Recent content by Lazzini

I was recently trying to explain to a grandchild the relative nature of velocity (the different paths of a coin dropped by a passenger on a train, as seen by the passenger on one hand and a trackside observer on the other), and the invalidity of the concept of absolute velocity. For some reason...

Thanks. A.T., for pointing me to that source. My physics background is pretty thin, and it would take me some time to get to grips with some of the terminology in it, but my initial impression was that it mainly describes experiments confirming the constancy of the velocity of light for all...

Having decided to try to understand the mathematics underlying Special Relativity, I have come up against an initial problem. I read that one of its postulates is that measurements of the speed of light, in any inertial frame of reference, return the same value, the value c. What I have so far...

Yes - I appreciate that, and just as a geostationary satellite experiences no stress from such a force, why would that not also be true of a body lying on the equator of the expanded Earth?

They are not massless, certainly, but surely they are weightless in the sense that they would register zero weight on bathroom scales in the same orbit? This, after all, is a problem faced by astronauts in orbit, and why they have to drink from squeeze-bottles, being unable to contain their...

Bodies in orbit around the Earth are, as I understand it, weightless. Suppose, then, that by some unimaginable process the Earth expanded to a radius equivalent to the orbital radius of a geostationary satellite, but retained the same mass. Does that imply that a body lying on the equator of the...

Hello Lurch. I'm back, later than expected. You say "When a body rotates", and this gets straight to the point of my confusion/questioning/ignorance - call it what you will. What is meant by "a body rotates"? I gave a previous example of someone tossing a ball on a train, and made the point -...

Thank you for the answer, Lurch. I shall be without access to the internet for the next week or so, and I'll respond to it (and any others that may turn up) when I return.

My question was intended as an opener to a problem that I have with the concept of absolute motion. As I understand it, and I understand physics only at a fairly elementary level, absolute motion doesn't exist. If I stand and watch a train go by while someone on it throws up a ball and catches...

Many thanks, marcus, for your replies, which I have only just seen. I have so far only skimmed through them, but they obviously deserve more than that.

I write as an intersted ignoramus. I have often read that studies of background radiation can take us back to, or give us information of, the earliest stages of the universe, when, as I understand everything was pretty close together. How is it that radiation from 14 billion years ago is...

Then does that mean that a person driving his Ferrari around the equator going east weighs less than one driving west? Does it mean that if I throw a stone westwards, standing on Earth's surface, and another to the east, one will reach ground before the other? I'm sorry to be asking such...

Presumably, then, I will eventually reach a height at which I can release a stone and it will neither fall nor rise. If I then throw a stone horizontally east, and another horizontaly west, one will have a velocity less than v, and the other will have a velocity greater than v, where v = omega *...

My tower is static with respect to the Earth, but shares all of Earth's motion.

If I build a tower - let's say, on the equator - and every so often, as the tower gets higher, I drop a stone from its top. Presumably, as I get fiurther away from the Earth's surface, each stone will accelerate towards ground at a lesser rate than one dropped when the tower was lower. How high...