You may be surprised to know that tides also played a key role in the World War II D-Day invasion. German leaders suspected an American invasion long before it happened. They knew it would be an invasion by sea, and they even suspected that the invasion would come during high tide. At Normandy, when the tides were low, German commanders caused millions of obstacles to be erected in the sand in preparation for the Allied attack. They stood at the ready to beat back the American surge.
Why would German commanders have anticipated an American invasion at high tide as opposed to low tide? Why would they have built all the obstacles?
Don't know? Read the whole fascinating tale at http://dx.doi.org/10.1063/PT.3.1257 .
BONUS:
A FULL SIZED CANDY BAR OR SIMILARLY-PRICED TREAT OF CHOICE WILL BE AWARDED TO THE FIRST PERSON TO POST A COMMENT EXPLAINING, ACCORDING TO THE ARTICLE, HOW GRAVITY AND THE CENTRIFUGAL FORCE INTERACT TO CAUSE HIGH AND LOW TIDES.
German commanders anticipated an American invasion at high tide because it would make the distance of the beach much shorter, thus making it easier for Allied troops to get out of the line of fire quicker. The Germans built the obstacles to prevent Allied landing craft from being able to reach the beach. At high tide the obstacles would be completely submerged but large enough so that the bottoms of the landing craft would hit the obstacles and heavily damage the craft.
ReplyDeleteI understand how the moon's gravitational force pulls the water closer to itself causing high tide and vice versa. However, I'm not sure how centrifugal force works. Could you please explain? (In general, not just in this example)
Excellent logic Chris. You are exactly right as to why the Germans were expecting an attack at high tide.
ReplyDeleteInterestingly enough, the Americans ended up actually attacking just an hour after low tide. American intelligence found out about all the obstacles and they didn't want to bust up all their transport ships so they reluctantly settled for a low tide attack. That made for lot more beach to cover! It is amazing that they were successful in their effort.
Lets wait for a few more people to take a crack at answering the question of how gravitational and centrifugal forces interact to cause tides. I'll give you a hint: It is in the "Understanding Tides" section of the article I've referenced in this blog post.
German commanders anticipated an American invasion on high tide due to the fact that the level of the water is higher, so in theory the allies would have less distance to travel on the beach. This is why the german commanders set up obstacles to stop there landing craft from reaching the beach, making it difficult for allied troops. The gravitional pull between the moon and the earth, along with the rotation (centrifugal force ) along the moon around the earth, causes the water to rise during high tide.
ReplyDeleteNice job Heriberto. Pretty good explanation of tides, but I'm looking for more detail. The article I referenced in the blog post ( http://dx.doi.org/10.1063/PT.3.1257 ) has a really detailed and good explanation about exactly how the two forces work together to cause a certain type of tide (high or low).
ReplyDeleteI would encourage you to go read the short section on "Understanding Tides" in that article.
German commanders anticipated the American invasion to occur at high tide because during the high tide, the Americans would land closer to the German forces and wouldn't have such a large beach front to cover. With the low tide, the Americans would be exposed and unprotected. So it's easy to see why the German commanders would assume the Americans to invade during the high tide. And the Germans' counterattack of underwater obstacles positioned to snag and rip out the bottoms of the landing craft was a wise counterattack indeed, but only if the Americans had in fact made land fall during the high tide. They had built the obstacles, again assuming the Americans would attack during high tide, in hopes to overturn and snag American landing craft, throwing a wrench into their invasion.
ReplyDeleteThe gravitational on the moon by the earth is what causes high and low tides. In other words, as the moon rotates around the earth, it pulls the water away from the earth, creating high tides. On the same hand, while the side of the earth closest to the moon will be at high tide due to the moon's gravitational pull, naturally the 'sides' of the earth or the sides farther away from the moon will be at low tide, again because the majority of the water is being pulled together and up with the moon's gravitational pull. Though this is where I begin to become confused. I understand that this all creates a total of two high and two low tides around the earth, though I don't understand how the second high tide, the one formed on the backside, farthest from the moon is formed. What is centrifugal repulsion and how does it create a force strong enough to create a high tide like the moon can?
~Rebekah Clayton
I think that Chris and Rebekah are right, high tied will hide the obstacles and stop the Americans from invading. The Americans of course would come during hide tide because the water is closer to land than during low tide.
ReplyDelete-Semira Jusic
The German commanders would have expected a high tide attack by the Americans as it would have significantly decreased the amount of beach to cover. Thus they(the Germans) placed the obstacles in hope of destroying ships and drowning as many troops as possible
ReplyDeleteThe Germans predicted an invasion at high tide because it would give them more of an advantage to get further up the beach and by getting further up the beach means less distance to travel and get shot at. The Germans set up the obstacles at low tide so it would be harder for the landing craft vehicle's (LCV) to see them at high tide.
ReplyDeleteThe Germans anticipated an invasion at high tide because they too tried to do a similar thing in their operation Sea Lion. Invading at high tide means the troops being unloaded have a shorter distance to advance along the beach before they reach enemy bunkers and soldiers, so it would make the most strategic sense to do so. However, the Germans, anticipating such a maneuver, built many obstacles on the beach to hinder the progress of the Allied invasion. Building obstacles during periods of low tide allowed them to build more obstacles and cover a larger area so that when the tide came in, it would hide all their Nazi traps and weaken the Allied forces. It didn't work.
ReplyDeleteRebekah, great job thinking through the logistics of the D-day attack. You are exactly right about why the Allies wanted to attack at high tide. I am also impressed with your understanding of tides.
ReplyDeleteThe easiest way I can explain the centrifugal force is to ask you to imagine driving in your car and then making a turn around a sharp curve. You'll notice that your body tends to want to follow the straight path you were on before you came to the curve. But your seatbelt and the seat of your car act on you and force your body to curve with the motion of the car. That is the essence of the centrifugal force. It works hand in hand with gravity.
I encourage you to follow this link (http://dx.doi.org/10.1063/PT.3.1257) and read this short but very instructive paragraph on understanding tides and how gravity and the centrifugal force interact to create two high tides, one on each side of the earth.