Wouldnt it be nice to be able to render any viewpoint from all the data transformed into a point cloud, an augmented virtual reality of moving objects in our solar system.
I would just like to be able to chose any point in the solar system and view exactly what is there at a specific time.
its possible to extrapolate 3d data from multiple viewpoints of an object, dont we have enough satellite data to do it?
Given the International Space Station's modular design, it appears spacecraft such as Soyuz and resupply freighters such as Progress can attach to many different modules.
This NASA diagram from 2008 shows Soyuz can be attached to four modules:
Here's a 2008 NASA photograph showing two Soyuz craft attached to the ISS. The angle makes it look like they might be attached to one of the US section modules, but in fact they are docked to Pirs and Rassvet. The caption reads:
ESA's Columbus laboratory, Node-2 and Japan's Kibo module at the ISS (main truss at rear, two Soyuz vehicles lower centre)
Here's another NASA image from April 2014 showing two attached Soyuz, captioned:
There are now four vehicles, two Soyuz spacecraft and two Progress space freighters, docked to the International Space Station.
A good question and answer similar to this is the question:
Will the ISS need more docking ports?
Some details on the Russian and US segments future plans as well as current situation is available in that question.
Big Bang theory is rather adequate, with respect to observations. But it's incomplete. Your question is about the pre-planck epoch, a state of the universe, when space and time didn't exist in a way we are used to in standard physics.
Nothing is really known (by empirical evidence) about this state, although there are theoretical approches (e.g. this one), which try to describe even those highly non-local and non-causal structures, from which "eventually" the Planck epoch could emerge.
The Planck epoch, lasting from zero to about $10^{-43}mbox{ s}$, the Planck time, is still far from being understood, since the energy needed to fully investigate this state of the universe is far beyond accessible to experiments. We just know, that neither general relativity nor quantum theory describe this state correctly. Research about quantum gravity tries to fill this gap.
You may think of the pre-Planck and the Planck epoch as a state of the universe, which is dominated by quantum fluctuations. They don't need a reason or a cause to occur. They are a consequence of Heisenberg's uncertainty principle.
As an example, if you try to measure time with very high precision, you'll get an increasing uncertainty in the energy measurement of the observed particle (time-energy-uncertainty). Within the very short Planck epoch, high energy fluctuations needed to occur, since both values (time and energy) cannot be pinned down together.
The reason for the Big Bang is thought to be such a kind of quantum fluctuations, yet not understood in very detail.
Questions like where?, when?, and why? don't apply in the intuitive sense to quantum phenomena. It's more a matter of probabilities, waves, and relations between observable values, without the observable values themselves being defined independently.
This can only happen if the moonrise at a certain date is earlier than the moonrise at the previous day. There are two reasons why this could happen:
See for instance the figure below where each drawing is at the same time of day. The moon will increase its right ascension during the day (along the celestial equator downwards, the red arrow in the figure). If the observer is on the Earth's equator, moonrise will be later the next day. It does not matter whether the declination (the position above or below the celestial equator (to the left or right in the figure)) will increase or decrease. All objects with the same right ascension will rise at the same time on the equator. If the observer is not on the equator but near one of the poles (for instance at 65° latitude north), the increase in declination may be sufficient to counteract the increase in right ascension (see bottom panel). Note that even though the right ascension increases (the moon moves left along the celestial equator axis), the Moon will rise earlier during the day.
This only works (in the Northern hemisphere) when the Moon increases its declination (the height above the celestial equator) very rapidly. This happen only when the Moon is near the Vernal Equinox (i.e. in Aries or Pisces). And the observer needs to be at a high latitude (i.e. near the North pole such as Thule as mentioned by @barrycarter)
METHOD 3 Predicting Periastron Times and Cycle Durations from Orbital Phase ($Phi$)
In the answer by Stan Liou he uses a Taylor Series approximation of the Mean Anomaly to derive a nice formula which determines the CPTS (Cumulative Perihelion Time Shift) value as a function of $t^2$. This formula produces results very close to those graphed by Weisberg & Taylor. As it took me a while to understand how the Mean Anomaly can be applied for a decaying-period orbit I thought it useful to note here what I learnt and present a slightly different way of obtaining a formula to predict periastron times.
Mean Anomaly basically indicates the phase of the orbit at a particular epoch, e.g. what time fraction of the orbit period has been completed. For Mean Anomaly the fraction is scaled by $2pi$. Let $Phi(t)$ be the phase of the orbit at time $t$ such that at the start of the orbit $t=0$ and $Phi(0)$ = 0 and at the end of the orbit when $t=P$ (the period of orbit) $Phi(P)$ = 1. I will assume that an orbit starts at one periapsis and finishes at the next periapsis.
