Astronomy

Would an object shot from earth fall into the sun?

Would an object shot from earth fall into the sun?


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Would an object shot from earth fall into the sun?

If an object is shot at 107,000 km/h via rocket or otherwise, in the opposite direction to our orbit about the sun, it will be traveling at 0 km/h relative to the sun. The moon is not close enough to the object to have a significant force for the purposes of this question.

Will this object start accelerating towards the sun or will it somehow fall into another stable orbit?

Could it instead get trapped in the L4 Earth-Sun Lagrange point?


Assume that a spacecraft is instantaneously accelerated at the Earth's surface (disregarding the atmosphere for simplicity). We'll consider this from the Sun's reference frame; in other words, the Sun is stationary and the Earth is moving around it.

The spacecraft is accelerated to a velocity which is precisely equal and opposite to the orbital velocity of the Earth around the Sun, making it completely stationary in the instant after the acceleration.

What happens next? Well, we can consider the forces acting on the spacecraft:

  • The Earth's gravity causes a force in the direction of Earth.
  • The Sun's gravity causes a force in the direction of the Sun.

The stationary spacecraft is therefore going to accelerate towards the Earth and towards the Sun. Since the Earth is moving away quickly on its orbital path, the gravitational force is not enough to pull the spacecraft back into an Earth orbit; however, it will nudge the spacecraft into an elliptical orbit.

To demonstrate the situation, I have created a small simulation which can be viewed in a desktop browser. Click here to try the simulation. (You can click "View this program" to check the code, and refresh the page to restart the simulation.)

The simulation is physically accurate (ignoring the effects of other planets), but the spheres have been enlarged for easy interpretation. The Earth is represented as green, while the Sun is orange and the spacecraft is white. Note that, while the spheres representing the spacecraft and Sun intersect, the distance between the two physical objects is always larger than 3.35 solar radii.

This screenshot shows how the spacecraft has been pulled into an elliptical orbit by the Earth:

Finally, we could consider a more realistic scenario where the spacecraft is accelerated until it reaches zero velocity (again, in the Sun's reference frame) at a certain distance from the Earth. At the instant it reaches zero velocity, the engine is stopped.

In this case, the result is essentially the same: there are still forces exerted by the Earth and the Sun, so an elliptical orbit will result. The further the rocket is from the Earth when it reaches zero velocity, the more elliptical the orbit. If the Earth is so far away that its gravity is negligible, the spacecraft will fall directly towards the Sun.


If an object is accelerated away from Earth fast enough that it winds up having no orbital velocity around the Sun, then it will fall radially into the Sun. It's orbital velocity that keeps the object (or the Earth itself) falling around the Sun and not into it. With zero orbital velocity, it simply falls straight down and it can't do anything else (getting trapped at the L4 point requires that it have an orbital motion very nearly the same as Earth's.)


The launch you described is similar to that of the Parker Solar Probe launched August 2018 at 12km/s in a direction opposite Earth's orbital velocity, so it fell toward (rather than into) the Sun, in an elliptical orbit. Its speed at closest approach is expected to be greater than 200km/s


The object will be attracted by the Sun's gravitational pull if the Moon and other planets in the Solar System are far enough that they do not significantly alter the object's speed or direction.


Why doesn't the earth fall down?

The earth does fall down. In fact, the earth is constantly falling down. It's a good thing too, because that is what keeps the earth from flying out of the solar system under its own momentum. Gravity is a centrally attractive force, meaning that objects in a gravitational field always fall towards the source of the gravity. Gravity is caused by mass, so objects with more mass, such as planets and stars, exert a lot of gravity. The earth and everything on it is constantly falling towards the sun because of the sun's immense gravity. This statement is not a metaphor or a play on words. The earth is literally falling towards the sun under its immense gravity.

So why don't we hit the sun and burn up? Fortunately for us, the earth has a lot of sideways momentum. Because of this sideways momentum, the earth is continually falling towards the sun and missing it. Scientists use fancy phrases for this effect such as "stable orbit" or "closed trajectory", but fundamentally what they mean is "falling and missing". All gravitational orbits are actually cases of falling and missing. Astronauts on the International Space Station are not in a no-gravity environment. They are surrounded by the earth's and the sun's immense gravity. More correctly, the astronauts are in a state of free fall. Astronauts in orbit are constantly falling towards the earth and missing it.

