Hey folks,
I'm trying to obtain the melting points of several materials in a vacuum.
It's pretty straightforward to look up the melting point in 1 atm, but I'm having difficulty doing this in a vacuum.
One material in particular I'm looking at is Teflon.
If anyone can provide any...
Hey Folks,
I'm working on a new problem in a field I don't have much experience in at all and looking for some high level guidance to get me started.
For a certain material I want to calculate how much that material ablates in the presence of steadily increasing radiation flux from the...
Not contesting that at all. Merely pointing out that a little more info from that chap would be useful.
The Snow books sounds interesting. Having experienced both systems I've enjoyed seeing the flaws (and strengths) in both systems.
rich
Gotta remember, not everyone is from the UK and knows what you mean by A-level. It's a bit of a generic question as you are posting here in a physics forum so you could get polarized answers.
First figure out if your wonder is of the natural work, the metahphysical world etc. Physics might...
It's a big number yes, but it's possible the universe is that large. I recall reading in Lisa Randalls 'Warped Passages' yesterday that one model that she and a Greek physicist studied entertained the possibility that we are in a 3 (spatial) dimensional 'sink hole', and other non-causally...
Thanks for clarifying Mark. Thats crystal clear!
Really neat idea, to use the CMB as an inertial frame. Is this idea new to this thread...I'm guessing probably not.
Rich
Hey, sorry for the delay in getting back to you Marcus. I'm on vacation in Utah with my wife so I'm not in front of the computer as much as usual.
Going back to your thought experiment with two observers separated by 140 ly, you mentioned the observers could use a doppler radar to measure...
Thanks Marcus, and I'm glad you posted a response as I put a lot of value on what you say.
Let me entertain you for a few moments and tell you where I'm really coming from.
The energy density of the universe is (again, excuse my approximations)
\rho=10^{-47}GeV^4
and we know from GR...
We can measure the expansion of space via the galactic redshifting.
Please for now excuse my order of mag. estimate, but in mks units, Hubble's constant is roughly:
H=2\times 10^{-18} {\rm m/s/m}
If this exapansion was much larger. Say H'=2\times 10^{-10} {\rm m/s/m}
Could a...
Sure - in my analogy the constant rate of expansion is the idea that the elastic band doubles in size per unit time. This is a constant rate of expansion.
Also in my analogy, the rate of expansion increases with distance. This is exactly what is encoded in Hubbles constant.
H=77 (km/s)/Mpc...
Imagine an infinite length of elastic that doubles its length in 1 second, and you are located at L=0m.
If you look at the L=1m location after 1 second it will be located at L=2m. This implies v=1m/s.
If you look at the L=2m location after 1 second it will be located at L=4m. This implies...
Hey, great question. I had similar questions from friends (and similar problems answering them) when I was undergoing my undergrad training.
Some pointers to help you.
1. The balloon analogy, although cliched is really (IMO) the best visualization tool.
2. The expanding balloon plays the...