In a decaying-period orbital system the value of $P(t)$ changes with $t$. Here $P$ is the period of orbit. In a decaying-period orbit I will assume that orbital phase $Phi(t)$ is completely specified by time $t$ and either $P(t)$ or $F(t)$, i.e. aspidial precession, progressive changes in semi-major axis length or eccentricity do not lead to significant additional changes in phase.
In a decaying-period system the concept of period at a given epoch is somewhat abstract, it might be construed as a hypothetical period that would occur thereafter if the force causing period change ceased at that particular moment. Instead of period we can think in terms of $F(t)=1/P(t)$ where $F$ is the orbital frequency.
I like to think of $F(t)$ as "the rate of change of phase with time", i.e. $F(t) = dot{Phi}(t)$. Picture an imaginary phase clock comprising a circular dial whose circumference has markings running from $Phi=0$ around in a full circle to $Phi=1$. The phase $Phi(t)$ of our subject system at any given epoch $t$ will be indicated by a marker at a particular point on the circumference of the dial. Then $F(t)$ can be thought of as the speed at which the marker is moving around the circumference of the dial at a given epoch $t$. In a particular short interval of time $delta t$ the (system state) marker will move a certain distance around the dial and this distance travelled will indicate the change in phase. The "travel" (change of phase) will depend on the value of $F$ during that time as per $delta Phi approx delta t * F(t)$. This is only approximate because F(t) changes during the interval $delta t$.
Now let us assume that the time interval $T$ between succesive periaspes is known and that the time of the first periapsis is at $t=0$. If $P(t)$ (and therefore $F(t)$ too) changed in a step-wise manner between time intervals, then we could write
$$
sum_{i=1}^{i=N=T/delta t} frac{delta t}{P(t)}
=
sum_{i=1}^{i=N=T/delta t} delta t F(t)
=
sum_{i=1}^{i=N=T/delta t} delta Phi(t)
= 1.
$$
To represent continuously-changing $P$ and $F$ we reduce $Delta t$ towards zero and obtain these integral functions
$$
int_{t=0}^{t=T} frac{1}{P(t)}, mathrm{d}t
=
int_{t=0}^{t=T} F(t), mathrm{d}t
=
int_{t=0}^{t=T} dot{Phi}(t), mathrm{d}t
= 1.
$$
At any time $tau$ during the orbit ($0leq tau leq 1$) the current instantaneous phase is given by
$$
Phi(tau) =
int_{t=0}^{t=tau} dot{Phi}(t), mathrm{d}t
=
int_{t=0}^{t=tau} F(t), mathrm{d}t
=
int_{t=0}^{t=tau} frac{1}{P(t)}, mathrm{d}t.
$$
and given a constant value of $dot P$ (the rate of change of period), and $P_o=P(0)$ we obtain
$$
Phi(tau)
=
int_{t=0}^{t=tau} frac{1}{P_o + dot P t}, mathrm{d}t
qquad mathrm{and} qquad
dot{Phi}(tau) = F(tau) = frac{1}{P(tau)} = frac{1}{P_o + dot P tau}.
$$
Using
$$
frac{mathrm{d}}{mathrm{d}t} left(
frac{1}{f(x)}
right)
=
frac{-dot f(x)}{f(x)^2}
qquad mathrm{and} qquad
f(x) = P_o + tau dot P
qquad mathrm{and} qquad
dot f(x) = dot P
$$
we get
$$
ddot Phi(tau)
=
frac{mathrm{d}}{mathrm{d}t} left(
frac{1}{P_o + tau dot P}
right)
=
frac{-dot P}{P_o^2 + (tau dot P)^2 + 2 P_o tau dot P}
$$
and for $tau = 0$ we get
$$
Phi(0) = 0
qquad mathrm{and} qquad
dot{Phi}(0) = frac{1}{P_o }
qquad mathrm{and} qquad
ddot Phi(0)
= frac{-dot P}{P_o^2}.
$$
PREDICTING PERIASTRON TIMES
We can obtain an expression for CPTS by copying Stan Liou's approach , but using phase ($Phi$) instead of Mean Anomaly ($M$).
