Why is the Great Red Spot on Jupiter so persistent?

 I would be cautious about calling the Great Red Spot permanent. It is certainly long-lived, as it has been observed by astronomers for 348 years. Recent observations show that it is smaller than previously thought. It is quite possible that it will disappear one day.

The short answer is that we don't have a definitive answer regarding the exact mechanisms. There is still much research and discussion about the precise mechanisms of the Great Red Spot and other anticyclones on Jupiter. Much of the current thinking is based on two different models—the quasi-geostrophic (QG) and the mid-geostrophic (IG). It's possible that the only way to resolve the difference between these two models will be to send probes into the atmosphere to obtain direct data.

But we have a fairly good consensus on some of the contributing variables.

The Great Red Spot is as tall as Earth and almost three times as wide. At its narrowest point, it is still six times the diameter of the largest hurricane ever recorded on Earth. The first question we should ask ourselves is why hurricanes on Earth don't last very long. Hurricanes feed on the energy in the moist air over warm water. Normally, hurricanes live until they either pass over cold water or land. On Jupiter, there is no cold water or land for them to fly over.

We should then ask ourselves what else is different about Jupiter that would affect the longevity of a hurricane. There are no boundary layers within the thin weather layer of Jupiter's atmosphere, which means there is very little dissipation. Jupiter rotates very quickly (resulting in a large Coriolis force). There is strong east-west shear. And the atmosphere is so thick that there is a virtually unlimited reservoir of energy.

There is broad agreement that a vortex can become stable if it is fed by shear in the bands above and below it. Computer models reflect this and explain why anticyclones like the Great Red Spot on Jupiter last so much longer than cyclones.

What is the weirdest red carpet dress a Bollywood actress has worn?

 The most beautiful and glamorous Bollywood actresses occasional find themselves on the worst dressed lists. There are some misses every fashionesta makes because it's the nature of the game. They take the resultant criticism from the fashion police in their stride.

These red carpet appearences made me growl!

Clockwise from the left corner:

Priyanka Chopra's weird Camp look at the New York Met Gala, in theme but not pretty at all. This esemblage actually made it to a few best dressed lists on the fashion circuit, but I've personally gone grrrrrrr at the sight of it.

Katrina Kaif's red nightmare on the green carpet at IIFA, an ill fitting full sleeved and square shouldered maxi with a slit in the front. Is this supposed to be androgynous? Then it clashes horribly with her feminine looks. Bad dress!

Kareena Kapoor's weird and garish assemblage in royal blue, and the bad angle doesn't help. The top is okay but the skirt could be in a more subtle neutral colour, this is just too much. No!

Deepika Padukone's ridiculous dress mess. Parrot green pants and a loose off the shoulder top with a huge, ruffled attached cape in the same awful colour. Wish I could appreciate the creativity, but it's just too bad!

Kangana Ranaut's matador look at Cannes was appreciated by some critics but I don't like it. The lower half of the coat front is a mess with that buckram looking weird. And the slicked back hair isn't suiting her either.

Aishwarya Rai's metallic gold dress with that cape consisting of sheets of gold is just too much gold for one dress. It's giving her a clumsy look. And Ash, being famously preoccupied with her appearance, probably knows it and is not feeling happy about it.