# Tag Info

2

The main fusion reaction in the sun is the proton-proton chain reaction, which takes six protons and produces two protons, one alpha particle, two anti-electrons, and two electron neutrinos. The deuterium nucleus is only barely bound and can be destroyed — dissociated into a proton and neutron — by absorbing a gamma ray with energy more than 2 MeV. This ...

3

You ask "what would we see", meaning you want to know what kind of radiation is given off. (i) sample from the surface looks like the surface of the Sun. i.e. it emits close-to-blackbody radiation at a temperature of 5800K.Except it now can't be a blackbody since you've taken it out of its environment. A black body is both perfect absorber and a perfect ...

6

Intensity has units of watts per area: $$\left[I\right]=\rm\frac{W}{ m^2}$$ where the area is the surface area of the emitting source (in this case, the sun). This tells you the total amount of radiation present (over all wavelengths). The extra factor of 1/nm in your plot gives the spectral irradiance: $$\left[\mathcal E\right]=\rm \frac{W}{m^2\,nm}$$ ...

2

$W/m^2$ would be the total energy emitted, regardless of wavelength. When you use $W/m^2/nm$ you are explicitly saying that it corresponds to a specific part of the spectrum (nm is a unit of wavelength). Which is what the graph you posted is showing. The first one is called "irradiance", the one plotted here is called "spectral irradiance". For more details ...

1

The formula $$L = \epsilon A \sigma T^4,$$ where $L$ is the luminosity in Watts, can be used for a "grey body" i.e. one that has a constant emissivity with frequency. Here you were told to "assume the Sun to be a perfect blackbody". This means that its emissivity is 1 because a blackbody absorbs everthing incident upon it and because it is in thermal ...

0

People who are studying something something generally use a frame of reference which is reasonably close to the things of interest. While it might in theory be possible to measure the stature of a man by very accurately determining the distance from the center of the Earth to the bottoms of his feet, as well as the distance from the center of the earth to ...

1

A star with a higher metallicity will have a larger interior opacity and a thicker convection zone for a given mass. The thickness of the convection zone is equally important in determining magnetic activity in stars that have an interface between a radiative inner region and convective envelope. The dependence is through the Rossby number - the ratio of ...

1

Earth is rotating on its own axis & also revolves around the Sun, then how come the Sun always rises in the East? Earth orbits around the Sun, but the motion can be expressed equivalently in Earth reference frame as Sun orbiting Earth. The orbital speed is not perfectly uniform, but close enough not to be distinguishable in normal life. Earth also ...

-1

(image credit: Gdr@Wikimedia) Essential answer, assuming the observer near Earth’s equator, is: When the Sun rises, the observer is near the centre of the leading Earth hemisphere (upper side of the blue disk in the image), and east points towards the Sun. At noon, the Sun is above the observer, and east points backward, against the orbital motion. At ...

4

The question is quite geocentric, as it is dependent on the observer's location. On Venus, which has a retrograde axis of rotation, the Sun appears to rise in the West. In Arctic regions, the Sun may not rise or set for up to six months of the year, and even then, it may not be clear in exactly which direction the sunrise/sunset occurs. Other suns in the ...

2

At first ask yourself the question what do you mean by "East"? Other answers have already said that why you should only concentrate on earth spin rather than its orbital motion towards that sun. See North, East, West and South are not absolute directions and changes with the latitude and longitude. So wherever you are on the earth surface, depending on ...

1

It looks like the Sun rises in east and set in west, but actually it is altogether vice versa. Our earth rotates around the sun in west to east fashion. Since we see ourselves as stationary in our frame of reference(i.e. earth), the sun seems to rise and set in east to west fashion. Similarly we have winter and summer as seasons due to the revolution of ...

29

Whether the sun "rises" in the east depends on your position on earth, and the time of the year. In northern latitudes, during the summer, the sun rises significantly North of East, and in the winter it rises in the South. For example, today's sunrise/sunset directions in Umeå Sweden, look like this (source: www.suncalc.net) The yellow line shows the ...

15

The Sun does not rise, it is the horizon that goes down. You say that Sun rises in the East (with a certain degree of oscillations due to the tilt of the axis) just because the Earth spins from West to East. The revolution affects the difference between sidereal time and solar time, and makes the solar day $\approx 4$ minutes longer If the Earth spinned in ...

5

It takes a year for Earth to revolve around the Sun, and only one day to rotate about itself. That is why you can, for most practical purposes, forget about the revolution (which causes the different seasons) and concentrate only on the rotation, at least fo sun raising purposes.

Top 50 recent answers are included