Write the phase at time $tau$ as a Maclaurin series (a Taylor series with $a=0$):
$$begin{eqnarray*}
Phi(tau) equiv int_{t=0}^{t=tau} dot{Phi}(t),mathrm{d}t
&=& Phi(0) + dot{Phi}(0) tau + frac{1}{2}ddot{Phi}(0) tau^2 + mathcal{O}(tau^3)\
&=& 0 +frac{1}{P_0}tau - frac{dot{P}}{2P_o^2}tau^2+mathcal{O}(tau^3)text{.}
end{eqnarray*}$$
Dropping the third order and residual error terms (Stan Liou's answer explains justification for this) we get
$$
Phi(tau) approx frac{1}{P_0}tau- frac{dot{P}}{2P_o^2}tau^2.
$$
Let $N$ count the number of completed orbits at some time $tau_N$. Then the phase at the end of orbit number $N$ is given by $Phi(tau_N) = N$. In a steady system (A) the orbital period $P_o$ stays constant $dot P=0$ and so the time $tau_{NA}$ at which the $N$th orbit completed is given exactly by $tau_{NA} = NP_o$ and thus $N=tau_{NA}/P_o$. In a decaying-period system (B) the Nth orbit completes at time $tau_{NB}$ when $Phi(tau_{NB}) = N$ but with $Phi(tau_{NB})$ depending on a non-zero value of $dot P$.
$$
begin{align}
&Phi(tau_{NA}) = N = frac{1}{P_0}tau_{NA}\
&Phi(tau_{NB}) = N approx frac{1}{P_0}tau_{NB}- frac{dot{P}}{2P_o^2}tau_{NB}^2.
end{align}
$$
We can obtain a formula for $Delta t_{N}$ which is the difference in time between $tau_{NB}$ (the epoch of the decaying system $N$th periastron) and $tau_{NA}$ (the epoch of the steady system $N$th periastron) as follows. Note that following Weisberg & Taylor we define $Delta t_{N},(=$ CPTS $)=tau_{NB} - tau_{NA}$. The $N$th periastron in the decaying period system occurs earlier than the $N$th periastron in the steady system. Therefore $Delta t_{N}$ (=$ CPTS $) will become increasingly negative as time passes (as $t$ increases).
$$
frac{tau_{NA}}{P_o} = N approx frac{tau_{NB}}{P_0}- frac{dot P}{2P_o^2} ,{tau_{NB}}^2
$$
$$
{tau_{NA}} approx {tau_{NB}} - frac{dot P}{2P_o} ,{tau_{NB}}^2
$$
$$
Delta t_N
= tau_{NB} - tau_{NA} approx + frac{dot P}{2P_o} ,{tau_{NB}}^2
$$
which is Stan Liou's approximation for $Delta t_N$.
So what value is this equation?
In general assume that we have determined the time $t_0$ of the $0$th periastron and measured accurately an initial orbital period $P_o$ and we keep track of the observed periastra.
Case 1 - we observe that the $N$th periastron occurs at a particular time ($tau_{NB}$). Using $tau_{NA}=N P_o$, we can easily calculate $Delta t_N = tau_{NB} - tau_{NA}$. Then, using Stan Liou's approximation of $Delta t_N$ we can obtain an empirical estimate of $dot P$ from
$$
{dot P} = frac{2 P_o ,Delta t_N} {tau_{NB}}^2.
$$
Case 2 - we have a theoretical formula which, given our measurement of $P_o$ predicts the value of $dot P$. Given various values of $N$ and using $tau_{NA}=N P_o$ we can easily calculate the hypothetical epochs ($tau_{NA}$ for various $N$) of the hypothetical steady-system periastra. Now we wish to plot a curve showing the theoretical values of $Delta t_N$ at various hypothetical periastron epochs ($tau_{NA}$). But Stan Liou's equation for $Delta t_N$ uses $tau_{NB}$ not $tau_{NA}$. We need to find $Delta t_N$ as a function of $tau_{NA}$. Therefore we would need to solve the following quadratic equation for $Delta t_N$ in terms of $tau_{NA}$ and $K$, where $K=frac{dot P}{2 P_o}$:
$$
Delta t_{N} = K {tau_{NB}}^2 = K ({tau_{NA}}^2 + 2 tau_{NA}Delta t_{N} +{Delta t_{N}}^2)
$$
$$
0 = (K{tau_{NA}}^2 + 2K tau_{NA}Delta t_{N} +K{Delta t_{N}}^2) -Delta t_{N}
$$
$$
0 = (K){Delta t_{N}}^2 +(2K tau_{NA} -1)Delta t_{N} +(K{tau_{NA}}^2)
.$$
The following way of getting an equation for $Delta t$ is more protracted but it will provide a formula for $Delta t$ as a function of $N$ (which can easily be converted into a function of $tau_{NA}$).
