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100,996 Questions

All about stars?

Stars are gigantic spheres of nucleosynthesis. They start off as hydrogen mainly but gradually fill up with heavier elements as they synthesise them.

Stars form from nebulae, vast clouds of hydrogen. Pockets of gas in the nebulae ball into spheres by gravity. Through tunnelling (relies on the Uncertainty Priciple of quantum theory), hydrogen nuclei fuse to form helium nuclei and this reaction gives of heat. Millions upon millions of these reactions heat up the star. Hydrogen is converted in this way (nucleosynthetically) into helium and helium into carbon.

A star is a 'delicate balance'. The heat from the core pushes outwards and the mass of the star tries to push the outer layers of the star inwards in collapse. Paradoxically, the larger a star the shorter is the time until it exhausts its nuclear 'fuel'. The nucleosynthetic reactions stop at iron. Energy must be addedto produce elements heavier than iron.

The largest stars (much larger than the Sun) explode as supernovae. The supernova energy is enough for the synthesis of the heavier elements, from iron to uranium.

With no nucleosynthetic energy continuing to be generated, the core collapses. Stars can shrink into white dwarves (where collapse is halted by electron degeneracy) or neutron stars (where collapse is halted by neutron degeneracy), or black holes, where collapse cannot be halted if the mass of the post-supernova core is above a certain limit - the Chandrasekhar limit.

There are a couple of videos on youtube about size and scale in the Universe. They start with the Moon and then show larger and larger and larger objects, from the Sun to Sirius and Aldebaran and the largest star so far known VY Canis Majoris.

The Sun is a star 150 million km from Earth and has a diameter of 1 390 000 km. The nearest star to the Sun is Proxima Centauri and is 4.3 light years from Earth.

Stars can be different colours, depending on their temperatures. Cool stars (from 3500 degrees Celsius) are redder in colour. The hottest stars are blue stars (up to 50 000 degrees Celsius). The Sun is 6000 degrees Celsius on the surface and 15 000 000 degrees Celsius at the centre and is classified as a type G yellow dwarf star.

Stars are classified by their size and colour on the Herzsprung-Russell Diagram.

Stars (in their billions) form huge groups (galaxies) thousands of light years in diameter. Galaxies have several shapes (spiral, barred spiral, elliptical and irregular).

Earth Sciences

What causes the seasons on Earth?

This is a more complex answer than most might think. Climate (long term weather) and climate change are a basic factor of 3 main things Obliquity (axial tilt) Precession Rotation (elliptical eccentricity,) They are also referred to as Milankovitch cycles named for the Serbian scientist that theorized and later proved his idea of cyclical climate changes with 26k 41k and 100k events which later were mathematically shown to coincide almost exactly with earths climate history. The Earth's rotation around its axis, and revolution around the Sun, evolve over time because gravitational interactions with other bodies in the solar system. a few cycles are dominant. Earths tilt and the wobble Seasons are not caused by its proximity to the sun, rather they are caused by its tilt (obliquity) and its wobble (precession) also causes chanhes in the magnetic declination of our poles. Think of an apple stab it with a pencil and tilt it 20 or so degrees, as the earth rotates amd revolves and wobbles the poles change place in angle to the sun, move your pencil from front to back

Where is the Aldorande star?

as they are star


What is Pisces' neighbor?

Cetus is the neighbour of Pisces.
Aquarius and Aries.

Artificial Satellites

What are the advantages of space satellites?

The advantages of space satellites are:

- Communication.

Satellites have greatly improved communication, not just nationally, but internationally. Nowadays a call can be placed from the United Kingdom to China in a matter of seconds.

Satellites also enable us to have mobile phones, without satellites, mobile phones are just a useless plastic square with numbers on it.

Satellites have also improved military communications (see below).

- Military and Security.

Military-controlled spy satellites are constantly scanning and keeping an eye on hostile territories around the globe, providing images, video and even voice recordings(!) to military command and intelligence agencies.

Satellites have also improved communication on the battlefield. Rather than using carrier pigeon services, wired phones and short-range wireless phones (which are not reliable), troops overseas now have satellite phones which can be used to contact friendlies, their headquarters, an allied aircraft carrier hundreds of miles away for air support and so on with rarely any complications.