Newton had a clever way of explaining the nature of orbits. Consider a cannon on the surface of the earth that shoots a cannonball straight forward. As the ball speeds forward, earth's gravity pulls on it and it falls to the earth until it hits the ground. But the cannonball does not strike the earth at the exact spot it was fired because its forward momentum carries it forward a ways before striking the earth. Now shoot the cannonball again, this time with a higher forward speed. The ball still falls and eventually strikes the earth, but because it has a higher forward speed (sideways, relative to the earth) the ball can cover more distance before striking the earth. If you shoot the ball fast enough, as shown in the picture on the right, it will still fall but will never manage to strike the earth. The earth will curve away faster than the ball can fall towards it. As a result, the ball will continually fall and miss and will end up circling the earth. This is exactly what satellites do. To get an object to orbit the earth, you just have to give it enough sideways speed that it will miss the earth as it falls.

If the earth was not falling around the sun, it would fly wildly out of orbit under its own inertia. The falling trajectory of the earth around the sun, combined with earth's tilt, is what causes the different seasons. All the planets in our solar system are falling around the sun but have enough speed to not hit it. Why are there no objects that do fall right into the sun? There were such objects, put once they fall into the sun, they burn up and become part of the sun. Our solar system is so old, that all rocks and dust clouds without enough speed to miss the sun have long since burned up in the sun.

All objects in the universe are constantly falling. You fall to the earth every time you jump. You and the earth are constantly falling around the sun. You, the earth, and the sun are constantly falling around the center of the galaxy. Why don't we feel all this falling motion? We do experience all this falling, we just don't notice it. The sun is so far away compared to humans, that our falling motion around the sun is very close to a constant speed in a straight line. Interestingly, you can't feel a constant speed in a straight line. Similarly, the galactic center is so far away that our falling motion around the galactic center is very close to a constant speed in a straight line. Our actual trajectory around the galactic center is curved, but the curve is so huge that it is essentially straight on human scales.


Would an object shot from earth fall into the sun? - Astronomy

In reference to "Can I fire a gun on the moon?"-- what then happens to the bullet?

First, we know that the bullet has the same initial velocity on the Moon as it does on the Earth - that is, it exits the gun at the same speed. But as soon as it leaves the gun, it's a different story. First, the Moon bullet doesn't have to contend with air resistance. With so little friction, it can maintain its speed longer than the Earth bullet can. (It's analogous to shooting a hockey puck across ice, which has very little friction, and shooting across sand, which has a lot of friction. The puck will travel a lot farther on the ice!)

Now, there is the issue of gravity. Assuming your bullet doesn't hit anything (a pretty safe bet on the Moon, but don't try this on Earth!) and forgetting about air resistance, the time it takes for the bullet to fall to the ground depends on its initial velocity, the angle at which you shoot it, and the force of gravity.

You can use some basic physics to figure out how far the bullet will fly horizontally and vertically. Say you fire it at some angle "a" (a=0 degrees would correspond to shooting it straight in front of you 90 degrees corresponds to shooting it straight up). It turns out that the bullet's horizontal range - the total distance it travels before gravity wrestles it to the ground - is given by the equation:

g is a measure of the strength of gravity. On Earth, it is 9.8 m/s 2 . To find g on the Moon, we need another equation:

G is the gravitational constant, M is the mass of the Moon, and R is the radius of the Moon. Anyway, on the Moon,

So, neglecting air resistance, the bullet will go about 6 times farther on the Moon than on Earth. Once you take air resistance into account, the Moon bullet has an even bigger advantage!

You might also ask, if the bullet were fired straight up, could it actually escape the moon's gravitational pull and fly off into space? To answer this, we have to compare the moon's "escape velocity" (the minimum velocity an object needs to escape the Moon's gravity) to the bullet's initial velocity. The moon's escape velocity is about 2.38 km/s, but a bullet typically travels at only about 1 km/s. So take cover - even in this case, what goes up must come down!