Starting with
$$
frac{tau_{NA}}{P_o} =frac{1}{P_0}tau_{NB}- frac{dot P}{2P_o^2} ,{tau_{NB}}^2
$$
$$
tau_{NA} =tau_{NB}- frac{dot P}{2P_o}{tau_{NB}}^2
qquadrightarrow qquad
0 = -tau_{NA} + tau_{NB} - frac{dot P}{2P_o} ,{tau_{NB}}^2
$$
Using $ x = frac{-b pm sqrt{b^2-4ac}}{2a}$ with $a=- frac{dot P}{2P_o} , b=1, c=-tau_{NA}$ we obtain
$$
tau_{NB} = frac{-(1) pm sqrt{(1)^2-4(- frac{dot P}{2P_o}).(-tau_{NA})}}{2(- frac{dot P}{2P_o})}
$$
$$
tau_{NB} = frac
{1 pm sqrt {1 - 2 frac{ dot P }{P_o}.tau_{NA} }}
{dot P /{P_o}}
qquad longrightarrow qquad
tau_{NB} =
frac{P_o}{ dot P } left( 1 pm sqrt {1 - 2 frac{dot P }{P_o}.tau_{NA} },, right)
$$
Now $tau_{NA} = P_o ,N$ so we can write
$$
tau_{NB} =
frac{P_o}{ dot P } left(1 pm sqrt {1 - 2 dot P N } right)
qquad longrightarrow qquad
-Delta t = tau_{NA}-tau_{NB}
= P_o left( N -frac{1}{ dot P} left(1 pm sqrt {1 - 2 dot P N } right) right)
$$
= = = = = = =
We can try a simple approximation of this using $(1+alpha)^{0.5} = (1+ 0.5alpha)$ so that $sqrt {1 - 2 dot P N } approx 1- dot P N$ and by inspection the "$pm$" becomes a "$+$"
$$
-Delta t
= P_o left( N -frac{1}{ dot P } left(1 pm 1 - dot P N right) right)
= P_o ( N - N )
= 0
$$
This is a valid approximation but it goes a bit too far for our purposes! We know that $tau_{NA}-tau_{NB} neq 0$. So let us try expanding the term $[1 -2 dot P N]^{0.5}$ in a series expansion,
$$
[1 + (-2 dot P N)]^{0.5}
= 1 +frac{1}{2}(-2dot P N)^{1} -frac{1}{8}(-2 dot P N)^{2}
+frac{1}{16}(-2dot P N)^{3}+...
$$
$$
[1+ (-2dot P N)]^{0.5}
= 1 - dot P N -frac{1}{2}(dot P N)^{2}
-frac{1}{2}( dot P N)^{3}+...
$$
Let us limit ourselves to terms with $ dot P $ to the power of $2$ or less thus
$$
[1-2 dot P N]^{0.5} approx
1 - dot P N -frac{1}{2}dot P ^2 N^2 .
$$
We can insert this into the time difference equation
$$
-Delta t
approx P_o left( N -frac{1}{ dot P }
left(1 pm (1 - dot P N -frac{1}{2} dot P ^2N^2 right) right)
$$
by inspection the "$pm$" becomes a "$-$"
$$-Delta tapprox P_o left( N -frac{1}{ dot P }
left( + dot P N +frac{1}{2}dot P ^2 N^2 right) right)
qquad longrightarrow qquad
-Delta tapprox P_o left( N - left( N +frac{1}{2} dot P N^2) right) right)
$$
$$
-Delta t approx -frac{1}{2}P_o dot P , N^2
qquad longrightarrow qquad
Delta t approx frac{1}{2}P_o dot P , N^2
$$
From the Weisberg & Taylor paper we are given $P_o=27906.979587552 s$ and $dot P = -2.40242 *10^{-12} s/s$
so $frac{1}{2}P_o dot P = -0.5 * 27906.979587552 * 2.40242 *10^{-12} = -3.352216747 * 10^{-08} s$.
With $N= 10,000$ cycles we get $Delta t = -3.352217 s$.
Note that we can make the substitution ${tau_{NA}}^2 = N^2 Po^2$ into the equation for $Delta t$ to give
$$
Delta t approx frac{1}{2}P_o dot P , N^2 = frac{1}{2} frac {dot P}{P_o} ,{tau_{NA}}^2
.$$
The difference between this $Delta t$ and the value of $Delta t$ from Stan Liou's equation is
$$
frac{1}{2} frac {dot P}{P_o} left( {tau_{NA}}^2 -{tau_{NB}}^2 right)
$$
$$
=
frac{1}{2} frac {dot P}{P_o} left(
{{tau_{NA}}^2
-tau_{NA}^2 +2 tau_{NA} Delta t + Delta t^2} right)
$$
$$
=
frac{1}{2} frac {dot P}{P_o} left(
{2 tau_{NA} Delta t + Delta t^2} right)
$$
and the difference as a fraction of $Delta t$
$$
=
frac{1}{2} frac {dot P}{P_o} left(
{2 tau_{NA} + Delta t} right)
.$$
For the present case $(dot P/P_o approx 8.6 * 10^{-17})$ and so, after 34,000 periastron cycles (948,838,000 s, about 30 years) the difference between the two approximations of $Delta t$ would be only $0.8 * 10^{-8} s$ which is much smaller than the time resolution of the observations.