(It is also theoretically possible to store missiles in space satellites and launch them at Earth. However such practices have been deemed illegal by the United Nations. An ordinary missile entering Earth from space will cause roughly the same amount of damage as a nuclear bomb, according to the Kinetic Bombardment Theory).

- Science and Discovery.

Satellites have the capability to carry scientific instruments through space, such as atmospheric readers, cameras and so on. These satellites roam space and beam images and scientific data back to Earth, enabling us to learn more about the planets in our solar system as well as about space itself.

- Navigation, Tracking and Mapping.

Satellites make it possible for us to have satellite navigation systems (better known as Global Positioning System, or GPS).

This enables us to have a device in our cars to tell us exactly where we need to go. They are also found in planes and ships to tell the pilots where they need to go and where they are.

Many new mobile phones have tracking devices in them, which is useful for parents who need to keep track of where their children are and to the police if a person goes missing.

The black boxes of aeroplanes (which believe it or not, are actually orange, not black) are embedded with a tracking device so it can be located after a plane crash, even if it ends up at the bottom of an ocean.

Tracking devices are also fitted to official, government and military vehicles for security reasons, such as preventing a bank van being hijacked or tracking a stolen military vehicle so jets can be sent in to destroy it.

Because of satellites, we now have access to a global map of the planet. We now know exactly what the planet looks like, providing us with the most accurate maps and atlases that have ever been produced before satellite mapping.

- Entertainment.

Yes, that's right, entertainment.

Satellites enable us to have satellite and digital television for everyday entertainment. Our daily and live television is beamed to us through satellites. Particularly if you live in the United Kingdom, where every television in the country is now digital.

Satellites also help digitally spread radio waves and even wireless internet.

The reason you can see friends on webcams from thousands of miles away, is mostly because of satellites feeding the webcam recording directly to your wireless router or internet modem.

- Weather, Meteorology, Geology and Climatology.

Satellites enable us to watch atmospheric changes in the Earth's atmosphere, enabling us to predict and forecast the weather.

They can also enable us to spot the early warning signs of a developing hurricane, for example, predict the path of the hurricane and organise evacuation of the areas that are going to be affected.

Satellites also enable us to scan the surface of the Earth for geological research and geological analysis. Particularly to predict when an active volcano is about to launch, to, again, organise evacuation.

Satellites also have the capability to forecast temperatures and gasses in our atmosphere. Which enables climatologists to update us about the progression of Global Warming on our planet.

- Earth's Shape and Earth's Distance.

Because of the shape of the Earth (sphere) and the vast size of the planet, it would normally be very difficult for ordinary wireless radio signals to reach one end of the globe to the other without receiving some form of interference. However, because of a system of satellites around the Earth these wireless signals, whether they be communication, television images and so on, can be bounced between the system of satellites and reach their required destination, without the normal interference that we would experience from wireless communication in the early 1900's.

There are of course some disadvantages to artificial satellites. They are very costly to launch and maintain. Abandoned satellites contribute to space junk making it dangerous for space shuttles to leave and enter the atmosphere. And so on.

However, the advantages of satellites far, far, outweigh the disadvantages.

Social Sciences
Apollo Moon Missions

How long will the footprints on the moon last?

The footprints on the moon will likely be there for as long as the moon is. Unlike Earth, there’s no liquid water, no volcanic activity, and no weather to speak of on the moon, so aside from the occasional meteorite and solar wind (which takes ages to have an effect), there’s nothing on the moon to mess with the footprints. They’re still there—along with spacecraft, scientific equipment, mementos, bags of human waste, and a lot more.

The Moon

How long exactly is one lunar month?

The moon completes one orbital revolution around the earth every 27.32 days,

and displays a complete cycle of "phases" every 29.53 days. (Those are both

rounded numbers.)

Planetary Science

Dusty and gaseous material orbiting a star is called what?

star dust


How are stars made?

