Why are underwater explosions more deadly than explosions on the surface?

 Imagine you’re relaxing in a swimming pool and suddenly a military grenade drops into the water.

If you think that because water is much denser than air, the shrapnel won’t travel far and you’ll be fine — you’d be right, but not completely.

While the fragments won’t go very far, an underwater explosion has other, much more lethal effects.

Explosives burn extremely fast, so when a grenade detonates, it releases a super-heated gas wave that spreads at incredible speed.
This expanding wave is called a pressure wave — and if it moves fast enough, it can break the sound barrier, creating a shockwave.

On land, a grenade explosion has enough power to tear off limbs, burn flesh, and of course send fragments flying at high speed.
When these shockwaves travel through air and hit a human body, most of the energy is reflected due to the large difference in density.

Only a small portion reaches inside the body, compressing the pockets of gas in your organs — potentially damaging the lungs, ears, blood vessels, and intestines. This internal implosion can cause irreversible injuries.

On the surface, the explosion expands into the atmosphere, which compresses it and reduces its destructive reach.

However, water is considered incompressible — technically it can be compressed, but it requires massive amounts of force to compress even a tiny amount.

This means the surrounding water does not absorb pressure waves as well as air does.

When the pressure wave hits your body underwater, it only slows down slightly because water and the human body have very similar densities — so there is little resistance.

As the wave travels into your body, it instantly compresses the air pockets inside you, causing:

• Brain hemorrhages
• Internal tearing
• Ruptured lungs

If the wave hits the surface and bounces back, the damage becomes even worse due to reflected shockwaves.

So if you ever had to choose between being on the surface or underwater during an explosion…

Your best chance is to run as fast as you can and hope for the best — because underwater, the shockwave is far more deadly.

What would it be like to fall into the surface of Saturn?

 What would it be like to fall into the surface of Saturn?

Saturn has a very low density and its gravity is not that much different than Earth’s, so I imagine you would initially free fall similar to how you would on Earth. The Saturnian atmosphere is closer to pure hydrogen/helium than other planet so your early visibility would be pretty good.

The drawback is you would not have a lot of sunlight to work with, so hopefully your excellent space suit would have powerful headlights.

When you started your descent the temperature may be as low as -250 C, but as you zip through the clear air to the first cloud layer the temperature climbs to -130 C. You are not falling that fast, your terminal velocity is around 200 km/h and will gradually slow as you reach thicker and thicker air, but so far you have fallen about 100 km and start passing through your first light cloud layer of ammonia crystals.

Saturn is a very windy place with the equatorial wind reaching speeds of 1,800 km/h, slowing somewhat towards the poles, but either way you are getting some lateral buffeting.

By the time you’ve passed through the second cloud layer of ammonia, hydrosulfides and ice crystals, the temperature is getting warmer, in the -70 C range and you have fallen for 170 km.

Another 130 km further and it seems more Earth-like, zero C or more and clouds of water, some of it liquid so you flip on your windshield wipers.

You have now fallen close to 400 km, and it’s taken over 2 hours, temperatures are climbing from freezing to as much as 80 C. Pressure is increasing rapidly now and you are seeing more and more liquid compounds, an hour or 2 more and the hydrogen is beginning to liquefy under the pressure. Helium is becoming more of the mix and temperatures continue to rise. Friction and static electricity generate lightning that arcs in from the troposphere.

As the liquid hydrogen thickens you continue to slow your descent until you have to fire up your propulsion system to proceed further. Eventually you see pressure liquefied helium as well and then a new barrier - metallic hydrogen which is much denser than water and crackles with magnetic fields it generates.

Other than increasing heat (up to 11,700 C) and pressure (>1000 bars) in this sea of metallic hydrogen you have a long way to descend until you finally reach a rocky core of compressed heavier elements like carbon, oxygen, silicon, and iron in a sphere possibly twice the diameter of the Earth.

Now the hard part….how in the hell are you going to get back out ?