Because of Joe’s ball, the Earth may fall into the sun and the moon may fall from the sky.
Meet Joe. Joe has a ball, and his ball is a great problem for the whole world.
Because of Joe’s ball, the Earth may fall into the sun and the moon may fall from the sky. That’s a big problem for a small ball in Joe’s hand.
The problem is that Joe drops his ball and then tosses it to the side (see illustration at right).
You see, when Joe drops his ball it accelerates at a spectacular rate of 32.2 feet per second per second.
Joe’s ball, as does any falling object, doesn’t just drop. It drops faster and faster, whether he just drops it, or tosses it to the side! If he tosses it to the side, it will hit the ground at the same time as if he just dropped it. The forward movement of the ball doesn’t slow down the downward acceleration of the ball toward the ground. (We are assuming here, that there’s no wind or air to slow it down, okay? Just leave that out for now.)
Now, Let’s say Joe has a bullet in his hand and drops his bullet. Like the ball, the bullet’s gonna fall to the ground at the same rate the ball did.
Let’s next give Joe a gun, and have him shoot the bullet. The bullet is going forward, just like the ball that Joe tossed. But the forward movement of the bullet from the gun barrel doesn’t slow the downward acceleration of the bullet as it falls to the ground. It just falls to the ground a ways off because the bullet was going fast.
Finally, Sir Isaac Newton shoots a cannon. And his cannon is very powerful. The cannonball goes so fast, so far, that as it falls to the ground, the ground curves away underneath it, and it goes around the world in an orbit.
But why? Both the ball and the bullet fall to the ground at 32.2 feet per second per second. They accelerate toward the ground, but Isaac Newton’s cannonball doesn’t. Satellites stay in orbit, the moon stays in orbit, the Earth stays in orbit, and they don’t accelerate toward the ground. How come?
The Earth is falling into the sun and the moon is falling from the sky.
Once upon a time, Sir Isaac Newton had a cannon. Noisy thing that. Orbitologists call the figurative device “Newton’s cannon.”
I managed to borrow one of these cannons from the National Museum of Orbitology and Conjecturism, and am standing next to a large pile of cannonballs (see image).
Depending on all sorts of factors, like how much gunpowder, how big the cannonball, etcetera, I’ve discovered the cannonball leaves the cannon around 1440 feet per second. Alas, after leaving the cannon, the speeding cannonball gets affected by wind, gravity and distance it has to travel.
The first factor is the wind resistance. At 1440 feet per second on a calm day, the spherical ball of lead immediately encounters 1440 feet per second wind resistance in the opposite direction of flight. The cannonball’s gonna slow down.
The second factor is gravity. No matter how fast that thing travels through the air, it’s still going to fall toward the ground for the same reason we plant our feet here. Gravity.
A third factor, I suppose, is if we’re shooting at a target or just an open space to see how far the ball will travel. Since I want to see how far the ball will go, I’m in an open field.
A fourth factor is trajectory. Am I shooting level to the ground, or in a big arc? Obviously it’s going to travel farther if I angle the barrel of the cannon up and shoot the ball in a big arc. So what to do? Let’s just put a level on the barrel and shoot it parallel to the ground to see how far the projectile is going to travel before wind resistance and gravity pull that hurdling ball of metal down to the unyielding ground below and then it bounces and rolls until it comes to a halt.
Now that we’ve fired the cannonball, let’s take a tape measure and see how far it went before it hit the ground. Surprising distance it seems for such a big heavy object. I wonder if we could make it go any farther?
This is the example of Newton’s Cannon. Given a condition of no atmosphere, and enough speed, that ball would travel around the curve of the earth, hitting further and further away from us. Speed it up even more and it will never hit the ground (see illustration).
That’s an orbit.
