Humans Not Meant for Space

An object falling from infinity? Scratches head.
Incidentally they were discussing the atmosphere on QI last night,and they quoted a french authority that say the earth's atmosphere ends at 60 miles or thereabouts.
One of the contestants said 'Why not just have a ladder going straight up,climb up and walk off?' I was waiting for Stephen Fry to mention the Space Elevator concept but he didn't.
 
Seems to me the first, greatest expenditure of resources could be used to put a platform up there in geo-stationary orbit, then they could just lower a stairway any time they needed to bring up supplies or personnel.

I'd buy a stairway to heaven, wouldn't you?
 
AE

If you climbed a 60 mile high ladder and stepped off, you would fall straight back down to Earth, and end up as raspberry jam.

To orbit at 60 miles high, you need both altitude and sideways velocity. You will still be falling, but if your velocity sideways is fast enough, you will move out as far as you fall. That makes the orbit.

Incidentally, there is no point at which we can firmly say the Earth's atmosphere ends. It thins gradually until the number of molecules per cubic centimetre is the same as in space. The point at which that happens is very fuzzy. However, at 60 miles, it is thin enough to be almost equivalent to space.
 
But once you're in Space you can just hang there,neither falling nor climbing. So (un)technically you should able to fly to altitude,punch thru the last layer of atmosphere and then come to a stop. What i'm saying is what is stopping a ship from leaving the atmosphere at normal speeds? Think of it another way. Lets say you get a machine that can hover on the spot,like a helicopter does. It hovers at the edge of space. You do an EVA and walk into space.
 
AE

In space, you are still subject to the gravity of the Earth. This means you are falling, since you are not supported. If you have no serious sideways motion, you will just fall back to Earth. Satellites orbit because they have substantial sideways motion. For example, a satellite in geostationary orbit, 36,000 kms up, will be moving sideways at 3 km per second. It is falling, but the sideways motion carries it further from the Earth, which exactly compensates for the fall.

If you climb a 60 mile (100 km) high ladder and step off, you have very little sideways motion, and will fall without anything to compensate for the fall. Thus, you will crash to the ground and be smashed to slush.

On the other hand, if the ladder was 36,000 kms high, it would end at the geostationary point. Since the top of the ladder is moving sideways, going around the Earth every 24 hours, then if you step off, you too will be moving sideways at the rate of once every 24 hours - or at 3 kms per second. This sideways motion is enough to compensate for the rate of fall, and you will stay in place relative to the Earth. This is the principle of the space elevator.
 
AE35Unit said:
But once you're in Space you can just hang there,neither falling nor climbing.
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Aha, there's the misconception. No. If you are anywhere near a largish mass, say a planet or a star, you experience a force. If there is no compensatory force, Newton informs us you will undergo an acceleration. Since this force is not transmitted by atmosphere, it makes no difference whether you are in 'space' (Meaning drift. You can no more get out of space than you can escape time. Vacuum would be more accurate) or three metres above sea level. Everything in Earth orbit is falling all the time.

However, if two things are falling at the same speed, they have no tendency to separate, so if one of them is an observer, the other appears motionless; possibly even a truth, as no frame of reference can be taken as an absolute; while the planet is attracting you at how ever many metres per second per second it does (at that height it won't be all that much less than the 9.8 at sea level) you're accelerating the Earth with the same absolute force (but a considerably smaller delta v, as it's a bit more massive).

When you're on your ship going to Jupiter, and you get out to replace the broken bit of your communications gear, you're belting along at a rate of knots (if they use knots to measure speed in space, which I doubt) but you can still spacewalk the length of your vessel, because you both start with the same velocity. Actually, the ship has a gravitational pull, too, but it's so much less massive than a planet the attraction is less than the barmaid in the Orangerie. The only time you'll tend to separate is when firing the engines, or (slightly) tidal effects when you slingshot round Jupiter due to your differing centres of gravity.

Free fall means falling freely, not freedom from falling, and that great big vacuum out there doesn't give you many clues as to whether you're undergoing acceleration or not, until you hit something.
 
Ah of course. Any body in Space creates its own gravity field. And so being close to Earth you are still drawn to it and need to 'escape'. Only if you're away from any large rotating body can you hang motionless,where there is no up and down.
 
AE35Unit said:
Ah of course. Any body in Space creates its own gravity field. And so being close to Earth you are still drawn to it and need to 'escape'. Only if you're away from any large rotating body can you hang motionless,where there is no up and down.
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Motionless? Relative to what? Everything in the universe is in motion.
 
