Ask Science
Ask a science question, get a science answer.
Community Rules
Rule 1: Be respectful and inclusive.
Treat others with respect, and maintain a positive atmosphere.
Rule 2: No harassment, hate speech, bigotry, or trolling.
Avoid any form of harassment, hate speech, bigotry, or offensive behavior.
Rule 3: Engage in constructive discussions.
Contribute to meaningful and constructive discussions that enhance scientific understanding.
Rule 4: No AI-generated answers.
Strictly prohibit the use of AI-generated answers. Providing answers generated by AI systems is not allowed and may result in a ban.
Rule 5: Follow guidelines and moderators' instructions.
Adhere to community guidelines and comply with instructions given by moderators.
Rule 6: Use appropriate language and tone.
Communicate using suitable language and maintain a professional and respectful tone.
Rule 7: Report violations.
Report any violations of the community rules to the moderators for appropriate action.
Rule 8: Foster a continuous learning environment.
Encourage a continuous learning environment where members can share knowledge and engage in scientific discussions.
Rule 9: Source required for answers.
Provide credible sources for answers. Failure to include a source may result in the removal of the answer to ensure information reliability.
By adhering to these rules, we create a welcoming and informative environment where science-related questions receive accurate and credible answers. Thank you for your cooperation in making the Ask Science community a valuable resource for scientific knowledge.
We retain the discretion to modify the rules as we deem necessary.
view the rest of the comments
Physicist here. Many common misconceptions in the comments.
If the other person travels at some speed (just) below the speed of light, the signal they send will be Doppler shifted/time dilated according to their relative velocity.
Thanks for clearing that up
I know there are a lot of impossibilities baked into how this scenario is set up. But hypothetically, if you could have a spaceship travelling at the speed of light, and hypothetically if they could communicate with someone who is stationary (ignoring Doppler effect etc), what would it be like to talk to them? Would the time dilation make it seem like the person travelling at lightspeed is speaking very slow?
This hypothetical is of the type "immovable object versus unstoppable force." The question becomes: which of the axioms of relativity do you want to discard? Yet, once you do, you are leaving the realm of physics and entering the realm of sci-fi, in which anything may be possible.
If you want to maintain any link to our current understanding of physics, there are no hypotheticals, no ifs or buts. It's simply not possible to have a set of laws of physics consistent with relativity as we understand it, wherein massive objects can travel at the speed of light in vacuum.
Okay well let’s just stipulate that the object is travelling close to enough to the speed of light for there to be time dilation of some sort. Or maybe the object is stationary but near a black hole or something so there is time dilation from the gravity
There is always time dilation between any two frames of references moving at nonzero speed with respect to each other. It's generally negligible for everyday velocities, but it's still there. You can find the degree of time dilation (and length contraction for that matter) in special relativity (i.e. ignoring gravity) by computing the gamma/Lorentz factor. For example, for 90% of the speed of light, the Lorentz factor is about 2.29.
In that case, it depends on how strong the gravitational effect is. The mathematics is a bit more complicated though. I would recommend to stick to special relativity if you're learning about relativity as an interested layman.