How fast can we go?

[GOD]

Gravity, weak as it is, is only attractive...so its effect "accumulates."

Gravity isn't only attractive. This can be proven in deep space by slowly moving two objects of equal size towards each other. The objects won't touch or bounce off one another -- they will orbit each other.

Wouldn't they just crash into eachother if on an exact course to another body with enough mass to have been attracted in the first place? Or is the magnetics of the bodies in motion what keeps them from colliding?

How then was the moon created? Or was this just the lump that removed itself from the molten earth as it rotated like crazy and the bulge of the moon pooped itself out...?

Is it then that the two bodies in space that attract eachother must be of equal size and mass (roughly speaking) so that they wouldn't collide (one being bigger and just pulling the smaller one into it... but then mercury is doing a good job of not being sucked in by the sun).

*confused*

I thought orbits occured because the attraction of the two objects weren't pulled directly to eachother, but more in the general direction of one another, and as they passed, their masses tugged and changed the directions of each, making them start to dance in the familiar round and round we go.

Arramon: Now you're thinking. Note Orin's comment in-line with current popular scientific opinion naming centrifugal force as the reason the planets are locked in the orbits they are. You're starting to question this, and suspect otherwise... yes, the moon DOES move around the Earth too slowly to account for centrifugal force to keep it out there -- doesn't it? Yet it's not crashing into the Earth... Keep it up... it's thinking along these lines that's leading to discovery of nature's repulsion force inherent in gravity.

[makc]

the moon DOES move around the Earth too slowly to account for centrifugal force to keep it out there -- doesn't it? Yet it's not crashing into the Earth...

And God said, "Let there be lights in the expanse of the sky to separate the day from the night, and let them serve as signs to mark seasons and days and years, and let them be lights in the expanse of the sky to give light on the earth." And it was so. God made two great lights—the greater light to govern the day and the lesser light to govern the night. He also made the stars. God set them in the expanse of the sky to give light on the earth, 18 to govern the day and the night, and to separate light from darkness.

[Orca]

Arramon: Now you're thinking. Note Orin's comment in-line with current popular scientific opinion naming centrifugal force as the reason the planets are locked in the orbits they are. You're starting to question this, and suspect otherwise... yes, the moon DOES move around the Earth too slowly to account for centrifugal force to keep it out there -- doesn't it? Yet it's not crashing into the Earth... Smile Keep it up... it's thinking along these lines that's leading to discovery of nature's repulsion force inherent in gravity.

Arramon: yeah, um, that's one suggestion.

My suggestion is to keep reading, take more classes, increase your knowledge base, continue to develop your critical analysis skills...then you'll be better equipped to develop your own insights, to "rend the wheat from the chaff." I'm not sure what folks like "GOD" get out of making these kinds of posts in this type of forum; it seems they are always going to be in the background.


GOD: You know, Einstein famously said, "God doesn't play with Dice." Quantum mechanics tells us otherwise; however, I am willing to bet that if he does indeed exist, he doesn't play with emoticons!

[Arramon]

*still lost becuz them answers made me say huh?*

*off-topic*

I have not studied any type of Astrology/Astronomy/Cosmology or any other type of Space-oriented courses, and only think of things and ask questions pertaining to what interests me. I don't plan on getting degrees in any of those fields, so I won't spend years and years trying to educate myself in a field that will never bring me income (I am, after all, only an Accountant, artist, poet and avid fantasy reader, not a Physicist/Cosmologist).

This is more a hobby that I've had since childhood. And since we are all children in the physics of the universe and whats deep within the smallest particle of matter, than I think it best to see how others think and feel about the hobbies I keep.

And, the analytical skills I use each and everyday pertain to contracts and purchase orders, system database breakdowns and client related purchases and expenditures.

I rely on great people like those found on APOD and other astronomy related forums to help me fill in gaps that I know nothing about, and that's only AFTER I read the hundreds of comments for that one topic where about 12 people are bantering back and forth and only about 2-3 of those people think otherwise from what the majority feel is actual fact (based on theory, of course). =b

*on-topic*

[orin stepanek]

Hi Arramon! I liked your 'toon. Actually centrifugal force doesn't really exist. It is actually gravity acting on a planet keeping it from moving away from the sun. The way I see it; it is actually the balance of gravity with the speed of the planet. http://www.infoplease.com/ce6/sci/A0811114.html
As you can see I'm not a physicist either but am interested in APOD. I really enjoy reading the comments by other readers and I've learned a bit from them.
Orin

[Qev]

yes, the moon DOES move around the Earth too slowly to account for centrifugal force to keep it out there -- doesn't it? Yet it's not crashing into the Earth...