This page was last updated on September 20, 2015.

About the Author

Kate Becker

With more than a decade of experience as a science writer, Kate Becker has written on a wide variety of science and science policy subjects for web, print, radio, and television, with an emphasis on astronomy and physics. As a researcher for NOVA and NOVA scienceNOW, the nation's premiere science documentary series, Kate investigated everything from human hibernation to invisibility cloaks. She studied physics at Oberlin College and astronomy at Cornell University, and she's had the good fortune to observe with the Arecibo Observatory in Puerto Rico and the Very Large Array in New Mexico, two of the very best places on this pale blue dot of a planet.


Mysterious object seen speeding past sun could be 'visitor from another star system'

A false-colour image of the object, which appears as a faint point of light in the centre. The streaks are stars, caused by the telescope tracking the object. Photograph: Alan Fitzsimmons/Queen’s University Belfast/Isaac Newton Group La Palma

A false-colour image of the object, which appears as a faint point of light in the centre. The streaks are stars, caused by the telescope tracking the object. Photograph: Alan Fitzsimmons/Queen’s University Belfast/Isaac Newton Group La Palma

Last modified on Wed 14 Feb 2018 21.33 GMT

A mysterious object detected hurtling past our sun could be the first space rock traced back to a different solar system, according to astronomers tracking the body.

While other objects have previously been mooted as having interstellar origins, experts say the latest find, an object estimated to be less than 400m in diameter, is the best contender yet.

“The exciting thing about this is that this may be essentially a visitor from another star system,” said Dr Edward Bloomer, astronomer at the Royal Observatory Greenwich.

If its origins are confirmed as lying beyond our solar system, it will be the first space rock known to come from elsewhere in the galaxy.

Published in the minor planet electronic circulars by the Minor Planet Center at the Harvard-Smithsonian Center for Astrophysics, the observations reveal that the object is in a strong hyperbolic orbit – in other words, it is going fast enough to escape the gravitational pull of the sun.

Objects originating from, and on long-period orbits within, our solar system can end up on a hyperbolic trajectory, and be ejected into interstellar space – for example if they swing close by a giant planet, since the planet’s gravity can cause objects to accelerate. But Dr Gareth Williams, associate director of the Minor Planet Center, said that wasn’t the case for the newly discovered body.

“When we run the orbit for this [object] back in time, it stays hyperbolic all the way out – there are no close approaches to any of the giant planets that could have given this thing a kick,” he said. “If we follow the orbit out into the future, it stays hyperbolic,” Williams added. “So it is coming from interstellar space and it is going to interstellar space.”

“If further observations confirm the unusual nature of this orbit, this object may be the first clear case of an interstellar comet,” the report notes. A second report, published later the same day, redesignated the object as an asteroid on account of new analysis of its appearance, giving it the handle A/2017 U1.

According to observations made by astronomers, the object entered our solar system from above, passing just inside Mercury’s orbit and travelling below the sun, before turning and heading back up through the plane of the solar system towards the stars beyond. At its closest, on 9 September, the object was 23.4m miles from the sun.

First spotted earlier this month by a telescope at an observatory in Hawaii, astronomers around the world are now following the path of the object. Among them is Professor Alan Fitzsimmons from Queen’s University Belfast.

“It is fairly certain we are dealing with our first truly identified alien visitor,” he said. Fitzsimmons added that his team is currently working on measuring the objects’ position better to improve calculations of its trajectory, and to gather information relating to its chemical makeup, and size.

Early results, he said, suggest that the object might be similar in make-up to many of those of the Kuiper belt – a region past Neptune in our solar system that contains myriad small bodies.

Bloomer says we should not be too surprised if it does indeed turn out to have come from elsewhere in the galaxy.

“Beyond the planets and past the Kuiper belt we think there is a region called the Oort cloud, which may be home to an astonishing number of icy bodies,” he said.

“Computer models have suggested that disturbances to the Oort cloud do send some stuff in towards the inner solar system, but it would also send stuff outwards as well – so we might be throwing out icy bodies to other star systems.”

