Skydiving on the Moon

In article , Ron Miller
wrote:

"G=EMC^2 Glazier" wrote in message
...
Hi Painius True acceleration would be 1/6 slower on the moon than on
the earth. You would start your fall with a feeling of slow motion,and
like you calculated have 27 seconds to worry about the ground coming up
to you. I think coming up to you is what you would think,rather than
falling into the surface (yes?) Well you weigh 1/6 less,and its weight
times speed that gives the force of impact. At that height you are just
as dead,as on Earth. Painius here is where inertia (mass)
comes in (fits) Your mass is the same as you had on Earth. Lets say
the force hitting the moon"s surface is like being hit by a train going
100 mph There is no difference being hit by a train on earth,or a train
on the moon going at the same speed. Asminov told me
this in his book "Physics" Bert


Since you would be in free fall, I don't think there would be any sense of
acceleration at all. If you are falling while in a spacecraft, it would be
accelerating right along with you, so it would give you no clues. If you in
a spacesuit dropping toward the surface, there still would be no
sensation---other than the awful one of watching the lunar landscape rushing
toward you.

RM

You might get a warm,fuzzy feeling as your bowels let loose.Also,the
last thing to go through your mind would be a Lunar boulder.Bill.

Falling is a scary thing. Your brain does not like it when it has no
control of the situation. Its like being buried alive.(can't get out of
that situation) People feel secure when they have the earth's surface
pushing up under their feet. Some people are afraid of elevators
because once inside they can't control the situation. I don't
think being in a space suit would be good idea with people with
claustrophobia. The fear of falling is in man's ID. It came
from the time he lived high up on trees when he went to sleep. If you
dream you are falling(very common dream) you will wake up with a start.
Falling is imprinted in our DNA Bert

Painius wrote:

So THAT's what i'm talking about... feeling the "being
thrown back" feeling that we can feel when our bodies
are accelerating. Would you feel this feeling if falling
toward the surface of the Moon?

I don't think so; the inner-ear fluid would be falling at the same
rate as the chamber containing it; likewise an accelerometer would
show no reading. I think the 'vertiginous' feeling experienced by the
skydiver right after jumping would have to do with the *deceleration*
caused by being 'detached' from the aircraft's thrust while
encountering drag in the airstream, _viz_ aerodynamic forces rather
than gravitational. In an accelerating car the sensation of "being
thrown back" comes from the forward pressure of the seat against your
back; accordingly in the inner ear the chamber gets pushed forward
(as the tension in your neck causes your head to 'catch up' with your
body), in turn accelerating the fluid. But true free-fall would feel
the same whether in the "Vomit Comet", in earth orbit, or falling
towards the moon, since gravitational forces, unlike mechanical ones,
are the same everywhere within any (small) system without requiring a
series of 'actions & reactions' to propagate through it by means of
secondary pressure and tension forces.

--
Odysseus

Hi Painius Falling inside a space suit is different. He would not feel
any differents from falling than when he was weightless in the space
ship. What he needs to cushion his fall is to have a space suit that
inflates to the size of the Pillsbery dough boy. It is better to bounce
than to go plop.Even NASA knows that. Bert

"G=EMC^2 Glazier" wrote in message...
...

Hi Painius Falling inside a space suit is different. He would not feel
any differents from falling than when he was weightless in the space
ship. What he needs to cushion his fall is to have a space suit that
inflates to the size of the Pillsbery dough boy. It is better to bounce
than to go plop.Even NASA knows that. Bert

Good, Bert, now forget the landing and focus upon the
falling...

From 2000 feet you have 27 gleeful seconds of freefall
with no air resistance and no terminal velocity.

Fear? Not you Bert! You traveled to the Moon, for
crissakes! Now look toward the horizon and tell me
all about HOW YOU FEEL.

Your body is being accelerated. You are gaining speed
to the tune of about 3.6 miles per hour each second. If
you started falling at 2000 feet (zero mph), then by the
end of 10 seconds you have accelerated to 36 mph. By
20 seconds you will be going over 70 mph...