Actually, if you plug the numbers into the equation for orbital velocity, the Moon needs to get 'round the Earth in just over 27 days... which it just so happens to do.

[harry]

G'day

This maybe of interesting reading on space travel.

http://www.andrews-space.com/images/vid ... 00307).pdf

MINI-MAGORION: A PULSED NUCLEAR ROCKET
FOR CREWED SOLAR SYSTEM EXPLORATION
Ralph Ewig*, Dana Andrews†
Andrews Space, 505 5th Ave South #300, Seattle WA 98104
* AIAA Member, Space Systems Engineer
† AIAA Member, Chief Technology Officer

ABSTRACT
Andrews Space has been awarded a NASA SBIR for
the investigation and experimental verification of the
Mini-MagOrion (MMO) concept. The MMO concept
is a GigaJoule scale pulsed nuclear fission device,
where low mass criticality is accomplished by the
electromagnetic compression of individual fission
pellets. The resulting fission reaction produces a
highly energetic plasma, which is then expanded
through a magnetic nozzle. Experiments on the Sandia
National Laboratory Saturn and Z pulsed power
machines were utilized to determine concept
feasibility, and the results are presented. The design of
the propulsion system based on the Mini-MagOrion
concept, together with a look at the accompanying
vehicle design and anticipated system performance are
also discussed. An analysis of engine / nozzle
interaction is presented, together with associated
requirements on the vehicles power and thermal
management subsystems. Vehicle performance
assessments are given for crewed and robotic missions
to the inner and outer solar system, indicating
favorable capabilities based on near-term achievable
technology.

[sugh]

I read today, about the earth's magnetic field changing. Do you think this could change our thinking about how we will move with future space travel?

[Arramon]

interesting...

[Conro]

why is everyone so convinced that centrifugal force doesn't exist?
either way, its besides the point. Planets aren't locked into orbits by centrifugal force, its gravity. And someone used the example of the moon. I think the best theory of its creation so far was that it was created by a large meteor crashing into the still cooling earth and propelling the debris outward into the near orbit of Earth. It has such a large amount of momentum leaving that the moon is leaving Earth anyway. And centrifugal force could easily be thought about if you visualize spinning in a circle, inertia wanting to continue forward, but you since your arms are attached to your body they can't leave(hopefully) and so the fly up.

[bystander]

http://en.wikipedia.org/wiki/Centrifugal_force

In classical mechanics, centrifugal force (from Latin centrum "center" and fugere "to flee") is an apparent force acting outward from the axis of rotation of a rotating reference frame.

A centrifugal force is a particular kind of fictitious force (also known as a pseudo force, inertial force or d'Alembert force), that exists for observers in a rotating reference frame. Unlike real forces such as electromagnetic forces, fictitious forces do not originate from physical interactions between objects.

[Arramon]

Was wondering what kind of forces work on hula hoops, and was gonna ask here, but found this quick explanation online:

http://www.worsleyschool.net/science/fi ... ahoop.html

What is the force that keeps a hula hoop up?

You might think that having hips would help, in which case girls ought to be better at this than boys. In fact, your hips do help ... but aren't really necessary at all. Anyone can make it work if they spin it just the right way.

So what keeps it up!?

To answer that question, let's look first at the force which is trying to make the hoop fall to the ground ... gravity.


The force of gravity acts downwards on the hoop at all times; this force should cause the hoop to fall, ... but of course it doesn't.
If the hoop stays at a constant height and does not move downwards, then there must be another force acting in the opposite direction that balances the force of gravity.

What is this force?

It's friction, of course.

The force of friction between Shandy's body and the hoop exactly equals the pull of gravity, so the hoop doesn't fall. Here's how it works:
As the hoop spins, Shandy's body exerts a force against the hoop, parallel to the ground, and perpendicular to the surface of the hoop.
This is the normal force.


The normal force is what causes friction; frictional force can be calculated using this normal force and the formula:

where the 'u' symbol is the coefficient of friction between the two surfaces, in this case 'sweater' and 'plastic'.

The normal force causes a frictional force perpendicular to FN.

This frictional force is opposite to the direction of motion (down) and must exactly equal the force of gravity;


A skilled hula hoop user will be able to maintain a normal force on the hoop during the entire time it circles the body, so the force of gravity is always balanced. A less skilled user will allow the hoop to jump away from the body; every time that happens, the normal force drops, and gravity takes over, pulling the hoop down.

