# Tag Info

1

I'd like to know what would happen if Venus was flung into a highly eccentric orbit like Sedna (except maybe with its current perihelion) with an orbital period measured in thousands of years. It's kind of a weird question but the first thing to consider is whether the orbit crosses any other planetary orbits, cause if it does, the biggest effect of ...

0

To determine transit UTC transit time of a celestial object; (360 plus your Longitude) minus star SHA= GHA Aries Get GHA Aries from The Nautical Almanac here; www.TheNauticalAlmanac.com To determine transit time of the Sun on your meridian (Longitude); Sun GHA = your Longitude. Let's say you're located at W 078 degrees 42 minutes. Date- November 18, ...

0

At my university it is, but that just basically means you get forced to do some Freshman Computer Science, Computational Physics(which is optional in other streams such as Laser and Nuclear Physics) and also Complex Analysis and Fourier Analysis in undergraduate. I'm not sure how it works in other universities, but that's our undergrad version of Theoretical ...

0

Speed of sound usually refers to the propagation velocity of a low amplitude vibration in a medium in equilibrium. A "sound" can travel far faster than the speed of sound if it is, for example, a shock wave

0

it's likely that when you google the term in general, most pages treat about the "speed of sound" at the common human meaning (sound in air :-) ), while its generalization to all the various circumpstances of fluids in the universe might more often been spelt "sound speed". But here it's more linguistic than physics, and it wouldn't be physically incorrect ...

2

I think it has to do with their relative intensities and the high density of food compared to the low density of the universe, This is correct. The microwave ovens are not working with a black body radiation curve with an average of 3K , nor is the heating effect a thermal balance between two black bodies: food and microwave. Bodies in space away from ...

3

The reason that there is a CMB is because of the big bang. The photons from the very beginning of our universe has spread (almost)uniformly throughout the universe to give rise to a general noise which we call background. Now to answer your question, as the universe expanded after big bang the photons got redshifted and their energy decreased. Now the avg ...

4

Although not a complete answer, one place to start is with the coldest naturally occurring place in the universe, which is the Boomerang Nebula, a planetary nebula that is around 1 K. As best as I can tell, this cooled below the CMB temperature simply by adiabatic expansion, and is insulated in its interior from CMB heating. Is this a feasible way to get to ...

2

There is another big problem with ultra-small luminosities: due to the small initial light + 1/r² decrease, it might be that only a few photons per hour sent by your target planet reach the diameter of Earth (better be in your telescope ! ). At very small luminosity you have to remind that light is not continuous and made of photons. And way before the ...

2

The spatial resolution of a telescope is going to be limited in what it can resolve by something called the diffraction limit. Basically, light can only be focused so much by a lens given its initial starting size and the focal length of the lens. Its useful to think about this in terms of angular resolution for the case of telescopes, and the minimum ...

1

the answer is no: for now there is a high correlation between the properties of planets (size, distance to their star) and their probability to be detected, which totally bias the observed distribution.

2

There are several broadband light sources in outer space such as quasars and blazars which basically can act as a light bulb. Earth bound telescopes as well as satellite telescopes can see absorption features in the light when the light passes through some cloud in outer space that contains molecules before the light reaches earth. In addition molecules in ...

2

The elements you give describe an idealised orbit that does not exist in reality. Those numbers are parameters to an approximate model. Earth's closest distance to the sun is different each and every year, by a lot (about 20,000 km in fact). Are there any exact data about Earth's orbit? There are certainly far better models than the 6-parameter ...

1

A Galaxy cluster could have $10^{14}$ solar masses within a radius of 5 Mpc. In this case $GM/Rc^2 \sim 10^{-6}$, equivalent to a velocity shift of less than 1 km/s. Our own Milky Way has a mass of around $10^{12}$ solar masses within 100 kpc. This gives a gravitational redshift of about 100 m/s. These are completely negligible compared to cosmological ...

2

The gravitational red shift is only significant for black holes – where the coefficient may grow arbitrarily large in the vicinity of the horizon – and the neutron stars – where the frequency drops to something comparable to 50%. For all other celestial objects, the red shift is much smaller than one. And only planets and white dwarfs are objects for which ...

5

Tyco Brahe Observed Mars. And as the Mars is out side us, and rotates slower, it has an particular character that it even moves to "wrong direction" in the sky for a while. It must have been partially luck, that 5 of these observations is measures with enough accuracy this important point in orbit. (see link) Or maybe this was exactly the interesting ...

0

We are not seeing those stars as they are now. They may have disappeared in our now, for all we can know but earth will not become aware of that unless the appropriate light years have passed. This is due to the fixed velocity of light, which we use as a measure of cosmic distances. The sun for example is 8 light minutes away from earth. If some cosmic ...

0

If a star is, say, 4 light years away (eg alpha centauri), light from it takes 4 years to reach us. Stars are generally very bright, so they can be seen seen a long way away. That's all.

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Are there any exact data about Earth's orbit? No. There are always measurement errors. There are however very good estimates. The best estimates come from three competing organizations, the Jet Propulsion Laboratory (the Development Ephemeris models), the Russian Institute for Applied Astronomy (the Ephemerides of the Planets and Moon), and the IMCCE ...

28

I generally regard NASA as authoritative, and they report the orbital parameters on their Earth Fact Sheet. I note that they disagree with Wikipedia about the aphelion though they agree on the perhelion, semi-major axis and eccentricity: NASA Wikipedia Aphelion 152.10 151.93 Perhelion 147.09 147.095 Semi-major 149.60 ...

2

They couldn't carry sufficently accurate time from London with portable clocks. But they were able to use clocks to time measure the time between the sun crossing and the transit of stars the night before and after. The absolute transit time of stars can be trivially obtained if you know the site's longitude. If you are on land and have an observatory ...

-1

For short periods of time very accurate time could be kept by using pendulums.

1

Absent a small amount of distortion from the oblateness of the Earth, yes: it is a great circle. To generate the corresponding curve on a flat map, you have to use the map's projection rules to project the coordinates of the circle's circumference onto the map. That completely depends on the projection rules for the specific map you're using.

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