If so, Bloomer said, there is no reason to suspect that disturbances to other star systems, as a result of gravitational interactions or other processes, wouldn’t throw material out too. “Just statistically, some of them are going to reach us,” he added.

Williams noted that objects could also be thrown out from the inner region of other solar systems as a result of gravitational interactions with giant planets, casting them into interstellar space.

And Fitzsimmons added that there was another possibility – that the object had been thrown out during the planet-forming period of another solar system.

“We know now that many stars, probably the majority of stars in our galaxy, have planets going around them, and we know from studying those stars but also primarily from studying our own solar system, that planet building is a very messy process,” he said.

With large quantities of material thrown out into interstellar space, said Fitzsimmons, is was expected that there would be objects travelling between the stars.

“This object itself could have been between the stars for millions or billions of years before we spotted it as it plunged into our solar system,” he said.

But, he noted, puzzles remain, not least that Kuiper belt bodies, which are believed to be icy, would give rise to an atmosphere and tail if brought close to the sun.

“There is no evidence that this object has behaved like that, all our data show it as an unresolved point of light, implying it is more like a rocky asteroid than an icy comet,” he said. “There are mysteries to be solved here.”


What Are an Asteroid, a Meteor and a Meteorite?

The terms asteroid, meteor, meteorite and meteoroid get tossed around recklessly, especially when two of them threaten the Earth on the same day. Here's a quick explainer:

An asteroid is a rocky object in space that's smaller than a planet — they're sometimes called minor planets or planetoids, according to NASA. Other sources refer to them loosely as "space debris," or leftover fragments from the formation of the solar system (like the extra pieces that remain after constructing a build-it-yourself bookcase from IKEA).

There are millions of asteroids orbiting the sun, some 750,000 of which are found in the asteroid belt, a vast ring of asteroids located between the orbits of Mars and Jupiter. Asteroids can be as large as hundreds of kilometers wide: The asteroid Ceres, sometimes referred to as a dwarf planet, is 940 km (584 miles) wide.

Asteroids have no atmosphere, but many are large enough to exert a gravitational pull — some, in fact, have one or two companion moons, or they form binary systems, in which two similarly sized asteroids orbit each other.

Scientists are eager to study asteroids because they reveal so much information about the early formation of our solar system some 4.6 billion years ago. One way to study them is to observe them when they come close to Earth, as 2012 DA14 will today (Feb. 15).

A meteor is an asteroid or other object that burns and vaporizes upon entry into the Earth's atmosphere meteors are commonly known as "shooting stars." If a meteor survives the plunge through the atmosphere and lands on the surface, it's known as a meteorite.

Meteorites are usually categorized as iron or stony. As the name implies, iron meteorites are composed of about 90 percent iron stony meteorites are made up of oxygen, iron, silicon, magnesium and other elements.

And meteoroids? That's a general term describing small particles of comets or asteroids that are in orbit around the sun. There's no universally accepted, hard-and-fast definition (based on size or any other characteristic) that distinguishes a meteoroid from an asteroid — they're simply smaller than asteroids.

Only when these objects enter the atmosphere are they referred to as meteors, like the meteor that was seen over Russia today. Because that meteor exploded in the atmosphere, the resulting fireball is known as a bolide. Again, there's no precise definition of a bolide — most astronomers understand a bolide as simply a very bright fireball.


Questions About The Earth

The Ask an Astronomer team's favorite links about The Earth:

    : Downloadable program that lets you explore anywhere on the earth. Easy to use and fascinating! : Wikipedia article about the earth. Loads of great information! : Earth information and facts from the Nine Planets Solar System Tour. : Lots of information and pictures about the aurora, including sighting reports and forcasts. : Lots of great images of Earth are here with accompanying descriptions.

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This Is Why We Don't Shoot Earth's Garbage Into The Sun

Solar orbiters are great ways for studying the Sun, and are part of how we've learned so much about . [+] our Solar System's greatest natural energy source. However, even though the Sun is certainly hot enough to melt and ionize any terrestrial matter we send into contact with it, it's an extraordinarily difficult task to actually send anything, like our garbage, into the Sun.

