Astrophysics

We use Earth as a reference. 'A planet not composed mostly of silicate rocks' would likely be a gas planet, although one could imagine a planet consisting of mostly water ... a so-called "water world". Within our sloar system, we call these gas planets "Gas Giants", because in reference to earth they are all very large. The 4 Gas Giants in our solar system are Jupiter, Saturn, Uranus, and Neptune. Sometimes Uranus and Neptune are referred to as "Ice Giants" based on the chemistry of their outer atmospheres and their interior cores. See this link for some info on orbital periods, masses, densities, etc: http://www.solstation.com/stars/jovians.htm

Depending on the mass of whatever is left over of a star, it can turn into a white dwarf, a neutron star, or - in the case of the most massive stars - a black hole.

No, Saturn is not the only planet with rings. Jupiter and Uranus also have rings, it is just easier to see the rings on Saturn.

Australopithecus is a genus of early hominins that lived in Africa from around 4 to 2 million years ago. They are known for being bipedal (walking on two legs) and having a mix of ape-like and human-like characteristics, making them an important part of our evolutionary history. Famous species within this genus include Australopithecus afarensis, represented by the fossil "Lucy."

Jupiter. Jupiter has a mass of 1.8986×1027 kg, 317.83 times the mass of earth.

Jupiter is massive enough to be used as a reference mass for describing the mass of the other outer planets of our solar system.

According to the Wikipedia article, there are different types of Cepheids; really, I think that each type should be investigated separately.For example, classical Cepheids have 4-20 times the mass of our Sun, and such stars are rare - 85-90% of all stars are less massive than our Sun. And not all such stars will automatically be Cepheids at any specific period of time.

I am not sure about the other types of Cepheids - whether they really ARE rare, or if they are, why. In fact, it would seem that nobody knows for sure - according to Wikipedia, article "Type II Cepheid", "The physical properties of all the type II Cepheid variables are very poorly known."

In the case of a star (that is not actually going nova or supernova) they are balanced.

Yes, light is the only thing that can escape a black hole's gravitational pull. Nothing with mass, including matter and other forms of energy, can escape a black hole once it crosses its event horizon.

A black hole does not contain air as we know it. It is a region of spacetime with such strong gravitational effects that nothing, not even light, can escape from it. It is a highly compact, dense object formed when a massive star collapses in on itself.

A stellar mass black hole is formed when a massive star undergoes a supernova explosion at the end of its life cycle. If the core of the star is massive enough, it collapses under its own gravity and forms a black hole. These black holes typically have a mass between 3-20 times that of the Sun.

Usually the Moon (Earth's) is said to orbit Earth, although the latter is sometimes not regarded as a celestial body per se. There are also arguments based on the nature of the lunar orbit that it is actually co-orbiting the Sun along with the Earth, that Earth and our moon simply share an orbit.

The strength of the gravitational field depends on the mass, and on the distance. Since in black holes, the mass is concentrated in a very small region of space, it is possible to get very close, and still have all the mass on one side.Please note that at a given distance, say 100 million kilometers, a black hole with a certain mass has exactly the same gravitational field as a star of the same mass, at the same distance.

The term "day" applies to the duration of one rotation of the planet on its own axis. The Earth rotates on its axis once every 24 hours. The rotational motion is attributed to the intrinsic angular momentum of the body, acquired during its formation.

By contrast, a year would be the duration of one orbit of the planet around the Sun.

In college chem when titrating we were told to take 10 drops per mL, thus there would be 10,000 drops per liter. Other texts cite 10, 15, 20, even up to 60 drops per milliliter when dealing with intravenous drip calculations in medicine - so, depending on what source you use, that could mean up to sixty thousand drops in that bottle.

When used to describe our sun it is a name, which makes it a proper noun and therefore should be capitalized. When used in reference to the many bright lights we see at night it is simply a noun and therefore not capitalized.

No. A black hole is not a tunnel. It is the remains of an object that has completely collapsed under the force of gravity. Within a certain distance, nothing, not even light can escape. That threshold is known as the event horizon. In a non-rotating black hole the event horizon appears as a simple, completely black sphere. In a rotating black hole the event horizon is slightly oblate; a bit wider at the "equator" than at the "poles." The background around the event horizon will appear highly distorted as light passing near it is bent by the strong gravity.

Black holes are super-heavy stars which exploded, then collapsed in on themselves to become so dense their gravitational force can collapse matter, and pulls in anything that gets too close. Once a hypothetical body, it is now generally agreed that there are many, many blackholes in the universe, I think something like 30 million in just our galaxy.

Wormholes are hypothetical (for now, haha) phenomena - basically according to relativity the universe has no beginning or end, it is closed in on itself, which means that if you were to go in a straight line in outer space very fast for a very long time, say the speed of light for 30 billion years, you would find yourself in the same spot you started at, because the universe curves in on itself. It is circular, not linear.

So while this is very hard to picture if you're not a quantum physicist, if the universe is a circle, like an apple, hypothetically there might be a way to "tunnel" from one side of the universe to the other side, or (maybe) to any point, like a worm tunneling through an apple.

Complicated stuff.

Time Tunnels are associated with science fiction stories but not science, they are tunnels inspired by the concept of the wormhole and allow things to pass from one time to another.

If you want to understand more about relativity, I recommend the small paperback The Universe and Dr. Einstein. No math or expertise required, and Einstein endorsed it himself. :)

A black hole is powered by gravity so great that nothing can escape it.

Well you could try google images, but other wise there is no actual real footage or pictures of any black hole because the gravitational pull of a black hole is so powerful that it can even suck up light!

Unanswered questions concerning the Big Bang:

1) What drove the initial expansion of space?

2) Why did inflation stop?

3) What existed before the start of expansion? And does the word "before" have any meaning if there is no time?

Back holes don't emit radiation*. Photography works by reacting a chemical-coated strip by the light emitted by an object, or photochemically noticing the light. Thus, direct photography of black holes is practically impossible.

No, all a black dwarf is is a white dwarf that has cooled, it's mostly carbon and oxygen and nitrogen. A black hole forms when the gravity of a collapsing star is able to overcome all opposing forces.

Kinetic theory in chemistry describes the relationship between temperature, volume, and pressure; if you increase temperature, the pressure or volume will increase, if you decrease volume or increase pressure, temperature will increase. The theory examines the nature of an elastic gas with atoms or molecules moving around within a container colliding with each other and with the walls of the container; temperature is a measure of the collective average random kinetic energy, expressed both in mass and speed (rotation, translation, and vibration). It describes that as you compress the substance (decrease the volume), the density of its component molecules increases and the frequency with which they collide with the walls increases, hence the temperature (and/or pressure) goes up.

No light comes from a black hole.

There are occasional bursts of X-rays from the accretion disk AROUND the black hole, we believe, caused as dust and gas are accelerated by gravity to nearly the speed of light. That's what we call the "event horizon"; the point at which falling mass is accelerated to lightspeed. Since the math for matter traveling at lightspeed doesn't make any sense, we say "We CAN'T know what happens".

Eventually, many years from now, we'll be able to examine the area around a black hole, but there are none nearby. EVERYTHING we think we know about black holes is based on mathematical theory, and it is highly probable that much of what we think we know is wrong.

Unfortunately, we don't know which parts.