Would you FEEL yourself being accelerated?

If so, then why?...

and if not, then why not?

happy days and...
starry starry nights!

--
Asimov! where have you gone?
Your written word goes on and on,
All becomes so clear to see
In Asimov's Astronomy!

Paine Ellsworth

"Painius" wrote in message
...

Your body is being accelerated. You are gaining speed
to the tune of about 3.6 miles per hour each second. If
you started falling at 2000 feet (zero mph), then by the
end of 10 seconds you have accelerated to 36 mph. By
20 seconds you will be going over 70 mph...

Would you FEEL yourself being accelerated?

No.

and if not, then why not?

Because everything by which you could judge acceleration is also falling at
the same rate. If you could see the ground rushing up at you, you would
certainly *know* you were accelerating, but there would be no physical
sensation. That is, if you were blindfolded or in a windowless capsule, you
would have no idea you were falling until you hit the ground. You would only
know you were in freefall, but not whether you were in orbit or dropping
toward the moon.

RM

Let me jump/skydive in once more.

The inner ear thing works through inertia as does your behavior in the car,
but its infinitely more sensitive to: change. And that's the key.

How it works is you have a fluid filled device called a cochlea in each ear
(its the one shaped like a snail shell, and I've undoubtedly misspelled it).
When you move in one direction the fluid, because of inertia, tries to stay
put, which also means - relative to the walls of the structure - the fluid
is moving in the opposite direction. Float a small piece of paper in your
coffee cup and rotate the cup and you can see this effect. The coffee and
the paper try to stay stationary while the cup moves around it.

The walls of your (misspelled?) cochlea are lined with thousands of cilia
(hair-like sensors) that pick up on this relative fluid movement. Like a
lot of senses your brain knows how to interpret by reversing the direction.
When the elevator suddenly starts down, the fluid moves up (tries to stay
put) relative to the sides of the device and the brain interprets this as
falling.

But once you've reached equilibrium your brain/ear stops getting the input,
which is important because it allows you to focus on other things, like
deploying your parachute or, in this case, your bouncy suit. The reason
this can occur is the system, the fluid in your ear, likewise gains
equilibrium. It will be either static (like you being pressed against the
seat of your car during acceleration) or flowing at a constant rate which
your brain can interpet as 'no change there'. I'm not 100% sure which of
these two occurs because I've never had to think it through to this degree
before, but I would expect the latter (a steady rate rotation of the fluid
in the inner ear) would be the case. In either case I believe you would not
feel yourself falling on the moon, anymore than you feel yourself
freefalling on earth. Except for the lack of wind resistance the two
systems are completely analogous. If something occurs to change your rate
of fall/acceleration then the system (which is based on detecting an
inertial response in the fluid) would immediately notice.

To go back to the earthbound skydiver, when I jumped as a rank amateur the
plane was going at about 70 mph and I started by hanging from the wing strut
then releasing, so I think what I was feeling on release was a momentary
sensation of acceleration, not deceleration (sp?) due to wind resistance;
you physics guys could likely figure that out pretty quick.

Of equal import is the ground rush feeling I described earlier. There are
two things going on there. One is just plain fear. And it's true, we are
biologically designed to be afraid of falling because of our tree dwelling
ancestors. The other thing that is going on is the brain is, in a panic,
trying to sort out two conflicting messages. The normal inner ear motion
detector is telling the brain nothing is going on, while the eyes are
telling the brain, 'your damn right something is going on and you better do
something about it'.

Motion sickness is caused by the same conflict going in the opposite
direction. Your eye/brain is telling you the ship's cabin is not moving or
is barely moving at all, but your ear/brain is telling you 'you're being
thrown all over the place, do something about it now!' If you go out on the
deck it gets even worse: your ear/brain system says you're being tossed
around, your eye/brain system says you're not: the deck and sides (your
inertial frame when things are steady) are staying in the same spot relative
to you, and then you see waves that are moving sometimes opposite to the
motion of the boat, and then you see the deck that says your not moving
despite your ears and the waves, and then you throw up.