I wonder if any objects or occurences in space happen like this... =/

[henk21cm]

Was wondering what kind of forces work on hula hoops, and was gonna ask here, but found this quick explanation online:

Three remarks:

The expression for Ff in Fn and µ is a formula for the maximum friction force. At any moment in time the actual friction can be lower than the product of µ and Fn.

The statement that Fg must be equal to Ff is only valid if there is a state of equilibrium. When the hoops slides along the body, down to the street, -evidently a state of non-equilibrium- Fg is larger than µ times Fn.

Centrifugal force is not just like the Coriolis force a force experienced and noticeble in a rotating frame. The centrifugal force for an observer at rest is:

Real: since the object (e.g. the moon) does not fall on the earth, the centrifugal force must be in equilibrium with the gravitational force.
Logical: since the object does not continue its motion in a straight line. I. Newton once stated that even a change in direction needs a force.

[Arramon]

http://www.spacedaily.com/reports/Trave ... t_999.html

Two Baylor University scientists have come up with a new method to cause a spaceship to effectively travel faster than the speed of light, without breaking the laws of physics.
Dr. Gerald Cleaver, associate professor of physics at Baylor, and Richard Obousy, a Baylor graduate student, theorize that by manipulating the extra spatial dimensions of string theory around a spaceship with an extremely large amount of energy, it would create a "bubble" that could cause the ship to travel faster than the speed of light.

To create this bubble, the Baylor physicists believe manipulating the 10th spatial dimension would alter the dark energy in three large spatial dimensions: height, width and length.

Cleaver said positive dark energy is currently responsible for speeding up the expansion rate of our universe as time moves on, just like it did after the Big Bang, when the universe expanded much faster than the speed of light for a very brief time.

"Think of it like a surfer riding a wave," said Cleaver, who co-authored the paper with Obousy about the new method. "The ship would be pushed by the spatial bubble and the bubble would be traveling faster than the speed of light."

The method is based on the Alcubierre drive, which proposes expanding the fabric of space behind a ship and shrinking space-time in front of the ship. The ship would not actually move, rather the ship would sit in a bubble between the expanding and shrinking space-time dimensions.

Since space would move around the ship, the theory does not violate Einstein's Theory of Relativity, which states that it would take an infinite amount of energy to accelerate a massive object to the speed of light.

say what?! O.o!

[henk21cm]

Since space would move around the ship, the theory does not violate Einstein's Theory of Relativity, which states that it would take an infinite amount of energy to accelerate a massive object to the speed of light.

Nice. Space is moving and what does happen to all matter inside space?

If the matter within space moves with space e.g. to another star, it would break conservation of energy, since it would have required an infite amount of energy to achieve lightspeed and warping space was just an unbelievebale -however finite- amount of energy. So that is not what i expect to happen, since as soon as conservation of energy is broken, someone could file a patent for a perpetuum mobile.

Space moves, and everything inside stays at the same distance relative to all other objects. The effect some performers can do: yanking the table sheet from the table, while all objects remain on the table at the same position. The net effect is something remarkable, however useless. Its like my hypothetical uncle supposedly living in England, while i live in the Netherlands and then we move space, so my uncle lives in the Netherlands, and i live in Germany. And again we do not live in the same country, nor do we speak the same language.

___________________________
Regards,
  Henk

Excuse, a bottle of sarcastic ink dripped on my keyboard.

[Arramon]

I like how it ends:

A new theory, called M-theory, takes string theory one step farther and states that the "strings" that all things are made of actually vibrate in an additional spatial dimensional, which is called the 10th dimension.

It is by changing the size of this 10th spatial dimension that Baylor researchers believe could alter the strength of the dark energy in such a manner to propel a ship faster than the speed of light.

The Baylor physicists estimate that the amount of energy needed to influence the extra dimension is equivalent to the entire mass of Jupiter being converted into pure energy for a ship measuring roughly 10 meters by 10 meters by 10 meters.

"That is an enormous amount of energy," Cleaver said. "We are still a very long ways off before we could create something to harness that type of energy."

yeah.. not quite that far yet in technology... d'oh!

[void]

Two Baylor University scientists have come up with a new method to cause a spaceship to effectively travel faster than the speed of light, without breaking the laws of physics.
Dr. Gerald Cleaver, associate professor of physics at Baylor, and Richard Obousy, a Baylor graduate student, theorize that by manipulating the extra spatial dimensions of string theory around a spaceship with an extremely large amount of energy, it would create a "bubble" that could cause the ship to travel faster than the speed of light.

To create this bubble, the Baylor physicists believe manipulating the 10th spatial dimension would alter the dark energy in three large spatial dimensions: height, width and length.