PREDICTING CYCLE DURATIONS
We can also derive an expression for the cycle duration $D$, as follows.
The start periaston is at $t=0=T0$ and the first following periaston is at $t=T1$ then
$$
Phi(T1)=int_{t=0}^{t=T1}frac{1}{P(t)},mathrm{d}t = 1
$$
this can be expressed as
$$
1 =int_{t=0}^{t=T1}frac{1}{ dot{P} t + P_0 },mathrm{d}t
= left[ frac{1}{dot{P}} ln ( Cdot{P}t + CP_0 )right]_0^{T1}
$$
hence
$$
dot{P} =
ln ( Cdot{P}T1 + CP_0 ) - ln ( CP_0 )
=
ln left( frac{ C ( dot{P}T1 + P_0 )} { C ( P_0 )} right)
=
ln left( frac{ dot{P}T1 + P_0 } {P_0 } right)
$$
$$
rightarrow exp(dot{P})
= frac{ dot{P}T1 + P_0 } {P_0 }
rightarrow
P_0 exp(dot{P}) -P_0
= dot{P}T1
$$
giving us
$$
rightarrow
T1 =
P_0 frac{exp(dot{P}) -1} {dot{P}}
$$
so the duration of the first orbit (from start periastron to first following periastron) is $D_1 = T1-T0 = T1$ thus
$$
D_1 =
D_0 frac{exp(dot{P}) -1} {dot{P}}
$$
and we can generalize this to
$$
D_{N} =
D_{N-1} left( frac{exp(dot{P}) -1} {dot{P}} right)
.$$
For example using the made-up value $dot P = -2.34,10^{-8}$ we obtain
$$
D_{N+1} =
D_{N} frac{exp(-2.34*10^{-5}) -1} {-2.34*10^{-8}}
= 0.999 999 988 D_{N}
$$
However, using standard arithmetical software (such as Excel) when we try to calculate using $dot P = -2.34,10^{-10}$ we get nonsense results because of truncation errors. The approximate value of $dot P$ reported for the Hulse-Taylor system is about $-2.34,10^{-12}$.
We can analyze the formula for $D_{N+1}$ using series expansions. A Taylor Series expansion of $exp(x)/x -1/x$ is given by WolframAlpha as
$$
exp(x)/x -1/x= 1 +
frac{x}{2}
+ frac{x^2}{6}
+ frac{x^3}{24}
+ frac{x^4}{120}
+ frac{x^5}{720}
+ frac{x^6}{5040}
+ frac{x^7}{40320}
+ frac{x^8}{362880}
+ frac{x^9}{3628800}
+ frac{x^{10}}{39916800}
+O(x^{11})
$$
or
$$1 + frac{x^{2-1}}{2} + frac{x^{3-1}}{3*2} + ... frac{x^{i-1}}{i!} + ...$$
No easilly computable expression or approximation is obvious at present.
Proceeding anyway, it is clear that the duration of any subsequent orbit $N$ can be computed from
$$
D_N
=
D_0 left(frac{exp^{dot P} -1} {dot P} right) ^N
=
D_0 left(frac{1}{dot P} right)^N left(exp^{dot P} -1 right) ^N
$$
It is interesting to compare this expression for cycle duration with that which was used as the basis of the coarse binomial solution (see other answer: Method 4)
$$D_1=D_0(1+dot P)^1$$
The ratio of durations Phase-based to Coarse binomial based is
$$
D_0 left( frac{exp(dot P)-1}{dot P} right)^{1}
:D_0(1+dot P)^1
$$
becoming
$$
frac{exp(dot P)-1}{dot P}
:1+dot P
qquad rightarrow
exp(dot P)-1
:dot P +dot P^2
qquad rightarrow
exp(dot P)
: 1+dot P +dot P^2
$$
applying the series expansion of $exp(dot P)$ we obtain
$$
qquad rightarrow
1+dot P + frac{dot P^2}{2} + frac{dot P^3}{6} + frac{dot P^4}{24} +,...,
: 1+dot P +dot P^2
$$
Clearly the two expressions give different values for cycle duration $D$ and the difference appears at the term in $dot P^2$ and seems to be no bigger than $frac{dot P^2}{2}$.
The images of New Horizons from Pluto will take more a year to arrive from space, for the moment with have some compressed images as a preview.
Nasa has advanced some information regarding the geologically inactive zone, but there has been no information regarding the possible geologically active zones, on the formation of the plateaus and the mountains.
What forces could be driving geothermal activity of what nature on Pluto? What can be learnt from theories of the moons of Jupiter and Saturn to understand activity inside of Pluto? What is the theoretical temperature of the center of the dwarf planet?
