News1 min ago
the big bang
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is it true that at the time of the big bang everything in the universe,all matter and energy was condensed into a tiny ball the size of a grapefruit?i have heard this analogy given before and canot get my head around it.
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Oh yes - and you don't know the half of it yet.
All physical space and time was in that too - and it was waaaay smaller than a grapefruit!
Don't fret - nobody can really visualise it - we all live "in" space and time. You can't picture yourself outside of it any more than a goldfish can imagine what it's like to be a bird.
All physical space and time was in that too - and it was waaaay smaller than a grapefruit!
Don't fret - nobody can really visualise it - we all live "in" space and time. You can't picture yourself outside of it any more than a goldfish can imagine what it's like to be a bird.
It comes from this realisation:
If you look into the sky, with good enough telescopes, you'll see that stuff is expanding -- stars and galaxies are moving away from each other.
But this is assuming that time is moving on too. So if you start moving backwards in time, you'll rewind the movement of the stars and galaxies, just like you'd see if you rewind a video.
So, you can imagine that if you keep rewinding, and everything is moving towards everything else, eventually you'll come to a point where everything is, and you can't rewind any more (the beginning of the tape, so to speak).
Next is time -- why do we think that this is the beginning of time? Well, it's all down to gravity. Everything that stuff is made of has some gravity. So if you have more stuff, you have more gravity. The Sun has more gravity than the Earth, because there's a lot more of it.
It was found (and is predicted quite accurately by Einstein's General Relativity), that a clock on the highest mountain runs a little faster than a clock at sea level. So, if you move away from a gravitational source, time runs faster. Kinda weird, but true.
But this also means that if you have a clock at somewhere with a lot of gravity, time will run really slow. So, at the time of the big bang, all the matter of the universe was there at the same point, so a clock at that point would have slowed enough to have stopped.
If you look into the sky, with good enough telescopes, you'll see that stuff is expanding -- stars and galaxies are moving away from each other.
But this is assuming that time is moving on too. So if you start moving backwards in time, you'll rewind the movement of the stars and galaxies, just like you'd see if you rewind a video.
So, you can imagine that if you keep rewinding, and everything is moving towards everything else, eventually you'll come to a point where everything is, and you can't rewind any more (the beginning of the tape, so to speak).
Next is time -- why do we think that this is the beginning of time? Well, it's all down to gravity. Everything that stuff is made of has some gravity. So if you have more stuff, you have more gravity. The Sun has more gravity than the Earth, because there's a lot more of it.
It was found (and is predicted quite accurately by Einstein's General Relativity), that a clock on the highest mountain runs a little faster than a clock at sea level. So, if you move away from a gravitational source, time runs faster. Kinda weird, but true.
But this also means that if you have a clock at somewhere with a lot of gravity, time will run really slow. So, at the time of the big bang, all the matter of the universe was there at the same point, so a clock at that point would have slowed enough to have stopped.
To be totally accurate (as accurate as a layman can be discussing quantum physics) the word picture of everything being in an extremely small area at the instant of the Big Bang is a misunderstanding of the event, in my opinion. The problem is, quantum modeling can only describe the event from the estimated onset of the small dimension, when, in reality the "time" (or distance) before that calculated dimension can only be guessed at.
Planck Time is a time whose length (duration?) is so small that only a few physicists in the world can discuss it with any understanding. But, that's the time at which our descriptions of the Big Bang begin. Prior to Planck Time (or distance, since Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to the Planck length (1.6 x 10-35 meters).. This is the �quantum of time�, the smallest measurement of time that has any meaning, and is equal to 10-43 seconds) quantum mechanics and it associated calculations can only guess at what was happening. It seems the logical conclusion would be that prior to Planck Time (I know... there is is no prior, but for the sake of discussion) there was nothing. Zip, zilch, nada... nothing. And... that's what make the event even more remarkable, if that's possible...
Planck Time is a time whose length (duration?) is so small that only a few physicists in the world can discuss it with any understanding. But, that's the time at which our descriptions of the Big Bang begin. Prior to Planck Time (or distance, since Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to the Planck length (1.6 x 10-35 meters).. This is the �quantum of time�, the smallest measurement of time that has any meaning, and is equal to 10-43 seconds) quantum mechanics and it associated calculations can only guess at what was happening. It seems the logical conclusion would be that prior to Planck Time (I know... there is is no prior, but for the sake of discussion) there was nothing. Zip, zilch, nada... nothing. And... that's what make the event even more remarkable, if that's possible...
Oh I thought Clanad wouldn't be long before chipping in with the Plank time.
This time is the shortest period of time that is meaningful - talking of times earlier than that is not a limitation of our knowledge but a reflection of how time actually is.
talking of times before it makes as much sense as talking about half an atom.
This time is the shortest period of time that is meaningful - talking of times earlier than that is not a limitation of our knowledge but a reflection of how time actually is.
talking of times before it makes as much sense as talking about half an atom.
Respectfully, jake... there is some time (or, whatever you wish to call the interval) before the instant that Planck (don't forget the c, Max wouldn't like it) time is measured. Intuitevly... just because we can't measure it doesn't infer that the event began at Planck Time, does it? Your contrast between time before and half and atom is meaningless, but only as a contrasting statement... If you're correct, then all the suppositions concerning the string theory, bosons and fermions are in vain... no?
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