It takes millions of years for free floating diatomic molecules of hydrogen gas in space to congregate in sufficient quantity to produce a protostar (the first stage). The collapse of the gas usually requires some event, such as a collision between gaseous nebula which tend to be inelastic, or the shockwave from a supernova, or the wake of a black hole. Any of these events can nudge gravity to coalesce the gas into a "brown dwarf."

When a brown dwarf has gained enough mass to emit its own light and heat via gravitational collapse, it becomes known as a "protostar." Protostars require 100,000 to a few million years to gain sufficient mass, core heat and pressure, to commence nuclear fusion, even though they can appear as bright as a "true" star. The most common true star is known as a T-Tauri star.

Nuclear fusion occurs as protons of hydrogen combine with neutrons to form helium nuclei (alpha particles). This process takes place in the core of the star, where the temperature is in the millions of degrees and the pressure is extremely high. Nuclear ignition is the point at which one may say a star is "born," and the resulting solar wind slows or halts the infalling nebular gas. Any remaining gas the star pulls into itself would come primarily from what is known as a protoplanetary accretion disk, usually forming parallel to the star's rotational axis.

Helium comes from the word helios, meaning "sun." The helium nucleus is lighter than its constituent parts--the two protons and neutrons of which it is formed. This difference is known as the "mass defect," and is equivalent to the energy liberated in the fusion process. So in its gestational state a protostar shines via gravitational collapse, until the core pressure and temperature is great enough for nuclear fusion, at which point the star shines by the nuclear fusion reaction.

Larger stars are less common, but can form in less time, such as by the collision of numerous protostars.
they are created with hot gasses from the nebula or really hot or exploded stars I believe
A star is born when gas and clouds of dust is forced/pushed together and forms a beautiful star.
they are created with hot gasses from the nebula or really hot or exploded stars I believe
A star is born when gas and clouds of dust is forced/pushed together and forms a beautiful star.


What do satellites do?

"Natural Satellites"

Circle around larger, more massive objects (the Earth is technically a satellite of the Sun, and the Moon is a natural satellite of the Earth).

Artificial Satellites

Satellites orbit the Earth to provide links between places on the planet (TV, phone, internet) and to study the Earth and space. They provide information to the military, to weather forecasting, to geologists, and more. The orbiting space telescopes examine other planets and stars.

Satellites orbit in a variety of directions, but most circle west-tp-east at various heights above the Earth's atmosphere. Geostationary satellites seem to stay in one place, but they only in very high orbits. Geosynchronous satellites orbit exactly once a day, so they stay over the same location on the ground.

(see related question)

  • Communications - This includes television, phones (cellular as well as others), and internet. Satellite television providers, for example, broadcast a one-way signal with audio and video programming to their customers. This is of great use for customers who are in areas too remote to use cable or other wired means, or for mobile users in vehicles and boats. Customers simply tune their in-home receivers to the sub-channel they desire and watch digital programming direct from space.
  • Earth Observation and Surveillance - Military reconnaissance satellites and civilian mapping satellites use high-resolution cameras to take photos of the earth's surface for mapping or intelligence purposes. Further, these cameras are not limited to the visible light spectrum, and so some are dedicated to infrared or ultraviolet sensing, which are used by environmental researchers and agriculturists; this can help them determine the temperature, quantity of foliage, chemical composition of the air in different locales, changing height of the polar ice caps, shoreline erosion, or mapping of warm and cold ocean currents. Other uses include popular web applications, surveying, real-time weather observation, and natural resource detection and management.
  • Navigation - Global Positioning System (GPS) satellites function by emitting a specific signal pattern. Variations in this signal can be detected by GPS receivers to determine a GPS user's location relative to the satellite by using a principle called the Doppler Effect. The Doppler effect is the apparent compression or decompression of signals that occurs when the signal source is in motion, relative to a listener, for example, why a train whistle changes pitch when it approaches or departs from the listener. By calculating the amount of compression in the signals for multiple satellites, a GPS receiver can pinpoint the user's location.

Because of the large distance between satellites, distances from Earth to distant stars and planets can be determined more accurately (greater parallax). Also, on board cameras can better view objects on Earth in 3 dimensions.

