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Gravity
Can anyone explain to me (in laymens terms) exactly what gravity is?
I dont want links to websites explaining it as Ive looked at those and cant make head nor tail of them. I just want a simple explanation why things fall down and not up.
Why does the earth keep the moon in orbit? Apparently the more matter the more gravity right? So why cant I orbit a frozen pea around a football? Come to that, why hasnt the moon fallen to earth yet?
Dont expect I'll wrap my head around it but humour me anyway.
I dont want links to websites explaining it as Ive looked at those and cant make head nor tail of them. I just want a simple explanation why things fall down and not up.
Why does the earth keep the moon in orbit? Apparently the more matter the more gravity right? So why cant I orbit a frozen pea around a football? Come to that, why hasnt the moon fallen to earth yet?
Dont expect I'll wrap my head around it but humour me anyway.
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"It's just happily timed so that we see only one side of it. "
It's not happily timed, Frog Nog and it is not a matter of coincidence. The moon exhibits "captured rotation" or is "tidally locked" with the earth (as is the planet Mercury with the Sun). This means it rotates on its axis in the same amount of time as it completes one orbit thus always presenting the same face towards the earth.
This has come about because the "tidal effect" that the earth has upon the moon has caused it to elongate in the direction of the earth (as the earth elongates daily as visible by the "tides" in the oceans). This has gradually slowed its rotation until it becomes captured in one place. This phenomenon is present with all bodies which rotate around a parent and effects both the parent and the satellite to a greater or lesser degree (depending on their relative masses). The tidal effect that the moon has upon the earth is slowing the earth's rate of rotation and eventually the earth will be tidally locked with the moon as well (if it exists for long enough).
It's not happily timed, Frog Nog and it is not a matter of coincidence. The moon exhibits "captured rotation" or is "tidally locked" with the earth (as is the planet Mercury with the Sun). This means it rotates on its axis in the same amount of time as it completes one orbit thus always presenting the same face towards the earth.
This has come about because the "tidal effect" that the earth has upon the moon has caused it to elongate in the direction of the earth (as the earth elongates daily as visible by the "tides" in the oceans). This has gradually slowed its rotation until it becomes captured in one place. This phenomenon is present with all bodies which rotate around a parent and effects both the parent and the satellite to a greater or lesser degree (depending on their relative masses). The tidal effect that the moon has upon the earth is slowing the earth's rate of rotation and eventually the earth will be tidally locked with the moon as well (if it exists for long enough).
If that apple had floated off into space we most likely wouldn't be having this discussion today.
Apart from gravity there would be no planets, stars or the heavier elements essential to life and the evolving of sentient beings capable of discussions of any kind. In fact, without hydrogen and gravity there never would have been anything of consequence to discuss.
Apart from gravity there would be no planets, stars or the heavier elements essential to life and the evolving of sentient beings capable of discussions of any kind. In fact, without hydrogen and gravity there never would have been anything of consequence to discuss.
Imagine a meter cubed of empty space, and think of 'space' and 'time' as forms of energy. For a ball to move through the space it temporarily takes up some of that space, which it then gives up as it leaves. It also requires time, which it does not give back. Some of the 'time' in that empty space has been used up, and because space and time are not interdependant, this has a reducing effect on the 'space'. This results in curvature of the space around it, just like many flat objects will bend if you shrink one side and not the other. That's my theory and it is a tad oversimplified but hopefully you get the gist of it.
As I understand it Bazile, a period of expansion occurred before what is scientifically considered to be the "big bang". (Not that there was any sound during that part, given there was nothing for sound waves to travel in.)
For our particular universe, space and time had to start with that initial expansion from the very small (infinitesimal possibly ?) But that does lead me to wonder at whether there is a sort of 'supertime' which encompasses the start of each universe and acts as a multiversal yardstick of some kind. After all we are also informed it should be possible for one universe to spawn another, so the young universe starts its time at some point along the timeline of the first.
I suspect I have a flawed notion of what time is though, and different frames of reference is going to explain it all :-)
If I am honest I'm not even sure time does flow, I'm rather attracted to the thought that everything that can be, always is, and we are just experiencing a path through it somehow, and that experiencing that seems like time passing.
Ah ... is ignorance bliss ?
For our particular universe, space and time had to start with that initial expansion from the very small (infinitesimal possibly ?) But that does lead me to wonder at whether there is a sort of 'supertime' which encompasses the start of each universe and acts as a multiversal yardstick of some kind. After all we are also informed it should be possible for one universe to spawn another, so the young universe starts its time at some point along the timeline of the first.
I suspect I have a flawed notion of what time is though, and different frames of reference is going to explain it all :-)
If I am honest I'm not even sure time does flow, I'm rather attracted to the thought that everything that can be, always is, and we are just experiencing a path through it somehow, and that experiencing that seems like time passing.
Ah ... is ignorance bliss ?
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