Is the Unisverse really expanding?

[ving (David)]

Originally posted by slice of heaven
The answer is still no. The tiny rocket part was a joke. lol
I might do a search after and try and find a full detailed description of the thrust equation to explain it.
I used to play with model rockets when I was a kid and it is easy to understand.
The size of the exhaust nozzle is critical.
Never had a toy jet though. But i think the adjustable exhaust nozzle on the jets is for the afterburners. They are opened for the afterburners and closed for the normal operation. The afterburners are only a series of injecters squirting fuel directly into the exhaust ,therefore needing a larger exhaust nozzle.

cool! science experiment time!!

you need:

• 1 pingpong ball

• 1 straw

• 1 3" diameter pvc tube or other similar tube

place the ball on a flat surface and blow thru the straw at it, taking note at velocity achieved at lung presure exerted. now grab the 3" tube and repeat useing the exact same pressure.
the force coming out of the 3" tube is substantially less than the straw and the ball moves less.

Dr Ving says lesson over.
interestign topic peoples!

[ballaratdragons (Ken)]

David,

Astronauts don't carry straws, ping-pong balls etc. LOL

Be funny to see an Astronaut wind down the window of his shuttle a blow through a straw to make a course correction.

[slice of heaven]

To add to that Ving
Get 50 people blowing through the same straw and 50 people blowing through the 3" tube.
Now which will move the ball more?

[ving (David)]

50 people on one straw! now your just being silly!
now if the straw had 50 entry points so 50 people could use it.... I'd still say the straw would win. of course you cant get 50 peeps on the one hole (even on a 3" pipe!).

hey ken... I think you are on to something there!

[slice of heaven]

Nightshift

Laws 2 and 3 apply to the rockets thrust.

What other tangible 'yardstick' can we use for pressure thats relative to us living on Earth.We do use the pressure of space to compare our atmospheric pressure. And the pressure in space is zero.

Its all theory. Until you can actually show something factually it is theory.Even the end of our Universe has to have a boundary.Whether its finite or infinite. Its a debate that will continue for all time ,until it is actually proven.
All theories relating to the size of the universe have had to have other unproven theories added to make the original theories plausable. So theres a lot of assumptions being made, not proven.
To reverse the situation; Is there a centre of the Earth?
I could say no!
Travel to the centre of the Earth and put a dot there. Then halve that dot, then halve that dot, then halve that dot, then halve that dot and you can do that infinitely.So no there is no centre of the Earth.
But there is a centre of the Earth. The term infinity itself suggests boundaries. Aristotle explained this better than I can.
Whichever train of thought you wish to follow will ultimately bring you to the conclusion that the answer cant be proved or disproved.
In a truly infinite universe youll have an infinite number of everything, including dimensions. So in other dimensions you'd possibly have other universes. So if there's other universes there would have to be a boundary between this universe and the others so therefore the universe isnt infinite.
So an infinite universe is a contradiction to itself.
Just because we cant see the edge of the universe doesnt mean there isnt one.
By including space in your description of the universe youve also placed the constraint of time as well. You cant have one without the other.

[slice of heaven]

Sorry Ving, I'm always silly on Monday mornings.

Heres a simple diagram to explain rocket thrust

http://www.grc.nasa.gov/WWW/K-12/airplane/rockth.html

Exhaust nozzle size matters

[ballaratdragons (Ken)]

In the link above the 'Nozzle Simulator' helps.

[slice of heaven]

I didnt even look at the page BD. I just seen the pic and equation and posted it.
Run the Ving straw theory it through. lol

[ving (David)]

hmm... i did. my it seems that the "throat size" is a case of the bigger the better too.... gah! stoopid jet thing!