Imagine our planet as it was for the first 4.55 billion years of its existence. Fires, volcanoes, earthquakes, tsunamis, asteroid strikes, hurricanes and many other natural disasters were ubiquitous, as was biological activity throughout our entire measured history. Most of the environmental changes that occurred were gradual and isolated only in a few instances — often correlated with mass extinctions — were the changes global, immediate, and catastrophic.

But with the arrival of human beings, Earth's natural environment has another element to contend with: the changes wrought upon it by our species. For tens of thousands of years, the largest wars were merely regional skermishes the largest problems with waste led only to isolated disease outbreaks. But our numbers and technological capabilities have grown, and with it, a waste management problem. You might think a great solution would be to send our worst garbage into the Sun, but we'll never make it happen. Here's why.

The very first launch of the Falcon Heavy, on February 6, 2018, was a tremendous success. The rocket . [+] reached low-Earth-orbit, deployed its payload successfully, and the main boosters returned to Cape Kennedy, where they landed successfully. The promise of a reusable heavy-lift vehicle is now a reality, and could lower launch costs to

$1000/pound. Still, even with all these advances, we won't be launching our garbage into the Sun anytime soon.

Jim Watson/AFP/Getty Images

At present, there are a little more than 7 billion humans on the planet, and the previous century saw us at last become a spacefaring civilization, where we've broken the gravitational bonds that have kept us shackled to Earth. We've extracted valuable and rare minerals and elements, synthesized new chemical compounds, developed nuclear technologies, and produced new technologies that far exceed even the wildest dreams of our distant ancestors.

Although these new technologies have transformed our world and improved our quality of life, there are negative side-effects that have come along for the ride. We now have the capacity to cause widespread damage and destruction to our environment in a variety of ways, from deforestation to atmospheric pollution to ocean acidification and more. With time and care, the Earth will begin self-regulating as soon as we stop exacerbating these problems. But other problems just aren't going to get better on their own on any reasonable timescale.

Nuclear weapon test Mike (yield 10.4 Mt) on Enewetak Atoll. The test was part of the Operation Ivy. . [+] Mike was the first hydrogen bomb ever tested. A release of this much energy corresponds to approximately 500 grams of matter being converted into pure energy: an astonishingly large explosion for such a tiny amount of mass. Nuclear reactions involving fission or fusion (or both, as in the case of Ivy Mike) can produce tremendously dangerous, long-term radioactive waste.

National Nuclear Security Administration / Nevada Site Office

Some of what we've produced here on Earth isn't merely a problem to be reckoned with over the short-term, but poses a danger that will not significantly lessen with time. Our most dangerous, long-term pollutants include nuclear by-products and waste, hazardous chemicals and biohazards, plastics that off-gas and don't biodegrade, and could wreak havoc on a significant fraction of the living beings on Earth if they got into the environment in the wrong way.

You might think that the "worst of the worst" of these offenders should be packed onto a rocket, launched into space, and sent on a collision course with the Sun, where at last they won't plague Earth anymore. (Yes, that was similar to the plot of Superman IV.) From a physics point of view, it's possible to do so.

But should we do it? That's another story entirely, and it begins with considering how gravitation works on Earth and in our Solar System.

The Mercury-bound MESSENGER spacecraft captured several stunning images of Earth during a gravity . [+] assist swingby of its home planet on Aug. 2, 2005. Several hundred images, taken with the wide-angle camera in MESSENGER's Mercury Dual Imaging System (MDIS), were sequenced into a movie documenting the view from MESSENGER as it departed Earth. Earth rotates roughly once every 24 hours on its axis and moves through space in an elliptical orbit around our Sun.

Human beings evolved on Earth, grew to prominence on this world, and developed extraordinary technologies that our corner of the cosmos had never seen before. We all have long dreamed of exploring the Universe beyond our home, but only in the past few decades have we managed to escape the gravitational bonds of Earth. The gravitational pull exerted by our massive planet is only dependent on our distance from Earth's center, which causes spacetime to curve and causes all objects on or near it — including humans — to constantly accelerate "downwards."