Umm….wait. Something’s seriously wrong here. My brain puts up red flags. I’m a layman, not a real scientist, so what do I really know about physics and all that stuff. I’m a buff isn’t it enough? Seems to me that a falling object should accelerate, not just fall at a constant speed. Seems to me the rate of acceleration of a falling object is (Googling it now) 9.8 m/s/s. “Free-falling objects are in a state of acceleration. Specifically, they are accelerating at a rate of 9.8 m/s/s. This is to say that the velocity of a free-falling object is changing by 9.8 m/s every second.” –physicsclassroom.com
So the cannonball should not just curve around with the curve of the earth, but accelerate downward as it falls, thus never achieving orbit and always hitting the ground. Therefore nothing can orbit anything and the moon can’t stay in the sky and the Earth is going to fall into the sun. The International Space Station is doomed tomorrow and all the GPS satellites are going to fall down. Forget about Dish Network, DirectTV, SeriusXM Radio, weather satellites and Google Earth. It’s all coming down.
Well, obviously wrong, but why wrong? This is a question this layman has pondered over many an hour sitting in pondering places at various pondering moments in this pondering life. I suppose I’m going to have to just ponder up another Google search. I will ask this question another way posted here, and after you read that one you can read here and then here!
I have written a few answers about this topic already and this one might end up TL;DR but what the heck, Here goes.
By Chris Craddock
I originally wrote: “No. Nobody can convince you that time travel can happen because it really can’t happen. Not in the sci-fi sense everybody seems to long for. We are all “traveling” forwards into the future at an eye popping rate of 1 second per second. We can’t go forwards any faster than that and we can’t EVER go backwards in time. Bottom line, time travel isn’t possible. ”
Then David Chidakel asked “I would like to hear your reasoning”. I started to answer David in the comment section but my answer got quite long, so I decided to edit my original post instead. I have written a few answers about this topic already and this one might end up TL;DR but what the heck, Here goes. Time’s arrow…
Some physics equations seem not to care about the sign of the time variable, or in many cases not to care about time at all. If you suspend disbelief for a moment, they seem to allow for “closed time-like curves” and quantum entanglements which is geek code for “time travel”. But those are only hypothetical quantum scale effects. They probably don’t work out when considered in conjunction with other known physical laws and certainly don’t work for massive objects like people and time machines.
First of all, let’s dispose with time travel into the past… that is ruled out by thermodynamics. First (law): just for grins and giggles let’s assume a time lord has invented a blue box that somehow instantaneously leaps the traveler back to some particular time and place in the past (relative to the traveler’s rest frame yada yada) where/when the travelers step out of the box and start interacting with the universe and alien creatures as they were back then.
But atoms/subatomic particles and their constituent energy fields are pretty tough things. They might get smashed in an accelerator or reactor, or be fused inside a star or have their electrons torn off inside a 9v battery along the way, but for the most part they are eternal and indestructible. Certainly within your own lifetime your atoms belong to you and only to you.
The problem then is that instantly upon arrival all of the atoms making up the traveler and his/her time machine would suddenly have to exist in two places at the same time: Inside the traveler (obviously) and ALSO inside whatever those same atoms happened to be contained within at that exact moment in the past. That can’t happen. If it could the whole edifice of physical laws would fall apart. So strike one. Second (law): a.k.a. “entropy always wins”. The universe is made up of atoms/energy fields each more or less randomly going about its business. At any given moment we can’t even know everything there is to know (position, momentum etc) about a single atom (according to Heisenberg and half a dozen other quantum laws) -AND EVEN WORSE- a moment later even that information is lost.
So no matter how much energy you’re willing to expend, there is simply NO way to rearrange all of the particles in the universe back to some prior state. The information about that state doesn’t I have written a few answers about this topic already and this one might end up TL;DR but what the heck, Here goes.I have written a few answers about this topic already and this one might end up TL;DR but what the heck, Here goes.exist. Fried eggs can’t become fresh unbroken eggs no matter what you do. So even if you can decide “when” to go back to, there is no “there” to go back to. Strike two. Third (admittedly just a thought experiment): While we know that time and space are entangled from a relativistic point of view, they are not the same thing. If time was just another dimension that you could (somehow) independently move along like a bead on a wire, then perhaps you could just pop out of the blue box and the universe would be sitting there exactly as it was “before”.
But whose version of “before” are we talking about? There is no universal time reference. That line of reasoning leads to grandfather paradoxes and infinite regression. If we supposed for a moment that it could happen, how could you ever tell? Aside from the violent anti-matter annihilation of the travelers atoms 🙂 I imagine the rest of the universe would simply carry on exactly the way it did last time. So logically it can’t happen. Strike three.
