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suntrack2
2006-Aug-23, 12:09 PM
this is for suppose: we know the earth's own gravity is much big, but in case the gravity of the earth gets downfall, so what will be the scinario on earth?

will such low gravity useful for satelite launchers to launch the satelite in the space?

how much time will take 'that apple falling' on the earth in such conditions?

or man himself will become able to fly in the low gravity? without wings!

this question is purely imaginative.

sunil

sundaju
2006-Aug-23, 03:57 PM
It will be utter chaos in earth...

Whatever activities we are seeing, doing, observing on Earth, they all have an underpinning either directly or indirectly on Earth's gravity.

There is every chance that the earth's atmosphere may go away slowly..

All living things would be confused when they try to do any routine activity, as the known way of doing these things will never work in that scenario...

Among all living beings, only the astronauts/cosmonauts who had been trained on space simulator will make some sense of the crazy things happening..

sundaju
2006-Aug-23, 04:54 PM
To add to that...

NASA will be making a lot of quick bucks... in training people on spacewalk to cope up with the loss of gravity..

Aeroplanes taking off and landing would be crazy to watch...

neilzero
2006-Aug-23, 09:45 PM
I think humans and other creatures would adapt to 1/4 g quite quickly. Most mechanical devices would need some minor adjustments for optimum operation. Vehicles would have a tendecy to become airbourne as they reached the top of a hill and started down. Neil

Ken G
2006-Aug-24, 10:47 AM
The simplest scaling is that the time it takes to fall a given distance scales like the inverse square root of the gravity, so everything would take twice as long to fall. As far as other things are concerned, just look at footage on the Moon and you'll get the idea. Note also that if the gravity changed from what it is now to 1/4 of what it is now, the relaxation of the crust of the Earth would destroy everything on its surface.

astromark
2006-Aug-24, 11:03 AM
Yes, Ken is on to it here. The reduction of Earths gravity would possibly destroy the calm we know so well. Seismic and volcanic activity would most probably destroy our environment just as the last remnants of our atmosphere drifted of into space.
Fortunately none of this can ever actually happen. The laws of physics of this universe have set the amount of gravity this much matter must have and, it does and will always be. One G.

suntrack2
2006-Aug-24, 01:37 PM
thanks for your comments above, well: how the heavy ship will work in the sea waters?

sunil

ToSeek
2006-Aug-24, 02:25 PM
thanks for your comments above, well: how the heavy ship will work in the sea waters?

sunil

The ships would probably be skimming right along the surface, though I wonder if with the reduced gravity the water pressure in the oceans would be reduced, thus expanding the water and drowning us all.

phunk
2006-Aug-24, 02:28 PM
Nah, water doesn't compress, reducing gravity wouldn't make it expand.

suntrack2
2006-Aug-24, 02:31 PM
thanks Toseek, you are quite true, : well as far as tsunami is concern how it will work in the low pressure in the sea, no tsunami will apear? or it will creat no destruction. and whether swimming will be difficult for fishes into the water?

sunil

agingjb
2006-Aug-24, 03:04 PM
Why would objects float any higher? Weights would remain in proportion to mass, so (relative) displacements wouldn't change, would they?

If the change happened suddenly (how?) then everything in orbit would escape the Earth, but not the Sun. The moon would go into a solar orbit, rather near that of the Earth, and unless it managed to get into something stable (L4, L5, or an exchange co-orbital) would have some probability of eventual impact. I think.

Kaptain K
2006-Aug-24, 03:20 PM
The ships would probably be skimming right along the surface..
I don't think it would change a thing. A ship displaces its weight of water. The ship weighs 1/4th as much, but the water weighs 1/4th as much per unit volume. The ship will displace exactly the same volume of water.

Ken G
2006-Aug-24, 03:21 PM
Why would objects float any higher? Weights would remain in proportion to mass, so (relative) displacements wouldn't change, would they?
Quite correct, ships would float in an unaltered manner. A nice tricky question for an exam, I should think!


The moon would go into a solar orbit, rather near that of the Earth, and unless it managed to get into something stable (L4, L5, or an exchange co-orbital) would have some probability of eventual impact.
Yes, that sounds right, though it might take a long time. If anyone survived the earthquakes, volanoes, and tsunamis, the Moon would probably be the least of their concerns!

Bob
2006-Aug-24, 03:46 PM
Atmospheric air pressure would be drastically reduced. Sea level air pressure would be comparable to present conditions at the top of the highest mountains. Few things in the biosphere would survive such an environment.

Boxes
2006-Aug-24, 05:16 PM
I don't think it would change a thing. A ship displaces its weight of water. The ship weighs 1/4th as much, but the water weighs 1/4th as much per unit volume. The ship will displace exactly the same volume of water.

