how do scientec know that the world formed by the big bang?

Answer 1

The short answer is--they don't.

What amuses me to no end is that it takes just as much faith to accept many scientific theories as it does to accept religious ones.

Answer 2

Things seemed a lot simpler back in 1965 when two astronomers at Bell Labs in Holmdel, N.J., provided a resounding confirmation of the Big Bang theory, at the time merely one of several ideas floating around on how the cosmos began. The discovery happened purely by accident: Arno Penzias and Robert Wilson were trying to get an annoying hiss out of a communications antenna, and after ruling out every other explanation—including the residue of bird droppings—they decided the hiss was coming from outer space.

Unbeknownst to the duo, physicists at nearby Princeton University were about to turn their own antenna on the heavens to look for that same signal. Astronomers had known since the 1920s that the galaxies were flying apart. But theorists had belatedly realized a key implication: the whole cosmos must at one point have been much smaller and hotter.

Penzias and Wilson later won the Nobel Prize for the accidental discovery of this radio hiss from the dawn of time.

The discovery of the cosmic-microwave background radiation convinced scientists that the universe really had sprung from an initial Big Bang some 15 billion years ago.

Most astronomers would say that the debate is now over:

Three excellent reasons exist for believing in the big-bang theory.

First, and most obvious, the universe is expanding.

Second, the theory predicts that 25 percent of the total mass of the universe should be the helium that formed during the first few minutes, an amount that agrees with observations.

Finally, and most convincing, is the presence of the cosmic background radiation. The big-bang theory predicted this remnant radiation, which now glows at a temperature just 3 degrees above absolute zero, well before radio astronomers chanced upon it.

Answer 3

Overall, there is a universal red shift (see COBE satellite) when the universe is viewed from the earth. This indicates that the universe it almost all moving away from us. There is the "hubble constant," derived from observation, which predicts how fast an object moves away from us for a certain distance away from the earth (how far back we look in time). The farther out you look, the faster things are moving away.Overall, everything is moving away from everything else, so naturally, in the past, everything was closer to each other. Furthermore, the further you look out (the maximum is some 14 billion years back in time) the newer the stars you will see. The "big bang" is part speculation, like most of astronomy, and it is widely misunderstood, but it is the best theory we have.

Answer 4

Some scientist (forgot his name!) discovered that the universe was expanding, so they figured that it must have started at some central point, and because it's expanding they thought that there must have been a big explosion at the beginning of time.

They do say that one day it will all come together again, then explode again but I'm not sure why they say that. I mean, if we discovered the fact that the universe is all coming together (say in millions of years time) we wouldn't have thought of a Big Bang theory because it would be getting smaller, not bigger!

Answer 5

One way that scientists know that some sort of "Big Bang" happened is that they can actually hear it.
After an explosion of that magnitude, shock waves are emitted and resonate for long periods of time and over long distances.
Scientists have measured a residual hum which they believe is
a hum from the original big bang still resonating.

Answer 6

They don't. It's just informed speculation, based on the laws of physics, the current speed at which galaxies are spreading apart, and what we see of the universe (which is really the universe that existed years/millions/ billions of years ago)

Answer 7

The 'world' didn't!

The universe did.

Answer 8

They don't KNOW it, it's just the most logical theory they have. It certainly makes more sense than a magical fairy waving his magic wand and creating the whole Universe in 7 days, doesn't it?

Answer 9

Not a scientific fact. They do not know, just a speculative guess. Do more searching, don't accept every theory as fact.

Answer 10

first off, they are referring to the entire universe, not just the world.

Secondly, this is a widely held theory based on much mathematical information