## Solution to Joe Drops the Ball

In two previous blog posts about Newton’s Cannon and Joe Drops the Ball I posed the question: If falling objects go faster and faster, why don’t orbiting objects fall out of orbit and crash to the ground?
The question is legitimate and also has a perfectly legitimate explanation.
The rate of a falling object is 32.2 feet per second per second, i.e. it goes faster and faster as it goes down. It accelerates on the way to the ground. So the first question is this: 1) Is an object in orbit in free fall? The answer is yes. 2) Do falling objects accelerate as they fall to the ground? The answer is yes. 3) Do orbiting objects accelerate and thus fall to the ground? The answer is no.
It’s all in the definition of accelerate. Acceleration is a change in velocity not just a change in speed. Velocity is the speed in a given direction, but because an object in orbit is always changing direction it is technically accelerating even if it’s speed isn’t changing.
The force of gravity bending the forward motion of the orbiting object changes the direction of the object. The object is accelerating even if it’s speed isn’t changing, because it is constantly changing direction.
This is alternatively explained in the article I wrote called The Little Rocket that Was.

## Can time travel happen, even if it's a century from now?

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.