I think you're right for large ocean going vessels with displacement hulls, which is what was asked about.

Just a guess, but I would think vessels with planing hulls, like most sport and leisure craft, would fly on top of the water using less horsepower than before. You might have to bring some O2 to keep the engine running though. Comments?

ToSeek
2006-Aug-24, 05:22 PM
I don't think it would change a thing. A ship displaces its weight of water. The ship weighs 1/4th as much, but the water weighs 1/4th as much per unit volume. The ship will displace exactly the same volume of water.

You're right, and I'm wrong. But we'd still have to live on those ships because the Earth would be covered with water.

pghnative
2006-Aug-24, 05:36 PM
The moon would go into a solar orbit
Yes, that sounds right, though it might take a long time. Well, the moon would instantaneously be in a much more eccentric orbit, right? It may only take a few months for the moon to be perturbed away --- I guess we'd have to do the math assuming moon at apogee and then cut the gravity.

Obviously you'd also have to know what caused the gravity to decrease. Is it a universal change in G? Then the Sun would expand, decrease its fusion rate (presumably), and the Earth orbit would go eccentric.

All sorts of fun things to think about --- if this happened, we'd probably finally stop arguing about the number of planets...

Ken G
2006-Aug-24, 09:21 PM
Well, the moon would instantaneously be in a much more eccentric orbit, right?
I was talking about the time it would take the Moon to possibly strike Earth. It would be in solar orbit right away-- it already is that.


Obviously you'd also have to know what caused the gravity to decrease. Is it a universal change in G? Then the Sun would expand, decrease its fusion rate (presumably), and the Earth orbit would go eccentric.
Interesting point, things would be different if it was G itself that was down by 1/4. Note that the Sun would initially expand, as you say, because it would be out of pressure equilibrium. In fact I suspect it would supernova. But if it later reformed, it would do so at a smaller size, to maintain fusion temperatures. The resulting high density would in turn retard the escape of photons, so the fusion rate would indeed decrease to establish thermal equilibrium, and the new solar-mass star would appear much less bright. But none of this would matter because the Earth would escape from the Sun if G decreased to 1/4. (Any circular orbit has 1/2 the kinetic energy it needs to escape, which would be twice what it needed if G was down by 1/4.)

pghnative
2006-Aug-24, 09:37 PM
I was talking about the time it would take the Moon to possibly strike Earth. Oh, I see now.
It would be in solar orbit right away-- it already is that.True, but the more interesting aspect is that the Moon would no longer be gravitationally bound to the Earth. I was guessing that the Moon's orbit would expand, and eventually be perturbed away from earth, but by your subsequent logic (any circular orbit...), the Moon would immediately have enough energy to escape Earth's gravity in this hypothetical situation.

Ken G
2006-Aug-24, 09:43 PM
Right, the factor 1/4 is pretty dramatic. I especially like thinking about your idea of doing this to the Sun!

trinitree88
2006-Aug-24, 10:13 PM
Not to mention the ruined roller coaster rides....who wants Kings Mountain at 25 instead of 100+mph...Lol. Pete:shifty:

Doodler
2006-Aug-24, 10:56 PM
You're right, and I'm wrong. But we'd still have to live on those ships because the Earth would be covered with water.


They'd be the only survivors. Especially after the tsunami triggered by crustal upwelling...

The Mid Atlantic ridge and the Ring of Fire would probably go off like crazy, the likes of which haven't been seen since the Great Rift Valley opened up in Africa.

Atmosphere would bleed off, but not necessarily immediately. Somewhere I heard that the Moon could retain a pretty reasonable atmosphere for at least 10,000 years.

ToSeek
2006-Aug-25, 06:16 PM
Atmosphere would bleed off, but not necessarily immediately. Somewhere I heard that the Moon could retain a pretty reasonable atmosphere for at least 10,000 years.

I would think it would get a lot thinner at the surface, possibly too thin to be breathable.

publiusr
2006-Aug-25, 07:27 PM
If you had a gravity reduction beam the internal pressures of the earth world tear the planet apart

Bob
2006-Aug-26, 06:37 PM
I would think it would get a lot thinner at the surface, possibly too thin to be breathable.

You were Bobbed on post 14. Sea level presure is the weight of the column of air above a unit area, which is now much reduced.

suntrack2
2006-Aug-29, 10:45 AM
I think the take off of a aeroplane will be much different in such low gravity, will there a possibility of low fuel consumption for lifting of plane? :)

phunk
2006-Aug-29, 04:10 PM
I think the take off of a aeroplane will be much different in such low gravity, will there a possibility of low fuel consumption for lifting of plane? :)

Maybe but it's not that simple. While there would be less weight, there would also be less lift due to reduced air pressure. They might need faster takeoff and landing speeds than before.