Now let’s think about time travel to the future. This also fails the thought experiment above.
The Future Now let’s think about time travel to the future. This also fails the thought experiment above. In gross details if we look at (say) a tennis ball in motion right now and we know its position and velocity and mass and angular momentum and air density etc, we can predict its future position quite accurately for a short time O(seconds). Beyond that, we just can’t predict its future. What happens to the ball next week, or in a hundred years from now? How about the position and momentum of every atom in a nearby star or the couple of hundred billion of its cousins in our galaxy?
Time travel to the future isn’t possible because the future has not happened yet. Which future would be traveling to? Our blue box can’t slide the travelers time bead along the wire of the time axis because we just proved (above) that there IS no wire. And the blue box can’t rearrange the entire universe’s atoms into some as yet unseen future state because it can’t predict what that state will be, even if it had the means to rearrange them to its desired state.
Mars is cool. Isn’t it? Well, spoiler alert: neither you nor I are going to settle on Mars. It’s inhospitable and has no benefit. It’s not a safe haven if we screw up Earth. Why? Because Mars lost its hot core billions of years ago. Without a hot core Mars lost the magnetic field shielding it from the sun. The atmosphere blew away, the volcanos dried up, and there’s nothing protecting any people there from the dangerous rays of the sun. It has no value for humans to go there, what to speak live there, and NASA has a whole department dedicated to making sure we don’t bring germs to other planets or from other planets back to Earth. That means we’ll never terraform Mars. We will never grow stuff there, and we will never survive there. Mars is useless except, maybe, for rovers to rove. Same goes for the moon. No point in going back to the moon. Anything you want to do there you can do without human hands. That’s what robots are for, and if a robot dies it costs money but no lives. We were born on this Earth. We will die on it. We’ve got stuff in orbit, and robots on Mars and in space, but that’s it. Maybe SpaceX or somebody will put some poor souls on the surface of Mars, but they will either die or have to come back to the safety of Earth. There will be no Star Trek Enterprise. There will never be a spaceship that can go “warp” speed. There will never be a Federation of Planets. Get real. Sorry if it’s upsetting. Great TV, great movies, but it’s science fiction. We won’t be able to visit those 7 “earthlike planets” recently discovered over 40 light years away, 10 times further than our closest stellar neighbor. We’ve got one place to live. Earth. Screw it up, and the future’s screwed. We have the science to sustain it, but greediness and politics, international conflicts and third world governments, big industry and you and me in our cozy environment choking homes, will not allow us to save it. Gradually a wide variety of species will go extinct, both plants and animals. Gradually the food chain will be disrupted. Not for you, probably not for your kids, but down the line it’s coming. Sometimes Earth people go “green” – reducing their “environmental footprint.” Yeah, you can try. You can even succeed if you try really hard. You can live off the grid, by candlelight or self generated electricity, don’t buy any food in containers or wrapped in plastic, make compost and grow food. I know people who live like that and it’s great for them. However, let’s get real here. Out of billions of people, if a few people leave less of an environmental footprint than most of the others, it might make them feel good but will it really save the world? No it won’t, because at the core of the problem is humanity itself. We are the polluters of our own planet. We are not likely to stop as a whole. We are not one world government, one people and one culture. We are diverse and dream of going to other planets if this one gets screwed up. Is this a pessimistic view? Probably. I’m going to be 64 years old in a few months. This is the world the boomers and those before us are leaving behind. See if you can fix it.
