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Author Topic: What would happen if gravity were disabled for 30 seconds?  (Read 3724 times)

Offline thedoc

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@Hossbeast asked the Naked Scientists:
   
What would happen if gravity were disabled in the universe for 30 seconds?

What do you think?
« Last Edit: 18/07/2012 20:30:02 by _system »


 

Offline Bored chemist

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For a start we would all suddenly not be held on the earth and would fly off tangentially at somewhere between 0 and about 1000 miles per hour.
This would be one of the few circumstances where I'd want to be at the South pole at the moment (it's Winter there as I write this). The North pole would do too, but I think I'd need a boat.

The same thing would happen to buildings etc.
I'm not sure about the oceans, but I doubt it would be good for us.
 

Offline Geezer

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I'd be less worried about the turning off bit than the turning back on bit.
 

Offline elFisico

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The whole earth would suddenly expand and throw off everything, as the earths layers are no longer compressed by gravity. After 30 seconds everything would fall down again and be buried in a tremendous crash. Only maritime life would survive.

The earth would start to fly outward away from the sun. After 30 seconds it would reenter a new orbit that would be more elliptical.

The Sun would also expand, just like the earth, and crunch again after 30 seconds, producing massive solar flares that could blow off quite an amount of atmosphere if the earth would be hit directly.
 

Offline namaan

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And if the electromagnetic force were turned off for a microsecond? Instant plasma? ;)
 

Offline CliffordK

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For a start we would all suddenly not be held on the earth and would fly off tangentially at somewhere between 0 and about 1000 miles per hour.
You would, of course, continue rotating at the same speed as the planet and atmosphere.  In fact, if the distance of the arc increased, one might perceive that one was actually slowing down slightly relative to the earth.

In a half a minute, the earth revolves about:
((360/24)60)/2 = 0.125°

Hmmm  dig up some old math.
SOH CAH TOA   (cosine is equal to the adjacent over the hypotenuse)

So, COS(0.125°) = (Your elevation) / (Your new elevation)   {all relative to the axis of rotation}
(Your new elevation)=(Your elevation) / COS(0.125°)

So, if earth's radius at the equator is 6,378 km, you get your new elevation 30 seconds later being 6378.015 km.

So, your maximum elevation change would be about 15 meters.  A good sized jump.  But...  probably survivable.  Less as you approach the poles.

The Earth's crust would have significant stresses as deep pressure is relieved, as well as the same centrifugal force as the people standing on it.  You would no doubt have a global earthquake, as well as many volcanoes erupting.  The aftermath would not be pretty.

As mentioned above, if you were boating in the ocean, you might not even notice anything other than the weightless feeling during the original 30 seconds as the boat and ocean would all separate from the Earth at the same rate.  As gravity resumed, you would fall back down with the water.  As the ocean basin is refilled, there would be some snap...  perhaps as if you just went over the crest of a 15 meter wave, and then hit the trough, except without the wave and trough.

 

Offline Geezer

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You would, of course, continue rotating at the same speed as the planet and atmosphere. 


See, this is what comes of believing in centrifugal force :)

There would be no rotation of anything. Everything that was not "glued down" by the other forces would immediately start traveling in a straight line tangential to its prior orbit. That would probably include most of the Earth's crust, so there would be one heluva earthquake when it all reassembled.

As BC points out, you would not want to be anywhere near the equator. On second thoughts, you probably would want to be at the equator because there would not be a much point in surviving the initial event.

 

Offline CliffordK

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As I calculated, the deflection at the equator would be about 15 meters in 30 seconds. 

Both the stuff on the surface, as well as the surface itself would expand.  Looking at it from afar, there would only be the 15 meter blimp in an otherwise ball form of a planet.

Solids like rock and concrete would remain solid, but might crack due to the subsurface pressure and expansion.  Sand, and perhaps dirt would be come like quicksand, and as people fell back to the ground, they might find themselves partly buried in it.
 

Offline Geezer

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As I calculated, the deflection at the equator would be about 15 meters in 30 seconds.


The "glue" that holds most of the planet together is gravity. What do you think might happen when things like the Rockies, the Himalayas and the Alps accelerate at about 10 meters per second through 15 meters on the way back down?
 

Offline CliffordK

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As I calculated, the deflection at the equator would be about 15 meters in 30 seconds.
The "glue" that holds most of the planet together is gravity. What do you think might happen when things like the Rockies, the Himalayas and the Alps accelerate at about 10 meters per second through 15 meters on the way back down?
A "Rock" can be relatively stable in space with minimal pressure or gravity.  Just look at all the asteroids and small planetoids. 

Our moon might look like a giant dust cloud as all the regolith gets flung off, but the core, a few km deep would remain largely intact.  Likewise Mars has a much thicker crust, and might not experience as significant structural damage.

Earth's problem would be due to the thin, tectonically active crust, and relatively high pressure of the deeper regions created by the gravity.

Anyway, it is not the 9.8 m/s2 acceleration on the way back down that would worry me, but rather the deceleration from about 15 m/s or so down to zero in the last half second or so down at the bottom. 
 

Offline Geezer

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Re: What would happen if gravity were disabled for 30 seconds?
« Reply #10 on: 20/07/2012 06:00:52 »

Anyway, it is not the 9.8 m/s2 acceleration on the way back down that would worry me, but rather the deceleration from about 15 m/s or so down to zero in the last half second or so down at the bottom.
 

The various bits would not reassemble in their previous positions to produce a single big crunch like a movie run backwards. As soon a gravity was restored, things would become chaotic because of all the collisions and rotations. Might make an interesting computer simulation!
 

Offline elFisico

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Re: What would happen if gravity were disabled for 30 seconds?
« Reply #11 on: 20/07/2012 12:31:04 »
Don't forget: the earth core is under considerable pressure from the weight of the earth mantle. Imagine the earth beneath your feet as a spring that is compressed by the weight of the ground and the buildings. Now if the weight suddenly is removed, the spring will expand. With how much force will it expand? Well, initially with the same force it was compessed in the first place. This means that in the first few seconds you would feel nothing unusual, because you would be accelerated upwards with one g! I have no idea how long this would last but you can definitely say that mother earth would literally shrug us off her shoulders... ;-)
 

The Naked Scientists Forum

Re: What would happen if gravity were disabled for 30 seconds?
« Reply #11 on: 20/07/2012 12:31:04 »

 

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