There's a certain amount of energy keeping any massive object bound to Earth: gravitational potential energy. However, if we move fast enough (i.e., impart enough kinetic energy) to an object, it can cross two important thresholds.

  1. The threshold of a stable orbital speed to never collide with Earth: about 7.9 km/s (17,700 mph).
  2. The threshold of escaping from Earth's gravity entirely: 11.2 km/s (25,000 mph).

It takes a speed of 7.9 km/s to achieve "C" (stable orbit), while it takes a speed of 11.2 km/s for . [+] "E" to escape Earth's gravity. Speeds less than "C" will fall back to Earth speeds between "C" and "E" will remain bound to Earth in a stable orbit.

Brian Brondel under a c.c.a.-s.a.-3.0 license

For comparison, a human at the equator of our planet, where Earth's rotation is maximized, is moving only at about 0.47 km/s (1,000 mph), leading to the conclusion that we're in no danger of escaping unless there's some tremendous intervention that changes the situation.

Luckily, we've developed just such an intervention: rocketry. To get a rocket into Earth's orbit, we require at least the amount of energy it would take to accelerate that rocket to the necessary threshold speed we mentioned earlier. Humanity has been doing this since the 1950s, and once we've escaped from Earth, there was so much more to see occurring on larger scales.

Earth isn't stationary, but orbits the Sun at approximately 30 km/s (67,000 mph), meaning that even if you escape from Earth, you'll still find yourself not only gravitationally bound to the Sun, but in a stable elliptical orbit around it.

The Dove satellites, launched from the ISS, are designed for Earth imaging and have numbered . [+] approximately 300 in total. There are

130 Dove satellites, created by Planet, that are still in Earth's orbit, but that number will drop to zero by the 2030s due to orbital decay. If these satellites were boosted to escape from Earth's gravity, they would still orbit the Sun unless they were boosted by much greater amounts.

This is a key point: you might think that here on Earth, we're bound by Earth's gravity and that's the dominant factor as far as gravitation is concerned. Quite to the contrary, the gravitational pull of the Sun far exceeds the gravitational pull of Earth! The only reason we don't notice it is because you, me, and the entire planet Earth are in free-fall with respect to the Sun, and so we're all accelerated by it at the same relative rate.

If we were in space and managed to escape from Earth's gravity, we'd still find ourselves moving at approximately 30 km/s with respect to the Sun, and at an approximate distance of 150 million km (93 million miles) from our parent star. If we wanted to escape from the Solar System, we'd have to gain about another 12 km/s of speed to reach escape velocity, something that a few of our spacecraft (Pioneer 10 and 11, Voyager 1 and 2, and New Horizons) have already achieved.

The escape speed from the Sun at Earth's distance is 42 km/s, and we already move at 30 km/s just by . [+] orbiting the Sun. Once Voyager 2 flew by Jupiter, which gravitationally 'slingshotted' it, it was destined to leave the Solar System.

Wikimedia Commons user Cmglee

But if we wanted to go in the opposite direction, and launch a spacecraft payload into the Sun, we'd have a big challenge at hand: we'd have to lose enough kinetic energy that a stable elliptical orbit around our Sun would transition to an orbit that came close enough to the Sun to collide with it. There are only two ways to accomplish this:

  1. Bring enough fuel with you so that you can decelerate your payload sufficiently (i.e., have it lose as much of its relative speed with respect to the Sun as possible), and then watch your payload gravitationally free-fall into the Sun.
  2. Configure enough fly-bys with the innermost planets of our Solar System — Earth, Venus and/or Mercury — so that the orbiting payload gets de-boosted (as opposed to the positive boosts that spacecraft like Pioneer, Voyager, and New Horizons received from gravitationally interacting with the outer planets) and eventually comes close enough to the Sun that it gets devoured.

The idea of a gravitational slingshot, or gravity assist, is to have a spacecraft approach a planet . [+] orbiting the Sun that it is not bound to. Depending on the orientation of the spacecraft's relative trajectory, it will either receive a speed boost or a de-boost with respect to the Sun, compensated for by the energy lost or gained (respectively) by the planet orbiting the Sun.