By Wayne E. Boyd Breaking news. Astrophysicists have discovered a new planet within the “Goldilocks” region orbiting a yellow dwarf star and believe it is teaming with life, thus putting to rest the age-old question: “Is there life on other planets?” The planet appears to be similar to our own in size and has an atmosphere primarily of oxygen and nitrogen. However, don’t plan on visiting the new world anytime soon. Not only is it many light years away, but microbial life floating in the wind would be a death trap without a spacesuit since we have never developed evolutionary immunity against them. Observations suggest the surface of the planet is mostly submerged under salt-water oceans which themselves are full of aquatic life of all sizes. The areas that rise above the oceans, approximately 25% of the planet surface, are covered with plant life which provide food for many of the animals that live there. Evidence indicates the dry land areas are inhabited mainly by germs and insects, however quadrupeds and bipeds live among them. The bipeds appear to be polluting their own air and water due to advanced industrial revolution. Great cities have arisen all over the land and the bipeds appear to have launched satellites and probes into space. Unfortunately, they quarrel and kill each other and share no common interests with their environment. The planet is located inside the neighboring Milky Way Galaxy, which can be seen from our own Andromeda Galaxy with the naked eye in the night sky, and appears brilliant when seen through even modest telescopes. Tentatively the planet, has been named “Earth” and due to the circumstances may be barren of all life within a few thousand years. It has been classified as dangerous for habitation and the search for intelligent life on other worlds continues.
Out there, in the night sky, you can see a bunch of twinkling stars with your naked eye, or in my case, with my prescription eyeglasses on my face. Our atmosphere makes them twinkle. In space they don’t twinkle.
They twinkle, and they move too. Really quickly it turns out. Right across the sky in a big arc.
I tried to look at Saturn once through an ordinary backyard telescope. I saw it – rings and all. However, it was moving past the field of vision with stupendous rapidity. That means really fast. You’d be surprised. I tried to photograph it, but I needed a long exposure to capture the dim light, and it came out a blur because Saturn moved. It just slid right out of view lickety-split.
Yeah, it’s in orbit around the sun and all, but that’s not the problem. The problem is our dizzying rotation around the Earth’s axis – that pesky little problem that makes a day only 24 hours. At the equator you’re traveling fast and far, and not in a straight direction. We’re spinning like a top. A man in Equador goes 24,901 miles a day at over a thousand miles per hour. In a big circle.
That spinning gyroscope known as Earth is why the sun rises and sets, why the stars spin by above us, and why I couldn’t photograph Saturn that night.
But are we affected by centrifugal force by all this spinning around and around? Well, it turns out that at the equator your weight is reduced by one third of a percent because of it. The further north or south you go from the equator, the less this effect is felt.
Additionally, the earth isn’t a perfect sphere. All this spinning around the axis has warped the shape of Earth. Our planet is fatter at the equator. We call that equatorial bulge. So somebody standing on the equator weighs 1/3 of 1 percent less because of centrifugal force, and another 1/5 of one percent being further from the center mass of the planet.
So if you’re interested in weight loss but diet and exercise isn’t your thing, go to the equator, where you’ll weigh about a half of a percent less than you do at the poles. That explains why Santa Claus weighs more at the North Pole than he would at the equator, and why he lives at the top of the world.
Astronomers believe most stars are part of binary systems rather than solo systems. A binary system means two stars orbiting each other.
They think Pluto is somewhat of a binary object with its inordinately large moon. The center of gravity between the two is outside Pluto itself.
Similarly, in a binary star system you have two stars going around a center of gravity that lies somewhere between the two of them but outside the sphere of either.
This happens a lot in space. Even here on Earth our own moon is relatively large. This is one of several explanations for the Earth’s wobble (along with droughts) and certainly why the moon wobbles. When that wobble becomes such that essentially both objects wobble around each other that’s a binary system.
Such bodies can be two stars, two planets or even two black holes that revolve around each other. Even a galaxy behaves in such a way that the stars orbit a center of gravity outside of themselves.
Recently astrophysicists have even wondered whether our own sun is part of a binary system revolving around an unknown brown dwarf hiding somewhere in the Oort Cloud.
But binary systems are only part of the story. Out there where no man has gone before there are trinary systems or even more.
The universe is not well understood though we like to think we know more than we do. There are great mysteries out there we may never understand.
There’s no way humans are going to colonize Mars. Hate to burst your bubble.
There’s no organized magneto sphere on Mars to protect people from the sun. It’s why the Martian atmosphere blew away and the oceans evaporated.
For that reason terra forming can’t be successful there, and scientifically no one wants to contaminate Mars with our germs.
We’re just going to have to fix what we’ve got. Star Trek is fiction.