Recent content by Nisse

The OP appears to be asking what it is about an electromagnetic wave that allows it to propagate through empty space under its own steam. Is that not answerable?

Thank you both for your replies. I seem not to be making myself clear, for which I apologise. What I'm after is someone who knows the history of the terminology in this area, like a scientific historian. For example, if I asked when the plum pudding model of the atom was first proposed, people...

Firstly, civil twilight is often used legally to define "the hours of darkness" and, in the UK at least, lighting up time. That's "of minor interest", is it? Secondly, it may be of little interest to you, but you have absolutely no idea why I am looking for this information and what my interest...

There are standard definitions for civil twilight (geometric center of the Sun is 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon) and astronomical twilight(Sun is between 12° and 18° below the horizon). Surely there must be a record of when these standards...

Does anyone know when the twilights (civil, nautical, astronomical) were officially scientifically defined? My internet searches have come up with nothing. Any suggestions appreciated!

Asking what things look like from a photon's point of view is like asking what the world looks like to a Mexican wave as it travels through the crowd in a stadium.

Would it be fair to infer from this that Relativity is an incomplete theory?

Answer that and you'll win a Nobel Prize.

:frown:

Anyone?

Thank you to everyone for clearing that up for me (no pun intended). I only used STDs as an example because that's what first got me thinking about this. I'm not a medical person and the question has been bothering me for ages, and you're the first people to give me a sensible answer, so...

If the only way to contract a disease is by coming into contact with an already-infected person, how did the first person contract it?

We're told in school that the only way to catch an STD is to have intimate relations with someone who's already infected. If that really is the case, then how can these diseases have started in the first place? There must, logically, be some other way of contracting them.

Why bother asking why the sky is blue? Why bother asking why the sun rises every morning? Why bother asking why children inherit charcteristics from their parents? This "science can't answer 'why' questions" attitude seems very strange, and it's one I've noticed a lot on this board.

I chose a speed of 0.866c because that gives a length contraction of approx. 0.5 and a time dilation of approx. 2, just to make things easier. Here are the answers I got: 1. At the point of launch, traveling at 0.866c, the ship thinks the distance to A is 9.33 light minutes. 2. After 1...