There are many purposes for placing satellites in orbit. First and foremost, communications satellites exploit their great distance from the earth to transmit their signals the greatest distance possible. Many modes of communication, chief among them microwave, travel by 'line of sight,' meaning that one must be in a direct, unobstructed sight line in order to receive a signal. The earliest communications satellite received and relayed microwave communications from large ground stations. Today, we have technology to communicate directly through such satellites using satellite phones. Satellite communication permits direct communication beyond the horizon that might not otherwise be possible with conventional VHF (Very High Frequency) communication (ie, radio).

Still other satellites are used for assorted experimental purposes, exploiting the lack of vibration, low temperature and low gravity of space as an ideal location for extremely sensitive instruments, such as the Hubble Space telescope and similar projects, which are able to see much deeper and more clearly into the cosmos without having to look through the earth's atmosphere first.

A special category of satellite is one that is manned, such as the International Space Station (ISS), and they are used for exploration and research into the effects of long-term low gravity, international cooperation and the promotion of peace, among other purposes.

Communication satellites can be used to send telephone messages or TV pictures. A satellite can be used for working out what the weather will be like in a few days. It has a sensor which send a television call to earth telling us what's going to happen. They can also be used for spying and navigation and they can spot forest fires and water pollution.
1st letter is S and ends with E!
it transmits radio/ televideo/etc. waves
It helps us by like if we atrapped some where and u have afone on u u can call 911 or someone who willhelp u
They are used for exploring different planets in our solar system, transmitting radio, telephone, and television signals, and to tell what the weather is going to be like.
many sencitest send artifical satalites some revolving around the earth. it is used dish antena
The primary uses for an artificial satellite, given our current technology, are:

  • Communication (television and cell phone satellites)
  • Observation (the Hubble Space Telescope, weather satellites, )
  • Location (the GPS system)
  • Habitation (Skylab, Mir, the International Space Station)

As our technology continues to expand, it's likely that uses for artificial satellites will as well. For example, a military satellite might provide a way to defend specific nations, or even the Earth as a whole (from a meteor strike, for example). Or, as seen on sci-fi TV shows, a space dock could allow the repair and refueling of space vehicles, without the need to return to our planet's surface. There could eventually be space hotels, low- and zero-gravity tourist attractions, zero-gee factories, controlled-gravity hospitals... The list is bounded only by our imagination, and economic considerations.

Meteorology and Weather

Does spring start a day early in 2020?

In the United States, the vernal equinox, which signifies the start of astronomical spring in the northern hemisphere, actually happens on March 19, 20, or 21 each year. We haven’t had a March 19 equinox since 1896, and we won’t have a March 21 equinox until 2101.

I say it marks the beginning of astronomical spring because meteorological spring (based on weather patterns) starts March 1.

Astronomical spring is a little harder to explain. The Earth’s axis is always tilted at about 23 degrees, meaning that depending on where it is in its orbit, one hemisphere or the other is closer to the sun. The equinoxes (the vernal equinox in March and the autumnal equinox in September) mark the points in the orbit where neither hemisphere is tilted toward nor away from the sun, meaning day and night are nearly equal.

Planetary Science

What does the earth's gravitational attraction prevent gases from doing?

The Earth's gravitational attraction prevents gasses from escaping into outer space.

The Moon
Planet Earth

The earth spins on its axis yes or no?


The Sun

Why can't we see the Sun at Night?

Because Earth is turning. It's only ever night time on one side of the Earth, the side not facing the sun.

Space Travel and Exploration
Planetary Science

What are uses of constellation?

Constellations are used as a way of mapping surrounding space so that's its easier for us to find certain planets/stars alot easier. Also in history these constellations have being used for astrology which is suposerly a way of reading ones future, hope this helps

School Subjects
Red Shift

Can there be purple shift aswell as blue shift and red shift?

Redshift and blueshift refer to a change in frequency of light we receive from distant objects (stars, galaxies, etc.) The light can turn different colors, and purple is one of them. However, no matter what the color the light changes to, the technical term is always "redshift" if the frequency of the light decreases (normally indicating that the object is moving away from us), and "blueshift" if it increases (normally indicating that the object is moving towards us).

