But why would that be exactly? If you hold the end of the hose higher, the water will come out with less pressure (and at some height no water will come out anymore at all). If you lower the end, it will have more pressure. Under water, the pressure from the water in the pool will go up by the...
It just occurred to me that I could do a very simple experiment: timing the revolutions of the water meter. Turns out the flow rates are practically identical after all. I guess the hose being "sucked in" is due to the water flow dragging the surrounding water along with it, resulting in a flow...
I just noticed something interesting: if I hold the hose immediately above the water and then slowly lower it into the water, it quite abruptly moves down into the water, appearing to be "sucked in". Of course no actual "sucking" is taking place, but this rather seems to indicate that the...
It's from a standard water faucet, so I imagine the pressure at the faucet is determined either by the height of the water tower or the output of some huge pump supplying the neighbourhood. So I think we can assume the pressure to be constant at the faucet. Which means the pressure at the outlet...
Don't reply too quickly, I've seen a lot of answers on this question already (differing ones of course, what would you expect), at first sight it would seem to be really simple but there are quite a few complicating factors.
So the question is basically: what's the quickest way to fill up a...
Still semantics. We use the word "reality" to mean different things.
When I used the term, I really meant "subjective reality", i.e. reality as observed using that reference frame. Einstein said any observer can describe reality with his own coordinates and use the same physical laws to arrive...
Those are extremely interesting links. If I understood correctly, I was not crazy after all, but just neglected to take certain factors like gravity into account. In an empty universe (or a universe containing only massless objects), my description would be more or less valid, FRW with...
Thank you, your post makes a lot of sense.
So, if I understood correctly, my description would work if the universe consisted of massless galaxies that were being pushed apart by an infinite army of equally massless angels. However, because of gravity, dark energy and other effects, the...
OK, forget about the curved universe for a minute, let's first clear this up.
Lorentz contraction is indeed "just a change in coordinate convention", and so is time dilation. Still, they lead to very real and measurable results.
When I say "M31 moves into the future during this acceleration"...
What if I just define a coordinate system as follows:
- We (or rather a point close to us, stationary relative to the CMB) are the stationary origin.
- The time coordinate at any point of the universe, stationary relative to us (zero redshift) is defined by the Einstein synchronization theorem...
Hmmm, I must have completely misunderstood some part of SR then. Would you mind telling which part I'm getting wrong?
When I accelerate towards a distant object, it moves forward in time, right? You can even make distant galaxies move forward and backward in time by accelerating a little bit...
Thanks for the link, it's a very nice description of the different phases of expansion of the universe using the usual cosmological co-moving coordinates. (My model only considered simple expansion).
But my question is, what if we use coordinates based on the axioms of special relativity, in...
I am familiar with the balloon analogy. I read the article you linked to just to be sure.
It does say the universe "has no center", but that is not the case if you choose to describe it with special-relativistic (Minkowski?) coordinates around a chosen center. We may consider ourselves to be...
It's not so much a "theory" as a "way of describing things". I just want to know whether this is a correct description or not. Meanwhile I seem to have read some other descriptions that resemble mine somewhat (are my "special-relativistic coordinates" actually "Minkowski Space"?) but I may have...
Hi,
I always used to struggle with the concept of "space itself expanding" (didn't Einstein say that the aether did not exist?) until one day an idea struck me that seemed to explain it all, without any need for complicated math. After talking about it with others, I got some great feedback...