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Author Topic: Gravity lifts  (Read 5408 times)

Offline Nobody's Confidant

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Gravity lifts
« on: 23/10/2007 17:43:07 »
These handy devices send down a ray that lowers gravity in the area inside the beam. So you float up to where you want to go. The best part is none of the boring music, but can this even be done?


 

Offline Bored chemist

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Gravity lifts
« Reply #1 on: 23/10/2007 19:09:15 »
No.
 

lyner

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Gravity lifts
« Reply #2 on: 23/10/2007 22:32:12 »
Put me down for one when you find it in the catalogue.
 

another_someone

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Gravity lifts
« Reply #3 on: 23/10/2007 23:46:07 »
Let us for one moment consider the possibility (infeasible though it may be) that one of these devices would exist.

Now, you are orbiting around the Earth, and switch on the device - so what would happen.

Firstly, you need a massive source of energy to power it - but we'll assume you have that from somewhere.

Secondly, if you have this tube with no gravity within, but lots of gravity outside - that gives you a massive gravity gradient at the interface between the two.  If the gradient is too steep (the wall too narrow), you could even create Hawkins radiation between the two (this itself, apart from being dangerous, would be a massive loss of energy).

Thirdly, you have to make sure the orbiting spacecraft would not be affected by the beam, otherwise the spacecraft itself would lose its orbit around the Earth.

Now, for the really spectacular bit - when you switch on the beam, and point it down to Earth, the first thing that will happen is you will have a massive rush of air, as the entire of the Earth's atmosphere, now freed from the constraints of gravity, rushes up your gravity free pipe, blasts you out of orbit, before leaking out into space.

But, aside from the risks associated with using such a device, what use would it be?  The laws of conservation of energy would require than to neutralise the gravity of the Earth, you need to use as much energy (at a minimum) as is contained in the gravity you are neutralising.  If you are using that much energy, we have other ways of lifting things up into space with the addition of energy (at present, we use chemical rockets - but other means may be devised, but they will all require a minimum amount of energy - the main problem with chemical rockets is their need to lift a lot of fuel halfway up in order to get the rest of the rocket all the way up - but I am sure there are better ways of overcoming this inefficiency).
« Last Edit: 23/10/2007 23:51:50 by another_someone »
 

lyner

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Gravity lifts
« Reply #4 on: 24/10/2007 12:30:38 »
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The laws of conservation of energy
That says it all, A-S.
The best 'gravity lift' we can hope for is the tethered satellite. This is not completely ridiculous but involves a large geostationary satellite, joined to the Earth by a long tether. Once (yes - once) you have got it there, the only energy you need to get to the top (a 36,000km journey) is the potential energy you have gained. No wasted chemical energy  from a rocket.
It's mainly a materials problem.  It would change the situation for spaceflight  and using  extra terrestrial materials dramatically.
 

Offline nikomaster

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Gravity lifts
« Reply #5 on: 05/11/2007 02:04:49 »
We can write new laws as allways we do.
 

another_someone

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Gravity lifts
« Reply #6 on: 05/11/2007 02:29:22 »
We can write new laws as allways we do.

Writing new laws is easy - I can write a law that says 1 + 1 = 5, but the fact that I have written it so does not make it so.

It is one thing to write a law, another to prove it to be so.

Are you suggesting that you could somehow prove a law to be true that undermines the concept of the conservation of energy?  Without a conservation of energy, then how would you constrain any probable action?  If you cannot constrain any probable action then you have no laws at all - because all possible outcomes are merely arbitrary.
 

lyner

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Gravity lifts
« Reply #7 on: 05/11/2007 18:04:33 »
A-S, I refer you to another thread -
http://www.thenakedscientists.com/forum/index.php?topic=11230.0
Are you being quite consistent, here?
Cannot someone challenge established Science here too?
 

another_someone

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Gravity lifts
« Reply #8 on: 05/11/2007 18:40:25 »
A-S, I refer you to another thread -
http://www.thenakedscientists.com/forum/index.php?topic=11230.0
Are you being quite consistent, here?
Cannot someone challenge established Science here too?

On the contrary, I think there is a problem with how you are interpreting what I have said (either there or here).

I have not questioned nikomasters right to challenge established science - but such a challenge is itself then open to challenge.

I have not told nikomaster he must not think up new laws, but I have suggested that his new law would have to successfully fend off certain apparent challenges.  How would that contravene what I have said in the other thread?
 

lyner

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Gravity lifts
« Reply #9 on: 05/11/2007 22:58:47 »
I think what you wrote is just a polite way of telling someone they're wrong, actually.
You are 'strongly directing' him away from that particular way of thinking; always good fun to do and hard to resist when it's so plainly at odds with received wisdom.
Have you ever thought of changing your screen-name to "devil's advocate"?
 

another_someone

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Gravity lifts
« Reply #10 on: 05/11/2007 23:50:22 »
I think what you wrote is just a polite way of telling someone they're wrong, actually.

I try very hard not to say 'you are wrong' (although sometimes I slip up), because I don't believe I have the right (nor even the qualifications) to say that - but rather, to say 'I think you are wrong'.

You are 'strongly directing' him away from that particular way of thinking; always good fun to do and hard to resist when it's so plainly at odds with received wisdom.

But the whole point is that, even if the guy is wrong, just telling him that tells him nothing useful.  Explaining why I believe they are wrong means that they have to think about what it is they are proposing, but potentially that thinking leaves them the option of proving my prejudices to be wrong.

Have you ever thought of changing your screen-name to "devil's advocate"?

 :)
 

lyner

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Gravity lifts
« Reply #11 on: 09/11/2007 00:32:09 »
Quote
But the whole point is that, even if the guy is wrong, just telling him that tells him nothing useful.
But sometimes just saying"bo****ks" can make one feel a lot better AND get a point across.
Not that it would ever happen on this forum, of course!
 

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Gravity lifts
« Reply #11 on: 09/11/2007 00:32:09 »

 

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