It is thought likely that black holes would produce Hawking radiation and evaporate. We can't yet describe the end products of an evaporating black hole, and space is too warm to detect Hawking radiation anywhere. There are some recent new ideas regarding complementarity that are difficult to reach a decision on as well.
Hawking seems to be pulling away from the black hole concept recently. I don't know what to make of that.
Regarding particle colliders: every few years some team gets into the general news cycle with an announcement about detections that resemble particular models of black hole behavior. Miscommunication tends to produce journalism about real black holes being created. Now there may be developing interest in the possibility of the galactic core lighting up. Maybe that would lead to better journalism.
Our day is 23 hours and 56 minutes long, and slowing by an infinitesimal (but measurable) amount each year due to tidal losses.
Our day has a connection with the weather, in that the sun drives all our weather systems, so heating over each part of the globe happens every day, but aside from that, your question doesn't make much sense.
Weather changes may come at the same time where you live (on a 24 hour cycle) but here in Scotland, we still have low reliability on even a 3 day weather forecast, because the weather systems that impact the UK are so complex as heating from the sun drives various air flows.
After your update, I still cannot understand what you mean. There is slippage in accuracy, but this is counteracted by leap seconds and leap years. It has nothing to do with weather. The shortest and longest days happen when they happen and are measurable. They help us define the year.
When the light from two telescopes is combined to make an interferometer, the resolution of the combined instrument is equal to the resolution of a single telescope with a diameter equal the the distance between the two (or more) smaller telescopes. This is the technology you need to view exo-planets to any resolution you want.
This has been incredibly successful in radio astronomy. Long baseline radio astronomy gives the resolution of a radio telescope the size of the diameter of the Earth. Optical telescopes in space can be even bigger. Arrays of relatively small telescopes with specially calculated spacings can do even better. Big mirrors are still better in order to get enough light on a sensor to be useful.
The twin Keck telescopes in Hawaii can form an interferometer but funding has dried up at the moment. It has an effective size of 280 feet. I don't know why there is no funding, but at this point it may be likely that a space-based interferometer would work so well that finishing the ground based instrument is not cost effective. Or the time required to set up and get data is a poor trade-off compared to other demands for telescope time. Also, longer IR is better for the planet imaging and space is a lot better place for that.
For some reason, this is a hot topic among PhD candidates, but a delay in getting pictures of these objects is not going to mean much for the rest of us.
In slow-roll inflation models, the early inflation of the universe is driven by the flat non-zero part of the inflaton potential, and it ends as the ball rolls down the cliff and the potential energy released leads then to the formation of matter.
However, as I have heard such slow-roll models are no longer deemed realistic today in inflationary cosmology, instead other models where the end of the inflation is explained by quantum tunneling of the universe from a state with higher vacuum energy density to another state with lower vacuum energy density are considered for example.
Why (from a physical point of view) are slow-roll inflation models no longer considered to be realistic, what are their disadvantages? What can models that explain (the end of) the early inflation by a tunneling transition between to vacua explain or describe, that slow roll models can not do?
It's not completely clear what you are asking, but if this is a multi-choice quiz, then the only option that could be correct is (a).
(b) Is not correct, because a white dwarf that just passes the Chandrasekhar mass is comfortably below the maximum mass that is supportable by a neutron star. So neutronisation followed by neutron degeneracy pressure and the strongly repulsive nuclear force between neutrons at small separations ought to be capable of preventing black hole formation.
(c) Is not correct because by definition, type II supernovae result from the collapse of massive stars. Observationally, they are distinguished by hydrogen absorption in their spectra, but since a white dwarf will contain little if any hydrogen, then this is not possible.
(a) Might happen. As mass is added to the white dwarf it will become smaller and denser. It is possible that nuclear reactions (carbon fusion) might begin. Because the white dwarf is supported by temperature-independent electron degeneracy pressure, then the nuclear reactions take off at constant density, but the increasing temperature leads to runaway nuclear reactions that detonate the star as a type Ia supernova.
There are many different ways to get spatial information about the surface of a star besides direct imaging.
Direct imaging is difficult because the angular resolution available goes as $lambda/D$.
For a 8-m telescope and light at 500 nm, one can resolve $6times10^{-8}$ radians (assuming the blurring of the atmosphere can be overcome by adaptive optics or similar).
The nearest stars are a couple of parsecs away, so the smallest spatial scales that could be resolved are $sim 2times 3.1times10^{16} times 6times10^{-8} = 3.7times10^{9}$ m, or about 500 solar radii. Hence no surface features or even a disk could be resolved.
Of course you could use interferometric techniques to effectively increase the size of $D$ and measurements of the angular radii are now possible for many nearby stars or giant stars at larger distances.