ToSeek
2006-Aug-29, 06:36 PM
I would bet no current airplane could get off the ground. They'd all have to be redesigned.

Ronald Brak
2006-Aug-30, 05:34 AM
I would bet no current airplane could get off the ground. They'd all have to be redesigned.

Nah, turboprops could take off as their fans compress air and wings would generate less lift in thinner air but less lift would be required. Landing would be a nightmare as your control surfaces would be much less responsive in thin air.

Of course it's all academic as we would have conked out from lack of oxygen. Humans are a cheap design and we can only detect too much carbon dioxide and can't detect a lack of oxygen. (Airlines are serious when they say put on your own oxygen mask before attempting to help others.) However, I suppose it would take a little time for the air to thin out. Perhaps this could allow some exceptional humans to survive? These would have to be people who have a tendency to constantly pant for no good reason.

Lake Eyre in Australia would be a good place to hang out as it is below sea level. Eyre would be one of the few places where we'd have a chance to breath air. Deep mineshafts might be another. Particularly if you use a lid and an air compressor.

suntrack2
2006-Aug-30, 11:19 AM
thanks for that take-off

the asteriod fall on earth will bounce aside after taking its first leap on earth and then went sowhere? its falling on earth will not be normal? it will not create any vast devastation on earth? or its intensity will be lower when it will fall on the earth in 2-3 phases, like a swinging ball bounce back and will rest on the ground unless the proper gravitational force applies?

Ronald Brak
2006-Aug-30, 11:58 AM
the asteriod fall on earth will bounce aside after taking its first leap on earth and then went sowhere?

Are you asking will asteroid impacts be less deadly with lower gravity? No, not really. Asteroids are already moving very fast. The moon has low gravity, but look at the enormous craters on its surface.

pghnative
2006-Aug-30, 01:19 PM
Are you asking will asteroid impacts be less deadly with lower gravity? No, not really. Asteroids are already moving very fast. The moon has low gravity, but look at the enormous craters on its surface.
I disagree. Asteroid impacts would be of lower velocity, since the maximum impact velocity is equal to escape velocity. Objects moving faster than escape velocity (relative to earth, which is the point here) have a vastly higher chance of missing earth than do objects with velocities lower than escape velocity. (The fast ones whip around on hyperbolic orbits. The slower ones get sucked in.)

Of course, the average asteroid hit would still be fairly devastating, as the lunar surface attests.

montebianco
2006-Aug-30, 03:28 PM
I've been losing weight, so the earth's gravity has been reduced by about 10%.

cjl
2006-Aug-31, 12:45 AM
I disagree. Asteroid impacts would be of lower velocity, since the maximum impact velocity is equal to escape velocity. Objects moving faster than escape velocity (relative to earth, which is the point here) have a vastly higher chance of missing earth than do objects with velocities lower than escape velocity. (The fast ones whip around on hyperbolic orbits. The slower ones get sucked in.)

Of course, the average asteroid hit would still be fairly devastating, as the lunar surface attests.


Actually, assuming the object that hits was not in orbit around earth, or close to it when it started, escape velocity would be a minimum speed for a collision, with higher speeds possible depending on the original speed of the object. An object does not need to be going <vescape to hit, it just needs to be on an approach path close enough for the gravity to give it a slight deflection to hit.

pghnative
2006-Aug-31, 01:08 AM
Actually, assuming the object that hits was not in orbit around earth, or close to it when it started, escape velocity would be a minimum speed for a collision, with higher speeds possible depending on the original speed of the object. An object does not need to be going <vescape to hit, it just needs to be on an approach path close enough for the gravity to give it a slight deflection to hit.

Arrrgh --- I had just written a very witty post showing you the error of your ways when I discovered that you are right and I'm wrong.

I had misinterpreted sites like this one (http://janus.astro.umd.edu/astro/impact/) which let you simulate impacts. They give a maximum impact speed, and at some point I learned that, and put two and two together to make five. But the maximum speed is for solar system bodies (which otherwise wouldn't be in orbit).

Oh well -- at least I figured out my error before posting again...

suntrack2
2006-Aug-31, 08:45 AM
Thanks for the replies, as far as planetary impact on earth possible, may be moon or other planet's impact, will it loose or less than the previous? The intensity of tides in the sea will become slower?

The lift in the multistory building will ascend easily, even its energy requirement will be lesser? Or upto the first floor would it be possible to ascend on without stairs? the playing games like cricket and baseball will work out very interestingly in the lower gravity, so may be possible to catch the ball will become tedious in such low gravity within the boundaries?


sunil