Wikimedia Commons user Zeimusu

The first option, in reality, requires so much fuel that it's practically impossible with current (chemical rocket) technology. If you loaded up a rocket with a massive payload, like you might expect for all the hazardous waste you want to fire into the Sun, you'd have to load it up with a lot of rocket fuel, in orbit, to decelerate it sufficiently so that it'd fall into the Sun. To launch both that payload and the additional fuel requires a rocket that's larger, more powerful and more massive than any we've ever built on Earth by a large margin.

Instead, we can use the gravity assist technique to either add or remove kinetic energy from a payload. If you approach a large mass (like a planet) from behind, fly in front of it, and get gravitationally slingshotted behind the planet, the spacecraft loses energy while the planet gains energy. If you go the opposite way, though, approaching the planet from ahead, flying behind it and getting gravitationally slingshotted back in front again, your spacecraft gains energy while removing it from the orbiting planet.

The Messenger mission took seven years and a total of six gravity assists and five deep-space . [+] maneuvers to reach its final destination: in orbit around the planet Mercury. The Parker Solar Probe will need to do even more to reach its final destination: the corona of the Sun. When it comes to reaching for the inner Solar System, spacecraft are required to lose a lot of energy to make it possible: a difficult task.

Two decades ago, we successfully used this gravitational slingshot method to successfully send an orbiter to rendezvous and continuously image the planet Mercury: the Messenger mission. It enabled us to construct the first all-planet mosaic of our Solar System's innermost world. More recently, we've used the same technique to launch the Parker Solar Probe into a highly elliptical orbit that will take it to within just a few solar radii of the Sun.

A carefully calculated set of future trajectories is all that's required to reach the Sun, so long as you orient your payload with the correct initial velocity. It's difficult to do, but not impossible, and the Parker Solar Probe is perhaps the poster child for how we would, from Earth, successfully launch a rocket payload into the Sun.

Keeping all this in mind, then, you might conclude that it's technologically feasible to launch our garbage — including hazardous waste like poisonous chemicals, biohazards, and even radioactive waste — but it's something we'll almost certainly never do.

Why not? There are currently three barriers to the idea:

  1. The possibility of a launch failure. If your payload is radioactive or hazardous and you have an explosion on launch or during a fly-by with Earth, all of that waste will be uncontrollably distributed across Earth.
  2. Energetically, it costs less to shoot your payload out of the Solar System (from a positive gravity assist with planets like Jupiter) than it does to shoot your payload into the Sun.
  3. And finally, even if we chose to do it, the cost to send our garbage into the Sun is prohibitively expensive at present.

This time-series photograph of the uncrewed Antares rocket launch in 2014 shows a catastrophic . [+] explosion-on-launch, which is an unavoidable possibility for any and all rockets. Even if we could achieve a much improved success rate, the risk of contaminating our planet with hazardous waste is prohibitive for launching our garbage into the Sun (or out of the Solar System) at present.

The most successful and reliable space launch system of all time is the Soyuz rocket, which has a 97% success rate after more than 1,000 launches. Yet a 2% or 3% failure rate, when you apply that to a rocket loaded up with all the dangerous waste you want launched off of your planet, leads to the catastrophic possibility of having that waste spread into the oceans, atmosphere, into populated areas, drinking water, etc. This scenario doesn't end well for humanity the risk is too high.

Considering that the United States alone is storing about 60,000 tons of high-level nuclear waste, it would take approximately 8,600 Soyuz rockets to remove this waste from the Earth. Even if we could reduce the launch failure rate to an unprecedented 0.1%, it would cost approximately a trillion dollars and, with an estimated 9 launch failures to look forward to, would lead to over 60,000 pounds of hazardous waste being randomly redistributed across the Earth.

Unless we're willing to pay an unprecedented cost and accept the near-certainty of catastrophic environmental pollution, we have to leave the idea of shooting our garbage into the Sun to the realm of science fiction and future hopeful technologies like space elevators. It's undeniable that we've made quite the mess on planet Earth. Now, it's up to us to figure out our own way out of it.