Surface imaging is harder. Indirect techniques are much more common. These include doppler imaging and eclipse mapping. The former uses the fact that there is a relationship between the position of a bright/dark feature on a rotating star and the doppler shift of the light from that feature. By observing a time-series of spectra, the lumps and bumps in spectral lines can be inverted to produce a "doppler map" of the surface. The technique is usually limited to stars that are considerably more rapidly rotating than the Sun. There is a lot of ambiguity in the image reconstruction process - many surfaces could lead to the same observable sigature and clever statistical techniques (and even philosphies) have to be deployed to choose between them. Many stars have published "doppler maps" of their surfaces. Here is a typical example of such a study and below I show an example of a "doppler image" for the star II Peg (a K-type subgiant), from Gu et al. (2003), showing dark spotted regions. A typical resolution for such an image is about 10 degrees on the star.
Eclipse mapping, for which I can't easily locate a good link, uses the fact that a star/accretion disk is orbited by another star or planet that periodically eclipses it. What happens to the light from the system in and out of eclipse can be used to probe the surface of the eclipsed object. There are of course limitations to the spatial resolution that can be obtained, depending on the size of the eclipsing object, how long the eclipse takes and how wide the orbit is. But useful constraints can be made on the structure of accretion disks, sizes of starspots etc, although "maps" are not usually produced. A recent example using the transits of a planet to probe starspot structure is Roettenbacher et al. 2013.
Another possibility is rotational modulation. Features on the surface that rotate around are self-eclipsed by the star and produce modulation of the observed light. This can be used to try and estimate e.g. the size and location of starspots. Again there are many degeneracies and ambiguities, but this has become a growth industry since the delivery of thousands of extremely high quality light curves from the Kepler satellite.
Actually, you sometimes can see the Moon illuminated by the Sun from the top, and therein lies the answer to your question - during day. When looking at the Moon during night time, the side of the Earth where you're standing and looking at it is pointed away from the Sun, while this is reversed during the day. The illuminated side of the Moon is also facing the Sun, of course. So we have:
So, the direction from which the Moon is illuminated from is the same as the direction the Earth is, both illuminated by the same celestial body - our Sun. So, when you see the Sun high above the skies, and if the Moon is visible during daytime, it's going to be illuminated from the same direction from which you are, and during night time, when you'd expect the Sun "below where you're standing", it's illuminated from that direction.
Your premise is incorrect. We used to think Mercury was tidally locked, but since 1965 we now know it is in a 3:2 spin-orbit resonance, which gives it (long) days.
Anything you read that says it is tidally locked is old, or itself using old reference material.
Here are some quick sketches to show the orbit, relative orientation of the planet, and the sidereal and solar days. If you like it as an answer I'll redraw with a graphics tool instead of my iPad Pen app...
I'm parsing FITS files for a project based on data from a telescope. These files include 'DEC', 'RA' and lat long values. I understand roughly the concept of celestial coordinates and I assume that these values are sufficient to calculate the direction that the telescope is facing and the angle that it's at but my trigonometry is not up to the task.
I am using astropy for the project so any answers which reference that would be great.
This is actually a very nice example of why black holes are such extreme objects, they even break the basic rules arithmatic:
Black hole math: $$1 text{ black hole} + 1 text{ black hole} = 1 text{ black hole}$$
(this is a little insider science joke)
A black hole is a region of space from which nothing, not even light, can escape. To achieve that it must have very strong gravity, so a lot of mass in a small region of space. So we may call it a "hole in spacetime", but it still has a mass.
In physical sense black holes can be described by only three quantities:
All these three properties can change if the black hole is fed with 'stuff'. If you add matter the black hole mass increases. If that matter has (aligned) angular momentum, the black hole will spin faster and if the matter is charged, then the black hole charge changes accordingly.
When dealing with merging black holes, it is the mass property that is important. If I repeat the black-hole-math for its mass you get
$$ 1 text{ black hole mass} + 1 text{ black hole mass} = 2 text{ black hole mass} $$
So a merger of two identical black holes just gives a single black hole with twice the mass.
Such black hole mergers are probably less hypothetical than you might think. They are considered to be likely method of creating supermassive black holes and are also considered as a potential source for gravitational wave emission.
In a car, you have a perception of speed because of (a) the "wind" passing by as you rush through the air which is not moving at the same speed as the vehicle, and (b) you perceive the stationary objects nearby as "moving" off into the distance behind.
As the earth moves in its orbit, you don't notice any "wind" from the planet rushing through space, as the atmosphere of the earth is moving along with the planet. There isn't any substance to the space around the planet to create an impression of "wind". The car is surrounded by air, so when you move through the air, you have an impression of moving because of the air rushing past. Because the planet isn't moving through an especially gaseous medium, there is no impression of movement, no "wind".
