Regardless of how fast or slow you reversed the direction. Pretty much every weather pattern and ocean current on the surface of the planet would be thrown into a massive calamity. The Corolis effect and momentum imparted to surface fluids around our rotating ball is a huge, huge deal with weather flow, like the "jet stream". It directs how storm systems (the flow of water that all life depends on) form and track and which typical track they take as the rotation of the earth is constantly deflecting them. There would be huge, unending storm systems as existing patterns now crashed head on into new ones, with storm fronts spanning entire continents. Even after the storms subsided and it settled into a new normal after 20, 30, maybe 50 years... agricultural breadbaskets would be either destroyed, completely inhospitable to their original crops, or stranded in drought. And human civilization would likely fall with them.

Lois Lane would be resurrected and unburied by rocks if there had been an earthquake caused by a nuclear strike shortly before this happened.

We all die, a lot us rapidly when the water keeps moving across the rock that just stopped and super tsunamis a good portion of the planet. The rest of us die slowly as the weather patterns are ruined for likely decades or centuries and we starve due to crop failures and the fact that the worldwide logistics we depend on is forever gone.

Edit: actually I thought some more, if it’s sudden then we’re all crushed by flying into the air into stuff at 1000 miles an hour when the rotation stops. If it’s gradual then we all starve since the weather is ruined

Randall Munroe made an xkcd about this. It's not on his website unfortunately, but someone else uploaded it. I would recommend using a adblocker though.

Lois Lane would come back to life

Time goes backwards and I get to eat that cake I had last week?

It changes the way stars appear to move for us. Astrology teachings would have to do a full 360 degree turn to retain their accuracy.

I can’t say this with any authority, but I think the biggest effect would be in weather patterns and the subsequent downstream effects of having different weather.

Sundials will be useless

The earth's magnetic field would probably 'follow' and change it's direction. But only a while later and very slowly. During the change, that would leave us without a magnetic field for some time. Then we have lots of cosmic rays hitting us, damaging some of the life on eath.

I don’t really know but based on the answers here this is the disaster movie I need next

Only a change in rotational speed would be bad. If earth were to rotate in the opposite direction since the beginning it would behave just like today.

Need more info. Does the earth immediately stop spinning and start spinning in the opposite direction? Or does it gradually stop over an arbitrary amount of time and reverse directions? Haven't seen the episode....

It spins the other way.

yna eb t'now erehT

Everybody would fall over.

Nothing. Only have to swap N-S poles and East becomes West. 💈 🧭

If it happened suddenly, there would be massive tidal waves on western coasts.

The sun would rise in the west and set in the east. Timezones would be backward. People in different areas would have oddly desynchronized sunlight exposure relative to the time on their clocks. For example, if this happened at sunset for you, the sun would rise first from the east and set in the west, then rise again from the west and set in the east. You'd be halfway through a double day at the moment of switching. Other people would have a double night.

Nothing if it does a flip first.

Would somebody smarter than me take these seeds of an idea and expand on how the physical forces would affect the composition of the Earth? My intuition tells me the shear forces would obliterate the planet, but I'm not sure.

Because of the nature of a sphere, the material rotating at the poles is effectively not moving at all. Whereas the material moving at the equator is moving at the maximum rotational speed of the Earth.

Likewise the core of the Earth is effectively still and the speed of each strata moves correspondingly faster as you get closer to the surface.