Infall to a point source of gravity Edit

The time to traverse half the distance R, which is the infall time from R along an eccentric orbit, is the Kepler time for a circular orbit of R/2 (not R), which is (1/32) 1/2 times the period P of the circular orbit at R. For example, the time for an object in the orbit of the Earth around the Sun, to fall into the Sun if it were suddenly stopped in orbit, would be P / 32 >> , where P is one year. This is about 64.6 days.

Infall of a spherically-symmetric distribution of mass Edit

where the volume of a sphere is: ( 4 / 3 ) π R 3 . >.>

where the latter is in SI units.

This result is exactly the same as from the previous section when : M ≫ m .

The free-fall time is a very useful estimate of the relevant timescale for a number of astrophysical processes. To get a sense of its application, we may write

Here we have estimated the numerical value for the free-fall time as roughly 35 minutes for a body of mean density 1 g/cm 3 .

For an object falling from infinity in a capture orbit, the time it takes from a given position to fall to the central point mass is the same as the free-fall time, except for a constant 4 3 π <3pi >>> ≈ 0.42.


Would an object shot from earth fall into the sun? - Astronomy

Why do the planets rotate around the Sun?

First, please note that "rotate" actually is used to describe an celestial body's spin, and "revolve" is used to describe its orbital motion. For example, the Earth completes one rotation about its axis about every 24 hours, but it completes one revolution around the Sun about every 365 days.

Anyway, the basic reason why the planets revolve around, or orbit, the Sun, is that the gravity of the Sun keeps them in their orbits. Just as the Moon orbits the Earth because of the pull of Earth's gravity, the Earth orbits the Sun because of the pull of the Sun's gravity.

Why, then, does it travel in an elliptical orbit around the Sun, rather than just getting pulled in all the way? This happens because the Earth has a velocity in the direction perpendicular to the force of the Sun's pull. If the Sun weren't there, the Earth would travel in a straight line. But the gravity of the Sun alters its course, causing it to travel around the Sun, in a shape very near to a circle. This is a little hard to visualize, so let me give you an example of how to visualize an object in orbit around the Earth, and it's analogous to what happens with the Earth and the Sun.

Imagine Superman is standing on Mt. Everest holding a football. He throws it as hard as he can, which is incredibly hard because he's Superman. Just like if you threw a football, eventually it will fall back down and hit the ground. But because he threw it so hard, it goes past the horizon before it can fall. And because the Earth is curved, it just keeps on going, constantly "falling," but not hitting the ground because the ground curves away before it can. Eventually the football will come around and smack Superman in the back of the head, which of course won't hurt him at all because he's Superman. That is how orbits work, but objects like spaceships and moons are much farther from the Earth than the football that Superman threw. (We're ignoring air resistance with the football example actual spacecraft must be well above most of a planet's atmosphere, or air resistance will cause them to spiral downward and eventually crash into the planet's surface.) This same situation can be applied to the Earth orbiting the Sun - except now Superman is standing on the Sun (which he can do because he's Superman) and he throws the Earth.

The next question, then, is how did Earth get that velocity, since in real life there's no Superman throwing it. For that, you need to go way back to when the Solar System formed.

This page was last updated on January 31, 2016.

About the Author

Cathy Jordan

Cathy got her Bachelors degree from Cornell in May 2003 and her Masters of Education in May 2005. She did research studying the wind patterns on Jupiter while at Cornell. She is now an 8th grade Earth Sciences teacher in Natick, MA.


Where did the Chinese rocket land?

The Long March 5B rocket safely plunged into the Indian Ocean at a point 72.47° East and 2.65° North in the early hours of Sunday, May 9, 2021.

The world watched on in fear amid concerns the rocket would hit a highly populous area after Chinese authorities lost the ability to control its re-entry.

But China's space agency announced the rocket likely landed in the Indian Ocean, just west of the Maldives after most of its structure burned up when reentering the atmosphere.

It re-entered the atmosphere at 10:24am Beijing time.

It is unclear if any debris made landfall - a theory fuelled by US Space Command, who merely said it was "unknown if the debris [had] impacted land or water".

They also did not confirm the landing spot reported by Chinese media, instead saying the rocket had "re-entered over the Arabian Peninsula".

There have been no reports of injuries or damage so far.