction between coordinate velocity and physical meaning in relativistic contexts.
PREREQUISITESAstronomers, physicists, and students of relativity who are interested in the effects of high-speed motion on time perception and frequency measurements in astrophysical contexts.
https://www.astronomy.com/science/weird-object-neutron-star-psr-j1748-2446/PeterDonis said:I don't see the point of switching scenarios if you haven't even gotten the original one right. The solution of both is the same in any case since we were only concerned with the equatorial plane of the rotating neutron star, which is the same as the rotating disk in your new scenario. So you've already been given the answer to your new scenario anyway.
It’s hard to visualize. In everyday life, the fastest-spinning thing we might see is the blade on a kitchen blender or a circular saw. But those never rotate more than a few hundred times a second. This star’s equator moves at one-quarter the speed of light. This rotation of 43,000 miles (70,000km) per second would be like Earth’s equator completing nearly two spins a second instead of one a day.
Neither. Do the math. I've already pointed you at it.King Solomon said:So now we start moving towards PSR J1748−2446ad at 0.995c, does the 70,000km remain the same or to the speed of light (minus a very small number).
Note that this is a speed in the pulsar's rest frame, and you are asking for a speed in the observer's frame. But this speed is not something the observer directly observes. They have to calculate it. Actually, two ways of making that calculation have been given in this thread. One of them just uses the direct velocity addition formula. The other starts with the Doppler factor, which is directly observed (the pulsar's frequency is 20 times faster) and then corrects for the change in light travel time due to the shortening distance between the pulsar and the observer. The two methods will both give the same answer if done correctly.King Solomon said:the 70,000km