Right. Several things. First, I was not aware that AE was made of raspberry jam. I'll bet Hannibal would enjoy him for lunch. ;)

Second, Chris has a way of "thinking out loud" so that when he says stuff like "you have an object falling from infinity" what he means is that gravitational fields extend out forever (technically) from a point roughly at the center of that mass. (The bigger the mass, the bigger the field). That is the (equal and opposite) force one must overcome when exiting Earth's gravitational field.

Also, just as the "velocity" (in technical terms velocity includes a direction or "vector" as well as a speed.) increases as the square of the distance (9.83 meters/sec/sec) once again we are actually gaining in speed (when falling) which is called acceleration (as Newton discovered by dropping an apple on his head :D ) Every second an object falls (ignoring air friction) it gains another 9.83 meters of speed. So, now, take that in reverse and try to fly up and away (No one has mentioned fortified helium balloons yet), and as the saying goes "the faster you go, the behind-er you get".

Also, by the way, I rather liked Skeptical's example about the satellite:
For example, a satellite in geostationary orbit, 36,000 kms up, will be moving sideways at 3 km per second. It is falling, but the sideways motion carries it further from the Earth, which exactly compensates for the fall.
Click to expand...

Another way to look at that is like having a circular escalator that goes around the planet. For each drop toward Earth, you must then thrust away from the intersection of the circle that defines your orbit by the same amount so that you keep a constant altitude.

The question is, where is the end of the circle? And does anyone know how Einstein came to the conclusion that if one started at any random point in the universe and kept going forever, they would end up right where they started?

"The truth will come to you at last, when we are one and one is all."

- Some British rock group.
 
Why should it stop? There's no way of making a Faraday shield against gravity or, as far as we know, reflecting it back. If it diminishes as the square of the distance, as seems fairly adequately proved, then it never reaches zero.

The only possible (and unproven) exception I have seen for this is a black hole; if gravity propagates at the speed of light, to satisfy Bert E., then possibly some gravity can't radiate from a black hole, folded back in by itself. There's still plenty left, and doing the measurements to prove this sounds rather hazardous. And nobody has caught, or even mathematically proved the existence of a graviton, yet.

Grandfaloon said:
Chris has a way of "thinking out loud" so that when he says stuff like "you have an object falling from infinity" what he means is that gravitational fields extend out forever (technically) from a point roughly at the center of that mass.
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Politely saying that Chrispy spends a fair portion of his time totally incomprehensible, and requires a translator. Mathematicians have no problems with thought experiments that strip the atmosphere off the Earth and sand down mountains to get a millimetrically smooth surface ; physicists (and the inhabitants of the planet) are a bit less convinced whereas the engineers would prefer to cool the whole thing down to less than a degree Kelvin, so the solidified atmosphere will smooth out the surface…
 
See i always equate a gravitic field to be like a magnetic field. It has a definite influence but beyond a certain point it fades to nothing. Its finite.
 
Apologies Chris. No Harm meant by that statement (thinking out loud etc.) It's actually a compliment in disguise because I've read a lot of your posts, and I can see very well that you are impressively learned. Plus, I have the same tendency, and therefore tend to recognize it.
 
AE35Unit said:
See i always equate a gravitic field to be like a magnetic field. It has a definite influence but beyond a certain point it fades to nothing. Its finite.
Click to expand...

A magnetic generator has two poles (north, and south) which, at a sufficient distance, cancel each other out. If a magnetic monopole did exist, it would spread out just like gravity.

Similarly, electrostatic imbalance – an excess or deficiency of electrons – tends to even out over a fairly small distance, a light year or two, so that is self cancelling on a cosmic scale.

Gravity seems to just keep on going.

Still, they're worried that there isn't enough of it (or that they can't explain enough of it away) so they're inventing intangible, undetectable dark matter (with its own dark energy) to boost their theories…
 
Well i guess it makes sense. After all the sun is 93 million miles from us yet it influences us strongly. Plus it keeps the other planets travelling round and round in their orbits
 
To return to an old topic, I came upon an old Discover magazine(November 2007), which said: "1. Nearly every astronaut experiences some space sickness, caused by the wildly confusing information reaching their inner ears. In addition to nausea, symptoms include headaches and trouble locating your own limbs. Just like college, really. 2. And those are the least of your worries. In weightlessness, fluids shift upwards, causing nasal congestion and a puffy face; bones lose calcium, forming kidney stones; and muscles atrophy, slowing the bowels and shrinking the heart." I suppose you could still survive, though the puffy face seems the worst affliction.
 
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