Cleaver said positive dark energy is currently responsible for speeding up the expansion rate of our universe as time moves on, just like it did after the Big Bang, when the universe expanded much faster than the speed of light for a very brief time.

"Think of it like a surfer riding a wave," said Cleaver, who co-authored the paper with Obousy about the new method. "The ship would be pushed by the spatial bubble and the bubble would be traveling faster than the speed of light."

The method is based on the Alcubierre drive, which proposes expanding the fabric of space behind a ship and shrinking space-time in front of the ship. The ship would not actually move, rather the ship would sit in a bubble between the expanding and shrinking space-time dimensions.

Since space would move around the ship, the theory does not violate Einstein's Theory of Relativity, which states that it would take an infinite amount of energy to accelerate a massive object to the speed of light.

Actually, this idea isn't entirely new. In 1994 Alcubierre wrote a paperon a warp-drive that works the same way, exceeding the speed of light globally, but not locally, by using a moving bubble. The only catch is you need exotic (negative) mass to do it. Alcubierre used General Relativity for his, but it's cool to see people using the next generation of physics now too (string theory).
- Ralph

[harry]

G'day from the land of ozzzzzzz


Bose-Einstein condensate: slowing down light to 38 mph
http://woodside.blogs.com/cosmologycuri ... in_co.html

Says a Harvard article: "This so-called Bose-Einstein condensate was not actually made until 1995, because the right technological pot to cook it up in did not exist. Vacuums hundreds of trillions of times lower than the pressure of air at Earth's surface, and temperatures almost a billion times colder that that in interstellar space, are needed to produce the condensate. Temperatures must be lowered to within a few billionths of a degree of absolute zero (minus 459.7 degrees F), where atoms have the least possible energy and all but cease to move around."

[Qev]

Centrifugal force is not just like the Coriolis force a force experienced and noticeble in a rotating frame. The centrifugal force for an observer at rest is:

Real: since the object (e.g. the moon) does not fall on the earth, the centrifugal force must be in equilibrium with the gravitational force.
Logical: since the object does not continue its motion in a straight line. I. Newton once stated that even a change in direction needs a force.

Wait, what? An observer in an inertial frame won't experience centrifugal forces. The only time you'd 'see' centrifugal forces in the Earth-Moon system is if you chose a rotating frame of reference (eg. one where the observer is rotating with the Earth-Moon system, on the same axis). In that frame, gravity and centrifugal force balance, but it's non-inertial.

In the inertial frame, there's only one (significant) force acting on the Moon: gravity.

[harry]

G'day from the land of ozzzzzzzz

I found this link. Could this be for real?

http://arxiv.org/abs/gr-qc/0411096
The warp drive and antigravity

Authors: Homer G. Ellis
(Submitted on 19 Nov 2004)

Abstract: The warp drive envisioned by Alcubierre that can move a spaceship faster than light can, with modification, levitate it as if it were lighter than light, even allow it to go below a black hole's horizon and return unscathed. Wormhole-like versions of the author's `drainhole' (1973) might provide the drive, in the form of a by-pass of the spaceship composed of a multitude of tiny topological tunnels. The by-pass would divert the gravitational `ether' into a sink covering part of the spaceship's hull, connected by the tunnels to a source covering the remainder of the hull, to produce an ether flow like that of a river that disappears underground only to spring forth at a point downstream. This diversion would effectively shield the spaceship from external gravity.

[orin stepanek]

Hi Harry! There have been other Ideas on faster than light travel. Like surfing in a bubble that has its own time; separate from the surrounding time. (I don't know if I worded that right.) But nothing has borne fruit. If it ever does; we'll have Flash Gordon and Buck Rogers out roaming the universe; and I'll pack my bags and go first class.

Meanwhile I'll keep watching the universe go by on APOD. 8)

Orin

[harry]

G'day orin

For a minute I thought you said Flesh Gordon,,,,,,,,smile,,and Buck Rogers

[orin stepanek]

G'day orin

For a minute I thought you said Flesh Gordon,,,,,,,,smile,,and Buck Rogers

Hey Harry! is there a movie called Flesh Gordon? Sounds kind of risque. I did indeed say Flash Gordon and Buck Rogers. Two childhood favorites. What I was saying was that if such faster than light inventions were possible that space travel would become a serious factor in human exploration; reaching out beyond the Solar System.

Orin

[Qev]

is there a movie called Flesh Gordon? Sounds kind of risque.

There is, and it is. It's also awful and absolutely hilarious.