Also when it comes to our planet, there is nothing "nearby" to create a reference point that would make it appear as if we are moving relative to that reference. Even the closest of objects, such as the moon, are sufficiently far off that the only obvious impression is that these move and we are still. Hence the reason why the geocentric view of our world was dominant for so long.
Even sitting still at home, your entire body is moving at the same velocity as the rest of the planet, so your brain isn't being jostled or 'gyrated' at all. If someone shook you, then your velocity would be changing and your body would feel the effects of acceleration, and then you would be jostled and gyrated. But that is because you are perceiving sudden and rapid changes in velocity, accelerations.
I can't give a good answer but I did find the documentary and out of curiosity, watched some of it, skipped forward and found the hologram section you're talking about, it's at the end about 1:18:40 in. (I'm not going to post a link to the video cause I'm not sure it's correctly copyrighted by those who are showing it)
The video itself isn't bad, but it's basically a science channel level program, which is written to appeal to viewers and explanations are often over-simplified. This video in particular seemed to try to cover so much ground that it explains very little. But on the positive side, they have Brian Greene and Leonard Susskind discussing the hologram idea and those guys are both real physicists who've talked about this before. I don't think it's a main stream idea, just an idea that a few people like.
Here's a magazine article on the subject and an excerpt from Brian Greene's book.
and Here's Leonard Susskind giving a talk on the subject at Stanford, not at a class, more of a lecture cause he mentions that not everyone in attendance might be a physicist, but I've since watched his lecture and he makes a few of these points more clear, at least to me.
And Here's a question and answer on a similar subject. There's also no shortage of articles that can be found on the Holographic principal or the "universe is a hologram", though I think the first is a better set of words to search and the 2nd might lead you to some sub-par articles.
Philip Gibbs - inactive's answer (also in the link above) on what the Holographic Principal implies is better than anything I could say about it, so I'd start there.
As a rule, it's a good idea to post links and if the video is 2 hours long, the specific time as well. YouTube links can also be removed so they're not ideal.
Edit to answer questions.
Had to think about this one a bit, and sometimes trying to answer "why" is opening a can of worms, but . . . here I go.
Why do they think that it is our Universe that is the Holograph?
I'm not a fan of the theory myself and I'd guess that not all physicists agree with it either. One big problem with the theory is that it can't be proven, which really makes it more of a guess based off a mathematical model and not a good theory. One definition of a good theory is one that can be tested. If it can't be tested true or false, it's really more of an idea.
As for why Brian Greene likes the theory, you might need to ask him or search his interviews, but maybe he likes it so can sell books - I don't know. Maybe he likes the idea of the Universe being a Hologram. He's obviously a pretty smart guy. You don't get a PHD in physics and get recognition and invited to ted talks and all that by being dumb, but smart guys are wrong all the time when it comes to new theories. There's no evidence that this theory is true.
Now, I should point out that the Holographic principal as it applies to black holes and the information paradox, all that stuff is good and valid theoretical physics rooted in ideas we understand such as entropy and time dilation and red-shift. The Holographic principal seems a very reasonably deduced feature of black holes that also, cleverly answers the information paradox, but whether it can be extrapolated to apply to the entire universe is a whole different ball game and to me, it's basically a guess. Not much more.
Why couldn't our Universe be reality and a Holograph exists of it
somewhere else?
Well, I could say "you're right", but the truth is, you're just flipping around the question. The more relevant questions are whether the theory is true at all, and as I said above (and Susskind said in his video), whether it can be tested. Susskind's video is really quite good though he starts slowly, but if you're really interested in this it's worth watching.
What makes them think that this is the Holograph instead of the
reality?
One thing about Physics to keep in mind. It's often surprised us. Physics has given us answers that physicists didn't expect many many times, perhaps more than any other field of study. Physics is probably more likely to yank the rug of reality out from under us than any other field and with that in mind, it's not a subject to study if you want to feel secure in what you believe and know. In the days after Newton, Physicists were very confident in what they knew and felt that nothing very new was out there, though the constant speed of light was a puzzle they'd not expected.
Then Einstein came along and pretty much threw everybody's understanding out the window when he started to figure things out and not long after that, the quantum physicists came up with ideas that made Einstein's head spin and to which he directly disagreed. After that the big bang was unexpected, background radiation was unexpected. Dark matter was unexpected (except for maybe Fritz Zwicky) and dark energy was quite the surprise when it was discovered.
Being regularly surprised, of-course, doesn't make the hologram theory any more true or false, cause nobody knows, but good physicists these days try to keep an open mind to mathematically valid new ideas.
