http://www.youtube.com/watch?feature=player_embedded&v=xJsUDcSc6hE#!



Answer: a LOT. And there's new ones being discovered all the time, as this fascinating animation by Scott Manley shows.

Created using data from the IAU's Minor Planet Center and Lowell Observatory, Scott's animation shows the progression of new asteroid discoveries since 1980. The years are noted in the lower left corner.

As the inner planets circle the Sun, asteroids light up as they're identified like clusters of fireflies on a late summer evening. The clusters are mainly positioned along the outer edge of Earth's orbit, as this is the field of view of most of our telescopes.

Once NASA's WISE spacecraft begins its search around 2010 the field of view expands dramatically, as well as does the rate of new discoveries. This is because WISE's infrared capabilities allowed it to spot asteroids that are composed of very dark material and thus reflect little sunlight, yet still emit a telltale heat signature.

While Scott's animation gives an impressive - and somewhat disquieting - illustration of how many asteroids there are knocking about the inner Solar System, he does remind us that the scale here has been very much compacted; a single pixel at the highest resolution corresponds to over 500,000 square kilometers! So yes, over half a million asteroids is a lot, but there's also a lot of space out there (and this is just a 2D top-down view too... it doesn't portray any vertical depth.)

While most asteroids are aligned with the horizontal plane of the Solar System, there are a good amount whose orbits take them at higher inclinations. And on a few occasions they even cross Earth's orbit.

An edge-on view of the Solar System shows the positions of asteroids identified by the NEOWISE survey. About 4700 potentially-hazardous asteroids (PHAs) have been estimated larger than 100 meters in size.
As far as how many asteroids there are... well, if you only consider those larger than 100 meters orbiting within the inner Solar System, there's over 150 million. Count smaller ones and you get even more.

I don't know about you but even with the distances involved it's starting to feel a little... crowded.

You can see more of Scott Manley's videos on YouTube here (including some interesting concepts on FTL travel) and learn more about asteroids and various missions to study them here.

Nice post.

There Everywhere!!!!

I see them all day......

Oh.....

wait......

you said assteroids......

didnt ya.......

Nevermind!!!!!!

the perfect Gravity-Weapon!

No matter how many there are found, there are many more to find. The Ort Cloud has so many, we can't even know how many. When two bump together, sometimes one is nudged towards the sun and we get another comet, rock, or whatever.


The Earth will be hit again. The statistics are 100% in favor.

Don't worry, the scientists are keeping us safe as we speak!
http://www.youtube.com/watch?v=cZfsnA7dAHI

There is a good way of establishing a close apporximation of the number of asteroids.

What you do is take their combined weight in the solar systme, the measurement of the the largest one, the definition of the smallest one; then you create an assumption on the distribution of their frequency in each of their sizes or size classes; then you distribute the total weight under the size-class distribution curve, and bang, there is your answer.

I know it won't give an answer to the nearest tenth of a decimal digit, but it will at least give you some idea of a number that you can carry around at coctail parties on a silver platter as it were a blood-soaked sword of impestilence.

they need to find a way to deflect/destroy the ones that could cause trouble for us here...i've read that an ion pulse drive has some good merits, but has yet to be tested

Once the frequency distribution is assumed, the shape of the curve, then to establish the numbers of asteroids under the entire curve you do it this way:

The total weight or volume is 1.

The total area undert he curve is 1.

To total the weight of the pieces under the curve, you would need to take the integral of the curve under its entere domain.

So since you know the total weight, you do an anti-integral on the curve, that is, you take its derivative, plug in the number of the weight, and bang, there is your answer.

for instance,

If the weight or volume of the entire totality of asteroids is W, and the shape of the distribution of the curve is F, then to get the number of pieces you woud do an anti-integral between the twh endpoints, F', and then you would simply solve for


N = (F'(largest X) - f'(smallest x))*W,

where X is the weight of any particular asteroid.

-----------------------

A simpler method would be to assume a distribution function whose median is known, and which is likely to be fitting to the asteroid distribution by weight.

Since we know the median, we can know the number of instances of asteroids by dividing the total weight by the median, which will give us the weight of asteroids if they were all equal, and then divide this number into the total weight, and you get the true number of asteroids (provided we were lucky enough to choose the appropriately-shaped distribution curve.)

How to chose the distribution curve? You can assume that the asteroids are the resultant pieces of 1, or 2, or 3, or N number of broken-up planets after the break-up. You take therefore a piece of rock, or cement, or beton, and smash it up. The rock will fracture, and you assume that the size distribution of the fractures is the same as the remaining pieces of two planets colliding.

This is an experiment you must do before you get to having an idea of the distribution function.

One might object: how dow we know the size distribution is the same, no matter how many planets collide? The answer is simpler than you would think: most similar-size planets break up into pieces of similar size distributions. So if you have 2 similar-sized planets colliding, or a hundred, or a million, you still have the same size-distribution.

What if the planets which were destroyed by collision and are much larger or smaller than the average? Well, this can only go on for a range, because the larger pieces woudl meld into each other, and the smaller pieces would meld into the larger pieces. Only planets of a certain size, rigidity, and comparable inelasticity would cause their own break ups if two of them collided. So the range of the size or mass of broken up one-time planets that gave rise to asteroid formation is narrow.

What is an ion-pulse drive?

I heard that by now Apple has built iOn-plus-pulse drives now too.

Seriously, what's an ion-pulse drive?

Ion Pulse Drive

The Ion Pulse Drive is actually a type of ion propulsion engine, or ion thruster.

I've see the ion engine work in video as a simple science project, a light tethered object charges the air positively to create enough force to generate lift.
Ion Thrusters

There has actually been lots of theory and experimentation with ion thrusters in the 1900's. NASA has been experimenting with them since the 1950's and in 1998 launched Deep Space 1 for a flyby of asteroid 9969 Braille and comet 19P Borrelly powered by an NSTAR Electrostatic Ion Thruster.

Dawn, launched on the 27th of September, 2007, is the first NASA spacecraft on a full exploratory mission to be powered by Ion Propulsion. Dawn accomplished a flyby of Mars on its way to explore the two largest bodies of the asteroid belt, Vesta and dwarf planet Ceres. Dawn should finish its expolration of Vesta in 2012 and move on to orbit Ceres in 2015.

Both Deep Space 1 and Dawn were a bit like Ion Pulse Drives because they used impluses for propulsion, as opposed to a constant thrust, which expends fuel more quickly.

The theory behind the Ion Pulse Drive is to create an engine that positively charges the air with ions and strategically detonate them, creating the ion pulse which is normally only referred to in science fiction movies. Sometimes this is referred to as the ionized field detonation engine.

The theory seems sound. Ion thrusters have been a field of study for the past 100 years. They have been employed as spacecraft propulsion engines for nearly a decade and a half, now. Whether we will see an actual Ion Pulse Drive produced in our lifetime is questionable, since the theory behind this type of drive offers untold, unmatched power.

Theoretically, it could already be in use powering top-secret military aircraft. They say that these things are so fast that once you hear it, it is already too late to see it. Only photos of its unique jet stream are left as evidence in its wake.

How long is a piece of string?

They got that little sucker too!

The earth will be hit by asteroids again and again and again. We can do what we can while civilization is able to protect us but as soon as it falls, and it will (history repeats itself), we would be powerless to control our fate on such a grand scale. Love the present...it's the only thing that's for sure.

"The theory behind the Ion Pulse Drive is to create an engine that positively charges the air with ions and strategically detonate them"

MightyMoe, how does space travel get helped by Ion Pulse Drive? Because as you say, it needs air or an atmoshpere in its immediate vicinity.