why do the boats have to be lifted up and down on the panama canal?

Answer 1

The Atlantic and Pacific Oceans are different elevations. At least I believe that to be the case.

Answer 2

the poster without a name has it right....there's a set of mountains in the middle of Panama and the first effort to dig a canal ( by the French, who had dug the Suez) failed because they tried to dig straight thru. The Americans damned the Charges River in the middle of Panama, creating a huge inland lake called Gatun about 200 feet above sea level; one set of locks raises ships to the Lake; they sail some 40 miles across it to another set of locks that lower them down to the ocean.

Gatun Lake is filled by rainfal...and it's worked well since 1914.....so all you need to raise a 75,000 ton ship some 200 feet is rainfall and gravity, as the water flows out of the Lake and fills the locks........as long as someone keeps the locks in repair, the engine / machine that is Panama should last a thousand years.

and sea level is sea level; the difference is the Caribbean side has a 1 foot tide and the Pacific a twenty foot tide

Answer 3

Because the land in the middle is higher than sea level; hence the ships have to be raised to get "over the hump", and then lowered again to ocean level.

It would have been far to expensive to cut down the "hump" to make a level canal.