- The sun: provides heat and light needed to support life.
- Magnetic field: deflects the solar wind.
- Ozone layer: Acts as a barrier against ultraviolet light and other radiation.
- Greenhouse gases such as methane and carbon dioxide: retain warmth within the Earth.
- Oxygen and carbon dioxide: oxygen is needed for aerobic respiration. carbon dioxide is needed by photosynthesising organisms.
- Liquid water: has many useful properties such as good solubility properties.
The Big Bang theory is an effort to explain what happened at the very beginning of our universe. Discoveries in astronomy and physics have shown beyond a reasonable doubt that our universe did in fact have a beginning. Prior to that moment there was nothing; during and after that moment there was something: our universe. The big bang theory is an effort to explain what happened during and after that moment.
According to the standard theory, our universe sprang into existence as "singularity" around 13.7 billion years ago. What is a "singularity" and where does it come from? Well, to be honest, we don't know for sure. Singularities are zones which defy our current understanding of physics. They are thought to exist at the core of "black holes." Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is actually squished into infinite density (a mathematical concept which truly boggles the mind). These zones of infinite density are called "singularities." Our universe is thought to have begun as an infinitesimally small, infinitely hot, infinitely dense, something - a singularity. Where did it come from? We don't know. Why did it appear? We don't know.
After its initial appearance, it apparently inflated (the "Big Bang"), expanded and cooled, going from very, very small and very, very hot, to the size and temperature of our current universe. It continues to expand and cool to this day and we are inside of it: incredible creatures living on a unique planet, circling a beautiful star clustered together with several hundred billion other stars in a galaxy soaring through the cosmos, all of which is inside of an expanding universe that began as an infinitesimal singularity which appeared out of nowhere for reasons unknown. This is the Big Bang theory. Big Bang Theory - Common Misconceptions
There are many misconceptions surrounding the Big Bang theory. For example, we tend to imagine a giant explosion. Experts however say that there was no explosion; there was (and continues to be) an expansion. Rather than imagining a balloon popping and releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe.
Another misconception is that we tend to image the singularity as a little fireball appearing somewhere in space. According to the many experts however, space didn't exist prior to the Big Bang. Back in the late '60s and early '70s, when men first walked upon the moon, "three British astrophysicists, Steven Hawking, George Ellis, and Roger Penrose turned their attention to the Theory of Relativity and its implications regarding our notions of time. In 1968 and 1970, they published papers in which they extended Einstein's Theory of General Relativity to include measurements of time and space.1, 2 According to their calculations, time and space had a finite beginning that corresponded to the origin of matter and energy."3 The singularity didn't appear in space; rather, space began inside of the singularity. Prior to the singularity, nothing existed, not space, time, matter, or energy - nothing. So where and in what did the singularity appear if not in space? We don't know. We don't know where it came from, why it's here, or even where it is. All we really know is that we are inside of it and at one time it didn't exist and neither did we.
Big Bang Theory - Evidence for the Theory
What are the major evidences which support the Big Bang theory?
* First of all, we are reasonably certain that the universe had a beginning.
* Second, galaxies appear to be moving away from us at speeds proportional to their distance. This is called "Hubble's Law," named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted.
* Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Background radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery.
* Finally, the abundance of the "light elements" Hydrogen and Helium found in the observable universe are thought to support the Big Bang model of origins. Answer
It is difficult to "look back into time" and answer a question like this. There are several different ideas floating among astrophysicists. The idea of strings as a source for the Big Bang is one hypothesis, but is currently untestable. The lion's share of the ideas we have concerning the origin of the universe at time zero are all based in mathematical models. Multi-dimensional manifolds set out what happened the instant space and time began to be created here and spacetime unfolded into the universe we know today.
For all the tap dancing, posturing and brilliant calculations being put forth, the short answer in that no one has the faintest idea. Something does not suddenly appear from nothing. Either the universe has always been here or it had a beginning. If it had a beginning than a split second before this there had to be nothing. Some say it must have been God others, particularly scientists, avoid the question rather doggedly. What we do know is that something can not suddenly appear where there is nothing, at least not with our current knowledge.
I've become very religious as a result of studying the universe.
It could be anything that caused this singularity (and how it came to be), even beyond our wildest imagination (may be or may not be a God/Gods, could be something else that we don't even know yet for sure, no one will know unless maybe you time travel back to the origin or bend the laws of Physics and travel even before that and return back to present time safely in one piece or find a way to communicate with present time across time and space)
Stars glow for the same reason that the sun glows. They are gigantic balls of flaming gases. The reason the stars look so small, is the incredible distance between earth and the stars. (The light that we see from the stars can be millions of years old because it took that long for the light to travel this far!)
SatellitesSatellites orbit in outer space, not in the earth. They are sent to outer space where the gravitational pull of the earth pulls them around, just as the earth is pulled around the sun in a similar manner. The layer is the exosphere.
It greatly depends on what the satellite is for and who owns it how far up it orbits. Imaging satellites need to be close to the Earth, so they orbit about 130 miles up. Communications satellites are generally at 23,000 miles up. GPS satellites are up about 13,000 miles.
Venus itself doesn't generate much visible light. There may be some electrical activity in its atmosphere that generates some light, but it's minimal. The light we see from Venus is mostly reflected light from the sun.