There was some really interesting work by the galaxy zoo team on this. They asked people to classify disk galaxies as being rotating counter clockwise (s like) or clockwise (z like). They actually found that there are more s like galaxies. To uncover this, they took the sample and flipped the...
As far as I know, this is a problem of simulteneity. Fred see's the events as simultaneous because he is within the inertial frame of the trani where the events take place.
However for Nancy, in a different inertial frame will see the train differently. I would say that she wouldn't see the two...
I used the equation for the Hubble Parameter as a function of redshift, then changed this over to be a function of scale factor instead.
\Omega_{total 0} = 1
I don't understand the first bitof the question I'm sorry.
I'm uncertain as to how that determines which of the two remaining...
Hello.
I have been working through some questions and answers to do with cosmology. One of them asks you to consider a model where:
\Omega_{MO}=3
\Omega_{\Lambda O}=0.01
\Omega_{RO}=0
and asks you to show mathematically that the model re-collapses.
Following through the math, I get three...
Shameless bump, could really use some help with this.
I have tried a bit more myself. Using:
P=\frac{\rho k T}{\mu} = \frac{1.3807 /times 10^{-23} \times 3 \times 10^6 \times 2 \times 10^7 \times 3}{4}=6.213 \times 10^{-10}
Using values given above, and taking mu as being 4/3 for pure...
Homework Statement
Have to calculate the Electron-Degeneracy Pressure as a fraction of the total pressure in a white dwarf. Given Density and Temperature.Homework Equations
(\frac{1}{5m_{e}}) (\frac{3h^3}{8 \pi})^{2/3} (\frac{\rho}{\mu_{e}M_{H}})^{5/3}
The Attempt at a Solution
I have...
Homework Statement
If a cosmic ray proton has 15J of energy how long, according to the proton's proper time would it take to travel from the galaxy M31 to our Galaxy, a distance that we mesure as 2.5x106 light-years?
Homework Equations
K.E = m_{o}c^2 (\gamma -1)The Attempt at a Solution
I...
So far I have:
z(t)=\frac{a(t_{o})}{a(t)}-1 = \frac{1}{a(t)}-1
Since a(to)=1 by definition,
Thus:
\frac{\delta z}{\delta t_{o}} = 0
\frac{\delta z}{\delta t}=-a(t)^-2
\frac{dt}{dt_{o}}
And now I am at another brick wall.
That terminology has confused me somewhat. The \dot{a} is the scale factor at some unknown time and a alone is the scale factor at the present epoch?
Or the other way around?
I'll have a tinker. I still feel a bit lost. Maybe writing some stuff down will help me out some
Thanks =]
I think I'm being dense here
z(t)=\frac{a(t_{0})}{a(t)}-1= \frac{H_{o}}{H(z)}-1
\frac{\delta z}{\delta t_{o}}= \frac{\delta}{\delta t_{o}}(\frac{H_{o}}{H(z)}-1)\frac{\delta}{\delta t}= \frac{\delta}{\delta t}(\frac{H_{o}}{H(z)}-1)
\frac{dt}{dt_{o}}
However there is no time involved in them...
Homework Statement
The redshift of a galaxy is measured at the present epoch t0 and again at the infnitesimal future epoch t0 + δt0. Show that the rate of change of z with t0 is given by
\frac{dz}{dt_{o}}=(1+z)H_{o}-H(z)
Homework Equations
Hint - Start From:
\frac{\delta z}{\delta...
And if shortest distance is best and radiation pressure is not to be neglected (Im here assuming the question is really badly worded and the acceleration it means is that of the rockets propulsion, NOT its total accelration) then above the plane is the way to go, since that will not have...