Blue shift and purple shift would mean the same thing because the spectrum is one-dimensional. It's like if you are in Boston, a shift towards Chicago is the same as a shift towards San Francisco.

Obviously, a purple shift is a super blue shift.

Earth Sciences

What causes the Earths seasons?

God made earth and all! It seems we maybe over effecting our earth and possibly causing our own changes to it.

All that do Believe in God have lives filled with LOVE!

Atheists cannot feel anymore than each of their own LUST for only each of their own wants!

Rhyming Words

What rhymes with black empty space?

slap in d face (sorry)

back in me face

clack-wimp tea base Similac tea base.

slack in d grace

back in d place

back in the race

the gak imp be traced

Shaq 'em, Tea Gaze

stack them delaze

crack them

crack black jack whack stack nack lack galacticky grace galacticky maze? phase

empty wimpty pimpty limpdy glib

sickle cell anemia.

plaque EMPTY? pimpty...

block um D? SEIS!


back impish pace

blasphemy race

grass for me trace

daquiri base

pace paste? grace mace chase

Planetary Science

What are the four orbital shapes?

We can come up with only three:

-- hyperbolic

-- parabolic

-- elliptical (including circular, a special case of elliptical)

Circles, ellipses, parabolas and hyperbolas are all conic sections, the intersection of a plane with a right-circular cone.

Orbitals in quantum chemistry have shapes that are spheres for s-orbitals, dumbbells for p-orbitals, and different types of d-orbital are either pairs of crossed dumbbells, or a dumbbell with a central collar. f-orbitals have yet more complex shapes, but they are not usually considered in textbooks.

In physics, p and d orbitals have rather different shapes. A s-orbital is still a sphere, but p-orbitals are either dumbbells or tyres, and d-orbitals are collared dumbbells, double (point to point) cones, or tyres.


What does the moon give us?

UpdateThe moon also provides up with some light at night-time because the sun reflects off the moon. If there was no moon then it would be very difficult to see at night without the assistance of fire or electricity. AnswerThe moon plays a very important role to life on Earth as we know it. Due to it's size, it keeps the Earth stable and does not tumble. Mercury, Venus, and Mars tumble because Mercury & Venus have no moon, and Mars' two moons are not large enough to affect it. The Moon also controls the tides of our oceans. We have two high and low tides each day. The Moon can also give us a show as it's proportional in size to the Sun and gives us Solar Eclipses. It also can provide Lunar eclipses.

Tides plays a large part in driving oceanic streams and weather patterns. Thanks to the moon, we have a large pump aerating the oceans and thanks to this constant churning we have a much greater chance of surviving climate changes.

Rock Music
The Moon
Moons and Natural Satellites

How cold is nighttime on the Moon?


The temperature of the Moon's night is -173.3 degrees C. (-280 degrees Fahrenheit).

The Solar System
The Sun

What is the importance of the sun in the solar system?

Clearly, we (Earth) can't live without the Sun. It gives us energy/ electricity and warmth. Plants need the Sun for photosynthesis, we need it as light during the day. The Sun plays a major role in our lives.
The importance of sun in our solar system is that if we don't have the sun then there will be no life on Earth since it is too cold for life to grow, and the Earth will be a frozen chunk of ice.

The Moon

Why is life not possible on moon?

"Life as we know it" is not possible on the Moon because the Moon has no atmosphere. When people go to live on the Moon, we will need to provide pressurized habitats in which we can live without a pressure suit. We will probably also have to live underground, since the lack of atmosphere also means that there is no protection from the damaging UV radiation from the Sun.

The Moon also lacks a strong magnetosphere to protect life from bombardment by charged particles.


The Lunar inhabitants are likely to refer to themselves as living "IN the Moon" rather than "ON the Moon" because the habitations are likely to be underground rather than on the surface.

Planet Earth
Speed of Light
The Solar System

How much time would taken by sun rays to get to the sun from the earth?

8.3 seconds


What are facts about a high mass star?

Mainly, a high mass star has a very short lifetime, because it uses its fuel in a much more wasteful manner: due to its higher mass, it will get much hotter, and the fusion will occur much faster.


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