Bill C.

"Painius" wrote in message
...
"G=EMC^2 Glazier" wrote in message...
...

Hi Painius Falling inside a space suit is different. He would not feel
any differents from falling than when he was weightless in the space
ship. What he needs to cushion his fall is to have a space suit that
inflates to the size of the Pillsbery dough boy. It is better to bounce
than to go plop.Even NASA knows that. Bert

Good, Bert, now forget the landing and focus upon the
falling...

From 2000 feet you have 27 gleeful seconds of freefall
with no air resistance and no terminal velocity.

Fear? Not you Bert! You traveled to the Moon, for
crissakes! Now look toward the horizon and tell me
all about HOW YOU FEEL.

Your body is being accelerated. You are gaining speed
to the tune of about 3.6 miles per hour each second. If
you started falling at 2000 feet (zero mph), then by the
end of 10 seconds you have accelerated to 36 mph. By
20 seconds you will be going over 70 mph...

Would you FEEL yourself being accelerated?

If so, then why?...

and if not, then why not?

happy days and...
starry starry nights!

--
Asimov! where have you gone?
Your written word goes on and on,
All becomes so clear to see
In Asimov's Astronomy!

Paine Ellsworth

Just to expand a bit on Bill C's most excellent synopsis (and you did
spell 'cochlea' correctly, Bill)-
Another 'thought experiment' for Painius, involving the
2000 foot high tower on the moon. At the top of the tower there's a
cantilever arm sticking out, oh, say 30 feet. Directly below the end of
the arm, 2000 feet below, is a big inflated airbag, the kind movie stunt
peolpe use back on Earth to break their fall.
You have a helper along, and you're both in spacesuits
(of course!). But since you are gonna be the "fall guy", your suit has
the visor completely blocked so you have no visual cues. In this state
of sensory deprivation in your suit, you are hung by a single cord from
the end of the arm, with your helper instructed to cut the cord but
*not* tell you when. By and by, PING he snips the cord... So what is the
sensation of becoming weightless in an instant? How quickly does the
cochlear system acclimatize to the weightless state? Bill...?
Obviuosly, once you're in the falling/ accelerating
phase, your entire anatomy, tactile nerves, cochlear system- everything,
is accelerating at exactly the same rate, just "going with the flow". So
there is nothing to generate any tactile or cochlear signals to tell you
anything during freefall.
But when you hit the airbag, then you feel the sudden
deceleration.

Another thought experiment comes to mind- Suppose the moon were all
alone in deep space, far away from Earth and its perturbing influence.
An object falls to the moon from an infinite distance (or at least an
extreme distance), and hits the moon dead center. How fast is the object
going when it hits (i.e., its impacting velocity)?

oc

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Bill Sheppard wrote:

Another thought experiment comes to mind- Suppose the moon were all
alone in deep space, far away from Earth and its perturbing influence.
An object falls to the moon from an infinite distance (or at least an
extreme distance), and hits the moon dead center. How fast is the object
going when it hits (i.e., its impacting velocity)?

Exactly the same as the escape velocity from the surface. This
follows from the definition of escape velocity, which is the speed at
which a body has the same amount of kinetic energy as it would have
gravitational potential energy if removed to an infinite distance
from the surface (or some other altitude of reference). In the case
of the moon's surface the figure is 2.38 km/s, or a little over 5300 mph.

To calculate the escape velocity from the surface of any body whose
mass and radius are expressed as fractions of the respective data for
the earth, one can use the formula

V_esc = 11.19 km/s * sqrt(mass/radius).

In the case of Mars, for a trendy example, we have

11.19 km/s * sqrt(0.107/0.532) = 5.02 km/s.

--
Odysseus

Odysseus wrote,

Exactly the same as the escape velocity
from the surface.

Bingo! Right you are, Ody. And under the flowing-space model of gravity
it's also the literal velocity of the spatial inflow at ground level.
This is pointed out in Henry Lindner's thesis (posted several times
previously). oc

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