From Radar Online:
The right-wingers who think nothing but the worst of Cindy Sheehan probably won't change their minds after reading Peace Mom. In the book, which hits bookstores September 19, the antiwar icon admits she has fantasized about going back in time and killing the infant George W. Bush, thereby preventing the Iraq War.
What if Cindy Sheehan could go back in time? If she succeeded at murdering the infant George W Bush in 1946, then the Iraq War would never have happened (or so she thinks). If there was no Iraq War, Casey Sheehan would be alive, and she would never have gone back in time. But if she didn't go back in time, George W Bush would have lived to become president, and the war would have happened...
This is called a paradox.
Most physicists believe a paradox can never happen. The universe doesn't allow it.
If Cindy Sheehan had gone back in time, and managed to be in the same room as George W Bush, and prepared to smash the baby's skull with a brick, Bush would survive. How? Simple. Skippy the Wonder Dog would have leapt up at that precise moment to spoil her attack.
Or someone would have entered the room for the baby's scheduled feeding.
Or she would have dropped the brick on her foot and broken her toe, attracting attention.
Or something else would have gone wrong. Something had to go wrong, because George W Bush was not killed.
Imagine it this way. (This example came from a book on the physics of time travel, the name of which evades me right now. If you are interested, I'll be updating this post later when I have a chance to find the book.)
Your have a time machine consisting of a tube with two ends. Something entering one end pops out the other exactly a half-second earlier. The two ends of the time machine are connected to pockets of a pool table. You decide to construct a paradox and so cause the universe to unravel. You are going to sink the ball in the pocket at the entrance of the time machine, but you've exquisitely calculated your shot such that when the ball emerges from the machine, it will cross the table and knock its earlier self -- the one still on its way to the machine -- off course. The ball won't enter the pocket, and you'll have the paradox of two balls in the present, one of which has no origin.
Poof! The universe dissolves as a result.
What really happens? You take your shot, the ball emerges, it hits the earlier version of itself, but only grazes it. It still manages to get into the pocket. Every time.
OK, you figure you can still destroy the universe. You construct a special ball that is actually an explosive. It is armed after being struck, and it is designed to explode at the slightest touch afterward. Now if the ball suffers even just a grazing touch from itself, it will explode, and so not enter the time machine, creating a paradox.
You take your shot. You look at the exit of the time machine, but to your horror, no ball exits. Instead a piece of star-shaped shrapnel comes winging out. It strikes the ball that is still on its way to the time machine entrance. The ball explodes, and even as the pieces fly everywhere, you see a piece of star-shaped shrapnel flying into the entrance of the time machine.
No paradox. Reality is safe.
Really, this was just an excuse to talk about time travel. But it was also meant to be instructive. The First Law of Temporal Imaginings is this: "If it happened, it happened." There is nothing you can do about it. Indeed, if you could go back in time, you would find out that whatever you did was just part of what happened. You just didn't realize that it was you that the newspapers were refering to when they wrote about the mysterious stranger wielding a brick who was picked up by police trying to break into the Bush residence on July 7, 1946, the day after George W Bush was born. Fortunately, according to the news reports, the Bushes left exactly one half-hour earlier. You see, you forgot to correct for Daylight Saving Time and add an extra hour to your time machine settings. When you left the the present 5pm on December 31, 2006, you set the machine to go back 530,208 hours, expecting to appear at 5pm on July 7, 1946, but really it's 6pm according to the local clock. Your plan to sneak in and murder the Bush child has failed. Like I said, something always goes wrong.
Or in the words of Ashleigh Brilliant, "Nothing we can do can change the past, but everything we do changes the future."
Anyone who insists on living in the past is wasting time. Literally and figuratively.
And anyone who spends their time thinking about impossible ways to kill babies is a waste of space.
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